关键词: 三角形螺旋夹套, 黏度, 换热, 流动

Abstract:

Considering fluid temperature-dependent viscosity, turbulent flow and heat transfer in the jackets with helical ducts were investigated numerically. Comparisons between experimental values and simulated values indicated that the simulation method was reliable. Based on the simulated results, the effects of temperature-dependent viscosity on the characteristics of turbulent flow and heat transfer were studied, variations of the mean flow resistance (fRe_m) and mean Nusselt number (Nu_m) of cross section in the flow direction were analyzed, and the whole flow resistance and the whole Nusselt number of varied viscosity flow were compared with those of constant viscosity flow. The results show that temperature-dependent viscosity affects the features of fluid flow and heat transfer in the jackets to a certain extent. The development of fRe_m and Nu_m along the axial direction is divided into the early, the middle and the later stages. The difference is obvious at the later developing stage between the trends with varied viscosity and constant viscosity. Under the same incoming flow and thermal boundary conditions, compared to those with constant viscosity, the local flow resistance with varied viscosity is lower, the local Nusselt number is larger, so that the whole flow resistance is lower and the whole Nusselt number is larger. Furthermore, with the decrease of the Reynolds number and the dimensionless curvature ratio, differences between the characteristics of flow and heat transfer for varied and constant viscosities are more obvious, so temperature-dependent viscosity is a greater contributing factor to fluid flow and heat transfer.

Key words: jackets with triangular helical ducts, viscosity, heat transfer, fluid flow