Evaporative Cooling Device for an Air Cooled final

Daniel Jones ACS Device for an Air-Cooled Chiller Project 10
SET4A B.Eng (Hons) in Sustainable Energy Page 1
Evaporative Cooling Device for an Air Cooled
Chiller System (ACS Device)
Daniel Jones, Cork Institute of Technology, Cork, Ireland
2016 Semester 2 Project Number (10)
___________________________________________________________________________________________
Student Number: R00096168
Degree Programme: Sustainable Energy Engineering (BEng Honours degree) CR510
Module Code: MANU8005 Project – Realisation
Supervisor: Paul O’Sullivan
Assessor: Chris Gibbons
___________________________________________________________________________________________
Abstract
This paper has identified the problem of heat rejection from an air-cooled chiller system during times of high
ambient temperatures and looks at feasible solutions to overcoming this common problem. “Air-cooled heat
rejection systems (air cooled chillers) rely on the dry bulb temperature which is commonly between 5 and 15
°C higher than the wet bulb temperatures”. “Traditionally, large heat rejection systems like a chiller
generally use a cooling tower in order to reduce the heat rejection equipment size as well as the
overall energy consumption due to lower condensing temperature” [2]. But due to water corrosion, and
health risks such as Legionella disease t h i s h a s shifted industries towards less efficient dry heat
rejection systems like air-cooled chillers. By simply intermittently spraying water over a mesh surface, in front
of the heat rejection surface and against the direction of the air stream, this introduces a g r e a t e r wet bulb
temperature during peak high ambient air periods. This process known as evaporative cooling can be done by
simply introducing water into an air stream which rapidly evaporates and the hidden energy of water provides
a cooler down stream air temperature as much as 6 ~ 8 °C lower than the incoming air. This drop in air
temperature results in a lower condensing temperature and therefore can save as much as 10 to 15% of
power consumption by simply using water directly from the tap. Testing of this new concept device showed
between 10 – 15% electricity reductions during operation of the air-cooled chiller during high ambient air
temperatures. This report details the overall design of a new concept device from the initial brainstorming
behind the prototype design to the complete construction and installation of the device that will then be used for
experiments on an air cooled chiller in order to generate a series of results. These results will be compared
against that of a baseline test without the device. This report also contains the results of the numerous
experiments that were completed on the air-cooled chiller system in one of the labs located in college. By
completing these tests it allowed for the demonstration of the effectiveness of the device that is in question.
Finally this paper identifies the use of a Microsoft Excel driven selection-modelling tool. Which allows the user
to gain a greater overall understanding of the effectiveness of the device in terms of payback and performance.
Keywords
Air-cooled chiller, heat transfer, High ambient air temperature, Energy Saving, ACS Device.
___________________________________________________________________________________________
Declaration:

“This report is solely the work of Daniel Jones unless otherwise indicated and is submitted in partial fulfilment of
the degree of Bachelor of Engineering in Sustainable Energy Engineering. I understand that significant plagiarism,
as determined by the examiner, may result in the award of zero marks for the entire assignment. Anything taken
from or based upon the work of others has its source clearly and explicitly cited.”
Signature: Date:

Acknowledgements

First I would like to acknowledge my project supervisor, Paul O’ Sullivan who has guided me through this project
over the past 8 months and dedicated his time to helping me make this project a realisation. Also I would like to
thank my project assessor Chris Gibbons. I would also like to acknowledge the course coordinator, Kevin Davis,
for his help throughout the semester. Pat Mehigan and Noel Clarke from the Tyndall National Institute should also
be thanked. Next Andy Brown should also be widely acknowledged, for everything he has done in making this
project a realisation and continuously dedicating his time to helping me in what ever way he could. Finally I
would like to thank my uncle for the help he gave me in constructing the frame that was used for the experiments.
Table
of
Contents

Abstract...................................................................................................................................................................1
Declaration:.............................................................................................................................................................1
Acknowledgements.................................................................................................................................................2
1.0 Introduction & Background ..............................................................................................................................5
1.1 Aims and Objectives.........................................................................................................................................5
Physical ........................................................................................................................................................5
Educational ..................................................................................................................................................5
1.2 Project schedule semester two:.........................................................................................................................5
1.2 Summary of literature review: ..........................................................................................................................6
1.2.1 Background: ........................................................................................................................................6
1.2.2 Air Cooled Chiller System:..................................................................................................................6
1.2.3 Evaporative Cooling: ..........................................................................................................................6
2.0 Methodology........................................................................................................................................................7
2.1 Design process behind the final concept: .........................................................................................................7
2.1.1 Phase 1: Market Assessment & Competitive Analysis ........................................................................7
2.1.2 Fitness-to-standard (FTS) & New-Unique & Difficult (NUD) Requirements for project. .................7
2.1.3 Critical Product Design Specifications...............................................................................................8
2.2 Phase 2: Initial Brainstorming Method.............................................................................................................8
2.3 Phase 3: The First Alpha Design ......................................................................................................................9
2.4 Phase 4: Design evolution leading to the final prototype design......................................................................9
2.4.1 Prototype Frame: ..............................................................................................................................10
2.4.2 Prototype Spray system:....................................................................................................................10
2.4.3 Prototype Collection tray ..................................................................................................................10
2.4.4 Prototype Mesh..................................................................................................................................10
2.5 Phase 5:...........................................................................................................................................................11
2.5.1 Experimental set-up .....................................................................................................................................11
2.6 Excel selection tool.........................................................................................................................................12
3.0 Results................................................................................................................................................................13
3.1 Experimental Results ......................................................................................................................................13
3.2 Scenario one: baseline test..............................................................................................................................13
3.3 Scenario two: introduction of ACS Device ....................................................................................................15
3.4 Economic Analysis .........................................................................................................................................18
4.0 Analysis..............................................................................................................................................................19
4.1 Phase 1: Prototype Critique: ...........................................................................................................................19
4.1.1 Recommendation for further study....................................................................................................19
4.2 Phase 2: Comparison of two scenarios (with and without ACS Device) .......................................................20
4.2.1 Performance comparison review .................................................................................................................20
4.2.1.1 Recommendation for further study...................................................................................20
4.3 Phase 3: Cost Analysis review:.......................................................................................................................21
4.4 Critical Analysis of Project.............................................................................................................................21
4.4.1 Alternations to the proposed methodology........................................................................................21
4.4.2 Undetermined data:...........................................................................................................................22
5.0 Conclusion .........................................................................................................................................................22
5.1 Points for further discussion: ..........................................................................................................................23
6.0 Bibliography......................................................................................................................................................24

7.0 Appendix............................................................................................................................................................25
7.1 Mission statement ...........................................................................................................................................25
7.2 Market Survey:................................................................................................................................................25
7.3 Concept Classification tree .............................................................................................................................25
7.4.1 Frame design:...............................................................................................................................................26
7.4.2 Spray System design:...................................................................................................................................26
7.4.3 Mesh Design ................................................................................................................................................26
7.4.4 Hose design..................................................................................................................................................27
7.4.5 Collection tray design ..................................................................................................................................27

Table
of
Figures

Figure 1 Project schedule ...........................................................................................................................................5

Figure 2 Circulation pattern of rejected Air................................................................................................................6

Figure 3 Various phases involved in design process ..................................................................................................7

Figure 4 Phases 2 Initial Brainstorming .....................................................................................................................8

Figure 5 Phase 3 Generating Project Concept ............................................................................................................9

Figure 6 Phase 4 Selecting Product Concept..............................................................................................................9

Figure 7 CAD Drawing of Final Design & Assembled Final Design ........................................................................9

Figure 11 Steps involved to complete experimental set-up......................................................................................11

Figure 12 Construction of ACS Device....................................................................................................................11

Figure 13 various positions of data loggers & Voltmeter.........................................................................................12

Figure 14 Temperature of ambient air in 2014 (CIT weather station)......................................................................13

Figure 15 Temperature of lab over a 10-minute period............................................................................................13

Figure 16 Psychrometric Chart of Scenario one.......................................................................................................14

Figure 17 Return Temperature of space over a 5-minute period..............................................................................14

Figure 18 Temperature rejected from chiller over a 2-minute period. .....................................................................14

Figure 19 Psychrometric chart of Scenario two........................................................................................................15

