关键词: 自然对流, 旋流片, 仿真模拟, 糖液

Abstract: The natural convection heat transfer of 60% sucrose solution in the vertical converging-diverging tube (CD) with regularly-spaced twisted tapes (RSTT) has been investigated numerically and experimentally. The effects of wall temperature and numbers of RSTT on the Nusselt number are performed in detail. The distributions of velocity and temperature for 60% sucrose solution are studied and the simulated results of CD with RSTT were compared with the smooth tube. The influence of Rayleigh number and RSTT on Nusselt number was conducted experimentally. The results indicate that the Nusselt number of 60% sucrose solution obviously increased with the number of RSTT but increased inconspicuously with 2 twisted tapes and more. The simulation shows that the distance to reach the optimal heat transfer performance is 46 times the diameter of the tube. The mechanism of the natural convection heat transfer enhancement of 60% sucrose solution interrelated by the CD and the RSTT was analyzed, and the change of average tangential velocity with the axial distance was presented to demonstrate that the enhancement of heat transfer was mainly due to the increase of tangential velocity.

Key words: natural convection, regularly-spaced twisted tapes, numerical simulation, sucrose solution