Experimental Investigation of the Heat Transfer Characteristics of Liquid Nitrogen in the Capillary Tubes

The heat transfer characteristics of liquid nitrogen in both capillary tubes and open bath are experimentally investigated in the present study. The experiments are conducted by using a thin wire heater as both the heating element and the thermometer under the inclination angles of 0deg to 90deg with the interval of 30deg. The diameters of the capillary tubes are 3.8 mm and 1.2 mm. It is found that the nucleate boiling heat transfer can be enhanced with the capillary tube in some cases. The heat transfer enhancement increases with the decrease of the diameter of the capillary tubes. The visualization shows that the appearance of the boiling phenomenon in the capillary tube is different from that in the open bath. The measurement results show that the critical heat fluxes (CHFs) were affected by the inclination angle and the diameter of the capillary tube