Heat transfer characteristics of magnetohydrodynamic electroosmotic flow in a rectangular microchannel

2019 ◽  
Vol 74 ◽  
pp. 180-190 ◽  
Author(s):  
Chunhong Yang ◽  
Yongjun Jian ◽  
Zhiyong Xie ◽  
Fengqin Li
2015 ◽  
Vol 813-814 ◽  
pp. 782-786
Author(s):  
C. Anbumeenakshi ◽  
M.R. Thansekhar ◽  
M. Satheeshkumar ◽  
R. Vishnu Gayathri

The microchannel cooling technique appears to be a viable solution to high heat rejection requirements of today’s high-power electronic devices. The thermal design of the small electronics cooling devices is a key issue that needs to be optimized in order to keep the system temperatures at certain levels. Thus the need of microchannel became vital. This present work investigates the experimental work conducted in a coated rectangular microchannel heat sink of hydraulic diameter of 0.763 mm for a heat input of 250 to 1020 Watt with water to study the heat transfer characteristics with two types of header arrangement such as rectangular header and trapezoidal header. The header plays a significant role in distributing the water in to the channels. The uniform distribution of water leads to uniform heat transfer in microchannels. From the experimental results carried with two types of header arrangements, it was found that coated rectangular microchannel with trapezoidal header gives better heat transfer characteristics for the range of heat inputs.


Micromachines ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 421
Author(s):  
Shuyan Deng ◽  
Quan An ◽  
Mingying Li

The non-Newtonian nanofluid flow becomes increasingly important in enhancing the thermal management efficiency of microscale devices and in promoting the exploration of the thermal-electric energy conversion process. The effect of streaming potential and viscous dissipation in the heat transfer characteristics of power-law nanofluid electrokinetic flow in a rectangular microchannel has been investigated to assist in the development of an energy harvesting system. The electroviscous effect caused by the streaming potential influences the hydrodynamical and thermal characteristics of flow. With the change in constitutive behavior of power-law nanofluid, the viscous dissipation effect is considered. The Poisson–Boltzmann equation, the modified Cauchy momentum equation, and the energy equation were solved. The temperature and heat transfer rate were analytically expressed for Newtonian nanofluid and numerically obtained for power-law nanofluid. The interactive influence of streaming potential, viscous dissipation, and hydrodynamical features of power-law nanofluid on the heat transfer characteristics were studied. The presence of streaming potential tends to reduce the dimensionless bulk mean temperature. The introduction of nanoparticles augments dimensionless temperature difference between channel wall and bulk flow, which decreases the heat transfer rate. The shear thinning nanofluid is more sensitive to the above effects. The temperature is a weak function of the flow behavior index.


Author(s):  
M. Yakut Ali ◽  
Fanghao Yang ◽  
Ruixian Fang ◽  
Chen Li ◽  
Jamil Khan

This study experimentally assesses single phase heat transfer characteristics of a shallow rectangular microchannel heat sink whose surface is enhanced with copper nanowires (CuNWs). The hydraulic diameter of the channel is 672 μm and the bottom wall is coated with Cu nanowires (CuNWs) of 200 nm in diameter and 50 μm in length. CuNWs are grown on the Cu heat sink by electrochemical synthesis technique which is inexpensive and readily scalable. The heat transfer and pressure drop results of CuNWs enhanced heat sink are compared with that of bare copper heat sink using deionized (DI) water as the working fluid at Reynolds Number (Re) ranging from 106–636. The experimental results indicate an enhancement in Nusselt Number (Nu) at all Re with a maximum enhancement of 24% at Re = 106. The enhanced thermal performance is attributed to two properties of Cu nanowire arrays — improvement in surface wettability characteristics and increased heat transfer surface area.


2005 ◽  
Author(s):  
Keisuke Horiuchi ◽  
Prashanta Dutta

Analytical solution for the heat transfer characteristics of steady electroosmotic flows with an arbitrary pressure gradient are obtained for two-dimensional straight micro-channels. Both thermally developing and fully developed regions are considered for hydraulically fully developed mixed flows under isoflux channel wall conditions. In mixed flow cases, the governing equation for energy is not separable in general. Therefore, we introduced a new method that considers the extended Graetz problem. Heat transfer characteristics are presented for low Reynolds number micro-flows where the viscous and electric field terms are very dominant. Our analytical techniques are verifled by obtaining an excellent agreement with existing literature for slug, pressure driven, and pure electroosmotic flow cases. In the fully developed region, the Nusselt number of mixed flow is independent of the thermal Peclet number for a particular Joule heat and imposed surface heat flux. The entry length of mixed flow significantly depends on the applied pressure gradient to the electroosmotic flow.


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