S. Faggiani

Influence of Streamwise Molecular Heat Conduction on the Heat Transfer Coefficient for Liquid Metals in Turbulent Flow between Parallel Plates

The energy equation for mechanically fully developed turbulent flow between parallel plates is numerically solved taking into account the term of streamwise heat conduction. Solutions are presented for Re = 7060 and 73620, and for Pr ranging from 0.001 to 0.1. Generally the influence of the streamwise molecular conduction results in a remarkable decrease of the Nusselt number in the thermal inlet. . Copyright

Forced and mixed convection heat transfer from an array of cylinders to a liquid submerged jet

Abstract The results of an experimental investigation concerning the heat transfer from three cylindrical heaters to a water jet are reported in the form of correlating equations, which express the Nusselt number versus the Reynolds, Prandtl and Grashof numbers and some dimensionless ratios characterising the configuration. As the experienced range of the thermal flux is wide (2·104 ≤ q ≤ 6·105 W·m−2), the influence of the free convection, which was shown to be negligible in previous studies, is carefully investigated in the present one. This influence appears still negligible up to the maximum value of q for the heater impinged by the jet; on the contrary it is remarkable for the heaters lying in its wake. Another aspect which is carefully studied is the influence both of the ratios characterising the configuration and of the impingement direction: accordingly the values of these ratios and the kind of impingement which yield the maximum Nusselt number are clearly singled out. The investigation is completed by some visualization experiments which allow us to qualitatively clarify some aspects of the interaction between the dynamic and thermal fields.

Thermal Behaviour of Composite Walls Under Solar Irradiation and Internal Intermittent Heating

The problem of the room temperature oscillation under intermittent heating and solar irradiation is analyzed for two types of walls which have the same thermal conductance and different heat capacities. The yearly time- dependence of the sol-air external temperature is simulated by means of a Fouriers expansion, the coefficients of which are linear functions of time. In this way the analysis deals with the yearly transient state. The calculations show that the amplitude of the room temperature oscillations is markedly smaller, and nearly independent of the beginning instant of heating, in the case of walls having larger heat capacities. The effects of lack of solar irradiation or intermittent heating are also studied.