Performance Analysis of Heat Pipe using Different Screen Mesh Sizes Manikandan.K * 1, Senthilkumar.R 2,

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1 Performance Analysis of Heat Pipe using Different Screen Mesh Sizes Manikandan.K * 1, Senthilkumar.R 2, 1, 2 Assistant Professor, Department of Mechanical Engineering, Annamalai University, India, Abstract Heat pipe is a passive heat transfer device which is used to remove the huge amount of heat from the heat source. The performance of the heat pipe is affected by various factors likely diameter, working fluid, wick structure, wick mesh size etc.in this work is to study the effect of wick mesh size on the performance of heat pipe with the various mesh sizes are 40, 60, 80, 100, 120 / square inch. Based on the experimental results, it is concluded that heat pipe with mesh size of 100 / square inch will have better performance than the other mesh sizes. Keywords: Heat pipe, mesh size, thermal efficiency, wick structure, thermal resistance I. INTRODUCTION The rapid and extensive development of technology over the electronic components leads the engineers to create a equipments with more efficiently and at very low costs. Due to this, an enormous amount of heat will be released with the reduction in size of equipments with more difficult specifications. So it is necessary to cool the electronic components as soon as possible and quickly, otherwise the electronic components are damaged. This leads to the development of heat pipe which is used to remove large amount of heat over a small temperature difference between two temperature limits. Amir faghri [1 ] defined that heat pipe was an passive device for radiating heat at a larger rate over a distance with small temperature drops between two temperature limits. Heat pipe comprises of three sections namely evaporator, adiabatic and condenser. The heat is supplied to the heat pipe in the evaporator section which converts the working fluid into vapour and returned to the condenser, due to capillary action of the wick structure. Yu-wei chang [2] utilised the heat pipe for cooling the electronic components and concluded that the evaporation resistance and condensation both increases with increase in heat input and decreases with filling ratio. Seok Hwan moon et al [3] implemented the concept of miniature heat pipe with wick material of woven to increase the cooling effect of notebook PC and showed that miniature heat pipe MHP cooling modules with wicks satisfies a demand condition of 0 to 100 C. Khalid Joudi et al [4] compared the performance of gravity assisted heat pipe with modified heat pipe with a separator in the adiabatic section. The results evidenced that modified heat pipe with separator is more efficient than gravity assisted heat pipe. Shinzo Shibayama and Shinichi Morooka [5] analysed both experimental and theoretical about the various limits such as capillary limit, maximum heat transfer limit of wick, friction loss and capillary properties. A. K. Mozumder et al [6 ] made an attempt to design, fabricate and test a miniature heat pipe with 5 mm diameter and 150 mm length with a thermal capacity of 10 W. Experiments were conducted with and without working fluid for different thermal loads to assess the performance of heat pipe. Finally the optimum liquid fill ratio is identified in terms of lower temperature difference, thermal resistance and higher heat transfer coefficient. Faghri et al [7] numerically analysed the transient and steady state performance of heat pipes with multiple heat sources and sinks. They concluded that the steady state of the heat pipe significantly changes with a change in the emissivity of the heat pipe wall and subsequently increases the power input in the evaporator section. Sun et al [8] the results implicated that a higher value of the capillary heat transport limit can be achieved when the heater placed symmetrically at the centre of the evaporator section as compared to the one side of the evaporator section. Patrik Nemec et al [ 9] made a detailed study about the working position of the heat pipe in both horizontal and vertical direction.they concluded that heat pipe can able to operate at both positions. Manikandan et al [10 ] analysed the effect of container diameter of heat pipe using Response Surface Methodology method to determine the optimal diameter. From that analysis the optimum diameter of heat pipe is 20 mm based on the thermal efficiency and thermal resistance.senthil kumar et al [11 ] analysed the heat pipe used in the energy conservation and waste heat recovery system. In their work, the heat pipe is fabricated with two layers of mesh size 80 /square inch and analysed the effect of using nanofluids in the heat pipe. K.N.Shukla et al [12] used four layered 100 mesh size copper screen to measure the thermal performance of cylindrical heat pipe using nanofluids and noticed that it is more improvement in the heat transfer coefficient. Ghanbarpour et al [13] used two layers of screen mesh wick of 150 ISSN: Page 220

