1. MILK COOLING SYSTEMS ON DAIRY FARMS
TO DETERMINE THE MOST ENERGY EFFICIENT METHOD
OF COOLING MILK IN BOTH CONVENTIONAL AND
AUTOMATIC MILKING SYSTEMS
BY
DAVID CONNOLLY
Dissertation submitted to
the School of Engineering
Waterford Institute of Technology
In partial fulfilment of the requirement for
the Degree of Bachelor of Engineering (Honours)
in Sustainable Energy Engineering
March 2016

2. i
Declaration
I declare that this dissertation, in whole or in part, has not been submitted to any
University/Institute as an exercise for a degree. I further declare that, except where
reference has been made in the text, the contents are entirely my own work. The author
agrees that the library may lend or copy this dissertation upon request for study
purposes, subject to the normal conditions of acknowledgement.
Signature: __________________________________________
Date: __________________________________________

3. ii
Table of Contents
Declaration.........................................................................................................................i
List of Tables....................................................................................................................vi
List of Figures .................................................................................................................vii
List of Equations ............................................................................................................viii
List of Abbreviations........................................................................................................ix
Executive Summary ..........................................................................................................x
Acknowledgements..........................................................................................................xi
Chapter 1 - Introduction....................................................................................................1
1.1 Research Overview .................................................................................................1
1.2 Research Aim..........................................................................................................1
1.3 Objectives................................................................................................................1
1.4 Hypothesis...............................................................................................................2
1.5 Justification of Research .........................................................................................2
Chapter 2 - Literature Review...........................................................................................3
2.1 Chapter Overview ...................................................................................................3
2.2 Importance of Milk Cooling....................................................................................4
2.2.1 Milk Spoilage...................................................................................................4
2.2.2 Price Adjustments ............................................................................................4
2.3 Methods of Cooling Milk........................................................................................5
2.3.1 Pre-cooling Unit...............................................................................................5
2.3.2 Refrigeration Unit ............................................................................................9
2.4 Vapour-compression refrigeration cycle...............................................................11
2.4.1 Pressure-Enthalpy Diagram ...........................................................................12
2.5 Concept of Heat Transfer......................................................................................13
2.5.1 Convective heat transfer.................................................................................13
2.6 Existing Research Findings...................................................................................19
2.7 Chapter Summary..................................................................................................20
Chapter 3 - Research Methodology ................................................................................21
3.1 Chapter Overview .................................................................................................21
3.2 Review of Objectives............................................................................................21
3.3 Hypothesis.............................................................................................................21
3.4 Choice of Research Methodology.........................................................................22
3.5 Research Limitations.............................................................................................22
3.6 Chapter Summary..................................................................................................22

4. iii
Chapter 4 - Monitoring / Methods of Data Capture........................................................23
4.1 Chapter Overview .................................................................................................23
4.2 Monitoring Period.................................................................................................23
4.3 Parameters Recorded.............................................................................................23
4.3.1 Power consumption........................................................................................23
4.3.2 Fluid temperatures..........................................................................................23
4.3.3 Volume of water required ..............................................................................24
4.3.4 Volume of milk cooled...................................................................................24
4.4 Equipment Used....................................................................................................24
4.4.1 Electricity Meters...........................................................................................24
4.4.2 Temperature Loggers .....................................................................................26
4.5 Electricity Tariff....................................................................................................27
4.6 Chapter Summary..................................................................................................28
Chapter 5 - Case Study....................................................................................................29
5.1 Chapter Overview .................................................................................................29
5.2 Description of Case Studies ..................................................................................29
5.2.1 Farm A ...........................................................................................................29
5.2.2 Farm B............................................................................................................29
5.2.3 Farm C............................................................................................................29
5.2.4 Farm D ...........................................................................................................30
5.2.5 Farm E............................................................................................................30
5.3 Chapter Summary..................................................................................................30
Chapter 6 - Research Findings........................................................................................31
6.1 Chapter Overview .................................................................................................31
6.2 Farm A ..................................................................................................................31
6.2.1 Parameter 1 – Volume of milk cooled ...........................................................31
6.2.2 Parameter 2 – Milk & water temperatures associated with THE...................31
6.2.3 Parameter 3 – Volume of GW required by THE............................................34
6.2.4 Parameter 4 – Power consumption of refrigeration unit ................................34
6.2.5 Parameter 5 – Power consumption of GW pump...........................................35
6.2.6 Summary of Findings.....................................................................................38
6.3 Farm B...................................................................................................................39
6.3.1 Parameter 1 – Volume of milk cooled ...........................................................39
6.3.2 Parameter 2 – Milk temperature upon entering refrigeration unit .................39

5. iv
6.3.3 Parameter 3 – Power consumption of refrigeration unit ................................40
6.3.4 Summary of Findings.....................................................................................41
6.4 Farm C...................................................................................................................42
6.4.1 Parameter 1 – Volume of milk cooled ...........................................................42
6.4.2 Parameter 2 – Milk temperature upon entering refrigeration unit .................42
6.4.3 Parameter 3 – Power consumption of refrigeration unit................................43
6.4.4 Summary of Findings.....................................................................................44
6.5 Farm D ..................................................................................................................45
6.5.1 Parameter 1 – Volume of milk cooled ...........................................................45
6.5.2 Parameter 2 – Milk & water temperatures associated with PHE...................45
6.5.3 Parameter 3 – Volume of GW required by PHE............................................46
6.5.4 Parameter 4 – Power consumption of refrigeration unit ................................48
6.5.5 Parameter 5 – Power consumption of GW pump...........................................49
6.5.6 Summary of Findings.....................................................................................51
6.6 Farm E...................................................................................................................52
6.6.1 Parameter 1 – Volume of milk cooled ...........................................................52
6.6.2 Parameter 2 – Milk & water temperatures associated with PHE 01..............52
6.6.3 Parameter 3 – Volume of GW required by PHE 01.......................................54
6.6.4 Parameter 4 – Milk & water temperature associated with PHE 02................55
6.6.5 Parameter 5 – Power consumption of IB supplying CW to PHE 02 .............56
6.6.6 Parameter 6 – CW temperatures between IB & refrigeration unit.................58
6.6.7 Parameter 7 – Power consumption of refrigeration process ..........................58
6.6.8 Parameter 8 – Power consumption of GW pump...........................................59
6.6.9 Summary of Findings.....................................................................................62
Chapter 7 - Discussion ....................................................................................................63
7.1 Chapter Overview .................................................................................................63
7.2 Energy Performance..............................................................................................63
7.2.1 AMS...............................................................................................................63
7.2.2 CMS ...............................................................................................................71
7.2.3 AMS vs. CMS................................................................................................75
7.3 Financial Appraisal ...............................................................................................77
7.3.1 AMS...............................................................................................................77
7.3.2 CMS ...............................................................................................................80
7.3.3 AMS vs. CMS................................................................................................83

6. v
7.4 Unexpected Findings.............................................................................................85
Chapter 8 – Conclusions & Recommendations ..............................................................86
8.1 Chapter Overview .................................................................................................86
8.2 Testing of Hypothesis ...........................................................................................86
8.3 Conclusions...........................................................................................................86
8.3.1 Research objective 1 ......................................................................................86
8.3.2 Research objective 2 ......................................................................................87
8.3.3 Research objective 3 ......................................................................................87
8.3.4 Research objective 4 ......................................................................................87
8.3.5 Research objective 5 ......................................................................................87
8.4 Recommendations for Further Research...............................................................88
8.5 Closing Statement .................................................................................................88
Bibliography....................................................................................................................89
Appendices......................................................................................................................98
Appendix A – Lely Documents ..................................................................................99
Appendix B – Milking times for Farm A..................................................................100
Appendix C – Milk yield during GW measuring period for Farm A........................104
Appendix D – Milking times for Farm B..................................................................106
Appendix E – Average milk temperature for Farm C...............................................110
Appendix F – Average milk temperature for Farm D...............................................112
Appendix G – GW flow rate recordings for Farm D ................................................114
Appendix H – Milking hours for Farm D .................................................................116
Appendix I – Average milk temperatures for Farm E...............................................118
Appendix J – GW flow rate recordings for Farm E..................................................120
Appendix K – Milking hours for Farm E..................................................................122
Appendix L – CW temperatures for IB supplying PHE 02 for Farm E....................124
Appendix M – CW temperatures for IB supplying refrigeration unit for Farm E ....126
Appendix N – Schematics of each system ................................................................128
Appendix O – OWL Software User Guide ...............................................................134

7. vi
List of Tables
Table 1: Using the Re Number to determine type of flow...............................................17
Table 2: Desired PHE outlet temperatures (Source: Ryan, 2004) .................................19
Table 3: Different Day/Night Rates (Source: Electric Ireland, 2015; SEE Airtricity,
2015; & Bord Gais Energy, 2015)..................................................................................28
Table 4: Farm D - Milking hours....................................................................................47
Table 5: Farm E - Milking hours....................................................................................54
Table 6: Determining the type of flow ............................................................................65
Table 7: Detailed review of GW pump for AMS .............................................................69
Table 8: Impact of a pre-cooler in an AMS ....................................................................70
Table 9: Water flow rates for Farms D & E...................................................................71
Table 10: Calculated water-to-milk ratios......................................................................72
Table 11: Impact of different cooling systems in a CMS ................................................74
Table 12: AMS vs CMS - Absence of pre-cooling...........................................................75
Table 13: AMS vs CMS - Annual cooling demands without pre-cooling .......................76
Table 14: AMS vs CMS - Presence of pre-cooling .........................................................76
Table 15: Annual cooling demands with pre-cooling.....................................................77
Table 16: Farm A & B - Day/night units ........................................................................77
Table 17: Farm A & B – Refrigeration unit costs per cycle ...........................................78
Table 18: AMS - Day/night units for GW pump..............................................................78
Table 19: AMS - Cost to operate GW pump ...................................................................79
Table 20: AMS - Total cooling costs...............................................................................79
Table 21: Farms C, D & E - Day/night units..................................................................80
Table 22: Farms C, D & E - Refrigeration unit costs per cycle .....................................80
Table 23: Farms C, D & E - No. of minutes on night rate .............................................81
Table 24: CMS - Costs to operate GW pump..................................................................82
Table 25: CMS - Total cooling costs ..............................................................................82
Table 26: AMS vs. CMS - Annual cooling costs without pre-cooling.............................83
Table 27: AMS vs. CMS - Annual cooling costs of refrigeration unit with pre-cooling.83
Table 28: AMS vs. CMS - Annual GW pumping costs....................................................84
Table 29: AMS vs. CMS - Total annual cooling costs ....................................................84

