Performance of Gas-to-Gas Micro-Heat Exchangers

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
J. Miwa ◽  
Y. Asako ◽  
C. Hong ◽  
M. Faghri
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Temperature Inversion ◽  
Channel Height ◽  
Arbitrary Lagrangian Eulerian ◽  
Flux Variation ◽  
Counter Flow ◽  
Numerical Result ◽  
Arbitrary Lagrangian Eulerian Method

Heat transfer performance of two-stream parallel and counter-flow gas-to-gas micro-heat exchangers are investigated numerically. Flow passages are plane channels with heights in the range of 10–100μm and selected lengths of 12.7mm and 25.4mm. Numerical methodology is based on the arbitrary-Lagrangian-Eulerian method. Computations were performed to find the effects of capacity ratio, channel height, and length on the heat transfer characteristics of micro-heat exchangers. To results are presented in the form of temperature contours, bulk temperatures, total temperatures, and heat flux variation along the channel. It was found that the temperature inversion occurs under certain conditions. Also, the effectiveness and the number of transfer units approach and the estimation of the heat exchange rate were discussed. The range of parameters where the predicted effectiveness agrees with the numerical result were investigated.

Performance of Gaseous Counter-Flow Micro Heat Exchangers

2007 ◽  
Author(s):  
J. Miwa ◽  
C. Hong ◽  
Y. Asako ◽  
M. Faghri
Keyword(s):  
Heat Flux ◽  
Heat Exchange ◽  
Heat Exchangers ◽  
Parallel Plate ◽  
Channel Height ◽  
Arbitrary Lagrangian Eulerian ◽  
Flux Variation ◽  
Counter Flow ◽  
Eulerian Method ◽  
Arbitrary Lagrangian Eulerian Method

Heat exchangers performance of two-stream counter-flow gas-gas type micro-heat exchangers is investigated numerically. The flow passages of the micro-heat exchangers are parallel-plate channels with heights in the range of 10 to 100 μm and selected lengths of 12.7 and 25.4 mm. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian method. The computations were performed to find the effects of capacity ratio, channel height and length on the heat exchange characteristics of micro heat exchangers. The results are presented in form of temperature contours, bulk temperatures, total temperatures and heat flux variation along the channel. Also, the correlation between the effectiveness and Ntu is discussed.

Performance of Gaseous Parallel-Flow Micro Heat Exchangers

2006 ◽  
Author(s):  
Y. Asako ◽  
C. Hong ◽  
J. Miwa ◽  
M. Faghri
Keyword(s):  
Heat Flux ◽  
Heat Exchange ◽  
Heat Exchangers ◽  
Parallel Plate ◽  
Parallel Flow ◽  
Channel Height ◽  
Arbitrary Lagrangian Eulerian ◽  
Flux Variation ◽  
Eulerian Method ◽  
Arbitrary Lagrangian Eulerian Method

Heat exchangers performance of two-stream parallel-flow gas-gas type micro-heat exchangers is investigated numerically. The flow passages of the micro-heat exchangers are parallel-plate channels with heights in the range of 10 to 100 μm and selected lengths of 12.7 and 25.4 mm. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian method. The computations were performed to find the effects of capacity ratio, channel height and length on the heat exchange characteristics of micro heat exchangers. The results are presented in form of temperature contours, bulk temperatures, total temperatures and heat flux variation along the channel. Also, the correlation between the effectiveness and Ntu is discussed.

Heat Transfer of a Double Layer Microchannel Heat Sink

2013 ◽  
Vol 479-480 ◽  
pp. 411-415 ◽  
Author(s):  
Wong Kok Cheong ◽  
Fashli Nazhirin bin Ahmad Muezzin
Keyword(s):  
Heat Transfer ◽  
Double Layer ◽  
Heat Sink ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Channel Width ◽  
Channel Height ◽  
Physical Parameters ◽  
Microchannel Heat Sink ◽  
Counter Flow

A numerical study is conducted to predict the effects of physical parameters of a double layer microchannel heat sink on heat transfer. The physical parameters investigated are the channel height and channel width for different flow orientation at the upper and lower channels. For the range of Reynolds number investigated, results show that parallel flow configuration leads to better heat transfer performance than counter flow. Lower thermal resistance can be achieved in a double-layered microchannel heat sink with higher channel height and lower channel width.

Numerical and Experimental Study on Temperature Crossover in Shell and Tube Heat Exchangers

2011 ◽  
Vol 7 (4) ◽  
Author(s):  
Fuhua Jiang ◽  
Xianhe Deng
Keyword(s):  
Heat Transfer ◽  
Food Processing ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Counter Flow ◽  
Numerical Studies ◽  
Shell And Tube ◽  
First Time ◽  
The Relationship ◽  
Dynamics Method

Experimental and numerical studies were conducted to investigate the heat transfer characteristics of five shell and tube heat exchangers (STHXs) with ratio of the length to width (L/W) at the range of 1.85 to 9.23. Temperature crossover in counter flow STHXs is meaningful in food processing industry. The relationship between temperature crossover and L/W is proposed for the first time. Both the experimental and numerical results show that temperature crossover can be achieved in STHXs with L/W?4.62 and can’t be achieved any more in STHXs with L/W?3.08. The results also indicate that heat transfer performance decreases with L/W decreasing. The inherent reason of this phenomenon is analyzed by computational fluid dynamics method.