Figure 21 Temperature of Air no mesh v mesh........................................................................................................16

Figure 22 Temperature before mesh and after mesh ................................................................................................16

Figure 23 Temperature of rejected air ......................................................................................................................16

Figure 24 Cooling Capacity......................................................................................................................................17

Figure 25 Power consumption ..................................................................................................................................17

Figure 26 Coefficient of Performance ......................................................................................................................17

Figure 27 Temperature of return water.....................................................................................................................18

Figure 28 Payback Period.........................................................................................................................................18

Figure 29 Phase one Performance review of Final Design.......................................................................................19

Figure 30 Phase two Comparison of gathered Results .............................................................................................19

Figure 31 Phase three Cost Analysis of Device........................................................................................................21

Figure 32 Phase four Critical Analysis of Project ....................................................................................................21

Figure 33 Concept classification tree........................................................................................................................25

Figure 34 Spray System Design (Brainstorming).....................................................................................................26

Figure 35 Mesh Design (Brainstorming)..................................................................................................................26

Figure 36 Hose Design (Brainstorming)...................................................................................................................27

Figure 37 Collection Tray Design (Brainstorming)..................................................................................................27

Table
of
Tables

Table 1: Nomenclature................................................................................................................................................4

Table 2: Fitness-to-standards Requirements...............................................................................................................8

Table 3: Design Specifications ...................................................................................................................................8

Table 4 Frame details & Figure 8 CAD Drawing of Frame .....................................................................................10

Table 5 Spray System Details & Figure 9 CAD Drawing of Spray System ............................................................10

Table 6 Mesh details & Figure 10 Mesh to be used .................................................................................................10

Table 7 Various Parameter in experiment ................................................................................................................11

Table 8 Various Parameters that have been monitored ............................................................................................13

Table 9 Various Parameters......................................................................................................................................15

Table 10 Temperature Comparisons.........................................................................................................................20

Table 11 Payback period...........................................................................................................................................21

Table 12:Mission Statement .....................................................................................................................................25

Table 13: Market Survey ..........................................................................................................................................25

Table 14: Frame brainstorming.................................................................................................................................26

Table 15: Mesh brainstorming..................................................................................................................................26

Table 16: Hose Brainstorming..................................................................................................................................27

Table 17: Collection tray brainstorming...................................................................................................................27

Table 1: Nomenclature
Nomenclature:
Symbol Description
Q Quantity of heat exchanged (btu/min)
W Flow rate of fluid (lb./min)
ΔT Temperature change of temp (˚C)
COP Coefficient of performance
AHU Air Handing Unit
SEU Significant Energy User
CHW Chilled Water
SP Set Point
Δp Pressure drop (pa)
Eu Useful energy acquired (btu)
Ea Energy Applied (btu)
BTU British Thermal Units
mh
Mass flow rate of the hot fluid (m/s)
Q Heat load (kW)
W Humidity ratio of moist air (kgw/kgda)
hw Specific enthalpy of condensed water
Cdd Cooling degree days
Tbase Base temperature (˚C)
LMTD Log mean temperature difference, °C
ACS Device Air Cooling System
U Overall heat transfer coefficient (W/m2
°C)

1.0
Introduction
&
Background

During my time working with the Tyndall National Institute, I was given the opportunity to base a lot of my time
identifying and working with the main SEU’s* onsite. After extensive work, it became prominently clear that the
chilled water process in the building accounted for a significant amount of energy usage onsite, especially during
times of high ambient air temperatures (mainly summer months). It can be said that “Air-cooled chillers are
commonly used to provide cooling in commercial buildings, but with considerable electricity consumption” [3].
According to the SEAI “cooling a building accounts for a significant amount of energy in most Irish industries,
where it can account for between 10% and 60% of the site’s electrical load” [4]. This figure varies according to
the time of the year, which is the main principle behind this project and will be continuously examined and
referred back to in this report.
This report outlines the realisation stage of this project, which will examine the feasibility of incorporating a new
add on retrofit device to an air cooled chiller system (ACS device) to assist the system in overcoming the process
of heat rejection, especially during times of high ambient air temperatures and fundamentally reducing the ambient
air temperature. Therefore allowing the device to be applied to certain areas where it can be utilised, thus saving
energy, emissions, and running costs. This will be discussed during the analysis stage of this report. This
report

consists
of
all
of
the
aspects
behind
the
design
including;
customer
and
engineering
requirements
and
the

performance
and
characteristic
criteria
required
will
be
assessed
to
produce
the
best
possible
device
that

meets
all
the
outlined
requirements. The main body of this report consists of the methodology implemented to
realise this project and a detailed analysis of the gathered results from the experiments that have been completed.
This report also contains a detailed product design method, which was completed to show the steps used to create
the product in question. Finally this report contains conclusions on the viability of the project in question, as well
as the execution of the project itself in relation to the completion of the objectives set forth in section 1.1 below.
1.1
Aims
and
Objectives

The aims and objectives set forth in this section are preliminary and may be subject to change as new
developments and ideas occur during the realisation of this project. The initial aims and objectives are as follows:
• Design the most beneficial solution in order to overcome high-energy consumption during times of high air
ambient temperatures, thus reducing energy consumption, CO2
emissions and the overall operating cost of a
chiller.
• To identify the most viable prototype to be used on the system, taking into account parameters including size,
conductivity of materials, weight of materials, shape of device, added or reduced pressure, connection points etc.
• Preform a series of experiments on the device that has been constructed to gain data and information on the
device’s performance in terms of: operational cost, temperature profile at various points and other key indicators.
• Present all findings in a detailed report examining all aspects carried out in finding a viable solution to problem.
The initial proposed deliverables of this project are as follows:
Physical

• A Microsoft Excel based theoretical energy modeling tool based on a device selection tool.
• A number of detailed experiments and results gathered from lab testing.
• Construction of a feasible prototype, which will meet the problems outlined in the literature review.
• A technical report on the feasibility and incorporation of an Evaporative-cooling device to aid with energy and
cost reduction.
Educational

These objectives have been met in semester one, with the completion of the literature review report.
1.2
Project
schedule
semester
two:

• Research behind project (Semester 1)
§ Concept evaluation & breakdown (Jan. 14th
)
§ Detailed Design analysis (Feb. 13th
)
§ Review of Detailed Design (March 5th
)
§ Generate concept (build) (March 10th
)
§ Set up experiment (March 15th
)
§ Prototyping and Testing (April 1st
)
§ Review & analysis test data (April 20th
)
Evaluation

Design

Analysis
Review

Generate

Concept

Set
up

experiment
Testing

Figure 1: project schedule

1.2
Summary
of
literature
review:

The literature review conducted in the research phase of this project addressed the following main subjects: The
operation of an air-cooled chiller system and the process of evaporative cooling, both of these topics are
fundamental in the overall execution of this project. The theory behind heat transfer and the fundamentals of the
refrigeration cycle will not be addressed in this summary, as it was only addressed in semester one in order to
provide a familiarity with thermodynamic operations in relation to chiller systems and how the unit operates.
1.2.1
Background:

During the literature review stage of this project, the problem of heat rejection in an air-cooled chiller system
during times of high ambient air temperature was identified. After careful consideration and countless hours of
research it soon became possible to identify a feasible solution to the problem observed, which involved the
development, and creation of a retrofit device that would simply be fitted to the exterior of the air-cooled chiller
system. Once knowledge of the operation of an air-cooled chiller and how the system operated throughout a 12-
month period was gained from the literature review stage, solutions were identified and then they were ranked on
their overall effectiveness in solving the problem in question. This lead to the possibility of incorporating the
process of evaporative cooling. In conclusion to the information that was gained in the literature review stage, it
was determined that by collaborating an air cooled chiller and the process of evaporative cooling together, the
solution to the problem faced may be established. Section 1.2.2 and 1.2.3 briefly outline the findings from the
literature review stage in relation to the operation of an air-cooled chiller and also the process of evaporative
cooling, both these topics are fundamental and act as the building blocks for this project.
1.2.2
Air
Cooled
Chiller
System:

