Latent Heat Flow

Calculate latent heat flow due to moisture in air using English (Imperial) or SI (metric) units. The latent heat flow depends on the latent heat of vaporization, air density, air flow rate, and the difference in humidity ratio between two states.

Parameter	English (Imperial)	SI (Metric)	Description
Formula	Ql = 60 × hwe × ρ × q × Δx	Ql = hwe × ρ × q × Δx / 3600	Latent heat flow calculation
Ql (Output)	Btu/hr	kW	Latent heat flow
hwe	1060 Btu/lb	2454 kJ/kg (at 20°C)	Latent heat of vaporization of water
ρ (Air Density)	0.075 lb/ft³	1.202 kg/m³	Air density at standard conditions
q (Air Flow)	ft³/min	m³/hr	Measured air flow rate
Δx (Humidity Difference)	lbH₂O/lbdry_air	kgH₂O/kgdry_air	Difference in humidity ratio

Calculator

Inputs

Unit System

Latent Heat of Vaporization (hwe) (kJ/kg or Btu/lb)

Air Density (ρ) (kg/m³ or lb/ft³)

Air Flow Rate (q) (m³/hr or ft³/min)

Humidity Ratio Difference (Δx) (kgH₂O/kgdry_air or lbH₂O/lbdry_air)

Results

Latent Heat Flow (Ql)-- kW or Btu/hr