Procedural Errors in Experimental Investigations of Boiling Heat Transfer under Conditions of Free Convection

摘要

A series of following typical procedural errors are analyzed, which are made in the case of experimental investigations of boiling heat transfer under conditions of free convection. (1) The volume of the experimental vessel is too small, and heat transfer is investigated in the gap between the walls of the vessel and experimental section. (2) The working volume is not thermostatically controlled. Additional convection flows cause a variation of temperature head in the region of transition from convection to boiling. (3) The small relative length of the experimental section prevents one from correctly determining the value of specific heat flux. (4) Measurements are performed only when the heat flux decreases. The hysteresis effect may cause a significant variation of the temperature head being determined. (5) The short-term mode of film boiling, which sometimes arises after convection, causes a thermal decomposition of heat-transfer agent, formation of oxide films on the experimental sections, and significant decrease in heat transfer. The description of the experimental setup, of the adopted measurement procedure, of the experimental section, and of the quality of heat-transfer agent must be given in publications in greater detail than is common practice at present.