Experimental Investigation of Effect of Electro Hydrodynamic Effect on Performance of Refrigeration System with R-134A

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1 IJIRST International Journal for Innovative Research in Science & Technology Volume 3 Issue 02 July 2016 ISSN (online): Experimental Investigation of Effect of Electro Hydrodynamic Effect on Performance of Refrigeration System with R-134A Miss. R. R. Kadam PG Student Department of Mechanical Engineering Dr. J.J. Magdum College of Engineering, Jaysingpur, Shivaji University, Kolhapur, India Prof. P. R. Kulkarni Professor Department of Mechanical Engineering Dr. J.J. Magdum College of Engineering, Jaysingpur, Shivaji University, Kolhapur, India Abstract Effects of applied of EHD on the performance of vapour compression refrigeration system are experimentally investigated to present applicability of the EHD technique. In the experimental work the condenser section is modified only. The refrigerant is cooled by dielectric fluid (transformer oil). Tests were performed at LPH of refrigerant flow and at different electrical field strengths (0-250 V), while average saturation temp was 54 C and 6 C. Experimental results demonstrate a remarkable potential in utilizing EHD to enhance condensation heat transfer. It is concluded that the enhancement is driven by the effective removal of the condensate through EHD induced liquid extraction and dispersion phenomena. For the presence of the electrodes, the experimental results indicate that the maximum heat transfer rate obtained is kj/sec and COP actual obtained is 4.98 which is 3 to 4 times more than without the EHD effect. This technique can be utilised effectively to the refrigeration system to have better COP and also size of condenser as well as evaporator can be varied. Keywords: Condensation heat transfer, COP, Electrical field strengths, Electrodes, Electro hydrodynamic I. INTRODUCTION Enhancing of heat transfer coefficient is an interesting area for both industry and academia. Achieving higher heat transfer rates through various enhancement techniques results in protection of our environment. This is done through substantial energy saving, due to both increasing of equipment performance, and designing of smaller systems to meet required loads. Electro hydrodynamic effect as an active technique for enhancing heat and mass transfer, with a focus on industrial applications, especially for evaporators and condensers. As phase change phenomena of boiling and condensation are very important mode in heat transfer, improvement on enhancing heat transfer in both evaporators and condensers are highly required. Heat exchangers are widely used for efficient heat transfer from one medium to another. Heat exchangers are those devices that facilitate the exchange of heat energy between two fluids that are at different temperatures while keeping them from mixing with each other. A double pipe heat exchanger has two concentric pipes. Heat exchange takes place through the tube walls between a first fluid (hot fluid) within the tubes and a second fluid (cold fluid) outside them, through annulus region, within the casing. Heat exchangers are used in different processes ranging from conversion, utilization & recovery of thermal energy in various industrial, commercial & domestic applications. Some common examples include steam generation & condensation in power & cogeneration plants; sensible heating & cooling in thermal processing of chemical, pharmaceutical & agricultural products; fluid heating in manufacturing & waste heat recovery etc. Increase in Heat exchanger s performance can lead to more economical design of heat exchanger which can help to make energy, material & cost savings related to a heat exchange process. II. THEORY Electrohydrodynamics: The electrohydrodynamic (EHD) effect is the effect in the interaction of electric fields and flow fields in a dielectric fluid medium is involved. This interaction may result in electrically induced pumping, mixing, or enhancement of heat transfer. The general mathematical expression (Landau & Lifshitz) of the electric body force is, fe = ρ ce 1 2 E2 ϵ [E2 ρ ( ϵ ) T] (1) ρ Where, ρc =electric field space charge density, E = applied electric field strength, ε = dielectric permittivity of the fluid, ρ = mass density, and T = temperature. The three terms on the right-hand side of Eq. (1) represent the electrophoretic, dielectrophoretic, and electrostrictive components of the electric force respectively. All rights reserved by 326

1) The electrophoretic component represents the force which acts on the free charge in the presence of an electric field. It is also known as the Coulomb force.

