Transient convective heat transfer to a turbulent flow from a flat plate with constant heat capacity

The studies on transient heat transfer are very few though the cases in which transient heat transfer becomes problem have arisen recently, such as nuclear reactors or automatic control equipment. In the previous report, the author has described the method to determine by numerical analysis the transient response regarding the transient heat transfer to turbulent flow when a flat plate with constant heat capacity is abruptly given a certain heat value, using arbitrary Prandtl number and turbulent Prandtl number. In this report, the author describes on the experimental study on the transient heat transfer in a turbulent boundary layer by modifying the previous experimental apparatus so as to suit the experiments for turbulent boundary layers. The experiments have been performed by applying constant heating current abruptly to a flat plate from a storage battery by the starting-up of a thyristor, and flowing water at constant speed, and by recording the local wall temperature and heating current with an electromagnetic oscillograph, using an evaporated thin nickel film as a resistance thermometer. When turbulent boundary layer was made at the front edge of the flat plate by a tripping wire of 0.65 mm diameter provided on the up-stream side of the plate, the turbulent Prandtl number showed the value of 0.79 in the water flow having the Reynolds number of approximately 3 x 105. Also, the experimental results well agreed with the calculated results obtained by the previous numerical analysis, assuring the propriety of the numerical analysis. (Wakatsuki, Y.)