The main aim is analysis the performance of pulsating heat pipe with open loop system. This design has effective to enhance the performance of heat pipe. The heat pipe having various limitations like capillary limit, boiling limit, entrainment limit, sonic limit etc. In this work, we analyze the overall heat transfer coefficient, heat transfer efficiency of the heat piper for different heat input and angle of variations. The work has been made with DI Water as working fluids. The performance of pulsating heat pipe tends to be better with heat pipe fabricated with 10mm size with Heat input of 50 W at angle inclination 45⁰

C. Kubendren

G. Elango

G. Senthilvel

M. Velmurugan

English

ZENODO

   8 Page 8-16 © MANTECH PUBLICATIONS 2019. All Rights Reserved  Journal of Thermal Engineering and Technology Volume 4 Issue 1      Investigation on Performance of Pulsating Heat Pipe  M. Velmurugan*, G. Senthilvel*, G. Elango*, C. Kubendren** Assistant Professor*, Professor** Department of Mechanical Engineering  Krishnasamy College of Engineering and Technology, Cuddalore, Tamilnadu Corresponding Author’s Email Id: vel642@gmail.com DOI: http://doi.org/ 10.5281/zenodo.2597255  Abstract The main aim is analysis the performance of pulsating heat pipe with open loop system. This design has effective to enhance the performance of heat pipe. The heat pipe having various limitations like capillary limit, boiling limit, entrainment limit, sonic limit etc. In this work, we analyze the overall heat transfer coefficient, heat transfer efficiency of the heat piper for different heat input and angle of variations. The work has been made with DI Water as working fluids. The performance of pulsating heat pipe tends to be better with heat pipe fabricated with 10mm size with Heat input of 50 W at angle inclination 45⁰.  Keywords: - Pulsating heat pipe, Angle of Inclination, Performance of Heat Pipes, Overall Heat Transfer coefficient.  INTRODUCTION Thermal management is the one of the most important parameter and its plays a vital role in a heat transfer device. Therefore, the design of efficient cooling system is important to increase system performance and reliability. Among other cooling techniques heat pipes have emerged as the most appropriate technology and cost effective thermal design solution due to its excellent heat transfer ability, high efficiency and simple in structure. Although the conventional heat pipes are various limitations of the performance of heat pipes, e.g. capillary limit, boiling limit, entrainment limit, sonic limit, and viscous limit. In both cases the limit will manifest itself by an unacceptable overheating of the evaporator due to lack of cooling working fluid (dry-out, burn-out). To overcome    9 Page 8-16 © MANTECH PUBLICATIONS 2019. All Rights Reserved  Journal of Thermal Engineering and Technology Volume 4 Issue 1      these difficulties the idea of pulsating heat pipes (PHPs) which work on principle of oscillation of the working fluid and phase change phenomenon in a capillary tube. Therefore, the purposes of this investigation are to study the heat transfer characteristics of a PHP and to find out the proper working fluids and other parameters for obtaining the optimum performance from a PHP by evaluating several issues related to its performance.   PULSATING HEAT PIPE The basic structure of PHP is small, lightweight, simple in structure and good efficiency. It consists of meandering capillary tubes having no internal wick structure arranged. In our work we selected open loop pulsating heat pipe. The closed passive system thus formed is evacuated and subsequently filled up partially with a pure working fluid, which distributes itself naturally in the form of liquid – vapor plug and slugs inside the capillary tube. Although a certain number of check valves have shown to improve the performance of the device. (See Figure:-1)  OPERATION OF PULSATING HEAT PIPE When a PHP is isothermal throughout, the liquid and vapor phases in the PHP exist in equilibrium at a saturation pressure corresponding to the fixed isothermal temperature. During operation, a temperature gradient prevails between the evaporator and the condenser, causing non-equilibrium pressure conditions. The heat transfer to the evaporator causes the bubbles in the evaporator to grow continuously and try to move at a higher pressure/temperature and a larger quality.  Figure 1 Schematic of open loop pulsating heat pipe    10 Page 8-16 © MANTECH PUBLICATIONS 2019. All Rights Reserved  Journal of Thermal Engineering and Technology Volume 4 Issue 1      This pushes the liquid column toward the low-temperature end (condenser). Simultaneously, the condensation at the other end will further enhance the pressure difference between the two ends, and forced to move at a lower pressure/temperature and a smaller quality. In this way a non-equilibrium state is formed between the driving thermal potentials and the system in return attempts to equalize the internal pressure.  