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 dinis November 21, 2002 15:04

Moist Air

I am trying to simulate the thermal and airflow behaviours in the refrigeration envelope of open display cases. Since the operation of those equipments is very sensitive to relative humidity, i would like to evaluate the equipment's (+ evaporator) performance under various relative humidity conditions. So, it was considered the fluid as air with a water-vapor concentration given as function of relative humidity (Amagat's Law in ideal gas mixtures). Which model should i use to simulate this condition: 1) Species Transport without chemical reactions, considering a mixture of air with a mass fraction of water-vapor?

?(Since the misture is in gas phase, I have many doubts in the use of following models, considering water-vapor (gas) as droplets)? 2) Euler-Euler Multiphase model - Mixture model, considering a mixture of air with a volume fraction of water-vapor) or, 3) Since the concentration of water-vapor in the atmospheric air is very low, should i use the na Euler-Lagrange Approach - discrete phase model? Aferwards, i would like to introduce thermal radiation in the simulation. For this case, which model should i use to simulate the air(gas)+water-vapor(gas) to obtain more accurate results. Also, can anyone suggest me bibliographical references to find mean values to absorption and scattering coeficients, and to refractive index for air and water-vapor in the IR wavelength. Thanks,

 Erwin November 22, 2002 06:50

Re: Moist Air

If you assume water exists as droplets you actually have saturated air, i.e. relative humidity = 100 %. So I guess you probably don't want to use any multiphase model but use a species transport model. You can add diffusion coefficients if necessary.

Air (humid or not) does not have a significantly scattering effect. Water droplets do (think of mist), but like I said I assume you don't have any.

The only components radiating in your mixture are CO2 and H2O. You could decompose air into its molecular components N2, O2, CO2 and H2O and then use the WSSG method for absorption.

 mahdi saniee nezhad November 24, 2002 01:46

Re: Moist Air

Dear sir I have a problem with this title. If it's possible for you please send me your received responses. Very thanks for your attention to my request. With the best regards. Mahdi saniee nezhad

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