Studying the Thermal-Hydraulic Efficiency of High-Temperature Cooling Systems for Marine Diesel Engines

Abstract

One of the perspective directions of improving diesels used as the main and auxiliary engines in the ship power plants composition is increasing the temperature level providing heat losses reduction, increase of engines thermal efficiency and their fuel economy. To implement this direction, many modern diesels are equipped with hightemperature cooling systems. Increasing the coolant temperature in such systems is accompanied by increasing the pressure in the cooling systems. Increasing pressure in the cooling systems leads to increasing the power consumption required to drive the circulation pump of the internal circuit of the diesel cooling system. The research purpose is a comparative assessment of the thermal-hydraulic efficiency of high-temperature and low-temperature cooling. As an evaluation criterion, the ratio of heat withdrawn through the cooling system and the power consumption for pumping the coolant, which provides this heat removal, is used. To determine this ratio, both known analytical dependencies and the results of numerical simulation of heat transfer processes in a cylindrical channel are used during the research. The use of both research methods allows us to obtain consistent results. Based on the conducted research results, it can be concluded that despite increasing the power costs for the circulation pump drive, the transition to high-temperature cooling provides an increase of the thermal-hydraulic efficiency of the ship diesel cooling systems. The most significant increasing the thermal-hydraulic efficiency of high-temperature cooling systems is possible when using water-water heat exchangers that provide the maximum permissible temperature difference of the coolant at the engine outlet and inlet.