Wet Bulb Equilibrium in a Finite Process

Abstract

WET bulb equilibrium between a liquid layer and a stream of air is established, in the absence of radiation, when the enthalpy of evaporation is entirely provided by heat transfer from the air stream. It is therefore possible to define an adiabatic surface, called here the l-surface, close to the interface and on the liquid side of it. For a control space bounded by an element of the l-surface, two cross-sectional planes normal to the air flow, and another adiabatic surface which may be the wall of a containing duct, the application of the steady flow energy equation and the liquid and vapour mass balance gives: where h′ is the enthalpy of the humid air in the bulk stream per mass of dry air, x is the mass ratio in the bulk stream (mass of vapour per mass of dry air) and hf,wb is the specific enthalpy of liquid at the l-surface.