Heat Transfer of the Critical Air Flow in a Nozzle : 2nd Report; Experimental Study on Heat Transfer of the Critical Air Flow in a Nozzle with Parallel walls

Abstract

Numerical analysis of the laminar heat transfer in the critical parallel nozzle has been reported in the first paper by the authors. In this report, the mean Nusselt number "Numc" of the critical flow is measured experimentally to compare with the numerical results. It is shown that the critical flow in parallel nozzle is laminar over the whole length of a nozzle when X_cdw^-1 &lsim;10², where X_cdw^-1 is the nozzle characteristic Reynolds number. Turbulence arises when X^cdw<-1> &gsim; 10², so in this range the influences of three non-dimensional parameters, i.e., sonic point Reynolds number Recdw, ratio of nozzle height to nozzle length d/L and non-dimensional wall temperature Θw are analyzed. Consequently, the experimental expression of the "Numc" can be given. Furthermore, to verify the adequancy of numerical and experimental results, two methods of optical observation are adopted. The optical results agree well with the laminar numerical ones for X_cdw^-1 &lsim; 10².