Scholarly article on topic 'Performance Evaluation of a Domestic Refrigerator with a Thermal Storage Arrangement Using Propane as a Refrigerant'

Performance Evaluation of a Domestic Refrigerator with a Thermal Storage Arrangement Using Propane as a Refrigerant Academic research paper on "Materials engineering"

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{"Domestic Refrigerator" / Evaporator / "Phase change Material / Propane"}

Abstract of research paper on Materials engineering, author of scientific article — D. Shikalgar Niyaj, S.N. Sapali

Abstract In developing countries like India, a general problem relates to frequent power breakdown, which gives augment to the spoiling of unpreserved items such as medicine and foodstuff due to lack of a passive cold retention system. Moreover, the rural India is subjected to maximum isolation due to power cuts for many hours and even days. The paper has an attempt to tackle this problem by developing a domestic refrigerator system capable of maintaining the cooling effect for more than 15hours without energy input and being compact as well as cost-effective. The second objective was to reduce the global warming potential caused by HCFC refrigerant. Taking into account the very needs of an average rural household in India, the required cooling load is estimated. The system was designed and analyzed using R290 (Propane) as a refrigerant by replacing R134a. The theoretical and experimental analysis of 45 liter domestic refrigerators using R290 as a refrigerant is carried out. The R290 is a replacement for R134a and R22 refrigerants. The Phase change material (PCM) is located in the newly designed evaporator in order to improve its efficiency and provide a storage capacity allowing a number of hours of refrigeration without energy supply. The system has been tested with Ethylene Glycol as a PCM with and without thermal load. Results show that the refrigerant R290 have a slightly lower coefficient of performance than R134a for the condensation temperature of 35°C to 43°C and evaporating temperatures range between −5°C to 5°C. Depending on the load in the refrigerator with PCM the average compressor running time per cycle is reduced significantly and it is in the range of 17% to 20% as compared with refrigerator without PCM. The coefficient of performance of refrigeration systems with R290 as refrigerant is comparable with R134a as a refrigerant and starting torque of compressor reduces which leads to improvement in a life span of the compressor.

Academic research paper on topic "Performance Evaluation of a Domestic Refrigerator with a Thermal Storage Arrangement Using Propane as a Refrigerant"

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Energy Procedia 109 (2017) 34 - 39

International Conference on Recent Advancement in Air Conditioning and Refrigeration, RAAR 2016, 10-12 November 2016, Bhubaneswar, India

Performance Evaluation of a Domestic Refrigerator with a Thermal Storage arrangement Using Propane as a Refrigerant

Shikalgar Niyaj Da* Sapali S Nb

a Assistant Professor, Department of Mechanical Engineering, College of Engineering Pune, Maharashtra, India b Professor, Department of Mechanical Engineering, College of Engineering Pune, Maharashtra, India

Abstract

In developing countries like India, a general problem relates to frequent power breakdown , which gives augment to the spoiling of unpreserved items such as medicine and foodstuff due to lack of a passive cold retention system. Moreover, the rural India is subjected to maximum isolation due to power cuts for many hours and even days. The paper has an attempt to tackle this problem by developing a domestic refrigerator system capable of maintaining the cooling effect for more than 15 hours without energy input and being compact as well as cost-effective. The second objective was to reduce the global warming potential caused by HCFC refrigerant. Taking into account the very needs of an average rural household in India, the required cooling load is estimated. The system was designed and analyzed using R290 (Propane) as a refrigerant by replacing R134a. The theoretical and experimental analysis of 45 liter domestic refrigerators using R290 as a refrigerant is carried out. The R290 is a replacement for R134a and R22 refrigerants. The Phase change material (PCM) is located in the newly designed evaporator in order to improve its efficiency and provide a storage capacity allowing a number of hours of refrigeration without energy supply. The system has been tested with Ethylene Glycol as a PCM with and without thermal load. Results show that the refrigerant R290 have a slightly lower coefficient of performance than R134a for the condensation temperature of 35°C to 43 °C and evaporating temperatures range between -5°C to 5°C. Depending on the load in the refrigerator with PCM the average compressor running time per cycle is reduced significantly and it is in the range of 17% to 20% as compared with refrigerator without PCM. The coefficient of performance of refrigeration systems with R290 as refrigerant is comparable with R134a as a refrigerant and starting torque of compressor reduces which leads to improvement in a life span of the compressor.

