In the energy equation, what is the sign convention for elevation z and head losses?

• A. Elevation z decreases with height; head losses add to the energy term.
• B. Elevation z increases with height; head losses add to the energy losses along the path and are represented on the loss side of the equation.
• C. Elevation z is constant; head losses are on the energy side.
• D. Elevation z is negative; head losses cancel with elevation.

Answer: (B)

In the energy equation, elevation z reflects gravitational potential energy and increases as you go higher, so the z term increases with height. Head losses represent energy dissipated due to friction and fittings along the flow path, so they reduce the available energy and are placed on the loss side of the equation. The usual form is p/γ + z + v^2/(2g) = p/γ + z + v^2/(2g) + h_L, showing that losses appear as an energy drop to be overcome along the path. Therefore, elevation increases with height, and head losses add to the energy losses on the loss side.