Numerical investigation of heat transfer enhancement in solar air heaters using polygonal-shaped ribs and grooves

Solar air heating thermal systems have found extensive utilization in a broad array of industrial and residential settings, playing a pivotal role in the conversion and reclamation of solar energy. Implementing repeated artificial roughness in the surfaces has the potential to augment thermal performance in solar air heaters (SAHs). This study presents a numerical investigation of SAHs with artificial rough surfaces, consisting of polygonal-shaped ribs and grooves located at different places inside the rectangular duct, that improve thermal efficiency. ANSYS Fluent software was employed to simulate the SAH with different relative pitch distances of p = 10 mm and 20 mm and relative rib heights e/d = 0.09–0.045. The working fluid air flows at different Reynolds numbers (Re), ranging from 3,800 to 18,000. Nusselt number (Nu), friction factor (f), and Thermal Hydraulic Performance (THP) are parameters to evaluate the performance of the SAH. The renormalized group (RNG) k-ϵ turbulent model was implemented in this simulation. The study outcomes indicate that increasing the rib height improves the heat transfer rate and nonetheless increases pressure drop while increasing the pitch distance. The higher Nusselt number (Nu) is 3.762 attained at p = 10 mm and 3.420 at p = 20 mm in the center-positioned rib at Re 3,800. The lower friction factor (ƒ) obtained in p = 20 mm is 1.681 and 0.785 in p = 10 mm in the staggered positioned rib at higher Re 15,000. The optimal THP was achieved at 2.813 at a staggered rib height at a pitch distance of p = 10 mm at Re 8,000. The study’s findings suggest that the incorporation of artificial rough surfaces has the potential to enhance the THP of an SAH

Effect of surgical experience and spine subspecialty on the reliability of the {AO} Spine Upper Cervical Injury Classification System

OBJECTIVE The objective of this paper was to determine the interobserver reliability and intraobserver reproducibility of the AO Spine Upper Cervical Injury Classification System based on surgeon experience (< 5 years, 5–10 years, 10–20 years, and > 20 years) and surgical subspecialty (orthopedic spine surgery, neurosurgery, and "other" surgery). METHODS A total of 11,601 assessments of upper cervical spine injuries were evaluated based on the AO Spine Upper Cervical Injury Classification System. Reliability and reproducibility scores were obtained twice, with a 3-week time interval. Descriptive statistics were utilized to examine the percentage of accurately classified injuries, and Pearson’s chi-square or Fisher’s exact test was used to screen for potentially relevant differences between study participants. Kappa coefficients (κ) determined the interobserver reliability and intraobserver reproducibility. RESULTS The intraobserver reproducibility was substantial for surgeon experience level (< 5 years: 0.74 vs 5–10 years: 0.69 vs 10–20 years: 0.69 vs > 20 years: 0.70) and surgical subspecialty (orthopedic spine: 0.71 vs neurosurgery: 0.69 vs other: 0.68). Furthermore, the interobserver reliability was substantial for all surgical experience groups on assessment 1 (< 5 years: 0.67 vs 5–10 years: 0.62 vs 10–20 years: 0.61 vs > 20 years: 0.62), and only surgeons with > 20 years of experience did not have substantial reliability on assessment 2 (< 5 years: 0.62 vs 5–10 years: 0.61 vs 10–20 years: 0.61 vs > 20 years: 0.59). Orthopedic spine surgeons and neurosurgeons had substantial intraobserver reproducibility on both assessment 1 (0.64 vs 0.63) and assessment 2 (0.62 vs 0.63), while other surgeons had moderate reliability on assessment 1 (0.43) and fair reliability on assessment 2 (0.36). CONCLUSIONS The international reliability and reproducibility scores for the AO Spine Upper Cervical Injury Classification System demonstrated substantial intraobserver reproducibility and interobserver reliability regardless of surgical experience and spine subspecialty. These results support the global application of this classification system

Review of Waste Cooking Oil (WCO) as a Feedstock for Biofuel—Indian Perspective

A detailed review was conducted to explore waste cooking oil (WCO) as feedstock for biodiesel. The manuscript highlights the impact on health while using used cooking oil and the scope for revenue generation from WCO. Up to a 20% blend with diesel results in less pollutants, and it does not demand more modifications to the engine. Also, this reduces the country’s import bill. Furthermore, it suggests the scope for alternate sustainable income among rural farmers through a circular economy. Various collection strategies are discussed, a SWOC (strength, weakness, opportunity, and challenges) analysis is presented to aid in understanding different countries’ policies regarding the collection of WCO, and a more suitable method for conversion is pronounced. A techno-economic analysis is presented to explore the viability of producing 1 litre of biodiesel. The cost of 1 litre of WCO-based biodiesel is compared with costs Iran and Pakistan, and it is noticed that the difference among them is less than 1%. Life cycle assessment (LCA) is mandatory to reveal the impact of WCO biodiesel on socio-economic and environmental concerns. Including exergy analysis will provide comprehensive information about the production and justification of WCO as a biodiesel

Anti-inflammatory, remorin-like protein from green marine Macroalga Caulerpa sertularioides (S.G.Gmel.) M.Howe

