Comparison between Solar Simulation and Infrared Technique for Thermal Balance Test
The precision of heat flux simulation influences the temperature field and test aberration for TB test and also reflects the test level for spacecraft development. This paper describes TB tests for a small satellite using solar simulator, electric heaters, calrod heaters to evaluate the difference of the three methods. Under the same boundary condition, calrod heaters cases were about 6C higher than solar simulator cases and electric heaters cases for non-external-heat-flux cases (extreme low temperature cases). While calrod heaters cases and electric heaters cases were 5~7C and 2~3C lower than solar simulator cases respectively for high temperature cases. The results show that the solar simulator is better than calrod heaters for its better collimation, non-homogeneity and stability. Keywords—solar simulation, infrared simulation, TB test, TMM
Heat transfer and thermal efficiency of a lab-fabricated ferrofluid-based single-ended tube solar collector under the effect of magnetic field: An experimental study
Abstract Heat transfer and thermal efficiency of a single-ended all-glass evacuated tube solar collector (SEETSC), as a special type of heat exchanger in the solar thermal systems, can be improved using ferrofluids, as working fluid, under the effect of the magnetic field. The present experimental study investigates the natural convection, and thermal efficiency of a lab-fabricated ferrofluid (Mn–Zn Fe2O4/water) based single-ended tube solar collector, as a simplified model of the SEETSCs, in the presence of non-uniform magnetic field. Effect of the nanoparticles volume fraction (0.0–0.5%), input heat flux ( q in ′ ′ =50–350 W/m2) and the magnetic field generated by several identical permanent magnets (remanent magnetization (Br) = 0.02–1.0 T) on the heat transfer and thermal efficiency of the collector is investigated. The results show that applying a magnetic field causes not only compensation of the heat transfer reduction due to the high viscosity values but also improvement of it. The maximum enhancements in the obtained average Nusselt number and thermal efficiency are respectively about 73.0% and 47.0% for the 0.5 vol% ferrofluid at q in ′ ′  = 350 W/m2 and Br = 1.0 T. According to this study, it can be feasible to enhance the thermal efficiency of the SEETSCs-based solar thermal systems using the ferrofluid under the effect of magnetic field.
Investigations of dielectric gratings using electrodynamic models based on volume integral equations
Eigenmodes of planar and cylindrical dielectric gratings (DGs) and electromagnetic wave scattering from multiplayer DGs are investigated. The DG characteristics are calculated using numerical-analytical solution of integral equations (IEs).