Abstract
The practical implementation of ocean thermal energy conversion technology faces constraints due to the low temperature differentials, resulting in limited energy conversion efficiency. This research introduces a novel combined power-refrigeration cycle that utilizes a hybrid liquid-gas-gas ejector to amplify the conversion efficiency. The gas extracted from the turbine is employed as auxiliary fluid within the liquid-gas-gas nozzle, effectively countering the low ejection coefficient associated with conventional liquid-gas ejectors. To elucidate the mechanism behind the liquid-gas-gas ejection process involving an ammonia-water-based absorption working fluid, a comprehensive fluid flow model for ejector is developed. This model facilitates the clarification of the non-equilibrium phase transition process occurring within the ejector. Parametric analysis was conducted to assess cycle performance under various operating conditions. The results show the innovative cycle can attain power/refrigeration efficiencies of 1.58 %/17.45 % while maintaining a refrigeration temperature of −18 °C. Performance comparisons indicate that the proposed liquid-gas-gas ejector based cycle reduces the minimum refrigeration temperature by 20.5 % in contrast to the cycle employing only the liquid-gas ejector, all while preserving power output. Furthermore, despite a mere 26 °C temperature difference, the refrigeration capacity of this cycle significantly outperforms those operating at greater temperature differentials. These findings demonstrate a substantial enhancement in the refrigeration and power capabilities of ocean thermal energy conversion.