scholarly journals Thermal Transfer Characteristics of Flat Plate Micro Heat Pipe with Copper Spiral Woven Mesh and a Copper Foam Composite Wick

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 2821
Author(s):  
Yanhui Zhang ◽  
Zhengang Zhao ◽  
Chuan Luo ◽  
Dacheng Zhang
Keyword(s):  
Thermal Resistance ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Thermal Power ◽  
Transfer Performance ◽  
Filling Rate ◽  
Thermal Transfer ◽  
Copper Foam ◽  
Foam Composite ◽  
Wick Structure

The thermal efficiency limitation of the Flat-plate Micro Heat Pipe (FMHP) is a major challenge in the development of the FMHP, where the effect of wick structure and wettability on its thermal performance is studied to improve the thermal efficiency of the FMHP. In this work, a copper spiral woven mesh and copper foam Composite Wick FMHP (CW-FMHP) is designed based on the conventional Copper Foam Wick FMHP (CFW-FMHP), and its thermal performance is analyzed regarding the wick structure and internal gas–liquid two-phase flow characteristics. An oxidized copper spiral woven mesh and copper foam Composite Wick FMHP (OCW-FMHP) has been further developed through the modification of composite wick wettability. The performance tests are carried out with the thermal transfer characteristics of CW-FMHP, OCW-FMHP, and CFW-FMHP under different filling rates and different thermal powers. The experimental results show that the thermal transfer performance of CW-FMHP reaches the optimal under a liquid filling rate of 150%, where the maximum thermal power is 15.7 W, 35.3% higher than that of the CFW-FMHP under the same filling rate. Moreover, the dynamic response characteristics of the CW-FMHP are significantly improved. The thermal resistance of the CW-FMHP is 0.48 ∘C/W under the filling rate of 150% at the thermal power of 10 W with a reduction of 9.4% compared to the CFW-FMHP under the same condition. Furthermore, the optimal filling rate for OCW-FMHP is lower compared with the CW-FMHP. The maximum thermal power of OCW-FMHP increases to 17.8 W while the thermal resistance reduces to 0.34 ∘C/W under the liquid filling rate of 140%. This implies that the composite wick structure designed in this work can improve the thermal transfer performance of the FMHP, and the composite wick with wettability modification is more effective regarding both thermal resistance and maximum thermal power.

Experimental Study of Thermal Performance of Nanofluid-Filled and Nanoparticles-Coated Mesh Wick Heat Pipes

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Naveen Kumar Gupta ◽  
Arun Kumar Tiwari ◽  
Subrata Kumar Ghosh
Keyword(s):  
Thermal Resistance ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Physical Vapor Deposition ◽  
Power Input ◽  
Working Fluid ◽  
Physical Vapor Deposition Method ◽  
The Stability ◽  
Stability Issues ◽  
Time Of Operation

The enhancements in thermal performance of mesh wick heat pipe (HP) using TiO2/H2O nanofluid (0.5, 1.0, and 1.5 vol %) as working fluid for different (50, 100, and 150 W) power input were investigated. Results showed maximum 17.2% reduction in thermal resistance and maximum 13.4% enhancement in thermal efficiency of HP using 1.0 vol % nanofluid as compared to water. The wick surface of the HP was then coated with TiO2 nanoparticles by physical vapor deposition method. The experimental investigation had been also carried out on coated wick HP using water as working fluid. Results showed 12.1% reduction in thermal resistance and 11.9% enhancement in thermal efficiency of the HP as compared to uncoated wick HP using water. Temporal deteriorations in thermal performance during prolonged working (2, 4, and 6 months) of HP were also studied. Temporal deterioration in thermal performance of HP filled with nanofluid depends upon the deterioration in thermophysical properties of nanofluids. The deterioration is due to the agglomeration and sedimentation of nanoparticles with respect to the time. Comparative study shows that after a certain time of operation, thermal performance of HP with nanoparticle coated wick superseded that of the HP filled with nanofluid. Therefore, nanoparticle coating might be a good substitute for nanofluid to avoid the stability issues. The present paper provides incentives for further research to develop nanofluids that avoid the encountered sedimentation or agglomeration.

