scholarly journals Experimental Study on Thermal Performance of a Loop Heat Pipe with Different Working Wick Materials

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2453
Author(s):  
Kyaw Zin Htoo ◽  
Phuoc Hien Huynh ◽  
Keishi Kariya ◽  
Akio Miyara
Keyword(s):  
Stainless Steel ◽  
Heat Pipes ◽  
Working Fluid ◽  
Stable Operation ◽  
Loop Heat Pipe ◽  
Heater Surface ◽  
Loop Heat Pipes ◽  
Limited Temperature ◽  
Sintered Stainless Steel ◽  
Continuous Heat

In loop heat pipes (LHPs), wick materials and their structures are important in achieving continuous heat transfer with a favorable distribution of the working fluid. This article introduces the characteristics of loop heat pipes with different wicks: (i) sintered stainless steel and (ii) ceramic. The evaporator has a flat-rectangular assembly under gravity-assisted conditions. Water was used as a working fluid, and the performance of the LHP was analyzed in terms of temperatures at different locations of the LHP and thermal resistance. As to the results, a stable operation can be maintained in the range of 50 to 520 W for the LHP with the stainless-steel wick, matching the desired limited temperature for electronics of 85 °C at the heater surface at 350 W (129.6 kW·m−2). Results using the ceramic wick showed that a heater surface temperature of below 85 °C could be obtained when operating at 54 W (20 kW·m−2).

Minimizing the Wick Thickness in a Planar Microscale Loop Heat Pipe Using Efficient Thermodynamic Design

2011 ◽  
Author(s):  
Navdeep S. Dhillon ◽  
Jim C. Cheng ◽  
Albert P. Pisano
Keyword(s):  
Heat Flow ◽  
Heat Pipe ◽  
Thermal Characteristics ◽  
Heat Pipes ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Two Phase ◽  
Loop Heat Pipes ◽  
Evaporator Section ◽  
Compensation Chamber

Theoretical and numerical thermodynamic analysis of the evaporator section of a planar microscale loop heat pipe is presented, to minimize the permissible wick thickness in such a device. In conventional cylindrical loop heat pipes, a minimum wick thickness is required in order to reduce parasitic heat flow, and prevent vapor leakage, into the compensation chamber. By taking advantage of the possibilities allowed by microfabrication techniques, a planar evaporator/compensation chamber design topology is proposed to overcome this limitation, which will enable wafer-based loop heat pipes with device thicknesses on the order of a millimeter or less. Thermodynamic principles governing two-phase flow of the working fluid in a loop heat pipe are analyzed to elucidate the fundamental requirements that would characterize the startup and steady state operation of a planar phase-change device. A three dimensional finite element thermal-fluid solver is implemented to study the thermal characteristics of the evaporator section and compensation chamber regions of a planar vertically wicking micro-columnated loop heat pipe. The use of in-plane thermal conduction barriers to reduce parasitic heat flow into the compensation chamber is demonstrated.

The Effect of CuO-Water Nanofluid and Biomaterial Wick on Loop Heat Pipe Performance

2014 ◽  
Vol 875-877 ◽  
pp. 356-361 ◽  
Author(s):  
Nandy Putra ◽  
Wayan Nata Septiadi ◽  
Rosari Saleh ◽  
Rardi Artono Koestoer ◽  
Suhendro Purbo Prakoso
Keyword(s):  
Heat Pipe ◽  
Pure Water ◽  
Sol Gel ◽  
Heat Pipes ◽  
Cuo Nanoparticles ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Gel Method ◽  
Loop Heat Pipes ◽  
Copper Pipe

The determinants of heat pipe performances are its wick and working fluid, instead of controlled by the material, dimension, and the shape of heat pipe. This study aimed to determine the effect of using nanofluid on the performance of Loop heat pipes (LHP) with CuO-water nanofluid that using biomaterials wick. LHP was made of 8 mm diameter copper pipe, with the diameter of evaporator and the condenser was 20 mm respectively and the length of the heat pipe was 100 mm. The wick was made of biomaterials Collaria Tabulate and the working fluid was CuO-water nanofluids where the CuO nanoparticles were synthesized by sol-gel method. The characteristic of the Tabulate Collaria biomaterial as a wick in LHP was also investigated in this experiment. The results of the experiments showed that the temperature differences between the evaporator and condenser sections with the biomaterial wick and CuO-water nanofluid were less than those using pure water. These results make the biomaterial (Collar) and nanofluids are attractive both as wick and working fluid in LHP technology. Keywords: loop heat pipe, wick, biomaterial, nanofluid.

