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.

scholarly journals Experiment Study on Improved Closed Loop Pulsating Heat Pipe with Silver/Water Nanofluid

2013 ◽  
Vol 732-733 ◽  
pp. 462-466
Author(s):  
Wei Xiu Shi ◽  
Wei Yi Li ◽  
Li Sheng Pan
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Closed Loop ◽  
Filling Ratio ◽  
Pulsating Heat Pipe ◽  
Start Up ◽  
High Heating ◽  
Operation Stability ◽  
Heat Transfer Limit

Start up and heat transfer performances of improved closed loop pulsating heat pipe (ICLPHP) charged with water and silver/water nanofluid, respectively, were investigated experimentally with angles of 90° and 60°. Both the average evaporator wall temperature and the overall thermal resistance of the ICLPHP with different working fluids and at the volume filling ratio of 35% were tested and compared. Experimental results showed that nanofluid caused different thermal performances of ICLPHP. Within the experiment range, silver/water nanofluid can improve operation stability and heat transfer limit and reduce starting power compared with water. With high heating power, thermal resistance of nanofluid was lower than that of water. With inclination of 60°, ICLPHP with nanofluid operated better and reduced sensitivity of inclination.

scholarly journals Analysis on start up and heat transfer performance of mercury heat pipe under alternating heating power

2021 ◽  
Vol 248 ◽  
pp. 01004
Author(s):  
Chongju Hu ◽  
Xiuxiang Zhang ◽  
Hongyan Wang ◽  
Bo Wu ◽  
Pinghua Zhang
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Start Up ◽  
Steady State Temperature ◽  
Temperature Heat ◽  
Fluctuation Amplitude

Heat pipe may be affected by the high temperature heat source during operation, resulting in unsteady oscillation heating. In this paper, the influence of alternating power and period on the start-up and heat transfer performance of mercury heat pipe is studied by using the method of equivalent thermal resistance of heat pipe. The results are as follows:1) The start-up time of alternating power heating and steady-state power heating is basically equal; 2) For the alternating power heating, the steady-state temperature of heat pipe changes periodically, increasing the alternating period or the amplitude of alternating power will lead to the increase of the fluctuation amplitude of heat pipe temperature, and the influence of alternating period is greater than that of changing the amplitude of alternating power. 3) Under the condition of alternating power heating, the steady-state thermal resistance of heat pipe changes periodically. The fluctuation amplitude of steady-state thermal resistance of heat pipe increases with the increase of alternating period and alternating power amplitude, and the influence of alternating power amplitude is greater than that of alternating period.

scholarly journals Analysis on heat transfer and start-up performance of mercury heat pipe

2021 ◽  
Vol 245 ◽  
pp. 03012
Author(s):  
Xiuxiang Zhang ◽  
Kang He ◽  
Quan Yang ◽  
Chengcai Xi
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Saturated Vapor ◽  
Heating Power ◽  
Good Thermal Stability ◽  
Start Up ◽  
Steady State Heat ◽  
Steady State Heat Transfer ◽  
Transient Thermal

Mercury heat pipe has the advantages of good thermal stability and low saturated vapor pressure, which is the best choice for the transition from water heat pipe to liquid metal heat pipe. The effects of heating power and heat pipe structure on start-up time and steady-state heat transfer performance of mercury heat pipe were studied by using transient thermal network model. The results showed that: 1) Increasing the length of condenser is beneficial to reducing the start-up time and thermal resistance; 2) Increasing the heating power or wall thickness will reduce the thermal resistance, but increase the start-up time, and increasing the porosity of wick is just the opposite; 3) Increasing the thickness of wick can increase both the start-up time and the thermal resistance.

Experimental Investigation of Heat Transfer Enhancement of the Heat Pipe Using CuO-Water Nanofluid

2010 ◽  
Vol 160-162 ◽  
pp. 507-512 ◽  
Author(s):  
Dong Dong Li ◽  
Wei Lin Zhao ◽  
Zong Ming Liu ◽  
Bao Jie Zhu
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Mass Concentration ◽  
Heat Transfer Performance ◽  
Input Power ◽  
Distilled Water ◽  
Transfer Performance ◽  
Start Up

This paper presents an experimental investigation of the heat transfer characteristics of the heat pipe with CuO-water nanofluid. For this purpose, CuO nanoparticles of 30 nm size were dispersed in distilled water to form stable suspension containing 0.1% ~ 2.0% mass concentrations of nanoparticles, and then the heat pipe was produced after CuO-water nanofluid was added in it as the working fluid. Experimental results show that the use of CuO-water nanofluid hold a lower start-up temperature and shorter start-up time for the evaporation section of the heat pipe compared to distilled water. Their heat transfer performance of the evaporation section and condenser section has been improved than that of distilled water. The heat transfer coefficient of nanofluid is higher than that of the base liquid and found to increase by 29.4% and 125.0% for the mass concentration of 0.5% compared with the heat pipe using distilled water while the input power ranging from 15W to 45W. By examining the thermal resistance, it was found that the thermal resistance has been significantly decreased compared with the heat pipe with distilled water. The thermal resistance of heat pipe using CuO-water nanofluid at a mass concentration of 0.5% is 0.36K/W when the input power is 45W, while the thermal resistance of heat pipe using distilled water is 0.80K/W. Further analysis indicates that the heat pipe using CuO-water nanofluid at 1.0% mass concentrations has the best heat transfer performance.

