Calculate Heat Duty Of Heat Exchanger

Heat Transfer Equations:

\[ Q = m \cdot c \cdot \Delta T \] \[ Q = U \cdot A \cdot \Delta T_{lm} \]

Calculation Type:

Mass Flow Rate (m):

kg/s

Specific Heat Capacity (c):

J/kg·K

Temperature Difference (ΔT):

Heat Transfer Duty (Q):

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1. What Is Heat Transfer Duty?

Heat transfer duty (Q) represents the rate of heat energy transferred in a heat exchanger. It quantifies the thermal power exchanged between fluids and is fundamental to heat exchanger design and performance evaluation.

2. Heat Transfer Equations

The calculator uses two primary heat transfer equations:

\[ Q = m \cdot c \cdot \Delta T \] \[ Q = U \cdot A \cdot \Delta T_{lm} \]

Where:

\( Q \) — Heat transfer duty (W)
\( m \) — Mass flow rate (kg/s)
\( c \) — Specific heat capacity (J/kg·K)
\( \Delta T \) — Temperature difference (K)
\( U \) — Overall heat transfer coefficient (W/m²·K)
\( A \) — Heat transfer area (m²)
\( \Delta T_{lm} \) — Log mean temperature difference (K)

Explanation: The first equation calculates heat duty based on fluid properties and temperature change, while the second uses heat exchanger geometry and overall heat transfer characteristics.

3. Importance Of Heat Duty Calculation

Details: Accurate heat duty calculation is essential for proper heat exchanger sizing, energy efficiency analysis, process optimization, and ensuring thermal requirements are met in chemical processes, HVAC systems, and power plants.

4. Using The Calculator

Tips: Select calculation method based on available data. For Q = m·c·ΔT, enter mass flow rate, specific heat capacity, and temperature difference. For Q = U·A·ΔT_lm, enter overall heat transfer coefficient, heat transfer area, and log mean temperature difference.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between the two calculation methods?
A: Q = m·c·ΔT calculates heat duty from fluid properties, while Q = U·A·ΔT_lm calculates it from heat exchanger design parameters. Both should yield similar results for the same system.

Q2: When should I use log mean temperature difference?
A: Use ΔT_lm for counter-current or co-current flow heat exchangers where temperature difference varies along the length. For constant temperature difference, use simple ΔT.

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

Q4: How does specific heat capacity affect heat duty?
A: Higher specific heat capacity means more energy is required to change temperature, resulting in higher heat duty for the same mass flow and temperature difference.

Q5: Can this calculator be used for phase change calculations?
A: This calculator is for sensible heat transfer only. For phase change (evaporation/condensation), latent heat calculations are required in addition to sensible heat.