Modeling and Analysis of Supercritical Startup of a Cryogenic Loop Heat Pipe

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Lizhan Bai ◽  
Guiping Lin ◽  
G. P. Peterson ◽  
Dongsheng Wen
Keyword(s):  
Mathematical Model ◽  
Parametric Study ◽  
Heat Load ◽  
Heat Pipes ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Modeling And Analysis ◽  
Loop Heat Pipes ◽  
Network Method ◽  
Startup Performance

Supercritical startup of cryogenic loop heat pipes (CLHPs) has been investigated both analytically and experimentally. Mathematical model of the supercritical startup has been established using the nodal network method, and parametric study is conducted where the effects of working fluid charged pressure, parasitic heat load from the ambient, etc., on the supercritical startup characteristics are incorporated and evaluated. The result improves understanding of the effects of these parameters on supercritical startup and identification of those conditions under which supercritical startup can and will occur. In addition, the modeling effort has led to an enhanced understanding of supercritical startup performance.

scholarly journals The Influence of Loop Heat Pipe Evaporator Porous Structure Parameters and Charge on Its Effectiveness for Ethanol and Water as Working Fluids

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7029
Author(s):  
Krzysztof Blauciak ◽  
Pawel Szymanski ◽  
Dariusz Mikielewicz
Keyword(s):  
Porous Structure ◽  
Pore Size ◽  
Heat Pipe ◽  
Capillary Pressure ◽  
Pressure Difference ◽  
Working Fluid ◽  
Loop Heat Pipe ◽  
Working Fluids ◽  
Integral Characteristics ◽  
Sintered Stainless Steel

This paper presents the results of experiments carried out on a specially designed experimental rig designed for the study of capillary pressure generated in the Loop Heat Pipe (LHP) evaporator. The commercially available porous structure made of sintered stainless steel constitutes the wick. Three different geometries of the porous wicks were tested, featuring the pore radius of 1, 3 and 7 µm. Ethanol and water as two different working fluids were tested at three different evaporator temperatures and three different installation charges. The paper firstly presents distributions of generated pressure in the LHP, indicating that the capillary pressure difference is generated in the porous structure. When installing with a wick that has a pore size of 1 μm and water as a working fluid, the pressure difference can reach up to 2.5 kPa at the installation charge of 65 mL. When installing with a wick that has a pore size of 1 μm and ethanol as a working fluid, the pressure difference can reach up to 2.1 kPa at the installation charge of 65 mL. The integral characteristics of the LHP were developed, namely, the mass flow rate vs. applied heat flux for both fluids. The results show that water offers larger pressure differences for developing the capillary pressure effect in the installation in comparison to ethanol. Additionally, this research presents the feasibility of manufacturing inexpensive LHPs with filter medium as a wick material and its influence on the LHP’s thermal performance.

Metallic Mesh as Capillary Structure Applied in Heat Pipe Heat Exchanger for Heat Recovery

2014 ◽  
Vol 1082 ◽  
pp. 309-314 ◽  
Author(s):  
Diogo L.F. Santos ◽  
Larissa S. Marquardt ◽  
Paulo H.D. Santos ◽  
Thiago Antonini Alves
Keyword(s):  
Stainless Steel ◽  
Heat Exchanger ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Working Fluid ◽  
Capillary Structure ◽  
Porous Wick ◽  
Metallic Mesh ◽  
Heat Loads ◽  
Pipe Heat

This work presents a theoretical and experimental analysis of a heat exchanger assisted by five heat pipes made of copper with a metallic mesh 100 of stainless steel which was used as capillary structure. All heat pipes used water as the working fluid and were designed based on the capillary limit model. The heat pipes were developed and tested under heat loads varying from 20 to 50 W before application into the heat exchanger. The theoretical and experimental results were compared and all heat pipes worked satisfactorily. Thereafter, it is presented the development of heat pipe heat exchanger which was tested under heat loads varying from 100 to 250 W. The highest temperature measured on the external surface of the heat pipes was 90 oC and the heat exchanger thermal efficiency varied from 74 to 80%. It is showed that the use of a stainless steel mesh as a porous wick was proved to work successfully in heat pipes.

scholarly journals Visualization Experimental Study on Silicon-Based Ultra-Thin Loop Heat Pipe Using Deionized Water as Working Fluid

