Heat Exchanger Calculator

Heat Exchanger Equation:

\[ Q = U \times A \times \Delta T_{lm} \]

Overall Heat Transfer Coefficient (U):

W/m²·K

Heat Transfer Area (A):

m²

Temperature Difference 1 (ΔT₁):

Temperature Difference 2 (ΔT₂):

Heat Transfer Rate (Q):

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1. What is the Heat Exchanger Equation?

The heat exchanger equation calculates the rate of heat transfer between two fluids at different temperatures. It's fundamental in thermal engineering for designing and analyzing heat exchangers.

2. How Does the Calculator Work?

The calculator uses the heat exchanger equation:

\[ Q = U \times A \times \Delta T_{lm} \]

Where:

\( Q \) — Heat transfer rate (W)
\( U \) — Overall heat transfer coefficient (W/m²·K)
\( A \) — Heat transfer area (m²)
\( \Delta T_{lm} \) — Log mean temperature difference (K)

The log mean temperature difference is calculated as: \[ \Delta T_{lm} = \frac{\Delta T_1 - \Delta T_2}{\ln(\Delta T_1 / \Delta T_2)} \]

Explanation: This equation accounts for the varying temperature difference along the length of the heat exchanger.

3. Importance of Heat Transfer Calculation

Details: Accurate heat transfer calculations are essential for designing efficient heat exchangers, estimating energy requirements, and optimizing thermal systems.

4. Using the Calculator

Tips: Enter all values in consistent units. The temperature differences (ΔT₁ and ΔT₂) should be the hot and cold end temperature differences of the heat exchanger.

5. Frequently Asked Questions (FAQ)

Q1: What is the log mean temperature difference?
A: It's an average temperature difference between the hot and cold fluids that accounts for the changing temperature difference along the heat exchanger length.

Q2: What are typical U values for different heat exchangers?
A: U values range from 10-100 W/m²·K for gas-gas, 100-1000 for liquid-liquid, and 1000-10000 for phase-change systems.

Q3: When is the arithmetic mean temperature difference acceptable?
A: When the temperature differences at both ends are within 50% of each other (ΔT₁/ΔT₂ between 0.5 and 2).

Q4: What affects the overall heat transfer coefficient?
A: Fluid properties, flow rates, heat exchanger geometry, fouling factors, and materials of construction.

Q5: How do you handle counterflow vs parallel flow?
A: The equation is the same, but the temperature differences are calculated differently for each configuration.