AXIAL TEMPERATURE GRADIENT IN FLOW WITH SURFACE BOILING.
PITTSBURGH UNIV PA
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The purpose of the investigation was to determine how the temperature of subcooled water varies as it flowed through a heated pipe. The inside wall temperature of the pipe was high enough to cause surface boiling. It was seen that the water temperature did not increase for approximately the first foot along the test section. It was felt that this reflected the period required for the thermal boundary layer to grow to its fully developed form. Several approximations to heat transfer theory were used to arrive at an expression for the distance required for the boundary layer to develop. Agreement with experimental results was within thirty-five per cent. In runs where the saturation state was attained the maximum temperature was always greater than saturation temperature. It is assumed that bubbles of superheated steam in the water caused the thermocouples to sense an average temperature between saturated water and superheated steam. It was also noted that in some cases the temperature continued to increase in this region. Not enough is known about two phase mixtures to be able to explain this pattern.