Calculator Input Form
Example Data Table
| Case | Duty kW | Hot In/Out C | Cold In/Out C | U W/m2 K | F Factor | Margin % | Approx Area m2 |
|---|---|---|---|---|---|---|---|
| Water cooler | 401 | 90 / 60 | 25 / 45 | 783 | 0.95 | 15 | 14.6 |
| Oil heater | 250 | 130 / 95 | 40 / 75 | 420 | 0.90 | 20 | 24.8 |
| Process condenser | 800 | 110 / 70 | 30 / 55 | 950 | 0.92 | 10 | 25.2 |
Formula Used
Heat duty can be entered directly. It can also be calculated from stream data.
Q = m Cp ΔT
LMTD = (ΔT1 - ΔT2) / ln(ΔT1 / ΔT2)
1 / U = 1 / hi + Rfi + wall / k + Rfo + 1 / ho
Area = Q / (U × F × LMTD)
Design Area = Area × (1 + Margin / 100)
Tube count is estimated from outside tube area. One tube area equals π times diameter times length.
How to Use This Calculator
- Enter known heat duty, or enter complete stream data.
- Select counter flow or parallel flow arrangement.
- Add film coefficients, fouling factors, and wall data.
- Set the LMTD correction factor and design margin.
- Enter tube diameter and length for tube count estimation.
- Press calculate to show results above the form.
- Use CSV or PDF buttons to save calculated results.
Article: Heat Exchanger Size Calculation Guide
Why exchanger size matters
A heat exchanger must transfer enough heat under real process conditions. Undersized equipment misses outlet temperatures. Oversized equipment wastes money, space, and pumping power. This calculator gives a practical first design estimate. It links heat duty, temperature driving force, overall coefficient, correction factor, and margin.
Heat duty comes first
Heat duty is the required thermal load. It is often known from a process balance. It can also be estimated from mass flow, specific heat, and temperature change. The hot stream loses this heat. The cold stream gains it. In a clean balance, both values should be close. Large differences suggest bad data or heat loss.
Temperature driving force
Heat transfer depends on temperature difference. That difference changes along the exchanger length. LMTD gives one useful average driving force. Counter flow usually gives a stronger driving force than parallel flow. The correction factor adjusts LMTD for multipass or crossflow designs. Use vendor charts or standards for final values.
Overall coefficient and fouling
The overall coefficient combines film resistance, wall resistance, and fouling resistance. High film coefficients reduce required area. Fouling increases resistance and increases required area. Wall thickness and wall conductivity also affect performance. A conservative fouling allowance helps maintain duty between cleaning cycles.
Area and tube estimate
Required area equals duty divided by corrected heat transfer rate. The design area adds margin for uncertainty. This margin covers aging, minor data error, and operating variation. Tube count is estimated from outside tube surface. Real exchangers also need pressure drop checks, vibration review, layout limits, nozzle sizing, and mechanical design.
Best practice
Treat this result as a screening calculation. Confirm properties at mean temperatures. Verify units before using results. Compare hot and cold duty values. Review velocity and pressure limits. Final equipment should be checked by a qualified engineer.
FAQs
What does this heat exchanger calculator estimate?
It estimates heat duty, LMTD, corrected LMTD, overall coefficient, required surface area, design area, heat flux, and tube count from entered process data.
Can I enter known duty directly?
Yes. Enter known duty in kW. The calculator will use it first. Stream data remains useful for LMTD and balance checking.
What is LMTD?
LMTD means logarithmic mean temperature difference. It represents the average temperature driving force between hot and cold streams.
Why is a correction factor needed?
The correction factor adjusts ideal LMTD for real exchanger arrangements, such as multipass shell and tube designs or crossflow designs.
What does fouling resistance do?
Fouling resistance lowers thermal performance. It increases total resistance, reduces the U value, and increases required exchanger surface area.
Is the tube count final?
No. Tube count is an estimate based on surface area. Final selection also needs pressure drop, layout, bundle limits, and mechanical review.
Should I use counter flow or parallel flow?
Use the arrangement matching your exchanger. Counter flow often gives better temperature driving force and smaller required area than parallel flow.
Can this replace detailed engineering design?
No. It supports early sizing only. Final exchanger design should include pressure, vibration, materials, codes, fouling, and safety checks.