EXPERIMENTAL VERIFICATION OF PERFORMANCE OF CAPILLARY TUBE USING VAPOUR COMPRESSION REFRIGERATION SYSTEM

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1 EXPERIMENTAL VERIFICATION OF PERFORMANCE OF CAPILLARY TUBE USING VAPOUR COMPRESSION REFRIGERATION SYSTEM Prof. S.V.Rao 1, Hitesh Sharma 2, Pankaj Kumar Gound 3, Tukaram Walgude 4, Shekhar Gavas 5 1 Prof. S. V. Rao(Professor), Mechanical Engg,VOGCE,Aghai,Thane,India, svrao1961@gmail.com 2 HiteshMadanlal Sharma (student), Mechanical Engg, VOGCE,Aghai,Thane,India, hitesh168@gmail.com 3 Pankaj Kumar Gound (student), Mechanical Engg,VOGCE,Aghai,Thane,India,Pankaj_555@yahoo.com 4 TukaramWalgude (student) Mechanical Engg VOGCE, Aghai,Thane, India, Tukaramwalgude00@gmail.com 5 Shekhar P. Gavas (student), Mechanical Engg, VOGCE,Aghai,Thane,India, shekhargavas777@gmail.com Abstract The refrigerator is considered to be one of the vital home appliances utilizing mechanical vapor compression refrigeration system cycle in its process. The main issue of the paper is the performance of the system and various researches and development process of refrigeration test rig are still ongoing to evaluate and improve efficiency of the system. The main objective of this paper is to study the vapour compression cycle, p-h chart and to calculate the performance using expansion devices like capillary tube and thermostatic expansion valve. The Comparison of performance of expansion devices are calculated through experiment on VCR system. The refrigerant R-134a is used in the compressor of VCR system. In this research work, a domestic refrigerator is selected to build the refrigeration test rig. Keywords: Capillary Tube, Thermostatic expansion valve, R-134a etc Introduction In today s era, refrigeration industry is passing through evolutionary changes. Emphasis is given to save energy and to protect the environment. Refrigeration technology is expected to develop technologies which are cheap and using refrigerant other than CFC. Refrigerator is a cooling appliance comprising a thermally insulated compartment and a refrigeration system to produce cooling effect in the insulated compartment. Meanwhile, refrigeration is define as a process of removing heat from a space or substance and transfers that heat to another space or substance. Nowadays, refrigerators are extensively used to store foods which deteriorate at ambient temperatures; spoilage from bacterial growth and other processes is much slower in refrigerator that has low temperatures. In refrigeration process, the working fluid employed as the heat absorber or cooling agent is called refrigerant. The refrigerant absorbs heat by evaporating at low temperature and pressure and remove heat by condensing at a higher temperature and pressure. As the heat is removed from the refrigerated space, the area appears to become cooler. The process of refrigeration occurs in a system which comprises of a compressor, a condenser, a capillary and an evaporator. The refrigerator works in a thermodynamic cycle which obeys Second Law of Thermodynamics. In this work the performance of refrigeration system is determined using a refrigerant R22 and evaluated its Coefficient of Performance (COP).

2 Expansion device function The basic function of expansion device used in refrigeration system is as follows:- 1. Reduce pressure from condenser pressure to evaporator pressure, and 2.

2 2 Expansion device function The basic function of expansion device used in refrigeration system is as follows:- 1. Reduce pressure from condenser pressure to evaporator pressure, and 2. Regulate the refrigerant flow from the high- pressure liquid line into the evaporator at a rate equal to the evaporation rate in the evaporator. Under ideal conditions, the mass flow rate of refrigerant in the system should be proportional to the cooling load sometimes; the product to be cooled is such that a constant evaporator temperature has to be maintained. In other cases, it is desirable that liquid refrigerant should not enter the compressor. In such case, the mass flow rate has to be controlled in such a manner that only superheated vapor leaves the evaporator. Again, an ideal refrigeration system should have the facility to control it in such a way that the energy requirement is minimum and the required criterion of temperature and cooling load are satisfied. Some additional controls to control the capacity of compressor and the space temperature may be required in addition, so as to minimize the energy consumption. The expansion devices used in refrigeration systems can be divided into fixed opening type or variable opening type. As the name implies, in fixed opening type the flow area remains fixed, while in variable opening type the flow area changes with changing mass flow rates. Capillary tube belongs to the fixed opening type, while the thermostatic expansion valve belongs to the variable opening type. 2.1 Capillary tube A Capillary tube is a small bore tube. It reduces the pressure of liquid refrigerant from condenser pressure to evaporator pressure when connected in a liquid line. The length of capillary is greater when the evaporator pressure is lower. So capillary of refrigerator is much longer than that of window air conditioner. The capillary tube is a simple device with no moving part. Fig-1: Capillary Tube 2.2 Thermostatic expansion valve Thermostatic Expansion Valve is the most commonly used valve in all large refrigeration system of variable loads. The valve also has a diaphragm. The spring pressure and evaporator Thermostatic expansion valve is the most versatile expansion valve and is most commonly used in refrigeration systems. A thermostatic expansion valve maintains a constant degree of superheat at the exit of the evaporator; hence it is most effective for dry evaporators in preventive the slugging of the compressors since it does not allow the liquid refrigerant to enter the compressor. This consists of a feeler bulb that is attached to the evaporator exit tube so that it senses the temperature at the exit of evaporator. The feeler bulb is connected to the top of the bellows by a capillary tube. The feeler bulb and the narrow tube contain some fluid that is called power fluid. The power fluid may be same as the refrigerant in the refrigeration system, or it may be different. In case it is different from the refrigerant, then the TEV is called TEV with cross charge.