2 mesh size to study the performance of heat pipe using silver nanofluids as a working fluid. They result showed that thermal conductivity is better at 60 angle of inclination. In the application point of view, heat pipe is used in the solar collector.tauofik brahim et al [14] used various screen mesh number in the heat pipe which is used in the solar collector and confirmed that heat pipe fabricated with two layers of screen mesh wick of mesh number 100 have increased the solar collector efficiency. Bhooomipagu et al [15] used copper screen mesh of 100 holes/square inch to generate capillary pressure in the square copper heat pipe. They compared the results thermal efficiency is better at 75% of filing ratio when water as a working fluid and 100% of filling ratio when Cuo as a working fluids. Senthil Kumar et al [16 ] used same two layers of stainless screen mesh of different mesh number of 60 square /inch to study the performance of heat pipe. The results showed that thermal efficiency was better at 45 for water and 60 for nanofluids. In this study, the thermal efficiency is compared with five different mesh size (40,60,80,100,120).The experiments were conducted with various heat input(30,40,50,60,70 W) and inclinations(15,30,45,60,75 ). heater which is placed over the evaporator section. The heat input is varied by means of autotransformer to get the desired the heat input. Every five minutes the surface temperature of heat pipe, inlet and outlet temperature of cooling water container is taken down until steady state prevails. Once it reaches steady state, the heat input is turned off and water is allowed to flow into the condenser jacket to cool down the heat pipe and make it ready for next experiment. The procedure is repeated for different number of mesh sizes, various heat inputs, angle of inclinations at constant filling ratio and flow rate. Fig. 1 The schematic diagram of heat pipe II. EXPERIMENTAL SETUP In this work five number of identical heat pipes are fabricated using copper as the container materials. Four layers of stainless steel mesh is used as the wick structures with different mesh sizes like 40, 60, 80, 100 and 120 holes/square inch. The experiment are conducted for various heat inputs (30,40,50,60&70) and angle of inclinations (15, 30, 45, 60& 75 ).The flow rate of coolant in the condenser section as kept as constant at 0.06 kg/min. Figure 1 shows the experimental setup diagram of heat pipe and figure 2 illustrates the thermocouple locations of the heat pipe. Copper tubes are used to fabricate the heat pipes and it is charged with working fluid. The heat pipe is charged with 85% of the evaporator volume which is required to saturate the wick.the working fluid used in this experiment is De-Ionized (DI) water. The thermocouples are used to measure the temperature of heat pipe surfaces (T-Type). Three numbers are placed over the evaporator section, four numbers are placed over the adiabatic section and three numbers are placed over the condenser section. In order to measure the thermal performance of the heat pipe, water jacket is placed over the condenser section and water is allowed to flow at a constant speed of 0.06 kg/min.the two more thermocouples are placed at the inlet and outlet of cooling water container to measure the coolant inlet and outlet temperature. The heat input is given to the heat pipe by means of electrical Fig. 2 The location of thermocouples III. RESULTS AND DISCUSSION 3.1. Effect of mesh size on thermal efficiency The thermal efficiency of the heat pipe is defined as the ratio of cooling capacity rate of water at the condenser section and the power supplied at the evaporator section.the thermal efficiency of heat pipe using DI water with different mesh size number are computed and compared in fig. 3-7 for various tilting angles and heat inputs. From all the figure from 3-7, it clearly indicates that the impact of inclination angle on the performance of heat pipe. When the angle of inclination increases, thermal efficiency seems to increase up to certain angle of 45 and afterwards it tends to decrease for all heat pipes.this is because gravitational force acts as major source for returning the working fluid between evaporator and condenser in addition to the capillary movement of wick structures. Therefore the heat pipe efficiency increases with increasing values of the angle of inclination. The thermal efficiency of the heat pipe increase with increase in the number of mesh size used for the capillary action of working fluid from all figures thermal efficiency tends to increase up to when the number of mesh size is 100 / square inch and afterwards it tends to decrease this is due to the ISSN: Page 221

3 fact that when the wick porosity increase it restricts the flow of condensate from the condenser to evaporator. Taoufiq brahim et al [14] also indicated that collector efficiency is mainly influenced by mesh number of heat pipe and number of fins. His results concluded that mesh number of 100 /square inch have resulted best thermal efficiency than with other mesh numbers for their configuration. When the heat input given to the heat pipe increases vice versa, heat will be generated more in the evaporator region. So that, the working fluid moves rapidly to the condenser section. As a result of that, more amount of heat is absorbed in the cooling area of the heat pipe which in turns increases the thermal efficiency. Fig. 5 Effect of mesh size on thermal efficiency at 50W Fig. 3 Effect of mesh size on thermal efficiency at 30 W Fig.6 Effect of mesh size on thermal efficiency at 60W Fig.4 Effect of mesh size on thermal efficiency at 40W Fig. 7 Effect of mesh size on thermal efficiency at 70 W 3.2. Effect of mesh size on Thermal resistance. The thermal resistance (TR) of the heat pipe is defined as ISSN: Page 222

