High Precision Heat Exchanger Calculator

Heat Transfer Equation:

\[ Q = U \times A \times LMTD \]

Overall Heat Transfer Coefficient (U):

W/m²K

Heat Transfer Area (A):

m²

Log Mean Temperature Difference (LMTD):

Heat Transfer Rate (Q):

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1. What is the Heat Transfer Equation?

The fundamental heat transfer equation (Q = U × A × LMTD) calculates the rate of heat transfer in a heat exchanger. It's essential for designing and analyzing heat exchanger performance in various engineering applications.

2. How Does the Calculator Work?

The calculator uses the heat transfer equation:

\[ Q = U \times A \times LMTD \]

Where:

\( Q \) — Heat transfer rate (W)
\( U \) — Overall heat transfer coefficient (W/m²K)
\( A \) — Heat transfer area (m²)
\( LMTD \) — Log mean temperature difference (K)

Explanation: The equation relates the heat transfer rate to the product of the overall heat transfer coefficient, heat transfer area, and the logarithmic mean temperature difference between the hot and cold fluids.

3. Importance of Heat Transfer Calculation

Details: Accurate heat transfer calculations are crucial for designing efficient heat exchangers, optimizing energy usage, and ensuring proper sizing of heat exchange equipment in chemical plants, power stations, HVAC systems, and other industrial applications.

4. Using the Calculator

Tips: Enter the overall heat transfer coefficient in W/m²K, heat transfer area in m², and LMTD in Kelvin. All values must be positive numbers for valid results.

5. Frequently Asked Questions (FAQ)

Q1: What is LMTD and how is it calculated?
A: LMTD (Log Mean Temperature Difference) is the logarithmic average of the temperature difference between the hot and cold fluids at each end of the heat exchanger. For counter-current flow: \( LMTD = \frac{(ΔT_1 - ΔT_2)}{\ln(ΔT_1/ΔT_2)} \).

Q2: What are typical U values for different heat exchangers?
A: U values vary widely: 25-250 W/m²K for gas-gas, 50-500 for liquid-gas, 300-1000 for liquid-liquid, and 2000-6000 for condensing/evaporating fluids.

Q3: When is the LMTD method not applicable?
A: LMTD method is less accurate when there's significant variation in U along the exchanger or for complex flow arrangements. The ε-NTU method may be better in such cases.

Q4: How does fouling affect heat transfer?
A: Fouling creates additional thermal resistance, reducing the overall heat transfer coefficient. Design typically includes fouling factors to account for this.

Q5: What's the difference between counter-current and co-current flow?
A: In counter-current flow, fluids enter at opposite ends, producing higher LMTD values and more efficient heat transfer than co-current flow where fluids enter at the same end.