H.E. Dillon, A.F. Emery^†, A.M. Mescher, O. Sprenger, S.R. Edwards

Frontiers in Heat and Mass Transfer, Vol.2, No.2, pp. 1-14, 2011, DOI:10.5098/hmt.v2.2.3002

Abstract The stability of free convection in an annulus is governed by the boundary conditions on the inner and outer walls of the annulus and the upper and lower boundaries. This paper explores the effect of free convection on the inner surface of the annulus, where the boundary conditions for the outer wall and the upper and lower boundaries are controlled. The temperature is measured in the center of the air cavity and just below the surface of the inner annular boundary. Experimental results are shown for a radius ratio of 0.40, aspect ratio of 20.7. These more recent experimental results… More >

Ralph L. Webb

Frontiers in Heat and Mass Transfer, Vol.2, No.2, pp. 1-5, 2011, DOI:10.5098/hmt.v2.2.3001

Abstract This paper discusses the “Inlet Temperature Difference” (ITD) based heat-exchanger (and its variants) design methodology frequently used by designers of electronic heat sinks. The methodology is at variance with the accepted methodology recommended in standard heat-transfer text books – the “Log-Mean Temperature Difference” (LMTD), or the equivalent “effectiveness-NTU” design method. The purpose of this paper is to evaluate and discuss the ITD based design methodology and its deficiencies. The paper shows that the ITD based method is an approximation at best. Variants of the method can lead to either under or over prediction of the heat transfer rate. Its shortcomings… More >

Frontiers in Heat and Mass Transfer, Vol.2, No.2, pp. 1-1, 2011, DOI:10.5098/hmt.v2.2.1001

Abstract This article has no abstract. More >

Rajesh Kumar Panda, B.V.S.S.S. Prasad^*

Frontiers in Heat and Mass Transfer, Vol.2, No.1, pp. 1-10, 2011, DOI:10.5098/hmt.v2.1.3008

Abstract Conjugate heat transfer from a flat circular disk is investigated both computationally and experimentally with a constant heat flux imposed on its bottom surface and a shower head of air jets impinging on the top surface. The shower head consists of a central jet surrounded by four neighboring perimeter jets. Measured temperature data at twelve locations within the plate are compared with the conjugate heat transfer result obtained at the same locations computationally by Shear Stress Transport (SST) κ-ω turbulence model. The spacing to orifice diameter ratio (H/d = 1 to 4), the jet Reynolds number (7115 to 10674) and… More >

Oronzio Manca^*, Sergio Nardini, Daniele Ricci

Frontiers in Heat and Mass Transfer, Vol.2, No.1, pp. 1-8, 2011, DOI:10.5098/hmt.v2.1.3007

Abstract Convective heat transfer may be enhanced passively by adopting rough surfaces. Ribs break the laminar sub-layer and create local turbulence in the channel, reducing thermal resistance and enhancing the heat transfer. However, higher losses are expected. In this paper a numerical investigation is carried out on air forced convection in a rectangular ribbed channel. A three-dimensional model is developed to study the effect of the angle between the fluid flow direction and the ribbed surface, provided with rectangular turbulators, in the turbulent flow. Simulations s that Nusselt numbers as well as the pressure drops increase as the inclination angles increase. More >

Syeda Humaira Tasnim^a,*, Shohel Mahmud^b, Roydon Andrew Fraser^a

Frontiers in Heat and Mass Transfer, Vol.2, No.1, pp. 1-10, 2011, DOI:10.5098/hmt.v2.1.3006

Abstract In this paper, we experimentally measure the temperature fields at different locations on the stack plate and in the surrounding working fluid in a standing wave thermoacoustic device. The temperature measurements at the stack extremities and at the neighboring gas show axial heat transfer at the stack extremities, as opposed to the hypothesis of a perfectly isolated stack used in the linear thermoacoustic theory. Four different mechanisms of heat transfer are identified at the stack extremities in the present study. This information is necessary for the optimization of the performances of practical thermoacoustic engines. For the selected operating conditions, temperature… More >

Jing Huang, Kapil Baheti, J. K. Chen^*, Yuwen Zhang

Frontiers in Heat and Mass Transfer, Vol.2, No.1, pp. 1-10, 2011, DOI:10.5098/hmt.v2.1.3005

Abstract An axisymmetric model for thermal transport in thin metal films irradiated by an ultrashort laser pulse was developed. The superheating phenomena including preheating, melting, vaporization and re-solidification were modeled and analyzed. Together with the energy balance, nucleation dynamics was employed iteratively to track the solid-liquid interface and the gas kinetics law was used iteratively to track the liquid-vapor interface. The numerical results showed that higher laser fluence and shorter pulse width lead to higher interfacial temperature, larger melting and ablation depths. A simplified 1-D model could overestimate temperature response and ablation depth due to the omission of radial heat conduction. More >

Patrick H. Oosthuizen^*

Frontiers in Heat and Mass Transfer, Vol.2, No.1, pp. 1-8, 2011, DOI:10.5098/hmt.v2.1.3004

Abstract The convective heat transfer to a window below which is mounted a natural convective heater has been numerically studied. The flow has been assumed to be three-dimensional and steady and to involve regions of laminar and turbulent flow. Fluid properties have been assumed constant except for the density change with temperature which leads to the buoyancy forces. The solution has been obtained using a commercial cfd code. Results have been obtained for a Prandtl number of 0.7. The effects of changes in the flow variables on the window Nusselt number and on the flow and temperature distributions have been examined. 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 protrusions can be used advantageously… More >

Hai Trieu Phan^b, Nadia Caney^a,†, Philippe Marty^a, Stéphane Colasson^b, Jérôme Gavillet^b

Frontiers in Heat and Mass Transfer, Vol.2, No.1, pp. 1-6, 2011, DOI:10.5098/hmt.v2.1.3002

Abstract Experiments were performed to study the effects of surface wettability on flow boiling of water at atmospheric pressure. The test channel is a single rectangular channel 0.5 mm high, 5 mm wide and 180 mm long. The mass flux was set at 100 and 120 kg/m² s and the base heat flux was varied from 30 to 80 kW/m². Water enters the test channel under subcooled conditions. The sample surfaces are titanium (Ti) and diamond-like carbon (DLC) surfaces having a contact angle of 49° and 63°, respectively. The experimental results show different flow patterns that impact the heat transfer significantly.… More >