ENHANCEMENT OF HEAT TRANSFER DURING TURBULENT FLOW IN PLANE AND CIRCULAR NONSEPARATING DIFFUSERS

Consideration is given to the possibility of enhancing heat transfer in circular and plane nonseparating diffusers with small opening angles. Numerical modeling of the heat transfer was performed with the three-parameter differential turbulence model supplemented with the transfer equation for the turbulent heat flux. It has been show that at the same opening angle, the Nusselt number in the circular diffuser is much higher than that in the plane diffuser, with this excess growing with opening angle. However, the Reynolds analogy factor for the circular diffuser is only slightly higher than that for the plane one. A study has been made of the influence of the Reynolds number, the diffuser length, and the Prandtl number of the heat-transfer agent. It has been shown that the minimum effect of heat-transfer enhancement is attained for gases with a small Prandtl number and depends weakly on the Reynolds number and the diffuser length.