A New Concept of Cooling Air in Ship Cogeneration Engines

The low speed diesel engines are the most widespread in marine power plants. Their fuel efficiency falls with growing intake and charge air temperatures. Therefore, cyclic air cooling ensures a sustainable performance of ship engines along the voyage with high fuel efficiency. The absorption chillers of lithium-bromide type (LBCh) are the most widened due to their high efficiency with COP of about 0.7. However, they are complicated and need a special room. The ejector chillers (ECh) consist mostly of heat exchangers which might be placed on the board side and transverse bulkheads in engine room, but their efficiency is considerably less than that of LBCh: COP = 0.2–0.3 depending on the temperatures of heat source, boiling and condensing refrigerant. The cogeneration engines are desired to produce hot water with temperature of about 90 °C. If hot water is applied as a heat source their COP is about 0.2, that inevitable leads to reduced refrigeration capacity and undercooling engine cyclic air. The lack of ECh cooling capacity has been boosted by the heat left from unloaded LBCh. Basing on a such general approach the overall thermal load on air cooling system has been distributed between LBCh and ECh to minimize LBCh sizes. A concept of ship cogeneration engine air cooling by combine LBCh and ECh has been realized by corresponding cooling system scheme solution. The general statements and assumptions of proposed design methodology of combine air cooling systems for diesel engines are introduced.