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Calculations of wet bulb when dry bulb above 100 C converge to unreasonable value #31

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dmey opened this issue Mar 21, 2019 · 3 comments
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@dmey
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dmey commented Mar 21, 2019

The calculations of wet bulb when dry bulb when above 100 C are not handled properly.
The convergence tests implemented (test_GetTDewPointFromVapPres_convergence) converge to unreasonable values when hen above 100 C. For example GetTWetBulbFromRelHum(TDryBulb, RelHum, Pressure) with TDryBulb = 25, RelHum = 1 and Pressure = 101325. As expected the function returns 25 (when the air is saturated, wet bulb = dew point = dry bulb). With TDryBulb = 99 it returns 99.. When called with TDryBulb = 101 it returns 43.

@dmey dmey added the bug label Mar 21, 2019
@dmey dmey added this to the Future milestone Mar 21, 2019
@dmey
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dmey commented Apr 8, 2020

@didierthevenard we may want to revisit this at the next release -- do you have any thoughts?

@dmey dmey modified the milestones: Future, 2.6.0 Apr 11, 2020
@dvd101x
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dvd101x commented Jan 9, 2022

Hi, I'm sorry this is a bit off topic but maybe it's useful for review:

I'm testing two libraries in javascript: coolprop for thermodynamics and mathjs for units and other math stuff.
When testing
HAprops('DewPoint', { 'Tdb': 25 degC, 'P': 1 atm, 'RelHum': 100 % }) to degC
The results is:
25.000000000064 degC

You can benchmark here if you would like:
https://github.com/dvd101x/CoolPropJavascriptDemo

@PHCEAC
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PHCEAC commented May 5, 2023

I apologise if this is completely obvious, but it seems that GetTWetBulbFromRelHum should be evaluating Psat * RelHum at the very beginning, and verifying that it is not larger than than the actual value of Pressure, which would indicate supersaturation, and therefore "unphysical" in the world of psychrolib.
If not obvious, did I misunderstand something?

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