Calculator Inputs
Use the responsive grid below. Large screens show three columns, medium screens show two, and small screens show one.
Performance Plot
The plot compares inlet and outlet temperatures for the hot and cold streams.
Example Data Table
| Case | Hot Inlet | Hot Outlet | Cold Inlet | Cold Outlet | Mass Flow Hot | Mass Flow Cold | Estimated Duty |
|---|---|---|---|---|---|---|---|
| Water to Water Service | 120 °C | 80 °C | 30 °C | 65 °C | 2.5 kg/s | 3.0 kg/s | 418 kW |
| Oil Cooler | 160 °C | 110 °C | 28 °C | 55 °C | 1.8 kg/s | 4.1 kg/s | 225 kW |
| Process Heat Recovery | 210 °C | 145 °C | 40 °C | 98 °C | 2.2 kg/s | 2.9 kg/s | 360 kW |
Formula Used
Q = m × Cp × ΔT
Qmax = Cmin × (Th,in − Tc,in)
ε = Q / Qmax
Q = U × A × LMTD
LMTD = (ΔT1 − ΔT2) / ln(ΔT1 / ΔT2)
Here, m is mass flow rate, Cp is specific heat, ΔT is stream temperature change, U is overall heat transfer coefficient, A is area, and LMTD captures the exchanger driving force.
How to Use This Calculator
- Select SI or Imperial units.
- Choose whether you want to calculate from temperatures, UA and effectiveness, or known duty.
- Enter hot-side flow, heat capacity, and inlet temperature values.
- Enter cold-side flow, heat capacity, and inlet temperature values.
- Provide outlet temperatures, or enter U, area, effectiveness, or known heat duty, depending on your selected mode.
- Press the calculate button to generate load and thermal performance results.
- Review the summary cards and graph shown above the form.
- Download CSV or PDF output for reporting or review.
Frequently Asked Questions
1. What does heat exchanger load mean?
Heat exchanger load is the thermal energy transferred between two fluids per unit time. It is commonly called heat duty and is usually reported in kW or Btu/h.
2. Why can hot-side and cold-side duty differ slightly?
Small differences can appear from rounding, estimated properties, sensor drift, or inconsistent unit entry. In real systems, heat loss and fouling can also create imbalance.
3. When should I use the UA method?
Use the UA method when you know the exchanger conductance and transfer area, or when sizing performance from effectiveness and available driving temperature difference.
4. What is LMTD used for?
LMTD measures the average temperature driving force across the exchanger. It is used with U and A to estimate duty for steady-state thermal design cases.
5. How does fouling affect performance?
Fouling adds thermal resistance, lowers the effective overall coefficient, and reduces heat transfer. That usually means lower duty, larger required area, or higher energy consumption.
6. Can this calculator help during early design?
Yes. It is useful for feasibility checks, preliminary sizing, and performance comparisons. Final design should still use validated properties, pressure-drop checks, and detailed standards.
7. Which exchanger type gives better thermal performance?
Counter-flow arrangements usually provide a stronger average temperature driving force than parallel flow. That often improves effectiveness for the same area and operating conditions.
8. Does this replace detailed process simulation?
No. This calculator is intended for engineering estimation and quick review. Complex phase change, variable properties, and transient behavior need more advanced modeling.