Application Of Nanofluids In Engine Cooling System

Cooling system is an important component in internal combustion engine. The working performance of cooling system impacts the power, economy, dependability of combustion engine directly. Nowadays, as the ceaseless development of engine power and the rapid increment of heating load, traditional pure liquid heat-transfer medium couldn't meet the engine cooling requirements in some special work condition. Therefore, choosing higher thermal conductivity and more efficient heat-transfer medium gradually becomes the key of increasing the engine heat dissipating capability. Nanofluids, as a new kind of high thermal conductivity heat-transfer medium, holds a wide application foreground in the field of strengthening heat-transfer. This paper made use of the strengthening heat-transfer character of nanofluids and applied nanofluids to engine cooling system instead of current medium in use. CFD numerical simulation method was employed to analyse the nanofluids application value in engine cooling.In the aspect of nanofluids thermal properties, many researchers have attempted to establish effective theoretical models to predict them recently, especially thermal conductivity model. This paper generalized the strengthening heat-transfer mechanics of nanofluids and the research achievement proposed by researchers in recent years, confirmed the effective models of nanofluids thermal properties, including thermal conductivity model, density model, specific heat model and viscosity coefficient model.This paper chose the cooling system of traditional in-line six-cylinder diesel engine as subject investigated. The whole engine cooling system was executed in three-dimensional numerical simulation. Firstly, the simulation took pure water as heat-transfer medium, analyzed current three-dimensional flow and heat-transfer condition of engine cooling system. Then Cu-water, Al-water, Al₂O₃-water and TiO₂-water nanofluids in 2% concentration were taken as heat-transfer medium of engine cooling system respectively. The simulation results indicated, compared with pure water, nanofluids could evidently enhance the heat dissipating capability of engine, and Cu-water had the best heat-transfer capability. Then Cu-water nanofluids with different concentration(1%～5%) were taken as heat-transfer medium. The simulation results indicated that the enhancement of engine heat dissipating capacity was larger with increasing the concentration of nanoparticles. When the concentration was 5%, the heat dissipating capacity increased by 43.9%. Otherwise, entering Cu nanoparticles into water caused the increment of fluid viscosity and cooling system pump work. When the concentration was 5%, the pump work increased by 6%, comparing with the remarkable enhancement on heat dissipating capacity, it is acceptable.Nanofluids applied in engine cooling system may provide a new effective approach for engine design to meet much higher heating load in future.