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add errata, fix typos

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Akbar Rahman 2023-04-23 19:13:58 +01:00
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uni/mmme/2047_thermodynamics_and_fluid_dynamics/pumps.md
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@ -11,6 +11,16 @@ exercise_sheets: [ ./exercise_sheets/Turbomachinery-problems.pdf]
Turbomachinery are rotating devices that add (pump for liquids; fan, blower, or compressor for gases at <0.02, <1 bar, and > 1 bar respectively) or extract (turbine) energy from a fluid. Turbomachinery are rotating devices that add (pump for liquids; fan, blower, or compressor for gases at <0.02, <1 bar, and > 1 bar respectively) or extract (turbine) energy from a fluid.
# Errata
## Worked Example 3 Diameter Incorrect (lecture slides 42, lecture notes p. 13)
Question specifies 21" diameter, but should be 32" diameter I think??
Solution provided in lecture slides continues to use 21" dia, but measures
from graph as if is 32".
Weird.
# Positive Displacement (PD) Pumps # Positive Displacement (PD) Pumps
- PD pumps force fluid along using volume changes (e.g. bike pumps, the heart) - PD pumps force fluid along using volume changes (e.g. bike pumps, the heart)
@ -112,7 +122,7 @@ This is where cavitation occurs and causes wear on the blade.
The following conditions must be satisfied to prevent cavitation: The following conditions must be satisfied to prevent cavitation:
\begin{equation} \begin{equation}
H_i - \frac{p_v}{\rho g} > \text{NSPSH} H_i - \frac{p_v}{\rho g} > \text{NPSH}
\end{equation} \end{equation}
where $H_i = \frac{p_i}{\rho g} + \frac{v_i^2}{2g}$ is total head at inlet, $p_v$ is saturation where $H_i = \frac{p_i}{\rho g} + \frac{v_i^2}{2g}$ is total head at inlet, $p_v$ is saturation
@ -146,8 +156,8 @@ Pi-theorem allows the following coefficients to be derived:
Therefore it can be expressed that: Therefore it can be expressed that:
\begin{align*} \begin{align*}
C_H &= g_1(C_Q, \text{Re}, \frac{\epsilon}{D} \\ C_H &= g_1\left(C_Q, \text{Re}, \frac{\epsilon}{D}\right) \\
C_P &= g_2(C_Q, \text{Re}, \frac{\epsilon}{D} C_P &= g_2\left(C_Q, \text{Re}, \frac{\epsilon}{D}\right)
\end{align*} \end{align*}
However for pumps it is assumed that Reynolds number and roughness parameter are constant However for pumps it is assumed that Reynolds number and roughness parameter are constant