Heat Transfer Characteristics of Oscillating Heat Pipe With Ethanol as Working Fluid

2009 ◽  
Author(s):  
Haizhen Xian ◽  
Dengying Liu ◽  
Yongping Yang ◽  
Xiaoze Du
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Inclination Angle ◽  
Effective Conductivity ◽  
Heating Temperature ◽  
Operating Conditions ◽  
Working Fluid ◽  
Experimental Investigations ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

In this paper, experimental investigations on the heat transfer characteristics of OHP with ethanol as working fluid were conducted. The experimental results show that there exists a necessary temperature difference between evaporator and condenser section to keep the heat pipe working. The minimum temperature differences for the optimal operating conditions varied from 1.5 to 2.0°C. The maximum effective conductivity achieved could reach up to 111kW/m•°C. The heat pipe was obviously affected by the filling ratio in some cases but the influence law is irregular and related to inclination angles and heating temperatures. Not all OHPs operated well in the limiting case of a zero inclination angle. In most cases, the optimal value of the inclination angle went up when the heating temperature increased. An appropriate high heating temperature is helpful for the OHP to achieved excellent performances. The startup temperature varied from 40°C to 50°C without considering the horizontal heating mode.

Heat Transfer Characteristics of Oscillating Heat Pipe With Water and Ethanol as Working Fluids

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Haizhen Xian ◽  
Yongping Yang ◽  
Dengying Liu ◽  
Xiaoze Du
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Inclination Angle ◽  
Heat Transfer Performance ◽  
Filling Ratio ◽  
Working Fluid ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Oscillating Heat Pipe ◽  
Transfer Characteristics

In this paper, experiments were conducted to achieve a better understanding of the oscillating heat pipe (OHP) operating behavior with water and ethanol as working fluid. The experimental results showed that there existed a necessary temperature difference between the evaporator and the condenser section to keep the heat pipe working. The maximum effective conductivity of the water OHP reached up to 259 kW/m K, while that of the ethanol OHP is of 111 kW/m K. Not all the OHPs are operated in the horizontal operation mode. The heat transfer performance of the ethanol OHP was obviously affected by the filling ratio and the inclination angle but the influence law is irregular. The effect of the filling ratio and the inclination angle of the water OHP were smaller than that of the ethanol one. The heat transfer performance of the OHP was improved with increase of operating temperature. The startup characteristics of the OHP depended on the establishment of the integral oscillating process, which was determined by the operating factors. The startup temperature of the ethanol OHP varied from 40°C to 50°C and that of the water, OHP varied from 40°C to 60°C without considering the horizontal operating mode. The water OHP showed a better performance and more stable heat transfer characteristics than the ethanol OHP, which had no obvious advantages of the startup capability as well.

scholarly journals Heat-Transfer Characteristics of a Cryogenic Loop Heat Pipe for Space Applications

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1616
Author(s):  
Jaehwan Lee ◽  
Dongmin Kim ◽  
Jeongmin Mun ◽  
Seokho Kim
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Infrared Detectors ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Zero Gravity ◽  
Heat Transfer Characteristics ◽  
Space Applications ◽  
Transfer Characteristics ◽  
Start Up

Infrared detectors on satellites and spacecraft require cooling to increase their measurement sensitivity. To efficiently cool infrared detectors in a zero gravity environment and in limited spaces, a cryogenic loop heat pipe (CLHP) can be used to transfer heat over a certain distance by the capillary forces generated from porous wicks without a mechanical power source. The CLHP presented in this study transfers the heat load to a condenser 0.5 m away from an evaporator at temperatures below −150 °C. The CLHP with two evaporators includes a subloop for initial start-up, and uses a pressure reduction reservoir (PRR) for the supercritical start-up from room to cryogenic temperature. Nitrogen is used as the working fluid to verify the thermal behavior of the CLHP, and the heat-transfer capacity according to the nitrogen charging pressure of the PRR is investigated. To simulate a cryogenic environment, the CLHP is installed inside a space environment simulator, including a single-stage GM (Gifford McMahon) cryocooler to cool the condenser. The CLHP is horizontally installed to simulate zero gravity. The heat-transfer characteristics are experimentally evaluated through the loop circulation of the CLHP.

