Blade-to-coolant convection heat-transfer coefficients were obtained on a forced-convection, water-cooled, single-stage turbine over a range of turbine speeds, coolant flow rates, and inlet-gas tem¬peratures. The convection coefficients were determined over a large laminar-flow range and over a portion of the transition range between laminar and turbulent flow. The range of Graetz numbers investigated was from 230 to 2400.nBoth natural- and forced-convection heat transfer were anticipated in this turbine. Natural-convection heat transfer, expressed nondimensionally by a relation between the Nusselt and the Grashof numbers, was negligible for this turbine over the Grashof number range investi¬gated from 3X109 to 4X10129. Blade-to-coolant convection coefficients were correlated by the general relation for forced-convection heat transfer for laminar flow that expresses Nusselt number as a function of Graetz number. When a characteristic dimension in the Graetz number equivalent to the length of a radial coolant passage in the blade was used, the turbine data agreed closely with a curve representing the data obtained by other investigators for laminar flow of heated liquids through stationary tubes.nWhen blade-to-coolant heat-transfer coefficients from stationary-tube heated-liquid data and theoretical gas-to-blade coefficients were used to calculate midspan average blade temperatures, the maximum deviation of calculated values from experimental data was 19° F at an experimental blade temperature of 165° F.
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