Thermal performance of water-based suspensions of phase change nanocapsules in a natural circulation loop with a mini-channel heat sink and heat source

2014 ◽  
Vol 64 (1-2) ◽  
pp. 376-384 ◽  
Author(s):  
C.J. Ho ◽  
Y.Z. Chen ◽  
Fong-Jou Tu ◽  
Chi-Ming Lai
Keyword(s):  
Heat Source ◽  
Phase Change ◽  
Thermal Performance ◽  
Heat Sink ◽  
Natural Circulation ◽  
Circulation Loop ◽  
Natural Circulation Loop ◽  
Water Based

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.

Two Dimensional Simulation of Heat Transfer and Fluid Flow in a Rectangular Natural Circulation Loop Containing PCM Suspensions

2004 ◽  
Author(s):  
C. J. Ho ◽  
S. Y. Chiu ◽  
J. F. Lin
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Liquid Phase ◽  
Phase Change ◽  
Natural Circulation ◽  
Circulation Loop ◽  
Freezing Process ◽  
Two Dimensional ◽  
Natural Circulation Loop ◽  
Solid Liquid

A two-dimensional numerical simulation, via a finite difference method, of fluid flow and heat transfer in a rectangular natural circulation loop is presented to explore efficacy of using solid-liquid phase change material (PCM) suspensions as a heat transfer medium. A continuum mixture flow model is used for the buoyancy-driven circulation flow of the PCM suspensions together with an approximate enthalpy model to describe the solid-liquid phase change (melting/freezing) process of the PCM particles in the loop. Parametric simulations have been conducted for the pertinent physical parameters of a loop with fixed geometrical configuration in the following ranges: the modified Rayleigh number Ra* = 109 ∼ 1013, the modified Stefan number Ste* = 0.05 ∼ 0.5, the particle volumetric fraction cv = 0 ∼ 20%, and the modified subcooling factor Sb* = 0∼2.0. The melting/freezing processes of the PCM particles at the heated/cooled sections of the loop are closely interrelated in their inlet conditions of the suspension. Closer examination of numerical results reveals that there could be a flow regime in the parametric domain where heat transfer performance of the suspension circulation loop is significantly enhanced, due to contribution of the latent heat transport associated with melting/freezing of PCM particles.

Steady-State Performance of a Rectangular Natural Circulation Loop With Differentially Heated Parallel Channels

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
Shubhankar Chakraborty ◽  
Prasanta Kr. Das
Keyword(s):  
Steady State ◽  
Phase Change ◽  
Energy Transport ◽  
Natural Circulation ◽  
Circulation Loop ◽  
Circulation Rate ◽  
Working Fluid ◽  
Two Phase ◽  
State Behavior ◽  
Natural Circulation Loop

Natural circulation loop (NCL) transfers thermal energy without using any external power. As with phase change, one can expect a higher rate of heat transfer and a greater change in density, NCL with a phase change of the circulating fluid is a more effective energy transfer device. Though in many of the practical NCLs there are multiple heating risers, the characteristics of NCLs with parallel boiling risers have not been investigated in detail. In the present work, the steady-state behavior of a two-phase NCL with two parallel boiling risers for water as the working fluid has been investigated. Emphasis has been given to the performance of the loop when the risers are differentially heated. Effect of different parameters on the loop circulation rate and energy transport for both equally and differentially heated conditions has been thoroughly examined and compared to the performance of a single-riser loop under equivalent working condition.

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