8. vii
List of Figures
Figure 1: Energy use breakdown on dairy farms (Source: Upton, 2012) ........................2
Figure 2: Flow principle of a single stage PHE (Source: DeLaval, 2000) ......................6
Figure 3: Flow principle of a double stage PHE (Source: DeLaval, 2000).....................7
Figure 4: Internal structure of an IB (Source: Kilkenny Cooling Systems, 2015) ...........7
Figure 5: Possible flow principles for a THE (Source: PicoTech, 2014).........................8
Figure 6: Internal structure of a typical refrigeration unit (Source: DeLaval, 2015) .....9
Figure 7: Basic vapour compression cycle (Source: O'Keefe, 2007).............................11
Figure 8: Rate of heat transfer under parallel flow (Source: Moss, 1998) ....................14
Figure 9: Rate of heat transfer under counter-flow (Source: Moss, 1998) ....................15
Figure 10: Types of flow .................................................................................................17
Figure 11: The OWL transmitter, CT clamp & display monitor (Source: The Owl, 2016)
.........................................................................................................................................25
Figure 12: Various ways of analysing logged data on the software (Source: The Owl,
2016) ...............................................................................................................................25
Figure 13: Various temperature loggers used (Source: TESTO, 2015).........................26
Figure 14: Farm A - Associated milk temperatures........................................................32
Figure 15: Farm A - Associated water temperatures during cycle ................................33
Figure 16: Farm A - Associated water temperature before & during cycle...................34
Figure 17: Farm A - Power consumption profile during cycle ......................................35
Figure 18: Farm B - Associated milk temperatures........................................................39
Figure 19: Farm B - Power consumption profile during cycle ......................................40
Figure 20: Farm C - Associated milk temperatures .......................................................42
Figure 21: Farm C - Power consumption profile during cycle ......................................43
Figure 22: Farm D - Associated milk temperatures.......................................................45
Figure 23: Farm D - Associated water temperatures.....................................................46
Figure 24: Farm D - Power consumption profile during cycle......................................48
Figure 25: Farm E - Associated milk temperatures for first PHE..................................53
Figure 26: Farm E - Associated water temperatures with first PHE .............................53
Figure 27: Farm E - Associated milk temperatures with second PHE...........................55
Figure 28: Farm E - Associated water temperatures with second PHE ........................56
Figure 29: Farm E - Power consumption profile IB feeding PHE during the cycle ......57
Figure 30: Associated flow & return temperatures for the IB feeding the refrigeration
unit ..................................................................................................................................58

9. viii
Figure 31: Farm E - Power consumption profile of IB feeding refrigeration unit during
cycle.................................................................................................................................59
Figure 32: Presence of THE vs Absence of THE on power consumption profile...........69
Figure 33: Most efficient water-to-milk ratio.................................................................71
Figure 34: Power consumption profiles of Farms C, D & E..........................................73
List of Equations
Equation 1: Basic heat transfer equation .......................................................................15
Equation 2: Formulae for calculating dimensionless numbers ......................................16
Equation 3: Equations used to determine type of flow ...................................................17
Equation 4: Log mean temperature difference (Source: Moss, 1998)............................18
Equation 5: Basic equation to convert Power to Energy................................................23
Equation 6: Conversion of Raw Data.............................................................................26
Equation 7: Volume of milk pipe.....................................................................................64

10. ix
List of Abbreviations
AMS – Automatic Milking System
CMS – Conventional Milking System
CW – Chilled Water
DX – Direct Expansion
GIIL – Glanbia Ingredients Ireland Ltd.
GW – Ground Water
HE – Heat Exchanger
IB – Ice Bank
IEA – International Energy Agency
IFA – Irish Farmers Journal
LMTD – Log Mean Temperature Difference
PHE – Plate Heat Exchanger
SHC – Specific Heat Capacity
TBC – Total Bacterial Count
THE – Tubular Heat Exchanger

11. x
Executive Summary
Title: Milk Cooling Systems on Dairy Farms
Sub-title: To determine the most energy efficient method of cooling milk in
both Conventional and Automatic Milking Systems
Researcher: David Connolly
Supervisor: Colm Tynan
Submission Date: 4th
of March 2016
Purpose:
This dissertation was inspired by the author’s admiration for dairy farming. Growing up
on the family farm exposed the author to the financial struggles farmers face whenever
there’s a drop in milk price or an increase in energy cost. By identifying the largest
energy user on a dairy farm as milk cooling, the author proceeds to compare the
available methods for each system in terms of energy performance. From the findings
and recommendations of this research, the author hopes to help dairy farmers become
more aware about the energy efficiency of their cooling system.
Methodology:
A comprehensive literature review was undertaken which revealed the various types of
cooling systems for both an AMS and a CMS. A total of five case studies were set up
which resembled the different cooling systems as closely as possible. Parameters such
as electricity consumption and temperatures were recorded on each farm. This allowed
the author to determine the energy consumed per litre of milk produced.
Findings:
For an AMS this research concludes that the presence of precooling can reduce the
energy consumption by 52% per litre of milk cooled compare to the absence of
precooling. While for a CMS, the most efficient method for cooling milk is through the
use of a double stage pre-cooler, IBs and an indirect expansion bulk tank. Single stage
pre-cooling resulted in being the least efficient method, however, the difference
between an automatic and manual wash may have offset this unexpected outcome.

12. xi
Acknowledgements
The author would like to express his sincere gratitude to the various people involved
throughout this research process for their help and support.
Firstly, I would like to thank my supervisor, Colm Tynan, for his assistance, guidance
and patience for the entirety of the investigation.
Secondly, I would like to give a special thanks to all of the dairy farmers who took part
in this research. Without them, this investigation would not have been possible.
Thirdly, I would like to thank the following professionals who provided their assistance
and invaluable knowledge throughout:
Larry Banville – Lely
Jim Brook – Lely
John Upton – Teagasc
Finally, to my classmates, friends and family, I thank you for your support, patience and
motivation for the duration of this research process. Without these attributes, this study
would never have been fulfilled to its full potential.

13. xii
Word count: 16,569

14. 1
Chapter 1 - Introduction
1.1 Research Overview
The process of cooling milk has been one of the highest energy users on dairy farms for
many years with reports stating that it can account for up to 40 per cent of the farms
electricity costs (Daly, 2011). Milk leaves the udder at approximately 35°C and must be
cooled to a storage temperature of 4°C within two hours in order to maintain maximum
quality and minimise micro-organism growth. Failure to do so will result in a high total
bacterial count (TBC) which leads to the farmer facing price adjustments per litre of
milk produced (FarmFile, 2015).
Towards the end of June 2015 Simon Coveney, the Minister for Agriculture, invited
Ireland’s 17,000 dairy farmers to apply for the 40% grant-aid for modernising their
dairy farms. Such upgrades include milking machines, milk cooling and storage
equipment, water heating and feeding systems (English, 2015). This presented an
opportunity for dairy farmers to increase their cooling systems in terms of energy
efficiency. The presence of a pre-cooling unit in a milk cooling system has the potential
to reduce cooling costs by up to 50% (Daly, 2011).
1.2 Research Aim
The aim of this research was to compare various milk cooling systems and determine
the most energy efficient for both conventional and automatic milking systems on dairy
farms in Ireland.
1.3 Objectives
In order to accomplish the aim stated above, the following list of objectives must be
adhered to:
 To review the available literature surrounding milk cooling on dairy farms.
 To investigate the various methods of cooling milk in both automatic and
conventional milking systems.
 To monitor each milk cooling system in terms of energy performance.
 To analyse and compare each method in order to determine the most energy
efficient.
 To provide recommendations based on the authors findings and identify
potential areas for further, in-depth research.

15. 2
1.4 Hypothesis
Throughout this research, the following statement shall be tested:
“Pre-cooling is considered an energy efficient solution to reduce milk cooling demands
on Dairy Farms”.
1.5 Justification of Research
The author chose to conduct this particular research in order to provide dairy farmers
with an insight into the energy performance of their cooling systems. As it stands, many
farmers just pay their bills and don’t query the figures involved. Milk cooling is
considered a necessary cost and farmers don’t have the time or the understanding to
seek potential savings. By monitoring each cooling system, the information will provide
farmers with feedback so they know exactly how much their system is costing
compared to other cooling systems. This dissertation will be beneficial to all dairy
farmers, especially those who got involved as it is focused on their exact systems.
Figure 1: Energy use breakdown on dairy farms (Source: Upton, 2012)

16. 3
Chapter 2 - Literature Review
2.1 Chapter Overview
The following review shall focus on the topic of determining the most energy
efficient method of cooling milk for both conventional and automatic milking
systems on dairy farms and provide an extensive review of the available literature.
The main sources of information contained within this review are books, journals
and reliable authorities on the subject; the use of unreliable websites has been
avoided due to the unreliability of their material.
As suggested by Fawkes (2013), interest in energy efficiency has experienced a
significant growth in the last five years due to rising energy prices and environmental
concerns. However, there is still confusion about the term ‘energy efficiency’. The
International Energy Agency (IEA) considers something to be energy efficient ‘if it
delivers more services for the same energy input, or the same services for less energy
input’ (IEA, 2016).
This review inspects the various aspects of milk cooling on dairy farms. It begins by
outlining the importance of cooling milk. Following on from this, the different
cooling methods are discussed with the concept of heat transfer explained for both an
AMS and a CMS cooling system. The review concludes by inspecting and
summarising the findings from case studies performed by reliable authorities on the
subject.

17. 4
2.2 Importance of Milk Cooling
Glanbia Ingredients Ireland Limited (GIIL), the milk processor, carries out tests on
the milk to measure the total bacterial count (TBC). TBC is linked with general
hygiene and milk storage conditions; where the lower the count, the better to
conditions are.
GIIL require dairy farmers to provide a capacity to hold a minimum of five milking’s
during peak collection periods so exceptional milk storage facilities are crucial as
suppliers face price adjustments depending on the TBC (Glanbia Ingredients Ireland
Limited, 2015).
2.2.1 Milk Spoilage
The instance milk is withdrawn from the cow’s udder at 35°C it becomes highly
perishable due to its richness in nutrients, neutrality in pH and lack of protection
from contamination. GIIL reserve the right to refuse any quantity of milk which is
not in accordance with its Milk Purchasing Policy (Glanbia Ingredients Ireland
Limited, 2015). As explained by Trott (1989), the cooling of milk to below 4°C
within two hours will prevent any micro-organisms present from multiplying at a
dangerous rate and preserve milk for transportation. Both Cengel & Boles (1998)
suggest that for every 3°C rise in temperature, the growth rate of some micro-
organisms doubles.
2.2.2 Price Adjustments
Depending on the milk quality, GIIL can adjust the price per litre paid to the dairy
farmer. With many dairy farmers relying on the production of milk as the sole source
of income, milk quality is of paramount importance. Surveys recently conducted by
Teagasc, the Agriculture and Food Development Authority, on dairy farms reveal
that it costs 25 cent to produce one litre of milk in the Republic of Ireland. This
figure, however, doesn’t take into consideration the EU support payments (Halleron,
2015).

