International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 01, January 2019, pp. 1201-1208, Article ID: IJMET_10_01_122
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=01
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
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EFFECT OF INSULATIONS ON COP IN VAPOR
COMPRESSION REFRIGERATION SYSTEM
Anusha Peyyala
Assistant Professor V P Siddhartha Institute of Technology, Research Scholar, Acharya
Nagarjuna University, India.
Dr N V V S Sudheer
Associate Professor, R V R & J C College of Engineering, Guntur India
ABSTRACT
In this project, experimentation is done on Vapour Compression Refrigeration System
[VCRS] as the COP is high for this system and it is the present trend of the HVAC in the
domestic industry. This study presents investigation of best suited refrigerant and
insulation combination for gas pipeline and liquid pipeline of a split air conditioning
system. Analysis are performed for R22-Chlorodiflouromethane, a HydroChloroFlouro
Carbon refrigerant, which has been using in the present world that cause both global
warming and ozone layer depletion and R410a, mixture of di-flouromethane and
pentaflouroethane, a Hydroflouro carbon refrigerant, which is future of HVAC which
reduces the effect of ozone layer depletion [ODP] and Global Warming Potential
[GWP].For these two refrigerants, we had found out the best insulation suitable as
insulation also affects the COP of air conditioner, which has been observed from the
literature. Minimizing the temperature of refrigerant in suction line helps condensing unit
work more effectively intern the system performance increases. This reduces the overall
power required for working of air conditioner, thereby reducing the maintenance cost of
system. Also, it helps the manufacturer to provide best type of insulation for the system at
reduced cost thereby reducing overall cost of VCRS.To perform the experimental
comparison, 16 tests were carried out for 5 times with each refrigerant Insulation
combination. From analysis it is observed that, COPA for NRF+AF gives highest value
for R22 and R410awhen compared to various insulation materials. Power required for
VCRS is greater while using R410a than R22. So In this work the main energy parameters
such as COP and work required for compressor are analysed and discussed.
Key words: Gas Pipeline Insulation; Liquid pipeline Insulation; R22; R410a; ODP;
GWP; VCRS
Cite this Article: Anusha Peyyala and Dr N V V S Sudheer, Effect of Insulations on Cop
in Vapor Compression Refrigeration System, International Journal of Mechanical
Engineering and Technology, 10(01), 2019, pp.1201–1208
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Anusha Peyyala and Dr N V V S Sudheer
1. INTRODUCTION
As we all know that Refrigeration is the science of producing and maintaining temperatures below
that of the surrounding atmosphere. This means removing of heat from a substance to be cooled.
Heat always passes downhill, from a warm body to a cooler one, until both bodies are at same
temperature. In simple, refrigeration is cooling or removal of heat from a system. Ahmet Z sahin
et al [1], explained about Optimum insulation thickness of a circular duct subjected to external
radioactive heat transfer and is studied for a given amount of insulation material. They also
explained about an analytical solution which is obtained for the insulation thickness variation
over a pipe to maintain a uniform outer surface temperature. A high temperature fluid is
considered to be flowing through the pipe.
The amount of the insulation material is assumed to be limited. Heat transfer from the outer
surface of the pipe is through convection and radiation. The solution of the insulation thickness
is found to be independent from the outer surface convective and radiative heat transfer
coefficients. Alireza Bahadori et al [2], explained about selection and determination of optimum
thickness of insulation which is of prime interest for many engineering applications. In this study,
a simple method is developed to estimate the thickness of thermal insulation required to arrive at
a desired heat flow or surface temperature for flat surfaces, ducts and pipes. Abdullah Yildiz et
al [3], in their study explained the investigation into optimum insulation thickness of installed
inside building pipe network of VRF (variable refrigerant flow) systems. Optimum insulation
thickness, energy savings over a lifetime of 10 years and payback periods are determined for high
pressure gas pipelines, low pressure gas pipelines and low-pressure liquid pipelines under the
heating-only and cooling-only modes of the three-pipe VRF system using R-410A as refrigerant.
Mustafa Ali Ersoz et al [4], performed investigations on optimum insulation thickness, cost
savings and payback periods for gas pipeline and liquid pipeline under the heating operation of
1500 hours and cooling operation of 1500 hours of a split air conditioning system that used
flexible insulation foam as insulation material.