The literature review conducted in semester one focused on the overall operations of an air-cooled chiller system.
Explaining exactly how the system absorbs the heat from the process of water being circulated around the
building. This absorbed heat is then released directly into the outside air, which surrounds the chiller system itself.
An air-cooled chiller uses the outside ambient air to cool the condensers inside. Air is allowed to enter the chiller
through a series of aerated fins, directing this in-take air into the system itself. “Air-cooled chillers do not require
a cooling tower and therefore are less costly to install and maintain” [5]. However, air cooled chillers are far less
energy efficient than water-cooled chillers. The heat being rejected from the condenser is mixed with the air
medium and forced out of the system via fans situated on the top or rear of the chiller unit.
1.2.3
Evaporative
Cooling:

The literature review stage identified the benefits of incorporating an evaporative cooling process. To recap on the
process, it can be said that when air comes in contact with water, some of the water evaporates to a gaseous state
in the air stream. This process removes heat from the air and adds heat to evaporated water. The overall rate of
evaporation varies with the saturation of the incoming air. The rate can be increased by spraying the water as a
fine mist to wet evaporative media that spreads the water over a large surface area. “Heat is removed from the air
stream and added to the water as it evaporates, thus lowering the dry bulb temperature of the air, which becomes
cool and moist” [6]. As shown in the Psychrometric chart in appendix A, this process starts with the conditions of
the incoming air, and moves up and to the left as the water evaporates. For example, if the external air is at 30°C
dry bulb and 18°C wet bulb that is evaporatively cooled to 25°C dry bulb would remain at 20°C wet bulb.
.

Figure 2 Circulation pattern of rejected Air

2.0
Methodology

The methodology of this project consists of three areas; first the various phases that ultimately led to the final
design and consequently the construction of the evaporative cooling device itself, secondly the experimental
collection of data from a series of experiments on the final design and finally the energy-modelling tool.
2.1
Design
process
behind
the
final
concept:

In order to meet objectives one and two that have been set forth for this project, a detailed analysis of the design
of the device to solve the identified problem encountered needed to be established. This would then allow for a
greater success rate when testing occurred, therefore reinforcing the objectives of this overall project. To do this,
the design stage was split into four phases plus a final testing phase, which can be seen in figure 3 below. The
following section discusses the comprehensive process that was carried out in coming up with the final design of
the evaporative cooling device, this includes; A market assessment to find the need, a competitive analysis to view
various competitors in the market, identify design and engineering specifications that need to be met, the initial
brainstorming ideas, the alpha model design and the project evolution that led to the final design of the device.
Figure 3 various phases involved in design process
2.1.1
Phase
1:
Market
Assessment
&
Competitive
Analysis

Phase one identifies the needs of the target market and assesses the market competitors. The general idea behind
the proposed device is for it to be a simple, easy to use and an effective mechanism. After gathering various data,
which included a market survey - which can be seen in appendix 7.2 - and from analysing the information,
gathered in the literature review, it was possible to determine the target market of this device, which was
extensive, ranging from small buildings to large commercial buildings. This allowed for the allocation of time to
focus on meeting the needs of that of a large energy consuming business. Once this was determined the following
question needed to be answered:
What is already on the market in terms of ways to lower the energy consumption in an Air-Cooled Chiller?
• Internal air wetting systems
• Combined hybrid systems (eco-tor)
• Pad-systems
Following extensive research and hours of searching through the Internet and books, it was clear to see that there
was a lack of products available on the market that were like the proposed ACS device. There were a few products
that showed similar characteristics but nothing in terms of design.
2.1.2
Fitness-‐to-‐standard
(FTS)
&
New-‐Unique
&
Difficult
(NUD)
Requirements
for
project.

The next step following on from the opportunity assessment is the formation of the various requirements that are
desired. The voice of the customer was developed from research into the market and also a customer survey. This
allowed the project to be defined in detailing the aspects of the product that are basic features of the design (FTS)
and, in addition, establishing some novelty characteristics that will attract the customers (NUD) to this device.
Fitness-to-standard
On the basis of similar products on the market, the fundamental demands for the device consist of the following:
o Concise design
o Performance enhancer
o Effective device
o Lengthy lifetime
o Inexpensive
o Simple-mechanism
New, Unique & Difficult
New: The proposed device is new on all fronts; it can be described as a “performance enhancer” which allows
multiple allocations of the product in many industrial departments. Other new attributes to the Product include:
o Designed to reduce air temperature.
o Designed to minimise energy consumption
during high ambient temps.
o Reduced running costs.
o Re-circulates water.
Phase
1:

Market

Assessment
&

Competitive

Analysis

Phase
2:
Initial

Braistorming
of

design

Phase
3:

Generate

Product

Concept

Phase
4:
Select

Product

Concept

Phase
5:
Test

Product

Unique: What makes this device unique is its ability to be an all in one system that can be attached and detached
very easily from the chiller. The device is cheap to produce and ultimately could save thousands of euros.
Difficult: The ACS device itself is a new product, which resolves the “Latent Problem”. A latent problem is a
problem that you do not know is there until you need it. In this case, the latent problem identified is the problem
of overcoming high-energy costs when operating during times of high ambient outside air temperature.
Requirements Type Weighting Factor
Performance enhancer NUD 35%
Concise design NUD 15%
Inexpensive FTS 20%
Material usage
Ease of use
FTS
FTS
15%
15%
Table 2: Fitness-to-standards Requirements
2.1.3
Critical
Product
Design
Specifications

Following on from the market assessment and the requirement importance ranking. The correlating of the
engineering specifications for these requirements was established by conducting extensive research and
continuous discussions with mentors and supervisors. The requirements identified will be continuously reviewed
throughout the design process, selection of alpha design, and the evolution of the project in order to meet the
needs identified for this device. In order to effectively design the required evaporative cooling device for an air-
cooled chiller, a wide-ranging list of performance expectations for the final product was produced. Based on
discussions with mentors in both college and during work placement regarding these requirements for the device,
in order to reduce energy consumption, and gaining a higher performance level it was possible to establish the
following list of specification, which are displayed in table 3 in order of importance from 5 (highest) to 1 (lowest).
Requirements Importance
(1 low, 5 high)
Engineering specifications
Robust 4 Downward Force (N)
Affordable 4 Manufacturing Cost (€)
Performance 5 Operation Cost (€)
Longevity 5 Service Lifetime (Years)
Easy to adjust 2 Adjustable Frame (m)
Lightweight 3 Weight (kg)
Table 3: Design Specifications
Figure 4 phases 2 Initial Brainstorming
2.2 Phase 2: Initial Brainstorming Method
Once the overall requirements, market needs and engineering specifications were established and inspected, it was
possible to begin the initial design phase in order to meet the series of objectives set forth for this project. There
were numerous steps and iterations to the design evolution of the proposed device in question. By utilizing a
brainstorming method it was extremely beneficial to the product development process of this project as it allowed
for the building blocks to be laid in relation to devising a suitable design to target the problem at hand. Using the
brainstorming method also made it possible to generate a series of ideas and compare each against the
requirements identified in section 2.1.2 in order to generate the solution for the problem faced. By using this
method it also allowed for an indication of possible risks that may have occurred throughout the project. Once the
best ideas where establish from using swot reports and other methods, it was possible to move onto the next stage
which involved the generation of the first Alpha design. The next stage of this report will look at the first design,
which was comprised of the best ideas generated during these brainstorming sessions. It can be said that the first
Alpha design will allow for further design evaluation, as problems will arise. Design generation began with a
design breakdown1
of the following components: frames, mesh, collection tank, spray system, hose, connections
and pumps. For each component, designs were generated2
and rated on their performance with the use of SWOT
reports, and then iterated based on mentor feedback. Through this process, a number of Alpha designs were
1
Refer to appendix 7.3 for design breakdown
2
Refer to appendix 7.4 for Initial Drawings
Phase
1:

Market

Assessment
&

Competitive

Analysis

Phase
2:
Initial

Brainstorming

of
Design

Phase
3:

Generate

Product

Concept

Phase
4:
Select

Product

Concept

Phase
5:
Test

Product

created, which will be discussed in section 2.3. In order to facilitate the manufacturing plan and to visualise the
current design challenges for the final prototype, mock-ups were produced.
Figure 5 Phase 3 Generating Project Concept
2.3
Phase
3:
The
First
Alpha
Design

