Novel preparation of metal-free carbon xerogels under acidic conditions and their performance as high-energy density supercapacitor electrodes.

The development of metal-free supercapacitor electrodes with a high energy density is a crucial requirement in the global shift towards sustainable energy sources and industrial pursuit of an optimal supercapacitor. Indeed, from an industrial perspective, time assumes a paramount role in the manufacturing process. A majority of synthesis methods employed for the fabrication of carbon xerogel-based supercapacitor electrodes are characterized by prolonged durations, and result in relatively poor energy and power density. These limitations hinder their practical applications and impede their widespread manufacturing capabilities. In this study, carbon xerogel-based supercapacitor electrodes were made in the shortest time ever reported by making the condition highly acidic with hydrochloric acid (HCl). Furthermore, the investigation of the effect of HCl concentrations (0.1 M, 0.05 M, and 0.01 M) on the morphology and electrochemical behavior of the prepared samples is reported herein. Interestingly, the highest concentration of HCl developed the highest BET surface area, 1032 m2 g-1, which enforced the capacitive behavior to deliver a specific capacitance of 402 F g-1 at 1 A g-1 and a capacitance retention of 80.8% at a current density of 2 A g-1 in an electrolyte containing 0.5 M H2SO4 + 0.5 M Na2SO4. Moreover, an impressive energy density of 45 W h kg-1 at a power density of 18.2 kW kg-1 was achieved. Interestingly, as the HCl concentration increased, the equivalent series resistance decreased to 3.9 W with carbon xerogel 0.1 M HCl (CX0.1). The superior performance of CX0.1 may be attributed to its enlarged BET surface area, pore volume, pore diameter, and smaller particle size. This work provides a facile approach for the large-scale production of metal-free carbon supercapacitor electrodes with improved performance and stability and opens novel horizons to explore the impacts of many types of catalysts during the carbon xerogel preparation.

A new fractional Cattaneo model for enhancing the thermal performance of photovoltaic panels using heat spreader: energy, exergy, economic and enviroeconomic (4E) analysis.

A new fractional non-Fourier (Cattaneo) photovoltaic (PV) model is presented to enhance the thermal performance of a PV system combined with a heat spreader (HS). The fractional Cattaneo model is shown to be effective in examining transient processes across the entirety of a PV system, in contrast to the conventional Fourier model's inability to predict system performance. Consequently, a comparison is conducted between the classical Fourier model with the fractional Fourier and fractional Cattaneo models for the PV system. The impact of using an aluminum heat spreader, with rectangular and trapezoidal shapes, has been developed under hot and cold climate conditions. The findings show that adding a trapezoidal heat spreader reduced the cell temperature by 20 K in summer and 12 K in winter. The reduction in the PV temperature led to an enhancement in daily average power by approximately 28% and 37% in hot and cold weather, respectively. Moreover, economic, exergoeconomic, and enviroeconomic assessment is introduced. The outcomes revealed that the electrical production costs of the rectangular and trapezoidal HS systems are 0.272 and 0.214 $/kWh, respectively, while about 0.286 $/kWh for the conventional PV panel. Based on the environmental study, the estimated CO2 reduction for PV, PV with rectangular HS, and PV with trapezoidal spreader is 0.5504, 0.7704, and 0.8012 tons, respectively. Finally, real experimental data are used to validate the fractional Cattaneo model. The results demonstrate that there is a great fitting with the measured data, with errors in PV power and exergy efficiency of just 0.628% and 3.84%, respectively, whereas their corresponding values for the classical model are 5.72 and 13.13%.

Effects of Dietary Bioactive Lipid Compounds of Acacia nilotica Bark on Productive Performance, Antioxidant Status, and Antimicrobial Activities of Growing Rabbits under Hot Climatic Conditions.