Analyses are performed for four different refrigerants indicated as R-22, R-134a, R-407C and
R-410A. Man- Hoe Kim et ala [5], did an experimental investigation for evaporating heat transfer
in 9.52 mm O.D. horizontal copper tubes was conducted. The refrigerants tested were R22 and
the near-azeotropic mixture, R410A. J H Wu et al [6], in their work, an original R22 wall room
air conditioner with a cooling capacity of 2.4 kW and energy efficiency ratio (EER) of 3.2 is retro
fitted with a compressor of a 20% larger displacement to charge R290 and R1270 for performance
experiments. A.Cavallini et al [7], in their work presented reports on experimental heat transfer
coefficients and pressure drops measured during condensation inside a smooth tube when
operating with pure HFC refrigerants (R134a, R125, R236a, R32) and the nearly azeotropic HFC
refrigerant blend R410A. M.Goto et al [8], in their work heat transfer coefficients were measured
for the condensation of R410A and R22 inside internally grooved horizontal tubes. R L Llopis et
al [9] presented a theoretical and experimental analysis of the performance of R22, R422A,
R417B, R404A in a two stage VCRS. Their results showed that when using any of the substitute
fluids there is an important incremental difference in the refrigerant mass flow rate through the
palnt and sometimes necessary to readjust the expansion valve of the system.
2. EXPERIMENTATION
Experimentation is done on SAC system of 5.25 KW designed for R22 & R410a were selected
for performance evaluation. It was tested as per the Indian Standard 1391 (1992) Part I, for unitary
air conditioners. The performance of SAC with R410a is compared with the baseline
performance. All materials that are discussed in the literature are not feasible for split air
conditioner. Because, few materials are higher in cost, few are obsolete, and few cannot be used
for split air conditioner. For these reasons, we had chosen few insulation materials and few
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Effect of Insulations on Cop in Vapor Compression Refrigeration System
combinations of materials.Materials and their combinations selected for experimentation are
EPF, NRF, PFS, NYR NRF+AF,NRF+NYR , PFS+NYR .Along with these materials, we also
conducted experimentation for Bare pipe (BP) (no insulation) so that variation in performance
can be observed with respect to it. Experimentation has been done, using these materials as
insulation in a SAC system using R22 and R410a as refrigerants. During this experimentation,
temperatures at various points are taken by using digital thermometer until steady state is
achieved. Values have been taken for R22 at Suction pressure = 4.48 bar Discharge pressure =
17.23 bar. Values have been taken for R410a at Suction pressure = 7.58 bar Discharge pressure
= 31.71 bar.
Temperature values are taken at various points TR, TE−LRI, TE−ttRO, TC−ttRI, TC−ttRO,
TCO−ttRI, TCO−LRO, TEV −LRI, TEV −LRO
Formulae Used,
(1)
(2)
(3)
(4)
∗ "4 $ "3 in Kw
(5)
All the thermo physical properties were considered from REFPROP 9 [10] for the considered
refrigerants. The above equations 1 to 5 are used for calculating different values. The data were
recorded for 5 times at an interval of 1 hour with different considered refrigerant insulation
combinations to obtain an average value after confirming the steady running state of an air
conditioner.
3. RESULTS AND DISCUSSIONS
By Observing the below Fig.1, it can understood that NRF+AF insulation is showing the
maximum COP value and Minimum Wc value when the considered VCR system is working with
R22 as the working Substance.
R22 Values
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
BP
EPF
NRF
PFS
COPA
PFS+NYR
NYR
NRF+NYR
NRF+AF
WC (KW)
Figure. 1: Variation of R22 refrigerant Properties with the Type of Insulation.
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Anusha Peyyala and Dr N V V S Sudheer
R410a Values
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
BP
EPF
NRF
PFS
COPA
PFS+NYR
NYR
NRF+NYR
NRF+AF
WC (KW)
Figure. 2: Variation of R410a refrigerant Properties with the Type of Insulation
By Observing the above Fig.2, it can understood that NRF+AF insulation is showing the
maximum COP value and Minimum Wc value when the considered VCR system is working with
R410a as the working Substance. So by comparing the results from Fig1 and Fig 2., irrespective
of the working refrigerant ,for a system if the gas and liquid pipelines were insulated with
NRF+AF, showing the maximum COP and minimum Wc.
