Effect of baffle on convective heat transfer from a heat generating element in a ventilated cavity

This paper reports the results of a numerical and experimental investigation of mixed convection from a heat-generating element in a vented cavity with/without a baffle arrangement. Numerical investigations are carried out to determine the best position of the baffle on the walls of a rectangular chamber. The effect of varying the baffle heights and the position on the enhancement of heat transfer from the heater is investigated. Experiments were carried out for a heater located centrally in a parallelepiped that has an air inlet and an outlet port. The vertical baffle is fixed on the bottom wall of the chamber. After a detailed parametric study, correlations have been developed for the average Nusselt number and the maximum dimensionless temperature occurring in the heat generating element. Comparison of the numerical and experimental results for the geometry considered showed good agreement.     

A correlation for laminar mixed convection from vertical plates using transient experiments

The applicability of the transient cooling experimental technique is studied for developing a correlation for Nusselt number with other pertinent parameters for laminar aiding mixed convection flows over an isothermal vertical plate. A heated aluminum plate, modeled as a lumped system, is allowed to cool in the mixed convection environment during which the transient response of the plate is recorded using a data acquisition system. The experimentally known transient response of the plate is then compared with the numerically computed transient response to estimate the square of the residual. The minimization of this residual using Levenberg–Marquardt iterative procedure retrieves the values of relevant parameters in the correlation, whose form is assumed a priori. The experiments were conducted for a temperature range of 410–305 K and a corresponding Richardson number range 20–0.04. The retrieved values of the parameters compare well with those available in literature.     

Approximate solution of nonlinear transient heat conduction in one dimension

Three approximate methods, viz. the Heat Balance Integral method (HBI), the Modified Heat Balance Integral method (MHBI) and the Double Integral Method (DIM) in combination with hybrid profiles (HP - consisting of an exponential and polynomial) are evaluated for relative merits in solving the onedimensional heat diffusion equation. Applications to two linear test problems (TP1 - semi-infinite solid with constant heat flux at its boundary, TP 2 - semi-infinite solid with step change in its surface temperature) yield the HP-MHBI as the most desirable combination. Applications to nonlinear problems show that these combinations are ideally suited for obtaing reliable and accurate appoximate solutions.

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Näherungslösung von eindimensionaler nicht linearer transienter Wärmeleitung

Zusammenfassung Es wurden drei Näherungsmethoden, die Heat Balance Integral-Methode (HBI), die Modified Heat Balance IntegralMethode (MHBI) und die Double Integral-Methode (DIM) in Verbindung mit hybriden Profilen (HP - bestehend aus Exponentialund Polynomfunktionen) ausgewählt, um die eindimensionale Wärmediffusionsgleichung zu lösen. Anwendungen auf zwei lineare Testprobleme (TP 1 - halb-unendlicher Festkörper mit konstantem Wärmestrom an dessen Grenze, TP2 - halb-unendlicher Festkörper mit sprunghaftem Wechsel der Oberflächentemperatur) ergaben, daß die HP-MHBI-Methode die erwünschte Kombination darstellt. Anwendungen auf nichtlineare Probleme zeigen, daß diese Kombination ideal für das Erzielen zuverlässiger und aussagekräftiger Näherungslösungen ist.

     

Plasma waves in a stochastic magnetic field

Propagation of circularly polarized waves along a spatially uniform but temporally fluctuating magnetic field is considered. It is shown that the coherent waves are damped. The results are compared with those for Krook's relaxation model.     

Survivable network design with shared-protection routing

In this paper we study the problem of designing a survivable telecommunication network with shared-protection routing. We develop a heuristic algorithm to solve this problem. Recent results in the area of global re-routing have been used to obtain very tight lower bounds for the problem. Our results indicate that in a majority of problem instances, the average gap between the heuristic solutions and the lower bounds is within 5%. Computational experience is reported on randomly generated problem instances with up to 35 nodes, 80 edges and 595 demand pairs and also on the instances available in SNDlib database.     

Construction of two dimensional temperature field from first derivative fields

Schlieren and its variants such as differential interferometry and schlieren microscopy, have been used extensively for flow visualization where first derivative fields are captured. The derivative fields obtained from the schlieren like methods can be further processed to estimate the temperature field when the first derivative fields relate to those of temperature. Temperature construction from first derivative field is an ill-posed problem owing to the experimental noise and a few discrete points where measured temperatures may be available. A new approach has been proposed where the domain is discretized into a large number of triangular elements and least-squares based finite-element analysis is performed over the discretized domain. The domain and boundaries are identified manually based on prior knowledge. Temperature fields have been constructed for experimentally obtained first derivative fields from a Differential Interferometer (DI) for different cases. The performance of the new methodology is found to be good.