Incipient boiling and burnout heat flux for subcooled water flowing in annuli containing heated concentric wires

Incipient boiling and burnout heat fluxes were studied for sub-cooled forced convection annular flow. Small wires varying from 0.010 to 0.020 inch in diameter were used as the inner core of the annulus and a one inch ID glass tube 24 inches long was used as the outer tube. This gave diameter ratios from 100:1 to 50:1. The water flow rate varied from 685,000 to 2,710,000 LBM/(hr.ft.²) at a constant temperature of 208.4°F and a constant pressure of 18.7 psia. Alternating current was supplied to the wires, and the power required for incipient boiling and burnout heat flux measured. Incipient boiling heat fluxes varied from 70,200 to 254,000 BTU/(hr.ft.²) while burnout heat fluxes ranged from 638,000 to 921,000 BTU/(hr.ft.²). For the range of operating conditions considered it was found that the heat transfer coefficient for incipient boiling was much less than predicted by other investigators. Measured burnout heat flux agreed well with an empirical relationship developed by Weatherhead