Fig. 19 indicates certain locations of sampling nozzles from which erroneous results will be obtained, the reasons being obvious from a study of the cuts.
Before taking any calorimeter reading, steam should be allowed to flow through the instrument freely until it is thoroughly heated. The method of using a throttling calorimeter is evident from the description of the instrument given and the principle upon which it works.
[Pg 136]
Babcock & Wilcox Superheater
FOOTNOTES
[19] See Stem Correction, page [80].
SUPERHEATED STEAM
Superheated steam, as already stated, is steam the temperature of which exceeds that of saturated steam at the same pressure. It is produced by the addition of heat to saturated steam which has been removed from contact with the water from which it was generated. The properties of superheated steam approximate those of a perfect gas rather than of a vapor. Saturated steam cannot be superheated when it is in contact with water which is also heated, neither can superheated steam condense without first being reduced to the temperature of saturated steam. Just so long as its temperature is above that of saturated steam at a corresponding pressure it is superheated, and before condensation can take place that superheat must first be lost through radiation or some other means. [Table 24][20] gives such properties of superheated steam for varying pressures as are necessary for use in ordinary engineering practice.