scholarly journals Study on Heat Transfer Performance of Non-integral Capillary Core Sintered Uniform Plate

2021 ◽  
Vol 7 (5) ◽  
pp. 292-301
Keyword(s):  
Heat Transfer ◽  
Particle Size ◽  
Heat Source ◽  
Thermal Resistance ◽  
Copper Powder ◽  
Heat Transfer Performance ◽  
Copper Plate ◽  
Transfer Performance ◽  
Filling Rate ◽  
Large Particle Size

This paper mainly introduces the sintering process of the monolithic capillary wick and analyzes the influence of different copper powder particle size, filling rate, copper powder shape and heat source size on the heat transfer performance of the isothermal plate. The experimental results show that: (1) For the isothermal plate sintered with spherical copper powder, the capillary force of large particle size copper powder is small, but the flow resistance is also small, and the performance of the isothermal plate sintered with large particle size copper powder is better. (2) In the case of low filling rate, the isothermal plate is dried due to insufficient return fluid. In the case of high filling rate, on the one hand, the thickness of the liquid film at the evaporation end of the isothermal plate is large, resulting in additional thermal resistance. On the other hand, the thin film evaporation mode will be transformed into pool boiling mode, which will reduce the heat transfer performance. (3) Spherical copper powder sintered plate with regular shape has the best performance, while dendritic copper powder sintered plate has relatively high thermal resistance. (4) The heat source area has a great influence on the thermal resistance of the plate. Under the same heating power, the thermal resistance of the small area heat source is much higher than that of the large area heat source; The thermal resistance of sintered copper plate is lower than that of pure copper plate under two heat source areas.

Variation of Plant Electrical Output Due to Main Steam Temperature and Thermal Power

2010 ◽  
Author(s):  
D. W. Yoon ◽  
C. K. Park ◽  
B. H. Lee ◽  
K. C. Jeong
Keyword(s):  
Power Plant ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Thermal Power ◽  
Heat Rate ◽  
Steam Temperature ◽  
Turbine Inlet ◽  
Thermodynamic Performance ◽  
Main Steam ◽  
Electrical Output

As a measure of power plant thermodynamic performance, heat rate (H.R.) is used. As heat rate is inversely proportional to thermal efficiency, the thermal efficiency of a power plant increases as the heat rate decreases. The major thermodynamic performance parameters in a plant thermal cycle affecting the electrical output include but are not limited to: the initial pressure of main steam at the turbine inlet, the initial moisture content or superheated condition of main steam at the turbine inlet, the effectiveness of the feedwater heating cycle, the effectiveness of the moisture separator, the effectiveness of the reheater, the condenser pressure, the level of cycle separation and the accuracy of electric output measurement. A review of thermodynamic principles involved in a thermal performance plan is needed to understand the changes in the parameters and recognize the thermal performance status and trends, which will lead us to propose corrective actions when appropriate. This paper focuses on the effects of main steam temperature and thermal power.

Thermal Performance of Carbon Nanotube Enhanced Vapor Chamber Wicks

2010 ◽  
Author(s):  
Sungwon S. Kim ◽  
Justin A. Weibel ◽  
Timothy S. Fisher ◽  
Suresh V. Garimella
Keyword(s):  
Carbon Nanotubes ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Positive Bias ◽  
Maximum Heat ◽  
Capillary Action ◽  
Wick Structure ◽  
Copper Mesh