The first alpha design consisted of the top-rated components from the initial functional breakdown and the various
SWOT analyses and TOWS analysis used in the brainstorming phase. The alpha model design consisted of a
frame that was made up of various length bamboo pipping that were put together and attached to the chiller. The
mesh was a basic blue fabric mesh used in building sites for covering fences. The mesh covered the exterior of the
frame and was connected to the various bamboo bars. The spray system was made up of a basic hose that was cut
into different lengths and numerous spray nozzles that would normally be used for garden maintenance. The spray
system was connected to the inner side of the frame using cable ties and masking tape and the water was feed to
the system via a tap and a hose, which measured over 8 meters in length. Once this alpha design was set up and
ran it was then re-evaluated and analysed to identify the critical areas for improvement and evolution. Also
engineering parameters and specifications were derived in order to progress to the initial fabrication of the final
prototype. Several areas were identified as possible failure locations once the alpha model was in operation and
were evaluated using engineering analysis to determine the likelihood of such failure. The alpha design will have
some functions and characteristics that will change with further design evaluation. Adjustments to the alpha
design were expected, especially as the project approaches the prototyping stage. The spray system will require
further design updates and analysis for circulating the water. (Refer to appendix for image of alpha design)

Figure 6 Phase 4 Selecting Product Concept
2.4
Phase
4:
Design
evolution
leading
to
the
final
prototype
design

There were many modifications to the design throughout the design and engineering process. Two of the main
influences that led to the re-design were in relation to materials and structure. As the device would be placed in a
hanging position from the exterior of the chiller unit, minimizing the overall weight of the device was priority.
Additionally, upon further consideration and discussion with my mentor, the use of a water collection system
needed to be incorporated into the design. The following section explains in detail the various components of the
final design accompanied with CAD Drawings, it also explains how each component relates to engineering and
performance requirements in section 2.1.2. Figure 7 below shows the final design for the evaporative cooling
device. The overall device meets the engineering requirements and specifications established for this project in
section 2.1.3.

Figure 7 CAD Drawing of Final Design & Assembled Final Design
Phase
1:

Market

Assessment
&

Competitive

Analysis

Phase
2:
Initial

Brainstorming

of
Design

Phase
3:

Generate

Product

Concept

Phase
4:
Select

Product

Concept

Phase
5:
Test

Product

Phase
1:

Market

Assessment
&

Competitive

Analysis

Phase
2:
Initial

Brainstorming

of
Design

Phase
3:

Generate

Product

Concept

Phase
4:
Select

Product

Concept

Phase
5:
Test

Product

2.4.1
Prototype
Frame:

The final design of the frame is illustrated below; the frame has an outer dimension of 1.1m long by 1.1m wide
and is made from lightweight reinforced steel. The main purpose of the frame is to provide the stability, strength
and structure that is required to support the mesh during the operation of the device. The mesh and spray system
will be supported on this frame. The four corners of the frame provide stability as they are connected to the chiller
system via copper hooks drilled into the chiller systems exterior. The crossbar is used to give the appropriate
angle, which will allow the spray system to cover the entire surface area of the mesh surrounding the frame. This
frame design meets the required design and engineering specifications laid out in section 2.1.2.
Table 4 Frame details & Figure 8 CAD Drawing of Frame
2.4.2
Prototype
Spray
system:

The fundamental purpose of the integrated spray system is to continuously spray a mist of water at the surface of
the mesh during peak ambient temperatures, thus giving the mesh a damp surface. The spray system itself is
connected to the rear of the frame parallel to the crossbar. The spray system is connected at one side to a hose,
which is recirculation the water collected in the tank below the device. The other side of the spray system has
been clamp welded together, therefore blocking the exiting of water.
Table 5 Spray System Details & Figure 9 CAD Drawing of Spray System

2.4.3
Prototype
Collection
tray

The purpose of the collection tray is to collect the excess water that passes through the mesh. The excess water in
the tray is then recirculated back around via a hose to the spray system. A hole of diameter 0.8 inches was made
on the side of the tray to allow for the connection of the hose to the spray system, once the hose was placed
through the hole on the tray, the hole was sealed using insulation so it would not leak during operation. The tray is
constructed from waste metal that was found within the college. The tray is approximately 1.3m wide and 25cm in
depth and 15cm in height and it simply slots in under the chiller as it has been designed around the chillers overall
size.
2.4.4
Prototype
Mesh

The purpose of the mesh was to act as a damp membrane. The mesh was cut to size (1.1m x1.1m) and then
secured to the face of the frame via cable ties. For the purpose of the experiments, different types of mesh were
used, each with different properties than the other. Therefore allowing for various series of data. The following
table identifies the properties of the mesh that will be tested.
Properties Mesh four
Material Nylon
Size 1.1m
Weight 0.12grams/m
Thickness 0.02mm
Table 6 Mesh details & Figure 10 Mesh to be used
Properties Details
Material Light weight steel
Size 1.1m x 1.1m
Weight 1.34kg
Thickness of steel 1.2cm
Properties Details
Material Copper
Size 1.1m x ½ inch
Weight 0.4kg
Thickness of steel 5 mm
Number of holes 6 x 4
110cm
110cm
80cm
45cm
45cm

Figure 10 Stage 5 Testing Prototype
2.5
Phase
5:

Phase 5 in the design aspect of the device leads on to the second of the stated methodology mentioned at the start
of this section, the experimental set up stage, which is discussed in the following section:
2.5.1
Experimental
Collection
of
Data

The experimental testing of this project took place in the south end of the B block in lab B234. The lab contains
numerous industrial devices to aid with student research. To complete the experiment and gain as much accurate
data as possible, the parameters outlined below had to be determined.
Parameter Instrument
External air temp before passing mesh (0
C) Temperature Probe
Air temperature of room (0
C) Data logger
Ambient temperature (0
C) CIT weather data
Entering & Exiting water temperature (0
C) Temperature probe
Temperature of rejected air (0
C) Data logger
Power Consumption (kW) Amp Meter
Table 7 Various Parameter in experiment
Figure 11 Steps involved to complete experimental set-up
The first step involved putting together the various components, which included the; frame, drip tray, mesh and
spray system. These were then attached to the air-cooled chiller via installed hooks in the unit. First the mesh was
connected to the frame using small 4-inch cable ties, once this was done the spray system was clipped into place
on the rear of the frame, using simple hooks that allowed for raising and lowering the spray system. Once this was
completed, the frame was attached to the chiller using hooks, as the frame itself was relatively light. After the
frame and various components were in place, the drip tray was simply placed underneath the frame (figure 12).
Figure 12 Construction of ACS Device
The second step was to place four different data loggers at four different points on the device, to measure a series
of focal points; the ambient air temperature of the lab at given intervals, the temperature of the air after it passed
through the mesh, the temperature of the rejected heat, the temperature of the air leaving the chiller, the entering
Phase
1:

Market

Assessment
&

Competitive

Analysis

Phase
2:
Initial

Brainstorming

of
Design

Phase
3:

Generate

Product

Concept

Phase
4:
Select

Product

Concept

Phase
5:
Test

Product

Step
1:

Assembly
devive
&

connect
to
chiller

Step
2:

Data
Logger

positions

Step
3:

Determine
position

of
spray

water temperature and finally the exit water temperature. This differs slightly from the proposed methodology set
forth in the semester one report, as time was limited and there was a restricted use of instruments, the pressure
changes and humidity changes will not be monitored in this experiment. The data loggers recorded temperatures
at thirty-second time interval, and were left in position for the duration of the experiments. The overall testing was
recreated in the lab, as it was not feasible to test the device outside due to the conditions and the time of the year.
In order to recreate the conditions needed the lab was significantly heated, creating a significant load in the room.
The first position records the outside air at ambient temperature. The data logger was fixed to the wall parallel to
the chiller system using simple cable ties. The reason why it was parallel to the chiller is so that it would not come
in contact with the water mist being used in the project. The position was chosen to determine the ambient air
temperature, which is necessary for the required calculation to determine if the ACS device is effective. This
temperature will be continuously varied throughout the experiment using the AHU, thus giving a varied output.
Figure 13 various positions of data loggers & Voltmeter
The second position records the temperature of the air after it has passed through the face of the mesh but just
before it meets with the heat exchanger on the face of the air-cooled chiller system. The data logger for this point
was also secured using cable ties but around the frame itself.
The third position records the heat being rejected from the system via the fans at the rear of the chiller unit. The
data logger for this point is located on the framework of the fan (figure 13) as it needs to record the temperature of
the heat rejected from the chiller unit. The fourth data logger was positioned on the return water piping at the rear
of the chiller to record the temperature of the water being returned to the space. This logger was a wrap around
device, which simply wrapped around the pipe.
The third step was to determine the position of the spray system, the spray system itself was interchangeable and
could be positioned either at the top of the frame or the bottom, this allowed for multiple analyses. The objective
was to entirely cover the outer mesh of the frame, thus giving the best possible accuracy when testing.
2.6
Excel
selection
tool

