COLD EXERGY, THE CONCEPT AND APPLICATIONS

Abstract

ABSTRACT

The purpose of this work is to contribute to the issue of recovering cold exergy from cold states. Material at temperatures less than atmospheric temperature such as liquefied natural gas (LNG), may possess an abundant amount of so called cold exergy, which is usually not recognized nor recovered during the regasification process. Derna power plant is selected to explore this issue, by utilizing the cold exergy which is possessed by the Liquefied Natural Gas (LNG), here, the gasification process takes place by utilizing the heat energy which is rejected by the condenser of the selected steam power station. Natural gas is compressed and liquefied to lower the specific volume for shipping at extremely low temperatures, around 110K. The latent heat (heat of evaporation) of methane (the major component of the natural gas) at 0.1MPa is 512 kJ/kg. Cold exergy could be recovered by transferring heat from the atmosphere (from seawater for instance) to a heat engine, and rejecting heat to a sink, for instance to the LNG during the evaporation process. The results show that 40.84% of the input physical exergy of the LNG is destroyed during the conventional regasification process. The net power output of the selected steam power plant could be raised by 12.1 % when connected with the regasification cycle.