KEVOS® MAKEOS · Hydraulics
Heat Exchanger Sizing (Duty, Outlet Temperature and Area)
How much heat does this exchanger move, what will the cold stream leave at, and is the installed area enough?
Sizing check of a liquid-to-liquid heat exchanger: duty from the hot stream’s flow, specific heat and temperature drop, the cold stream outlet temperature from the energy balance, the log-mean temperature difference for counterflow or parallel flow (as the heat exchanger LMTD tool), the area needed with your overall coefficient, and checks of the installed area and the closest approach temperature.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Hot stream | ||
| Hot flow | L/min | Volume flow of the hot stream. |
| Hot density | kg/m³ | Density of the hot fluid. |
| Hot specific heat | kJ/kg·K | Specific heat of the hot fluid (about 1.9–2.1 for mineral oil). |
| Hot inlet | °C | Hot stream inlet temperature. |
| Hot outlet | °C | Hot stream outlet temperature wanted. |
| Cold stream | ||
| Cold flow | L/min | Volume flow of the cooling stream. |
| Cold density | kg/m³ | Density of the cold fluid. |
| Cold specific heat | kJ/kg·K | Specific heat of the cold fluid. |
| Cold inlet | °C | Cold stream inlet temperature. |
| Exchanger | ||
| Flow arrangement | choice | Whether the streams run in opposite directions (counterflow) or the same direction. |
| Overall heat transfer coefficient | W/m²·K | Overall heat transfer coefficient for the exchanger type and fluids, including fouling (from the maker or your data). |
| Installed area | m² | Heat transfer area of the exchanger fitted or offered. |
| Closest approach temperature allowed | K | Smallest temperature difference you accept between the streams at either end. |
Method and formulas
- Duty = ṁ_h c_ph (T_hi − T_ho), ṁ = flow × density.
- Cold outlet T_co = T_ci + duty ÷ (ṁ_c c_pc).
- LMTD = (ΔT₁ − ΔT₂) ÷ ln(ΔT₁ ÷ ΔT₂) with the end differences for the flow arrangement (as the LMTD tool).
- Area needed = duty ÷ (U × LMTD).
- Example: cooling 30 L/min from 70 to 50 °C moves 41.8 kW; the water leaves at 35 °C and 3.5161 m² is needed.
Limitations
- Pure counterflow or parallel flow; shell-and-tube with several passes needs an LMTD correction factor.
- Constant specific heats and no phase change.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size an oil or coolant cooler for a machine
- Find the water outlet temperature of a cooler
- Check whether an existing exchanger has enough area
Who it is for
- Plant engineers
- Hydraulic engineers
- Maintenance engineers
What you get
- Duty and cold outlet temperature
- LMTD and area needed
- Area and approach checks
Interpreting the result
- Counterflow needs less area for the same duty and lets the cold outlet exceed the hot outlet.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 371–378. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Heat Exchanger Sizing (Duty, Outlet Temperature and Area) calculator