18. 5
2.3 Methods of Cooling Milk
The energy required for milk cooling primarily depends of two factors; the efficiency
of the refrigeration unit and the temperature differential of the milk. The most
common method of cooling milk is to employ a two stage process consisting of a
pre-cooling unit and a refrigeration unit (Upton, et al., 2013). The cooling system for
a CMS differs slightly to that of an AMS with the two main differences being the
milk flow rate per unit time and the pre-cooler requirements. According to the Irish
Farmers’ Association (IFA), the average dairy herd size is approximately sixty cows
with each cow having an average annual yield of five thousand litres. To put this into
perspective, this results in three hundred thousand litres of milk which must be
cooled below 4°C in order to achieve the best price per litre from GIIL. (Irish
Farmers' Association, 2014).
2.3.1 Pre-cooling Unit
The easiest and most cost effective way of cooling milk is to install a pre-cooler. Pre-
cooling units are fitted between the storage jar and the refrigeration unit with a
purpose of reducing the cooling load of the refrigeration unit (Dillion, et al., 2010).
Pre-cooling is achieved by pumping hot milk through a heat exchanger where ground
water (GW) is pumped through the opposite side. An efficient pre-cooler should
reduce the milk temperature by approximately 20°C (Hartley & Kennard, 2015).
2.3.1.1 CMS Pre-cooler
In a CMS, the herd is usually milked twice a day, both morning and evening. This
requires the pre-cooler to have the ability to cool a large volume of milk in a short
period of time. By taking the average dairy herd size into consideration, just over
four hundred litres of milk will pass through the pre-cooler per milking. The plate
heat exchanger (PHE) is the most common type of pre-cooling method used in a
CMS and is available as a single stage or double stage set up (Ryan, 2004). The PHE
consists of thin rectangular stainless steel plates, containing stamped channels
through which fluid flows, with large surface area for efficient heat transfer
(Branson, 2011).

19. 6
2.3.1.1.1 Single Stage Pre-cooler
Ryan (2004) also explains that a single stage pre-cooler operates by passing milk and
cool GW, at a ratio of one part milk to two parts GW for optimum efficiency, in
opposite directions. The majority of farms have access to naturally cooled GW which
is freely available and more commonly used as the only cost involved is that of the
pump. The tepid water exiting the heat exchanger can be used for multiple tasks such
as udder washing, yard washing and for stock. According to Lely (2011), stock water
should be within 10-20°C for optimal consumption during the cold winter days so
tepid stock water proves very beneficial. Daly (2011) claims that a ‘a correctly sized
and properly functioning plate cooler can reduce the milk temperature to within 2-
3°C of the well water temperature, more than halving the electricity cost for cooling’
by reducing the load on the refirgeration unit. However, Upton (2012) suggests that
this goal is rarely achieved in practice.
Figure 2: Flow principle of a single stage PHE (Source: DeLaval, 2000)
2.3.1.1.2 Double Stage Pre-cooler
The presence of a double stage pre-cooler provides the ability to instantly cool the
milk to the desired storage temperature of below 4°C. The first stage consists of a
PHE that uses GW as the cooling medium, while the second stage consists of a
second PHE which uses chilled water (CW) as the cooling medium. The CW is
circulated between the second PHE and the evaporator coil in the ice bank (IB) when
milk cooling is required.

20. 7
Figure 3: Flow principle of a double stage PHE (Source: DeLaval, 2000)
Koelet (1992: 176) describes ice banks as ‘evaporator coils or plates submerged in a
tank of water’ where the coils or plates are surrounded by ice. The coils and plates
are placed further apart than normally in order to provide clearance for ice to build
up. Ideally, the ice should last for both milkings the following day, provided the IB is
correctly sized (Ryan, 2004). Liscarroll Engineering (2014) associate additional
benefits such as reduced bacterial growth, advantageous use of “off-peak” electricity
and reduced running costs with the presence of ice builders in milk cooling systems
on dairy farms. IBs are considered an alternative option for milk cooling where a
three phase supply is prohibited as they contain smaller condensers that operate over
large periods of time (DairyMaster, 2012).
Figure 4: Internal structure of an IB (Source: Kilkenny Cooling Systems, 2015)

21. 8
Figure 4 illustrates the circulation pump and the internal coil of an IB. As previously
mentioned, the CW is pumped to the second PHE where it absorbs heat from the
milk only to be circulated through the evaporator coil in the IB to be cooled by the
ice.
2.3.1.2 AMS Pre-cooler
In an AMS, cows are being individually milked throughout the day with the average
cow visiting the robot twice a day. This leads to a significantly smaller volume of
milk that requires cooling at any one time. When compared to a CMS with the same
herd, the AMS never experiences an immediate large cooling demand. As a result of
this, a relatively smaller pre-cooler, in terms of surface area for heat transfer, is
sufficient.
The tubular heat exchanger (THE) is the most common pre-cooling method for an
AMS. A THE consists of a coil with both an inner and outer tube; the inner tube for
milk and the outer tube for water. Both tubes are then encased within a shell and
surrounded with insulation. The volume of water that passes through the THE is
controlled by a solenoid on the water inlet. The solenoid opens each time the milk
pump is activated and aims for the desired ratio of two parts water to one part milk
(Lely, 2015).
Figure 5: Possible flow principles for a THE (Source: PicoTech, 2014)

22. 9
2.3.2 Refrigeration Unit
Refrigeration can be described as the transfer of heat from a hot reservoir (source) to
a cold reservoir (sink) under controlled conditions with the aim of cooling the source.
For milking systems, milk is classed as the heat source while, depending on the
cooling method, water or air can be classed as the heat sink (Perrot, 1998).The
refrigeration unit on dairy farms, more so known as the bulk tank, provides final
cooling of the milk to 4°C within the two hour period and maintains that temperature
until collected by GIIL. As expressed by Cengel & Boles (1998) the ability to
maintain the required storage temperature is critical in ensuring high quality milk as
a small increase in storage temperature will cause a large increase in the growth of
unwanted microorganisms.
The bulk tanks cooling system consists of pipes or pillow plates, through which the
cooling liquid flows, which are located on the underside of the milk chamber. A
layer of insulation covers the milk chamber and the cooling lines, with an exterior
metal shell over the insulation (O'Keefe, 2007). The aforementioned cooling medium
being used depends on the type of cooling system in use; direct expansion (DX) and
indirect expansion.
Figure 6: Internal structure of a typical refrigeration unit (Source: DeLaval, 2015)

23. 10
2.3.2.1 Direct Expansion Cooling
According to Liscarroll Engineering (2014), DX bulk tanks cool milk directly by
circulating refrigerant through the evaporator plates and are the most popular cooling
systems on Irish dairy farms. While DeLaval (2000) state their popularity is a result
of their high efficiency in cooling technology combined with their lowest possible
energy consumption. A DX bulk tank operates on a typical vapour-compression
refrigeration cycle which consists of four essential components; evaporator,
compressor, condenser and an expansion valve (Murphy, et al., 2011). The heat is
absorbed from the milk into the refrigerant and then emitted in the condesning unit
where cool air is pulled across it via a fan.
2.3.2.2 Indirect Expansion Cooling
An indirect expansion bulk tank uses CW as a cooling medium as opposed to a
refrigerant. The CW is circulated between the evaporator plates in the bulk tank and
the evaporator coil in the IB. Compared to a DX bulk tank where the heat is absorbed
and emitted by the refrigerant; the CW absorbs heat from the milk in an indirect
expansion bulk tank. The CW then carries this heat to the IB where the generated ice
absorbs the heat from the CW; hence the name ‘indirect expansion’.

24. 11
2.4 Vapour-compression refrigeration cycle
The vapour-compression refrigeration cycle is the most commonly used in
refrigeration systems due to its high index of efficiency (Moran, et al., 2012). A
schematic of the aforementioned cycle including the four essential components is
illustrated in the following Figure.
Figure 7: Basic vapour compression cycle (Source: O'Keefe, 2007)
The refrigerant enters the compressor as a heated vapour at a low pressure from the
evaporator. The purpose of the compressor is to compress the refrigerant, causing a
rise in temperature, and to keep circulating the refrigerant throughout the system
(Cook, 1995).
The refrigerant enters the condenser as a superheated vapour at an elevated pressure.
The condenser is positioned outside and contains fans which pull cool air across the
coils causing heat to be transferred from the superheated vapour by forced
convection. This process removes the heat and liquefies the vapour causing the
refrigerant to exit the condenser as a liquid at an elevated pressure (Minich &
Elonka, 1983).
The expansion valve controls the flow of refrigerant from the elevated-pressure
condensing side into the low-pressure evaporating side of the system (Trott, 1989).

25. 12
The refrigerant flows through an expansion valve which decreases the pressure of the
liquid and, as a result of pressure drop, some of the liquid flashes into vapour.
The refrigerant then enters the evaporator where it hits saturation point and the
remaining liquid is vaporized as heat is transferred from the refrigerated space. The
refrigerant exits the evaporator as a heated vapour at a low pressure and the entire
cycle repeats itself (Sonntag & Borgnakke, 2009).
2.4.1 Pressure-Enthalpy Diagram
The pressure-enthalpy (p-H) diagram is a very useful way of illustrating the pressure
and energy changes within the vapour-compression refrigeration cycle.
The circuit 1-2-3-4-1 on Figure 7 represents the aforementioned cycle in its simplest
form.
Stage 1-2 is where the cycle begins; the refrigerant is compressed resulting in a
significant increase in both pressure and temperature.
Stage 3-4 is where the superheated refrigerant remains at a constant high pressure but
loses heat to an external source, usually water or air, within the condenser.
Stage 4-1 is where the refrigerant remains at a constant low pressure and absorbs
heat from the source where the entire cycle is repeated.

26. 13
2.5 Concept of Heat Transfer
Incropera & De Witt (1990: 2) state that ‘heat transfer (heat) is energy in transit due
to a temperature difference’. There are three fundamential modes of heat transfer
which are conduction, convection and radiation. Heat exchangers and refrigeration
systems effectively transfer heat by means of convection when cooling milk.
2.5.1 Convective heat transfer
Convective heat transfer occurs where there are fluids in motion at two different
temperatures with a bounding surface (Bejan, 2013). When the fluid in motion is
caused to move away from the heat source, it carries the transferred energy with it.
Convective heat transfer can be divided into two distinct categories, depending on
the driving force causing the liquid to flow. The first category, natural or free
convection, occurs when the movement of fluid is due to a temperature difference.
During the transfer of heat, the associated density changes and buoyant effect causes
the fluid to naturally circulate. The second category, forced or assisted convection,
occurs when the fluid is forced over a hot or cold surface by a fan or a pump (Kraus,
et al., 2001). A more detailed analysis can be achieved by dividing both of these
categories into two further categories, which define the way in which the fluid is
flowing, whether it’s turbulent or streamline/laminar.
2.5.1.1 Heat Exchangers
As mentioned by Mills (1995), ‘the most common type of heat exchanger is the two-
stream steady-flow exchanger, with parallel, counter- or cross-flow of the two
streams’. Both arrangements produce different variations in temperature along the
heat exchangers, which is illustrated in the following Figures.

