scholarly journals Experimental Study of a Loop Heat Pipe with Direct Pouring Porous Wick for Cooling Electronics

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1332
Author(s):  
Bing Cai ◽  
Weizhong Deng ◽  
Tong Wu ◽  
Tingting Wang ◽  
Zhengyuan Ma ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Heat Load ◽  
Load Test ◽  
Vapor Flow ◽  
Loop Heat Pipes ◽  
Load Matching ◽  
Porous Wick ◽  
Start Up ◽  
Compensation Chamber ◽  
And Performance

A pouring silicate wick was manufactured to explore the influence of process and physical properties on the production and performance of loop heat pipes (LHP). This paper theoretically analyzed the advantages of pouring porous wick and introduced the technology of pouring silicate directly on evaporator. Based on this, the heat transfer performance of copper-methanol LHP system with pouring porous wick was tested under different positions. The results showed that with the input of multiple heat sources, the LHP could start up and maintain a stable temperature from 40 W to 160 W. When the vapor grooves were located above the compensation chamber, it was difficult to start up positively. By adding gravity assistance, the system could obtain more stable liquid supply and vapor flow, so as to realize start up. In the variable heat load test, the LHP showed good adaptability to the change of heat load. The thermal resistance of the system decreased with the increase of heat load. The thermal resistance of the evaporator almost unchanged and was always lower than 0.05 °C/W, which indicated that the pouring porous wick in the evaporator had good heat load matching.

Experimental Study On Preparation and Heat Transfer of Nickel-Based Ammonia LHP

2021 ◽  
Author(s):  
Wenjing Ning ◽  
Jun Ma ◽  
Cheng Jiang ◽  
Yingwen Cao ◽  
Chunsheng Guo ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Pore Size ◽  
Thermal Load ◽  
Physical Property ◽  
Variable Load ◽  
Pressing Pressure ◽  
Cold Pressing ◽  
Porous Wick ◽  
Start Up

Abstract The loop heat pipe (LHP) is a passive heat sink used in aerospace and electronic devices. As the core component of the LHP, the physical property parameters of porous wick directly affect the overall performance of the LHP. In this paper, the performance of the porous wick is improved by adjusting the pore size, thereby improving the performance of the LHP. The nickel-based double-pore porous wicks are prepared by T225 nickel powder and NaCl particles, and the pore size of the porous wicks can be changed by different cold pressing pressures (30KN, 40KN, 50KN, 60KN). The effects of different cold pressing pressures on the porosity, permeability, and other physical property parameters are studied when the ratio of pore former is 20wt%. In the end, we select the cold pressing pressure of 30KN to prepare the porous wick of the LHP. Then the effects of constant load and variable load of the heat transfer performance under different placement angles are studied. The results show that the heat load range is 10W-100W, the minimum evaporator thermal resistance is 0.424K/W, and the minimum LHP thermal resistance is 0.598K/W. When ß=0°, there is a "backflow" phenomenon at the initial stage of low thermal load. With the increase of thermal load, the "backflow" duration decreases until it disappears, and the start-up time becomes shorter. The thermal resistances of the evaporator and LHP decrease and then increase. When ß= -90°, the LHP appears "reverse start-up" phenomenon.

Investigation of Heat Transfer in Evaporator of Microchannel Loop Heat Pipe

2013 ◽  
Vol 135 (10) ◽  
Author(s):  
Alexander A. Yakomaskin ◽  
Valery N. Afanasiev ◽  
Nikolay N. Zubkov ◽  
Dmitry N. Morskoy
Keyword(s):  
Heat Transfer ◽  
Electronics Cooling ◽  
Open Loop ◽  
Main Element ◽  
Working Fluid ◽  
Vapor Flow ◽  
Loop Heat Pipes ◽  
Evaporation And Condensation ◽  
Flow Geometry ◽  
Compensation Chamber

Loop heat pipes (LHP) are heat transfer devices which use evaporation and condensation of working fluid to transfer heat and use capillary forces to provide fluid circulation in a closed loop. One of the main applications of LHP is cooling of electronic components. Further development of this field is associated with miniaturization. Thus, there are strict limits imposed upon size of elements of heat transfer devices in electronics cooling. One of such elements is an evaporator of the LHP, its main element. This paper deals with the LHP evaporator and is aimed at showing dependence of wick conductivity, thickness, and vapor flow geometry on overall heat transfer performance. An open loop experimental setup was created. Experiments were carried out with various configurations. The evaporator consisted of a microchannel (MC) plate, with groove widths of 100 and 300 μm, wick (metal and nonmetal porous materials were used) and a compensation chamber (CC). Heat load varied from 20 to 140 W in steps of 20 W. The area of the heater was equal to 19 × 19 mm2. The working fluid is de-ionized water. Experimental results include data on temperature distribution across the wick's height, temperature of microchannel's surface, and temperature of water in the compensation chamber. The results reveal a potential for performing optimization of the zone of evaporation in order to produce thinner LHP evaporators.