© 2017 The Authors. Published byElsevierLtd. Thisis an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of RAAR 2016. Keywords: Domestic Refrigerator, Evaporator, Phase change Material,Propane

1876-6102 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of RAAR 2016. doi:10.1016/j.egypro.2017.03.045

1. Introduction

Conquering execution of the different components of the Montreal protocols and Kyoto protocols will express to the effectual phase-out of Ozone Depletion Potential and Global Warming Potential substances if appropriate long term alternative refrigerants are identified. 1,1,1,2-tetrafluoroethane (HFC-134a) was identified as an alternate refrigerant to Chlorodifluoromethane (R22). The problems associated with ozone depletion and climate change are technically, theoretically and monetarily interconnected. Ozone depletion and global climate change are linked through physical and chemical processes in the atmosphere. The industries in the field of HVAC have grown extensively over the past few decades and will continue to do so all over the globe for the forth coming year. Ozone Depletion Potential and Global Warming Potential values are very less for the Hydro carbon group of refrigerants, but these refrigerants are limited in use for safety reasons. The energy efficiency of refrigerator is improved using thermal energy storage material . The cooling capacity stored in the PCM is used to stabilize the temperature in the compartment, also reduces the effects of peak loads and cooling losses during periods when the door is open [4]. Refrigerator has previously tested a with 5 mm and 10 mm ice slabs as a PCM. The results showed that the refrigerator autonomy increased from 5 to 9 hours depending on the thermal load [9]. In order to simulate the cycle, all components are interconnected with each other to form the complete system and the thermodynamic properties of R134a and R290 refrigerants are compared with the help of the REFPROP 9.1 software.

2. Phase Change Material( PCM)

Phase Change Material is a substance who has high heat of fusion. During melting and solidifying at a certain temperature large amount of energy get stored or release by PCM . The experiments be carried on refrigerator to evaluate the energy performance and the cool storage capacity of the refrigerator with and without PCM. The use of phase change materials (PCMs) to accumulate thermal energy in domestic refrigerators is a new solution. The cooling capacity stored in the PCM can be used to stabilize the temperature in the compartment.

Gobin D et al [5] have previously tested a domestic refrigerator with 5mm and 10 mm ice slabs in get in touch with with the evaporator. Their result shows that the refrigerator autonomy increased from 5 to 10 hours depending on the thermal load. It was observed that the ice slab of 10 mm slab was never completely freeze, probably because of low thermal conductivity of the PCM and low cooling capacity of the 5 x 10-6 m3 (i.e. 5 cm3) swept volume compressor employed. During experimentation in domestic refrigerator Ethylene glycol was used as a PCM [6].

3. Experimental Setup

A household refrigerator is incredibly common for the storage of perishable food items, medicines, cold drinks. These refrigerators are available in various capacities such as 45 litres to 300 litres, etc. These consume electrical energy at the rate of about 100W to 300W. The Largest population in India is staying in the villages. Almost these villages do not get electricity for more than 10 hrs per day. The major heat load comes from the outside environment of the storage space through insulated walls. Moreover, door openings bring warm and moist air into the cold storage space, raising the temperature. The refrigerator capacity is estimated based on the needs of a rural family for domestic use. The cooling load is predicted based on heat ingress into the refrigerator through walls, door openings, and product load. Theoretical and Experimental analysis of the refrigerator using propane (R290) as a refrigerant is carried out to maintain the required temperature of the refrigerator during power failure for fifteen hours. PCM is lagged in the modular chamber of the refrigerator.

The domestic refrigerator is designed, fabricated and tested with R290 as an eco-friendly refrigerant. To begin with, refrigerator performance is simulated using simulation software at different cooling capacities and in experimentation, the real world effect was simulated by door openings and by electrical breakdown. Thermocouples are bonded to the tube surface at compressor discharge, condenser discharge, and capillary

outlet, evaporator outlet, in the refrigerated cabin and over the PCM surface.

The experimental device shows that figure 2 is a single compartment refrigerator with the following qualities:

• volume of cabin: 45 litres

• Evaporator: free convection , roll bond, back wall positioned with Cavity

• Condenser: wire tube condenser with free convection

• Hermetic sealed reciprocating compressor

• Refrigerant: R290

• On/off control and auto defrost.

The Ethylene glycol is placed on the back side of the evaporator . It must be noted that a significance of this modification is that both the faces of an evaporator are used.

Fig. 1. Line diagram of experimental setup.

4. Experimental Procedure

The domestic refrigerator was designed and tested with equipped instrumentation at appropriate locations to record data. Using thermocouples the temperatures were recorded with an accuracy of ± 0.5 K. Four pressure gauges are mounted at compressor suction side and discharge side, at evaporator inlet side and at condenser outlet side for measurement of pressure and to calculate the pressure drop. The experimental set up was then installed in the test room with the purpose to maintained surrounding temperature 23°C. Experiments are conducted in a controlled environment. The overall heat transfer coefficient for the refrigerator is 21.3 W/m2K. The unit is maintained under steady state conditions for about five hours, the data was recorded over the period of 15 minutes time intervals. Initially, the baseline performance test was established with R134aas a refrigerant. The pressures, temperatures, power consumption and refrigerant charge for R134a are recorded. All safety precautions are taken while charging and testing the unit with R290. All electric components as, capacitor, thermostat switch, and on-off switch are properly sealed. The experimentation was carried out with R 290 as a refrigerant in a controlled environment.

Fig. 2. Evaporator geometry (a) 3D geometry of test setup (b) experimental setup.

5. Energy Consumption of Compressor

The energy consumption by the compressor during experimentation was measured and stored in a computer. The test was carried out at 23°C and 28°C room temperatures. The refrigerator consumes more energy at 28°C ambient temperature than at 23°C ambient temperatures for all refrigerants. The compressor consumes 3% less energy with R290 at 28°C condenser temperature.

