The Maximum and Minimum Values of the Heat Q Transmitted from Metal to Boiling Water under Atmospheric Pressure

The quantity of heat transmitted from a metal surface to boiling water increases as the temperature difference ΔT is increased, but after the ΔT has reached a certain limit, quantity Q decreases with further increase in ΔT. This turning point is the maximum value of heat transmitted. The existence of this point was actually observed in the experiment. Under atmospheric pressure, ΔT corresponding to the maximum value of heat transfer for water at 100°C falls between 20 degC to 40 degC, and Q is between 1080000 and 1800000 kcal/m2 h (i.e. between 2000 and 3000 kg/m2h, if expressed in constant evaporation rate at 100°C) ; this figure is larger than the maximum value of heat transfer as was previously considered. Also, the minimum value of heat transfer was obtained, and in the Q−ΔT curve for the high temperature region, the burn-out effect is discussed.