Visualization of Boiling Heat Transfer on Micro Porous Coated Surface in Confined Space

2013 ◽  
Author(s):  
Chien-Yuh Yang ◽  
Chien-Fu Liu
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Boiling Heat Transfer ◽  
Heat Transfer Performance ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Confined Space ◽  
Two Phase ◽  
Nucleate Boiling Heat Transfer ◽  
Coated Surface

Numerous researches have been developed for pool boiling on microporous coated surface in the past decade. The nucleate boiling heat transfer was found to be increased by up to 4.5 times than that on uncoated surface. Recently, the two-phase micro heat exchangers have been considered for high flux electronic devices cooling. The enhancement techniques for improving the nucleate boiling heat transfer performance in the micro heat exchangers have gotten more importance. Previous studies of microporous coatings, however, have been restricted to boiling in unconfined space. No studies have been made on the feasibility of using microporous coatings for enhancing boiling in confined spaces. This study provides an experimental observation of the vapor generation and leaving processes on microporous coatings surface in a 1-mm confined space. It would be helpful for understanding the mechanism of boiling heat transfer and improving the design of two-phase micro heat exchangers. Aluminum particles of average diameter 20 μm were mixed with a binder and a carrier to develop a 150 μm thickness boiling enhancement paint on a 3.0 cm by 3.0 cm copper heating surface. The heating surface was covered by a thin glass plate with a 1 mm spacer to form a 1 mm vertical narrow space for the test section. The boiling phenomenon was recorded by a high speed camera. In addition to the three boiling regimes observed by Bonjour and Lallemand [1], i.e., isolated deformed bubbles, coalesced bubbles and partial dryout at low, moderate and high heat fluxes respectively in unconfined space, a suction and blowing process was observed at the highest heat flux condition. Owing to the space confinement, liquid was sucked and vapor was expelled periodically during the bubble generation process. This mechanism significantly enhanced the boiling heat transfer performance in confined space.

Heat Transfer Performance of Different Nanofluids Flows in a Helically Coiled Heat Exchanger

2013 ◽  
Vol 832 ◽  
pp. 160-165 ◽  
Author(s):  
Mohammad Alam Khairul ◽  
Rahman Saidur ◽  
Altab Hossain ◽  
Mohammad Abdul Alim ◽  
Islam Mohammed Mahbubul
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Volume Concentration ◽  
Transfer Performance

Helically coiled heat exchangers are globally used in various industrial applications for their high heat transfer performance and compact size. Nanofluids can provide excellent thermal performance of this type of heat exchangers. In the present study, the effect of different nanofluids on the heat transfer performance in a helically coiled heat exchanger is examined. Four different types of nanofluids CuO/water, Al2O3/water, SiO2/water, and ZnO/water with volume fractions 1 vol.% to 4 vol.% was used throughout this analysis and volume flow rate was remained constant at 3 LPM. Results show that the heat transfer coefficient is high for higher particle volume concentration of CuO/water, Al2O3/water and ZnO/water nanofluids, while the values of the friction factor and pressure drop significantly increase with the increase of nanoparticle volume concentration. On the contrary, low heat transfer coefficient was found in higher concentration of SiO2/water nanofluids. The highest enhancement of heat transfer coefficient and lowest friction factor occurred for CuO/water nanofluids among the four nanofluids. However, highest friction factor and lowest heat transfer coefficient were found for SiO2/water nanofluids. The results reveal that, CuO/water nanofluids indicate significant heat transfer performance for helically coiled heat exchanger systems though this nanofluids exhibits higher pressure drop.

The Curvature Effect on the Heat Transfer at the End of a Bayonet Tube With Laminar Flows

2004 ◽  
Author(s):  
F. Sun ◽  
H. Li ◽  
J. Drummond ◽  
G.-X. Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Average Nusselt Number ◽  
Heat Transfer Performance ◽  
Laminar Flows ◽  
Transfer Performance ◽  
Curvature Effect ◽  
Flow And Heat Transfer ◽  
Cooling Agent ◽  
Annular Section

Bayonet tubes, simple refluent heat exchangers, are widely used to heat or cool a media when the heating/cooling agent is readily accessible from one side only. Many studies have been conducted to evaluate the heat transfer performance of bayonet tubes. The majority of these studies focus on the heat transfer in the annular section and little on the end surface. This paper presents a numerical simulation of the laminar flow and heat transfer in a bayonet tube. The simulation is first validated by the experimental data in the literature. The flow and heat transfer in bayonet tubes are then investigated with both flat and curved end surfaces. Both local and average Nusselt number on the end surfaces are calculated under various Re and geometry conditions. Effect of the end surface curvature is studied by comparing the performances of the flat and curved ended bayonet tubes.

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