Ventilation Fitting Pressure Loss Coefficients

In summary, for the most accurate results, it is recommended to use the closest combination of diameters and flowratios from the ASHRAE tables for fitting loss coefficients.
  • #1
chrisbolivia
3
0
Good morning,
I'm calculating the pressure loss of a ventilation system for pot-off gas of an aluminum smelter using ASHRAE tables for fitting loss coefficients. The problem is that for much of the ducting, the diameters and flowrate ratios I have do not exist in the tables. (We're talking about Converging Tees, 90deg, 60" with 10" branches, 19m/s)

Should I approximate the fitting loss coefficient using the closest combination of diameters and flowratios in the tables? even though my diameters and flow ratios are very very different from the closest?

Thank you,
 
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  • #2
It is possible to approximate the fitting loss coefficient in this case, however it may not be the most accurate way of determining the pressure loss. It is best to use the closest combination of diameters and flowratios available in the ASHRAE tables. If you have access to more detailed tables or software for calculating pressure losses in ventilation systems, you could use those tools to get a more accurate estimation of the pressure loss.
 

FAQ: Ventilation Fitting Pressure Loss Coefficients

1. What is a ventilation fitting pressure loss coefficient?

A ventilation fitting pressure loss coefficient, also known as a K-factor, is a numerical value that represents the amount of pressure loss that occurs as air flows through a ventilation system fitting, such as a bend, elbow, or tee. It is a crucial factor in determining the overall pressure drop and air flow in a ventilation system.

2. How is the pressure loss coefficient calculated?

The pressure loss coefficient is calculated by conducting experiments and measuring the pressure drop across a fitting at different air flow rates. The results are then used to calculate the K-factor using a formula, which takes into account the shape and size of the fitting.

3. What factors affect the pressure loss coefficient?

The pressure loss coefficient can be affected by a variety of factors, including the shape and size of the fitting, the type of material the fitting is made of, the air flow rate, and the smoothness of the fitting's interior surface. The K-factor may also vary depending on the type of air flow (laminar or turbulent) and the orientation of the fitting.

4. Why is the pressure loss coefficient important in ventilation design?

The pressure loss coefficient is an important factor in ventilation design because it helps determine the overall pressure drop and air flow in a system. By knowing the K-factor of each fitting, engineers can accurately calculate the total pressure loss and select the appropriate fan and duct sizes to achieve the desired air flow rate and pressure requirements.

5. How can the pressure loss coefficient be reduced?

The pressure loss coefficient can be reduced by selecting fittings with lower K-factors, using smoother materials for the fittings, and minimizing the number of fittings in the ventilation system. Properly sizing and designing the system can also help reduce the overall pressure loss. Regular maintenance and cleaning of fittings can also help maintain their smoothness and reduce pressure loss.

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