Because of the inter-connection of the tube(s), the motion of the liquid slugs and vapor bubbles at one section of the tube towards the condenser also leads to the motion of slugs and bubbles in the other section towards the high temperature (Evaporator) in the next section. This works as a restoring force. The inter-play between the driving force and restoring force leads to oscillation of the vapor bubbles and liquid slugs in the axial direction. Further, inherent perturbations present in real systems augment pressure Fluctuations in the system .Unlike conventional heat pipes, no steady-state pressure equilibrium can be achieved for an operating PHP. The frequency and amplitude of the oscillations are expected to depend on the heat flow rate and the mass fraction of the liquid in the tube. Through these oscillations, heat which is supplied by the heat source at the evaporator is carried to the condenser and is removed by a heat sink.  PULSATING HEAT PIPE DESIGN In our design we use copper pipe is a material because of high thermal conductivity. The pulsating heat pipe with diameter of 10mm and divide into three areas. For evaporator area 300 mm, condenser area 300mm and adiabatic section 600mm.in this setup we measure temperature in 12 different points. The experiments were conducted in a heat pipe for a 30, 40, 50, 60 & 70 W heat input and 80 ml/min flow of water in condenser side and constant filling ratio of 75% of evaporator volume. The performance test on the heat pipe was conducted for the above mentioned conditions for 0o, 15⁰, 30o, 45°, 60o, 75°and 90o inclinations of heat pipe   Figure:-2 View of Pulsating Heat Pipe Kit      11 Page 8-16 © MANTECH PUBLICATIONS 2019. All Rights Reserved  Journal of Thermal Engineering and Technology Volume 4 Issue 1      RESULTS AND DISCUSSION  The pulsating heat pipe is a device that efficiently transports heat from one end to another. It utilizes the latent heat of the vaporized working fluid instead of the sensible heat. The two-phase heat transfer mechanism results in heat transfer capabilities from one hundred to several thousand times that of an equivalent well known conductor such as copper. Heat transmitted through a pulsating heat pipe is based on phase change it can be pointed out that using a PHP with similar dimensions of a solid metal pipe, larger the amounts of heat transfer will be obtained.  In this work, the pulsating heat pipe with two numbers of mesh layers are fabricated and tested under different heat inputs and different inclinations. The thermal efficiencies of pulsating heat pipe are calculated. The working fluids used in this analysis are DI water.  The experiments were conducted in a pulsating heat pipe for a 30, 40, 50, 60& 70W heat input and 80 ml/min flow of water in condenser side and constant filling ratio of 75% of evaporator volume. The performance test on the pulsating heat pipe was conducted for the above mentioned conditions for 0o, 45°and 90o inclinations of heat pipe Variations of thermal efficiency The thermal efficiency is calculated from the ratio between the cooling capacity rates of water at the condenser section to the power supplied at the evaporator section. Fig 3 to 10 shows the variations of thermal efficiency for various heat inputs and angle of inclinations. From all the figures, the efficiency increases with increasing values of the angle of inclination up to 45°, afterwards it tends to decrease. This is due to the fact that the gravitational force has a significant effect on the flow of working fluid between the evaporator section and the condenser section. Also the thermal efficiency of the heat pipe increases with increasing heat flux, due to the fact that the temperature difference between the evaporator and condenser sections increases which results in higher evaporation heat transfer rate of working fluid. At higher heat input in the evaporator section, the heat transfer from its surface to the working medium is higher and it causes the working medium which is in the form of vapor to move vigorously into the condenser section. The cooling water in the condenser absorbs this excessive heat and as a result the efficiency of the heat pipe increases. At the optimum condition (45° tilting angle) this results in maximum heat pipe thermal efficiency.     