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.

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.

On the Convective Heat Transfer in a Tube of Elliptic Cross Section Maintained Under Constant Wall Temperature

1986 ◽  
Vol 108 (1) ◽  
pp. 33-39 ◽  
Author(s):  
M. A. Ebadian ◽  
H. C. Topakoglu ◽  
O. A. Arnas
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Temperature Distribution ◽  
Convective Heat Transfer ◽  
Cross Section ◽  
Convective Heat ◽  
Wall Temperature ◽  
Elliptic Cross Section ◽  
Constant Wall Temperature ◽  
Elliptic Cross

The convective heat transfer problem along the portion of a tube of elliptic cross section maintained under a constant wall temperature where hydrodynamically and thermally fully developed flow conditions prevail is solved in this paper. The successive approximation method is used for the solution utilizing elliptic coordinates. Analytical expressions for temperature distribution and Nusselt number corresponding to the first cycle of approximation are obtained in terms of the ellipticity of the cross section. In the case of a circular section, the first cycle approximation of the Nusselt number is obtained as 3.7288 compared to the exact value of 3.6568. Representative temperature distribution curves are plotted and compared to those corresponding with constant wall heat flux conditions.

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.

scholarly journals Modelling heat transfer in heterogeneous media using fractional calculus

2013 ◽  
Vol 371 (1990) ◽  
pp. 20120146 ◽  
Author(s):  
Dominik Sierociuk ◽  
Andrzej Dzieliński ◽  
Grzegorz Sarwas ◽  
Ivo Petras ◽  
Igor Podlubny ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Differential Equation ◽  
Partial Differential Equation ◽  
Heat Flux ◽  
Transfer Function ◽  
Transfer Process ◽  
Heterogeneous Media ◽  
Heat Transfer Process ◽  
Order Partial Differential Equation ◽  
Partial Differential

This paper presents the results of modelling the heat transfer process in heterogeneous media with the assumption that part of the heat flux is dispersed in the air around the beam. The heat transfer process in a solid material (beam) can be described by an integer order partial differential equation. However, in heterogeneous media, it can be described by a sub- or hyperdiffusion equation which results in a fractional order partial differential equation. Taking into consideration that part of the heat flux is dispersed into the neighbouring environment we additionally modify the main relation between heat flux and the temperature, and we obtain in this case the heat transfer equation in a new form. This leads to the transfer function that describes the dependency between the heat flux at the beginning of the beam and the temperature at a given distance. This article also presents the experimental results of modelling real plant in the frequency domain based on the obtained transfer function.

Investigation of Convective Heat Transfer of Aqueous Nanofluids in Microchannels Integrated With Temperature Nanosensors

2011 ◽  
Author(s):  
Jiwon Yu ◽  
Seok-won Kang ◽  
Saeil Jeon ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Wall Temperature ◽  
Pure Water ◽  
Bulk Temperature ◽  
Inlet Temperature ◽  
Experimental Conditions ◽  
Forced Convective Heat Transfer

Forced convective heat transfer experiments were performed for internal flow of de-ionized water (DIW) and aqueous nanofluids (ANF) in microchannels that were integrated with a calorimeter apparatus and an array of temperature nanosensors. The heat flux and wall temperature distribution was measured for the different test fluids as a function of fluid inlet temperature, wall temperature, heat flux, nanoparticles concentration, nanoparticle materials (composition, nanoparticle size and shape) and flow rates. Anomalous behavior of the nanofluids in convective heat transfer was observed where the heat flux varied as a function of flow rate and bulk temperature. The heat exchanging surfaces were characterized using electron microscopy (SEM, TEM) to monitor the change in surface characteristics both before and after the experiments. Precipitation of nanoparticles on the walls of the microchannels can lead to the formation of “nano-fins” at low concentrations of the nanoparticles while more rampant precipitation at high concentration of the nanoparticles in the nanofluids can lead to scaling (fouling) of the microchannel surfaces leading to degradation of convective heat transfer — compared to that of pure water under the same experimental conditions. Also, competing effects resulting from the decrease in the specific heat capacity as well as anomalous enhancement in the thermal conductivity of aqueous nanofluids can lead to counter-intuitive behavior of these test liquids during forced convective heat transfer.

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