The effect of free convection on entry flow between horizontal parallel plates

In the entrance region of a parallel plate rotary heat exchanger or regenerator, the velocity and temperature distributions are developing, leading to modified values of friction factor and heat transfer coefficient in that region. These parameters are further affected by natural convection. A description is presented of the results of a numerical (finite difference) study of the development of the velocity and temperature distributions in the entrance region of a cascade of parallel horizontal plates, the temperature of which is different from that of the incoming fluid. The flow has been assumed to be uniform some distance upstream of the cascade. The thickness of the plates has been taken into account. It is found that the friction is more strongly affected by free convection than is the heat transfer. This is consistent with the fact that the direct effect of the free convection is an additional force in the momentum balance.