NUCLEATE POOL BOILING OF A TURBO-B BUNDLE IN R-113

Heat transfer measurements were made during nucleate boiling of R-113 from a bundle of 15 electrically heated, copper TURBO-B tubes arranged in an equilateral triangular pitch, designed to simulate a portion of a flooded evaporator. Five of the tubes that were oriented in a verti cal array on the centerline of the bundle were each instrumented with six wall thermocouples. For increasing heat flux, the incipient boilin g wall superheat of upper tubes decreased as lower tubes were activate d. In the boiling region at low heat fluxes (almost-equal-to 1 kW/m2), the average bundle heat transfer coefficient was 4.6 times that obtai ned for a smooth tube bundle (under identical conditions) and 1. 6 tim es greater than that obtained for a single TURBO-B tube; a similar bun dle factor has been reported for a smooth tube bundle. At high heat fl uxes (100 k W/m2), the average bundle heat transfer coefficient was 3. 6 times that of a smooth tube bundle. Furthermore, there was still a s ignificant bundle factor (1.22), contrary to a smooth tube bundle, whe re all effect of lower tubes was eliminated at high heat fluxes.