Maximum heat-transfer capacity of a vertical two-phase thermal siphon

1978 ◽  
Vol 35 (3) ◽  
pp. 1017-1021
Author(s):  
M. G. Semena
Keyword(s):  
Heat Transfer ◽  
Two Phase ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Heat Transfer Capacity

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.

scholarly journals Влияние наножидкостей на теплопередающую способность миниатюрных термосифонов для охлаждения электроники

2019 ◽  
Vol 45 (6) ◽  
pp. 54
Author(s):  
Б.И. Бондаренко ◽  
В.Н. Морару ◽  
В.Ю. Кравец ◽  
Г. Бехмард
Keyword(s):  
Thermal Resistance ◽  
Closed Loop ◽  
Electronics Cooling ◽  
Sharp Decrease ◽  
Vapor Film ◽  
Two Phase ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Boiling Process ◽  
Heat Transfer Capacity

AbstractStable nanofluids based on DG-100 grade carbon black and carbon nanotubes have been prepared, and their influence on the maximum heat-transfer capacity and thermal resistance of closed-loop two-phase thermosyphons (TPTs) intended for electronics cooling have been studied. A more than twofold increase in the critical heat flux of these TPTs as compared to those filled with water has been obtained along with a sharp decrease in their thermal resistance. It is suggested that this effect is not only due to the high thermal conductivity of the proposed nanofluids, but is also related to the formation of a specific porous structure hindering the appearance of a vapor film and enhancing the boiling process.

Numerical Investigation on Pool Boiling Over a Vertical Tube Coupled With In-Tube Condensation

2019 ◽  
Author(s):  
Shuai Ren ◽  
Wenzhong Zhou
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Boiling Heat Transfer ◽  
Power Plants ◽  
Pool Boiling ◽  
Heat Removal ◽  
Vertical Tube ◽  
Two Phase ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Abstract Pool boiling and in-tube condensation phenomena have been investigated intensively during the past decades, due to the superior heat transfer capacity of the phase change process. In passive heat removal heat exchangers of nuclear power plants, the two phase-change phenomena usually occur simultaneously on both sides of the tube wall to achieve the maximum heat transfer efficiency. However, the studies on the effects of in-tube condensation on external pool boiling heat transfer are very limited, especially in numerical computation aspect. In the present study, the saturated pooling boiling over a vertical tube under the influences of in-tube steam condensation is investigated numerically. The Volume of Fluid (VOF) interface tracking method is employed based on the 2D axisymmetric Euler-Euler multiphase frame. The phase change model combining with a mathematical smoothing algorithm and a temporal relaxation procedure has been implemented into CFD platform by user defined functions (UDFs). The two-phase flow pattern and bubble behavior have been analyzed. The effects of inlet steam mass flow rate on boiling heat transfer are discussed.

Guidelines for Designing Micropillar Structures for Enhanced Evaporative Heat Transfer

2021 ◽  
Author(s):  
Kidus Guye ◽  
De Dong ◽  
Yunseo Kim ◽  
Hyoungsoon Lee ◽  
Baris Dogruoz ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Interfacial Area ◽  
High Heat ◽  
Heat Fluxes ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Evaporation Heat

Abstract Over the last several decades, cooling technologies have been developed to address the growing thermal challenges associated with high-powered electronics. However, within the next several years, the heat generated by these devices is predicted to exceed 1 kW/cm2, and traditional methods, such as air cooling, are limited in their capacities to dissipate such high heat fluxes. In contrast, two-phase cooling methods, such as microdroplet evaporation, are very promising due to the large latent heat of vaporization associated with the phase change process. Previous studies have shown non-axisymmetric droplets exhibit different evaporation characteristics than spherical droplets. For a droplet pinned atop a micropillar, the solid-liquid and liquid-vapor interfacial area, the volume, and thickness of the droplet are the major factors that govern the evaporation heat transport process. In this work, we develop a shape optimization tool using the particle swarm optimization algorithm to maximize evaporation from a droplet confined atop a micropillar. The tool is used to optimize the shape of a nonaxisymmetric droplet. Compared to droplets atop circular and regular equilateral triangular micropillar structures, we find that droplets confined on pseudo-triangular micropillar structures have 23.7% and 5.7% higher heat transfer coefficients, respectively. The results of this work will advance the design of microstructures that support droplets with maximum heat transfer performance.

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.

Experimental Investigation of an Evaporator Enhanced With a Micro-Porous Structure in a Two-Phase Thermosyphon Loop

2008 ◽  
Author(s):  
Richard Furberg ◽  
Rahmatollah Khodabandeh ◽  
Bjo¨rn Palm ◽  
Shanghua Li ◽  
Muhammet Toprak ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Rectangular Channel ◽  
Large Diameter ◽  
Nucleate Boiling ◽  
Nano Particles ◽  
Working Fluid ◽  
Two Phase ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Following is an experimental study of six different evaporators in a closed two-phase thermosyphon loop system, where the influence of various evaporator dimensions and surfaces was investigated. The evaporators featured a 30 mm long rectangular channel with hydraulic diameters ranging from 1.2–2.7 mm. The heat transfer surface of one of the tested evaporators was enhanced with copper nano-particles, dendritically connected into an ordered micro-porous three dimensional network structure. To facilitate high speed video visualization of the two-phase flow in the evaporator channel, a transparent polycarbonate window was attached to the front of the evaporators. Refrigerant 134A was used as a working fluid and the tests were conducted at 6.5 bar. The tests showed that increasing channel diameters generally performed better. The three largest evaporator channels exhibited comparable performance, with a maximum heat transfer coefficient of about 2.2 W/(cm2K) at a heat flux of 30–35 W/cm2 and a critical heat flux of around 50 W/cm2. Isolated bubbles characterized the flow regime at peak performance for the large diameter channels, while confined bubbles and chaotic churn flow typified the evaporators with small diameters. In line with previous pool boiling experiments, the nucleate boiling mechanism was significantly enhanced, up to 4 times, by the nano- and micro-porous enhancement structure.

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