Engineering tools · Free to use
Phase Change Latent Heat Rate Calculator
Calculate latent heat rate for isothermal evaporation or condensation using phase-change mass flow and latent heat at the relevant state.
Input parameters
Inputs and calculations stay in this browser.
Result
Positive means heat enters the phase-changing fluid; negative means heat leaves it. This is the latent contribution, not the complete equipment duty.
Equation
Q̇latent = +ṁ hfg (evaporation); Q̇latent = −ṁ hfg (condensation)
ṁ is the mass flow undergoing phase change (kg/s); hfg is the positive latent heat at the corresponding saturation state (kJ/kg). Their product is in kW; direction determines the sign.
Applicability
For isothermal evaporation or condensation at the selected state. The flow is the mass actually changing phase, not an unchecked total flow. The input latent heat must apply to that process; subcooling or superheating sensible heat, heat loss, pressure drop and other energy terms are excluded.
Traceable example
At 100 °C and approximately 101.418 kPa saturation pressure, saturated water has latent heat about 2256.4 kJ/kg. Complete evaporation of 0.1 kg/s absorbs +225.64 kW; complete condensation at the same rate releases −225.64 kW from the fluid. Latent heat varies with saturation state.
For engineering estimates; verify the full energy balance, operating conditions and applicable requirements for design.