Thermal Behavior Analysis of Wire Mini Heat Pipe

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Kleber Vieira de Paiva ◽  
Marcia Barbosa Henriques Mantelli ◽  
Leonardo Kessler Slongo
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Design Parameters ◽  
Working Fluid ◽  
Diffusion Welding ◽  
Flat Plates ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Heat Transfer Capacity ◽  
Microgravity Conditions

This work presents a theoretical and experimental analysis of a copper mini heat pipe (MHP), fabricated from a sandwich formed between cylindrical wires and flat plates, which are welded by means of diffusion process. The edges formed between the wires and the plates provide the working fluid capillary pressure necessary to overcome all the pressure losses. Two different experimental set ups were developed: one for test in gravity (laboratory) and other for microgravity conditions (International Space Station—ISS). The main difference between them lies in the condenser section. In the laboratory, cooling water was used to remove heat from the mini heat pipe, while at the ISS, fins and air fan were employed. In gravity, three different working fluids were tested: water, acetone, and methanol, while, for the experiments at the ISS, just water was used. A model was developed to predict the maximum heat transfer capacity of the device. In comparison to the literature models, the main difference of the present model is the variation of contact angle to adjust the mathematical model. Therefore, the main contributions of the present work are development of wire plate mini heat pipe fabrication methodology using diffusion welding, improvement of the analytical model used to predict the maximum heat transfer capacity of the device, determination of the present technology optimum design parameters, and test data obtained under microgravity conditions.

Optimization of Wettability Gradient for Enhancement of Thermal Performance of Micro Heat Pipes

2018 ◽  
Author(s):  
Manjinder Singh ◽  
Naresh Varma Datla ◽  
Supreet Singh Bahga ◽  
Sasidhar Kondaraju
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Variable Mass ◽  
Working Fluid ◽  
Maximum Heat ◽  
Continuous Increase ◽  
Maximum Heat Transfer ◽  
Integration Density ◽  
Heat Transfer Capacity ◽  
Micro Heat Pipes

Continuous increase in the integration density of microelectronic units necessitates the use of MHPs with enhanced thermal performance. Recently, the use of wettability gradients have been shown to enhance the heat transfer capacity of MHPs. In this paper, we present an optimization of axial wettability gradient to maximize the heat transfer capacity of the MHP. We use an experimentally validated mathematical model and interior point method to optimize the wettability gradient. For our analysis, we consider two cases wherein (i) the mass of working fluid is constrained, (ii) mass of working fluid is a design variable. Compared to MHP with uniform high wettability and filled with a fixed mass of working fluid, optimization of the wettability gradient leads to 65% enhancement in heat transfer capacity. Similar comparisons for MHP filled with variable mass of working fluid shows more than 90% increase in the maximum heat transfer capacity due to optimization of wettability gradient.

A Review on Nanofluid Heat Pipe

2014 ◽  
Author(s):  
Maryam Shafahi ◽  
Kevin Anderson ◽  
Ali Borna ◽  
Michael Lee ◽  
Alex Kim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Working Fluid ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Medical Instruments ◽  
Thermo Physical Properties

This paper reviews the improvement in the heat pipe’s performance using nanofluid as the working fluid. The use of nanofluid enhances heat transfer in the heat pipe due to its improved thermo-physical properties, such as a higher thermal conductivity. Nanofluids proved to be the innovative approach to a variety of applications, such as electronics, medical instruments, and heat exchangers. The influence of different nanoparticles on heat pipe’s performance has been studied. Utilizing nanofluid as the working fluid leads to a significant reduction in heat pipe thermal resistance, an increase in maximum heat transfer, and an improvement of heat pipe thermal performance.

scholarly journals A heat pipe heat recovery heat exchanger for a mini-drier

2006 ◽  
Vol 17 (1) ◽  
pp. 50-57 ◽  
Author(s):  
A Meyer ◽  
R T R T Dobson
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Theoretical Model ◽  
Heat Pipe ◽  
Experimental Testing ◽  
Thermal Design ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Maximum Heat ◽  
Maximum Heat Transfer