This study aimed to evaluate the efficacy of dietary Acacia nilotica bark bioactive lipid compounds (ANBBLCs) as novel feed additives on the growth performance, carcass criteria, antioxidants, and antimicrobial activities of growing male rabbits. A total of 100 California male weanling rabbits aged 35 days were divided into four nutritional treatments, each of which contained ANBBLCs at concentrations of 0 (control group), 50, 100, and 150 mg/kg diet (n = 25 per treatment, each replication consisting of one animal). The average body weight of the animals was 613 ± 14 g. The experiments lasted for 56 days. Dietary ANBBLC levels linearly improved (p < 0.05) the body weight, body weight gain, and feed conversion ratio (FCR) of rabbits. Furthermore, with increasing concentrations of ANBBLCs, the total antioxidant capacity of blood and liver tissue was linearly (p < 0.05) enhanced. Lactobacillus increased and Staphylococcus decreased (p < 0.05) in comparison to the control group when ANBBLC levels were added to the diets of rabbits. Rabbit diets supplemented with ANBBLCs increased dressing percentages and decreased abdominal fat. This study shows that ANBBLCs can be used as a feed additive to enhance the growth performance, carcass criteria, antioxidant, and antibacterial properties of growing rabbits.

Effect of substituting hydroponic barley forage with or without enzymes on performance of growing rabbits.

This study aims to evaluate the effect of hydroponic barley (HB) by substituting control diet with 25% HB with or without enzymes on rabbit performance, nutrient digestibility, and economic efficiency. A total number of 60 growing male HyPlus rabbits (average body weight 669 ± 12 g, 30 days of age) were utilized in the present study. The rabbits were randomly assigned to three groups (n = 20 rabbits per group). The first group served as a control (C). The other two groups were fed the control diet substituted with 25% hydroponic barley HB (group CHB), and the control diet substituted with 25% HB added with 0.5 g/kg enzymes (CHBE). The experiment lasted for 56 days. The results revealed that daily body weight gain improved (P < 0.05) by 18.64% and 23.94%, and feed conversion ratio improved by 3.74% and 17.91% than control, respectively, during 30-86 days of age in CHB and CHBE groups. The economic efficiency was improved (P < 0.05) by 32.17% and 39.60% in CHB and CHBE diets, respectively, compared to control; and nutrient digestibility, and mineral retention of growing rabbits were also improved (P < 0.05) by substituting HB with or without enzymes compared to control diet. Overall, the best rabbit performances were observed in both CHB and CHBE groups. In conclusion, these results suggest that substituting 25% of concentrated control diet by hydroponic barley with or without enzymes have positive effects in a sustainable way on growth performance, nutrient digestibility, and economic efficiency of growing rabbits.

Productive, physiological and nutritional responses of laying hens fed different dietary levels of turmeric powder.

This study aimed to determine the impact of supplementation of turmeric powder on laying performance, egg quality, nutrient digestibility and some blood metabolites in laying hens. A total of one hundred and twenty Bovans Brown laying hens (55 weeks old) were assigned to one of four treatment diets (n = 30) for 12 weeks including turmeric powder at 0, 2.5, 5 or 7.5 g/kg respectively. The results revealed that egg production, egg weight and egg mass were significantly increased (p < 0.05), and the feed conversion ratio was significantly improved (p < 0.012) with increasing levels of turmeric in the laying hen diet. Egg thickness and Haugh unit were linearly increased (p < 0.01) with increasing supplementation levels. Moreover, compared with the control diet, the levels of turmeric powder supplementation significantly improved nutrient digestibility (p < 0.001). Moreover, the serum metabolic profile revealed that serum total cholesterol, aspartate aminotransferase, creatinine and urea concentrations were linearly decreased with increasing turmeric powder supplementation to hen diets. In conclusion, the inclusion of turmeric powder at 2.5, 5 or 7.5 g/kg diet improved egg production, nutrient digestibility, egg quality and serum metabolic profile and may be used as a feed additive in laying hens' nutrition. However, results indicate that the best improvement was observed when 5 g/kg were supplemented.

Biotechnology methods for succession of bacterial communities in polychlorinated biphenyls (PCBs) contaminated soils and isolation novel PCBs-degrading bacteria.

