Boiling heat transfer of Freon-113 flowing normal to a tube: effect of tube diameter
The effect of heater diameter on the pool and flow boiling heat transfer of saturated Freon-113 was examined. The heaters were horizontal copper tubes of diameter 1.59 to 7.94 mm (pool) and 3.18 to 12.7 mm (flow), heated internally by condensing steam. The test fluid, at atmospheric pressure, flowed upward normal to the heaters, at approach velocities of 2.4, 4.0, and 6.0 m/s. For flow boiling, at a fixed velocity and wall temperature, smaller tubes resulted in higher heat flux values. The maximum heat flux was proportional to the 0.44 power of velocity and inversely proportional to the 0.28 power of diameter. In pool boiling, the critical diameter was different for each regime of boiling, depending on the regime's characteristic length. For tubes smaller than this critical diameter, heat flux increased as the tube size decreased for a fixed wall temperature. Tubes larger than the critcial diameter showed no diameter effect on the heat flux except for transition boiling. In this region, the heat flux increased as the tube diameter increased beyond the critical diameter.
- OSTI ID:
- 5563194
- Country of Publication:
- United States
- Language:
- English
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