Demonstration of a Novel Combined Cooling and Power Gas Turbine with Water Harvesting

Abstract

Experiments are conducted on a novel cooling and power cycle that combines a semi-closed cycle gas turbine called the High Pressure Regenerative Turbine Engine (HPRTE) with a vapor compression refrigeration system. A fraction of the exhaust air from the combustor is recirculated back to the combustor. The recirculated air is first cooled in a heat exchanger before it is passed on to the evaporator of the vapor compression refrigeration system. The evaporator further cools the recirculated air and in this process water is condensed on the surface of the evaporator tubes. A one-ton refrigeration system was used in the experiment. A total of 1.3 liters of water was extracted for about 20 liters of fuel consumed. In the future, the vapor compression refrigeration system will be replaced with a vapor absorption refrigeration system (VARS). The generator of the VARS will first cool the recirculated air before it passes to the heat exchanger and the evaporator. The evaporator of the VARS will then provide extra cooling in addition to that required for water extraction. The cycle is also modeled using traditional one-dimensional steady-state thermodynamics, with the actual values of the efficiency and pressure drops for the turbomachinery and heat exchangers. The mixture properties of air account for the water removal rate in the evaporator. The values of temperatures and pressure at different state points obtained from the computer model are compared with the experimental values. The difference between the values is found to be within the acceptable limits. The model is then used to design the evaporator capacity for a given amount of water extraction. The evaporator should cool the recirculated gases to about 5 o C to extract about one kg of water per kg of fuel consumed with the current experimental set up. In such a case, about 35 % of the total water vapor generated in the combustor will be extracted in the evaporator.