NDLI: Validation of ASHRAE Equation to Find Evaporation Rates in Humid Cavity

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Kuravi, Suma Agonafer, Dereje
Copyright Year	2004
Abstract	Presence of Humidity has many undesired effects in many applications. Moisture balance of the air has become an important task and dehumidification has become a necessity for many applications in many industries. This paper discusses about the study of the factors affecting the evaporation rate of water in cavities exposed to humid conditions. The ASHRAE equation to find the evaporation rate in swimming pools is considered and validated for a small pool of water in humid conditions in humid cavity with fixed dimensions. The equation states that, the evaporation rate, W = (95+0.425V)(Pw-Pa)/Y, where W is the Evaporation rate in lb/h-ft2; V is the air velocity at water surface; ft/min; Pw is the saturation vapor pressure at water temperature, in. Hg; Pa is saturation vapor pressure at air dew point, in. Hg; and Y is latent at water temperature, Btu/lb. The evaporation rate inside the humid cavity is found and compared with that of the equation. The evaporation rate obtained inside the humid cavity is 95% of the evaporation rate obtained by the use equation. The factors responsible for the low evaporation rate are identified. A CFD Model is developed using FLUENT to represent the time averaged steady state condition of the humid cavity. The temperature and velocity values at particular points are probed in CFD model and are obtained. The results are compared with the actual physical model. These values are used to find the evaporation rate occurring inside the cavity using the ASHRAE equation. The evaporation rate found in the humid cavity is found to be 76% of the evaporation rate that is calculated from the values of the CFD model, using the equation. Factors affecting the evaporation rate inside the humid cavity are discussed and the effects of these factors are illustrated using the CFD Model. Propositions are made to improve the evaporation rates inside the humid cavity. Future studies are planned to do a multi species modeling to include humidity in the CFD analysis for humid cavity.
Sponsorship	Heat Transfer Division
Starting Page	109
Ending Page	116
Page Count	8
File Format	PDF
ISBN	079184711X
DOI	10.1115/IMECE2004-61942
Volume Number	Heat Transfer, Volume 2
Conference Proceedings	ASME 2004 International Mechanical Engineering Congress and Exposition
Language	English
Publisher Date	2004-11-13
Publisher Place	Anaheim, California, USA
Access Restriction	Subscribed
Subject Keyword	Water Cavities Temperature Computational fluid dynamics Vapor pressure Dehumidification Dimensions Evaporation Water temperature Modeling Steady state
Content Type	Text
Resource Type	Article

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