The energy-modelling tool for this project is a Microsoft Excel based tool, and instead of an energy
characteristics tool, this model will act as a selection tool to a user. The tool will consist of; a user-
friendly interactive interface and a series of selection tools allowing for performance criteria to be met.
As this tool incorporates a series of different parameters, there will be a series of scenarios to be
considered due to the variation of data that may be inputted into the tool. Each of these scenarios is
detailed below. In order to allow this model to be applied to different chiller systems, various options
will be incorporated into the selection tool to give maximum performance results for the user. The tool
incorporates slide-bar and button functions for each of the variables being measured. The selection tool
will analyse the energy usage of the system with and without the mesh, therefore giving the user a
better understanding if he/she will benefit in relation to energy savings (kw), savings during operation
(€) and a simple payback period for the device and installation. The energy tool will be simple and easy to
use thus allowing the user to easily operate the tool by simply changing the value of various inputs and the tool
will generate an output based on the input figures and the ACS device details.

3.0
Results

The following section of the report concentrates on the results gathered from the experimental stage,
which has been split into two scenarios, thus giving a realistic representation of the ACS device.
3.1
Experimental
Results

For the purpose of demonstrating the effectiveness of the ACS system, two scenarios of testing have been
introduced: testing the chiller without the ACS device and testing the chiller with the ACS device in operation.
The experiment was set up and tested in the energy lab in block A.
Figure 14 Temperature of ambient air in 2015
Figure 14 represents the ambient temperature profile of Cork in 2015; it is clear to see how the summer months
average between 15 to 170
C. By introducing the ACS device the ambient temperature experienced is reduced. This
will be discussed in section 3.3
3.2
Scenario
one:
baseline
test

Scenario one initially required the room parameters to be found, these parameters can be seen in table 8 below.
Parameters Temperature
Initial Room Temperature (0
C) 24.80
C
Temperate of air beyond mesh (0
C) OFF
Humidity (%) 38.8%
Entering temperature (0
C) 240
C
Exiting Water Temperature (0
C) 13.40
C
Table 8 Various Parameters that have been monitored
Scenario one involved testing the chiller without the ACS device in order to gain figures in which could be used
as a baseline for comparison with scenario 2. Figure 15 identifies the temperature of the room recorded over a 10-
minute period. It should be noted that the test was conducted on a significantly warm day, which is evident in
figure 15.
Figure 15 Temperature of lab over a 10-minute period.
0

5

10

15

20

Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Temperature
(0C)

Mesh
on
Vs
Mesh
off

Without
Mesh
With
Mesh

15

17

19

21

23

25

27

0
1
2
3
4
5
6
7
8
9

Temperature
(0C)

Time
(Mins)

Room
Temperature

To develop a greater understanding of the cooling needs and the properties of the initial air in the lab at the time of
testing, a Psyhcrometric chart was produced. Figure 16 visually represents the properties of the initial air in the lab
on the Psychrometric chart before the introduction of the ACS device. The initial temperature of the lab can be
seen as 24.8 degrees with an initial relative humidity rate of 39.8%.

Figure 16 Psychrometric Chart of Scenario one
The chiller unit was run and the results were gathered. Figure 17 visually represents the temperature profile of the
water temperature returning to the space from the air-cooled chiller over a period of 5 minutes.
Figure 17 Return Temperature of space over a 5-minute period.
Figure 18 represents the air that is being rejected over 2 and half minutes from the chiller without the ACS device.

Figure 18 Temperature rejected from chiller over a 2-minute period.
0

5

10

15

20

25

30

0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5

Temperature
(0C)

Time
(Mins)

Return
Water
Temperature

25

27

29

31

33

35

37

0
0.5
1
1.5
2

Temperature
(0C)

Time
(Mins)

Rejected
Air
Temperature

DB=24.80
C
39.8% RH
0.018 g/gWB= 15

3.3
Scenario
two:
introduction
of
ACS
Device

This scenario involved introducing the ACS device to the chiller system. Once again, the room parameters had to
be found and recorded, these parameters can be seen in table 9 below.
Parameters Temperature
Initial Room Temperature (0
C) 24.80
C
Temperate of air beyond mesh (0
C) 18.40
C
Humidity (%) 39.8%
Table 9 Various Parameters
Figure 19 below illustrates air passing through the face of the mesh; this process results in the process of heat
transfer and can be shown by the straight-line law [7]. This law states that when air is transferring heat to the
mesh, the condition of the air at point A, moves towards the saturation line at the temperature of mesh (18.40
C).
The condition of the air then leaves the wetted mesh at point B, where the dry bulb temperature has reduced and
the RH level has increased. The warm air of point A drops in temperature when in contact with TC at point C.
This process illustrates the activity of adiabatic saturation. To summarise, it can be seen from the Psychrometric
chart below that when the temperature of TA (24.80
C) passes through the saturation cover, the water on the mesh
is evaporated, so the air leaving the mesh has a temperature of TB (18.40
C).

Figure 19 Psychrometric chart of Scenario two
Figure 20 visually illustrate the temperature difference entering the chiller once the ACS system was turned on. It
is clear to see a significant temperature drop with the introduction of the ACS device.
Figure 20 Temperature profile no mesh v mesh
15

17

19

21

23

25

27

0
1
2
3
4
5
6
7
8
9

Temperature
(0C)

Time
Step
(mins)

Temperature
of
Air
before
&
after
Mesh

Series1
Series2

60C
Change

Before
ACS
Device

With
ACS
Device

A
B
TC TB TA
C

Figure 21 represents the dry bulb temperature as the ACS device is switched on and off simultaneously.
Figure 21 Temperature of Air no mesh v mesh
The overall temperature profiles of the ACS device intermittently turned on and off, graphed against the
temperature of the dry bulb temperature without the ACS device is illustrated in Figure 22.
Figure 22 Temperature before mesh and after mesh
Figure 23 represents the temperature profile of the rejected air temperature from the chiller with the ACS device
on and also without it on.
Figure 23 Temperature of rejected air
10

12

14

16

18

20

22

24

26

28

0
10
20
30
40
50
60
70
80
90

Temperature
(0C)

Time
(mins)

Temperature
of
Air
With
&
Without
Mesh

Mesh
ON
Mesh
OFF

Mesh
ON

15

17

19

21

23

25

27

0
10
20
30
40
50
60
70
80
90

Temperature
(0C)

Temperature
of
Air
Before
and
After
Mesh

Room
On/Off

Mesh
ON
Mesh
OFF
Mesh
ON

60C

6oC

Before
ACS

24

26

28

30

32

34

36

38

0
5
10
15
20

Temperature
(0C)

Time
(seconds
x
10)

Temperature
of
Rejected
Air

mesh
No
mesh

6-‐7oC

Figure 24 illustrates the change in cooling capacity with and without the ACS device in place.
Figure 24 Cooling Capacity
Figure 25 represents the power consumption as the temperature is decreased.
Figure 25 Power consumption
Figure 26 represents the change in COP of the test chiller system with and without the ACS device in place.
Figure 26 Coefficient of Performance
1.1

1.2

1.3

1.4

1.5

1.6

1.7

10
15
20
25
30
35
40

Cooling
Capacity
kW

Inlet
Air
Temperature
(oC)

Cooling
Capacity
(kW)

Without
Mesh

With
Mesh

0.3

0.35

0.4

0.45

0.5

0.55

0.6

10
15
20
25
30
35
40

Power
Consumption
kW

Inlet
Air
Temperature
(0C)

Power
Consumption
(kW)

Without
Mesh

With
Mesh

1

1.5

2

2.5

3

3.5

4

4.5

10
15
20
25
30
35
40

Coeffecient
of
Performance

Inlet
Air
Temperature
(0C)

COP

Without
Mesh

With
Mesh

Figure 27 represents the temperature returning to the space from the chiller unit with and without the ACS device
in operation.

