SEPARATING AND THROTTLING CALORIMETER

A pure separating calorimeter suffers from a disadvantage that the steam passing out after water separation may not be completely dry or it may have higher dryness faction. Only in throttling calorimeter a high dryness fraction (93%) can be found. Thus, a combined separating and throttling calorimeter may be used to measure the dryness fraction of steam. The sample steam is first passed through separating calorimeter, where most of the moisture is separated and measured and then the drier steam is passed into the throttling calorimeter. A schematic diagram of separating and throttling calorimeter is shown in Figure 4.8.

Figure 4.8 Separating and Throttling Calorimeter

Example 4.11: Following data were obtained on combined separating and throttling calorimeter: Pressure of steam sample = 20 bar, pressure of steam at exit = 1 bar, temperature of steam at the exit = 160°C, discharge from separating calorimeter = 1 kg/min, discharge from throttling calorimeter = 15 kg/min. Determine the dryness fraction of the sample steam.

Solution:

Pressure of sample steam, P₁ = P₂ =120 bar, pressure at the exit, P₃ = 1 bar, temperature of steam at the exit, t_sup3 = 180°C, discharge from separating calorimeter, m = 1 kg/min, discharge of dry steam from throttling calorimeter, M = 15 kg/min.