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Abstract: Axially rotating heat pipes are devices used to dissipate heat flux through the latent heat of phase change of a fluid at saturation state. In these systems, centrifugal forces due to heat pipe rotation allow the liquid to flow. The present study focuses on cylindrical heat pipes due to the simplicity and cost of the manufacturing of theses devices. This paper presents a steady-state model of heat and mass transfers along the rotating heat pipe. An optimization procedure, which permits to work at a given saturation temperature and so allows to study the parameters influence for given thermophysical properties, has been developed to perform the calculations. The hypotheses of the model are also discussed and examined. Finally, a parametric study has been carried out, using water as a working fluid, to highlight the influence of parameters such as rotational speed, temperature difference between the evaporator wall and the vapour, or the mass of fluid, on the heat transfers. Finally, the operating conditions conducive to maximal performance have been described. [Copyright &y& Elsevier]

Abstract: In this paper we investigate the magnetohydrodynamic slip flow of an electrically conducting, viscoelastic fluid past a stretching surface. The main concern is to analytically investigate the structure of the solutions and determine the thresholds beyond which multiple solutions exist or the physical pure exponential type solution ceases to exist. In the case of the presence of multiple solutions, closed-form formulae for the boundary layer equations of the flow are presented for two classes of viscoelastic fluid, namely, the second-grade and Walter’s liquid B fluids. Heat transfer analysis is also carried out for two general types of boundary heating processes, either by a prescribed quadratic power-law surface temperature or by a prescribed quadratic power-law surface heat flux. The flow field is affected by the presence of physical parameters, such as slip, viscoelasticity, magnetic and suction/injection parameters, whereas the temperature field is additionally affected by thermal radiation, heat source/sink, Prandtl and Eckert numbers. The regions of existence or non-existence of unique/multiple solutions sketched by the combination of these parameters are initially worked out by providing critical values and then velocity/temperature profiles and skin friction coefficient/Nusselt number are examined and discussed. [Copyright &y& Elsevier]

Abstract: An analysis was carried out to study the performance of spine fins of different configurations when subjected to simultaneous heat and mass transfer mechanisms. The temperature and humidity ratio differences are the driving forces for the heat and mass transfer, respectively. Analytical solutions are obtained for the efficiency and temperature distribution over the spine surface when the surface condition is fully wet. A correction chart is developed to correct the value of the dry fin parameter if the fin surface condition is fully wet. The effect of atmospheric pressure on the spine efficiency was also studied as well as the spine optimum geometries were obtained such that a maximum amount of heat transfer rate occurs. It is shown that the closed-form solution for a dry spine case discussed in text books is a special case for the solutions presented in this paper. [Copyright &y& Elsevier]