Problem: a warehouse located in a damp climate uses two-pipe heating fan coil units to maintain a maximum relative humidity of 60%.
Given: 200 CFM fan coil units; 1.08 CFM delta T
Approach: So this is an interesting situation we have a warehouse and they're using heating fan coils to keep the relative humidity from ...
Calc: So this is an interesting situation we have a warehouse and they're using heating fan coils to keep the relative humidity from ...
Calc: This might be the 80% curve and maybe this is the 60% curve, something like that.
Result: The best answer choice is A.
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Student questions asked in live office hours about this problem
OH 29: HVAC 5
Q: Can you explain the rule of thumb for Q_water and Q_air — what's the underlying logic, and what's the alternative approach using the PE reference handbook?
A: The rule-of-thumb equations (Q = 1.08 × CFM × ΔT for air; Q = 500 × GPM × ΔT for water) are derived by folding the specific heat and density of each fluid at standard conditions directly into the formula. If conditions deviate significantly from standard, fall back on the full mass-flow-rate approach (Q = ṁ × Cp × ΔT) for better accuracy.