Head Loss

Head loss, abbreviated as \(h_l\), is a pressure loss due to the resistance of the fluid and obstructions along the way in a pipe.  There are a number of factors that affect head loss such as:

• flow rate
• corrosion and scale deposits
• fittings (bends, elbows, exits, expanders and reducers, tees)
• inside diameter of the pipe
• roughness of the pipe wall
• viscosity of the liquid
• length of the pipe
• straightness of the pipe
• valves

 

Major Head Loss

Major head loss, abbreviated as \(h_{l-major}\), is the pressure drop caused by friction loss.  It does not matter if the pipe is horizontal, vertical or on an incline.

Major Head Loss Formula
\(\large{ h_{l-major} = f \; \frac{l}{d} \; \frac{v^2}{2\;g}  }\)
Symbol	English	Metric
\(\large{ h_{l-major} }\) = major head loss	\(\large{ ft }\)	\(\large{ m }\)
\(\large{ f }\) = friction factor	\(\large{ dimensionless }\)
\(\large{ g }\) = gravitational constant	\(\large{\frac{lbf-ft^2}{lbm^2}}\)	\(\large{\frac{N - m^2}{kg^2}}\)
\(\large{ l }\) = lenght of pipe	\(\large{ ft }\)	\(\large{ m }\)
\(\large{ d }\) = pipe inside diameter	\(\large{ in }\)	\(\large{ mm }\)
\(\large{ v }\) = velocity of flow	\(\large{ \frac{ft}{sec} }\)	\(\large{ \frac{m}{s} }\)

 

Minor Head Loss

Minor head loss, abbreviated as \(h_{l-minor}\), is the pressure drop caused by fittings and valves.

Minor Head Loss Formula
\(\large{ h_{l-minor} = K \; \frac{v^2}{2 \; g}  }\)
Symbol	English	Metric
\(\large{ h_{l-minor} }\) = minor head loss	\(\large{ft}\)	\(\large{m}\)
\(\large{ g }\) = gravitational constant	\(\large{\frac{lbf-ft^2}{lbm^2}}\)	\(\large{\frac{N - m^2}{kg^2}}\)
\(\large{ K }\) = loss coefficient	\(\large{ dimensionless }\)
\(\large{ v }\) = velocity of flow	\(\large{ \frac{ft}{sec} }\)	\(\large{ \frac{m}{s} }\)