Analysis Of Forced Convection Heat Transfer Research Articles

Heat Transfer in a Short Parallel-Plate Channel in the Transition Regime

Heat transfer in a parallel-plate channel with uniform wall heat flux and refrigerated by water is investigated experimentally for the laminar and transition hydrodynamic regimes. The dimensions of the channel were chosen such that entry effects are relevant for a significant part of the channel length. The influence of the following parameters has been studied: inlet Reynolds number, inlet temperature and wall heat flux. Experimental results are compared with predictions based on different empirical correlations for convection in ducts. This analysis shows that the correlation of Gnielinski provides a good agreement with the experimental results for Reynolds numbers between 5,000 and 10,000 at 20°C and under relatively low heat fluxes. Experiments performed at relatively low heat fluxes show that, in the entry region previous to the laminar-turbulent transition, the behavior of the flow is well described by the combined hydrodynamic and thermal entry solution obtained by Hwang and Fan (Finite Difference Analysis of Forced-Convection Heat Transfer in Inlet Region of a Flat Rectangular Duct, Appl. Sci. Res., vol. 13, pp. 401–422, 1964). The hydrodynamic and thermal entry effects for the experimental conditions in the present work are relevant for most of the test section. The location of the transition point is affected in the first instance by the local bulk Reynolds. On the other hand, the wall heat flux affects the fluid properties, i.e., the fluid viscosity, and therefore, it also affects the transition. It was found that for the transition regime, an increase of the wall heat flux produces lower values of the convection coefficient than the values predicted by the correlation of Gnielinski. This behavior, which seems to be associated to the variation of the fluid properties, is opposite to the increase of the convection coefficient observed for heating in the laminar and turbulent regimes for water and oils. The case of an inlet Reynolds number of 5,000 was studied in detail, and the influence of heat flux on the Nusselt number is addressed.

302 Joule-Thomson効果を考慮した充填層内強制対流熱伝達の理論的研究(OS3-1,OS3 多孔質体内流動・伝熱・燃焼研究の新展開)

302 Joule-Thomson効果を考慮した充填層内強制対流熱伝達の理論的研究(OS3-1,OS3 多孔質体内流動・伝熱・燃焼研究の新展開)

Joule-Thomson効果を考慮した充填層内強制対流熱伝達の解析(一般セッション 伝熱解析及び理論 II)

Joule-Thomson効果を考慮した充填層内強制対流熱伝達の解析(一般セッション 伝熱解析及び理論 II)

Steady-State Numerical Solution of the Navier-Stokes and Energy Equations around a Horizontal Cylinder at Moderate Reynolds Numbers from 100 to 500

A numerical analysis of forced-convection heat transfer from a horizontal stationary circular cylinder dissipating a uniform heat flux in a crossflow of air is conducted by solving the full two-dimensional steady-state Navier-Stokes and energy equations in the range of the Reynolds numbers from 100 to 500 (based on diameter). A numerical study by this author for Reynolds numbers less than 100 was previously conducted and therefore is not repeated here. Dependence on the Reynolds number of the flow and thermal fields, vorticity and pressure distributions, separation angle, drag coefficient, and local and average Nusselt number around the cylinder are shown. Correlations for the separation angle and drag coefficient as functions of Reynolds number are suggested. Quantities such as vorticity, pressure, and Nusselt number at the forward and rear (base) stagnation points are also calculated and correlated as functions of Reynolds number. The local and average values of the Nusselt numbers are shown to be in go...

The effect of variable viscosity on boundary-layer heat transfer in a porous medium

In this work we present a theoretical analysis of forced-convection heat transfer over a flat surface imbedded in a saturated porous medium, considering that the viscosity of the fluid varies with temperature. The velocity and temperature profiles are described by means of a similarity solution. The effect of viscosity variations is quantified for the case of a fluid whose dependence of viscosity on temperature is linear. Illustrative results indicate that, for liquids, this effect should be taken into account, even for relatively low temperature gradients. This confirms experimental observations made in previous works.

MOVING FREE SURFACE HEAT TRANSFER ANALYSIS BY CONTINUOUSLY DEFORMING FINITE ELEMENTS

A two-dimensional transient analysis of forced-convection heat transfer is presented for a heated liquid with a free surface advancing into an initially empty channel of finite length at a lower temperature. The problem formulation is neither purely Eulerian nor purely Lagrangian. In particular, conservation equations for a control volume that deforms at a known rate are derived. These equations are used to derive a finite-element formulation that encompasses continuous mesh deformation automatically and consistently, and numerical results of its solution are presented.

Finite difference analysis of forced-convection heat transfer in entrance region of a flat rectangular duct

The laminar forced convection heat transfer in the entrance region of a flat rectangular duct is studied. In this region temperature and velocity profiles are simultaneously developed. The basic governing equations of momentum, continuity, and energy are expressed in finite difference form and solved numerically by use of a high speed computer for a mesh network superimposed on the flow field. All fluid properties are assumed to be constant. The cases of uniform constant wall temperature and of uniform constant heat flux from wall to fluid are considered. Nusselt numbers are reported for Prandtl numbers in the range of 0.01 to 50. The exact solution of the energy equation obtained by means of the numerical method is compared with the results of approximate solutions.