Construction
- Figure shows throttling calorimeter which essentially consists of throttle valve, pressure gauge, thermometer and manometer.
- Through sampling tube steam is taken to throttle valve where steam is throttled from higher pressure to lower pressure.
- Pressure gauge is used to measure pressure before throttling and manometer is used to measure pressure after throttling. Thermometer is used to measure temperature after throttling.
Construction
- With full open steam stop valve, steam is allowed to throttle until steady pressure and temperature is reached. At steady state condition pressure before throttling (p1) and temperature after throttling is to be measured.
Calculation
- As we know that during throttling process enthalpy remains constant. This fact is used to measure dryness fraction of wet steam.
Enthalpy before throttling = Enthalpy after throttling
Where, unknown dryness fraction
Where, enthalpy of saturated liquid at
Where, latent heat of steam at
Where, sensible heat of water at
Where, latent heat of steam at
Where, specific heat of superheated steam assumed
Where, temperature of steam measured by thermometer after throttling
Where, saturation temperature of steam at
Limitations
- This calorimeter is used when the dryness fraction is greater than 0.95.
- To use this calorimeter condition of steam after throttling must be superheated.