Chekifi. T^1,2, Dennai. B¹, Khelfaoui. R¹

FDMP-Fluid Dynamics & Materials Processing, Vol.11, No.3, pp. 205-220, 2015, DOI:10.3970/fdmp.2015.011.205

Abstract Droplet generation, splitting and sorting are investigated numerically in the framework of a VOF technique for interface tracking and a finite-volume numerical method using the commercial code FLUENT. Droplets of water-in-oil are produced by a flow focusing technique relying on the use of a microchannell equipped with an obstacle to split the droplets. The influence of several parameters potentially affecting this process is investigated parametrically towards the end of identifying "optimal" conditions for droplet breakup. Such parameters include surface tension, the capillary number and the main channel width. We show that the capillary number plays More >

P. K. Das^*, S. Chakraborty, S. Bhaduri

Frontiers in Heat and Mass Transfer, Vol.3, No.1, pp. 1-17, 2012, DOI:10.5098/hmt.v3.1.3008

Abstract A state of the art review of critical heat flux during flow boiling through mini and microchannels has been provided based on the open literature. This review mainly examines three aspects, namely the experimental investigations, the available correlations and the state of prediction using those correlations and finally the proposed physical mechanisms as well as the theoretical models. Before discussing the specific literature on microchannels, a brief overview of critical heat flux for pool and flow boiling is provided. The review has been concluded with a summary of the available information on this topic and More >

Amit Agrawal^a,*, V.S. Duryodhan^a, S. G. Singh^b

Frontiers in Heat and Mass Transfer, Vol.3, No.1, pp. 1-7, 2012, DOI:10.5098/hmt.v3.1.3005

Abstract An experimental study of flow boiling through diverging microchannels has been carried out in this work, with the aim of exploring reduction in flow instabilities during boiling in diverging microchannels. Effect of mass flux, heat flux and divergence angle on two phase pressure drop has been studied using deionized water as the working fluid. The experiments are carried out on three test sections with divergence angle of 4, 8 and 12 deg with nearly constant hydraulic diameter (146, 154 and 157 µm respectively), for inlet mass flux and heat flux range of 117 - 1197 kg/m² More >

Jiwon Yu^a , Seok-Won Kang^a, Saeil Jeon^b, Debjyoti Banerjee^a,*

Frontiers in Heat and Mass Transfer, Vol.3, No.1, pp. 1-9, 2012, DOI:10.5098/hmt.v3.1.3004

Abstract Experiments were performed to study the forced convective heat transfer of de-ionized water (DI water) and aqueous nanofluids in a microchannel and temperature measurements were obtained using an array of nanosensors (i.e., thin film thermocouples or “TFT”). Heat flux values were calculated from the experimental measurements for temperature recorded by the TFT array. The experiments were performed for the different test fluids where the flow rate, mass concentration (of silica nanoparticles ~10-30 nm diameter) in the colloidal suspension and the wall temperature profile (as well as applied heat flux values) were varied parametrically.
Anomalous enhancement… More >

Yaohua Zhang^a,*, Yoshio Utaka^b

Frontiers in Heat and Mass Transfer, Vol.3, No.1, pp. 1-12, 2012, DOI:10.5098/hmt.v3.1.3003

Abstract This paper reviews recent research on microlayer formed by confined vapor bubbles during boiling in mini/microchannels. Experimental measurements, simulations and theoretical studies are described and compared. As a reference to clarify the mechanism for the formation of a microlayer, Taylor flow (i.e. elongated bubble flow in mini/micro circular tubes under adiabatic conditions and at Re << 1) and elongated bubble flow at high velocity, with consideration of the influence of inertia, are also reviewed. Compared to the steady adiabatic conditions, one of the distinct points for the boiling condition is that the bubble grows exponentially More >

Etienne Costa-Patry^a, Jonathan Olivier^b, John R. Thome^a,∗

Frontiers in Heat and Mass Transfer, Vol.3, No.1, pp. 1-14, 2012, DOI:10.5098/hmt.v3.1.3002

Abstract This article presents new experimental results for two-phase flow boiling of R-134a, R-1234ze(E) and R-245fa in a micro-evaporator. The test section was made of copper and composed of 52 microchannels 163μm wide and 1560μm high with the channels separated by 178μm wide fins. The channels were 13.2mm long. There were 35 local heaters and temperature measurements arranged in a 5×7 array as a pseudo-CPU. The total pressure drops of the test section were below 20kPa in all cases. The wall heat transfer coefficients were generally above 10’000W/m²K and a function of the heat flux, vapor quality More >

Tomio Okawa^*,†

Frontiers in Heat and Mass Transfer, Vol.3, No.1, pp. 1-8, 2012, DOI:10.5098/hmt.v3.1.3001

Abstract The present article summarizes the studies on the thermalhydraulic condition under which the onset of nucleate boiling (ONB) is triggered in subcooled flow boiling. Available correlations and experimental data show that the ONB is tended to be delayed in mini and microchannels. It is known that the ONB condition is significantly dependent on the surface condition even in conventional-sized channels. Accumulation of ONB data accompanied by the information on the surface condition is therefore considered of importance to elucidate the mechanisms of boiling incipience in microchannels. Discussion is also made for the bubble dynamics observed More >

Frontiers in Heat and Mass Transfer, Vol.3, No.1, pp. 1-3, 2012, DOI:10.5098/hmt.v3.1.1001

Abstract This article has no abstract. More >

M. Yakut Ali^a,*, Fanghao Yang^a, Ruixian Fang^a, Chen Li^a, Jamil Khan^a,†

Frontiers in Heat and Mass Transfer, Vol.2, No.3, pp. 1-11, 2011, DOI:10.5098/hmt.v2.3.3003

Abstract This study experimentally investigates single phase heat transfer and pressure drop 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 surface heat… More >

Muhammad M. Rahman^*, Phaninder Injeti

Frontiers in Heat and Mass Transfer, Vol.2, No.1, pp. 1-9, 2011, DOI:10.5098/hmt.v2.1.3003

Abstract This paper presents the effects of protrusions on heat transfer in a microtube and in a two-dimensional microchannel of finite wall thickness. The effects of protrusion shape, size, and number were investigated. Calculations were done for incompressible flow of a Newtonian fluid with developing momentum and thermal boundary layers under uniform and discrete heating conditions. It was found that the local Nusselt number near a protrusion changes significantly with the variations of Reynolds number, height, width, and distance between protrusions, and the distribution of discrete heat sources. The results presented in the paper demonstrate that More >