Vapor chambers are often used as spreaders to dissipate high heat fluxes by taking advantage of liquid-vapor phase change. Wicking of the working fluid in vapor chambers is accomplished through capillary action, which is strongly affected by the wick structure. Traditionally, copper meshes with micrometer-scale pore sizes have been used as wicking structures, but it is expected that heat fluxes in the next generation of high-power electronic devices will cause boiling in these devices and lead to dryout with conventional wick materials. With a goal of increasing maximum heat dissipation and reducing thermal resistance, a wick structure composed of both conventional copper mesh and carbon nanotubes has been developed and characterized. The high-permeability mesh provides for a low-resistance bulk flow path while the carbon nanotubes, with their high thermal conductivity and high surface area, modify the wick surface for enhanced capillary action. CNT-enhanced integrated wicks were fabricated by sintering a copper mesh on Cu-Mo-Cu substrates, on which CNTs were grown. A thin layer of copper was evaporated onto the CNTs to improve wicking and wettability with water, the working fluid of interest. Samples grown under varying degrees of positive bias voltage and varying thicknesses of post-CNT-growth copper evaporation were fabricated, so that the surface morphology of the samples could be varied. The resultant boiling curves and associated wick thermal resistances indicate that micro/nano integrated wicks fabricated with higher positive bias voltages during CNT synthesis, and thicker copper coatings, lead to improved thermal performance and lower wick thermal resistance. Notably, heat fluxes at the heater surface of greater than 500 W/cm2 were observed without reaching a critical heat flux condition.

Heat Transfer Performance of a Parabolic Trough Receiver Using SWCNTs-Therminol®VP-1 Nanofluids

2017 ◽  
Author(s):  
Aggrey Mwesigye ◽  
Josua P. Meyer
Keyword(s):  
Heat Transfer ◽  
Solar Energy ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Concentration Ratio ◽  
Heat Transfer Performance ◽  
Energy System ◽  
Transfer Performance ◽  
Parabolic Trough ◽  
Flow Rates

In this paper, the potential for improved thermal performance of a high concentration ratio parabolic trough solar energy system working with high thermal conductivity single-walled carbon nanotubes (SWCNTs) and Therminol®VP-1 nanofluid is numerically investigated. In the numerical analysis, the practical heat flux profiles expected for parabolic trough receivers were obtained using Monte-Carlo ray tracing and coupled with a computational fluid dynamics tool using user defined functions to investigate the thermal performance of the parabolic trough solar energy system. A parabolic trough system with a concentration ratio of 113 was considered in this study and heat transfer fluid inlet temperatures between 400 K and 650 K were used. The volume fraction of SWCNTs in the base fluid was in the range 0% to 2.5% and the flow rates used were in the range 0.82 to 69.41 m3/h. Results show improvements in the convective heat transfer performance and receiver thermal efficiency as well as a considerable reduction of the receiver thermal losses with increasing volume fractions. The heat transfer performance increases up to 64% while the thermal efficiency increases by about 4.4%. Higher increments are observed at low flow rates and inlet temperatures. The receiver thermodynamic performance also increases significantly with the use of nanofluids. Entropy generation rates reduce by about 30% for the range of parameters considered.

Study of Influence Effect on Heat Transfer Performance of Single-Loop Oscillating Heat Pipe

2014 ◽  
Vol 535 ◽  
pp. 114-118 ◽  
Author(s):  
Su Lei
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Filling Rate ◽  
Oscillating Heat Pipe ◽  
Heating Section ◽  
Cooling Section

s. The experiment studied the effect of heat source temperature, heating section length ratio, cooling air flow rate, liquid filling rate and pipe diameter on the heat transfer performance of the single-loop red copper-water oscillating heat pipe. The results show that increasing heat source temperature or pipe diameter and reducing filling rate can obviously reduce the thermal resistance of the heat pipe; in the air cooling mode, the cooling thermal resistance outside the pipe is affected by both cooling conditions and heat pipe cooling section average temperature; when the heating section is shorter than the cooling section, the heat pipe thermal resistance shows an apparent trend of increasing with the increase of heating section length ratio, when the heating section is longer than the cooling section, the cooling thermal resistance increases with it apparently; the heat transfer power is the highest when the filling rate is 50%.

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