The determination of the specific heat of superheated steam by throttling and other experiments

Abstract

In October, 1898, the author commenced experiments, having for their object the determination of the specific heat of superheated steam. At first an attempt was made to obtain this end by measuring the rise in temperature produced in a known quantity of steam by supplying a definite amount of heat in the form of electrical energy, but the experimental difficulties experienced in satisfactorily preventing radiation, in maintaining the rate of flow of steam uniform and in securing a steam supply sufficiently homogeneous and constant as to temperature, proved so great that the attempt on these lines was given up for a time, but returned to later. Then another method was adopted, that of allowing dry saturated steam to expand without doing external work, and observing the resulting change in temperature. This method had been used in preliminary experiments on this subject by Professor Ewing and Mr. Dunkerley, who found that the specific heat of superheated steam at atmospheric pressure, as deduced by this method from Regnault’s values of the "total heat,” was not a constant, as had been previously supposed, but increased with temperature.