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

The heat transfer of a critical flow in a small-sized has not been studied in detail, since the flow is too complicated. In this paper, the two-dimensional compressible laminar boundary layer equations in a parallel with heat transfer are solved numerically. The obtained results reveal that the two-dimensional critical flow patterns are classified by nozzle characteristic number xc. The local and mean heat transfer coefficients in the critical nozzles were calculated by defining an adiabatic wall temperature as gas temperature in reference. Especially, it is found that the local heat transfer coefficients rise sharply near the exit. The mean Nusselt numbers obtained numerically can be plotted on a single curve independent of the non-dimensional wall temperature θw, being arranged on the basis of modified characteristic Reynolds number Xcdw; furthermore they can be approximated by incompressible ones, if arranged on the basis of Xcdws-1 defined as the state of sonic point in the critical nozzle.