Experimental Investigation on the Heat Transfer Characteristics of Nanofluids in Self-Exciting Mode Oscillating-Flow Heat Pipe

2011 ◽  
Vol 396-398 ◽  
pp. 250-254 ◽  
Author(s):  
Fu Min Shang ◽  
Jian Hong Liu ◽  
Deng Ying Liu
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Working Fluid ◽  
Oscillating Flow ◽  
Filling Rate ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow Heat

The objective of this article is to provide the heat transfer characteristics of Cu-H2O nanofluids in self-exciting mode oscillating-flow heat pipe under different laser heating input, and to compare with the heat transfer characteristics of the same heat pipe with distilled water as working fluids. In this paper, the peculiarity of heat transfer rate of the SEMOS heat pipe with Cu-H2O fluid has been experimentally confirmed by changing the proportion of working fluid and Cu nanoscale particles in the heat pipe. As the results, it has been confirmed that the parameter of filling rate of working fluid determine the heat transfer rate of SEMOS heat pipe, although under certain condition heat transfer performance could be improved because of the addition of nanofluids.

Effect of Wick Characteristics on the Thermal Performance of the Miniature Loop Heat Pipe

2009 ◽  
Vol 131 (8) ◽  
Author(s):  
Randeep Singh ◽  
Aliakbar Akbarzadeh ◽  
Masataka Mochizuki
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Working Fluid ◽  
Vapor Flow ◽  
Loop Heat Pipe ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Two phase heat transfer devices based on the miniature version of loop heat pipe (LHP) can provide very promising cooling solutions for the compact electronic devices due to their high heat flux management capability and long distance heat transfer with minimal temperature losses. This paper discusses the effect of the wick properties on the heat transfer characteristics of the miniature LHP. The miniature model of the LHP with disk-shaped evaporator, 10 mm thick and 30 mm disk diameter, was designed using copper containment vessel and water as the working fluid, which is the most acceptable combination in electronic cooling applications. In the investigation, wick structures with different physical properties including thermal conductivity, pore radius, porosity, and permeability and with different structural topology including monoporous or biporous evaporating face were used. It was experimentally observed that copper wicks are able to provide superior thermal performance than nickel wicks, particularly for low to moderate heat loads due to their low heat conducting resistance. With monoporous copper wick, maximum evaporator heat transfer coefficient (hev) of 26,270 W/m2 K and evaporator thermal resistance (Rev) of 0.06–0.10°C/W were achieved. For monoporous nickel wick, the corresponding values were 20,700 W/m2 K for hev and 0.08–0.21°C/W for Rev. Capillary structure with smaller pore size, high porosity, and high permeability showed better heat transfer characteristics due to sufficient capillary pumping capability, low heat leaks from evaporator to compensation chamber and larger surface area to volume ratio for heat exchange. In addition to this, biporous copper wick structure showed much higher heat transfer coefficient of 83,787 W/m2 K than monoporous copper wick due to improved evaporative heat transfer at wick wall interface and separated liquid and vapor flow pores. The present work was able to classify the importance of the wick properties in the improvement of the thermal characteristics for miniature loop heat pipes.

Effect of Tube Bending on Heat Transfer Characteristics of Miniature Heat Pipe with Sintered Porous Media

2011 ◽  
Vol 312-315 ◽  
pp. 1015-1020 ◽  
Author(s):  
P. Sakulchangsatjatai ◽  
N. Thuchayapong ◽  
P. Terdtoon ◽  
N. Sangsirakoup
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Heat Pipe ◽  
Working Fluid ◽  
Tube Bending ◽  
Heat Transfer Characteristics ◽  
Small Space ◽  
Condenser Section ◽  
Transfer Characteristics ◽  
Evaporator Section

