Result
Preliminary calculation: This tool is for quick sizing and information. In real projects, load calculation, selection and commissioning require engineering calculations and a site survey. Results are approximate values.
Formulas
Q = U × A × LMTDLMTD = (ΔT1 − ΔT2) / ln(ΔT1 / ΔT2)For counterflow, ΔT1 = T_hot,in − T_cold,out and ΔT2 = T_hot,out − T_cold,in. For parallel flow, take ΔT1 = T_hot,in − T_cold,in and ΔT2 = T_hot,out − T_cold,out. If the two differences are equal, LMTD equals that value.
Points to consider in selection
- The smaller the approach temperature (between cold outlet and hot inlet), the faster the area grows
- Fouling resistance lowers the U value
- For plate heat exchangers, pressure loss and gasket material should be checked
- In glycol circuits, the fluid properties are different
Frequently asked questions
What is LMTD?
It is the logarithmic mean of the temperature differences between the two ends of the heat exchanger; it is used to find the heat transfer surface.
Why is counterflow more efficient?
With the same inlet and outlet temperatures, counterflow gives a larger LMTD; that means a smaller area for the same capacity.
Is the calculated area sufficient?
The calculation does not include fouling and pipe/plate details. The manufacturer's software or an engineering calculation is required for selection.