4 where T e and T c are the average surface temperatures of the heat pipe at the evaporator section and the condenser section respectively and Q is the input power supplied to the heat pipe. Figures 8 to 12 show the comparative results of thermal resistance of heat pipe filled with DI water with different number of mesh size. It is clear that the thermal resistance of heat pipe decreases for all the different mesh size with its increasing values of angle of inclination and the heat input. From fig 8 to 11, the thermal resistance of heat pipe is low for mesh size is 100/square inch. More than 100 mesh size, the flow of condensate from condenser to evaporator is disturbed. So that other mesh,gives the high resistance than the 100 mesh,so that the thermal resistance is higher than the 100 mesh size. On the other hand, these thermal resistances fall quickly to its minimum value when the heat load is increased, because the heat input is increases to high value than the amount of vapour produced in the evaporator also increases. So that the vapour flows freely to the condenser. Due to this the thermal resistance decreases at higher loads. Fig. 10 Effect of mesh size on thermal resistance at 50W Fig. 11 Effect of mesh size on thermal resistance at 60 W Fig.8 Effect of mesh size on thermal resistance at 30W Fig. 12 Effect of mesh size on thermal resistance at 70 W IV. CONCLUSION Fig. 9 Effect of mesh size on thermal resistance at 40 W The heat pipes are fabricated and tested the effect of mesh sizes of wick structure. From this experimental analysis the following results are obtained. -The experimental results show that the performance of heat pipes depends on the parameters likely heat pipe diameter, screen mesh ISSN: Page 223

5 size used for wicks, inclination angle and heat input. -The heat pipe thermal efficiency is better at heat pipe fabricated with screen mesh number 100 holes/square inches. - the thermal resistance of the heat pipe is low when using screen mesh number of 100 holes/square inch than with other heat pipe fabricated with different mesh sizes. -The temperatures at adiabatic regime are almost uniform for all the experimentations. -The trial results reveal that the heat pipe efficiency tends to increase upto angle of inclination of 45 and after that gots reduced. ACKNOWLEDGEMENTS The authors thank the authorities of Annamalai University for providing the necessary facilities in order to accomplish this piece of work. References 1. Amir faghri, Heat pipes:review,opportunities and challenges, Frontiers in heat pipes,vol.5(1),pp.1-48, Yu-Wei Chang, Chiao-Hung Cheng,Jung-chang Wang,Sih-li hen, Heat pipe for cooling of electronic equipment,energy Conversation and management,vol.49,pp , Seok Hwan Moon,Gunn hwang,ho Gyeong yun,tae goo Choy,Young Kang, Improving thermal performance of miniature heat pipe for notebook PC cooling,microelectronics Reliability,vol.42,pp , Khalid A.Joudi,A.M.Witwit, Improvements of gravity assisted wickless heat pipes,energy conversion&management,vol.41,pp , Shinzo Shibayama and Shinichi Morooka, Study on a heat pipe,int. J. Heat Mass transfer, vol. 23,pp , A.K. Mozumder,A. F. Akon, M. S. H. Chowdhury and S. C. Banik, Performance Of Heat Pipe For Different Working Fluids And Fill Ratios, Journal of Mechanical Engineering, Vol. ME 41, No. 2,2010, Transaction of the Mech. Eng. Div., The Institution of Engineers, Bangladesh. 7. Faghri, A. Buchko, M. and Cao, Y. A Study of High Temperature Heat Pipes with Multiple Heat Sources and Sinks: Part I Experimental Methodology and Frozen Start up Profiles, Journal of Heat Transfer, vol.113, pp , K. H. Sun, C. Y. Liu and K. C. Leong, The Effective Length Of A Flat Plate Heat Pipe covered Partially By A Strip Heater On the Evaporator Section, Heat Recovery Systems & CHP,vol.15(4),, pp , Patrik Nemec, Alexander Čaja, Milan Malcho, Thermal performance measurement of heat pipe, Transaction on Thermodynamic and Heat Transfer, vol.2, pp , Kadamban Manikandan and Rathinasamy Senthilkumar, Optimization of Heat Pipe Container Diameter using Response Surface Technology, Australian Journal of Basic and Applied Sciences, vol.9 (36), pp , Dr. Senthilkumar R, Manikandan K, Velmurugan M, Study of Heat Pipes Using Nanofluids in Heat Recovery and Energy Conservation Systems, Advances In Natural and Applied Sciences,vol.10(4),pp , K. N. Shukla, A. Brusly Solomon, B. C. Pillai,B. Jacob Ruba Singh, S. Saravana Kumar, Thermal performance of heat pipe with suspended nanoparticles, Heat and Mass Transfer, vol.48,pp , M.Ghanbarpour,N.Nikkam,Rkhodabandeh,M.S.Toprak,(2 015), Thermal performance of inclined screen mesh heat pipesusing silver nanofluids, International communications in heat and mass transfer,vol.67, pp.14-20, Taoufik Brahim,Mohammed houcine dhaou,adbelmajid Jemni, Theoretical and experimental investigation of plate screen mesh heat pipe solar collector, Energy conversion and management,vol.87,2014,pp , Bhoomipagu Alankritha,P.Lakshmi reddy, Thermal performance of a square copper heat pipe for different volumes of Cuo nanofluid, International journal of innovative Research in science, engineering and technology,vol.4(8),pp , SenthilkumarR,Vaidyanathan S,sivaraman B, Effect of inclination angle in heat pipe performance Using copper nanofluid, Procedia engineering,vol.38,pp ,2012. ISSN: Page 224