2 1) The electrophoretic component represents the force which acts on the free charge in the presence of an electric field. It is also known as the Coulomb force. This Coulomb force usually dominates over other two forces under the application of direct current in dielectric fluid medium. 2) The dielectrophoretic component represents the force which is due to the spatial change of the permittivity of the dielectric fluid medium as a result of temperature gradients and/or differences. The dielectrophoretic force is weaker than the electrophoretic force as the permittivity of the working fluid is a weak function of the electric field. 3) The electrostrictive component represents the force caused by the inhomogeneous electric field strength and the variation in dielectric constant with density and temperature. Coulomb force has dominant effect, among these forces, in electrohydrodynamic and other two forces are neglected in EHD effect. Thus, interaction of electric field with dielectic fluid medium may set up a mechanical body force which may be useful in various applications such as heat transfer controlling, liquid film pumping, electronic device cooling, etc. In this technique, an electric field characterized by a high voltage and low current is applied to the fluid. III. EXPERIMENTAL SETUP An experimental set-up has been designed and fabricated for the investigation of effect of electro hydrodynamic effect on performance of refrigeration system with R-134a. A schematic diagram of the experimental set-up is shown in Figure. Experimental setup consists of the vapour compression cycle i.e. refrigeration tutor. The cycle consists of main four components compressor, condenser, thermostatic expansion valve, evaporator with pressure measurement gauges, and four temperature measurement thermo couples which gives condenser inlet & outlet condition and evaporator inlet & outlet condition. Also receiver and drier are used. In the system hermetically sealed compressor with cooling fan is used having 1/3 ton capacity. Evaporator is coil type with water cooled having size of pipe diameter 13.4 mm and 50foot. OD of coil is 190 mm. This coil is inserted in a tank of size 300 X 300 X 400 mm. The test section is consists of condenser is coil type with transformer oil cooled having size OD of coil is 190 mm, 23 number of turns and total length of copper pipe is 80 foot. It is placed in a tank having size 300 X 300 X 400 mm. Transformer oil heated by the heat rejected by refrigerant in condenser pipe has to be cooled. For this purpose another water cooled heat exchanger is used. The water coming out of evaporator section is re-circulated in it. Heat exchanger is a tank having size 250 X 250 X 320 mm. transformer oil is circulated by a 1/ 2 HP centrifugal regenerative pump which is self-primed. Electro hydrodynamic effect is applied to condenser through DC power source. DC power source is made by autotransformer and rectifier unit. For the investigation purpose, the condenser section is modified to apply the electric field. The condenser coils are depeed in dielectric fluid. Two electrodes are immersed in the dielectric fluid and these electrodes are connected to dimmer stat to vary the intensity of electric field in dielectric fluid medium. The secondary heat exchanger is used to cool the dielectric fluid and again it is allowed to flow towards dielectric fluid reservoir. Electrodes are made from the copper plate of size 30 X 300 mm and connection is given from the rectifiers.for the measurement of pressure of high side and low side two pressure gauges are used. High side pressure gauge has range of 0-20 kg/cm 2 and low side pressure gauge has range 0-14 kg/cm 2. For temperature measurement total 9 chromel-alumel thermocouple is used which has the temperature range of C.In the control panel energy meter, ammeter, dimmer stat, temperature indicator, on and off switches is used. For mass flow rate measurement rotameter is used having range of 0 to 60 LPH. Fig. 1: Experimental set- up All rights reserved by 327

3 IV. EXPERIMENTATION ON TEST SECTION 1) Connect the water supply to the evaporator and secondary heat exchanger. Adjust the water flow rates. Start the pump it will supply transformer oil to the condenser section adjust the flow rate of it. 2) Switch ON the main supply. Switch ON the compressor. Within about half an hour confirm the steadiness of the temperatures. If temperatures have reached steady state note down all the readings and complete the observation table. 3) Initially experiment is carried out without the electro hydrodynamic effect and readings are taken. Reading for temperature, pressure, mass flow rate is noted on the basis of it calculations are done. 4) Now supply electric current (DC) to wire electrodes (which are not shown in the figure) and adjust voltage with the help of dimmerstat and repeat step (3). This will give the coefficient of performance of the system with application of electro hydrodynamic effect. Different readings are taken by varying voltage with the help of dimmerstat and calculate the coefficient of performance of the system. 5) Every test has to be run under constant mass flow rate, and at steady state condition, with or without the electric field. 6) Take the readings and we will check the effect of different input voltage on the performance of heat exchanger. V. RESULTS AND DISCUSSION Using the data obtained from experiments, various COPS, heat transfer rate, compressor work, and heat transfer coefficient of refrigeration system is discussed in following subsections. Effect of EHD on Theoretical COP of Refrigeration System: Fig. 1: Comparison between Theoretical COP with and without EHD effect. Graph shows that for without application of the EHD effect the theoretical COP has variations from 3.8 to 5.4 and if the EHD application is done then theoretical COP varies from 4.8 to 5.9. Also by observing the graph of with EHD effect, it seems that as the voltage increases from 50 V to 250 V the COP value also increases gradually this is due the dissociation of the molecules in the fluid due to application of EHD. All rights reserved by 328