This paper considers the thermal design and the experimental testing of a heat pipe (thermosyphon) heat exchanger for a relatively small commercially available mini-drier. The purpose of the heat exchanger is to recover heat from the moist waste air stream to preheat the fresh incoming air. The working fluid used was R134a and the correlations are given for the evaporator and condenser inside heat transfer coefficients as well as for the maximum heat transfer rate. The theoretical model and computer simulation program used for the thermal design calculations are described. The validity of the as-designed and manufactured heat exchanger coupled to the drier is experimentally verified. The theoretical model accurately predicted the thermal performance and a significant energy savings and a reasonable payback period was achieved.

scholarly journals Experimental investigations and optimization of process parameters of meshed-wick heat pipe

2020 ◽  
Vol 184 ◽  
pp. 01026 ◽  
Author(s):  
B.Ch Nookaraju ◽  
B. Hemanth Sai ◽  
K.V.N.S Himakar ◽  
N. Limba Reddy ◽  
N Sateesh
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Working Fluid ◽  
Outer Diameter ◽  
Cylindrical Shape ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Screen Mesh

Heat pipes are used to transfer heat, which are hollow cylindrical shape device filled with small amount of working fluid, which can change its phase. The rate of heat transfer in heat pipes compared to normal heat exchanging devices is more. Depending on the applications of heat transfer various heat pipes are being designed. Methanol fluid is used with 50% fill ratio. It is made of copper with outer diameter of 15.88mm and inner diameter of 14.88mm. It consists of a screen mesh made of copper powder inside it with thickness of 0.5mm. Due to heat input methanol changes its phase from liquid to vapor. The vapor loses its heat and changes its phase back to liquid in the condenser. At the condenser section the vapour gives up it heat and changes its phase from vapour to liquid. The screen mesh assists the flow of condensed working fluid through capillary action. Optimized the results by “Taguchi method” using “Minitab software”. The Thermal analysis was done with the optimum conditions, which were obtained as a result from the optimization method by Ansys Fluent software. Then finally compared the thermal parameters obtained from experiments with the Thermal analysis result. It is found the maximum heat transfer rate is optimized using meshed wick heat pipe conditions.

Maximum Heat Transfer and Operating Temperature of Oscillating Heat Pipe

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Naoko Iwata ◽  
Hiroyuki Ogawa ◽  
Yoshiro Miyazaki
Keyword(s):  
Heat Transfer ◽  
Ambient Temperature ◽  
Heat Pipe ◽  
Critical Point ◽  
Heat Input ◽  
Operating Temperature ◽  
Working Fluid ◽  
Maximum Heat ◽  
Oscillating Heat Pipe ◽  
Maximum Heat Transfer

It is reported that the operating temperature of an oscillating heat pipe (OHP) at an operating limit is not dependent on the ambient temperature but that the maximum heat transfer is dependent on this. In this study, using different ambient temperature conditions, a 15-turn OHP filled with HFC-134a as a working fluid was operated until it dries out. The maximum heat transfer was found to vary with changes in the ambient temperature, but the operating temperature at an operating limit, which depends on the filling ratio (FR) of the working fluid, was found to be constant. At the operating limit, the operating temperature decreased with an increase in the FR when the ratio was greater than 50 wt.%. Visualization experiments and calculations were used to confirm that there is an increase in the liquid volume in the OHP in accordance with an increase in the heat input and that ultimately the OHP fills with the liquid, resulting in the failure of OHP operation. In contrast, at the operating limit, when the FR was less than 50%, the operating temperature increased in line with an increase in the FR. In this case, it is assumed that the volume of liquid slugs decreases as the heat input increases, thus causing the OHP to dry out. This theory is explained using a P–V diagram of the working fluid in the OHP. The OHP thermodynamic cycle reaches a saturated liquid or vapor line before it reaches a critical point if a specified volume is shifted from the specified volume at the critical point. The optimum FR for maximum heat transfer is therefore decided by the void ratio at the critical point of the working fluid.

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