Polychlorinated Biphenyls (PCBs) are persistence in the contaminated sites as a result of lacking PCBs-degrading microorganisms. Cultivation-independent technique called single-strand-conformation polymorphism (SSCP) based on 16SrRNA genes was chosen to characterize the diversity of bacterial communities in PCBs polluted soil samples. The bacterial communities showed an increasing diversity from the genetic profiles using SSCP technique. 51 single products were identified from the profiles using PCR reamplification and cloning. DNA sequencing of the 51 products, it showed similarities to Acidobacteria, Actinobacteria, Betaproteobateria, Gammaproteobacteria and Alphaproteobacteria, the range of similarities were 92.3 to 100%. Pure 23 isolates were identified from PCBs contaminated sites. The identified isolates belonged to genus Bacillus, Brevibacillus, Burkholderia, Pandoraea, Pseudomonas, and Rhodococcus. The new strains have the capability to use PCBs as a source of sole carbon and harbor 2,3-dihydroxybiphenyl dioxygenase (DHBDO) which could be used as molecular marker for detection PCBs-degrading bacteria in the PCBs contaminated sites. This finding may enhance the PCBs bioremediation by monitoring and characterization of the PCBs degraders using DHBDO in PCBs contaminated sites.

A review of water electrolysis-based systems for hydrogen production using hybrid/solar/wind energy systems.

Hydrogen energy, as clean and efficient energy, is considered significant support for the construction of a sustainable society in the face of global climate change and the looming energy revolution. Hydrogen is one of the most important chemical substances on earth and can be obtained through various techniques using renewable and nonrenewable energy sources. However, the necessity for a gradual transition to renewable energy sources significantly hampers efforts to identify and implement green hydrogen production paths. Therefore, this paper's objective is to provide a technological review of the systems of hydrogen production from solar and wind energy utilizing several types of water electrolyzers. The current paper starts with a short brief about the different production techniques. A detailed comparison between water electrolyzer types and a complete illustration of hydrogen production techniques using solar and wind are presented with examples, after which an economic assessment of green hydrogen production by comparing the costs of the discussed renewable sources with other production methods. Finally, the challenges that face the mentioned production methods are illuminated in the current review.

Activated Glassy Carbon Electrode as an Electrochemical Sensing Platform for the Determination of 4-Nitrophenol and Dopamine in Real Samples.

Glassy carbon electrode (GCE) was electrochemically activated using a repetitive cyclic voltammetric technique to develop an activated glassy carbon electrode (AGCE). The developed AGCE was optimized and utilized for the electrochemical assay of 4-nitrophenol (4-NP) and dopamine (DA). Cyclic voltammetry (CV) was employed to investigate the electrochemical behavior of the AGCE. Compared to the bare GCE, the developed AGCE exhibits a significant increase in redox peak currents of 4-NP and DA, which indicates that the AGCE significantly improves the electrocatalytic reduction of 4-NP and oxidation of DA. The electrochemical signature of the activation process could be directly associated with the formation of oxygen-containing surface functional groups (OxSFGs), which are the main reason for the improved electron transfer ability and the enhancement of the electrocatalytic activity of the AGCE. The effects of various parameters on the voltammetric responses of the AGCE toward 4-NP and DA were studied and optimized, including the pH, scan rate, and accumulation time. Differential pulse voltammetry (DPV) was also utilized to investigate the analytical performance of the AGCE sensing platform. The optimized AGCE exhibited linear responses over the concentration ranges of 0.04-65 µM and 65-370 µM toward 4-NP with a lower limit of detection (LOD) of 0.02 µM (S/N = 3). Additionally, the AGCE exhibited a linear responses over the concentration ranges of 0.02-1.0 and 1.0-100 µM toward DA with a lower limit of detection (LOD) of 0.01 µM (S/N = 3). Moreover, the developed AGCE-based 4-NP and DA sensors are distinguished by their high sensitivity, excellent selectivity, and repeatability. The developed sensors were successfully applied for the determination of 4-NP and DA in real samples with satisfactory recovery results.

Soft computing and statistical approach for sensitivity analysis of heat transfer through the hybrid nanoliquid film in rotating heat pipe.