27. 14
Figure 8: Rate of heat transfer under parallel flow (Source: Moss, 1998)
Figure 8 represents the temperature profile of a heat exchanger using parallel flow.
The heat transfer is at its peak when both fluids enter the unit on the left hand side.
As the fluid passes through the unit, the heat transfer is greatly reduced as the
temperature difference is reduced. T1 and T2 represent the milk inlet and outlet
temperatures while t1 and t2 represent the water inlet and outlet temperatures.
As a comparison to the previous figure, Figure 9 represents the temperature profile
for a heat exchanger using counter-flow. The temperature drop throughout the heat
exchanger remains relatively constant. As a result of this, the greater the heat transfer
area of a counter-flow heat exchanger, the greater the heat transfer.

28. 15
2.5.1.2 Formulae Involved
According to Jones & Hawkins (1986), the basic equation for calculating convective
heat transfer takes factors such as surface area, temperature differential and the
relevant coefficients into consideration. The following information is based on
forced convective heat transfer as both fluids are pumped through the pre-coolers.
Equation 1: Basic heat transfer equation
𝑸 = 𝒉 𝐜 𝑨 ∆𝑻
Where, Units:
Q represents the heat transferred per unit time (W)
hc represents the convective heat transfer coefficient (W/m2
K)
A represents the heat transfer surface area (m2
)
ΔT represents the temperature difference between both fluids (°C)
Figure 9: Rate of heat transfer under counter-flow (Source: Moss, 1998)

29. 16
When determining the heat transfer across a heat exchanger, DeWitt, et al., (2007)
recommends taking the following assumptions into consideration:
1) ‘Negligible heat loss to surroundings’
2) ‘Negligible plate thermal resistance and fouling factors’
3) ‘Identical gap-to-gap heat transfer coefficients’
2.5.1.2.1 Convective Heat Transfer Coefficient
According to Incropera & De Witt (1990: 642), ‘an essential, and often the most
uncertain part of any heat exchanger analysis is determination of the overall heat
transfer coefficient’.
In terms of forced convection, dimensionless numbers are effectively used to
determine the convective heat transfer coefficient. These consist of the Nusselt
Number (Nu), the Reynolds Number (Re) and the Prandtl Number (Pr). With the
Nusselt Number being the dependent variable; both the Reynolds Number and the
Prandtl Number must be calculated first. A relatively large Nusselt number
resembles highly efficient convective heat transfer.
Equation 2: Formulae for calculating dimensionless numbers
𝑅𝑒 =
𝜌 𝑢 𝑑
𝜇
𝑃𝑟 =
𝜇 𝐶𝑝
𝑘
𝑁𝑢 =
ℎ𝑐 𝐿
𝑘
Where, Units:
ρ represents the density of the fluid kg/m³
u represents the mean velocity m/s
L/d represents the characteristic dimension m
μ represents the dynamic viscosity kg m/s
Cp represents the specific heat capacity (SHC) kJ/kg °C
k represents the thermal conductivity W/mK
hc represents the convective heat transfer coefficient W/m²K

30. 17
Another element which must be considered is the characteristics of the flow; whether
it’s laminar or turbulent. Different equations are used, depending on the flow pattern,
to determine the Nusselt number for the convective heat transfer coefficient.
Equation 3: Equations used to determine type of flow
Laminar Flow: Nu = 1.86 (RedPr)1/3
(d/L)1/3
(tb/tw)0.14
Turbulent Flow: Nu = 0.023 Red
0.8
Prn
By calculating the Re number, the type of flow can be determined. The following
table displays the ranges for laminar, transitional and turbulent flow.
Table 1: Using the Re Number to determine type of flow
Reynolds Number Type of Flow
0 – 2,300 Laminar
2,300 – 4,000 Transitional
4,000 + Turbulent
Figure 10: Types of flow

31. 18
2.5.1.2.2 Log Mean Temperature Difference
In order to determine the effectiveness of a heat exchanger, while taking the
temperature variation into consideration, the use of the log mean temperature
difference (LMTD) provides more accurate results. The LMTD is the average
temperature difference between the hot and cold fluids at each end of the heat
exchanger and replaces ΔT in the basic convective heat transfer equation.
Equation 4: Log mean temperature difference (Source: Moss, 1998)
𝐿𝑀𝑇𝐷 𝑑𝑡 𝑚 =
( 𝑑𝑡 𝑚𝑎𝑥 − 𝑑𝑡 𝑚𝑖𝑛)
(𝐿𝑛
𝑑𝑡 𝑚𝑎𝑥
𝑑𝑡 𝑚𝑖𝑛
)
Where, depending on the specific flow arrangement, the following terms apply:
Parallel flow
𝑑𝑡 𝑚𝑎𝑥 = 𝑡ℎ1 − 𝑡 𝑐1 𝑑𝑡 𝑚𝑖𝑛 = 𝑡ℎ2 − 𝑡 𝑐2
Counter flow
𝑑𝑡 𝑚𝑎𝑥 = 𝑡ℎ1 − 𝑡 𝑐2 𝑑𝑡 𝑚𝑖𝑛 = 𝑡ℎ2 − 𝑡 𝑐1

32. 19
2.6 Existing Research Findings
Many companies involved in agriculture are conducting research in order to improve
efficiency on dairy farms in Ireland. The author has specifically focused on research
conducted by Teagasc and Lely.
Teagasc, also known as the Agriculture and Food Development Authority, are a
national body that provide integrated research, advisory and training services to the
agriculture and food industry. Teagasc have a dedicated research centre which
anticipates production requirements of a quickly changing industry and develops
sustainable systems for milk production. As stated on their website, ‘Moorepark is
one the world’s leading dairy research centres and specialises in pasture based
systems of milk production’ (Teagasc, 2015).
Researchers at Moorepark have conducted a series of energy audits on PHEs
currently in use on dairy farms across Ireland. Results concluded that the vast
majority of PHEs were underperforming due to insufficient milk-to-water flow
ratios, with the average being 1:1.2 (Dillion, et al., 2010). As recommended by Ryan
(2004), for optimum efficiecny of the PHE, the water flow rate should be at least
double the milk flow rate. Whereas a report produced by the Milk Development
Council at Teagasc suggests that a ratio of 1:1 is more typical in PHEs providing a
reduction of 10°C in milk temperature (Teagasc, 2012).
Table 2: Desired PHE outlet temperatures (Source: Ryan, 2004)
Water
Inlet
(°C)
Water/Milk 1:1 Water/Milk 2:1 Water/Milk 3:1
Milk (°C) Water (°C) Milk (°C) Water (°C) Milk (°C) Water (°C)
10 20 27 15 20 14 17
15 22 28 19 23 18 21
20 25 30 23 27 22 25
Table 2 displays the desired temperatures the outlet fluids should reach at different
water to milk ratios when the milk entering is at 35°C. For example at a ratio of 2:1,
with GW entering the PHE at 10°C it should ideally leave at 20°C causing the milk
to reduce to 15°C.

33. 20
Both DX and indirect expansion bulk tanks have also been thoroughly investigated.
Teagasc believe DX bulk tanks have the ability to cool up to 75 litres of milk per
kWh of energy consumed while IBs are only able to cool 50 litres of milk per kWh
of energy consumed (Teagasc, 2012). While Dillion, et al., (2010), also suggests that
ice banks are considered less efficient in terms of energy consumed per litre of milk
cooled.
Lely are innovators in agriculture and leaders in dairy equipment, robotic milking
systems and forage machinery. The AMS under investigation is the Lely Astronaut
A4. Researchers at Lely have conducted performance analysis tests on their compact
cooler in order to determine optimum flow ratios, with results showing water-to-milk
ratio of 2:1 is most efficient. According to documents received from Lely in
Appendix A, the presence of a compact cooler in an AMS can reduce the cooling
demand by up to 50%.
2.7 Chapter Summary
This chapter has provided a review of the available literature and previously
conducted research regarding the topic of milk cooling on dairy farms. It has
revealed some interesting facts which will be used as a comparison to test the
research solidarity in the discussion chapter. At this point, the reader should have an
understanding of the importance of cooling milk, the different cooling methods
available and how to calculate the convective heat transfer.

34. 21
Chapter 3 - Research Methodology
3.1 Chapter Overview
The main aim of this chapter is to explain the chosen methods of research that will be
adopted to help investigate the aforementioned hypothesis. In order to communicate
and adhere to the objectives and goals mentioned at the beginning of this
dissertation, the appropriate research methodology must be undertaken. According to
Kothari (2004: 1), ‘the purpose of research is to discover the answers to questions
through the application of scientific procedures’ with its main aim being to discover
the hidden truth which has not been discovered as of yet. The author has decided to
adopt a quantitative approach by generating numerical data from a number of case
studies. In total, there are five case studies, each based on a dairy farm with a
different milk cooling system. The results generated will provide dairy farmers with
knowledge and guidance when investing in efficient milk cooling technologies.
3.2 Review of Objectives
To reach the overall objective of determining the most energy efficient method of
cooling milk on dairy farms the following list of key objectives must be adhered to:
 To review the available literature surrounding milk cooling on dairy farms.
 To investigate the various methods of cooling milk in both automatic and
conventional milking systems.
 To monitor each milk cooling system in terms of energy performance.
 To analyse and compare each method in order to determine the most energy
efficient.
 To provide recommendations based on the authors findings and identify
potential areas for further, in-depth research.
3.3 Hypothesis
The integrity of the following statement shall be tested by the following research:
“Pre-cooling is considered an energy efficient solution to reduce milk cooling
demands on Dairy Farms”.

