| Popis: |
The demand for more accurate values of thermal efficiencies in modern steam power plants, together with the fact that the velocity of steam is often so high that the impact effect upon temperature-measuring instruments can no longer be neglected, has created a need for improved temperature instrumentation. Studies have been made of the performance, in moving air and steam, of various total-temperature-type wells suitable for use in steam at operating conditions. The instruments recommended for such applications, constructed so that the sensing element is surrounded by nearly stagnant steam, have temperature-recovery factors above 0.9, which do not change significantly with either the medium, its temperature, or its pressure. Although additional work remains to be done on reducing their sensitivity to flow direction and pattern, these wells, when installed in straight pipes through which steam is flowing at any velocity up to 725 fps, yield total enthalpies which are accurate to within 1 Btu per lb. |