6. Result and discussion

An experimental test is carried out at different loads to examine the performance enhancement of a domestic refrigerator with PCM and without PCM (Ethylene Glycol). The following conclusions are drawn based on the experimental results.

1. PCM solidification Time: The ratio of melting time to solidification time is 9 that significantly show that the melting process almost 9 times slower than solidification directly produces cooling effect for more than 7 hrs. During a test at -10°C PCM temperature the power supply to the compressor was cut off. The temperature deviation in the cabin was kept within 3°C it will give a great advantage over conventional domestic refrigerator for vegetable preservations

2. Variation of PCM and refrigerator cabin temperature without load: without energy input to compressor PCM material maintains cabin temperature below 10°C for 8 hours and below 15°C for 14 hrs. PCM provides uniform cabin temperature, though all cycle. The figure 3 shows that the cabin temperature was maintained below 15°C for 14 hours it gives a great advantage over conventional domestic refrigerator for vegetable preservation during a power failure.

Fig. 3. Temperature variation with respect to time with PCM

3. Temperature reduction in a cabin by using PCM has indicated by blue line, that shows reduction of 1°C for one-hour duration as shown in figure number 3. Depending on the load on the refrigerator with PCM the average compressor running time per cycle is reduced considerably and it found that 17% to 20% reduction as compared with conventional refrigerator without PCM. Graph shows power requirement is increased by 7.12% for the temperature variation from 20°C to 45°C. The refrigerant charge for same refrigeration system with R290 as refrigerant is reduced by 40% as compared with R134a for the same operating conditions.

Fig. 4. Variation of temperature with respect to time with PCM

The sudden temperature rises or spikes in the graph shown by blue colour indicate the time at which by intention of door was opened and the temperature rise is because of the ingress of heat through atmospheric air getting inside when the load is added cabin temperature increases by around 7°C. The instant at which PCM start melting graph shows a large difference between inside cabin and PCM temperature

7. Conclusions

1. The Investigation shows that PCM is useful to maintain the refrigerator cabin temperature

below 100 C for 16 hours as compared to a conventional refrigerator that maintains cabin temperature for 4 hours without power supply.

2. PCM is also used to maintain the temperature variation inside cabin within 2°C to 3°C that

helps to increase the life of perishable food products as compared with conventional one where the temperature variation is 6°C to 8°C.

3. The compressor running time per cycle is reduced significantly and it found that reduction

about 17% to 20% as compared with conventional refrigerator without PCM.

4. The coefficient of performance of refrigeration systems with R290 as refrigerant is comparable

with R134a as a refrigerant and starting torque of compressor reduces which leads to improvement in the life of a compressor.

8. References

[1] UNEP, Montreal protocol on substances that deplete the ozone layer, United Nations environment programme (UNEP); 1987.

[2] Kyoto protocol to the United Nations framework convention on climate change, United Nations (UN), New York, USA; 1997.

[3] Azzouz, K., Leducq, D. and Gobin, D. Enhancing the performance of household refrigerators with latent heat storage: an experimental investigation, International Journal of Refrigeration, 32: 16341644, 2009.

[4] A. Padalkar, K. Mali, S. Devotta, Simulated performance of R-290 in air conditioner, in : The 23rd International congress refrigeration, Czech republic, August 2011.

[5] Azzouz, K., Leducq, D., Guilpart, J., Gobin, D., 2005. Improving the energy efficiency of a vapor

compression system using a phase change material. In: Proceedings 2nd Conference on Phase Change Material & Slurry, Yverdon les Bains, Switzerland, 15 - 17 June 2005.

[6] Azzouz, K., Leducq, D., Gobin, D., 2008. Performance enhancement of a household refrigerator by an addition of latent heat storage. International Journal of Refrigeration 31 (5), 892-901.

[7] Marques, C., Davies, G, Maidment, G., Evans, J. A. "Application of phase change materials to domestic refrigerators." 9th International Conference on Phase-Change Materials and Slurries for Refrigeration and Air Conditioning, 2010.

[8] Joseph Sekhar S, Mohan Lal D, Renganarayanan S. Improved energy efficiency for CFC domestic refrigerators retrofitted with ozone friendly HFC134a/HC refrigerant mixture. International Journal of Thermal Science 2004; 43(3):307-14.

[9] Improved energy efficiency for CFC domestic refrigerators retrofitted with ozone-friendly HFC134a/HC refrigerant mixture (2004) International Journal of Thermal Sciences, 43 (3), pp. 307314.

[10] Testing of propane/isobutene mixture in domestic refrigerators (2000) International Journal of Refrigeration, 23 (7), pp. 517-527.

[11] Cool pack Software http://www.et.web.mek.dtu.dk/Coolpack/UK/download.html: Denmark Technical University.

[12] A theoretical comparison of two eco-friendly refrigerants as alternatives to R22 using a simple vapour compression refrigeration system (Article), Transactions of Famena ,Volume 38, Issue 3, 2014, Pages 59-70.