In this paper, the numerical solution for heat transfer through a rotating heat pipe is studied and a sensitivity analysis is presented by using statistical experimental design technique. Graphene oxide-molybdenum disulfide (GO-MoS2) hybrid nanofluid is taken as working fluid inside the pipe. The impact of the heat pipe parameters (rotation speed, initial mass, temperature difference) on the heat transfer and liquid film thickness is investigated. The mathematical model coupling the fluid mass flow rate and liquid film evolution equations in evaporator, adiabatic, and condenser zones of the heat pipe is constructed. The mathematical model is solved by implementation of "Particle Swarm Optimization" along with the finite difference method. The outcomes demonstrate that hybrid nanoparticles help to improve the heat transfer through the heat pipe and reduce liquid film thickness. The heat transfer rises with increasing temperature difference and reducing inlet mass, and it reduces slightly with rising rotation speed. The difference in liquid film thickness between the evaporator and condenser zones increases with increasing temperature difference and decreasing rotation speed. The impact of increasing the volume fraction of GO on the liquid film thickness is higher than that in the case of the MoS2 nanoparticles. However, an increase of the heat transfer is noticed in case of increasing the volume fraction of GO relative to increasing MoS2 concentration. Statistical analysis of the computed numerical data and the identification of significant parameters for total heat transfer are found using the response surface method. At 95% level of significance, the GO concentration in the hybrid nanofluid, inlet mass of the hybrid nanofluid and the temperature difference inside the evaporator zone of the pipe are found to be significant linear parameters for increasing heat transfer.

Characterization and Expression Analysis of Extradiol and Intradiol Dioxygenase of Phenol-Degrading Haloalkaliphilic Bacterial Isolates.

Haloalkophilic bacteria have a potential advantage as a bioremediation organism of high oil-polluted and industrial wastewater. In the current study, Haloalkaliphilic isolates were obtained from Hamralake, Wadi EL-Natrun, Egypt. The phenotype script, biochemical characters, and sequence analysis of bacterial-16S rRNA were used to identify the bacterial isolates; Halomonas HA1 and Marinobacter HA2. These strains required high concentrations of NaCl to ensure bacterial growth, especially Halomonas HA1 strain. Notably, both isolates can degrade phenol at optimal pH values, between 8 and 9, with the ability to grow in pH levels up to 11, like what was seen in the Halomonas HA1 strain. Moreover, both isolates represent two different mechanistic pathways for phenol degradation. Halomonas HA1 exploits the 1,2 phenol meta-cleavage pathway, while Marinobacter HA2 uses the 2,3 ortho-cleavage pathway as indicated by universal primers for 1,2 and 2,3 CTD genes. Interestingly, Marinobacter HA2 isolate eliminated the added phenol within an incubation period of 72 h, while the Halomonas HA1 isolate invested 96 h in degrading 84% of the same amount of phenol. Phylogenetic analysis of these 1,2 CTD (catechol dioxygenase) sequences clearly showed an evolutionary relationship between 1,2 dioxygenases of both Halomonadaceae and Pseudomonadaceae. In comparison, 2,3 CTD of Marinobacter HA2 shared the main domains of the closely related species. Furthermore, semi-quantitative RT-PCR analysis proved the constitutive expression pattern of both dioxygenase genes. These findings provide new isolates of Halomonas sp. and Marinobacter sp. that can degrade phenol at high salt and pH conditions via two independent mechanisms.

Biochemical and genetic characterization comparison of four extradiol dioxygenases in Rhizorhabdus wittichii RW1.

