Natural circulation pump with asymmetrical heat transfer wall as the element of Büttiker–Landauer thermal ratchet

2020 ◽  
Vol 32 (11) ◽  
pp. 112016
Author(s):  
Hideyuki Sugioka ◽  
Yusuke Someya
Keyword(s):  
Heat Transfer ◽  
Natural Circulation ◽  
Circulation Pump

Thermal Performance of Water-Based Suspensions of Phase Change Nanocapsules in a Natural Circulation Loop

2013 ◽  
Author(s):  
C. J. Ho ◽  
Chi-Ming Lai
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Natural Circulation ◽  
Pure Water ◽  
Circulation Loop ◽  
Core Material ◽  
Working Fluid ◽  
Outer Diameter ◽  
Natural Circulation Loop ◽  
Water Based

Experiments were conducted to investigate the heat transfer characteristics of water-based suspensions of phase change nanocapsules in a natural circulation loop with mini-channel heat sinks and heat sources. A total of 23 and 34 rectangular mini-channels, each with width 0.8 mm, depth 1.2 mm, length 50 mm and hydraulic diameter 0.96 mm, were evenly placed on the copper blocks as the heat source and heat sink, respectively. The adiabatic sections of the circulation loop were constructed using PMMA tubes with an outer diameter of 6 mm and an inner diameter of 4 mm, which were fabricated and assembled to construct a rectangular loop with a height of 630 mm and a width of 220 mm. Using a core material of n-eicosane and a shell of urea-formaldehyde resin, the phase change material nanocapsules of mean particle size 150 nm were fabricated successfully and then dispersed in pure water as the working fluid to form the water-based suspensions with mass fractions of the nanocapsules in the range 0.1–1 wt.%. The results clearly indicate that water-based suspensions of phase change nanocapsules can markedly enhance the heat transfer performance of the natural circulation loop considered.

A Natural Circulation Model of the Closed Loop, Two-Phase Thermosyphon for Electronics Cooling

2001 ◽  
Author(s):  
S. I. Haider ◽  
Yogendra K. Joshi ◽  
Wataru Nakayama
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Closed Loop ◽  
Two Phase Flow ◽  
Natural Circulation ◽  
Saturation Temperature ◽  
Electronics Cooling ◽  
Phase Flow ◽  
Two Phase

Abstract The study presents a model for the two-phase flow and heat transfer in the closed loop, two-phase thermosyphon (CLTPT) involving co-current natural circulation. Most available models deal with two-phase thermosyphons with counter-current circulation within a closed, vertical, wickless heat pipe. The present research focuses on CLTPTs for electronics cooling that face more complex two-phase flow patterns than the vertical heat pipes, due to closed loop geometry and smaller tube size. The present model is based on mass, momentum, and energy balances in the evaporator, rising tube, condenser, and the falling tube. The homogeneous two-phase flow model is used to evaluate the friction pressure drop of the two-phase flow imposed by the available gravitational head through the loop. The saturation temperature dictates both the chip temperature and the condenser heat rejection capacity. Thermodynamic constraints are applied to model the saturation temperature, which also depends upon the local heat transfer coefficient and the two-phase flow patterns inside the condenser. The boiling characteristics of the enhanced structure are used to predict the chip temperature. The model is compared with experimental data for dielectric working fluid PF-5060 and is in general agreement with the observed trends. The degradation of condensation heat transfer coefficient due to diminished vapor convective effects, and the presence of subcooled liquid in the condenser are expected to cause higher thermal resistance at low heat fluxes. The local condensation heat transfer coefficient is a major area of uncertainty.

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