Thermal Striping Tests in Mixing Tees with Same Pipe Diameters (2nd Report, Characteristics of Heat Transfer of Temperature Fluctuations)

Abstract

Thermal striping tests in mixing tees with same pipe diameters were conducted in order to construct databases for entablishment of an evaluation method for high-cycle thermal fatigue of piping systems. Hot and cold water with a terperature difference of 40 degrees Kelvin were supplied to the mixing tee. In order to clarify characteristics of fluid temperature fluctuations and its heat transfer, temperature fluctuations of the fluid and pipe wall were measured as the velocity ratio of the flow in the branch pipe to that in the main pipe was varied from 0.1 to 5. Characteristics of flow patterns and fluid temperature fluctuations were reported in our previous paper. In this paper, heat transfer coefficients were evaluated by using the power spectrum method. The ratios of the measured heat transfer coefficient to that evaluated by Dittus-Boelter's empirical equation were independent of the velocity ratio and Reynolds number, and they were within 1.6.