Waghmare Tushar Ramrao, D.S.Nakate

Transcription

1 International Engineering Research Journal Performance analysisof vapor compression system by using capillary tube suction line heat exchanger and helical condenser for R134a Waghmare Tushar Ramrao, D.S.Nakate P.G.Student, M.E.Heat Power Engineerin, Dr. D.Y.Patil School of Engineering Academy,Ambi, Pune, India Asst.Prof.M.E.Heat Power Engineering Dr. Dr. D.Y.Patil School of Engineering Academy, Ambi, Pune, India Abstract A vapor compression system is the one in which removal of heat from cold space is made by compressing the vapors in compressor. Many refrigeration systems work on it. The important parts of the system include evaporator, compressor, condenser and expansion device. Due to low cost and simplicity capillary tube is used as an expansion device in many vapor compression systems. In the present work capillary tube heat exchanger is used as suction line heat exchanger, forming counter flow heat exchanger. Using this it is observed that the temperature of refrigerant entering the compressor increases and as a result of this there is reduction in the torque required by compressor thereby increasing the refrigeration effect and COP of system. The main objective of the work is to evaluate the performance of vapor compression system by using CTSLHX of three different lengths and in the second part removing the CTSLHX and replacing the existing condenser by using helical condenser of three different diameters and comparing the results. Keywords compression; heat exchager; CTSLHX; condenser; I. INTRODUCTION The vapor compression system is one of the most commonly used systems of refrigeration now days.the first mechanically produced cooling system was developed in England in 1834.The process later became known as vapor compression. After availability of electricity automatic refrigeration system was developed in 1897.Basically a refrigeration or air conditioning is nothing more than a heat pump whose job is to remove heat from a lower temperature source and reject heat to high temperature sink.the Vapor Compression Refrigeration Cycle is a process that cools an enclosed space to a temperature lower than the surroundings. To accomplish this, heat must be removed from the enclosed space and dissipated into the surroundings. However, heat tends to flow from an area of high temperature to that of a lower temperature. During the cycle refrigerant circulates continuously through four stages. The first stage is called Evaporation and it is here that the refrigerant cools the enclosed space by absorbing heat. Next, during the Compression stage, the pressure of the refrigerant is increased, which raises the temperature above that of the surroundings. As this hot refrigerant moves through the next stage, Condensation, the natural direction of heat flow allows the release of energy into the surrounding air. Finally, during the Expansion phase, the refrigerant temperature is lowered by what is called the auto refrigeration effect. Y. S. Lee and C. C. Su, have studied the performance of VCRS with isobutene andcompare the results with R12 and R22. They used R600a about 150 g and set the refrigeration temperature about 4 C and -10 C to maintain the situation of cold storage and freezing applications. They used 0.7 mm internal diameter and 4 to 4.5 m length of capillary tube for cold storage applications and 0.6 mm internal diameter and 4.5 to 5 m length of capillary tube for freezing applications. They observed that the COP lies between 1.2 and 4.5 in cold storage applications and ions, whereas that with a single tube is suitable in the freezing applications. Cabello, E. Torrella and J. Navarro-Esbri, have analyzed the performance of a Vapor compression refrigeration system using three different working fluids (R134a, R407c and R22). The operating variables are the evaporating pressure, condensing pressure and degree of superheating at the compressor inlet. They analyzed that the power consumption decreases when compression ratio increases with R22 than using the other working fluids. James M. Calm, has studied the emission and environmental impacts of R11, R123, R134a due to leakage from centrifugal chillers system. He also investigated the total impact in form of TEWI and change in system efficiency or performance due to Charge loss. He also summarized the methods to reduce the refrigerant losses by the system like design modifications, improvement in preventive maintenance techniques, use of purge system for refrigerant vapor recovery, servicing and lubricant changing in system.

