EXPERIMENTAL RESULTS ON HUMIDIFICATION OF COMPRESSED AIR IN A TUBULAR HUMIDIFIER FOR EVAPORATIVE CYCLES

摘要

The evaporative gas turbine (EvGT), also known as the humid air turbine (HAT) has the potential to compete with diesel engines and combined cycles in small and intermediate sizes. Most EvGT concepts include a packed bed tower for humidification; however, an alternative is a tubular humidifier unit. A tubular humidifier test rig was designed and constructed at the Royal Institute of Technology in Stockholm. A thorough investigation of the humidifier's performance and characteristics at different pressures was conducted in 1998. The humidifier consists of a single vertical surface-extended tube and shell. The water and the compressed air are brought into countercurrent contact inside the tube, resulting in evaporation of the water film in the compressed air. The heat required for the evaporation comes mainly from the exhaust gas cooling on the shell side. Experimental results show that the tubular humidifier operates satisfactorily. The exhaust gas heat is recovered to significantly low temperatures. The temperature and the humidity ratio of the compressed air are promising for EvGT applications. The flooding velocity and the wetting limit were also examined. In most cases an inner tube diameter of approximately 50 mm and a tube length of 9 m are considered suitable for this type of application.