Rhizorhabdus (previously Sphingomonas) wittichii RW1 uses a diverse array of aromatic organic compounds as energy and carbon sources, including some extremely recalcitrant compounds such as dibenzo-p-dioxin and dibenzofuran. Extradiol dioxygenases play a key role in the metabolism of dibenzofuran (DBF), dibenzo-p-dioxin (DBD), PCBs, and various other aromatic compounds. In this study, a detailed kinetic analysis of four extradiol dioxygenases identified in R. wittichii RW1 (DbfB, Edo2, Edo3, and Edo4) showed all of them to be typical 2,3dihydroxybiphenyl (DHB) dioxygenases with DHB as preferred substrate (kcat/Km values of 0.13-188 (µM -1 s-1)) and only slightly lower activity against trihydroxybiphenyl (THB) whereas monocyclic substrates were, to different extents, poor substrates due to high km values. All extradiol dioxygenases analyzed were subject to mechanism-based inactivation by 2,2`,3-trihydroxybiphenylether (THBE) the intermediate of DBD degradation. However, Edo4 was superior as reflected by the relatively high partition ratio and the comparably low efficiency of inactivation. Significant differences were observed with respect to their inactivation by 3-chlorocatechol. The absence of any significant mechanism-based inactivation makes Edo3 a perfect candidate for being recruited for chlorobiphenyl degradation where inactivation of extradiol dioxygenases by this intermediate creates significant metabolic problems. KEY POINTS: • Characterization of additional extradiol dioxygenases encoded by RW1 • Identification of differences in 2,2`,3-trihydroxybiphenylether transformation • Identification of differences in inhibition by 3-chlorocatechol.

Study of the performance of thermoelectric generator for waste heat recovery from chimney: impact of nanofluid-microchannel cooling system.

A huge number of chimneys all over the world utilized in many industrial applications and applications like restaurants, homes, etc. contribute badly on the global warming and climate change due to their waste heat. So, in this paper, the performance of thermoelectric generator (TEG) cooled by microchannel heat spreader having nanofluid and used for waste heat recovery from vertical chimney is investigated. Using heat spreader with microchannel cooling system increases the output TEG power compared to natural convection cooling system. In this paper, the impact of microchannel sizes, using nanofluid and heat spreader with different sizes on the TEG performance and cooling, is considered. Three-dimensional mathematical models including TEG, microchannel, nanofluid, and heat spreader are presented and solved by Ansys Fluent software utilizing user-defined memory, user-defined function, and user-defined scalar. All TEG effects (Joule, Seebeck, and Thomson) are considered in TEG model. Results indicate that TEG power rises with increasing the heat spreader and microchannel sizes together. Increasing microchannel and heat spreader sizes four times of TEG size raises the TEG output power by 10%. This also achieves the maximum cooling system efficiency of 88.9% and the maximum net output power. Microchannel heat spreader cooling system raises the system (TEG power-pumping power) net power by 125.2% compared to the normal channel and decreases the required cooling fluid flow rate. Utilizing copper-water and Al2O3-water nanofluids rises maximally the TEG output power by 14% and 4%, respectively; however, it increases the pumping power. Moreover, using nanofluids increases the net output power at low Reynolds number and decreases it at higher Reynolds number.

Isolation and Characterization a Novel Catabolic Gene Cluster Involved in Chlorobenzene Degradation in Haloalkaliphilic Alcanivorax sp. HA03.

Chlorobenzene (CB) poses a serious risk to human health and the environment, and because of its low degradation rate by microorganisms, it persists in the environment. Some bacterial strains can use CB as growth substrates and their degradative pathways have evolved; very little is known about these pathways and the enzymes for CB degradation in high pH and salinity environments. Alcanivorax sp. HA03 was isolated from the extremely saline and alkaline site. HA03 has the capability to degrade benzene, toluene and chlorobenzene (CB). CB catabolic genes were isolated from HA03, which have a complete gene cluster comprising α and ß subunits, ferredoxin and ferredoxin reductase (CBA1A2A3A4), as well as one gene-encoding enzyme for chlorocatechol 1,2-dioxygenase (CC12DOs). Based on the deduced amino acid sequence homology, the gene cluster was thought to be responsible for the upper and lower catabolic pathways of CB degradation. The CBA1A2A3A4 genes probably encoding a chlorobenzene dioxygenase was confirmed by expression during the growth on CB by RT-PCR. Heterologous expression revealed that CBA1A2A3A4 exhibited activity for CB transformation into 3-chlorocatechol, while CC12DOs catalyze 3-chlorocatechol, transforming it into 2-chloromucounate. SDS-PAGE analysis indicated that the sizes of CbA1 and (CC12DOs) gene products were 51.8, 27.5 kDa, respectively. Thus, Alcanivorax sp. HA03 constitutes the first bacterial strain described in the metabolic pathway of CB degradation under high pH and salinity conditions. This finding may have obvious potential for the bioremediation of CB in both highly saline and alkaline contaminated sites.

