Numerical optimization on microchannel flow and heat transfer performance based on field synergy principle

Author(s):  
Fang Li ◽  
Wenhui Zhu ◽  
Hu He
2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Yang Liu ◽  
Jing Cui ◽  
WeiZhong Li ◽  
Ning Zhang

In this paper, forced convection heat transfer occurring in microchannels with different microstructures is investigated numerically. It is found that vortices will appear in the microstructure grooves. The influence of microchannel geometries on heat transfer performance is evaluated by Nusselt number and the entrance effect is noted for all geometries. Compared with the plain plate surface, a much more moderate decrease of local Nusselt number can be found for all the grooved microstructures, indicating more uniform heat transfer intensity along the flowing direction. The results also suggest that the heat transfer performance improves with inlet Reynolds number. The V-shaped grooved microstructure possesses the highest heat transfer performance. Compared with the plain plate surface, averaged Nusselt number can be increased by about 1.6 times. Through the field synergy principle analysis, we find that it is the synergy between temperature gradient and velocity that results in different heat transfer performance for different microstructures.


2012 ◽  
Vol 516-517 ◽  
pp. 949-953
Author(s):  
Jiu Yang Yu ◽  
Li Jun Liu ◽  
Wei Lin ◽  
Qian Liu ◽  
Wen Hao Yang ◽  
...  

The present paper focuses on the analysis of transient heat transfer and flow in a vibratory tube. The characteristics of flow and heat transfer are investigated by dynamic mesh of CFD (computational fluid dynamics) software FLUENT, the velocity and temperature distributions in a vibration cycle are analyzed by field synergy theory. The results indicate that the vibration parameters have great effect on heat transfer, and the tube vibration leads to heat transfer enhancement or reduction. Moreover, the optimum heat transfer performance inside tubes is obtained in a half-cycle when time phase is 90°.


Author(s):  
X. Yu ◽  
C. Woodcock ◽  
Y. Wang ◽  
J. Plawsky ◽  
Y. Peles

In this paper we reported an advanced structure, the Piranha Pin Fin (PPF), for microchannel flow boiling. Fluid flow and heat transfer performance were evaluated in detail with HFE7000 as working fluid. Surface temperature, pressure drop, heat transfer coefficient and critical heat flux (CHF) were experimentally obtained and discussed. Furthermore, microchannels with different PPF geometrical configurations were investigated. At the same time, tests for different flow conditions were conducted and analyzed. It turned out that microchannel with PPF can realize high-heat flux dissipation with reasonable pressure drop. Both flow conditions and PPF configuration played important roles for both fluid flow and heat transfer performance. This study provided useful reference for further PPF design in microchannel for flow boiling.


2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Ningbo Zhao ◽  
Xueyou Wen ◽  
Shuying Li

Coolant is one of the important factors affecting the overall performance of the intercooler for the intercooled (IC) cycle marine gas turbine. Conventional coolants, such as water and ethylene glycol, have lower thermal conductivity which can hinder the development of highly effective compact intercooler. Nanofluids that consist of nanoparticles and base fluids have superior properties like extensively higher thermal conductivity and heat transfer performance compared to those of base fluids. This paper focuses on the application of two different water-based nanofluids containing aluminum oxide (Al2O3) and copper (Cu) nanoparticles in IC cycle marine gas turbine intercooler. The effectiveness-number of transfer unit method is used to evaluate the flow and heat transfer performance of intercooler, and the thermophysical properties of nanofluids are obtained from literature. Then, the effects of some important parameters, such as nanoparticle volume concentration, coolant Reynolds number, coolant inlet temperature, and gas side operating parameters on the flow and heat transfer performance of intercooler, are discussed in detail. The results demonstrate that nanofluids have excellent heat transfer performance and need lower pumping power in comparison with base fluids under different gas turbine operating conditions. Under the same heat transfer, Cu–water nanofluids can reduce more pumping power than Al2O3–water nanofluids. It is also concluded that the overall performance of intercooler can be enhanced when increasing the nanoparticle volume concentration and coolant Reynolds number and decreasing the coolant inlet temperature.


Author(s):  
F. Sun ◽  
H. Li ◽  
J. Drummond ◽  
G.-X. Wang

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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