Calculators › HVAC and building envelope Air latent heat rate calculator
Air latent heat rate
Standard-air latent load uses the moisture change in grains per pound of dry air rather than relative humidity. Standard-air latent load uses the moisture change in grains per pound of dry air rather than relative humidity.
Units IP (US) SI (metric)
q latent = 0.68 × C F M × Δ gr q_{\text{latent}} = 0.68 \times \mathrm{CFM} \times \Delta \text{gr} q latent = 0.68 × CFM × Δ gr q latent = 3 × Q air × Δ w q_{\text{latent}} = 3 \times Q_{\text{air}} \times \Delta w q latent = 3 × Q air × Δ w
Calculator
Enter the values you know and leave one box empty. Calculate finds the empty one, the result or any input.
Worked example
Given
C F M \mathrm{CFM} CFM 4,500 cfm Δ gr \Delta \text{gr} Δ gr 22 grain/lb q latent = 0.68 × 4500 × 22 = 67 , 320 q_{\text{latent}} = 0.68 \times 4500 \times 22 = 67{,}320 q latent = 0.68 × 4500 × 22 = 67 , 320
Given
Q air Q_{\text{air}} Q air 1,000 L/s Δ w \Delta w Δ w 0.004 kg/kg q latent = 3 × 1000 × 0.004 = 12 q_{\text{latent}} = 3 \times 1000 \times 0.004 = 12 q latent = 3 × 1000 × 0.004 = 12
Symbols and units
Symbol Meaning Unit
q latent q_{\text{latent}} q latent latent air heat rate Btu/h C F M \mathrm{CFM} CFM air volume flow cfm Δ gr \Delta \text{gr} Δ gr humidity-ratio change grain/lb
Symbol Meaning Unit
q latent q_{\text{latent}} q latent latent air heat rate kW Q air Q_{\text{air}} Q air air volume flow L/s Δ w \Delta w Δ w humidity-ratio decrease kg/kg
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