Experimental Study of Heat Exchange and Hydrodynamics at the Laminar Flow of Nanocoolant Based on Propylene Glycol and Al2O3 Nanoparticles

An experimental study of heat transfer coefficient and pressure losses coefficient under the laminar flow of nanocoolants in the pipe was carried out. The relevance of the studies is related to the possibility of intensification of the heat transfer process when using nanofluids as heat transfer agents and coolants without modernizing the equipment.As the objects of the study, we used nanocoolants based on aqueous solutions of propylene glycol with the addition of Al2O3 nanoparticles in the amount of 0.53 and 1.03 % by weight. A technology for the preparation of nanocoolants by a two-stage method is described. Results of the aggregate stability of nanoparticles in the coolant are presented. Thermophysical properties of nanocoolants, necessary for evaluating heat-transfer coefficient and coefficient of pressure losses, were estimated experimentally (viscosity and heat capacity) and theoretically (density and thermal conductivity) in temperature range of 253–313 K. A schematic of the original experimental installation for measuring heat-transfer coefficient and pressure losses coefficient in the pipe is represented. Results of the calibration experiment with the use of water as coolant are presented. Experimental values of heat-transfer coefficients and pressure losses coefficient under the forced laminar flow of nanocoolant in the pipe are given. It was shown that the mean lengthwise and local values of heat-transfer coefficients for the nanocoolant are larger than those for the base coolant. At the same time, an increase in heat exchange intensity is not proportional to the concentration of nanoparticles in the coolant. An increase in the losses of head at the addition of nanoparticles to the base coolant was demonstrated.The data obtained showed a possibility in principle to intensiy the heat transfer process under the forced motion of nanocoolant based on the aqueous solutions of propylene glycol and Al2O3 nanoparticles in the heat exchange equipment of refrigeration systems