Page:Journal of the American Society of Mechanical Engineers, Volume 33.pdf/672



71In this formula $$e_1$$ is the pressure of saturated vapor corresponding to the dew point $$T_1$$, and $$e'_2$$ is the vapor pressure at saturation corresponding to temperature $$T_2$$. It also follows that

At constant pressure

Also if it is assumed $$\frac{pv}{T}$$ is constant, i.e., $$\frac{e}{DT}$$ is constant for saturated water vapor (not exactly correct),

Therefore

But substituting $$D_2$$ for its value in [30]