Application peculiarities of the high-temperature fluids containing nanoparticles in gas-tube boilers

Abstract

The paper considers the application peculiarities of the high-temperature fluids containing nanoparticles in gas-tube boilers. The classification of nanofluids obtaining methods is presented, one-step and two-stepmethods for preparing the product are considered. The main thermophysical properties of materials are described. The values of the thermal conductivity coefficient for some materials that are usually used as the base ones for mixing liquids and nanoparticles are represented. The mechanisms of heat transfer in nanofluids in the forced and free convection and boiling processes determining the gas-tube boiler efficiency are considered. Criteria dependences of calculating the heat transfer in the free and forced convection and boiling when nanofluids flowing through the heat generators are proposed. It is proved that when adding nanoparticles to the base liquid, an increase in the heat transfer coefficient will be observed if its thermal conductivity is increased. Besides, the convective heat transfer is affected by the density and viscosity of the nanofluid. When the liquid boils, the critical heat flux increases, and the determining factor of the heat transfer coefficient is the particles concentration. The represented data are prerequisites of developing the efficient gas-tube boiler with a high-temperature fluid.