35. 22
3.4 Choice of Research Methodology
The author has chosen to take a quantitative approach for gathering the numerical
data by the establishment of five case studies on dairy farms that consist of different
cooling systems. As mentioned by Denscombe (2003), such an approach has an aura
of scientific respectability and conveys a sense of solid, objective research.
According to Hammersley & Gomm (2012), case studies are invaluable as they
allow researchers to examine problems in practical, real-life situations. Byrne (2002)
suggests that another perk of quantitative research is the ability to measure the
variable, instead of assuming a variable.
With regards to secondary research, documents and reports of previously conducted
research were received from the likes of Teagasc and Lely. Additional information
was sourced from the WIT database, journal publications such as “Journal of Dairy
Science” and numerous books from the WIT library. One of the biggest flaws with
secondary research is the lack of reliability; not all websites can be trusted that their
information is correct, accurate and up to date, i.e. Wikipedia.
3.5 Research Limitations
As with any form of research, limitations are always going to be a factor. The author
has identified the following factors that may have an influence on the results derived
from the research:
 Due to time constraints, the cooling systems can only be monitored for one
cycle. Ideally each system should be monitored over a period of 12 months in
order to provide a more in-depth analysis.
 Refrigeration units and pre-coolers are not all manufactured by the same
company therefore efficiencies will slightly differ.
 The inability to measure the GW pumps power for the cycle. By manually
measuring the water volume consumed and assuming the GW pumps
efficiency will lead to a minute level of inaccuracy.
3.6 Chapter Summary
At this stage the reader should be able to visualise the appointed objectives, have a
firm understanding about the process through which the author intends to gather the
relevant data and the limitations involved.

36. 23
Chapter 4 - Monitoring / Methods of Data Capture
4.1 Chapter Overview
The purpose of this chapter to explain the chosen monitoring period, the parameters
recorded and the equipment used.
4.2 Monitoring Period
Due to time restrictions and sensor availability, the monitoring period has been
chosen to be one cycle. This cycle will begin when the bulk tank is emptied on the
first collection day and finish at the same stage on the following collection day. The
docket, provided by the milk processor, contains the milk volume and the times the
cycle begun and finished. Each cycle starts with a wash and once a large volume of
milk enters the bulk tank, initial cooling begins. This is followed by agitation and
maintenance cooling until the milk is collected by the processor, representing the end
of the cycle.
4.3 Parameters Recorded
4.3.1 Power consumption
The main parameter recorded was the power consumed by the refrigeration unit. The
live feed into the refrigeration units control box, which was located with the help of a
highly qualified and competent electrician, was monitored. The recorded power
consumption could then be converted into energy consumption (kWh) by using the
following equation:
Equation 5: Basic equation to convert Power to Energy
𝐸𝑛𝑒𝑟𝑔𝑦 (𝑘𝑊ℎ) = 𝑃𝑜𝑤𝑒𝑟 (𝑘𝑊) 𝑥 𝑇𝑖𝑚𝑒 (𝐻𝑜𝑢𝑟𝑠)
4.3.2 Fluid temperatures
The temperatures of both milk and water were recorded at various stages. For
systems with pre-coolers, both temperatures were recorded before and after the pre-
cooling unit to determine its effectiveness. For systems without a pre-cooler, the
temperature of the milk just before it entered the refrigeration unit was recorded so it
could be compared to temperatures associated with the presence of a pre-cooler.

37. 24
4.3.3 Volume of water required
The inability to monitor the power consumption of the GW pump resulted in the
volume of water required having to be determined. The volume of water required
was measured differently in both systems. The characteristics of the AMS meant the
use of a flow meter wouldn’t provide an accurate measurement. As the milk had an
intermittent flow pattern, the volume of water required had to be measured using a
large container. The large container was left to fill for a period of time while cows
were being milked. The water collected in the container was measured in terms of
litres and compared to the litres of milk produced in the same period of time. This
information was gathered from the robots PC. By doing this, an average water to
milk ratio could be derived and by using this ratio as a multiplication factor, the
approximate volume of water required for an entire cycle could be determined.
Measuring the volume of water required by the CMS could be determined using a
bucket and a stopwatch. By measuring the time it took to fill the bucket, the water
flow rate could be determined. However, the water would only be flowing at this rate
during milking hours. Milking hours could simply be determined by analysing the
inlet milk temperature graph. A sudden peak in temperature would represent the start
of milking while a sudden drop would represent the end of milking.
Although the ideal way to measure this parameter would be to monitor the energy
consumption of the GW pump, however, the existing set up meant the pump was
providing water for the entire farm. Nevertheless, the pump power can be calculated
through a number of equations involving the water volume.
4.3.4 Volume of milk cooled
The volume of milk cooled during the cycle can be found on the docket provided by
the milk supplier after each collection.
4.4 Equipment Used
4.4.1 Electricity Meters
With the aid of an OWL meter, the energy consumption of the refrigeration unit can
be recorded and analysed for one cycle. The OWL meter is a Wireless Electric
Monitor (WEM). By placing the inductive clamp around the electricity source, the
total energy consumption can be measured. The inductive clamp is connected to a

38. 25
transmitter which transmits information to the monitor. The power consumption is
measured at one minute intervals and is saved onto the monitor. Once the monitoring
is finished, the data can be analysed by connecting the monitor to the OWL software
on a laptop. This provides a detailed breakdown on the energy usage during the
monitoring period which is shown in kilowatt hours (kWh). The OWL meter can also
take energy cost and greenhouse gas (GHG) emissions into consideration (Owl,
2015). It is expected that the energy consumption will vary throughout the process,
depending on the cooling stage and the storage temperature of the refrigeration unit.
The following figures illustrate the typical components of an OWL kit and the
detailed breakdown of the energy usage.
Figure 11: The OWL transmitter, CT clamp & display monitor (Source: The Owl,
2016)
Figure 12: Various ways of analysing logged data on the software (Source: The
Owl, 2016)
As a result of the OWL meters recording power consumption every 1 minute the
basic power-to-energy conversion calculation proves insufficient. The correct

39. 26
method of calculating the energy consumed for the duration of the cycle is as follows
(refer to Appendix O for further information; in particular pages 21 & 23):
1) Export all data into an Excel spreadsheet
2) Locate ‘kW_Raw_Data’ column. Convert all the data by dividing each
reading by 1,000.
3) The summation of the Converted Raw Data during the monitored cycle is the
energy (kWh) consumed
Equation 6: Conversion of Raw Data
𝐶𝑜𝑛𝑣𝑒𝑟𝑡𝑒𝑑 𝐷𝑎𝑡𝑎 (𝑘𝑊ℎ) =
𝐸𝑎𝑐ℎ 𝑟𝑒𝑎𝑑𝑖𝑛𝑔 𝑜𝑓 𝑘𝑊_𝑅𝑎𝑤_𝐷𝑎𝑡𝑎
1000
The summation of the converted data for the entire cycle represents the amount of
energy (kWh) consumed during the cycle.
4.4.2 Temperature Loggers
Various TESTO temperature loggers, in particular the 175-T3 and the 635 models,
were used during this research. These loggers consisted of a large display screen with
an alarm indication and the ability to take simultaneous measurements which made
them ideal for continuous monitoring (TESTO, 2015). By placing the sensors on the
water and milk inlets/outlets on the pre-cooler, the effectiveness of the unit could be
determined. The temperatures were logged onto the device and once the monitoring
was finished, they were analysed in great detail. It is expected that the temperature of
the pipe will rise when milk flows through it and drop to a constant low outside
milking hours. The following figures represent the temperature loggers used
throughout this research.
Figure 13: Various temperature loggers used (Source: TESTO, 2015)

40. 27
4.4.2.1 Measurement Frequency
The fluid temperatures were recorded every pre-set period of time. This was set
using the relevant software and differed in both systems. For the CMS, the milk flow
is relatively constant during milking hours so therefore a single speed pump was
present. This meant that a measurement could be recorded every one minute as the
temperature wouldn’t fluctuate too much. The average temperatures were easily
calculated as milking hours could be determined from the relevant graphs. As for the
AMS, where milk flow wasn’t constant, a variable speed pump was present. The
variable speed pump kicked in every time a cow was finished milking. Adjusting the
time interval, for which a temperature measurement was recorded, to every 10
seconds increased the likelihood of obtaining an accurate reading. Determining the
average temperatures for the AMS would prove to be trickier as the milking hours
were defined as the entire cycle. By comparing the milking times on the robots PC to
the times a temperature was recorded, very accurate average temperatures could be
calculated.
4.5 Electricity Tariff
Electricity tariffs are more commonly referred to as the price paid per unit of
electricity consumed. This price is dependent on the electricity supplier the customer
is operating with. The rates paid per unit of electricity vary depending on the type of
meter installed. Where single rate meters are installed, the customers pays a fixed
price per unit of electricity no matter what time of day it is (Electric Ireland, 2016).
Where Night Saver meters are installed, the day and night consumption are
separately metered. This allows customers to use electricity during the night at a
cheaper rate. During the winter, the night rate applies between 11:00pm and 8:00am
while during the summer; it applies between 12:00 midnight and 9:00am (SEE
Airtricity, 2016).
Electricity is charged by the number Kilowatt Hours (kWh) consumed. Kilowatts
(kW) refer to the power rating of an appliance whereas a kWh refers to the amount of
energy that appliance consumes during a time period of one hour (BizEE, 2016). The
following table shows the prices paid per kWh on the Night Saver meter for the
leading electricity companies in Ireland.

41. 28
Table 3: Different Day/Night Rates (Source: Electric Ireland, 2015; SEE Airtricity,
2015; & Bord Gais Energy, 2015)
Day Rate (c/kWh)
(Ex. VAT)
Night Rate (c/kWh)
(Ex. VAT)
Electric Ireland 17.84 8.81
SEE Airtricity 17.59 8.71
Bord Gais Energy 17.32 8.57
4.6 Chapter Summary
From reading this chapter, the reader should understand the purpose of recording the
chosen parameters and the method in doing so. They should also have a brief
understanding about the milk flow rates of an AMS compared to a CMS. The cost
per unit of electricity has been included for use in the financial appraisal section, for
comparsion purposes it is assumed that each farm contains a nightsaver meter and
have the same electricity supplier.

42. 29
Chapter 5 - Case Study
5.1 Chapter Overview
The purpose of this chapter is to describe the characteristics of each Farm to the
reader. The differences on each farm are noted in the following text and are included
briefly in the discussion chapter as a reminded.
5.2 Description of Case Studies
For each of the following case studies, the milk is pumped from the storage jar in the
direction of the bulk tank. Whether it passes through a pre-cooler or not depends on
the particular system. All of the bulk tanks, except the one on Farm C, automatically
wash themselves after each collection which will increase energy consumption. The
bulk tanks used in the AMS are bottom fill while the bulk tanks in a CMS are top fill.
Schematics for each cooling system which include the locations of the temperature
loggers are available in Appendix N.
5.2.1 Farm A
The first farm contains an AMS with the presence of a THE and a DX bulk tank. GW
is used as the cooling source for the THE. GW flow rate is controlled by a solenoid
located at the water inlet which is supplied by a ¾ inch alkathene water pipe. The
bulk tank, which is bottom fill for increased efficiency, is cooled by two externally
located condensers.
5.2.2 Farm B
The second farm is based on the same system as mentioned in the previous farm but
differs in one aspect. For Farm B and as a comparison, the water flow to the THE
was switched off, ultimately deactivating the pre-cooler. Now that the pre-cooler had
been deactivated, the milk would be pumped from the storage jar in the robot,
through the compact cooler and into the bulk tank. Deactivation of the THE should
increase the cooling load of the bulk tank.
5.2.3 Farm C
The third farm consists of a CMS with the absence of a PHE. The milk is pumped
from the storage jar directly into the DX bulk tank. The bulk tank is manually
washed after milk collection.

