Internal Heat Exchanger Calculation

Heat Transfer Equation:

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

Overall Heat Transfer Coefficient (U):

W/m²·K

Heat Transfer Area (A):

m²

Log Mean Temperature Difference (ΔT_lm):

Heat Transfer Rate (Q):

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1. What is Internal Heat Exchanger Calculation?

The Internal Heat Exchanger Calculation determines the heat transfer rate in heat exchangers using the log mean temperature difference method. This fundamental equation is widely used in thermal engineering and HVAC systems design.

2. How Does the Calculator Work?

The calculator uses the heat transfer 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)

Explanation: This equation calculates the rate of heat transfer through a heat exchanger surface, considering the temperature driving force and the thermal properties of the system.

3. Importance of Heat Transfer Rate Calculation

Details: Accurate heat transfer rate calculation is crucial for designing efficient heat exchangers, optimizing energy consumption, and ensuring proper thermal management in various industrial and HVAC applications.

4. Using the Calculator

Tips: Enter the overall heat transfer coefficient in W/m²·K, heat transfer area in m², and log mean temperature difference in K. All values must be positive and valid for accurate results.

5. Frequently Asked Questions (FAQ)

Q1: What is log mean temperature difference (ΔT_lm)?
A: ΔT_lm is the logarithmic average of the temperature difference between the hot and cold fluids at each end of the heat exchanger, providing a more accurate driving force for heat transfer.

Q2: How is overall heat transfer coefficient (U) determined?
A: U depends on the thermal conductivities of the materials, fluid properties, flow conditions, and fouling factors. It's typically obtained from experimental data or correlations.

Q3: What are typical U values for different heat exchangers?
A: U values range from 10-50 W/m²·K for gas-gas systems, 100-1000 W/m²·K for liquid-liquid systems, and up to 5000 W/m²·K for condensation/evaporation systems.

Q4: When is this equation most applicable?
A: This equation works best for steady-state conditions, constant U values, and counter-current or co-current flow arrangements in heat exchangers.

Q5: What are the limitations of this calculation?
A: The method assumes constant physical properties, no phase change, and may not account for complex flow patterns or variable heat transfer coefficients.