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1080
Author(s):  
Wenzhe Song ◽  
Yanfeng Xu ◽  
Lihong Xue ◽  
Huajie Li ◽  
Chunsheng Guo
Keyword(s):  
Heat Pipe ◽  
Heat Dissipation ◽  
Experimental System ◽  
High Heat ◽  
Deionized Water ◽  
Working Fluid ◽  
Stable Operation ◽  
High Heat Flux ◽  
Loop Heat Pipe ◽  
Silicon Based

As a type of micro flat loop heat pipe, s-UTLHP (silicon-based ultra-thin loop heat pipe) is of great significance in the field of micro-scale heat dissipation. To prove the feasibility of s-UTLHP with high heat flux in a narrow space, it is necessary to study its heat transfer mechanism visually. In this paper, a structural design of s-UTLHP was proposed, and then, to realize the working fluid charging and visual experiment, an experimental system including a holding module, heating module, cooling module, data acquisition module, and vacuum chamber was proposed. Deionized water was selected as a working fluid in the experiment. The overall and micro phenomena of s-UTLHP during startup, as well as the evaporation and condensation phenomena of s-UTLHP during stable operation, were observed and analyzed. Finally, the failure phenomenon of s-UTLHP was analyzed, and several solutions were proposed. The observed phenomena and experimental conclusions can provide references for further related experimental research.

Experimental investigation of a loop heat pipe with R245fa and R1234ze (E) as working fluids

2021 ◽  
pp. 1-17
Author(s):  
Guangming Xu ◽  
Rongjian Xie ◽  
Nanxi Li ◽  
Cheng Liu
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Characteristic Temperature ◽  
Thermal Characteristics ◽  
Heat Pipes ◽  
Loop Heat Pipe ◽  
Working Fluids ◽  
Loop Heat Pipes ◽  
Heat Transfer Capacity ◽  
Heat Loads

Abstract Two kinds of new refrigerant-R1234ze (E) and R245fa were discussed as substitutes or supplements to traditional working fluids of loop heat pipes based on their favorable thermophysical properties and characteristics such as being safe and environmentally friendly. Thermal characteristics of a loop heat pipe with sintering copper wick at different charging ratios were experimentally investigated under variable heat loads. The results showed that the optimal charging ratio in the loop heat pipe range from 65% to 70%, and at this charging level, the R1234ze(E) system had better start-up response, while the R245fa system presented a stronger heat transfer capacity. The characteristic temperature of R1234ze(E) system was below 35 °C, and the corresponding thermal resistance was 0.08 K/W ~ 1.62 K/W under heat loads ranging from 5 W to 40 W. The thermal resistance of the R245fa system was 0.18 K/W ~ 0.91 K/W under heat loads of 10 W ~ 60 W, and the operating temperature was below 60 °C. The loop heat pipes charged with the proposed new refrigerants exhibit superb performance in room temperature applications, making them beneficial for enhancing the performance of electronics, and could provide a distinctive choice for the cooling of small-sized electronics especially.

Experimental Investigation On a Thin Loop Heat Pipe with New Evaporator Structure

2021 ◽  
Author(s):  
Ai Ueno ◽  
Shuto Tomita ◽  
Hosei Nagano
Keyword(s):  
Critical Role ◽  
Three Dimensional ◽  
Experimental Results ◽  
Working Fluid ◽  
Stable Operation ◽  
Temperature Hysteresis ◽  
Loop Heat Pipes ◽  
Operation Temperature ◽  
Transport Length

Abstract This paper presents thin loop heat pipes (tLHPs) with evaporator thickness of 1 mm and a one-way transport length of 200 mm. Grooves and liquid cores are mounted on the evaporator case in the design of a flat evaporator. Liquid cores play a critical role in reducing the pressure drop in the wick and in increasing the path length for heat transfer. A one-dimensional steady model was applied to the design of the tLHP. New tLHPs with thin evaporator (26 × 24 × t1 mm) was fabricated by a three-dimensional printer. Firstly, two kinds of tLHP systems were (type-1) fabricated with different wick materials - micro glass paper and Shirasu porous glass (SPG). Ethanol was selected as a working fluid. The experimental results showed the both LHPs can transport heat up to 12 W. Secondary, the evaporator structure was modified based on the experimental results with the type-1 tLHP, and the tLHP with SPG wick (type-2) was fabricated. The experimental results demonstrated the stable operation. The operation temperature was 83 °C, and the thermal resistance became 1.98 °C/W. The power cycle test at the range of a heat load from 5 to 10 W was also conducted. No temperature hysteresis was observed during three cycles.

Sign in / Sign up

Export Citation Format

Share Document