43. 30
5.2.4 Farm D
The fourth farm contains a CMS with the presence of a PHE and a DX bulk tank.
GW is used as the cooling source and the flow rate is manually operated by means of
a valve at the side of the PHE. GW is supplied by a ¾ inch alkathene water pipe.
5.2.5 Farm E
The final farm contains a CMS which consists of a double stage PHE and an indirect
expansion bulk tank. The first PHE uses GW as the cooling source while the second
PHE uses CW as the cooling source. The GW is supplied by a 1 inch alkathene water
pipe. The CW for the PHE is generated by circulating water through an IB. The
indirect expansion bulk tank uses another IB instead of refrigerant to provide final
cooling to the milk. The CW is circulated between the base of the bulk tank and the
IB by means of a pump positioned on top of the IB.
5.3 Chapter Summary
Upon reading this chapter, the reader should understand the differences between each
Farm. Schematics of each system display the locations of where the temperature
loggers were placed and are available in Appendix N.

44. 31
Chapter 6 - Research Findings
6.1 Chapter Overview
This chapter reveals the findings gathered from each farm involved in the research.
Each parameter is discussed and briefly analysed with temperature and power
profiles illustrated graphically to provide the clearest understanding.
6.2 Farm A
The monitoring period is as follows:
18/01/2016 @ 10:11am to 21/01/2016 @ 08:18am
The following parameters were recorded:
1) Volume of milk cooled
2) Milk/water temperatures before and after THE
3) Volume of water required
4) Power consumption of refrigeration unit
5) Power consumption of GW pump
6.2.1 Parameter 1 – Volume of milk cooled
According to the docket produced by the milk processor, the volume of milk cooled
during the monitored cycle was 5,447 litres.
6.2.2 Parameter 2 – Milk & water temperatures associated with THE
Both the milk and water temperatures were recorded before and after the pre-cooler
to determine its effectiveness.
6.2.2.1 Milk Temperature
The following graph displays the variation of the milk temperature before and after
the pre-cooler for the duration of the cycle

45. 32
The sudden peaks in temperature are as a result of the AMS conducting a system
wash. This particular AMS was programmed to carry out three washes daily;
accumulating to a total of nine washes during the cycle. The variation of temperature
throughout the cycle is related to the number of cows milked. A relatively constant
inlet temperature represents that the cows are being milked consecutively throughout
the day while a considerable drop in inlet temperature can represent idle robots.
The presence of a variable speed pump resulted in a large fluctuation in temperatures
throughout the cycle so therefore simply getting an average temperature would be
inaccurate. By matching the milking times shown on the robots PC to the times a
milk inlet temperature was recorded at the pre-cooler for a number of cows, a very
accurate temperature reading can be made. By doing so, the average milk inlet
temperature was 29.48°C while the average milk outlet temperature was 13.36°C;
refer to Appendix B.
6.2.2.2 Water Temperature
As a result of an error occurring with the sensor on the water inlet and outlet, the
temperature was only logged for a short period of time. Nevertheless, an accurate
average water temperature can still be calculated as the sensors were attached the
night before collection so therefore contained an extra twelve hours of data. By
matching the milk inlet temperatures with the milking times, the corresponding water
temperatures can be determined. The following graph displays the variation of the
0
10
20
30
40
50
60
70
80
10:11
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
08:17
Temp.
(°C)
Time (24hrs)
Milk Temp. In (°C) Milk Temp. Out (°C)
Figure 14: Farm A - Associated milk temperatures

46. 33
GW temperature before and after the pre-cooler. For milking times, please refer to
Appendix B.
Figure 15: Farm A - Associated water temperatures during cycle
The two sudden peaks in the water inlet temperature are as a result of the system
wash. Some of the hot water used for the wash exits the THE through the water inlet
where a T-joint is present. The T-joint contains two solenoids; one which controls
water flow and the other which controls whether the water enters the pre-cooler or
goes down the drain.
The author decided that the water temperature data collected during the cycle was
not enough to provide an accurate average temperature so therefore included the data
gathered from the night before. The following graph displays the data collected
outside the cycle.
0
5
10
15
20
25
30
35
40
45
10:11
12:00
18:00
20:31
Temp.
(°C)
Time (24hr)
Water Temp. In (°C) Water Temp. Out (°C)

47. 34
Figure 16: Farm A - Associated water temperature before & during cycle
As shown by the graph, the temperature profile is very similar to the data gathered
during the cycle. The average water temperature was determined by matching
milking times with the times a temperature was recorded and can be seen in
Appendix B. The average temperature of the water inlet was 8.65°C and at the outlet
was 15.8°C.
6.2.3 Parameter 3 – Volume of GW required by THE
By allowing the outgoing water from the THE flow into a container for a period of
time and then calculating the amount of milk produced in that same period of time, a
milk-to-water ratio could be determined. The milk yield during this period of time
can be seen in Appendix C. The ratio was then used as a multiplication factor to
determine the volume of water required. This resulted in a water-to-milk ratio of
2.1:1. By multiplying the volume of milk produced during the cycle by this ratio, the
volume of water required is determined.
5,447 𝑙𝑖𝑡𝑟𝑒𝑠 𝑜𝑓 𝑚𝑖𝑙𝑘 𝑥 2.1 = 11,438.7 𝑙𝑖𝑡𝑟𝑒𝑠 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑
6.2.4 Parameter 4 – Power consumption of refrigeration unit
The power consumption of the refrigeration unit throughout the entire cycle was
measured by the OWL meter. According to the logged data received from the meter,
the raw data amounted to 17,471kW. The following graph illustrates the
consumption profile during the cycle.
0
5
10
15
20
25
30
35
40
45
21:54
00:00
06:00
10:11
12:00
18:00
20:31
Temp.
(°C)
Time (24hr)
Water Temp. In (°C) Water Temp. Out (°C)

48. 35
To convert the raw data into the energy consumption (kWh) each individual reading
had to be divided by 1,000. The summation of these values represented the energy
consumed during the monitored cycle. The summation of the total ‘kW_Raw_Data’
divided by 1,000 yields the same result.
𝐶𝑜𝑛𝑣𝑒𝑟𝑡𝑒𝑑 𝐷𝑎𝑡𝑎 (𝑘𝑊ℎ) =
𝑆𝑢𝑚𝑚𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑡𝑜𝑡𝑎𝑙 𝑘𝑊_𝑅𝑎𝑤_𝐷𝑎𝑡𝑎
1,000
𝐶𝑜𝑛𝑣𝑒𝑟𝑡𝑒𝑑 𝐷𝑎𝑡𝑎 (𝑘𝑊ℎ) =
17,471𝑘𝑊
1,000
𝐸𝑛𝑒𝑟𝑔𝑦 (𝑘𝑊ℎ) = 17.47𝑘𝑊ℎ
6.2.5 Parameter 5 – Power consumption of GW pump
The power consumption mentioned in parameter 4 only represents the power
consumed by the refrigeration unit for the entire cycle; now the power consumption
of the GW pump must be calculated. As there was no way of actually monitoring the
pump on this farm, a number of calculations were carried out to determine the pump
power. Due to the characteristics of this farm, there was no way of determining the
time that the GW pump was operating in order to supply water to the pre-cooler only.
So therefore, the following calculation is based on the pump house being 50 metres
away from the pre-cooler.
0
100
200
300
400
500
600
10:11
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
08:18
Power
(kW)
Time (24hr)
Figure 17: Farm A - Power consumption profile during cycle

49. 36
Additional information:
 Volume of GW required is 11,438.7 litres
 Assume pump efficiency is 80%
 Total pressure loss of 6,000Pa within pipe (taken from CIBSE guides)
 Operation time of GW pump (entire cycle): 4,207 minutes
Equation used:
Power (kW) =
PT qv
η
Where,
PT represents the total pressure (kPa)
qv represents the water flow rate in litres per second (l/s)
η represents the efficiency of the GW pump
STEP 1:
First of all the water flow rate must be calculated in litres per second.
𝐹𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑙/𝑠) =
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝐺𝑊 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 (𝑙𝑖𝑡𝑟𝑒𝑠)
𝑇𝑖𝑚𝑒 𝑖𝑛 𝑜𝑝𝑒𝑟𝑎𝑡𝑖𝑜𝑛 (seconds)
𝐹𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑙/𝑠) =
11,438.7 𝑙𝑖𝑡𝑟𝑒𝑠
252,420 𝑠𝑒𝑐
𝐹𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑙/𝑠) = 0.045𝑙/𝑠
STEP 2:
Now the approximate pump power can be calculated the following equation.
Power (kW) =
PT qv
η

50. 37
PT = 6,000Pa or 6kPa
qv = 0.045l/s
η = 0.8
Power (kW) =
6 x 0.045
0.8
Power (kW) = 0.338kW
This figure represents the power consumed by the pump for the duration of one hour.
To determine the energy consumed by the pump, the factor of time has to be taken
into consideration. Due to the inability to measure the operation time of the GW
pump, the following calculation is based on the pump being in constant operation
throughout the cycle.So therefore, the energy consumption is as follows:
Duration of cycle: 4,207 minutes
𝐺𝑊 𝑝𝑢𝑚𝑝 𝑒𝑛𝑒𝑟𝑔𝑦 𝑐𝑜𝑛𝑠𝑢𝑚𝑝𝑡𝑖𝑜𝑛 (𝑘𝑊ℎ) = 𝑃𝑜𝑤𝑒𝑟 (𝑘𝑊) 𝑥 𝑇𝑖𝑚𝑒 (ℎ𝑜𝑢𝑟𝑠)
= 0.338𝑘𝑊 𝑥
4,207
60
𝐸𝑛𝑒𝑟𝑔𝑦 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑑 𝑏𝑦 𝐺𝑊 𝑝𝑢𝑚𝑝 = 23.69𝑘𝑊ℎ

51. 38
6.2.6 Summary of Findings
Farm A
Duration of cycle 4,207 minutes
Average milk inlet temperature 29.48°C
Average milk outlet temperature 13.36°C
Average water inlet temperature 8.65°C
Average water outlet temperature 15.8°C
Volume of milk cooled 5,447 litres
Energy consumption of refrigeration unit 17.471kWh
Volume of GW required 11,438.7 litres
Energy consumption of GW pump 23.69kWh
Total energy consumed during cycle 41.161kWh

