Moist Air newbie question: "Properties of the moist gas are physically unrealistic"

W.Scott.Dempster — Tue, 14 Mar 2023 17:48:25 GMT

Hi all -- Happy Pi Day!

I am doing a small CFD study to observe the effects of very hot and humid air running through a copper tube.

I was able to successfully run the simulation with regular Air as my fluid material with BC's of temperature of 85C, humidity of 98% RH, at a volumetric flow rate of 1 L/min. However, I recently learned that I should have been using Moist Air instead, and swapped it in for the Air and enabled the Humidity option in the Advanced settings of the Solver.

When trying to Solve, I get the Error: "Properties of the moist gas are physically unrealistic. The vapor pressure is greater than or equal to the absolute pressure." with suggested solutions of to increase the Reference Pressure or reducing the temperature BC.

I have tried both solutions by increasing the pressure from 101,325 Pa to 500,000 Pa and reducing the temperature from 85C to 60C and I am getting the same solution, so I am unsure if I am doing this correctly or there is something I am overlooking, so I would appreciate input.

Here is a link with the Support files since I am getting an error trying to directly attach it (errors love me today).

https://drive.google.com/file/d/1-fmCyBdwIL6xm0mv0llzR9kQU6sa11uF/view?usp=sharing

Re: Moist Air newbie question: "Properties of the moist gas are physically unrealistic"

karol.suchon — Thu, 16 Mar 2023 10:45:55 GMT

Hello,
Humidity Bc should be applied in the range between 0-1. So we do not use the % value.

Try to change that and let me know if that help.
BR
Karol

Re: Moist Air newbie question: "Properties of the moist gas are physically unrealistic"

W.Scott.Dempster — Thu, 16 Mar 2023 13:01:54 GMT

I knew it would be something silly. Thanks!

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Moist Air newbie question: "Properties of the moist gas are physically unrealistic"

Re: Moist Air newbie question: "Properties of the moist gas are physically unrealistic"

Re: Moist Air newbie question: "Properties of the moist gas are physically unrealistic"