Mist/Steam Cooling in a Heated Horizontal Tube—Part 1: Experimental System

Abstract

To improve the airfoil cooling significantly for the future generation of advanced turbine systems (ATS), a fundamental experimental program has been developed to study the heat transfer mechanisms of mist/steam cooling under highly superheated wall temperatures. The mist/steam mixture was obtained by blending fine water droplets (3∼15 μm in diameter) with the saturated steam at 1.5 bars. Two mist generation systems were tested by using the pressure atomizer and the steam-assisted pneumatic atomizer, respectively. The test section, heated directly by a DC power supply, consisted of a thin-walled (∼0.9 mm), circular stainless steel tube with an ID of 20 mm and a length of 203 mm. Droplet size and distribution were measured by a phase Doppler particle analyzer (PDPA) system through view ports grafted at the inlet and the outlet of the test section. Mist transportation and droplet dynamics were studied in addition to the heat transfer measurements. The experiment was conducted with steam Reynolds numbers ranging from 10,000 to 35,000, wall superheat up to 300°C, and droplet mass ratios ranging from 1∼6 percent. [S0889-504X(00)02402-8]