A numerical solution of the unsteady radiative free convection flow of an incompressible viscous fluid past an impulsively started vertical plate with variable heat and mass flux is presented here. This type of problem finds application in many technological and engineering fields such as rocket propulsion systems, spacecraft re-entry aerothermodynamics, cosmical flight aerodynamics, plasma physics, glass production and furnace engineering. The fluid is gray, absorbing-emitting but non-scattering medium and the Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing non-linear, coupled equations are solved using an implicit finite difference scheme. Numerical results for the velocity, temperature, concentration, the local and average skinfriction, the Nusselt and Sherwood number are shown graphically, for different values of Prandtl number, Schmidt number, thermal Grashof number, mass Grashof number, radiation parameter, heat flux exponent and the mass flux exponent. It is observed that, when the radiation parameter increases, the velocity and temperature decrease in the boundary layer. The local and average skin-friction increases with the increase in radiation parameter. For increasing values of radiation parameter the local as well as average Nusselt number increases.

Heat transfer by electromagnetic radiation is one of the common methods of energy transfer between objects. Using the fluctuation-dissipation theorem, we have studied the effect of particle arrangement in the transmission of radiative heat in many-body systems. In order to show the effect of the structure morphology on the collective properties, the radiative heat transfer is studied and the results are compared for fractal and periodic structures. The calculations for fractals are restricted to the fractal structures based on vicsek model. It is shown that the thermal conductance can be large even for far apart particles in periodic structures. In contrast, it is shown that fractal arranged nanoparticles display complex radiative behavior related to their scaling properties, and heat flux is not of large-range character in such structures.

Radiative heat transfer must be considered in retail refrigerators with glass doors. Some methods have been proposed for reducing radiative losses, like usage of double glased windows filled with argon or other types of transparent material with low emissivity in infrared band. For evaluation of thermal radiation in commercial refrigerator compared to infiltration loss, thermal conduction and facilities loss, a three dimensional model has been developed. In this model all wall surfaces are isothermal and evaporator with specific temperature located in roof. The radiative properties of glass are considered as actual.The results show that decreasing internal temperature of cabinet incentive radiation losses. These losses are almost independent of window surface temperature. Increasing of emissivity factor of evaporator, causes increasing of thermal radiation flux of evaporator which can be used in design improvement. Radiation flux of each surface have been compared with convection flux. This comparison show the importance of covering windows in unutilized times.

In this paper, an inverse heat conduction problem in one-dimensional infinite domain will be considered. By employing inverse heat fundamental solution, and an over specified condition, the temperature and its heat flux will be identified.

An industrial furnace could be considered as a three dimensional enclosure. The zonal analysis of radiative heat transfer modeling is used for finding the three dimensional temperature distributions. Exchange areas are determined by simplified numerical integration in three dimensions for surface-surface, surface-gas, and gasgaszones for absorbing and emitting media. The effects of some important parameters in the furnaces are described. It is shown that the zonal method is a useful numerical method for considering multi-dimensional thermal performance of gas-filled enclosures.

A helical double-pipe heat exchanger filled with a porous material under asymmetric heat flux is studied analytically. Momentum and energy equations are transformed to the Germano? s coordinate and then expressions representing the velocity and temperature fields are obtained based on the powers of dimensionless curvature using perturbation analysis. To be more insightful، contours of velocity and temperature fields are presented. Results reveal an asymmetric axial velocity profile arising from the curved geometry. The Nusselt number increases with respect to the dimensionless curvature increment as well as the inner to outer radius ratio increase.

In the present study an unsteady mixed convection boundary layer flow of an electrically conduct-ing fluid over an stretching permeable sheet in the presence of transverse magnetic field, thermal radiation and non-uniform heat source/sink effects is investigated. The unsteadiness in the flow and temperature fields is due to the time-dependent nature of the stretching velocity and the surface temperature. Both opposing and assisting flows are considered. The dimensionless governing or-dinary non-linear differential equations are solved numerically by applying shooting method using Runge-Kutta-Fehlberg method. The effects of unsteadiness parameter, buoyancy parameter, thermal radiation, Eckert number, Prandtl number and non-uniform heat source/sink parameter on the flow and heat transfer characteristics are thoroughly examined. Comparisons of the present results with previously published results for the steady case are found to be excellent.