Correct Answer - Option 3 : stagnation
Explanation:
moving blades
- The moving blades move as a result of the impulse of steam (caused by the change of momentum) and also as a result of expansion and acceleration of the steam relative to them.
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In other words, they also act as nozzles.
Stagnation temperature
- The stagnation values are useful reference conditions in a compressible flow.
- The stagnation properties at a point are defined as those which are to be obtained if the local flow were imagined to cease to zero velocity isentropically.
- When a thermometer is used to measure temperature in moving steam in a nozzle, it measures stagnation temperature.
- The stagnation temperature is given numerically as follows
\(\frac {T_o}{T}=1+\frac{\gamma -1 }{2}Ma^2 \)
where To is the stagnation temperature, T is local temperature and Ma is Mach number respectively.
Static temperature
- It is the temperature measured with the sensor travelling at the same velocity as the fluid.
- In other words the temperature with no velocity effects.
Wet-bulb temperature
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It is the temperature read by a thermometer covered in water-soaked cloth over which air is passed.
- At 100% relative humidity, the wet-bulb temperature is equal to the air temperature;
- At lower humidity, the wet-bulb temperature is lower than the dry-bulb temperature because of evaporative cooling.
Dynamic temperature
- It includes the static temperature and dynamic component related to the kinetic energy of the gas.
