HVAC · Psychrometrics · Problem 2PDFSolution in PDF ↓
HVAC · Psychrometrics · Problem 2
Problem & Solution
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Problem: Psychometrics problem too.
Given: 000 BTU's power; 5 in this case; 0.00108 pounds of water per pound of dry air
Approach: An outside air handling unit is equipped with a hot water coil to temper the fresh air intake during winter operation.
Calc: The outside conditions are 20 degrees and 50% relative humidity.
Calc: It's winter operation, 20 degrees and 50% relative humidity.
Result: So then the only thing that we have to do is use the conditions at state 1 to look up the humidity ratio, which we would normally use the psychomet...
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Student questions asked in live office hours about this problem
OH 96: HVAC: Psychrometrics Module #2
Q: For temperatures below 35°F on the psychrometric chart, how do we find properties like enthalpy, and can we use the lever rule to find relative humidity?
A: Below 35°F, use the Moisture Properties table in the reference handbook and interpolate between dry and saturated air conditions. For the lever rule: it works for linear parameters (dry bulb, wet bulb, humidity ratio, enthalpy, specific volume) but NOT for relative humidity, which is curved—so find two other known properties first, then read relative humidity directly off the chart.