Abstract
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 Al 2 O 3 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 Al 2 O 3 nanoparticles in the heat exchange equipment of refrigeration systems.
Highlights
IntroductionIntensification of the heat exchange process in different thermal power systems is an important task, since it contributes to the rational utilization of energy resources, as well as to the reduction in material consumption of heat exchange equipment.One of the most promising ways of the heat exchange intensification, not requiring design changes in the equipment, is the use of nanofluids, obtained on the basis of traditional heat-transfer agents (water, mineral oils, ethylene glycol and other), instead of these agents
Intensification of the heat exchange process in different thermal power systems is an important task, since it contributes to the rational utilization of energy resources, as well as to the reduction in material consumption of heat exchange equipment.One of the most promising ways of the heat exchange intensification, not requiring design changes in the equipment, is the use of nanofluids, obtained on the basis of traditional heat-transfer agents, instead of these agents
A schematic of the original experimental installation to study the processes of heat exchange and hydrodynamics under the forced flow of nanofluids was devised; the calibration experiment was performed using distilled water as coolant, which demonstrated reliability of the obtained experimental data
Summary
Intensification of the heat exchange process in different thermal power systems is an important task, since it contributes to the rational utilization of energy resources, as well as to the reduction in material consumption of heat exchange equipment.One of the most promising ways of the heat exchange intensification, not requiring design changes in the equipment, is the use of nanofluids, obtained on the basis of traditional heat-transfer agents (water, mineral oils, ethylene glycol and other), instead of these agents. The major advantage of the application of nanofluids as heat-transfer agents is in the fact that they have the higher value of thermal conductivity in comparison with the basic liquid For this reason, nanofluids are promising heat-transfer agents for the heat exchange equipment under laminar conditions of the liquid motion [1,2,3,4,5]. The detailed, physically substantiated ideas about the mechanism of the heat transfer intensification with the participation of nanofluids have not been sufficiently developed so far For this reason, additional experimental studies, directed toward studying the influence of nanoparticles on the heat transfer intensity at the forced motion of nanofluids in the pipes and channels, are necessary
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