Heat Exchanger Design Calculator (LMTD Method)
Calculate the Log Mean Temperature Difference (LMTD) for heat exchangers with our precise online tool. Ideal for engineers and students alike.
Temperature Inputs
Supply the inlet and outlet temperatures for the hot and cold streams. The calculator assumes a counterflow exchanger.
Ensure the hot side temperatures are higher than the cold side counterparts. Invalid ordering renders the log mean undefined.
Log Mean Temperature Difference
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°C
Assumes counterflow heat exchange with constant flow rates.
How to Use This Calculator
Enter the hot and cold fluid inlet/outlet temperatures, then press Calculate. The tool computes the two temperature differences and applies the log mean formula to estimate the effective driving force for heat transfer.
Methodology
The calculator follows the standard LMTD approach for counterflow heat exchangers, deriving the average temperature difference from both ends of the shell-and-tube arrangement.
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Glossary of Terms
- Hot Inlet Temperature: hot fluid temperature entering the heat exchanger.
- Hot Outlet Temperature: hot fluid temperature leaving the exchanger.
- Cold Inlet Temperature: cold fluid temperature entering the exchanger.
- Cold Outlet Temperature: cold fluid temperature exiting the exchanger.
- LMTD: Log Mean Temperature Difference between the two streams.
Step-by-Step Example
Take a heat exchanger where the hot fluid enters at 150°C and leaves at 100°C while the cold fluid flows from 50°C to 80°C. The calculator evaluates ΔT₁ = 150 − 80 = 70°C and ΔT₂ = 100 − 50 = 50°C, then computes LMTD ≈ 59.44°C.
Frequently Asked Questions
What is the purpose of the LMTD method?
The LMTD method determines the average temperature difference between two fluids in a heat exchanger, which is essential for calculating heat transfer rates.
Why is LMTD important?
LMTD provides a more accurate representation of the temperature driving force than a simple arithmetic mean.
Can LMTD be applied to all types of heat exchangers?
Yes, the concept is universal; you only need to adjust for flow arrangement if it differs.
What factors affect the LMTD?
The inlet and outlet temperatures of both fluids and the direction of flow impact the LMTD.
How does LMTD differ from arithmetic mean temperature difference?
LMTD accounts for the logarithmic pattern of temperature change, offering a precise driving-force estimate.