Waste heat recovery systems from domestic refrigerator ..........

1. WASTE HEAT RECOVERY SYSTEM
FROM DOMESTIC REFRIGERATOR
BY: GROUP-II
FINAL YEAR
MECHANICAL DEPARTMENT
U.I.E.T C.S.J.M UNIVERSITY
KANPUR
PROJECT INCHARGE
Er. Arpit Srivastava
Dept. of Mechanical Engineering
UIET CSJM University
Kanpur

3. CONTENTS
 Introduction
 Different recovery systems
 System Description
 Design of Heat Exchanger
 Design Of Oven
 Fabrication And Assembly Works
 Results
 Conclusion

4. INTRODUCTION
• In domestic refrigerator a
part of heat gets wasted out
from condenser
• Wasted heat can be utilized
• system is technically
feasible and economically
viable
Fig 1

5. DIFFERENT HEAT RECOVERY SYSTEM
• HRSG in gas power plant or turbine
• HVAC in steam power plant
• WHRS in refrigeration plant

6. SYSTEM DESCRIPTION
• Tested a WHRS and experimented to recover
condensation heat from domestic refrigerator
of 165 liter.
• By suitably retrofitting the WHRS in the unit ,
considerable waste heat is recovered.
• This heat is utilized for different purposes

7. SYSTEM DESCRIPTION
•SECTION “A”- HEAT
EXCHANGER.
•SECTION “B”- OVEN.
•SECTION “C”- PIPE
Fig 2

8. HEAT EXCHANGER
 A heat exchanger is a device used to transfer heat between
one or more fluids. The fluids may be separated by a solid
wall to prevent mixing or they may be in direct contact.
 They are widely used in space heating, refrigeration, air
conditioning, power stations, chemical plants,
petrochemical plants, petroleum refineries, natural-gas
processing, and sewage treatment.
Fig 3

9. CLASSIFICATION OF HEAT
EXCHANGER
 Classification-
On the basis of flow
(a) Parallel flow (b) Counter flow
Fig 4

10. WHY COUNTER FLOW IN WHRS?
The counter-flow heat exchanger has three significant advantages over the
parallel flow design:-
 The more uniform temperature difference between the two fluids
minimizes the thermal stresses throughout the exchanger.
 The outlet temperature of the cold fluid can approach the highest
temperature of the hot fluid.
 The more uniform temperature difference produces a more uniform rate of
heat transfer throughout the heat exchanger.

11. DESIGN OF HEAT EXCHANGER
Applying heat transfer equation
heat transfer(1-2)= heat transfer(1-3)
45 − 40
ln
𝑟2
𝑟1
2𝜋𝑘 𝑟𝑒𝑓 𝑙
= ((45 − 30)/[
ln
𝑟2
𝑟1
2𝜋𝑘 𝑟𝑒𝑓 𝑙
+
ln
𝑟3
𝑟2
2𝜋𝑘 𝑡ℎ𝑒𝑟𝑚𝑎𝑐𝑜𝑙 ∗ 𝑙
+(1/(ℎ 𝑎𝑖𝑟2𝜋𝑟3 𝑙)])

12. Putting all known values , we get;
Now calculating the value of r2 by hit and trial method:-
r2 LHS RHS
2.8 3 7.22
3 3 4.775
3.2 3 3.65
3.3 3 3.33
3.4 3 3.033
3 =
ln[
𝑟2
2.5
×
6
𝑟2
0.5
×𝑒0.4]
ln(
𝑟2
2.5
)

13. So r2=3.4mm
For Refrigerator of 165 liters capacity, given data from Kirloskar
Ltd manual follows- [1]
Refrigerator cooling capacity (amount of refrigeration produced
or heat extracted in refrigerator) =76 kcal/hr
= 76×4.187×1000×3600
= 88.392 W
Power required running the compressor (work done on
refrigerant) =
1/8 HP = 1/8×746 =93.25 W
Qcondensor = QEVOPORATOR + W COMPRESSOR
=88.392+93.25
=181.642Watt

14. Assume efficiency of heat exchanger is 70%
So heat absorb by heat exchanger =QA
𝜂 =
𝑄 𝐴
𝑄 𝐶𝑂𝑁𝐷𝐸𝑁𝐶𝐸𝑅
0.7=
𝑄 𝐴
181.642
QA=127.149 Watt
So heat receave by pipe through condenser is 127.149 watt.

