Heat Exchanger Size Calculation

Heat Exchanger Equation:

\[ A = \frac{Q}{U \times LMTD} \]

Heat Transfer Rate (Q):

Overall Heat Transfer Coefficient (U):

W/m² K

Log Mean Temperature Difference (LMTD):

Heat Exchanger Area (A):

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1. What is the Heat Exchanger Size Equation?

The heat exchanger size equation calculates the required heat transfer area based on the heat transfer rate, overall heat transfer coefficient, and log mean temperature difference. It is fundamental in thermal engineering for designing efficient heat exchange systems.

2. How Does the Calculator Work?

The calculator uses the heat exchanger equation:

\[ A = \frac{Q}{U \times LMTD} \]

Where:

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

Explanation: The equation determines the necessary surface area for heat transfer based on thermal performance parameters.

3. Importance of Heat Exchanger Area Calculation

Details: Accurate area calculation is crucial for designing cost-effective and energy-efficient heat exchangers, ensuring they meet thermal requirements without being oversized or undersized.

4. Using the Calculator

Tips: Enter heat transfer rate in watts, overall heat transfer coefficient in W/m² K, and LMTD in kelvin. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What factors affect the overall heat transfer coefficient?
A: Material properties, fluid velocities, fouling factors, and heat exchanger design all influence the U-value.

Q2: How is LMTD calculated for different flow arrangements?
A: LMTD formulas vary for parallel flow, counterflow, and crossflow configurations, with counterflow typically providing the highest temperature difference.

Q3: What are typical U values for common heat exchangers?
A: U values range from 10-100 W/m² K for gas-gas exchangers to 500-2000 W/m² K for liquid-liquid exchangers.

Q4: When should correction factors be applied to LMTD?
A: For multi-pass or crossflow heat exchangers, correction factors are needed to account for deviations from pure counterflow conditions.

Q5: How does fouling affect heat exchanger sizing?
A: Fouling reduces heat transfer efficiency, requiring larger surface areas to compensate for the added thermal resistance.