Figure 27 Temperature of return water
3.4
Economic
Analysis

The simple payback period was calculated under a series of conditions: the first is an initial investment of just
under €200, which is a general assumption (which will be discussed in section 4.3) as most of the products were
sourced, constructed and installed on-site. The second condition is in relation to maintenance costs, which can be
assumed as zero due to simplicity of the ACS device. The final condition is that the price of electricity remains
static at 0.16c/kWh. Figure 28 illustrates the cumulative savings provided by the installation of the ACS device,
over the period of 22 weeks. Note: Once the points move above the negative line a profit is being made.
Figure 28 Payback Period
The installation of the ACS device 3
would save approximately €580 in 4 months, the payback was reached in just
over 8 weeks depending on the ambient air temperature. After the twenty year lifespan of the device over a twenty
year cooling period, the total cumulative savings (NPV) would equal just over €9,600.

3
ACS Device – Air Cooling System Device
10

12

14

16

18

20

22

24

26

0
5
10
15
20
25
30
35
40
45
50

Temperature
(0C)

Temperature
of
Supply
Water

Return

Return
(mesh
on)

2
-‐
3oC

-‐€220.00

-‐€120.00

-‐€20.00

€80.00

€180.00

€280.00

€380.00

€480.00

€580.00

€680.00

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22

Cost
€

Time
(Wks)

Payback
Period

4.0
Analysis

This section of the report is made up of four sub-sections; a detailed review and breakdown of the final design of
the ACS device in terms of materials and construction methods, a comparison of generated results with and
without the ACS device, a detailed cost analysis of the ACS device and finally a critical analysis of the
completion of this project.

Figure 29 Phase one Performance review of Final Design
4.1
Phase
1:
Prototype
Critique:

After testing and reviewing the final design, it quickly became evident that a few areas of the ACS device needed
further analysis and improvements in order to call the device a complete success. While I do believe that the
overall design of the device was moderately good, the following aspects have been identified as focal points for
design consideration if this topic was to be further looked at.
§ Collection tray:
The overall design of the tray was how I expected, but the material that was used was very basic, thus
once the tray was completely filled with water it began to seep from the corners, this was corrected but
could have been avoided if the tray had been made of better materials. It was also clear to see if the water
was left over night in the tray, the following morning it would be contaminated with rust from the tray.
§ Spray system:
Once the device was up and running, it was clear to see that the water pressure was dropping
significantly as it passed from one end of the spray system to the other. After careful consideration it was
decided on that a new spray system would be designed. This design was not very different from the final
design but a header was introduced to the centre of the system, which allowed the water to circulate
easier.
§ Mesh:
Only one variation of mesh was tested, therefore only demonstrating how the chosen one performed.
There are hundreds of different mesh variations on the market. Therefore it can be questioned that there
is a different mesh on the market that wasn’t tested that could possibly perform at a much higher level.
Also the mesh that was purchased came in sections of 1mx0.66m, therefore the mesh had to be connected
together to fit the face of the frame. This may have lead to less accurate results.
§ Recirculated Water:
One of the most significant problems that arose during the testing of the device was due to the
recirculating of the water. As the water that was being recirculated was the same constant supply, it soon
began to heat up to room temperature after being recirculated a number of times. This may have had a
significant effect on the results gathered from the experiments.
4.1.1
Recommendation
for
further
study

To provide better, more accurate results, the materials used should be manufactured to a higher standard than that
of the materials used during the experiment stage as problems occurred. More time may be needed to find the
most suitable materials and allow for manufacturing of the device. Also, a review should be undertaken to
examine the recirculation of the water with the possibility of introducing a cooling mechanism to cool the water
during recirculation as problems arose as the water temperature increased after continuous recirculation, therefore
the results gained could have been even more superior if a cooling method was introduced to the system.
Figure 30 Phase two Comparison of gathered Results
Phase
1:

Device

Performance

review

Phase
2:

Comparison

of
results.

Phase
3:
Cost

analysis

Phase
4:

Analysis
of

completion

of
project

Phase
1:

Device

Performance

review

Phase
2:

Comparison

of
results.

Phase
3:
Cost

analysis

Phase
4:

Analysis
of

completion

of
project

4.2
Phase
2:
Comparison
of
two
scenarios
(with
and
without
ACS
Device)

The following section will compare the results from section 3 of this report from the testing of the chiller with and
without the ACS device, and then compared under the following headings; temperature change comparison,
energy usage, economic breakdown and overall performance.
4.2.1
Performance
comparison
review

The table below represents the overall operating performance of the chiller plant with the ACS device on and
without the ACS device in place; this information is a summary of the results obtained in section 3.0.
Criteria Without mesh With mesh
Temperature entering (0
C) 23.80
C 18.40
C
Temperature of Rejected Air 35.50
C 32.30
C
Temperature of Return Water 13.40
C 12.30
C
Coefficient of Performance 2.9 3.5
Table 10 Temperature Comparisons
It can been seen from table 10 above that the temperature profile of the chiller unit without the ACS device
(Scenario one) is much higher than that of the system incorporated with the ACS device (scenario two). It can be
concluded from the results obtained that the introduction of the ACS device significantly reduces the temperature
in three different areas.
Reduction one: It can been seen from the experiments conducted on the system that the temperature of the air
coming in contact with the heat exchanger of the air-cooled chiller unit was significantly reduced with the ACS
device in place when compared with scenario one, it can be seen in the results section and table 10 above that this
reduction is just over 5 degrees. This figure represents the overall effectiveness of the device in terms of cooling
the outside air.
Reduction two: Secondly it is clear to see that the temperature of the rejected air from the chiller unit has been
reduced by just over 3 degrees when the ACS device was attached to the chiller and in operation. This indicates a
reduction in operation costs, as the compressor does not need to work as hard to pull the heat from the air and
force the heat out of the unit. It can also be said that the compressor was not working as hard to reject this heat
with the ACS device in place, as only one fan was in operation during the time the tests were conducted on the
system, therefore the compressor life should be increased dramatically.
Reduction three: Finally, it is clear to see from the gathered results obtained from the experiments, that the
temperature of the water returning to the space from the air cooled chiller unit has decreased by a little over 1
degree with the ACS device in place when compared against the data of the chiller without the device. It can also
be seen from the graph that the time taken to cool this water is significantly reduced with the inclusion of the ACS
device to the chiller unit.
Figure 25 in results section 3 represents the result of the air inlet temperature on the power consumption for
altered evaporator inlet air temperatures. It can be seen from the graph that the power consumed was reduced with
the reduction in temperature. The power consumption is decreased by 8% by changing the simply reducing the
temperature from 24.8o
C to 18.4o
C. Figure 26 represents the effect of condenser inlet air temperature on the air-
cooled chillers COP at various temperatures. The systems COP was improved by just over 9% by reducing the air
temperature entering the condenser from 24.8o
C to 18.4o
C. Finally figure 27 shows the decrease in temperature
being rejected from the system when the ACS system was introduced to the chiller. A 2-3o
C temperature decrease
was observed when the temperature of the ambient are was reduced from 24.8o
C to 18.4o
C.
4.2.1.1
Recommendation
for
further
study

In order to gain a greater understanding of the overall energy consumption (kW) it would have been much easier
to monitor the consumption of energy, if the chiller unit itself had been tracked using a monitoring system which
may be a BMS4
system or similar. This would have given a very accurate indication of exactly how much energy
was being consumed at various intervals of operation. Also another method of monitoring the energy performance
that would have benefited and also reduced the overall time period would have been the inclusion of an energy
tracker. This device could have been connected to the electrical distribution board and would have allowed for an
extremely accurate reading of electricity usage at close intervals and would have allowed for the generation of
performance and usage graphs in terms of energy consumption.
4
BMS – Building Monitoring System

Figure 31 Phase three Cost Analysis of Device
4.3
Phase
3:
Cost
Analysis
review:

