Calculate heat exchanger duty (Q = m·Cp·ΔT) from flow rate and inlet and outlet temperatures with typical Cp for water, glycol or air, or latent duty.

Constant specific heat over the entered temperature range; heating or cooling.

Typical specific heat near room temperature. Choose Custom to enter your fluid’s Cp.

Optional settings

Heat Exchanger Duty Formula

For a single-phase stream, sensible duty is Q̇ = ṁ × Cp × |Tout − Tin| with constant Cp. For phase change, the separate latent-duty equation below applies to the mass flow actually undergoing the transition.

HED = M × LH

Variables:

  • HED is the Heat Exchanger Duty (kW)
  • M is the fluid mass flow rate through the exchanger (kg/s) 
  • LH is the latent heat (kJ/kg) 

For phase-change duty, multiply the phase-changing mass flow by the applicable latent heat. This excludes sensible heating before or after the transition. Use the separate sensible, outlet-temperature or mass-flow modes for single-phase energy balances.

How to Calculate Heat Exchanger Duty?

The following steps describe Phase-change duty mode. Select the relevant solve mode rather than leaving an arbitrary input blank.

  1. First, determine the fluid mass flow rate through the exchanger (kg/s). 
  2. Next, determine the latent heat (kJ/kg). 
  3. Next, gather the formula from above = HED = M * LH.
  4. Finally, calculate the Heat Exchanger Duty.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

fluid mass flow rate through the exchanger (kg/s) = 75

latent heat (kJ/kg) = 100

HED = M * LH = 75 × 100 = 7,500 kW