1. What is an Air to Water Heat Exchanger Sizing Calculator?

Definition: This calculator determines the required heat transfer area for an air to water heat exchanger based on thermal performance parameters.

Purpose: It helps engineers and HVAC professionals properly size heat exchangers for optimal thermal performance.

2. How Does the Calculator Work?

The calculator uses the fundamental heat exchanger equation:

Where:

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

Explanation: The required heat transfer area is directly proportional to the heat load and inversely proportional to the heat transfer coefficient and temperature difference.

3. Importance of Proper Heat Exchanger Sizing

Details: Correct sizing ensures efficient heat transfer, proper system performance, and avoids oversizing which increases costs or undersizing which reduces effectiveness.

4. Using the Calculator

Tips: Enter the heat transfer rate in watts, overall heat transfer coefficient (default 25 W/m² K for air-water), and LMTD (default 10 K). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical U value for air-water heat exchangers?
A: Typically ranges from 10-50 W/m² K depending on design, with 25 W/m² K being a common average value.

Q2: How do I calculate LMTD?
A: LMTD = [(ΔT1 - ΔT2)/ln(ΔT1/ΔT2)] where ΔT1 and ΔT2 are temperature differences at each end of the exchanger.

Q3: What affects the U value?
A: Flow rates, materials, fouling factors, and heat exchanger design (plate, shell-and-tube, etc.) all influence U.

Q4: Should I include a safety factor?
A: Yes, typically add 10-20% to the calculated area to account for fouling and uncertainties.

Q5: Can this be used for other heat exchanger types?
A: The formula is universal, but U values differ significantly for different fluids and designs.