15. WHY OVEN?
• COMPLIMENT OF REFRIGERATOR
• LESS POWER REQUIRED
• ECONOMICALLY VIABLE
Fig 5

16. Principle
• The transient respond of the body can be determine
by relating its rate of change of internal energy with
convection exchange at the surface
• Initially transient condition
• Steady state later
• Heat transfer through convection
[5]
Fig 6

17. Energy Supply
• Oven use low grade energy to work
• It use the waste heat, which is release to
atmosphere
• The refrigerant circulates through tubes
("refrigerant lines") that travel throughout the
oven.
• This circulated refrigerant dissipate heat to the
air inside oven

18. CONCEPTS & DESIGN
• Since the temperature of air inside oven varies with time
t initially
𝑻 𝒕 − 𝑻 𝒐
𝑻𝒊 − 𝑻 𝒐
= 𝒆
−𝒉𝑨 𝒔 𝒕
𝝆𝑽𝑪
𝐐(𝐭) = 𝐡𝐀(𝐓 𝐨 − 𝐓𝐢)[𝐭 +
𝝆𝑽𝒄
𝒉𝑨
𝒆
−𝒉𝑨 𝒔 𝒕
𝝆𝑽𝑪 ]
Q= 𝝆𝑽𝑪(𝑻 𝒕 − 𝑻𝒊)
𝑄 =844.2 joules
T = 300 seconds
L = 0.6 meters

19. FABRICATION AND ASSEMBLY
• Parts of domestic refrigerator are as follows-
Compressor
Modified Air cooled Condenser
Capillary Tube
Plate type Evaporator
Parallel type heat exchanger
Insulated pipe
Insulated Cabin
[4]

20. Fabrication of Insulated Cabin
5.2.1 Material Used: Galvanized Iron Sheet
5.2.2 Process used - Sheet metal forming.
Fig 7

21. Fabrication of Cabin
• Inner box and outer box of insulated cabin are made
up of Galvanized iron sheet. After defining
dimensions, sheet metal working is performed. The
cabin is painted by silver color.
• Insulation material- here thermo Cole is used for
insulation purpose and it is of 3.5cm thickness.
• After forming all parts of cabin
it is assembled in well manner
as shown in
Fig 8

22. RESULTS
• The main aim is to use waste heat for domestic
purposes.
• Waste heat from condenser is utilised.
• All above analysis results in utilisation of waste
heat.
• COP of refrigerator is also increased.

23. • Actual COP of refrigerator
COPactual = 0.948
• Improved COP of refrigerator
COPimproved= 0.98
• Improvement in COP
=
0.98−0.948
0.948
x100
= 3.3%
COP improved varies than the actual calculated because of following errors.
1. Heat outleak while opening or closing the door cannot be exactly evaluated.
2. Actual COP is different than the value taken because the refrigerator is old.
3. Air may leak in or out because of old gasket.

24. CONCLUSION
 Suitable heat recovery system can be designed and developed
for every household refrigerator.
 The experimentation has shown that such a system is practically
feasible.
 Technical analysis has shown that it is economically viable.
 If this can be started from individual level then it can sum up
and enormous effect can be obtained. Thus with small addition
in cost if we recover and reuse the waste heat, then definitely we
can progress towards energy conservation and simultaneously
achieve our day today function.
 In present situation where everybody in a home is moving out,
this combination of refrigerator and food warmer is
definitely a boom to efficient
house wife.

25. REFERANCES
• [1] S.C.Kaushik, M.Singh., Feasibility and Design studies for heat recovery
from a refrigeration system with a Canopus heat exchanger, Heat Recovery
Systems & CHP, Vol.15(1995)665673.
• [2] P.Sathiamurthi, PSS.Srinivasan, Studies on waste heat recovery and
utilization. Globally competitive eco-friendly technologies engineering
National conference, (2005)39.
• [3] P.Sathiamurthi, PSS.Srinivasan “Design and Development of Waste
Heat Recovery System for air Conditioning Unit, European Journal of
Scientific Research,Vol.54 No.1 (2011), pp.102-110
• [4] C.P. Arora, Refrigeration and Air conditioning PHI Publications, 2010.
• [5] Er.R.K.Rajput, Heat and Mass Transfer, 4e McGraw Hill Publication
2012
• [6] Design and Development of Waste Heat of domestic refrigerator
• [7] Frank P. Incropera and David P. Dewitt, Fundamentals of heat and Mass
Transfer 5e, Wiley India edition, 2008.