Miniature heat pipe is a compact heat transfer device with very high heat transfer capability. The miniature heat pipes have been widely accepted for thermal management in laptop computer. Generating heat from chip-set is rapidly transferred to a heat sink via the miniature heat pipe which occupies small space, resulting in smaller and more attractive size of the laptop. Heat pipe bending is unavoidable in such small space. However, tube bending decreases thermal performance of heat pipe and it stops working in some cases. In this study, a computer program to simulate heat transfer characteristics of a bending water-copper-sintered-wick heat pipe has been established. Domains of heat pipe consist of three parts; vapor of working fluid in vapor core which transfer heat and mass from evaporator section to condenser section, liquid of working fluid in wick which transfer heat and mass from condenser section to evaporator section in porous media by capillary force, and container wall. In simulation, fluid flow and heat transfer were assumed to be steady, laminar and incompressible. The porous media is saturated with liquid and working fluid is assumed to be Newtonian fluid. The governing equations, i.e. continuity, Navier-Stokes, and energy equations, and boundary conditions were solved by using the Finite Element Method (FEM). Several bending angles (0 and 90; angle measured from straight pipe) with 6 mm outer diameter and 200 mm length were simulated and tested. It was found that the predicted and experimental thermal resistances of heat pipe, when bending angle increases from 0 to 90, increased from 0.47°C/W to 0.65°C/W and 0.67°C/W to 0.88°C/W respectively, due to rising of the vapor pressure drop in vapor channel. The simulation results are in agreement with experimental data with 26-29% error.

Experiment Investigation on Heat Transfer Characteristics of a Novel Gravity-Assisted Heat Pipe Heat Exchanger

2011 ◽  
Vol 236-238 ◽  
pp. 689-693
Author(s):  
Xiao Lin Cao ◽  
Shuang Jun Cao ◽  
Xiao Jun Zhu ◽  
Wei Zeng ◽  
Fang Fang Wang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Inclination Angle ◽  
Filling Ratio ◽  
Heat Transfer Characteristics ◽  
Air Velocity ◽  
Condenser Section ◽  
Transfer Resistance ◽  
Transfer Characteristics ◽  
Minimum Heat

A novel gravity-assisted heat pipe with fins was developed. The influences of filling ratio, inclination angle and air velocity at condenser section on the heat transfer characteristics were investigated experimentally. The results show that heat power has an important effect on heat transfer characteristics while inclination angle has little effect on that. The minimum heat transfer resistance is got at the filling ratio equaling about 20%. The heat transfer thermal resistance decreases gradually as the air velocity at condenser section increases.

An Experimental Study of Heat Transfer Characteristics in Miniature Loop Heat Pipes With Rectangular Shaped Evaporator

2011 ◽  
Author(s):  
Z. R. Lin ◽  
Z. Y. Lee ◽  
L. W. Zhang ◽  
S. F. Wang ◽  
A. A. Merrikh ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heat Sink ◽  
Thermal Design ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Heat Transport Capability

Loop heat pipe (LHP) is a highly efficient cooling device. It has gained great attention in the electronics cooling industry due to its superior heat transport capability — that is, its ability to carry heat over long distances. For this article, a miniature flat loop heat pipe (MFLHP) with rectangular-shaped evaporator was developed. The LHP’s evaporator was combined with the compensation chamber. MFLHPs with different diameters and lengths for the connecting pipeline were selected for a series of experimental studies on their heat transfer characteristics. In these experiments, pure water was used as the working fluid. The studies showed that the heat transport capability of a MFLHP with 4 mm diameter was better than that a MFLHP with 3 mm diameter. At a low thermal resistance of 0.04°C /W (at 200W), an optimal length for the connecting pipeline for a particular MFLHP with 4 mm diameter was identified. Finally, a heat sink attached to a MFLHP was developed for cooling a graphics processing unit (GPU), the thermal design power (TDP) of which was 200 W. The results showed the GPU heat sink with MFLHP had good performance and satisfied GPU cooling requirements. Compared to the conventional heat pipe solutions, only one MFLHP was able to cope with high power dissipation, offering the potential to make a lighter heat sink.

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