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Calcimator

Heat Exchanger Duty Calculator

Calculate heat exchanger duty using the Log Mean Temperature Difference (LMTD) method: Q = U × A × ΔTlm for counter-current or parallel flow.

Inputs

Results

LMTD (°C)

72.24

Heat duty (kW)

361.2

Heat duty (BTU/hr)1,232,476
ΔT₁ (°C)80
ΔT₂ (°C)65
Heat duty (W)361,203
Effectiveness NTU1
How to Use This Calculator
  1. Enter Hot fluid inlet temperature (°C), Hot fluid outlet temperature (°C), and Cold fluid inlet temperature (°C).
  2. Set Cold fluid outlet temperature (°C), Overall heat transfer coefficient U (W/m²·K), and Heat transfer area (m²).
  3. Adjust Flow arrangement (0 = counter, 1 = parallel) as needed.
  4. Review LMTD (°C) and Heat duty (kW).
  5. Use Heat duty (BTU/hr) and ΔT₁ (°C) to inform your decision.

How the result changes with Hot fluid inlet temperature (°C)

Hot fluid inlet temperature (°C)LMTD (°C)Heat duty (kW)
557.437.01
318136.66683.32
633230.671,153.37
895299.11,495.48

What each input means

Hot fluid inlet temperature (°C)
Temperature of the hot stream entering the exchanger.
Hot fluid outlet temperature (°C)
Temperature of the hot stream leaving the exchanger.
Cold fluid inlet temperature (°C)
Temperature of the cold stream entering the exchanger.
Cold fluid outlet temperature (°C)
Temperature of the cold stream leaving the exchanger.
Overall heat transfer coefficient U (W/m²·K)
Typical values: water-water 800-1500, steam-water 1000-6000, gas-gas 10-50 W/(m²·K).
Heat transfer area (m²)
Total effective heat transfer surface area.
Flow arrangement (0 = counter, 1 = parallel)
0 for counter-current flow, 1 for parallel (co-current) flow.

What each result means

LMTD (°C)
Log Mean Temperature Difference driving the heat exchange.
Heat duty (kW)
Total heat transfer rate Q = U × A × LMTD.
Heat duty (BTU/hr)
Duty converted to imperial units.
ΔT₁ (°C)
Temperature approach at one end of the exchanger.
ΔT₂ (°C)
Temperature approach at the other end.
Heat duty (W)
Duty in Watts.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Hot fluid inlet temperature (°C) = 150, Hot fluid outlet temperature (°C) = 90, Cold fluid inlet temperature (°C) = 25, Cold fluid outlet temperature (°C) = 70 = 7 input(s) provided
  2. Calculate LMTD
    LMTD
    72.24 = 72.24
  3. Calculate Heat duty
    Heat duty = dutyW / 1000
    361.2 = 361.2
  4. Calculate Heat duty
    Heat duty = dutyW * 3.41214
    1232476 = 1232476
  5. Calculate ΔT₁
    ΔT₁
    80 = 80

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