Exergy Analysis of a Liquefied Natural Gas Counter Flow Cooling Tower

Abstract

The energy dissipation occurring in a cooling tower coupled with lack of proper system maintenance results in the cooling tower becoming less effective at heat exchange, leading to performance and efficiency losses. This paper presents the exergy analysis of a liquefied natural gas (LNG) counter flow cooling tower. The purpose of this research work was to identify areas of energy dissipation in the components of the cooling tower with a view to carrying out its optimization. The methodology employed in carrying out this research work involves the collection of relevant data from the Nigeria Liquefied Natural Gas (NLNG) plant in Bonny Island, Rivers State and analysis of the data using formulated exergy equations as it applied to a cooling tower. The results of the analysis reveals that as the wet-bulb temperature increased from 21°C to 30°C, this leads to notable improvements in cooling tower efficiency, with enhancements ranging from 23% to 49%. The results also showed that the cooling tower efficiency increased from 45.94% to 46.39%, 46.06% to 46.63% and 46.19% to 46.8% for mass flow rates of air of 946 kg/s, 1583 kg/s and 2216.2 kg/s respectively, with a matching water inlet temperatures of 39.4°C – 41°C. The results also showed that changing the water flow rate, increases cooling tower efficiency from 25.8% to 28.3%, 34.6% to 37% and 40.4% to 42.2% for water mass flow rates of 3257.1 kg/s, 5428.5 kg/s and 7599.9 kg/s respectively. It is important to carry out exergy analysis of a cooling tower in order to identify areas of energy dissipation and determine how to optimize the various components of the cooling tower through efficient maintenance.

Keywords — Energy dissipation, Optimization, Cooling load, Range, Approach, Wet bulb

temperature, Working fluid, Mass flow rate.