Conjugate Convective Heat Transfer Research Articles

Numerical solutions of conjugate heat transfer and thermal stresses in a circular pipe externally heated with non-uniform heat flux

Conjugate heat transfer by forced convection through an externally heated pipe has many important engineering applications. In the present work, the radial and axial heat conductions and thermal stresses in a pipe with uniform or non-uniform wall heat flux of fully developed laminar forced convective conjugate heat transfer have been considered for analysis. The analysis is based on the two-dimensional steady-state heat conduction equation and laminar boundary layer equation for the flowing fluid by using a finite difference scheme. Water has been used as a fluid. Numerical calculations have been performed by using the FLUENT 4.5 and HEATING7 computer codes. The temperature and stress ratio distributions inside the pipe wall, heated from the outer surface by applying uniform and non-uniform heat fluxes, have been presented for two different mean flow velocities. The temperature distributions of the flowing fluid inside the pipe have also been presented for all investigated cases.

NATURAL CONVECTION BETWEEN PARALLEL PLATES WITH CONJUGATE CONDUCTIVE EFFECTS

This article deals with the conjugate conductive and convective heat transfer in a vertical channel with finite thickness conductive parallel plates. The investigation is carried out numerically by solving the full elliptic Navier-Stokes and energy equations with the finite volume method in a composite I-shaped domain. The results are reported as functions of the main geometrical (B/b and L/b) and thermal (K and Ra*) parameters, for a Prandtl number of 0.71 (i.e., air). The results show that the thinner the plate the more uniform the heat flux distribution along the plate. As the thickness of the plate increases, the heat flux distribution is less uniform and at the inlet corner the temperatures present much higher values than at the infinitely thin plate. Lower plate thermal conductivity implies a more uniform heat flux distribution and lower temperature increments than the infinitely thin plate. The dependence of the heat flux and temperature distributions along the solid-fluid interface is stronger than the lower the Ra* value.

Laminar forced convection conjugate heat transfer over a flat plate

Coupled heat transfer between laminar forced convection along and conduction inside a flat plate wall is theoretically studied. The laminar convective boundary layer is analyzed by employing the integral technique. The energy equations for the fluid and the plate wall are combined under the condition of the continuity in the temperature and heat flux at the fluid-solid interface. The analysis results in a simple formal solution. Expressions have been obtained for calculating local Nusselt number, wall heat flux and temperature along the plate, all are functions of the local Brun number, Br x , which is a measure of the ratio of the thermal resistance of the plate to that of the convective boundary layer. The results indicate that for Br x ≥0.15, neglecting the plate resistance will results in an error of more than 5% in Nusselt number. Comparison of the present solution with other previous studies has been made. The solution may be of a considerable theoretical and practical interest.

The thermal-hydraulic characteristics of staggered circular finned-tube heat exchangers under dry and dehumidifying conditions

Fluid flow and heat transfer over four row circular finned-tube heat exchangers with staggered arrangement are studied experimentally and numerically. Two types of finned-tube configurations have been investigated under the dry and wet conditions for different values of inlet frontal velocity ranging from 1 to 6 m s −1. The experimental results indicated that the sensible Colburn factor, J s , and for the friction factor, φ, the wet coils are, respectively 20% and 15% higher than that for the dry coils. The three-dimensional numerical results of laminar model for the dry coils are also presented. Conjugate convective heat transfer in the flow field and heat conduction in the circular fins are considered also. The numerical results for the streamline, isotherm, Nusselt number and fin efficiency are shown and compared with the experiments.

Mixed Convective Conjugate Heat Transfer from a Vertical Flat Plate

AbstractThe aim of this paper is to present a detailed numericla study of the conjugate mixed convection flow along a vertical finite flat plate and both the cases of aiding and opposing flows, which are characterized by the buoyancy parameter λ, are considered. In the first part of the analysis, asymptotic series solutions which are valid near the leading edge of the plate and far from it are given. These solutions are them matched by solving numerically the full governing boundary‐layer equations using a finite‐difference scheme. It is shown that for λ < 0 (opposing flow) the boundary‐layer separates from the plate and we have determined very accurately the location of the point of separation, i.e. where the numerical method breaks down. In addition, an asymptotic expression is given which accurately predicts the position of separation as a function of the buoyancy parameter. Detailed velocity and temperature profiles, and the skin friction and the temperature at the plate are given for a wide range of values of the relevant parameters which occur in the problem.

Transient conjugate heat transfer between a laminar stagnation zone and a solid disk

An explicit finite difference technique is used to solve the case of transient, forced convective conjugate heat transfer between an axisymmetric incompressible laminar impinging jet and a solid disk. The solution to the governing equations is based on the assumptions of constant physical properties and no viscous dissipation. The hydrodynamics of the flow are considered to be steady state, whereas thermal transients take place with a step temperature change at the jet upstream boundary condition. The unexposed bottom surface of the disk is treated as an isothermal boundary, and the radial boundary of the disk is modeled as adiabatic. In this work, the effect of the ratios of thermal conductivity and thermal diffusivity between fluid and solid on transient heat transfer characteristics of the system have been investigated.

Temperature field of the active element of a solid-state laser with a liquid cooling system

Results of a numerical solution of a nonstationary conjugate convective heattransfer problem are presented. Temperature fields are determined in the coolant stream and in the body being cooled.

Conjugate convective heat transfer problems

From the analysis of a conjugate problem of convective heat transfer in a laminar incompressible flow around a flat plate of a finite thickness the design formulas are suggested for a local Nusselt number Nu x ( Nu x / Nu x0 )−1 = CB x , (0 < Br x < 1.5), ( Nu x / Nu x0 )−1 = C 0−( C/ Br x ), (1.5 < Br x <∞), where Nu x0 is the Nusselt number with Br x = 0 (the Nusselt number defined by the ordinary heat transfer equations) and Br x is the localBrun number (a conjugation number).