scholarly journals Effect of Tube Number on Critical Heat Flux and Thermal Performance in Linear Fresnel Collector Based on Direct Steam Generation

2020 ◽  
Vol 38 (1) ◽  
pp. 223-230 ◽  
Author(s):  
Najmeh Salehi ◽  
Arash Lavasani ◽  
Ramin Mehdipour
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Thermal Performance ◽  
Steam Generation ◽  
Tube Number ◽  
Direct Steam

scholarly journals Experimental Study on Thermal Performance of a Bent Copper-Water Heat Pipe

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Shuangshuang Miao ◽  
Jiajia Sui ◽  
Yulong Zhang ◽  
Feng Yao ◽  
Xiangdong Liu
Keyword(s):  
Heat Flux ◽  
Heat Pipe ◽  
Critical Heat Flux ◽  
Working Conditions ◽  
Thermal Performance ◽  
Heat Input ◽  
High Heat ◽  
High Heat Flux ◽  
Electronic Components ◽  
Copper Water

Vapor-liquid phase change is regarded as an efficient cooling method for high-heat-flux electronic components. The copper-water bent heat pipes are particularly suited to the circumstances of confined space or misplaced heat and cold sources for high-heat-flux electronic components. In this paper, the steady and transient thermal performance of a bent copper-water heat pipe is studied based on a performance test system. The effects of cooling temperature, working conditions on the critical heat flux, and equivalent thermal conductivity have been examined and analyzed. Moreover, the influences of heat input and working conditions on the thermal response of a bent heat pipe have also been discussed. The results indicate that the critical heat flux is enhanced due to the increases in cooling temperature and the lengths of the evaporator and condenser. In addition, the critical heat flux is improved by extending the cooling length only when the operating temperature is higher than 50°C. The improvement on the equivalent thermal by increasing the heating length is more evident than that by increasing cooling length. It is also demonstrated by the experiment that the bent copper-water heat pipe can respond quickly to the variation of heat input and possesses superior transient heat transfer performance.

Towards a Durable Polymeric Internal Coating for Diabatic Sections in Wickless Heat Pipes

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Fabio Villa ◽  
Marco Marengo ◽  
Joël De Coninck
Keyword(s):  
Heat Flux ◽  
Heat Pipe ◽  
Surface Properties ◽  
Critical Heat Flux ◽  
Thermal Performance ◽  
Heat Pipes ◽  
Surface Wettability ◽  
Polymeric Coating ◽  
Stainless Steel Surface ◽  
Power Load

Heat pipe characteristics are linked to the surface properties of the diabatic surfaces, and, in the evaporator, surface properties influence both the onset boiling temperature (TONB) and the critical heat flux (CHF). In this work, the effect of surface wettability in pool boiling heat transfer is studied in order to understand if there could be a path to increment heat pipe thermal performance. This work analyzes the effects of surface wettability on boiling (tested fluid is pure water) and proposes a new super-hydrophobic polymeric coating (De Coninck et al., 2017, “Omniphobic Surface Coatings,” Patent No. WO/2017/220591), which can have a very important effect in improving the heat pipe start-up power load and increasing the thermal performance of heat pipes when the flux is lower than the critical heat flux. The polymeric coating is able to reduce the TONB (−11% from 117 °C to about 104 °C) compared with the uncoated surfaces, as it inhibits the formation of a vapor film on the solid–liquid interface, avoiding CHF conditions up to maximum wall temperature (125 °C). This is realized by the creation of a heterogeneous surface with superhydrophobic surface (SHS) zones dispersed on top of a hydrophilic surface (stainless steel surface). The proposed coating has an outstanding thermal resistance: No degradation of SH properties of the coating has been observed after more than 500 thermal cycles.

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