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 P 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 t his work the m ain energy parameters s uch as COP and work required for compressor are analysed and discussed. Key w ords: G as P ipeline Insulation; L iquid pi peline I nsulation; R 22; R 410a; 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 http://iaeme.com/Home/issue/IJMET?Volume=10&Issue=1
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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 i nsulation w hich is of pr ime i nterest f or m any e ngineering applications. I n 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 r efrigerant f low) 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 usi ng a ny of t he s ubstitute f luids t here i s a n i mportant i ncremental di fference i n 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. A ll m aterials t hat a re di scussed i n t he l iterature a re not f easible f or split air conditioner. Because, few materials are higher in cost, few are obsolete, and few cannot be used
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Effect of Insulations on Cop in Vapor Compression Refrigeration System for split air conditioner. For these reasons, we had chosen few insulation materials and few combinations of m aterials.Materials a nd their c ombinations s elected f or 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 a t various points a re t aken by using di gital thermometer until s teady s tate 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) 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 O bserving t he below F ig.1, i t can underst ood t hat NRF+AF i nsulation 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 PFS+NYR NYR NRF+NYR NRF+AF
COPA 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 PFS+NYR NYR NRF+NYR NRF+AF
COPA 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 R 410a a s t he w orking S ubstance. S o by c omparing t he r esults f rom F ig1 a nd F ig 2., irrespective of t he w orking r efrigerant ,f or a s ystem i f t he gas a nd l iquid pi pelines 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 PFS+NYR NYR NRF+NYR NRF+AF
WC for R22 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 PFS+NYR NYR NRF+NYR NRF+AF
COP ACTUAL for R22 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 an d 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 usi ng NRF+AF. I t has a lso been observed that COPA is hi gh, while using NRF+AF for SAC with R410a and COPA val ue was increased w hile 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 t he c ontext of ozone l ayer depletion , R 410a i s pr eferable t han R 22 w ith 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, e xperimentation c an be done w ith c hange i n i nsulation t hickness a nd c an 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
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Anusha Peyyala and Dr N V V S Sudheer compressor type. We 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] 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. [2] 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. [3] 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. [4] Mustafa A li E rsöz, A bdullah Y ildiz e t a l: T he e ffect o f w ind sp eed o n the economical optimum insulation thickness for HVAC duct applications. Elsevier international journal of refrigeration in 2016. [5] 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. [6] J.H. Wu, L .D. Y ang, J . Hou: E xperimental p erformance st udy of a sm all w all r oom air conditioner retrofitted with R290 and R1270. International Journal of Refrigeration 35 (1860-1868) in 2012. [7] A. Cavallini,G. Censi , D. Del Col , L. Doretti, G.A. Longo , L. Rossetto: Experimental in- vestigation 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. [8] 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. [9] 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. [10] Lemmon, E.W.,Huber, M.L.,Mclinden, M.O.: REFPROP,NIST standard reference database23,V8.Natiobal Institute of Standards, Gaithersburg, MD,U.S. [11] P. A nusha, 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. [12] P. A nusha, D r.NVVS S udheer “ Possibility o f U sing Ref rigerant Bl ends I n t he 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. NOME NCLATURE Symbol Description T Temperature s 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 http://iaeme.com/Home/journal/IJMET 1207 [email protected]
Anusha Peyyala and Dr N V V S Sudheer
NIST National Institute of Standards and Technology EPF Expanded polyethylene foam BP Bare pipe NRF Nitrile rubber foam PFS Polyethylene foam sheet NYR Nylon ribbon NRF+AF Nitrile rubber foam with aluminium foil NRF+NYR Nitrile rubber foam with nylon ribbon PFS+NYR Polyethylene foam sheet with nylon ribbon ASHRAE American Society of Heating, Refrigeration and Air-conditioning Engineers REFPROP Reference Fluid Thermodynamic and Transport Properties
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