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For heat transfer intensification in the cooling systems of forced and perspective ship internal combustion engines, the coolants with an increased thermal conductivity are created, which are stable two-phase suspensions based on an aqueous solute of ethylene glycol and solid multigraphene nanoparticles with a high thermal conductivity. Numerical and experimental studies of heat transfer from the heated wall of the test section to nanofluids in the range of mass concentrations of multigraphene particles from 0.2 to 0.75 percent are carried out, which corresponds to the thermal conductivity coefficients from 0,715 to 0,85 W / m·K. The developed experimental facility operating under stationary heat exchange conditions is used to measure the temperature of fluid and the section metal wall at the constant values of such parameters that are found in the engine cooling systems: the heated wall washing circuit, design features of the cooling cavity, artificial turbulization of the fluid flow, etc. The heat transfer coefficients from the heated wall to the base fluid and to the two-phase coolant with its increased thermal conductivity coefficient are compared under identical operation conditions of the test: the coolant temperature is 80 degrees Celsius and its speed of 0,4...1,2 m /s. The influence of the increased thermal conductivity of coolants with multigraphene particles on heat transfer is established. At the same speed of the coolant with an increase in the thermal conductivity of nanofluid from 0,715 to 0,85 W / m·K, the heat transfer coefficient increases by 22 percent. The presence of multigraphene nanoparticles in a suspension with a thermal conductivity of 0.85 W / m·K results to increase in of heat transfer intensity by 30 percent compared with the base fluid. The obtained experimental results are processed in the similarity numbers, which made it possible to obtain the criterial equation for heat transfer under forced convection and the turbulent flow regime of “liquid-solid particles” suspensions. This equation can be the basis for calculating heat transfer in the cooling systems of internal combustion engines when using such two-phase coolants with an increased thermal conductivity. The task of increasing the heat exchange intensity at the boundary between the wall and coolant is relevant both to increase the forced marine diesel engines reliability and to improve the thermal and hydraulic efficiency of heat exchangers associated with the cooling circuit of marine engines.

vestnik gosudarstvennogo universiteta morskogo i rečnogo flota imeni admirala s. o. makarova/vestnik gosudarstvennogo universiteta morskogo i rečnogo flota imeni admirala s.o. makarova

HEAT TRANSFER IN THE COOLING SYSTEMS OF SHIP ENGINES WHEN CIRCULATING THE COOLANT CONTAINING MULTIGRAPHENE NANOPARTICLES WITH HIGH THERMAL CONDUCTIVITY