Spogis
commented
8 months ago Dear @ Scorpiomom69,
Your informed points are indeed very important, but I believe you might be confusing two different pieces of information.
What you're mentioning to me is what I refer to as Absolute Humidity (g water / kg of dry air). Note that this value in the figure you sent me is 80.29 g water/kg of dry air, which is practically identical to the value obtained from (https://www.kwangu.com/work/psychrometric.htm), which is 0.0803 kg water / kg of dry air. Notice there is a difference in units! Thus, if you convert the units, you'll see that the values are identical.
The Degree of Saturation, used in Psychrometrics, refers to the ratio of the actual amount of water vapor present in the air to the maximum amount of water vapor the air can hold at a given temperature, when it is saturated. Essentially, it measures how "full" the air is with moisture compared to its maximum capacity for moisture at that specific temperature. The degree of saturation is a dimensionless number and is often expressed as a percentage. When air is fully saturated (100% relative humidity), the degree of saturation is 1.0 or 100%, indicating that the air cannot hold any more moisture at that temperature.
Relative Humidity is a measure of the amount of water vapor present in the air compared to the maximum amount of water vapor the air can hold at a given temperature. At 100% relative humidity, the air is saturated, meaning it cannot hold any more water vapor at that temperature.
Thus, the values obtained by this plugin have been extensively compared and validated with the data from the 2009 ASHRAE Handbook—Fundamentals, and with the ASHRAE Psychrometric Chart App (https://www.ashrae.org/technical-resources/bookstore/psychrometrics), global references in the field.
Please contact me if you still have any questions.
Atenciosamente / Best regards,
Prof. Nicolas Spogis, Ph.D. Phone/WhatsApp: https://wa.me/5519998440460 +55 (19) 99844-0460
E-mail: @. @.>
LinkTree: https://linktr.ee/CascaGrossaSuprema
De: Scorpiomom69 @.> Enviada em: sábado, 2 de março de 2024 08:15 Para: Spogis/Psychrometry @.> Cc: Subscribed @.***> Assunto: [Spogis/Psychrometry] Psychrometric calculation errors (Issue #1)
Hi. Thanks for posting this nice tool but I wanted to point out apparent errors in the calculation. To clarify, I have a masters degree strongly focussed on humid airflow calculations, which is where my comment originates. If you go to a site like https://www.kwangu.com/work/psychrometric.htm you can calculate the psychrometric properties of most humid airstreams pretty accurately. What's particularly interesting is the humidity ratio given. It must be noted that this is not a ratio of vapor mass to total mass, this is a ratio of vapor mass to dry air mass. The psychrometric calculations use this is because the dry air mass is constant and only the vapor mass changes. Thus the vapor mass ratio should be calculated as: (vapor mass/kg da)/(1kg dry air/kg da + vapor mass/kg da) [da = dry air, vapor mass/kg da is the humidity ratio]. This seems to be incorrectly done in your calculator as I find it impossible in many instances to generate a 100% humid air stream and also the mass fraction of the vapor ['vapor mass ratio'] is currently = to the humidity ratio in the psychrometric popup, which is not possible. I do find it interesting that the density calc works, since it requires the same foreknowledge, but perhaps this is due to rounding or different formulas, idk. Please feel free to contact me about this and thanks again for the tool. image.png (view on web) https://github.com/Spogis/Psychrometry/assets/76644903/f0554c12-eb99-49db-b869-a9cc7562542c image.png (view on web) https://github.com/Spogis/Psychrometry/assets/76644903/06aa01c2-5e5b-43c0-ab55-313c4f626fc6
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Scorpiomom69
Hi. Thanks for posting this nice tool but I wanted to point out apparent errors in the calculation. To clarify, I have a masters degree strongly focussed on humid airflow calculations, which is where my comment originates. If you go to a site like https://www.kwangu.com/work/psychrometric.htm you can calculate the psychrometric properties of most humid airstreams pretty accurately. What's particularly interesting is the humidity ratio given. It must be noted that this is not a ratio of vapor mass to total mass, this is a ratio of vapor mass to dry air mass. The psychrometric calculations use this is because the dry air mass is constant and only the vapor mass changes. Thus the vapor mass ratio should be calculated as: (vapor mass/kg da)/(1kg dry air/kg da + vapor mass/kg da) [da = dry air, vapor mass/kg da is the humidity ratio]. This seems to be incorrectly done in your calculator as I find it impossible in many instances to generate a 100% humid air stream and also the mass fraction of the vapor ['vapor mass ratio'] is currently = to the humidity ratio in the psychrometric popup, which is not possible. I do find it interesting that the density calc works, since it requires the same foreknowledge, but perhaps this is due to rounding or different formulas, idk. Please feel free to contact me about this and thanks again for the tool.
