# Throttling calorimeter measures dryness fraction up to:

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Throttling calorimeter measures dryness fraction up to:

1. 0.68
2. 0.98
3. 0.56
4. 0.76

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Correct Answer - Option 2 : 0.98

Explanation:

Throttling Calorimeter:

• It is a vessel with a needle valve fitted on the inlet side.
• The moisture from the wet steam sample is first removed in separating calorimeter so that the dryness of the wet steam sample is increased above 0.95 before the steam sample enters enter into the throttling calorimeter. During this process pressure and the temperature remains constant.
• The steam is throttled through the needle valve and exhausted to the condenser. The state of steam for the separating and throttling calorimeter should be in superheated vapour just after throttling.
• Then only pressure and temperature can be measured by a manometer and thermometer and then using the steam table enthalpy of superheated vapour is determined.
• From the steady flow energy equation, we can find the enthalpy after throttling and dryness fraction.

The Separating calorimeter:

• It consists of two concentric chambers, the inner chamber and the outer chamber, which communicates with each other through an opening at the top.
• As the steam discharges through the metal basket, which has a large number of holes, the water particles due to their heavier momentum get separated from the steam and collect in the chamber.
• The comparatively dry steam in the inner chamber moves up and then down aging through the annular space between the two chambers and enters the Throttling Calorimeter.
• It is a vessel used initially to separate some of the moisture from the steam, to ensure superheat conditions after throttling. The steam is made to change direction suddenly; the moisture droplets, being heavier than the vapour, drop out of suspension and are collected at the bottom of the vessel.