SOLUTION FOR ACR3422 PSYCHROMETRICS 1ST ASSIGNMENT

Question 1:
Locate points for recirculated and outside air on the chart. connect with a straight line. Read specific volumes of air at each point from chart. Convert cfm of air to pounds of air and find total weight of mixture.
7500/13.22 = 567.3 lbs./min
2500/14.37 = 173.9 lbs./min
Total weight = 741.2 lbs/min
Dry bulb of mixture =
(567.2/741.2)*57=43.6
(173.9/741.2)*96=22.5
Therefore, DB=66.1 deg F
From intersection of 66.1 deg F DB line with line between two points, read WB=62.1F, h=27.83 Btu/lb. dry air, humidity ratio = 77.1 gr. of moisture/lb. of dry air.
Approximate solution does not convert cfm to pounds per minute.
(7500/10 000)*57 = 42.75
(2500/10 000)*96 = 24.00
Mixture DB = 66.75 deg F.
At intersection of this line with line between two points, read WB = 62.5 F, h = 28.1 Btu/lb. dry air, humidity ratio = 78.0 grains of moisture/lb.of dry air.

Question 2:
Locate the initial condition on the chart. Draw a horizontal line through the initial point to the 95 F DB line. Read 7.3% RH, WB = 59.2 F and DP = 23.5 F.
Read enthalpy of initial air as 11.1 Btu/lb=h1
Read enthalpy of final air as 25.6 Btu/lb. = h2.
Heat added equals difference 14.5 Btu/lb.

Question 3:
Locate the initial and final conditions on the chart.
For the initial condition read W1 = 81.7; h1 = 32.48
For the final condition read W2 = 56.2; h2 = 21.4
Heat removed: h2 - h1 = 21.4 - 32.48 = -11.08 Btu/lb.dry air.
Moisture removed: W2 - W1 = 56.2 - 81.7 = -25.5 grains.
To determine the SHR, draw a straight line between the initial and final conditions. Draw a line parallel to this one from the reference point at 78 F DB and 50% RH to the sensible heat ratio scale. Read SHR = 63.8