Abstract
This paper is a report on studies of heat transfer and pressure drops in steam-generating tubes at pressures from 500 to 3300 psi and under exposure to furnace heat in large steam-generating units. Most of the test surfaces were in the form of flat spirally coiled tubes, but for comparison one straight tube 50 ft long was tested. Specific problems investigated include the influence of variations of the steam-water ratio and of variations in tube dimensions (scale factor) on tube-metal temperatures and on pressure drops. Some data relate to tubes operating under conditions approaching those often associated with operating failures. The test conditions were extended in several instances to include water below the saturation temperature.
Some of the possible engineering analyses of the data have been made. Such an analysis of the relation of metal temperature to heat absorption and internal fluid conditions led to the proposal of a function ϕ which seems to offer some possibilities of development as a function correlating the factors influencing an abnormal rise in metal temperature. Similarly an analysis of the pressure drop has led to the proposal of a modification of the usual pressure-drop correlation to include the thermodynamic effect of transverse-momentum changes during evaporation.
Supplementary investigations reported upon include pressure drop of water at saturation temperature for the pressure range 250 to 2500 psi, through flow-distributing equipment designed for forced-circulation boilers, and heat-transfer coefficients for the specific auxiliary equipment used.