3 Figure 2- Thermostatic Expansion valve 2.3 Experimental set-up A setup manufactured to experimentally investigate the performance of capillary tube and Thermostatic Expansion valve for refrigerant R-134a.Experimental setup consist of four major parts of refrigeration system such as compressor, which compress refrigerant, condenser which rejects the heat from refrigerant at constant pressure, expansion device which drop down the temperature and pressure of the refrigerant and finally evaporator which absorbs heat from the refrigerated space.all the component of the refrigeration system is displayed on the portable wooden panel. Sr. No Parameters Description 1 Type Refrigeration Test Rig (Refrigeration Tutor) 2 Refrigerant R-134a 3 Capacity 0.18 TR 4 Compressor Hermetically Sealed, single cylinder reciprocating 5 Condenser Finned Coils, air cooled 6 Expansion device Capillary tube and TXV 7 Evaporator Shell & tube type evaporator Table No- 1 Components in the experimental setup

4 3 Experiment readings for capillary tube SR.NO. Description Symbol Units Readings 1 Condensing Pressure P c psi Evaporating Pressure P e psi 38 3 Rotameter flow rate ṁ LPH 28 4 Condenser inlet temperature T 1 0 C 58 5 Condenser outlet temperature T 2 0 C 40 6 Evaporator inlet temperature T 3 0 C 6 7 Evaporator outlet temperature T 4 0 C 24 8 Compressor energy-time for 10 flashes T c S 20 9 Compressor Current I A 1 10 Compressor Voltage V V Calorimeter temperature 0 C Heater energy S Calculation for capillary tube 1. Theoretical COP: COP (theoretical) = H eo -H co / H ci -H eo = / COP (theoretical) = Actual COP: COP (actual) = N (actual) / W (actual) COP (actual) = 2 = 0.75 / Relative COP = COP (actual) / COP (theoretical) Relative COP= Carnot COP = T L / T H -T L = 278 / ( )

5 Carnot COP= Efficiency of the plant on Carnot cycle basis = COP (actual) / COP (Carnot) = 2 / 7.31 = CONCLUSION Fixed expansion devices, such as capillary tubes, work at one preset level and have no ability to compensate for load changes. The values of COP Carnot, COP theoretical, COP actual are in accordance with theory and are in descending order. Variations of capacity over the ambient temperature range of 26 0 C to 55 0 C can cause a performance loss of 85% with a cap tube system. A well-tuned expansion valve system will lose less than one half this amounts, while maintaining better compressor temperature control. Carnot COP is higher than theoretical COP and actual COP in case of both thermostatic expansion valve and capillary tube. Experimental results shows thermostatic expansion valve has higher Carnot, theoretical and Actual cop than capillary tube. It was found that the energy consumption of the thermostatic expansion valve system was only lower than that of the capillary tube system at higher cooling loads and at lower cooling capacities. 5. ACKNOWLEDGEMENTS I with great pleasures take this opportunity to express my deep sense of gratitude towards Vishwatmak Om Gurudev College Of Engineering, Aghai. For allowing me to do the case study work on Comparison of Performance of Capillary Tube through Experiment on Vapour Compression System. I also would like to thank my Guide Prof. S.V. Rao & Co-Guide Prof. Pavan Nikam, Department of Mechanical Engineering for his valuable guidance and constant inspiration during the completion of this paper. 6. REFERENCES [1] Performance Evaluation of a Vapor Compression Refrigeration System for Simultaneous Cooling & heating by using R22 & Alternatives Refrigerants by Rahul P Patel & Dr. R.K. Kapadia. [2] Experimental analysis of VCR system using the refrigerant with Nano particles by N. Kamaraj& A. ManojBabu. [3] Experimental verification of the variable affecting the performance of VCR cycle by KiranDilipBhosale & SurajDilipBhosale. [4] Performance analysis of a Domestic Refrigerator by M. Y. Taib& A.A. Aziz [5] Comparative performance analysis of RTG for R-12 & R-134a by Parmesh& Mr. Amit Sharma. [6] Experimental analysis of VCR system with variable length to diameter ratio of capillary tube by T. Raghavendra, H. Ranganna &G.Maruthi Prasad Tadav. [7] Pdf on Expansion devices. [8] Optimization of Expansion valve control in Refrigeration appliances under cyclic operation by Marcel van Beek& Hans ele Jong. [9] Experimental analysis of Thermostatic expansion valve, constant Expansion device & Capillary tube on Vapor Compression Refrigeration System by Rohit Joshi, Dr.Atul.A. Patil& Prof. Tushar.A. Koli. [10] Study & Review on the performance analysis of various expansion devices in VCR system by Rohit Joshi, Dr.AtulPatil& Prof. TusharKoli.

6 [11] A Generalized correlation for pressure drop of Refrigerant R-134a through Helical Capillary Tubes by N. Dhekale& Dr. P.A. Patil. [12] Comparison analysis between a capillary tube & an electronic expansion valve in a Household Refrigerator by Jackson B. Marcinichen. [13] Experiment analysis and performance testing of capillary tube and thermostatic expansion valve by Amol A. Gawali&Madhav S. Joshi.

An Experimental Study of a Simple Vapour Compression Refrigeration System with Varying Parameters

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