A Numerical Study on Taylor Flow Heat Transfer in Square Microchannels Under Constant Wall Temperature Boundary Condition

2012 ◽  
Author(s):  
V. Talimi ◽  
Y. S. Muzychka ◽  
S. Kocabiyik
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Transfer Process ◽  
Wall Temperature ◽  
Heat Transfer Process ◽  
Constant Wall Temperature ◽  
Temperature Boundary ◽  
Slug Flows ◽  
Temperature Boundary Condition

Heat transfer in Taylor flows or slug flows has been examined exclusively by researchers. Noncircular microchannels have not been widely considered in the literature. There is a large gap in research since noncircular microchannels are common structures in microcooling processes. Square and rectangular microchannels are the most important examples. In the present study the heat transfer process in slug flows in square microchannels has been investigated numerically under constant wall temperature boundary condition. The local heat flux for the moving slugs has been converted to total microchannel heat flux using the integration methods suggested recently by the authors. This leads to microchannel wall average heat flux which is the parameter of interest in heat sink problems. Finally, effects of liquid film around bubbles on heat transfer process have been discussed.

Analysis of Effect of Fouling on Thermodynamic Performance of Convective Heat Transfer Process Through a Duct

2002 ◽  
Author(s):  
Shuangying Wu ◽  
Danling Zeng
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convective Heat Transfer ◽  
Transfer Process ◽  
Wall Temperature ◽  
Transfer Rate ◽  
Heat Transfer Process ◽  
Constant Wall Temperature ◽  
Thermodynamic Performance ◽  
Increase Rate

Based on the first and second laws of thermodynamics simultaneously, the effect of fouling on the thermodynamic performance of convective heat transfer process through a duct with constant wall temperature and constant heat flux is investigated analytically when the flow is turbulent. A criterion evaluating the effect of fouling is defined as the entropy generation increase rate per unit heat transfer rate. The effect of Reynolds number (not considering fouling) and dimensionless inlet temperature difference and dimensionless wall heat flux on the entropy generation increase rate per unit heat transfer rate is discussed. In addition, the results with constant wall temperature are compared with that with constant wall heat flux.

Shear work, viscous dissipation and axial conduction effects on microchannel heat transfer with a constant wall temperature

2015 ◽  
Vol 230 (14) ◽  
pp. 2496-2507 ◽  
Author(s):  
K Ramadan ◽  
Iskander Tlili
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Wall Temperature ◽  
Slip Flow ◽  
Brinkman Number ◽  
Constant Wall Temperature ◽  
Fully Developed Flow ◽  
Boundary Shear ◽  
Temperature Boundary ◽  
Temperature Boundary Condition

Convective heat transfer in a microchannel rarefied gas flow with a constant wall temperature boundary condition is investigated numerically. The boundary shear work, viscous dissipation and axial conduction are all included in the study. An analytical solution is also derived for the fully developed flow condition including the boundary shear work. The proper thermal boundary condition considering the sliding friction at the wall is implemented. A comparative study is performed to quantify the effect of the shear work on heat transfer in the entrance – and the fully developed – regions of the microchannel for both gas cooling and heating. The results demonstrate that the effect of shear work on heat transfer is significant and it increases with increasing both the Knudsen number and Brinkman number. Neglecting the shear work in a microchannel slip flow leads to over- or under estimation of the Nusselt number considerably. For a fully developed flow in a microchannel with constant wall temperature boundary condition, the contribution of the shear work to heat transfer can be around 55% in the vicinity of the upper limit of the slip flow regime, regardless of how small the non-zero Brinkman number can be. Including the shear work is therefore crucial in the analysis of microchannel heat transfer and should not be neglected.

Transient Heat Transfer of Piston/Rings/Liner System in Diesel Engines

2005 ◽  
Author(s):  
Daxi Xiong ◽  
Tian Tian ◽  
Victor Wong
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Transfer Process ◽  
Diesel Engines ◽  
Frictional Heating ◽  
Heat Transfer Process ◽  
Transient Heat Transfer ◽  
Transient Temperature ◽  
Piston Rings ◽  
Liner System

In diesel engines, transient heat transfer in the piston/rings/liner system greatly affects the performance of the engine, such as in carbon deposit buildup, microwelding, lubricant degradation, and changing mechanical properties of the materials. The current work aims at studying the local piston/rings/liner transient heat-transfer process by incorporating real time dynamics of the rings in sufficient detail. In the present study, several techniques have been adopted to simulate the transient heat transfer process, with fully-incorporated ring dynamics. These techniques include using the model/submodel approach, local refined mesh approach, and the virtual thermal conductivity approach. The transient temperature and heat flux profiles in the piston and rings are illustrated. The results show that the relative movement of the rings greatly affects the temperature/heat flux distribution and the peak temperature in the top ring. The friction heating between the top ring and the liner is also evaluated. The analysis demonstrates that under some extreme conditions when frictional heating reaches its peak value, some heat flux directs back to enter the ring.

Sign in / Sign up

Export Citation Format

Share Document