Adaptable management for cooling cyclic air in ship power plants by heat conversion – Part 1: Downsizing strategy for cogeneration plants

The ship power plants (SPP) are generally based on Diesel engines. Their fuel efficiency is gradually sensible to cyclic air temperatures and drops with their rise. A sustainable performance of ship engines with high fuel efficiency is possible by cooling intake and charge air as two objects in waste heat conversion chillers. The peculiarities of marine engine application are associated with constrained space of machine room. Whereas, the chiller's downsizing leads to inevitable lack of their cooling capacity and incomplete cooling air which results in reduction of fuel saving. The research objective is to develop the heat conversion management adaptable to balanced downsizing and fuel saving strategies due to flexible heat distribution between the chillers of different efficiencies (COP) in response to current thermal loads on engine cyclic air cooling system along the ship routes which enables to foresee a sustainable thermally stabilized and fuel saving operation of SPP. For the first time, such conflicting challenges are satisfied by flexible heat distribution between different chillers in response to intake and charge air cooling needs. The unique of such approach lies in unloading the high efficient but cumbersome chiller (absorption with COP about 0.7 as example) to boost the less efficient but easy to place in machine room ejector chiller (COP of about 0.2). The method of flexible heat distribution to minimize chiller sizes as constraints is realized in methodology based on step-by-step comparing the gap between heat demand and production to minimize shortage in fuel reduction simultaneously. It has been proved that cooling engine air by compact but less efficient ejector chiller (ECh) and high effective but cumbersome lithium bromide absorption chiller (ACh) of reduced capacity and sizes by about 30 % accordingly provides a specific fuel consumption reduced by about 3 %. The loss of route fuel saving by about 10 % is considered as the "cost" for downsizing. These findings have been verified by the calculation results on current and summarized values of the cooling capacities lack, caused by the chiller's downsizing, and fuel saving along the ship route. The novel strategy of heat conversion by combined chillers is especially useful for upgrading the existing engine air cooling system to implement it into the ship machine room. It can be successfully applied for any type of combustion engines and stationary application while space limitation, for instance, mobile autonomous trigeneration plants of container type.