Wc values for R22 & R410a
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
BP
EPF
NRF
PFS
WC for R22
PFS+NYR
NYR
NRF+NYR
NRF+AF
WC for R410a
Figure. 3: Compassion of Wc values for R22 & R410a refrigerants
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Effect of Insulations on Cop in Vapor Compression Refrigeration System
Actual COP values for R22 & R410a
3.00
2.50
2.00
1.50
1.00
0.50
0.00
BP
EPF
NRF
PFS
COP ACTUAL for R22
PFS+NYR
NYR
NRF+NYR
NRF+AF
COP ACTUAL for R410a
Figure. 4: Comparison of COP values for R22 & R410a refrigerants
From Fig3. We can understood that Wc required for r22 refrigerant is less when compared to
a system when using R410a as refrigerant. From Fig4. One can understand that actual COP value
when using R22 refrigerant is showing more value when compared to a system when using R410a
as refrigerant.
4. CONCLUSION
From analysis it is observed that, actual cop [COPA] for NRF+AF gives the highest value for
R22 and COPA value was increased while using NRF+AF when compared to insulation materials
of various types. We can understood that the Power required while using insulation materials is
less when compared to Bare Pipe and work required for compressor [WC] reduced maximum
while using NRF+AF. It has also been observed that COPA is high, while using NRF+AF for
SAC with R410a and COPA value was increased while using NRF+AF when compared to
various types of insulation materials. Also, power required for SAC is less while using NRF+AF
for R410a. Comparing R22 and R410A, COPA for SAC is 5% to 10% more while using R22
refrigerant than R410a refrigerant. Power required for SAC is greater while using R410a than
R22 as the WC for SAC is 13% to 24% more while using R410a refrigerant than R22 refrigerant.
Although, it is noted that R22 has better results when compared to R410a, in the context of ozone
layer depletion, R410a is preferable than R22 with best insulation, nitrile rubber foam with
aluminium foil [NRF+AF] to meet the performance of R22.
FUTURE SCOPE
In this experimentation, we have analyzed the performance parameters while using R22 and
R410a refrigerants and with seven different combinations of insulation materials and analysis is
done with fixed thickness of insulation by using the concept of critical radius of insulation.In
future, experimentation can be done with change in insulation thickness and can use other
insulation materials like rockwool, calcium silicate, fiber glass, etc., for experimentation. Further,
there are many other refrigerants like R290, R407C, etc., are available in market and by using
various combinations of refrigerants and insulations, experimentation can be done.In addition to
these, performance analysis can be done by changing expansion valve and compressor type. We
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Anusha Peyyala and Dr N V V S Sudheer
also suggest, using various proportions of suitable refrigerants to form a new refrigerants,
performance analysis can also be done with those refrigerants which have low GWP and low
ODP. Natural refrigerants will be the good option from an environmental point of view because
their GWP are nearly unity. Possibility of refrigerants and refrigerant blends effect on cop can be
further understood from papers [11,12].
ACKNOWLEDGEMENTS:
We would like to thank management of Siddhartha academy of general and technical education
[SAGTE], Convener of PVP Siddhartha Institute of technology, Principal of PVP Siddhartha
Institute of technology for supporting us to carry out this work academically and financially.
REFERENCES
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
Ahmet Z. Sahin, Muammer Kalyon et al: Maintaining uniform surface temperature along
pipes by insulation Elsevier Energy, Volume 30, Issue 5, April 2005, Pages 637-647.
Alireza Bahadori, Hari B. Vuthaluru et al: A simple method for the estimation of thermal
insula- tion thickness Elsevier Applied Energy, 87 (2010) 613–619.
Abdullah Yildiz, Mustafa Ali Ersöz et al: Effect of refrigerants on the economical optimum
in- sulation thickness for indoor pipelines of split air conditioning systems. Elsevier
Renewable and Sustainable Energy Reviews in 2015.
Mustafa Ali Ersöz, Abdullah Yildiz et al: The effect of wind speed on the economical
optimum insulation thickness for HVAC duct applications. Elsevier international journal of
refrigeration in 2016.
Man-Hoe Kim, Joeng-Seob Shin: Evaporating heat transfer of R22 and R410A in horizontal
smooth and micro fin tubes. International Journal of Refrigeration 28 (940–948) in 2005.