2 II. SIMPLE VAPOR COMPRESSION SYSTEM A. Diagram Figure 1: Basic cycle of domestic refrigeration system Refrigerant used----r134a Compressor capacity hp Evaporator --- Length m Diameter mm Condenser ---- Length m Diameter mm Capillary ---- Length m Diameter mm Compressor capacity = 0.16 HP Compressor discharge temperature = 59 to 60 ᵒC Compressor suction pressure = 1.03 bar Compressor discharge pressure = bar Mass flow rate to obtain 1TR = 1.61 kg/min Temperature of vapor refrigerant entering the HE = - 15 ᵒC=tc1=258K Temperature of vapor refrigerant leaving the HE = - 11 ᵒC=tc2=262K Temperature of liquid refrigerant entering from condenser in the HE = 44 ᵒC=th1=317K Temperature of liquid refrigerant leaving from the HE = 39 ᵒC=th2=312K III SET UP Figure 2: Pressure-enthalpy graph for vapor compression refrigeration system B. Experimental procedure and setup Following procedure is selected 1.Experimental set up

3 6. Heat rejected in condenser = (h2 h3) ctslh x Analysis of ctslhx parameter existing Heat exch.length in cm COP NRE kj/kg Mass flow rate kg/min Work of compression KJ/kg Theoretical power of compressor KW FIGURE3 C. capillary tube suction line heat exchanger types B.Graphical presentation for CTSLHX COP COP against lenghth of hx D. Performance calculations 1. Net Refrigerating Effect (NRE) = (h1 h4) 2. Circulating rate to obtain one tone of Refrigeration, = 210/ NRE 3. Heat of compression = (h2 h1) 4. Heat Equivalent of work of compressor = m r x (h2 h1) 5. Coefficient of performance (COP) = Net refrigerating Effect Heat of Compression Graph1 NRE Graph 2 NRE against lenghth of hx

4 mass flow rate against lenghth of hx mass flow rate Mass flow rate kg/min Work of compression KJ/kg Theoretical power of compressor KW 1.5 B.Graphical presentation for helical condenser Graph3 work of comp against lenghth of hx Work of comp power of comp against lenghth of hx power of comp Graphs 4 and Graph1 cop NRE COP of comp against coil dia NRE against Coil dia Coil Diamter coil diameter mass flow rate against coil dia mass flow rate III. USING THE HELICAL CONDENSER A. Analysis by using helical condenser Table 2 parameter existing Helical cond. Dia. In mm COP NRE kj/kg coil diameter

5 work of comp Graphs2,3,4,5 B. Results and disscussion work of comp against coil dia coil diamter power of comp against coil dia power of comp coil diameter COP: It is observed that the COP of the system using helical condenser by using 262 mm is 4.33 from graph1 for helical condenser. The same as observed for existing diameter is 3.56 therefore there is an increase in COP by 17.7%. Graph1 of helical condenser. It is observed that the COP of the system using ctslhx by using 32 cm length is 3.42 from graph1 for ctslhx. The same as observed for existing length is 3.24 therefore there is an increase in COP by 5.2%. Graph 1 of ctslhx. NRE: The value of net refrigerating effect for helical condenser is 130kj/kg for 262 mm diameter while the value of NRE for existing is 124kj/kg in experiment. Therefore there is an increase in NRE by 4.61%.Graph2of helical condenser. The value of net refrigerating effect ctslhx is 145kj/kg for 32cm length while the value of NRE for existing is 133.3kj/kgin experiment. Therefore there is an increase in NRE by 8.06%.Graph2 of ctslhx. Work of compression. The value of work of compression for helical condenser is 30 kj/kg for 262 mm diameter while the value ofwork of compression for existing is35 kj/kg in experiment. Therefore there is fall in value of work of compression by 14.28%.as shown in graph 4 of helical condenser. The value of work of compression for ctslhx for a length of 32cm is 39.7 kj/kg, which is 41 kj/kg for existing. Therefore there is decrease of 3.17% in work of compression. Graph 4 of ctslhx. Power Consumption The value of power of compression for helical condenser is 0.81 kw for 262 mm diameter while the value ofpower of compression for existing is 0.98 kw in experiment. Therefore there is fall in value of power of compression by 17.34%, as shown in graph 5 of helical condenser. The value of power of compression for ctslhx is 1.011kw for 32 cm length while the value ofpower of compression for existing is 1.07 kw in experiment. Therefore there is fall in value of power of compression by 5.51%, as shown in graph 5 of ctslhx. C. Conclusions In the present work experimental investigation is carried out to investigate the performance of vapour compression refrigeration system of a domestic refrigerator of 160 liters capacity, with R-134a by adopting different lengths of liquid line-suction line heat exchanger for domestic refrigerator. After conducting the experiments, the following conclusions are drawn. Net refrigerating effect is increased for different lengths of liquid line-suction line heat exchanger and at the length of heat exchanger of 32 cm is high for R134a is 145. Coefficient of performance is increased for different lengths of liquid line-suction line heat exchanger and at the length of heat exchanger of 32 cm it is maximum forr134a is 3.42 It is advantageous to provide a helical condenser at the inlet of the capillary tube and maintain the condenser pressureand the performance of vapour compression refrigeration system can be enhanced with the help of the helical condenser. Finally, it is concluded by change the shape of existing design to helical condenser the coefficient of performanceis increased and heat transfer rate is increased.

