Flow Factor (Kv) and Flow Coefficient (Cv)

The flow coefficient - C_v - and the flow factor - K_v - are commonly used to specify the capacity of control valves.

Flow Coefficient - C_v

It is often convenient to express the capacities and flow characteristics of control valves in terms of the

• Flow Coefficient - C_v

The flow coefficient - C_v - is based on the imperial units system and is defined as:

• the flow of water through a valve at 60 ^oF in US gallon/minute at a pressure drop of 1 lb/in²

The flow coefficient is commonly used in the U.S.

Flow Factor - K_v

The metric equivalent of the flow coefficient - C_v - is based on the SI-system and is called the

• Flow Factor - K_v

The flow factor - K_v - is defined as

• the flow of water with temperature ranging 5 - 30 ^oC through a valve in cubic meters per hour (m³/h) with a pressure drop of 1 bar

The flow factor is commonly used outside U.S.

Converting between Flow Coefficient C_v and Flow Factor K_v

The relationship between C_v and K_v can be expressed as:

• C_v = 1.16 K_v         (1)
• K_v = 0.853 C_v         (2)