Papers by Keyword: Heat Pipe

Abstract: This work presents a theoretical and experimental analysis of a heat exchanger assisted by five heat pipes made of copper with a metallic mesh 100 of stainless steel which was used as capillary structure. All heat pipes used water as the working fluid and were designed based on the capillary limit model. The heat pipes were developed and tested under heat loads varying from 20 to 50 W before application into the heat exchanger. The theoretical and experimental results were compared and all heat pipes worked satisfactorily. Thereafter, it is presented the development of heat pipe heat exchanger which was tested under heat loads varying from 100 to 250 W. The highest temperature measured on the external surface of the heat pipes was 90 oC and the heat exchanger thermal efficiency varied from 74 to 80%. It is showed that the use of a stainless steel mesh as a porous wick was proved to work successfully in heat pipes.

Abstract: Heat pipe has excellent conductivity of heat and diversity of structure, so it can be used in machining which can decrease or avoid using the cutting fluid. In this paper, the abrasive tool with rotating heat pipe was designed. To validate that the abrasive tool with heat pipe can safely and steadily grind materials, the model analysis of abrasive tool with heat pipe is carried on with the ANSYS software based on the theory of modal analysis, then the first five order natural frequency and vibration models are to get. The results indicated that the vibrational frequency of designed abrasive tool is far away from natural frequency, so resonance phenomenon does not happen and the abrasive tool with heat pipe can smoothly work.

Abstract: The aim of this paper is to investigate the effect of nanofluid on the heat transfer performance of heat pipe and to examine the difference of the thermal conductivity between pure water heat pipes and nanofluid heat pipes. In our experiments, Al₂O₃-water nanofluid and pure water were used as working fluids respectively in gravity-assisted heat pipes. Effects of filling ratio and heating temperature on the thermal performance of heat pipe were investigated. The thermal resistance of heat pipe was analyzed. Our results showed that nanofluid can significantly increase the heat transfer coefficient and enhance the thermal performance of heat pipe.

Abstract: Heat pipe has excellent conductivity of heat and diversity of structure, so it can be used in machining which can decrease or avoid using the cutting fluid. In this paper, the abrasive tool with rotating heat pipe was designed. To validate that the abrasive tool with heat pipe can safely and steadily grind materials, the structure of abrasive tool was finite element analyzed which included static analysis. Furthermore, the heat transfer performance of heat pipe was tested. The results indicated that heat pipe has certain cooling impacts relative to no heat pipe in machining.

Abstract: LED has been regarded as the next generation lighting source. As for high power LED lamps, heat accumulation will cause a series of problems. Therefore, thermal management is very important for designing a high power LED lamp. Three types of heat sinks are designed by using the finite element analysis (FEA) method for an 180W high power LED lamp. Then the optimized heat sinks are developed and experiments are performed to demonstrate the simulated results. At the same time, the thermal performances with different working angles are investigated experimentally. The heat sink with heat pipe has a better heat dissipation performance than the conventional heat sink under the same input power. The working angles of the lamps greatly influence the thermal performance of each heat sink. For the same heat sink, the temperature varies with different install directions and working angles. Finally, the heat sink with the best thermal performance is recommended. The results have practical significance in designing high power LED lamps.

Abstract: The objective of the present study is to investigate the performance of solar collector with serpentine shape of heat pipe and water-ethanol as a working fluid. Serpentine shape is easy of manufacturing and also to reduce cost of manufacturing. In this work, heat pipe is made from copper tube having ID 10mm and OD 12mm.The tube is bent in serpentine manner and filled with Water-ethanol as a working fluid with 70% filling ratio. The length of evaporator, adiabatic and condenser section was 480mm, 50mm and 65mm respectively. The test is conducted for coolant flow rate 4.5 kg/hr different angle of collector 20°, 31.5°, 40°, 50°, 60°. Result shows that water-ethanol collector gives better performance than collector with water as a working fluid. Maximum efficiency is observed at 31.5° inclination.

Abstract: This experimental study finds the effect of condensation on the thermal performance of heat pipe. Condensation heat transfer rate, heat transfer coefficient and variation of temperature over the heat pipe are measured at vertical and horizontal position of HP, by varying the steam-to-surface temperature difference. It is found that the condensation heat transfer rate for vertical position of heat pipe with CuO nanofluid is 2.07 times higher than the horizontal position, whereas the increase in heat transfer coefficient is 1.94 times. Using CuO nanofluid instead of deionized water in the heat pipe enhances the heat transfer rate and heat transfer coefficient by 1.25 and 1.42 times respectively for the vertical orientation.

Abstract: This study aims to investigate the influence of inclination angle and concentration of nanoparticles on the improvement in heat pipe thermal efficiency. Spherical shaped, 40 nm size CuO nanoparticles are used in this study and its physical and thermal chracteristics are investigated. The results are compared with a heat pipe using DI water at horizontal position.The thermal efficiency is improved by increasing the tilt angle and mass of particles dispersed in DI water. The improvement in thermal efficiency obtained are 20.59, 35.92 and 32.57% respectively for 0.5, 1.0 and 1.5 wt% of CuO nanofluids and 60° inclination angle.

Abstract: The two-phase flow through porous media is an important topic which spans a broad spectrum of engineering disciplines especially in porous heat pipes. Heat pipe is a thermodynamic device that transports heat energy from one location to another with a negligible temperature drop. The aim of the present work is to investigate the phase change mechanisms, namely boiling and condensation, in the flat heat pipe system with different orientation. Governing equations used for the formulation are continuity, mixture momentum, liquid conservation and energy equations. These equations are converted into three ordinary differential equations using similarity transformation and two-phase similarity solutions are obtained for both boiling and condensing flows. In each case, a two phase zone where the liquid and vapour can coexist appears adjacent to the wall. As the heat transfer at the wall gradually enhances, the liquid saturation at the wall approaches to the limiting value, zero, for boiling and unity for condensation. The present work is an attempt to predict numerically the liquid wall saturation, non-dimensional temperature, non-dimensional temperature gradient and effect of Sherwood number during the phase change of water-steam system in the heat pipe for horizontal and vertical cases. Nomenclature

Abstract: Nanofluid is nanomaterial suspended in base fluid. Nanoparticle enhances various properties of base fluid mainly heat transfer characteristics. Also sometime nanoblends means hybrid nanofluid is used. This article mainly states how nanofluids are formed from nanoparticle and there types. This paper reviews and summaries the recent work in experimental and theoretical heat transfer characteristic of nanofluid as well as nanoblends and it is helpful in identifying the nanofluid that can be used in heat pipe for further research.