Comparison of the effect of 1st order and 2nd order fluctuating temperature field on convective heat transfer coefficient in an unsteady laminar-boundary layer

Abstract

Abstract An unsteady thermal boundary layer analysis over a heat source (flat plate) has revealed that first order temperature change in source and core flow temperatures affects the time average or RMS value of h’S. It also emphasize that 1st order changes are important. Analysis also indicates that a phase difference between pressure and temperature exists at the source in order to increase the RMS value of h’S. Value of h’S is directly proportional to the tan/sine of the above phase difference, This implies that entropy oscillations must exist at the heat source. The purpose of this paper is to compare the result of 2nd order analysis previously done, with the 1st order study carried out in this paper. In second order analysis time average of h”S depends upon 2nd order change due to 1st order effects. Finally, existence of phase difference between pressure and temperature, thus having entropy oscillations are evident, comparison implies although there is similarity between 1st order and 2nd order results but first order effects are more important than 2nd order effects.