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# Fans - Calculate Air and Brake Horsepower

### Air Horse Power - AHP

Assuming 100% efficiency AHP is the power required to move a given air volume against a given pressure. AHP can be expressed as

P AHP = q dp inWG SG / 6356                                 (1)

where

P AHP =  Air Horse Power (hp)

q = air flow (cfm)

SG = Specific Gravity Air (= 1.0)

dp inWG = total pressure (in. W.G)

### Brake Horse Power - BHP

• Brake horsepower is the actual power delivered to or by a shaft.

The actual power - brake horse power - a fan requires, because no fan is 100% efficient, can be expressed as

P BHP = q dp inWG / μ 6356                                   (2)

where

P BHP =  Brake Horse Power (hp)

μ = fan efficiency

## Related Topics

### • Ventilation Systems

Design of systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more.

## Related Documents

### Fan Affinity Laws

The affinity laws can be used to calculate resulting volume capacity, head or power consumption when speed or wheel diameters are changed.

### Fan AMCA Classification

Fan classification established by AMCA.

### Fans - Efficiency and Power Consumption

Power consumption and typical efficiencies of fans

### Fans - Volume Flow, Pressure Head and Power Consumption vs. Air Temperature and Density

The temperature and density of the air influences on the volume flow, pressure head and power consumption in a fan.

### Pumps - Specific Speed

Characterizing of impeller types in pumps in a unique and coherent manner.

### Types of Fans

Axial and propeller fans, centrifugal (radial) fans, mixed flow fans and cross flow fans.

### Types of Fans - Capacity Ranges

Centrifugal, axial and propeller fans and their capacity ranges.

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