The economic analysis conducted for th
is project is based on two main assumptions; there is no further investment in the device and secondly there is a
static energy cost for the fuel in use in CIT. These assumptions have been made due to their parameters, which are
extremely dependant on external drivers, which not be determined. In terms of the second assumption, the cost of
the electricity was assumed to be static due to the fact that the rate of per kWh varied considerably.
As previously mentioned in the results section, the initial investment that was made on all components in relation
to this project was just under €200. The following table breaks down the overall cost into the various components.
DESCRIPTION AMOUNT
Frame
Cooper Pipes
Mesh
Materials for tray
Plastic piping
Connection points
1 150.00€
1/2” by 3m 28.00€
1 6.99€
8kg 4.80€
1m 3.99€
2 5.98€
Total €199.76
Table 11 Payback period.
The initial investment in this project can vary considerably depending on the materials that may be used. For this
project, cheap scale materials were used therefore the payback period is extremely fast and demonstrates an
effective device, but if the overall initial investment in the device were higher due to expensive material the
payback period would be much longer. As this is a new device it was very hard to look into the future in terms of
maintenance costs. If the time frame for this project was expanded it may have been possible to calculate
maintenance costs or if there were any needed over the lifespan of the device.
Figure 32 Phase four Critical Analysis of Project
4.4
Critical
Analysis
of
Project

The critical analysis of this report will review two areas: alterations to proposed methodologies in semester one
and also the undetermined data in this report.
4.4.1
Alternations
to
the
proposed
methodology

There were many alterations to the proposed methodology set forth in semester one, due to the availability of new
information and ideas. The first alteration came in the form of the elimination of the degree-day analysis. In
semester one it was put forward that a degree-day analysis would be conducted to determine the cooling
requirements, based on the comparison of monthly mean temperature data. It became relatively clear that using a
degree-day comparison method would not benefit the project, as the device is a product that could be fitted to a
generic chiller system and also the time frame in which this project was based on did not make it beneficial to do
this. Instead this analysis was replaced with a more detailed comparison method, which consisted of the
psychrometric charts and both an energy consumption and cost analysis of various scenarios this allowed for a
better identification of overall performance of the ACS device.
Phase
1:

Device

Performance

review

Phase
2:

Comparison

of
results.

Phase
3:
Cost

analysis

Phase
4:

Analysis
of

completion

of
project

Phase
1:

Device

Performance

review

Phase
2:

Comparison

of
results.

Phase
3:
Cost

analysis

Phase
4:

Critical

Analysis
of

project

The second alteration was the elimination of a regression analysis comparison method. Using a regression model
works well if comparing a large amount of data over a series of years, but for this project data was only recorded
over a few days, due to the given time frame for completion. Although a lot of data was recorded, as there were
three different scenarios, it was still concluded that it would not be beneficial to conduct a regression model
comparison method for this project.
The third alteration or inclusion to this report involved the introduction of a product design method. By
introducing this method to the development of the device it allowed for a more detailed and informative result in
generating the final design. To do this it was best to introduce a system that used a series of phases that help lead
into the final phase which was testing the device. By introducing this method I felt the report and overall project
was a lot more structured and allowed the user to gain an in-depth knowledge of exactly how the final design for
the device was found.
In terms of the collection of experimental data, there were three alterations to the proposed methodology: the
recording of the energy usage using a voltmeter, the introduction of two temperature probes at the intake water
and exit water to monitor and record the water temp, also the water being recirculated was monitored using
another temperature probe. With further discussions with mentors and supervisors, it was determined that it would
be beneficial in proving the ACS system was working by recording the energy being using by the compressor
during operation. By simply connecting a voltmeter it was possible to monitor the usage at given intervals.
After deliberation with mentors, it was also decided that the intake and exit water temperatures needed to be
found, this was done by placing a wrap around temperature probe on the intake water pipe and also another of the
exit pipe. These temperatures were of interest, as we believed the exit temperature might have decreased due to
the installation of the ACS device.
4.4.2
Undetermined
data:

The project itself examines the effect of heat rejection from an air-cooled chiller during periods of high ambient
air temperature and how much it costs to carry out this process. Therefore the generated data in the results stage
was made up of only temperature and cost data. This project however did not take into account the RH %
contained in the surrounding air. To incorporate this into the project, the moisture content of the air outside the
system would have to be recorded for each temperature step, to do this a separate RH probe would have to be
attached to the frame to record. The reason why this type of recording was excluded from the testing is due to the
lack of instruments that could measure the moisture content of the air in conjuction with the temperature data
recorded by the data loggers. Also, another factor that affected this reading was the overall time frame in which
this project had to be completed.
Also the project itself does not examine the change in pressure within the air-cooled chiller. The main reason for
this was also due to the lack of instruments available. In order to measure the pressure of the system a separate
instrument would need to be installed into the chiller to monitor the pressure changes, as the test chiller was a
relatively small device and unlike an industrial sized chiller a build in recording device was not present to allow
for a visual inspection of the chillers performance at any given interval. The pressure of the chiller may have been
slightly altered due to the fact that the mesh covered the heat exchanger, which may have affected the pressure
reading within.
Finally the project did not measure or monitor the speed of the fans incorporated into the air-cooled chiller, which
are used to reject the heat. The more heat that needs to be rejected the faster the fans work. It may have been very
beneficial to monitor this, as the ACS system would, in theory, reduce the overall speed of these fans due to the
ambient air temperature being minimised by the effect of the ACS device. But this cannot be guaranteed, as it was
not monitored.

5.0
Conclusion

The success of this project is determined by the completion of the four main objectives which were set forth in the
introduction. In turn, the completion of these objectives can then be determined by the production of the expected
deliverables. Based on the definition of success, this project is deemed to be extremely successful. The first
objective was to design the most beneficial solution to overcome high-energy consumption during times of high
ambient temperatures, thus reducing energy consumption. This was broken up into two elements: The first was the
Alpha, which allowed for evolution of the final prototype this can be seen in section 2.2.1, while the second
element was a development of the first and this could be deemed a success, based on the recorded results gathered
from the experiments and also the construction of the device. The second objective was to identify the most viable

prototype to be used on the system, taking into account parameters including size, conductivity of materials,
weight of materials, shape of device, added or reduced pressure, connection points etc. This corresponds to the
first objective but goes that extra step; this objective can also be seen as a huge success, which can be seen in
section 3.0. The third objective was to perform a series of experiments on the device that has been constructed to
gain data and information on the device’s performance in terms of: operational cost, temperature profile at various
points and other key indicators. This objective was met in the results section and it can be concluded that the
experiments on the device were extremely successful. The final objective was to present the findings from the
experiment this was done in the analysis section of this report 4.0. Therefore to conclude, it can be said that this
project was a great success and met all the objectives set out in section 1.1 of this report.
5.1
Points
for
further
discussion:

Some of the main discussion points for this report have been addressed below:
The overall final design of the product has been designed to meet both customer and engineering requirements
and specifications to meet the objectives set forth at the start of this project. But I do believe if given more time to
conduct this project the overall characteristics of the final design could have been built and manufactured to a
higher standard, which include different materials and mesh, these may have enhanced the overall results and
performance that was recorded from testing the device.
The accuracy of the energy-modelling tool could be improved for future studies that may take place in relation to
this device. Extra data including pressure changes and water temperature may be needed to allow for a more
detailed analysis of the device’s performance on an air cooled chiller. By expanding the energy tool it would
allow the user to gain a clearer picture of the overall performance of the device, taking into account even more
parameters. The energy modelling tool constructed for this project identified the payback period, energy
consumption and change in COP with the introduction of the ACS device. The overall accuracy of the energy-
modelling tool could have been improved for future studies that may take place on this topic. In terms of energy
consumption, the inclusion of several different air-cooled chiller units could be included. This would require extra
work in gathering the needed data, but expanding the scope would lead to a clearer picture of how each system
benefits from the introduction of the ACS device.
The overall testing environment could be improved if further studies were to be conducted on the device. The
environment, which was used, was that of an artificial test bed, the lab was not allowed to act in a normal way; the
temperature was manually changed rather than allowed to change due to external losses and gains. Therefore it
can be said that this environment that was used to test the device was not natural and this may have affected the
overall performance and output of the device. Thus I would recommended that if further study was to be
conducted on the device it would be beneficial to test the device in a natural environment that takes into account
the daily changes of an industrial building.
In conclusion, the utilization of the ACS device has great potential and should be seriously considered for air
cooled chillers in the future as it can be said from tests that the ACS device will save users energy, costs and CO2
emissions during times of operation in high ambient air temperatures. This project has met all outlined objectives
set forth in section 1.1 of this report, thus can be deemed a success. The cooling effect & energy saving from the
ACS device may be better if the chiller was operated in a hot and dry environment. The outcomes from this
project provided an indication on how the ACS device can be used as an evaporative pre-cooler to increase the
chiller systems efficiency under various temperature situations. After testing the ACS device and reviewing the
results gained, it can now be concluded that:
§ The air entering the system was significantly reduced due to the cooling effect of the ACS device. This
was evident in the 6-7 degree temperature reduction of the air temperature.
§ The overall power consumed of the compressor was reduced by just over 8% by reducing the air
temperature entering the system from 24.8o
C - 18.4o
C.
§ The COP5
of the test chiller was improved by just over 9%, by simply reducing the temperature of the air
entering into the chiller system from 24.8o
C - 18.4o
C.
§ The rejected air temperature was reduced by 2-3 degrees with the introduction of the ACS device.
5
COP- Coefficient of Performance