Different surgical procedures for reconstruction of soft-tissue defects around the ankle.

INTRODUCTION: Management of soft tissue defects around the ankle is a difficult and challenging situation for all reconstructive surgeons. A microsurgical free flaps coverage can solve this problematic situation especially with large defects that is not available in all trauma centers. Moreover, long operating time and suitable operative demands are considered obstacles. MATERIALS AND METHOD: Eighty five patients having soft tissue defects around ankle were included in this study. They underwent various reconstructions in our specialized hand and reconstructive microsurgery unit from 2015 to 2019. Fifty two were males and thirty three patients were females. Road traffic accident was the main cause of injury in 66 patients followed by implant exposure in 15 patients and chronic osteomyelitis in 4 patients. Distally based superficial sural artery flap was used to reconstruct the defects in 21 cases, free flap was used in 32 cases, Rotational local flap was used in 8 cases, contralateral distally based superficial sural artery flap was used in 2 cases, full or partial skin flaps were used in 10 cases and Propeller flap was used in 12cases. RESULTS: All flaps survived except for one modified sural flap with 98% success rate and average follow up of 48 months. All patients were satisfied with the functional capacity of operated limbs. Average time of bone healing postoperative was 3 months with gradual return to original work with acceptable degrees for cosmotic appearance of the limbs. CONCLUSION: Many treatment options are available to cover defects around the ankle. Propeller and rotational flaps are fast and easy but cover small defects, distally-based modified sural artery flap is an excellent reliable flap. Microsurgical free flaps provide good contour, color, texture and cover large defects but require microsurgery facilities to execute.

Loads of Coliforms and Fecal Coliforms and Characterization of Thermotolerant Escherichia coli in Fresh Raw Milk Cheese.

The aim of this study was to assess the hygienic status of raw milk cheese and determine the trends of virulence and antimicrobial resistance in thermotolerant Escherichia coli. Two hundred samples of karish, a popular Egyptian fresh raw milk cheese, were analyzed for coliforms and fecal coliforms using a standard most probable number (MPN) technique. Overall, 85% of samples were unsuitable for consumption, as they exceeded Egyptian standards for coliforms (10 MPN/g), and 65% of samples exhibited coliforms at 44.5 °C. Of 150 recovered thermotolerant strains, 140 (93.3%) were identified as E. coli. Importantly, one Shiga toxin-producing E. coli (STEC) strain carrying a striking virulence pattern, stx1-, stx2+, eae-, was detected. Eleven strains (7.8%, 11/140) showed resistance to third-generation cephalosporins. Antibiotic resistance genes included blaSHV, blaCTX-M, qnrS, tet(A), and tet(B), which were present in 4.3%, 2.8%, 0.71%, 2.1%, and 0.71% of isolates, respectively. In conclusion, this study indicated that hygienic-sanitary failures occurred throughout the production process of most retail karish cheese. Furthermore, our findings emphasize the need for adopting third-generation cephalosporin-resistant E. coli as an indicator for monitoring antimicrobial resistance in raw milk cheese to identify the potential public health burden associated with its consumption.

Occurrence, Phenotypic and Molecular Characteristics of Vancomycin-Resistant Enterococci Isolated from Retail Raw Milk in Egypt.

