Heat Transfer and Pressure Drop Characteristics of Water in the Transitional Flow Regime of Horizontal Smooth Tubes at Constant Wall Temperature

Owing to design limitations, heat exchangers are frequently forced to operate in the transitional flow regime, however, there exists no accurate measurements for both heat transfer and pressure drop in this region. In order to optimize a heat exchanger for maximum efficiency and minimum pressure losses, it is required to design it for the transitional flow regime. Therefore, the purpose of this study is to obtain accurate Nusselt numbers and pressure drop coefficients for water flowing through a horizontal smooth tube with a constant wall temperature. Heat transfer and pressure drop measurements were conducted on a 5.33 mm tube at Reynolds numbers ranging from 1 000 to 5 000.