6.0 Bibliography
[1] Cork Institute of Technology, "Weather Data," , Cork, 2014.
[2] Techoeps. (2013, March) Techoeps. [Online]. http://www.techoeps.com/Chiller.html
[3] F.W.H.Yik, "Predicting air-conditioning energy consumption of a group of buildings using different heat
rejectin methods," Energy and Buildings, 2001.
[4] SEAI, "Reducing Energy Use in Large Scale Refrigeration," Heat Transfer Fundimental, vol. 4, pp. 02-04,
March 2009.
[5] Berg, "What is a chiller? The principle of Basic Refrigeration," Introduction to basic refrigeration, vol. 4, no.
2, pp. 2177-2187, June 2010.
[6] Xiaohua Liu, "Temperature and humidity independent control of air-conditioning unit," Department of
Building Science , Tsinghua University, Beijing, 2013.
[8] (2010, April) Engineering Toolbox. [Online]. http://www.engineeringtoolbox.com/chilled-water-d 955.html
[7] Cibse. (2010, July) Cibse Journal. [Online]. www.cibsejournal/cpd/modules/2010-07/
[9] Dschool. (2011) Stanford. [Online]. https://dschool.stanford.edu/sandbox/groups/dstudio/Brainstorming-
Method.pdf
[10] Alexandra Iaccarino. (2013, October) Wordpress. [Online].
http://alexandraiaccarino.wordpress.com/2013/10/17/human-adapation-between-body-and-structure/
[11] J.Jahanbani, "A novel approach for optimal chiller loading using particle swarm," Energy and buildings, vol.
40, pp. 2177-2187, 2008.
[12] Jeff Miller, "God of Thermodynamics," A Mechanical Engineers Perspective, March 2002.
[13] M.Pfeifer, "The Materials Engineering Perspectice," no. 2, pp. 32-34, April 2004.
[14] R.Ramakrishnan, "Thermal Performance Investigtion of Mechanicl Cooling tower using Psychrometric
technique," pp. 1344-1353, December 2013.
[15] A.Bhatia, "Principles of Evaporative cooling," vol. 2, pp. 04-12, May 2012.
[16] Nick Rubis, "Engineering Design Report," Mechanical, Univercity of Michigan, 2009.
[18] Israel Urieli, "Psychrometrics Chart and Air Conditioning Process," Building and Energy, University of
Ohio, Ohio, PhD 1994.
[17] K.Smith, "Evaporative Cooling using Psychromric Charts," Mechanical , Univercity of Leeds, 2013.
[19] G.Godwin, "Psychrometry and Calculations of Air Conditioning Design," vol. 05, no. 2, pp. 12-17, 1998.
[20] Rapid-Tables. (2016) Rapid Tables. [Online]. http://rapidtables.com/calc/electric/energy-consumption-
calculator.htm
[21] Tgdl Part L, "Building Regulations 2011," Enviornment, Community and Local Government, 2011.
[22] Western Cooling Efficiency Center, "Building Energy Efficiency Consortium," Tsinghua University, China,
2014.
[23] Vishnu Manimaran, "Performance evaluation of an air-cooled screw chiller at low part ratios and outdoor
temperatures in Dubai & measure to improve the performance," Heriot Watt University Dubai U.A.E, Dubai,
2014.

7.0
Appendix

7.1
Mission
statement

Mission Statement: Evaporative cooling device
Product Description • A add on device for an air-cooled chiller.
Benefit Proposition • Reduces energy consumption, cost and CO2
production during high ambient temperatures.
Primary Market • Large Commercial buildings that need
refrigeration units.
Secondary Market • Small domestic buildings using small-scale
air-cooled chillers.
Assumptions • Easy construction
• Performance enhancer
• Durable
Table 12:Mission Statement
7.2
Market
Survey:

Evaporative Cooling Device
Please indicate on a scale of 1 to 5 how important the following features are to you in relation to the device.
Please use the following scale:
1. Feature is undesirable. I would not consider a product with this feature.
2. Feature is not important, but I would not mind having it.
3. Feature would be nice to have, but is not necessary.
4. Feature is highly desirable, but I would consider a product without it.
5. Feature is critical. I would not consider a product without this feature.
Importance of each: Place a tick in the box if unique.
On a scale of 1 to 5
_______ The device can be adjusted to fit various chiller makes.
_______ The device can be easily attached and detached.
_______ The device Price.
_______ Adding of a pump to recirculate water
Table 13: Market Survey
7.3 Concept Classification tree
Figure 33 Concept classification tree
Device

Frame

Plastic

Metal

Wood

Piping

Copper

Plastic

Cover

Mesh

Plastic

Metal

Fabric

Water

System

Pipe

Spray

7.4.1 Frame design:
Figure 31 shows the three different frame designs generated during the brainstorming session. Figure 1 is
rectangle design that would sit over the chiller. Figure 2 is a circular design while design 3 is a triangular shape.
Selection
Criteria
Frame
A
Frame
B
Frame
C
Ease of use
Durability
Weight
Shape
Attachment
+
+
-
-
0
+
0
+
-
0
0
+
+
+
+
Sum +’s
Sum 0’s
Sum –‘s
2
1
2
2
2
1
4
1
0
Net score
Rank
Continue?
0
3
No
1
2
No
4
1
Yes
Table 14: Frame brainstorming
7.4.2
Spray
System
design:

Figure 32 represents the three different spray system designs. Figure 1 is the device on the top of a cleaning bottle,
which can be found in any supermarket, Figure 5 is an average hose nozzle, while figure 6 is a more complex
spray bar with a number of holes positioned across it.
Figure 34 Spray System Design (Brainstorming)
7.4.3
Mesh
Design

Figure 33 represents the different mesh designs that were created during the brainstorming sessions. The first
shows tight aligned mesh. The second shows a diagonal style mesh design while third shows a more spread out
mesh.
Selection Criteria Mesh A Mesh B Mesh C
Ease of use
Durability
Movement
+
0
0
+
0
+
-
+
-
Sum +’s
Sum 0’s
Sum –‘s
1
2
0
2
1
0
1
0
2
Net score
Rank
Continue?
1
2
No
2
1
Yes
-1
3
No
Table 15: Mesh brainstorming

Figure 35 Mesh Design (Brainstorming)

7.4.4
Hose
design

Figure 34 represents the hose design
Selection Criteria
Hose
A
Hose
B
Ease of use
Durability
Flexibility
Shape
Connection
+
0
+
+
+
+
0
+
0
_
Sum +’s
Sum 0’s
Sum –‘s
4
1
0
2
2
1
Net score
Rank
Continue?
4
1
Yes
1
2
No
Table 16: Hose Brainstorming
Figure 36 Hose Design (Brainstorming)
7.4.5
Collection
tray
design

Figure 35 represents two different collection tray designs. Figure 12 is a half circle shape design. Figure 13 is a
basic rectangular design.
Selection
Criteria
Tray
A
Tray
B
Tray
C
Ease of use
Durability
Movement
Shape
+
0
0
-
+
0
+
+
-
+
-
0
Sum +’s
Sum 0’s
Sum –‘s
1
2
1
3
1
0
1
1
2
Net score
Rank
Continue?
0
2
No
3
1
Yes
-1
3
No
Table 17: Collection tray brainstorming
Figure 37 Collection Tray Design (Brainstorming)

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