Calculator Inputs
Example Data Table
| Case | Hot In | Hot Out | Cold In | Cold Out | U Value | Tube Length | Use |
|---|---|---|---|---|---|---|---|
| Water cooler | 120 °C | 80 °C | 30 °C | 65 °C | 650 W/m²·K | 5 m | Initial sizing |
| Oil heater | 180 °C | 130 °C | 45 °C | 95 °C | 320 W/m²·K | 6 m | Area check |
| Process condenser | 95 °C | 70 °C | 25 °C | 45 °C | 900 W/m²·K | 4.8 m | Tube estimate |
Formula Used
Heat duty from hot stream:
Qh = mh × Cph × (Thi − Tho)
Heat duty from cold stream:
Qc = mc × Cpc × (Tco − Tci)
Average design heat duty:
Q = (Qh + Qc) ÷ 2
Log mean temperature difference:
LMTD = (ΔT1 − ΔT2) ÷ ln(ΔT1 ÷ ΔT2)
Corrected temperature difference:
Corrected LMTD = F × LMTD
Fouled design coefficient:
Udesign = 1 ÷ [(1 ÷ Uclean) + Rf]
Required area:
A = Q ÷ (Udesign × Corrected LMTD)
Tube count:
N = Area ÷ (π × tube outside diameter × tube length)
Tube pressure drop estimate:
ΔP = [f × (L ÷ D) + K] × ρv² ÷ 2
How to Use This Calculator
Enter the hot side flow rate, heat capacity, inlet temperature, and outlet temperature.
Enter the same values for the cold side stream.
Select counter flow or parallel flow.
Add the clean overall heat transfer coefficient.
Enter fouling resistance, LMTD correction factor, and design margin.
Enter tube outside diameter, inside diameter, tube length, and tube passes.
Use installed tube count when checking an existing exchanger.
Leave installed tube count as zero for a new estimate.
Set tube side density and viscosity for velocity and pressure drop checks.
Press calculate. The result appears above the form and below the header.
Shell and Tube Heat Exchanger Sizing Guide
Purpose
A shell and tube heat exchanger transfers heat between two fluids. One fluid flows through tubes. The other fluid flows across those tubes inside a shell. This layout is strong, serviceable, and common in plants. It handles high pressure, high temperature, and large duties well.
Thermal Duty
The first step is the heat duty. Duty depends on mass flow, specific heat, and temperature change. The hot side loses heat. The cold side gains heat. In a perfect balance, both values match. In real estimates, small differences are common. A large difference means one input is wrong, or heat loss needs review.
LMTD Method
This calculator uses the LMTD method. LMTD means log mean temperature difference. It represents the driving force for heat transfer. Counter flow often gives a higher LMTD than parallel flow. A correction factor adjusts the result for real shell and tube paths. Many exchangers use one shell pass and two or more tube passes.
Area and Fouling
The required area depends on duty, design coefficient, and corrected LMTD. A higher coefficient reduces area. Fouling resistance lowers the design coefficient. This is important because deposits grow over time. A design margin adds extra surface. The margin helps cover uncertainty, aging, and small operating changes.
Tube Count
Tube count is based on outside tube area. Longer tubes provide more surface per tube. Larger outside diameter also increases surface. The calculator estimates tube count from the required area. You can also enter an installed tube count. This checks whether an existing exchanger has enough surface.
Velocity and Pressure Drop
Tube side velocity affects heat transfer and pressure drop. Very low velocity may allow fouling. Very high velocity may create erosion or pumping issues. Reynolds number shows the flow regime. Pressure drop is estimated with a simple friction relation. Final design should still use detailed mechanical and thermal standards.
FAQs
1. What does this calculator estimate?
It estimates heat duty, LMTD, corrected LMTD, design area, tube count, velocity, Reynolds number, and tube side pressure drop.
2. What is LMTD?
LMTD is the log mean temperature difference. It represents the average thermal driving force between hot and cold streams.
3. Why is a correction factor used?
A correction factor adjusts ideal LMTD for real shell and tube flow paths. It is usually below one.
4. What does fouling resistance do?
Fouling resistance reduces the effective heat transfer coefficient. It increases the required heat transfer area.
5. Can I check an existing exchanger?
Yes. Enter the installed tube count. The calculator compares installed surface area with required design area.
6. What is a good tube side velocity?
Acceptable velocity depends on fluid, fouling, erosion risk, and design rules. Many liquid services need moderate velocity.
7. Why do hot and cold duties differ?
They differ when flow, heat capacity, or temperature data are inconsistent. Heat losses can also create small differences.
8. Is this enough for final design?
No. Use it for early estimates. Final design needs detailed thermal rating, vibration review, materials, codes, and pressure checks.