Evaporation of water by free or mixed convection into humid air and superheated steam

Abstract This paper concerns a numerical analysis of the evaporation of water in pure air, humid air and superheated steam in an externally insulated channel. Results were obtained for mixed and free convection driven by combined thermal and mass buoyancy forces. For natural convection case, the analysis is restricted to situation in which combined buoyancy forces act in the downward direction. The results show that below a certain temperature of the free stream, water evaporation rate decreases as the humidity of air increases and above it this relation reverses. This temperature “inversion point temperature” was treated in previous experimental and numerical studies in the case of forced convection. In this work, particular attention is paid to study the effect of the ambient conditions on evaporation rate of water and the inversion temperature phenomenon in the condition of free and mixed convection.

[1]  J. Chung,et al.  SIMULATED DEHYDRATION OF WEDGE-SHAPED SPECIMENS IN TURBULENT FLOW OF SUPERHEATED STEAM AND AIR , 1989 .

[2]  J. P. Schwartze,et al.  The evaporation of water into air of different humidities and the inversion temperature phenomenon , 2000 .

[3]  Tsing-Fa Lin,et al.  Combined heat and mass transfer in natural convection between vertical parallel plates with film evaporation , 1990 .

[4]  W. Yan,et al.  Convective heat and mass transfer along an inclined heated plate with film evaporation , 1995 .

[5]  L. C. Chow,et al.  Evaporation of water into a laminar stream of air and superheated steam , 1983 .

[6]  Louis C. Chow,et al.  Experimental Measurement of Water Evaporation Rates Into Air and Superheated Steam , 1988 .

[7]  J. Whitelaw,et al.  Convective heat and mass transfer , 1966 .

[8]  Wei-Mon Yan,et al.  Natural convection flows in a vertical, open tube resulting from combined buoyancy effects of thermal and mass diffusion , 1986 .

[9]  S. Ben Nasrallah,et al.  Evaporation of water by free convection in a vertical channel including effects of wall radiative properties , 2001 .

[10]  J. Chu,et al.  Evaporation of Liquids into Their Superheated Vapors , 1953 .

[11]  Frank P. Incropera,et al.  Fundamentals of Heat and Mass Transfer , 1981 .

[12]  R. Shah.  Laminar Flow Forced convection in ducts , 1978 .

[13]  Tsing-Fa Lin,et al.  Cooling of a falling liquid film through interfacial heat and mass transfer , 1990 .

[14]  Tetsuo Yoshida,et al.  Evaporation of Water in Air, Humid Air, and Superheated Steam , 1970 .

[15]  L. Chow,et al.  Simulation of wedge-shaped product dehydration using mixtures of superheated steam and air in laminar flow , 1987 .

[16]  Robert R. White,et al.  ENGINEERING AND PROCESS DEVELOPMENT Drying Granular Solids in Superheated Steam , 1951 .