The aim of this study was to determine the occurrence, phenotypic and molecular characteristics of vancomycin-resistant enterococci (VRE), isolated from retail raw cow's milk. One hundred milk samples collected from retail shops in Egypt were examined for the occurrence of VRE by using kanamycin aesculin azide agar supplemented with 4 µg/mL vancomycin. PCR was conducted to determine enterococcal species and to screen the isolated strains for the presence of antibiotic resistance and virulence genes. All isolated strains were characterized by antimicrobial susceptibility testing for 12 antibiotics. From 24 samples (24%), we recovered 22 isolates (91.6%) classified as VRE (minimum inhibitory concentration ≥32) and 2 isolates (8.3%) classified as intermediate resistant to vancomycin (≤16). Enterococcus faecium (29.1%), Enterococcus faecalis (12.5%), Enterococcus casseliflavus (16.6%), and Enterococcus gallinarum (4.1%) were identified by using multiplex PCR. The genus Enterococcus was resistant to clindamycin (100%), linezolid (91.6%), teicoplanin (91.6%), erythromycin (87.5%), and tetracycline (29.1%). Co-resistance to vancomycin, teicoplanin, and linezolid was detected in 83.3% of isolates. Antibiotic resistance genes vanB, tet(M), tet(L), and erm(B) were identified in 29.1%, 16.6%, 8.3%, and 4.1% of isolates, respectively. Virulence genes gelE and esp were detected in 16.6% and 12.5% of isolates, respectively. In conclusion, the high occurrence of co-resistance to vancomycin, teicoplanin, and linezolid reported in this study is alarming. The high frequency of linezolid resistance prompts increased the attention of researchers to routinely perform linezolid susceptibility in food isolates. This study declares potential food safety risks from consumption and improper handling of raw milk regarding clinically important bacteria and promotes necessary legislation for forbidding the selling and consumption of retail raw milk.

Enhancement of the daily performance of solar still by exhaust gases under hot and cold climate conditions.

A study is presented on the enhancement of solar still (SS) performance by using chimney exhaust gases (EGs) passing through chimney channels under the still basin. The impact of the exhaust gas temperature on the SS temperature, productivity, efficiency, and freshwater yield cost is considered. The SS performance with the chimney is compared with that of conventional solar still. The study is performed under the hot and cold climate conditions of Upper Egypt. A complete transient mathematical model of the physical model including the solar still regions temperatures, yield, and heat transfer between the SS and the EGs is constructed. This model is solved by using Runge-Kutta method of fourth-order and programmed inside MATLAB software and validated using an experimental setup. The results show that the SS saline water temperature and freshwater yield rise with rising EGs temperatures. Furthermore, the impact of using EGs on the SS performance in winter is superior to that in summer, and also during the daytime is higher than that of night. Using chimney EGs at 75 °C and 125 °C enhances the daily freshwater yield of the SS by more than three times and about six times in winter, respectively, and about two and half times and more than three times in summer, respectively. Using EGs at 125 °C achieves a maximum solar still efficiency of 29.5% in winter and 49.5% in summer with an increase of 41% and 55.7%, respectively, and reduces its yield cost by 63.6% compared to conventional SS.

Energy and exergy assessment of new designed solar air heater of V-shaped transverse finned absorber at single- and double-pass flow conditions.

Flat plate solar collector is one of the main solar collectors that has a simple structure, reliable operation, large heat preoccupation area, and low cost. Its drawback is the low heat transfer between the working air and the absorber plate. A solar air heater of V-shaped transverse finned absorber having new designed absorber plate of lateral gaps and central holes to enhance its performance is investigated experimentally at single-pass and double-pass airflow conditions. Moreover, the energy and exergy assessment of its performance was studied and compared with traditional longitudinal finned heater having the same fin surface area and construction except for the absorber plate design. The study is investigated at air mass flow rates of 0.025, 0.05, and 0.075 kg/s. Findings show that the new heater achieves maximum outlet temperature rising of 28.2 °C at 0.025 kg/s and double-pass flow. Moreover, it has an average daily energy efficiency of 88.5%, 81.88%, and 61.3% at mass flow rates of 0.075, 0.05, and 0.025 kg/s with increments of 9.4%, 13.3%, and 9.66%, respectively, compared to the longitudinal finned heater. Additionally, it achieves exergy efficiencies of 2.5%, 2.1%, and 1.7% at mass flow rates of 0.025, 0.05, and 0.075 kg/s with increments 18%, 25.7%, and 18.2%, respectively, relative to longitudinal finned heater. Furthermore, the new heater design possesses greater energy efficiency comparing to former studied SAH designs.