52. 39
6.3 Farm B
The monitoring period is as follows:
29/01/2016 @ 10:03am to 01/02/2016 @ 10:11am
The following parameters were recorded:
1) Volume of milk cooled
2) Milk temperature just before it entered the refrigeration unit
3) Power consumption of refrigeration unit
6.3.1 Parameter 1 – Volume of milk cooled
According to the docket produced by the milk processor, the volume of milk cooled
during the monitored cycle was 5,928 litres.
6.3.2 Parameter 2 – Milk temperature upon entering refrigeration unit
The milk temperature was recorded just before it entered the refrigeration unit in
order to determine the impact of the absence of precooling. The following graph
displays the temperature profile throughout the entire cycle.
Once again, the average milk inlet temperature was determined by matching the
milking times with the times a temperature was recorded. This resulted in an average
milk inlet temperature of 27.28°C, which can be seen in Appendix D.
0
10
20
30
40
50
60
70
10:03
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
10:11
Temp.
(°C)
Time (24hr)
Milk Temp In[°C]
Figure 18: Farm B - Associated milk temperatures

53. 40
6.3.3 Parameter 3 – Power consumption of refrigeration unit
The power consumption of the refrigeration unit throughout the entire cycle was
measured by the OWL meter. According to the logged data received from the meter,
the raw data amounted to 86,480.08kW. The following graph illustrates the
consumption profile during the cycle.
To convert the raw data into the energy consumption (kWh) each individual reading
had to be divided by 1,000. The summation of these values represented the energy
consumed during the monitored cycle. The summation of the total ‘kW_Raw_Data’
divided by 1,000 yields the same result.
𝐶𝑜𝑛𝑣𝑒𝑟𝑡𝑒𝑑 𝐷𝑎𝑡𝑎 (𝑘𝑊ℎ) =
𝑆𝑢𝑚𝑚𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑡𝑜𝑡𝑎𝑙 𝑘𝑊_𝑅𝑎𝑤_𝐷𝑎𝑡𝑎
1,000
𝐶𝑜𝑛𝑣𝑒𝑟𝑡𝑒𝑑 𝐷𝑎𝑡𝑎 (𝑘𝑊ℎ) =
86,480.08𝑘𝑊
1,000
𝐸𝑛𝑒𝑟𝑔𝑦 (𝑘𝑊ℎ) = 86.48𝑘𝑊ℎ
0
50
100
150
200
250
10:03
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
10:11
Power
(kW)
Time (24hr)
Figure 19: Farm B - Power consumption profile during cycle

54. 41
6.3.4 Summary of Findings
Farm B
Duration of cycle 4,328 minutes
Average milk inlet temperature 27.28°C
Volume of milk cooled 5,928 litres
Energy consumption of refrigeration unit 86.48kWh

55. 42
6.4 Farm C
The monitoring period is as follows:
20/01/2016 @ 12:30pm to 23/01/2016 @ 04:47am
The following parameters were recorded:
1) Volume of milk cooled
2) Milk temperature just before it entered the refrigeration unit
3) Power consumption of refrigeration unit
6.4.1 Parameter 1 – Volume of milk cooled
According to the docket produced by the milk processor, the volume of milk cooled
during the monitored cycle was 3,102 litres.
6.4.2 Parameter 2 – Milk temperature upon entering refrigeration unit
The milk temperature was recorded just before it entered the refrigeration unit in
order to determine the impact of the absence of precooling. The following graph
displays the temperature profile throughout the entire cycle.
A sudden rise in temperature represents the start of milking as the warm milk passes
through the pipe. The average milk inlet temperature is determined by calculating the
average during milking hours as opposed to the entire cycle for an AMS. The
average milk inlet temperature was found to be 33.49°C and can be seen in Appendix
E.
0
10
20
30
40
50
60
12:30
18:00
00:00
06:00
12:00
18:00
00:00
06:00
12:00
18:00
00:00
04:47Temp.
(°C
Time (24hr)
Milk Temp. (°C)
Figure 20: Farm C - Associated milk temperatures

56. 43
6.4.3 Parameter 3 – Power consumption of refrigeration unit
The power consumption of the refrigeration unit throughout the entire cycle was
measured by the OWL meter. According to the logged data received from the meter,
the raw data amounted to 77,193.06kW. The following graph illustrates the
consumption profile during the cycle.
To convert the raw data into the energy consumption (kWh) each individual reading
had to be divided by 1,000. The summation of these values represented the energy
consumed during the monitored cycle. The summation of the total ‘kW_Raw_Data’
divided by 1,000 yields the same result.
𝐶𝑜𝑛𝑣𝑒𝑟𝑡𝑒𝑑 𝐷𝑎𝑡𝑎 (𝑘𝑊ℎ) =
𝑆𝑢𝑚𝑚𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑡𝑜𝑡𝑎𝑙 𝑘𝑊_𝑅𝑎𝑤_𝐷𝑎𝑡𝑎
1,000
𝐶𝑜𝑛𝑣𝑒𝑟𝑡𝑒𝑑 𝐷𝑎𝑡𝑎 (𝑘𝑊ℎ) =
77,193.06𝑘𝑊
1,000
𝐸𝑛𝑒𝑟𝑔𝑦 (𝑘𝑊ℎ) = 77.193𝑘𝑊ℎ
0
100
200
300
400
500
600
12:30
18:00
00:00
06:00
12:00
18:00
00:00
06:00
12:00
18:00
00:00
04:47
Power
(kW)
Time (24hr)
Figure 21: Farm C - Power consumption profile during cycle

57. 44
6.4.4 Summary of Findings
Farm C
Duration of cycle 3,857 minutes
Average milk inlet temperature 33.49°C
Volume of milk cooled 3,102 litres
Energy consumption of refrigeration unit 77.193kWh

58. 45
6.5 Farm D
The monitoring period is as follows:
22/01/2016 @ 04:36am to 25/01/2016 @ 04:41am
The following parameters were recorded:
1) Volume of milk cooled
2) Milk/water temperatures before and after the PHE
3) Volume of water required
4) Power consumption of refrigeration unit
5) Power consumption of GW pump
6.5.1 Parameter 1 – Volume of milk cooled
According to the docket produced by the milk processor, the volume of milk cooled
during the monitored cycle was 3,464 litres.
6.5.2 Parameter 2 – Milk & water temperatures associated with PHE
Both the milk and water temperatures were recorded before and after the pre-cooler
to determine its effectiveness.
6.5.2.1 Milk Temperature
The following graph displays the variation of the milk temperature before and after
the pre-cooler for the duration of the cycle.
0
5
10
15
20
25
30
35
04:36
06:00
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
12:00
18:00
00:00
04:41
Temp.
(°C)
Time (24hr)
Milk Temp. In (°C) Milk Temp. Out (°C)
Figure 22: Farm D - Associated milk temperatures

59. 46
Once again, the average milk inlet and outlet temperatures were only determined
during milking hours. The average milk inlet temperature was found to be 29.38°C
while the average milk outlet temperature was found to be 20.06°C, as seen in
Appendix F.
6.5.2.2 Water Temperature
The following graph displays the variation of the water temperature before and after
the pre-cooler for the duration of the cycle.
The average water inlet temperature was found to be 10.11°C while the average
outlet temperature was found to be 16.36°C; table available in Appendix F.
6.5.3 Parameter 3 – Volume of GW required by PHE
The volume of GW required by the PHE to pre-cool the 3,464 litres of milk was
determined using a bucket and stopwatch. The complete table of recordings can be
found in Appendix G. By doing so, the water flow rate could be calculated.
𝐹𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑙/𝑠) =
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑏𝑢𝑐𝑘𝑒𝑡 (𝑙𝑖𝑡𝑟𝑒𝑠)
𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛 𝑡𝑜 𝑓𝑖𝑙𝑙 𝑏𝑢𝑐𝑘𝑒𝑡 (seconds)
𝐹𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑙/𝑠) =
9.1 𝑙𝑖𝑡𝑟𝑒𝑠
12.87 𝑠𝑒𝑐𝑜𝑛𝑑𝑠
𝐹𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑙/𝑠) = 0.707 𝑙/𝑠
0
5
10
15
20
25
04:36
06:00
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
12:00
18:00
00:00
04:41
Temp.
(°C)
Time (24hr)
Water Temp. In (°C) Water Temp. Out (°C)
Figure 23: Farm D - Associated water temperatures

60. 47
The water would only be flowing at this rate during milking hours. To determine
milking hours, the temperature data from the milk inlet to the PHE was analysed.
The following table displays the milking hours each day during the cycle; refer to
Appendix H for the analysed data.
Table 4: Farm D - Milking hours
Day Milking hours (24hr) Duration (mins)
1
07:17 – 08:20
17:30 – 18:31
63
61
2
07:14 – 08:11
17:18 – 18:15
57
57
3
07:14 – 08:15
17:11 – 18:09
61
58
The duration of each milking during the cycle can be seen in the Table 4, with the
total time spent milking accumulating to 357 minutes. This figure can be used to
determine the volume of water used for pre-cooling during the cycle by the following
equation.
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 (𝑙) = 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑙/𝑠) 𝑥 𝑇𝑖𝑚𝑒 𝑠𝑝𝑒𝑛𝑡 𝑚𝑖𝑙𝑘𝑖𝑛𝑔 (sec)
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 (𝑙) = 0.707𝑙/𝑠 𝑥 (357𝑥60)
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 (𝑙) = 15,143.94 litres

61. 48
6.5.4 Parameter 4 – Power consumption of refrigeration unit
The power consumption of the refrigeration unit throughout the entire cycle was
measured by the OWL meter. According to the logged data received from the meter,
the raw data amounted to 107,227.07kW. The following graph illustrates the
consumption profile during the cycle.
Figure 24: Farm D - Power consumption profile during cycle
To convert the raw data into the energy consumption (kWh) each individual reading
had to be divided by 1,000. The summation of these values represented the energy
consumed during the monitored cycle. The summation of the total ‘kW_Raw_Data’
divided by 1,000 yields the same result.
𝐶𝑜𝑛𝑣𝑒𝑟𝑡𝑒𝑑 𝐷𝑎𝑡𝑎 (𝑘𝑊ℎ) =
𝑆𝑢𝑚𝑚𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑡𝑜𝑡𝑎𝑙 𝑘𝑊_𝑅𝑎𝑤_𝐷𝑎𝑡𝑎
1,000
𝐶𝑜𝑛𝑣𝑒𝑟𝑡𝑒𝑑 𝐷𝑎𝑡𝑎 (𝑘𝑊ℎ) =
107,227.07𝑘𝑊
1,000
𝐸𝑛𝑒𝑟𝑔𝑦 (𝑘𝑊ℎ) = 107.23𝑘𝑊ℎ
0
20
40
60
80
100
120
140
160
180
04:36
06:00
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
12:00
18:00
00:00
04:41
Power
(kW)
Time (24hr)