6 Acknowledgment I wish to express my gratitude to Dr.D.Y.Patil School of Engineering AcademyAmbi, Pune forproviding me necessecary support throughout this innovative project. Authoris also thankful to Prof.Nakhate and ganesh fabricators for providing me support in fabricating my project. References Y.S. Lee, and C.C. Su, Experimental studies oisobutene (R600a) as the refrigerant in domestic refrigeration system, Applied Thermal Engineering 22, pp , R. Cabello, E. Torrella, J. Navarro-Esbri, Experimental evaluation of a vapour compression plant performance using R134a, RR407C and R22 as working fluids, Applied Thermal Engineering 24 (2004).James M. Calm, Emissions and environmental impacts from air conditioning andrefrigerationsystems, International Journal of Refrigeration 25, pp , B.O.Bolaji, M.A. Akintunde, T.O. Falade, Comparative analysis of performance of three ozone-friends HFC refrigerants in a vapour compression refrigerator, Journal of Sustainable Energy and Environment 2 (2011) B.O.Bolaji, Selection of environment friendly refrigerants and the current alternatives in vapour compression refrigeration systems, Journal of Science and Management, Vol 1, No. 1 (2011) Samira Benhadid-Dib, and Ahmed Benzaoui, Refrigerants and their impact in the environment. Use of the solar energy as the source of energy, Energy Procedia 6,pp , James M. Calm, Emissions and environmental impacts from air conditioning and refrigeration systems, International Journal of Refrigeration 25, pp , B.O.Bolaji, M.A. Akintunde, T.O. Falade, Comparative analysis of performance of three ozone-friends HFC refrigerants in a vapour compression refrigerator, Journal of Sustainable Energy and Environment 2 (2011) B.O.Bolaji, Selection of environment friendly refrigerants and the current alternatives in vapour compression refrigeration systems, Journal of Science and Management, Vol 1, No. 1 (2011) Samira Benhadid-Dib, and Ahmed Benzaoui, Refrigerants and their impact in the environment. Use of the solar energy as the source of energy, Energy Procedia 6,pp , Ashish Kumar Paharia and Gupta R C, Effect of sub cooling and superheating on vapour compression refrigeration systems using r-22 alternative refrigerants. 3. BukolaOlalekanBolaji, Effects of Sub-Cooling on the Performance of R12Alternatives in a Domestic RefrigerationSystem. 4. Churchill S W (1977), Friction factorequation spans all fluid flow regimes, Chemical Engineering, Vol. 84, pp CP ARORA (2003), Refrigeration and Air Conditining. 6. Domkundhar and Domkundar, Refrigeration And Air conditioning. 7. Dalkilic A S and Wongwises S,A performance comparison of vapour compression refrigeration system using various alternative fuels. 8. Manohar Prasad, Refrigeration and Airconditining Systems. 9. Nagalakshmi K and MaruthiprasadYadavG, The Design and Performance Analysisof Refrigeration System Using R12 & R134aRefrigerants. Tiwari A C and ShyamkumarBarode, Performance Analysis of a Vapour Compression Refrigeration Systems Using Hydro-fluorocarbon Refrigerants. 11. Akintunde, M.A. 2004b. Experimental Investigation of The performance of Vapour Compression Refrigeration Systems.Federal University of Technology, Akure, Nigeria. 12. Kays WM, London AL. Compact heat exchangers. New- York: McGraw-Hill, Seshimo Y, Fujii M. An experimental study of the performanceof plate fin and tube heat exchangers at lowreynolds numbers. ASME/JSME Thermal Engineering Proceedings, ASME 1991;4: