Evaluation of the ventilation system in an LNG cargo tank construction platform (CTCP) by the AHP-entropy weight method

Owing to the vulnerability of Invar to moisture in the membranes of LNG tanker cargo tank construction platforms (CTCPs), an energy-efficient ventilation system is needed to maintain a suitable thermal-moisture environment and a healthy workplace. However, the optimal distribution of supply and return devices that would guarantee worker satisfaction, air quality, and energy efficiency is unclear. Therefore, we conducted numerical simulations to determine the worker satisfaction indices (temperature, relative humidity, and carbon monoxide concentration satisfactions), air quality index (contaminant-removal efficiency), and energy efficiency index (heat-removal efficiency) with supply vane angles ranging from -75° to 0° and two return vent positions (the bottom return vent and the top return vent). The analytic hierarchy process (AHP) entropy weight method was employed to determine the optimal supply vane angle and return vent position for three design targets by considering these indices simultaneously. The results indicated that, with a supply angle of -45° and a bottom return vent, worker satisfaction and air quality were prioritized. Furthermore, a high energy performance of the ventilation system was achieved with a -15° supply angle and a bottom return vent. Moreover, a comprehensive graph of supply vane angles at both return heights, which could provide a reference for optimizing the ventilation system in LNG-CTCPs, is described.