Numerically Calculating Psychrometric Properties from Dry Bulb and Wet Bub Temp Part 1

We are going through the first stages of calculating all the psychrometric properties starting from dry-bulb temperature, wet-bulb temperature, and total pressure.

[@peacecop]

If we look into the table we see that the specific heat capacity of both air, liquid water, vapor and steam change according to the temperature. For instance, if the dry-bulb temperature is about 300 K, the specific heat of air is 1007 J / kg / K and if the dry-bulb temperature is about 280 K, the specific heat of air is 1006 J / kg / K. you just wrote down the numbers without explaining where they come from. What about 2.501? i see that it's the enthalpy of vaporization at 273.16 K. Should we always use that value or shall we consider the temperature? For instance, at 298.15 K, the heat of vaporization is 2441700 J / kg instead of 2500900 J / kg.

[@MitchellPaulus]

When I first made this video, I think I was focusing on simply getting the numerical formulations presented for computation, less on full derivations. For the enthalpy formulation that you've commented on, I made a follow-up video that does explain where those constants are from. See ua-cam.com/video/udz4Dr6AjTw/v-deo.html.
You're correct that specific heat is a function of temperature. Fortunately, over the range of temperatures that engineers in the HVAC field generally face, the differences are small enough that we can generally assume a constant value. There's no stopping someone from doing the proper integration to account for the variation - it's just that the added complexity is rarely worth it.

[@nkanyezinhlumayo6817]

Is it possible to calculate the dry bulb temperature from the humidity ratio, altitude and wet bulb temperature?

[@MitchellPaulus]

Yes - you can find a useful relation between those quantities in my other video: ua-cam.com/video/VTcnd-pCDc0/v-deo.html

[@vivekchincholi8526]

can we numerically calculate WBT by using DBT, humidity ratio And altitude

[@MitchellPaulus]

You can - It is slightly more complicated, I've written a post about it at mitchellt.com/2019/06/15/how-to-calculate-wet-bulb-temperature.html

[@mayankrajprajapat8542]

congratulation on completing your phD program .