Effect of EHD on Actual COP of Refrigeration System: Fig. 2: Comparison between Actual COP with and without EHD effect Graph gives variation of the Actual COP V/S applied voltage.

This variation is due to increase in the heat transfer by refrigerant to the transformer oil in the condenser section.

4 Effect of EHD on Actual COP of Refrigeration System: Fig. 2: Comparison between Actual COP with and without EHD effect Graph gives variation of the Actual COP V/S applied voltage. Also it compares with and without EHD effect on the system. Under application of EHD as the voltage increases the actual COP increases from value 1.5 to 5. This variation is due to increase in the heat transfer by refrigerant to the transformer oil in the condenser section. As the voltage increases dissociation of the molecules increases which forms the secondary flow in the system. In comparison to without EHD affect results the COP is more with the EHD effect. In normal operation the COP obtained is 1 to 2. Effect of EHD on Overall Heat Transfer Coefficient: Fig. 3: Relation between overall heat transfer coefficients to the applied voltage Graph shows the effect of EHD on the overall heat transfer coefficient. It can be observed that overall heat transfer coefficient for without application of EHD is varies from 280 to 420 W/m2 K and that compared with the application of EHD then values are up to 1100 W/m2 K. this increases is due to the voltage variation in the transformer oil which forms the fluid motion in it which increases the heat transfer. All rights reserved by 329

Effect of EHD on Heat Transfer Rate: Experimental Investigation of Effect of Electro Hydrodynamic Effect on Performance of Refrigeration System with R-134A Fig.

It seen that for the same mass flow rate of refrigerant the heat transfer rate is increased as compared to the without EHD operation.

5 Effect of EHD on Heat Transfer Rate: Experimental Investigation of Effect of Electro Hydrodynamic Effect on Performance of Refrigeration System with R-134A Fig. 4: Relation between heat transfer rate and mass flow rate of refrigerant Graph gives the variation of heat transfer rate due to application of the EHD effect. It seen that for the same mass flow rate of refrigerant the heat transfer rate is increased as compared to the without EHD operation. From above graph, the heat transfer rate (Q) of double pipe heat exchanger without EHD effect is lower than that EHD effect. This is because in the absence of electric field, there is no any dissociation of molecules. But under the influence of electric field, fluid flow rate increases due to increase in electrical body force (fe). Hence, as the strength of electric field increases, heat transfer rate of heat also increases rapidly. Effect of EHD on Compressor Work: Fig. 5: Relation between the compressor work and mass flow rate of refrigerant Graph gives variation of compressor work with the application of EHD. It seems that for without application of EHD compressor work is more and as we apply the EHD effect to the system then compressor work decreases for the same mass flow rate of refrigerant. The EHD effect causes the sub cooling of the refrigerant in the condenser which reduces work required to run the compressor. The more voltage can cause more reduced compressor work of the system, which results in increased COP of the system. All rights reserved by 330

