By-Pass Factor of Heating Coil Calculator

By-Pass Factor Formula:

\[ BPF = \exp\left(-\frac{U \times A_c}{m_{air} \times c}\right) \]

Overall Heat Transfer Coefficient (U):

W/m²·K

Surface Area of Coil (A_c):

m²

Mass of Air (m_air):

Specific Heat Capacity (c):

J/kg·K

By-Pass Factor (BPF):

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1. What is By-Pass Factor?

By-Pass Factor is the inability of a coil to cool or heat the air to its temperature. It represents the fraction of air that passes through the coil without contacting the heat transfer surface.

2. How Does the Calculator Work?

The calculator uses the By-Pass Factor formula:

\[ BPF = \exp\left(-\frac{U \times A_c}{m_{air} \times c}\right) \]

Where:

\( U \) — Overall heat transfer coefficient (W/m²·K)
\( A_c \) — Surface area of coil (m²)
\( m_{air} \) — Mass of air (kg)
\( c \) — Specific heat capacity (J/kg·K)

Explanation: The formula calculates the exponential decay factor based on the ratio of overall heat transfer capability to the thermal capacity of the air flow.

3. Importance of By-Pass Factor Calculation

Details: By-Pass Factor is crucial in HVAC system design as it determines the efficiency of heating and cooling coils. A lower by-pass factor indicates better coil performance and more effective heat transfer.

4. Using the Calculator

Tips: Enter all values in appropriate units. Ensure all inputs are positive numbers. The calculator will compute the By-Pass Factor using the exponential function.

5. Frequently Asked Questions (FAQ)

Q1: What is a good By-Pass Factor value?
A: Lower values (closer to 0) indicate better coil performance. Typical values range from 0.1 to 0.3 for well-designed coils.

Q2: How does By-Pass Factor affect system performance?
A: Higher By-Pass Factor means less effective heat transfer, requiring larger coils or higher flow rates to achieve the same temperature change.

Q3: Can By-Pass Factor be zero?
A: In practice, By-Pass Factor cannot be zero as some air will always bypass the coil surfaces due to flow dynamics and construction limitations.

Q4: How is By-Pass Factor related to coil efficiency?
A: By-Pass Factor is inversely related to coil efficiency. Lower By-Pass Factor indicates higher efficiency in heat transfer.

Q5: What factors affect By-Pass Factor?
A: Coil design, fin spacing, air velocity, and coil surface characteristics all influence the By-Pass Factor.