Example 06: Sensible heating: 'qSen' per mass (+ve): energy transfer TO humid air

The course PDF Answers (where available) from the worked example problem are given in the 3rd column in the custom table in the top of the image in IP units.

Note that the values for specific enthalpy per dry air as calculated via CoolProp are slightly different from those provided by the course Answers. The relative difference in 'hda2 - hda1' departs even more.

Note also that the answer in the course PDF is given in terms of Btu/lb, but it doesn't say whether it is per dry air mass or per humid air mixture mass. From the calculations, it seems that per dry air mass is probably meant.

When handled by the MPsy class, we have 2 objects representing the before and after states. Note how the humidity ratio 'w' of the 1st object is used to set the humidity ratio of the 2nd object, because it is assumed that there is no change in the contained water mass within the humid air.

The 2nd table that shows the differences between them, as well as indicating the change in each main psychrometric variable, and the "direction" of change.

There is a dedicated Psy library function for calculating the sensible heat energy 'qSen' (in this case added to the system so +ve).

Webel: Psy/MPsy: Psychrometrics for Mathematica: Transferred heat (energy "Q") has field names with lower case 'qTot', 'qSen', 'qLat'. Heat rates (energy per time) have field names 'qDotTot', 'qDotSen', 'qDotLat' (to avoid clashes with Mathematica core)

Wikipedia: 'Heat released by a system into its surroundings is by convention a negative quantity (Q < 0); when a system absorbs heat from its surroundings, it is positive (Q > 0). '

And the psychrometric chart function shows both states, as well as an arrow indicating the change.

Up next

Example 07: Sensible cooling: 'qDotSen' (-ve): energy transfer rate FROM humid air

Notes

[COMPLICATION, GOTCHA, TIP]{INFORMATIVE} GOTCHA: Mathematica: Specific enthalpy conversion J/kg to Btu/lb: Does not consider a possible "total" enthalpy reference offset vs 0 °C or 0 °F respectively

[CONVENTION]{STRICT} Webel: Psy/MPsy: Psychrometrics for Mathematica: For Imperial Units (IP), International British Thermal Units (Btu) are assumed

[ASSERTION, GOTCHA, WARNING]{INFORMATIVE} In the course PDF for 'CED Engineering: Air Conditioning Psychrometrics (A.Bhatia)' the term "enthalpy (h)" usually refers to the mass-specific enthalpy per dry air (in CoolProp notation 'Hda')

[CONVENTION]{STRICT} Webel: Psy/MPsy: Psychrometrics for Mathematica: Transferred heat (energy "Q") has field names with lower case 'qTot', 'qSen', 'qLat'. Heat rates (energy per time) have field names 'qDotTot', 'qDotSen', 'qDotLat' (to avoid clashes with Mathematica core)

Snippets (quotes/extracts)