Substrate finishing and niobium content effects on the high temperature corrosion resistance in steam atmosphere of CrN/NbN superlattice coatings deposited by PVD-HIPIMS

The main objective of this work was to evaluate the oxidation resistance of three PVD-HIPIMS CrN/NbN coatings, studying the effect of the surface finishing of the substrate and the role of niobium content into the coating composition. CrN/NbN nano-multilayered films on P92 steel were tested at 650°C in pure steam atmosphere. The mass gain was measured at fixed intervals to study their oxidation kinetics. The morphology and thickness of nanoscales were measured by transmission electron microscopy (TEM). Characterization of coatings before and after the thermal treatment was performed by scanning electron microscopy-energy with facilities of dispersive X-ray spectroscopy (SEM–EDX) and X-ray diffraction (XRD). All coatings improved the oxidation resistance of the substrate material, but the best behaviour was exhibited by the CrN/NbN with the high niobium (Nb) content and deposited on the substrate with the finest surface finishing

Effect of parabolic solar energy collectors for water distillation

This research article briefly summarizes the augmentation of condensate output using concentrators. This study compares a single-slope solar still, a compound conical concentrator (CCC) solar still, and a compound parabolic concentrator–tubular solar still (CPC–TSS). The effect of miniaturization of the absorber (increase in the concentration factor) and some modifications in the solar still assembly show a remarkable increase in output. The measured daily yield rate per square meter of absorber area of the single slope solar still, CCC solar still, and CPC–TSS is 2,100, 18,000, and 6,100 ml, respectively. It was found that the CCC solar still provides the maximum yield

Effect of heat removal on tubular solar desalting system

The technological process integration will influence directly on the energy efficient conversion with vital role on system productivity. In this work, an attempt was made to investigate on the performance of a compound parabolic concentrator-concentric tubular solar still (CPC-CTSS) coupled with a single slope solar still. A set of 2 m long concentric tubes with rectangular basins of the same length was fabricated (2 m2 area) and the entire experimental setup was operated with cold water flow over the inner tubes of the concentric arrangement. This pre-heated water was fed to a single slope solar still. The area of the single slope solar still was 0.25 m2 and the glass had an angle of 11° from the horizontal. It was clearly observed that the yield strongly depends on the evaporative heat transfer coefficient. It was concluded that, to increase the distillate augmentation to overnight, phase change material was additionally incorporated in the single slope solar still

Numerical and Experimental Investigation on a Combined Sensible and Latent Heat Storage Unit Integrated With Solar Water Heating System

The present work investigates, theoretically and experimentally, the thermal performance of a packed bed combined sensible and latent heat storage unit, integrated with the solar water heating system. A one-dimensional porous medium approach with the finite difference technique is used to develop the numerical model to obtain the temperature profiles of both the phase change material (PCM) and heat transfer fluid (HTF), and the molten mass fraction of the PCM at any axial location of the cylindrical storage tank during the charging process. The model also incorporates the effect of the varying fluid inlet temperature to accommodate the actual conditions that prevails in the solar collector. Experimental apparatus utilizing paraffin as PCM, which is filled in high-density polyethylene spherical capsules, is constructed and integrated with a solar flat plate collector to conduct the experiments. The water used as HTF to transfer heat from the solar collector to the storage tank also acts as a sensible heat storage (SHS) material. The results of the numerical model are compared into the experimental results of the temperature profile for various porosities and HTF flow rates. It is found that the results of the numerical model are in good agreement with the experimental results. The performance parameters, such as instantaneous heat stored, cumulative heat stored, and charging rate are also studied in detail.</jats:p