12 Page 8-16 © MANTECH PUBLICATIONS 2019. All Rights Reserved  Journal of Thermal Engineering and Technology Volume 4 Issue 1       Figure 3 shows the heat input (w) vs. thermal efficiency (%) for 0⁰   Figure 4 shows the heat input (w) vs. thermal efficiency (%) for 45⁰   Figure 5 shows the heat input (w) vs. thermal efficiency (%) for 90⁰  384042444648505230W 40W 50W 60W 70WThermal efficiency,%heat input,W2728293031323334353630W 40W 50W 60W 70WThermalefficency,%heat input,W0510152025303540455030W 40W 50W 60W 70WThermal efficiency,%Heat input,W   13 Page 8-16 © MANTECH PUBLICATIONS 2019. All Rights Reserved  Journal of Thermal Engineering and Technology Volume 4 Issue 1       Figure 6 shows the angle of inclination (⁰) vs thermal efficiency (%) for 30W   Figure 7 shows the angle of inclination (⁰) vs thermal efficiency (%) for 40w   Figure 8 shows the angle of inclination (⁰) vs thermal efficiency (%) for 50w 0510152025303540450 15 30 45 60 75 90Thermal efficiency,%Angle of inclination,degree051015202530354045500 15 30 45 60 75 90Thermal efficiency,%Angle of inclination,degree010203040500 15 30 45 60 75 90Thermal efficiency,%Angle of inclination,degree   14 Page 8-16 © MANTECH PUBLICATIONS 2019. All Rights Reserved  Journal of Thermal Engineering and Technology Volume 4 Issue 1       Figure 9 shows the angle of inclination (⁰) vs thermal efficiency (%) for 60w   Figure 10 shows the angle of inclination (⁰) vs thermal efficiency (%) for 70w  CONCLUSIONS In this work attempt has been made with DI Water as working fluids. In the performance of pulsating heat pipe the thermal efficiency tends to be better with heat pipe fabricated with 10mm size. Heat input at 50 W at angle inclination 45⁰. From the experimental investigation the following salient points also arrived.  The heat transfer efficiency got reduced, when the heat pipe is inclined above 45⁰.   The temperatures at adiabatic regime are almost uniform for all the experiments.  01020304050600 15 30 45 60 75 90Thermal efficiency,%Angle of inclination,degree01020304050600 15 30 45 60 75 90Thermal efficiency,%Angle of inclination,degree   15 Page 8-16 © MANTECH PUBLICATIONS 2019. All Rights Reserved  Journal of Thermal Engineering and Technology Volume 4 Issue 1       The variation of the super heat temperature is almost linear irrespective of heat input, angle of inclination and flow rate of cooling medium.   The steady state temperature of heat pipe at 50 W is higher than others.   The evaporator temperature distribution also follows the uniform pattern for all the heat input and inclination.  The experiments showed that pulsating heat pipe can be operated effectively with various heat input. The heat pipe based passive system can provide reliable and effective thermal control for energy conservation, energy recovery and renewable energy application.  REFERENCES I. Journal of Electronics Cooling & Thermal Control (2013), “Experimental Studies on Thermal  Performance of a Pulsating Heat Pipe with DI water”,Bhawna Verma, Vijay Lakshmi Yadav, Kaushal Kumar Srivastava.  II. Heat and Mass Transfer (2012), “Thermal performance of an open loop closed end pulsating heat pipe”,Manabendra Saha, C.M Feroz, F.Ahmed, T.Mujib.  III. Proc.5th Minsk International Seminar (Heat Pipes, Heat Pumps and Refrigerators), Minsk, Belarus, 2003, “On the definition of pulsating heat pipes: An Overview”, Sameer Khandekar and Manfred Groll.  IV. “Characteristics of an Open Loop Pulsating Heat Pipe”,Roger R. Riehl.  V. 13th International Heat Pipe Conference, “Closed loop and Open loop pulsating heat pipes”, Sameer Khandekar, Manfred Groll, P. Charoensawan, S. Rittidech, P. Terdtoon. Pulsating Heat Pipe based heat exchanger, Sameer Khandekar.   VI. International Journal of Heat and Mass Transfer, “A novel design of pulsating heat pipe with fewer turns applicable to all orientations”, Kuo-Hsiang Chien,Yur-Tsai,Yi-Rong Chen,Kai-Shing Yang,Chi-Chuan Wang.      16 Page 8-16 © MANTECH PUBLICATIONS 2019. All Rights Reserved  Journal of Thermal Engineering and Technology Volume 4 Issue 1      VII. International Journal of Heat and Mass Transfer, “ Chaotic behavior of pulsating heat pipe”, Yanxi Song, Jinliang Xu.International Journal of Heat and Mass Transfer, “Chaotic behavior of pulsating heat pipes”, Yanxi          Song, Jinliang Xu.  VIII. The 7th International Conference on Applied Energy-ICAE2015,“Experimental investigations on   pulsating heat pipe”, Harshal Gamit, vinayak More, Bade Mukund, H.B. Mehta.  IX. International Conference on Computational Science, ICCS 2012, “Modelling of A Pulsating Heat Pipe and Startup Asymptotics”, Xin-She Yang, Tao Luan.         Cite this Article M. Velmurugan, G. Senthilvel, G. Elango, C. Kubendren (2019). Investigation on Performance of Pulsating Heat Pipe Journal of Thermal Engineering and Technology, 4(1), 8- 16 http://doi.org/10.5281/zenodo.2597255  

Investigation on Performance of Pulsating Heat Pipe

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Investigation on Performance of Pulsating Heat Pipe

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