Heat Exchanger Input Form
Formula Used
Hot side duty: Q = mh × Cph × (Th,in − Th,out)
Cold side duty: Q = mc × Cpc × (Tc,out − Tc,in)
LMTD: ΔTlm = (ΔT1 − ΔT2) / ln(ΔT1 / ΔT2)
Required area: A = Q × 1000 / (U × F × ΔTlm)
Effectiveness: ε = Q / [Cmin × (Th,in − Tc,in)]
NTU: NTU = U × A / Cmin
Pressure drop estimate: ΔP = f × (L / D) × (ρv² / 2)
How to Use This Calculator
- Select the exchanger flow pattern.
- Enter hot side flow, heat capacity, and temperatures.
- Enter cold side flow, heat capacity, and temperatures.
- Add the overall coefficient, installed area, and correction factor.
- Leave one outlet temperature blank when using a target duty.
- Press the calculate button to show results below the header.
- Use CSV or PDF buttons to save the report.
Example Data Table
| Case |
Flow Pattern |
Hot In/Out |
Cold In/Out |
U |
Area |
Expected Duty |
| Water cooler |
Counterflow |
95 / 65 °C |
25 / 50 °C |
850 W/m²·K |
12 m² |
Near 313 kW |
| Oil heater |
Shell and tube |
160 / 115 °C |
40 / 90 °C |
420 W/m²·K |
28 m² |
Process dependent |
| Air preheater |
Parallel flow |
220 / 140 °C |
30 / 105 °C |
75 W/m²·K |
90 m² |
Low coefficient case |
Heat Exchanger Calculator Guide
A heat exchanger moves thermal energy between two fluids. The fluids may be liquids, gases, or phase changing streams. This calculator supports early design checks, classroom work, and maintenance reviews. It estimates duty, log mean temperature difference, corrected temperature difference, required area, effectiveness, NTU, and balance error.
Why heat exchanger sizing matters
Correct sizing protects process quality and operating cost. A small area can miss the target outlet temperature. A very large area can waste material and space. The tool compares heat gained by the cold stream with heat lost by the hot stream. That comparison helps you spot input mistakes and poor assumptions. It also shows whether the selected area and overall coefficient can deliver the required duty.
Understanding the inputs
Enter mass flow in kilograms per second. Enter specific heat in kilojoules per kilogram kelvin. Temperatures may be entered in Celsius because differences are the same in kelvin. Add the overall heat transfer coefficient in watts per square meter kelvin. Add heat transfer area when you want to check an existing exchanger. Leave a target duty when you want the required area for a planned duty.
Interpreting the results
The calculated duty shows the useful heat transfer rate. LMTD represents the average temperature driving force. The correction factor adjusts ideal counterflow values for real layouts. Required area is based on duty divided by coefficient and corrected LMTD. Effectiveness compares actual duty with the maximum possible duty. NTU compares exchanger size with the weaker heat capacity stream. Balance error should stay low when both outlet temperatures are known.
Practical design notes
Use realistic fouling assumptions before choosing final area. Fouling reduces performance over time. Check pressure drop separately for pumps, fans, and safety limits. Review material compatibility when temperatures or fluids are severe. Shell and tube, plate, double pipe, and finned exchangers can all use the same heat balance ideas. Detailed final design should include standards, vendor data, vibration review, and cleaning access. Record the final inputs with each report. Always confirm assumptions before purchase orders are issued. This makes future reviews easier and reduces repeated troubleshooting. This calculator gives a strong first estimate, but it should not replace engineering judgment or approved design procedures.
FAQs
What does this heat exchanger calculator estimate?
It estimates heat duty, LMTD, corrected LMTD, required area, installed area margin, NTU, effectiveness, capacity rates, outlet temperatures, and a simple pressure drop value.
Can I leave an outlet temperature blank?
Yes. Enter a target duty and leave one outlet temperature blank. The calculator estimates that outlet temperature from mass flow and specific heat.
Which flow pattern should I choose?
Use counterflow for opposite flow directions. Use parallel flow for same direction movement. Use shell and tube corrected when applying a correction factor.
What is LMTD?
LMTD means log mean temperature difference. It represents the average thermal driving force between hot and cold fluids across the exchanger.
Why is correction factor included?
Real exchangers may not behave like ideal counterflow units. The correction factor adjusts LMTD for shell passes, tube passes, and layout effects.
What does effectiveness mean?
Effectiveness compares actual heat transfer with the maximum possible heat transfer. Higher values mean the exchanger uses the available temperature difference better.
Why does heat balance error appear?
The hot side heat loss should match the cold side heat gain. A large error may indicate wrong flow, heat capacity, or temperature data.
Is this enough for final design?
No. Use it for estimates and checks. Final design should include vendor ratings, fluid properties, fouling, pressure limits, materials, vibration, and safety rules.