Experimental Study Of Subcooled Boiling On Heat Transfer Characteristics In Pulsating Flow

Heat transfer characteristics and two phase flow pattern of subcooled boiling under pulsating condition has been experimentally investigated and the mechanism were analyzed.Deionized water was used as the work fluid and the experiment was carried out at atmospheric pressure.In the experiments,the effect of inlet subcooling,mass flow rate and pulsating parameters on single-phase heat transfer and subcooled boiling heat transfer were analyzed and discussed,and the fluctuation characteristics of wall temperature,outlet temperature and heat transfer coefficient were presented.The experimental results could be summarized as follows:In single phase heat transfer region,the phenomenon of cross flow regime occurs by the fluctuation of flow rate which is controlled by pulsating parameters,and the pulsating parameters influence the characteristics of single phase heat transfer by changing the type and degree on the phenomenon of cross flow regime,besides,the effect of pulsating amplitude on single phase heat transfer is stronger than the effect of pulsating period.In constant flow of subcooled boiling,the mass flow rate and inlet subcooling have a influence on the characteristics of subcooled boiling.Futher,several empirical correlations for the calculation of subcooled boiling heat transfer coefficient are evaluated against the test data.Considering the effect of thermal parameters on subcooled boiling heat transfer,the Liu-Winterton empirical correlation has been corrected and the new empirical correlation has been created to predict the heat transfer coefficient of subcooled boiling.In pulsating flow of subcooled boiling,the region of subcooled boiling could be divided into the initial stage and the final stage of subcooled boiling by the influence of pulsating parameters.The mechanism on the influence of pulsating parameters on subcooled boiling has been summarized as follows: The pulsating amplitude influents the subcooled boiling by changing the range of flow fluctuation and the pulsating period influents the subcooled boiling by changing the degree of heat transfer between fluid and heated wall.And the tangent force on bubbles changed by the fluid inertia force could be neglected on influencing the subcooled boiling heat transfer.The characteristics of flow pattern in subcooled boiling under pulsating condition havebeen investigated.The flow pattern has a periodical change with the fluctuation of flow rate,and the inlet subcooling has a influence on the occurrence of flow pattern.The fluid thermal inertia can induce the occurrence of boiling hysteresis,and the shorter pulsating period could intensify the phenomenon of boiling hysteresis.