BOILING HEAT TRANSFER IN A NARROW VERTICAL RECTANGULAR CHANNEL (RELATIONSHIP BETWEEN HEAT TRANSFER COEFFICIENT AND PERIOD OF PASSING BUBBLE).

An experimental study has been made of saturated boiling heat transfer for water and R 113 in a narrow vertical rectangular channel (2 mm space, 20 mm wide, and 200 mm long) at atmospheric pressure, in which the vertical heated surface (10 mm long, 20 mm wide) is located on one side at a position 150 mm from the entrance and bubbles are forcibly passed through it at designated period of 0. 033 to 1. 0 sec. The experiment shows that the heat transfer coefficients are increased by the bubble passing through the heated surface for the value of thermal diffusivity, a, times period, T//0, of the passing bubble above about 6 multiplied by 10** minus **9 m**2 (aT//0 greater than 6 multiplied by 10** minus **9), while for aT//0 less than 6 multiplied by 10** minus **9 m**2, the heat transfer coefficients become independent of the period.