Pressure Drop Across a Nozzle/Orfice Formula |
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| \( p \;=\; \dfrac{ Q^2 \cdot \rho }{ 12,031 \cdot A_c^2 \cdot C^2 } \) | ||
| Symbol | English | Metric |
| \( p \) = Pressure Drop Across a Nozzle or Orifice (psi) | \(lbf\;/\;ft^2\) | - |
| \( Q \) = Circulation Flow Rate (gpm) | \(gal\;/\;min\) | - |
| \( \rho \) (Greek symbol rho) = Fluid Density | \(lbf\;/\;gal\) | |
| \( A_c \) = Nozzle/Orifice Area | \(in^2\) | - |
| \( C \) = Orifice Coefficient | \(dimensionless\) | - |
Pressure drop across a nozzle or orifice comes from the constriction of the flow path. As a fluid flows from a wider area into the narrower opening of a nozzle or orifice, its velocity must increase to maintain a constant mass flow rate. According to Bernoulli's principle, this increase in kinetic energy is accompanied by a decrease in pressure energy. Consequently, the pressure downstream of the constriction is lower than the pressure upstream.
Several factors influence the magnitude of this pressure drop. The geometry of the nozzle or orifice, particularly the size and shape of the opening, plays a crucial role; a smaller opening or a sharper edge will generally result in a larger pressure drop. The flow rate of the fluid is also significant, with higher flow rates leading to greater pressure differences. Furthermore, the physical properties of the fluid, such as its density and viscosity, affect the pressure drop. A more viscous fluid or a denser fluid will experience a larger pressure drop for the same flow rate and geometry.
