Utilization of Zinc-Ferrite/ Water Hybrid Nanofluids for enhancing thermal performance of a Flat Plate Solar Collector -An Analytical Study

Thermodynamic performance analysis is carried out on a flat plate solar thermal collector utilizing single and hybrid nanofluids. As heat transfer fluids, Fe2O4/water, Zn-Fe2O4/water hybrid nanofluids, and water are used, and its performance are compared based on the energy and exergy transfer rate. The thermo-physical properties are evaluated by regression polynomial model for all the working fluids. Developed codes in MATLAB solve the collector's thermal model iteratively, energy and exergetic performance are evaluated. The system was then subjected to parametric investigation and optimization for variations in fluid flow rate, temperatures, and concentrations of nanoparticles. The findings show that utilizing Zn-Fe2O4/water hybrid nanofluids with a particle concentration of 0.5 percent enhanced the solar collector's thermal performance by 6.6% while using Fe2O4/water nanofluids raised the collector's thermal performance by 7.83% when compared to water as the working fluid. While hybrid nanofluids give a better thermal alternative than water and single nanofluids, they have also produced a 5.36% increase in exergetic efficiency and an enhancement of 8.24 percent when used with Fe2O4/water nanofluids.

Performance and Exergy Transfer Analysis of Heat Exchangers with Graphene Nanofluids in Seawater Source Marine Heat Pump System

A marine seawater source heat pump is based on the relatively stable temperature of seawater, and uses it as the system’s cold and heat source to provide the ship with the necessary cold and heat energy. This technology is one of the important solutions to reduce ship energy consumption. Therefore, in this paper, the heat exchanger in the CO2 heat pump system with graphene nano-fluid refrigerant is experimentally studied, and the influence of related factors on its heat transfer enhancement performance is analyzed. First, the paper describes the transformation of the heat pump system experimental bench, the preparation of six different mass concentrations (0~1 wt.%) of graphene nanofluid and its thermophysical properties. Secondly, this paper defines graphene nanofluids as beneficiary fluids, the heat exchanger gains cold fluid heat exergy increase, and the consumption of hot fluid heat is heat exergy decrease. Based on the heat transfer efficiency and exergy efficiency of the heat exchanger, an exergy transfer model was established for a seawater source of tube heat exchanger. Finally, the article carried out a test of enhanced heat transfer of heat exchangers with different concentrations of graphene nanofluid refrigerants under simulated seawater constant temperature conditions and analyzed the test results using energy and an exergy transfer model. The results show that the enhanced heat transfer effect brought by the low concentration (0~0.1 wt.%) of graphene nanofluid is greater than the effect of its viscosity on the performance and has a good exergy transfer effectiveness. When the concentration of graphene nanofluid is too high, the resistance caused by the increase in viscosity will exceed the enhanced heat transfer gain brought by the nanofluid, which results in a significant decrease in the exergy transfer effectiveness.

Second Law Analysis of Spectral Radiative Transfer and Calculation in One-Dimensional Furnace Cases

This study combines the radiation transfer process with the thermodynamic second law to achieve more accurate results for the energy quality and its variability in the spectral radiation transfer process. First, the core ideas of the monochromatic photon exergy theory based on the equivalent temperature and the infinite-staged Carnot model are reviewed and discussed. Next, this theory is combined with the radiation transfer equation and thus the spectral radiative entropy and the radiative exergy transfer equations are established and verified based on the second law of thermodynamics. Finally, one-dimensional furnace case calculations are performed to determine the applicability to engineering applications. It is found that the distribution and variability of the spectral radiative exergy flux in the radiation transfer process can be obtained using numerical calculations and the scatter media could slightly improve the proportion of short-wavelength radiative exergy during the radiation transfer process. This has application value for research on flame energy spectrum-splitting conversion systems.