Surface Heat-Transfer Coefficeints for Hydrogen-Cooled Rotating Electric Machines

A method is given for calculating the surface heat-transfer coefficients for hydrogen-cooled roating electric machinery from the values of these coefficients as determined from tests in air. The influence of hydrogen purity and of the velocity exponent on the ratio of heat transfer in hydrogen to heat transfer in air is evaluated; also, for gas flowing in ducts, the effect of the type of flow on this ratio is discussed. A method is also given for calculating the heat-transfer coefficients for ventilating ducts, in either air or hydrogen, on an inlet temperature basis, as an aid to simplifying the calculation of the surface temperature rise.