J.H. Wu, L.D. Yang, J. Hou: Experimental performance study of a small wall room air
conditioner retrofitted with R290 and R1270. International Journal of Refrigeration 35 (18601868) in 2012.
A. Cavallini,G. Censi , D. Del Col , L. Doretti, G.A. Longo , L. Rossetto: Experimental investigation on condensation heat transfer and pressure drop of new HFC refrigerants (R134a,
R125, R32, R410A, R236ea) in a horizontal smooth tube. International Journal of
Refrigeration 24 (73±87) in 2001.
M. Goto, N. Inoue, R. Yonemoto: Condensation heat transfer of R410A inside internally
grooved horizontal tubes. International Journal of Refrigeration 26 (410–416) in 2003.
R.Llopis, E.Torrella, R.Cabello, D.Sanchez: HCFC-22 replacement with drop in and retrofit
HFC refrigerants in a two-stage refrigeration plant for low temperature. International Journal
of Re- frigeration 35(2012), 810-816.
Lemmon, E.W.,Huber, M.L.,Mclinden, M.O.: REFPROP,NIST standard reference
database23,V8.Natiobal Institute of Standards, Gaithersburg, MD,U.S.
P. Anusha, Dr.NVVS Sudheer, “Experimental Investigation of COP Using Hydro Carbon
Refrigerant in a Domestic Refrigerator”, IOP Conf. Series: MSE 225 (2017) 012236
doi:10.1088/1757-899X/225/1/012236.
P. Anusha, Dr.NVVS Sudheer “Possibility of Using Refrigerant Blends In the Existing
Refrigerator & AC Systems: A Review” IOSR Journal of Mechanical and Civil Engineering,
ISSN: 2320-334X, Volume 13, Issue 3, June - 2016, PP 63-70.
NOMENCLATURE
Symbol
T
s
Description
Temperature
Entropy of refrigerant
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Effect of Insulations on Cop in Vapor Compression Refrigeration System
P
Pressure of refrigerant
h
Enthalpy of refrigerant
K
Thermal conductivity of insulation material,
hC
Coefficient of convective heat transfer
TR
Temperature inside room
TO
Temperature outside room
TE-LRI
Temperature of liquid refrigerant inlet to evaporator
TE-GRO
Temp of gas refrigerant outlet from evaporator
TC-GRI
Temp of gas refrigerant inlet to compressor
TC-GRO
Temp of gas refrigerant outlet from compressor
TCO-GRI
Temp of gas refrigerant inlet to condenser
TCO-LRO
Temp of liquid refrigerant outlet from condenser
TEV-LRI
Temp of liquid refrigerant inlet to expansion valve
TEV-LRO
Temp of liquid refrigerant outlet to expansion valve
h1
Enthalpy at evaporator inlet temperature
h2
Enthalpy at evaporator outlet temperature
h3
Enthalpy at compressor inlet temperature
h4
Enthalpy at compressor outlet temperature
COPT
Theoretical COP
COPA
Actual COP
COPR
Relative COP
Q
Refrigeration effect
Cp
Specific heat of refrigerant
m
Mass flow rate
WC
Compressor work
V
Velocity of air
Abbreviations:
SAC
Split air conditioner
AC
Air conditioner
ODP
Ozone Layer Depletion
GWP
Global Warming Potential
VCRS
Vapour Compression Refrigeration System
COP
Coefficient of performance
R22
Chlorodifluoromethane
R410a
Mixture of difluoromethane and pentafluoroethane
HVAC
Heating, ventilation and air conditioning
CFC
Chloroflouro carbon
HCFC
Hydro Cholroflouro carbon
HFC
Hydro Flouro carbon
HC
Hydrocarbon
TEWI
Total equivalent warming index
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NIST
EPF
BP
NRF
PFS
NYR
NRF+AF
NRF+NYR
PFS+NYR
ASHRAE
Engineers
REFPROP
National Institute of Standards and Technology
Expanded polyethylene foam
Bare pipe
Nitrile rubber foam
Polyethylene foam sheet
Nylon ribbon
Nitrile rubber foam with aluminium foil
Nitrile rubber foam with nylon ribbon
Polyethylene foam sheet with nylon ribbon
American Society of Heating, Refrigeration and Air-conditioning
Reference Fluid Thermodynamic and Transport Properties
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