Lattice Boltzmann numerical method for natural convection and entropy generation in cavity with refrigerant rigid body filled with DWCNTs-water nanofluid-experimental thermo-physical properties

Abstract

In the present study, the natural convection heat transfer and total entropy generation are analyzed by utilizing Lattice Boltzmann numerical method. The simulations are performed for square cavity in presence of refrigerant rigid body. Moreover, the cavity is filled with the DWCNTs-water. The utilized nanofluid is prepared in the laboratory, and the thermo-physical properties, thermal conductivity and dynamic viscosity, of the nanofluid are measured experimentally by means of modern measuring devices. The DWCNTs-water nanofluid is obtained in different solid volume fractions of 0.01%, 0.02%, 0.05%, 0.1%, 0.2%, and 0.5%, and thermo-physical properties are measured in all solid volume fractions and temperature range of 300–340 (K). The side walls have constant/uniform hot temperature, the top and bottom walls are insulated, and the rigid bodies are cooled with constant/uniform temperature acting like refrigerant components. Effects of different governing parameters such as four different positions of refrigerant rigid bodies, Rayleigh number and solid volume fraction on the flow structure, temperature map, Nusselt number and total/local entropy generation are obtained and discussed comprehensively. It is concluded that the array of refrigerant bodies has significant influence on the streamlines and isothermal lines. Furthermore, the average Nusselt number is highest as array is in Double Vertical form, and is lowest when the array is in Single Horizontal form. Also, the Nusselt number has direct relationship with Rayleigh number and solid volume fraction. On the other hand, the total entropy generation has direct and reverse relationship with Rayleigh number and solid volume fraction, respectively.