The most prevalent natural source of hydrocolloids, cosmetics, medications, and nutraceuticals is marine seaweed (macroalgae). Numerous bioactivities, including antiviral, anticancer, anti-inflammatory, and immunomodulatory characteristics, have been found in bioactive substances such as polyphenols and sulfated and non-sulfated polysaccharides. As a result, new start-up projects and industries based on seaweed are emerging in all regions of the world with abundant marine biodiversity. In this current investigation, the anti-inflammatory activity of two different marine macroalgae Caulerpa racemosa (CR) and Caulerpa sertularioides (CS) was evaluated. Consequently, CS demonstrated more anti-inflammatory and antioxidant effects at a lower dose than CR. The IC50 value for DPPH inhibition was 456.1 μg/mL, and 180.9 μg/mL for CS and CR respectively. A similar result was obtained in the case of protein denaturation (PD), membrane stabilization (MS), and protease inhibition (PI) anti-inflammatory assays with 127.2 μg/mL, 135.5 μg/mL, and 71.88 μg/mL for CR, and 66.78 μg/mL, 88.96 μg/mL, and 59.54 μg/mL for CS respectively. Based on the SDS-PAGE, the molecular weight of lectin responsible for the anti-inflammatory activity was determined as 17 kDa. Protein mass fingerprinting was performed for the particular lectin by in-gel trypsin digestion, MALDI-MS analysis, and Mascot peptide mass fingerprinting. Because of this, the unidentified lectin protein was discovered to be a remorin-like protein that shared 65% of its sequence with the remorin-like protein of Aegilops tauschii subsp. tauschii. Therefore, it is the hitherto report on the presence of remorin-like protein from the green macroalga Caulerpa sertularioides

Effect of baffle shape in heat transfer for jet impingement on a solid block

The numerical solution solution is obtained for fluid flow and heat transfer in a confined impinging slot on a solid block with the presence of baffles. In order to consider the effect of baffle shape the rectangular and semi circular baffles are considered and for the effect for Reynolds number the Reynolds number is varied from 100 to 300 with the step of 50. The present study reveals the vital impact of Baffle shape and Reynolds number (Re) on the fluid flow and heat transfer characteristics over a wide range. It is finally added that the presence of baffle improves the Nusselt number. The Nusselt number increases with the increase of Reynolds number. The present study proved that, the primary peak of Nusselt number occurs nearer to the reattachment length. The secondary peak of Nusselt number occurs nearer to the baffle. It is observed that for semi circle baffle the velocity attains maximum one compared to rectangular baffle

Effect of baffle shape in heat transfer for jet impingement on a solid block

The numerical solution solution is obtained for fluid flow and heat transfer in a confined impinging slot on a solid block with the presence of baffles. In order to consider the effect of baffle shape the rectangular and semi circular baffles are considered and for the effect for Reynolds number the Reynolds number is varied from 100 to 300 with the step of 50. The present study reveals the vital impact of Baffle shape and Reynolds number (Re) on the fluid flow and heat transfer characteristics over a wide range. It is finally added that the presence of baffle improves the Nusselt number. The Nusselt number increases with the increase of Reynolds number. The present study proved that, the primary peak of Nusselt number occurs nearer to the reattachment length. The secondary peak of Nusselt number occurs nearer to the baffle. It is observed that for semi circle baffle the velocity attains maximum one compared to rectangular baffle

Numerical investigation of heat transfer from a two-dimensional sudden expansion flow using nanofluids

Laminar forced convection heat transfer from two-dimensional sudden expansion flow of different nanofluids is studied numerically. The governing equations are solved using the unsteady stream function-vorticity method. The effect of volume fraction of the nanoparticles and type of nanoparticles on heat transfer is examined and found to have a significant impact. Local and average Nusselt numbers are reported in connection with various nanoparticle, volume fraction, and Reynolds number for expansion ratio 2. The Nusselt number reaches peak values near the reattachment point and reaches asymptotic value in the downstream. Bottom wall eddy and volume fraction shows a significant impact on the average Nusselt number

Synthesis and Empirical Analysis of the Thermophysical Characteristics of GO-Ag Aqueous Hybrid Nanofluid Using Environmentally Friendly Reducing and Stabilizing Agents

The remarkable potential of the carbon allotrope graphene and its derivatives in developing hybrid nanofluids has sparked considerable interest among researchers. These carbon nanoparticles offer excellent opportunities to blend with various metal or metal oxide nanoparticle binders to improve their material properties. This study focuses on investigating the synthesis, characterization, and thermophysical properties of silver- (Ag-) infused GO aqueous hybrid nanofluids with various weight percentages (0.025, 0.05, and 0.1 wt.%) using environmentally friendly reducing and stabilizing agents. Characterization of the hybrid nanofluids was performed using XRD, SEM, EDX, a UV-visible spectrometer, a particle size analyzer, and FTIR techniques. The thermal conductivity and viscosity of the GO-Ag hybrid nanofluids were experimentally determined in the temperature range of 293 K–333 K. Notably, the results indicated that the nanofluids with a concentration of 0.1 wt.% exhibited the most significant enhancement in thermal conductivity, with improvements of 15.22% at 293 K and 31.19% at 333 K compared to the base fluid. A mathematical model was developed based on the thermal conductivity experimental results using the response surface methodology (RSM). Overall, the results suggest that the silver nanoparticles-decorated aqueous graphene oxide hybrid nanofluid has promising potential as an innovative heat transfer fluid in various heat transfer applications