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 Comprehensive Performance of Sintering Biporous Wicks Prepared by Salt Dissolution and Cold Pressing Process

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Chunsheng Guo ◽  
Cheng Jiang ◽  
Jun Ma ◽  
Yingwen Cao ◽  
Yong Zou ◽  
...  
Keyword(s):  
Resistance Testing ◽  
Pressing Pressure ◽  
Long Distance ◽  
Capillary Suction ◽  
Cold Pressing ◽  
Testing Platform ◽  
Loop Heat Pipes ◽  
Porous Wick ◽  
Salt Dissolution ◽  
Total Suction

Abstract Porous wicks are a key component of loop heat pipes (LHPs). In order to enhance the antigravity and long-distance operation ability of the LHP, a porous wick is required to have the characteristics of high permeability and high capillary suction capability. In this paper, biporous wicks were prepared by salt dissolution pore-forming technology, and a gas resistance testing platform and a capillary suction testing platform were setup to test the samples. The current research studies the effects of different pore-forming agent mass ratios (10%, 30%, and 40%) and different cold pressing pressures (30 kN, 40 kN, 50 kN, and 60 kN) on the porosity, permeability, and the suction speed. The study finds that the porosity, permeability, and the total suction mass of the porous wicks all increase when the NaCl mass increases; the increase of the suction speed is proportional to the increase of the porosity and the permeability, and hence, proportional to the increase of NaCl mass. The total suction mass and suction speed is inversely proportional to cold pressing pressure.

Study on Relationship between Partial Load and Rib Effect Coefficient of Refrigeration Heat Exchanger Used in Air Conditioning

2011 ◽  
Vol 121-126 ◽  
pp. 2922-2930
Author(s):  
Hou Hua Wang ◽  
Hou Shuai Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Resistance ◽  
Resistance Ratio ◽  
Transfer Model ◽  
Variable Load ◽  
Value Analysis ◽  
Partial Load ◽  
Load Rate ◽  
The Relationship

The relationship between thermal resistance ratio ζ(the ratio of thermal resistance between two sides of the tube wall) and load rate, according to heat transfer theory, is derived from simplifying the heat transfer model of heat exchanger. Considering the different running time of heat exchanger under variable load, the operation heat is proposed. Then the range of thermal resistance ratio for evaporator and condenser is determined and the law of thermal resistance is validated by analyzing the example. As a result, the relationship between rib effect coefficient and the thermal resistance ratio is established. Furthermore, value analysis of rib effect coefficient is analyzed. Results of this study show that the heat transfer performance of evaporator and condenser maximizes when ζ=1 at the partial load rate of (0.25, 0.50). Meanwhile, rib effect coefficient on the water side is less than that of the refrigerant side for evaporator and condenser.

Heat Transfer with Propane Evaporation from a Porous Wick of Heat Pipe

2001 ◽  
Vol 4 (2) ◽  
pp. 10 ◽  
Author(s):  
Leonid L. Vasiliev, Jr. ◽  
Alexander S. Zhuravlyov ◽  
Mikhail N. Novikov ◽  
L. L. Vasiliev, Jr
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Porous Wick

scholarly journals Correlation between the Porosity and Permeability of a Polymer Filter Fabricated via CO2-Assisted Polymer Compression

Membranes ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 391 ◽  
Author(s):  
Takafumi Aizawa ◽  
Yoshito Wakui
Keyword(s):  
Pore Size ◽  
Gas Permeability ◽  
Physical Property ◽  
Polymer Fibers ◽  
Darcy Law ◽  
Compression Method ◽  
Porosity Reduction ◽  
Sintered Porous Material ◽  
Porosity And Permeability ◽  
Size Data

A porous filter was fabricated by plasticizing polymer fibers with CO2, followed by pressing and adhering; then, its gas permeability, a basic physical property of filters, was measured using N2. The as-obtained filter was well compressed and expected to approximate a sintered porous material. Therefore, the fabricated filter was analyzed by applying the Darcy law, and the correlation between its gas permeability and porosity was clarified. The gas permeability decreased owing to both pore size and porosity reduction upon increasing the degree of compression, which is a feature of the CO2-assisted polymer compression method. In particular, without any contradiction of pore size data previously reported, the gas permeability was clearly determined by the filter porosity and pore size. This study can serve as a guide for designing filters via CO2-assisted polymer compression.

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