AbstractIn support of the High Flux Isotope Reactor Program, experimental determinations were made of friction factors, burnout heat fluxes, and average and local nonboiling heat-transfer coefficients for forced-convection flow of water through thin aluminum and nickel rectangular channels under the following conditions: heat flux = 0.1×106to 7.4×106Btu/h·ft2, velocity = 10 to 85 ft/sec, Reynolds number = 9,000 to 270,000, pressure = 1 to 39 atmospheres absolute, flow gap = 0.043 to 0.057 in., and heated length = 12 and 18 in. A few tests were made to ascertain the effect of an axially oriented cylindrical spacer strip on surface-temperature distribution and burnout heat flux. The results of these studies, unlike those of some earlier investigations of narrow-gap heat transfer, are in reasonably good agreement with accepted correlations. The friction factors are in satisfactory agreement with the Moody chart for the relative roughness of the test sections used, the burnout heat fluxes are well reproduced by the Soviet Zenkevich-Subbotin correlation, and the local and average heat-transfer coefficients are slightly larger than values predicted by the Hausen and Sieder-Tate equations.