Winter Cycle Psychrometrics
1. Draw schematic diagram of air-conditioning plant (see above).
2. Plot room condition O, M and R on psychrometric chart.
3. Plot the after Preheater condition P.
The Preheater process will be a horizontal line from O to P and acts as a frost coil in this case, heating the air to 5oC.
4. Join points P and R.
5. Find the mix point M by measuring the length of the line P-R
and multiply this by the mixing ratio.
The line measures 82mm long.
82 x 0.5 = 41 mm
6. Find the room ratio.
Plot this ratio on the protractor, so that it passes through point R.
Total heat is 17 kW sensible + 10 kW latent = 27kW.
Ratio is 17/27 = 0.63.