scholarly journals Recent Advances in Loop Heat Pipes with Flat Evaporator

Entropy ◽  
2021 ◽  
Vol 23 (11) ◽  
pp. 1374
Author(s):  
Pawel Szymanski
Keyword(s):  
Reverse Flow ◽  
Construction Materials ◽  
Poor Performance ◽  
Heat Pipes ◽  
Manufacturing Cost ◽  
Heating Zone ◽  
Loop Heat Pipes ◽  
Start Up ◽  
Flat Evaporator ◽  
Compensation Chamber

The focus of this review is to present the current advances in Loop Heat Pipes (LHP) with flat evaporators, which address the current challenges to the wide implementation of the technology. A recent advance in LHP is the design of flat-shaped evaporators, which is better suited to the geometry of discretely mounted electronics components (microprocessors) and therefore negate the need for an additional transfer surface (saddle) between component and evaporator. However, various challenges exist in the implementation of flat-evaporator, including (1) deformation of the evaporator due to high internal pressure and uneven stress distribution in the non-circular casing; (2) heat leak from evaporator heating zone and sidewall into the compensation chamber; (3) poor performance at start-up; (4) reverse flow through the wick; or (5) difficulties in sealing, and hence frequent leakage. This paper presents and reviews state-of-the-art LHP technologies; this includes an (a) review of novel manufacturing methods; (b) LHP evaporator designs; (c) working fluids; and (d) construction materials. The work presents solutions that are used to develop or improve the LHP construction, overall thermal performance, heat transfer distance, start-up time (especially at low heat loads), manufacturing cost, weight, possibilities of miniaturization and how they affect the solution on the above-presented problems and challenges in flat shape LHP development to take advantage in the passive cooling systems for electronic devices in multiple applications.

scholarly journals Experimental analysis of a Vapour-Liquid Separated Flat Loop Heat Pipe Evaporator System

2020 ◽  
Vol 307 ◽  
pp. 01055
Author(s):  
Yang Yang ◽  
Zhu Kai ◽  
Wang Yabo ◽  
Wei Jie ◽  
Sarula Chen
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Load ◽  
Experimental System ◽  
Base Plate ◽  
Loop Heat Pipe ◽  
Operation Performance ◽  
Total Thermal Resistance ◽  
Variable Heat ◽  
Start Up

In this paper, a unique operation mechanism of loop heat pipe (LHP) was proposed. To test the performance of LHP under this new mechanism, a visual flat LHP evaporator prototype and an open experimental system were designed and assembled, and start-up experiment and variable heat load experiment were done respectively to obtain the actual operation characteristics, such as the evaporator thermal resistance (Re), total thermal resistance (Rt), start-up time and temperature of base plate. The proposed LHP had better overall performance during the start-up tests when He value of EC was set to 0.5mm, and its corresponding Re and Rt value were 0.035 K/W and 0.451 K/W when the heating power was 208w. Meanwhile, as per the heat load applied to the base plate, the whole variable heat load experiment could be divided into three distinct stages: low heat load stage, efficiency operation stage and dry-out stage. Moreover, the results also showed that the circulation driven head formed inside of the EC played an important role in promoting the operation performance, especially when the wick, the vapour-liquid interface and the bottom of the evaporator arrived at a reasonable situation.

Qassim Central Power Plant Inlet Air Cooling System

2001 ◽  
Author(s):  
A. Al Bassam ◽  
Y. M. Al Said
Keyword(s):  
Saudi Arabia ◽  
Power Plant ◽  
Cooling System ◽  
Flow Diagram ◽  
Air Cooling ◽  
Process Flow Diagram ◽  
Electric Company ◽  
Start Up ◽  
Air Cooling System ◽  
And Performance

This paper summarizes the experiences with the first gas turbine inlet air cooling project in Saudi Arabia. It will cover the feasibility study, cooling system options, overview, system equipment description, process flow diagram, construction, commissioning, start-up and performance of the project which is currently under commissioning and initial start up at Qassim Central Power Plant (QCPP) owned by Saudi Electric Company (S.E.C.) Central Region Branch.

The Role of Spiritual Capital in Innovation and Performance: Evidence from Developing Economies

2017 ◽  
Vol 41 (4) ◽  
pp. 621-640 ◽  
Author(s):  
Mitchell J. Neubert ◽  
Steven W. Bradley ◽  
Retno Ardianti ◽  
Edward M. Simiyu
Keyword(s):  
Developing Economies ◽  
Large Body ◽  
Institutional Voids ◽  
Spiritual Capital ◽  
Social Forms ◽  
Significant Relationships ◽  
Start Up ◽  
Additional Influence ◽  
And Performance

Forms of capital play a significant role in the innovation and performance of start–up firms. Current entrepreneurial research has focused on the role of financial, human, and social forms of capital. We build on a large body of theory and research in sociology and economics, proposing spiritual capital as an additional influence where institutional voids are greater in the development contexts studied. Results from microcredit entrepreneurs in Kenya and Indonesia indicate significant relationships between entrepreneurs’ spiritual capital and business innovation and performance, even after accounting for other forms of capital.

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