Numerical Predictiono f Laminar Flow and Heat Transfer in a Tube with Twisted-tape Insert: Effects of Property Variations and Buoyancy

摘要

In a recent experiment with laminar flow of Servotherm oil in a horizontal tube containing a twisted tape, the Nusselt number is correlated with Rayleigh number in addition to the forced ocnvection parameters [1]. For Servotherm oil, density and viscosity vary appreciably with temeprature. The measured Nusselt numbers were found to be higher than those predicted by the earlier isothermal correlation. The purpose of this study is to investigate if this difference arises becasue of property variations or becuase of buoyancy. Numerical predictions can assist in this inquiery. Based on numerical predictions, appropriate correlations are derived and the resutls compared with experimental correlations.