6 VI. CONCLUSIONS Experimental study of vapour compression refrigeration system was performed using with and without electro hydrodynamic (EHD) effect. The results will show comparison between with and without electro hydrodynamic (EHD) on the performance of vapour compression refrigeration system. The effects of parameters such as Heat transfer rate, Overall heat transfer coefficient, coefficient of performance on the heat transfer were studied with and without EHD effect. The conclusions from experimentation work are drawn as follows, 1) In vapour compression refrigeration cycle, to obtain effective heat exchange in condenser high voltage power supply is required. The proper flow of transformer oil with high voltage power can enhance heat transfer rate in the condenser. 2) The electro hydrodynamic effect causes more temperature drop at outlet of the condenser which results in decreased compressor work requirement and increases COP of the system. 3) It is found that as the heat transfer rate increases; overall heat transfer coefficient also increases for electro hydrodynamic (EHD) effect on the performance of vapour compression refrigeration system as the voltage increases. When voltage across electrode increases, dissociation of ions dielectric fluids also increases. This increase flow rate which is responsible for heat transfer enhancement. 4) The heat transfer rates for EHD effect on the performance of vapour compression refrigeration system were 5-15% higher than the without EHD effect heat exchanger. Improved heat transfer rates will ultimately allow smaller size and smaller mass flow rate of refrigerant in the condenser. 5) From comparative experimental analysis, it is found that the coefficient of performance of the vapour compression refrigeration system with EHD effect is 3 to 4 times higher than that without EHD effect. REFERENCES [1] Hamid Omidvarborna, Arjomand Mehrabani-Zeinabad, Mohsen Nasr Esfahany Effect of electrohydrodynamic (EHD) on condensation of R-134a in presence of non-condensable gas International Communications in Heat and Mass Transfer 36 (2009) [2] Taveewat Suparos, Heat Transfer Enhancement of Refrigeration System Under Electric Field Proceeding of HT2005 ASME Summer Heat Transfer Conference July 17-22,2005, Francis Hotel, San Francisco,CA,USA [3] H. Sadek, A.J. Robinson, J.S. Cotton, C.Y. Ching, M. Shoukri, Electrohydrodynamic enhancement of in-tube convective condensation heat transfer, International Journal of Heat and Mass Transfer 49 (2006) [4] Suriyan Laohalertdecha, Somchai Wongwises, Effect of EHD on heat transfer enhancement during two-phase condensation of R-134a at high mass flux in a horizontal smooth tube [5] Suriyan Laohalertdecha, Somchai Wongwises, Effects of EHD on heat transfer enhancement and pressure drop during two-phase condensation of pure R-134a at high mass flux in a horizontal micro-fin tube, Experimental Thermal and Fluid Science 30 (2006) [6] Jamal Seyed-Yagoobi, Electrohydrodynamic pumping of dielectric liquids, 19 March 2005, Journal of Electrostatics 63(2005) [7] L. Léal, M. Miscevic,P. Lavieille, M. Amokrane, F. Pigache, F. Topin, B. Nogarède, L. Tadrist d, An overview of heat transfer enhancement methods and new perspectives: Focus on active methods using electroactive materials, International Journal of Heat and Mass Transfer 61 (2013) [8] M. Al Shehhi, S. Dessiatoun, A. Shooshtari1, M. Ohadi, and A. Goharzadeh, Electrohydrodynamic (EHD)-Enhanced Separation of Fine Liquid Droplets from Gas Flows - Application to Refrigeration and Petro-chemical Processes, The Second International Energy 2030 Conference, Abu Dhabi, U.A.E., November 4-5, 2008, [9] Chuntian Chen, Jiaxiang Yang, Qiujia Zhang, Jing Li, Study of EHD Effect on Enhanced Condensation heat transfer of dielectric fluid, Conference Record of the 2004 IEEE Intemational Symposium on Electrical Insulation, Indianapolis, IN USA, September 2004, ( /04/$ IEEE.) [10] CHEN Xiaopeng, CHENG Jiusheng & YIN Xiezhen, Advances and applications of electrohydrodynamics, Chinese Science Bulletin 2003 Vol. 48 No , 11 June [11] M. Mirhosseini1, A.A. Alemrajabi, Effect of ehd on forced convection in a tube by using helical electrode, SET2011, 10th International Conference on Sustainable Energy Technologies, İstanbul, TÜRKİYE, 4-7 Sep [12] H. El-kashef, O.ElShanwany, Laser interferometric study of the physical properties of transformer oil, Optics & Laser Technology vol 44, year [13] Sid Ahmed ould Ahmedou, Michel Havet, Effect of process parameters on the EHD airflow, 15 February 2009, Journal of Electrostatics 67 (2009) [14] L. Léal, M. Miscevic, P. Lavieille, M. Amokrane, F. Pigache, F. Topin,B. Nogarède L. Tadrist, An overview of heat transfer enhancement methods and new perspectives: Focus on active methods using electroactive materials, 8 March 2013, International Journal of Heat and Mass Transfer 61 (2013) [15] Dr S. S. Banwait, Dr. S. C. Laroiya, Properties of refrigerant and psychometric tables and charts in S.I. unit, and ISBN: [16] Manohar Prasad, Refrigeration and air conditioning data Book, ISBN X All rights reserved by 331

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