62. 49
6.5.5 Parameter 5 – Power consumption of GW pump
The power consumption mentioned in parameter 4 only represents the power
consumed by the refrigeration unit for the entire cycle; now the power consumption
of the GW pump must be calculated. As there was no way of actually monitoring the
pump on this farm, a number of calculations were carried out to determine the pump
power. So therefore, the following calculation is based on the pump house being 50
metres away from the pre-cooler.
Additional information:
 Volume of GW required is 15,143.94 litres
 Assume pump efficiency is 80%
 Total pressure loss of 6,000Pa within pipe (taken from CIBSE guides)
 Operation time of pump (milking hours): 357 minutes
 Calculated water flow rate 0.707l/s
Equation used:
Power (kW) =
PT qv
η
Where,
PT represents the total pressure (kPa)
qv represents the water flow rate in litres per second (l/s)
η represents the efficiency of the GW pump
STEP 1:
Now the approximate pump power can be calculated the following equation.
Power (kW) =
PT qv
η
PT = 6,000Pa or 6kPa
qv = 0.707l/s

63. 50
η = 0.8
Power (kW) =
6 x 0.707
0.8
Power (kW) = 5.3kW
This figure represents the power consumed by the pump for the duration of one hour.
To determine the energy consumed by the pump, the factor of time has to be taken
into consideration. The GW pump would only be in operation for the duration of
milking hours. So therefore, the energy consumption is as follows:
Time spent milking during cycle: 357 minutes
𝐺𝑊 𝑝𝑢𝑚𝑝 𝑒𝑛𝑒𝑟𝑔𝑦 𝑐𝑜𝑛𝑠𝑢𝑚𝑝𝑡𝑖𝑜𝑛 (𝑘𝑊ℎ) = 𝑃𝑜𝑤𝑒𝑟 (𝑘𝑊) 𝑥 𝑇𝑖𝑚𝑒 (ℎ𝑜𝑢𝑟𝑠)
= 5.3𝑘𝑊 𝑥
357
60
𝐸𝑛𝑒𝑟𝑔𝑦 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑑 𝑏𝑦 𝐺𝑊 𝑝𝑢𝑚𝑝 = 31.55𝑘𝑊ℎ

64. 51
6.5.6 Summary of Findings
Farm D
Duration of cycle 4,325 minutes
Average milk inlet temperature 29.38°C
Average milk outlet temperature 20.06°C
Average water inlet temperature 10.11°C
Average water outlet temperature 16.36°C
Volume of milk cooled 3,464 litres
Energy consumption of refrigeration unit 107.23kWh
Volume of GW required 15,143.94 litres
Energy consumption of GW pump 31.55kWh
Total energy consumed during cycle 138.78kWh

65. 52
6.6 Farm E
The monitoring period is as follows:
11/02/2016 @ 09:26am to 13/02/2016 @ 09:00am
The following parameters were recorded:
1) Volume of milk cooled
2) Milk/water temperatures before and after the first PHE
3) Volume of water required
4) Milk/water temperatures before and after the second PHE
5) Power consumption of IB supplying second PHE
6) CW flow/return temperatures from IB to refrigeration unit
7) Power consumption of refrigeration unit and associated IB
8) Power consumption of GW pump
As a result of collection times, only four milkings were within the monitoring period
whereas a total of six milkings were monitored in the previous CMSs. Nevertheless,
by comparing the systems based on energy consumed per litre, solves this issue.
6.6.1 Parameter 1 – Volume of milk cooled
The volume of milk cooled was simply determined by checking the docket received
from the milk supplier after collection. For the monitored cycle, the volume of milk
cooled was 6,195 litres.
6.6.2 Parameter 2 – Milk & water temperatures associated with PHE 01
Both the milk and water temperatures associated with the first PHE were recorded in
order to determine its effectiveness.
6.6.2.1 Milk Temperature
The following graph displays the milk temperature profile before and after the first
PHE for the duration of the cycle.

66. 53
The average milk inlet temperature was calculated to be 30.89°C while the average
milk outlet temperature was calculated to be 19.77°C; please refer to Appendix I.
6.6.2.2 Water Temperature
The following graph displays the water temperature profile before and after the first
PHE for the duration of the cycle.
Figure 26: Farm E - Associated water temperatures with first PHE
The water inlet temperature was expected to be relatively constant whereas the above
graphs illustrates the temperature fluctuating approximately between 5°C and 10°C
throughout the cycle. The average water inlet temperature was calculated to be
7.86°C while the avergae outlet temperature was calcualted to be 20.52°C; refer to
Appendix I.
0
5
10
15
20
25
30
09:26
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
09:00
Temp.
(°C)
Time (24hr)
Water Temp. In (°C) Water Temp. Out (°C)
0
5
10
15
20
25
30
35
40
45
09:26
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
09:00
Temp.
(°C)
Time (24hr)
Milk Temp. In (°C) Milk Temp. Out (°C)
Figure 25: Farm E - Associated milk temperatures for first PHE

67. 54
6.6.3 Parameter 3 – Volume of GW required by PHE 01
The volume of GW required for the first PHE was determined using the same
method as on Farm D; with a bucket and stopwatch. Once again, a total of fifty
buckets were filled in order to determine an average flow rate; please refer to
Appendix J. By doing so, the average GW flow rate could be calculated.
𝐹𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑙/𝑠) =
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑏𝑢𝑐𝑘𝑒𝑡 (𝑙𝑖𝑡𝑟𝑒𝑠)
𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛 𝑡𝑜 𝑓𝑖𝑙𝑙 𝑏𝑢𝑐𝑘𝑒𝑡 (seconds)
𝐹𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑙/𝑠) =
9.1 𝑙𝑖𝑡𝑟𝑒𝑠
6.83 𝑠𝑒𝑐𝑜𝑛𝑑𝑠
𝐹𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑙/𝑠) = 1.33 𝑙/𝑠
The water would only be flowing at this rate during milking hours. To determine
milking hours, the temperature data from the milk inlet to the first PHE was
analysed. The following table displays the milking hours each day during the cycle;
refer to Appendix K for the analysed data.
Table 5: Farm E - Milking hours
Day Milking hours (24hr) Duration (mins)
1
Morning milking was outside cycle
17:17 – 19:32
n/a
135
2
06:54 – 08:55
17:16 – 19:11
121
115
3
06:45 – 08:52
Evening milking was outside cycle
127
n/a
The duration of each milking during the cycle can be seen in the Table 5, with the
total time spent milking accumulating to 498 minutes. This figure can be used to
determine the volume of water used for pre-cooling during the cycle by the following
equation.

68. 55
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 (𝑙) = 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 (𝑙/𝑠) 𝑥 𝑇𝑖𝑚𝑒 𝑠𝑝𝑒𝑛𝑡 𝑚𝑖𝑙𝑘𝑖𝑛𝑔 (sec)
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 (𝑙) = 1.33𝑙/𝑠 𝑥 (498𝑥60)
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 (𝑙) = 39,740 litres
While the author was attaching the temperature sensors to the pre-coolers, a solenoid
was found on the GW inlet into the first PHE. This resulted in control over the
volume of GW entering and in fact makes the calculated volume required to be
incorrect. For the purpose of this research, the author will pursue and use the
calculated volume of GW required.
6.6.4 Parameter 4 – Milk & water temperature associated with PHE 02
Both the milk and water temperatures associated with the second PHE were recorded
in order to determine its effectiveness.
6.6.4.1 Milk Temperature
The following graph displays the variation of the milk temperature profile before and
after the second PHE for the duration of the cycle.
Figure 27: Farm E - Associated milk temperatures with second PHE
The milk outlet temperature from the second PHE seems to rise to over 35°C for a
period of time during the cycle. A peak just above 35°C doesn’t represent a system
wash as the temperature is too low. A possible cause of this peak can be turning off
the IB pump where CW cannot be circulated through the second PHE for the entirety
of the milking. The average milk inlet temperature was calculated to be 19.77°C
0
5
10
15
20
25
30
35
40
09:26
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
09:00
Temp.
(°C)
Time (24hr)
Milk Temp. In (°C) Milk Temp. Out (°C)

69. 56
while the average milk outlet temperature was calculated to be 7.98°C; refer to
Appendix L for relevant calculations.
6.6.4.2 Water Temperature
Due to the large amount of temperatures that needed to be monitored on this system,
the temperatures were recorded over a period of two cycles.
The following graph displays the variation of the water temperature before and after
the second PHE over the period of two consecutive cycles.
Figure 28: Farm E - Associated water temperatures with second PHE
Although it may be difficult to compare the temperature profiles, the average CW
inlet and outlet temperatures can still be calculated. In this case, the average CW
inlet temperature was 4.1°C while the average CW outlet temperature was 9.8°C;
calculations are available in Appendix L.
6.6.5 Parameter 5 – Power consumption of IB supplying CW to PHE 02
The power consumption of the IB generating ice for the CW in the second PHE
throughout the entire cycle was measured by the OWL meter. According to the
logged data received from the meter, the raw data amounted to 1,519.03kW. The
following graph illustrates the consumption profile during the cycle.
0
5
10
15
20
25
09:26
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
09:00
Temp.
(°C)
Time (24hr)
Chilled Water In (°C) Chilled Water Out (°C)

70. 57
Figure 29: Farm E - Power consumption profile IB feeding PHE during the cycle
To convert the raw data into the energy consumption (kWh) each individual reading
had to be divided by 1,000. The summation of these values represented the energy
consumed during the monitored cycle. The summation of the total ‘kW_Raw_Data’
divided by 1,000 yields the same result.
𝐶𝑜𝑛𝑣𝑒𝑟𝑡𝑒𝑑 𝐷𝑎𝑡𝑎 (𝑘𝑊ℎ) =
𝑆𝑢𝑚𝑚𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑡𝑜𝑡𝑎𝑙 𝑘𝑊_𝑅𝑎𝑤_𝐷𝑎𝑡𝑎
1,000
𝐶𝑜𝑛𝑣𝑒𝑟𝑡𝑒𝑑 𝐷𝑎𝑡𝑎 (𝑘𝑊ℎ) =
1,519𝑘𝑊
1,000
𝐸𝑛𝑒𝑟𝑔𝑦 (𝑘𝑊ℎ) = 1.52𝑘𝑊ℎ
0
0.5
1
1.5
2
2.5
09:26
12:00
18:00
00:00
06:00
12:00
18:00
00:00
06:00
09:00
Power
(kW)
Time (24hr)