Hot Springs Research Articles

Nutritional niches of potentially endemic, facultatively anaerobic heterotrophs from an isolated Antarctic terrestrial hydrothermal refugium elucidated through metagenomics

BackgroundTramway Ridge, a geothermal Antarctic Specially Protected Area (elevation 3340 m) located near the summit of Mount Erebus, is home to a unique community composed of cosmopolitan surface-associated micro-organisms and abundant, poorly understood subsurface-associated microorganisms. Here, we use shotgun metagenomics to compare the functional capabilities of this community to those found elsewhere on Earth and to infer in situ diversity and metabolic capabilities of abundant subsurface taxa.ResultsWe found that the functional potential in this community is most similar to that found in terrestrial hydrothermal environments (hot springs, sediments) and that the two dominant organisms in the subsurface carry high rates of in situ diversity which was taken as evidence of potential endemicity. They were found to be facultative anaerobic heterotrophs that likely share a pool of nitrogenous organic compounds while specializing in different carbon compounds.ConclusionsMetagenomic insights have provided a detailed understanding of the microbe-based ecosystem found in geothermally heated fumaroles at Tramway Ridge. This approach enabled us to compare Tramway Ridge with other microbial systems, identify potentially endemic taxa and elucidate the key metabolic pathways that may enable specific organisms to dominate the ecosystem.

Peculiarites of clay minerals formation in the Pleistocene sediments under specific tectonomagmatic and hydrothermal conditions of the Central Hill (Escanaba Trough, Gorda Ridge, Pacific Ocean). Communication 2. Holes ODP 1038A and 1038H

Clay minerals were studied in Pleistocene sediments from Holes 1038А, 114.50 m deep, and 1038Н, 192.80 m deep, which were drilled near a hydrothermal spring with a temperature of 217°C on Central Hill, 275 m east of Hole 1038B. In the sediments from Hole 1038A, at a depth of 8.52 m, the fraction 0.001 mm consists completely of chlorite. In the rest of the sediment section from Hole 1038A clay minerals consist of chlorite (from ~64 to ~98%) and illite. In sediments from Hole 1038H clay minerals also consist of chlorite and illite. Their formation occurred under conditions that arose at the intrusion of a basaltic melt in the form of a laccolith into the Escanaba trough and the heating under its influence of a solution, during the interaction of which with sediments at a high-temperature stage biotite was formed. With the subsequent slow cooling of the laccolith and fluid, the newly formed biotite was completely replaced by chlorite. Illite was precipitated from a hydrothermal solution. At a depth of 183 m, in sediments from Hole 1038H, clay minerals consist of biotite, chlorite and dioctahedral smectite, just as in sediments from Hole 1038B when they were formed under conditions of rapid cooling of the laccolith flank and penetration of sea water into the sediments. The similarities and differences in the processes of formation of clay minerals are shown in the Pleistocene sediments of the Central Hill, located above the slowly cooling part of the laccolith (Holes 1038A and 1038H), and in sediments located above the rapidly cooling flank of the laccolith (Hole 1038B).

Enhancing the efficiency of solar-powered water distillation units by utilization of waste heat

ABSTRACT Thermal water desalination is based on the evaporation and condensation of water, and such a process consumes a lot of energy, which lowers the economy of the process for commercial water desalination. The objective of this research is to improve the desalination energy efficiency of a novel domestic water desalination unit, which is based on thermal desalination, and this is done via utilization of the waste heat in the generated steam and reducing the operating costs. The distillation process begins with solar-powered evaporation of the salty water in the evaporator, followed by condensation of the generated water vapor coming from the evaporator over the cross-flow heat exchangers located in the condenser, which preheats the incoming saline water from the saltwater tank before it enters the evaporator. To assess the system's performance, comprehensive measurements are taken, including the electrical energy output from the PV panels and the volume of the output distilled water. Notably, the energy efficiency of the distillation is defined as the ratio of the heat energy gained by the distilled water, i.e. collected at the end of the day, to the electrical energy input to the electric heater, and it is found to be, on average, 82%.

Inhalation therapy with sulfur-rich thermal water for rhinogenic deafness: a series of case reports.

The study analyzed the effectiveness of a two-week cycle of sulfurous water therapy at Frasassi Thermal Springs ("Terme di Frasassi - S. Vittore", located in the Province of Ancona, Italy) on 8 patients suffering from rhinogenic deafness caused by chronic rhinosinusitis associated with nasal polyps and respiratory allergies. Patients underwent 12 sessions of sulfurous aerosol therapy and 12 bilateral tubal insufflations (1 aerosol and 1 insufflation per day). Pre- and post-treatment assessments included tympanometric measurements and a subjective evaluation of symptomatic improvement on a scale from 1 to 10. The median reported improvement was 9.5 (min: 7; max: 10). By the end of the treatment, all patients achieved a bilateral type A/A tympanogram, indicating restored tubal function. The results suggest that sulfurous water thermal therapy can be a useful treatment for rhinogenic deafness associated with chronic rhinosinusitis, nasal polyps, and respiratory allergies, with significant improvements in both auditory function and quality of life. Further studies are needed to compare this treatment with other therapies and to precisely evaluate the duration of the benefit over time.

Harnessing Geo-Diversity: Geosites and Geotourism in Uganda's Albertine Region

The Albertine Region of Uganda, an integral part of the Great Rift Valley, have a diverse array of geosites with exceptional geoheritage value. Despite the region's immense geological, geomorphological, structural, palaeontological, stratigraphic and mineralogical significance, as well as its potential as a prime geotourism destination, there is a scarcity of comprehensive studies on its geoheritage within the global geotourism literature. This research examined and assessed key geosites in the Albertine Region, emphasizing their educational value and unique geological characteristics that could attract geotourists. The study employed a rigorous methodology combining cartographic analysis, scientific literature review, GIS data integration, and field surveys to identify and evaluate the geosites based on their educational and touristic potential. The geosites were classified into thematic groups, including waterfalls, hot springs, glacial features, caves, rare mineral occurrences, and bedrock exposures. The evaluation revealed that several geosites possess considerable geotourism and educational potential, with some receiving high scores for both educational value and geotourism attractiveness. To capitalise on this potential and generate economic benefits for Uganda, a two-pronged approach is recommended, involving collaboration between government agencies and educational institutions to promote geosites and actively identify and develop potential sites. By doing so, the Albertine Region can be transformed into a premium geotourism destination in Uganda, generating economic benefits for the country while safeguarding its invaluable geoheritage.

A Report on Experiments on Spaces and Activities in Hot Springs Areas that Contribute to Visitor Well-Being

A Report on Experiments on Spaces and Activities in Hot Springs Areas that Contribute to Visitor Well-Being

Hydrogeochemical Characteristics and Genesis of Hot Springs in Da Qaidam Area, Northern Qaidam Margin of the Qaidam Basin

Hydrogeochemical research on fluids is an effective method to understand the formation mechanism, occurrence environment, and circulation process of groundwater. The groundwater sampling sites are located in the town of Dachaidan on the northeastern edge of the Tibetan Plateau, which was selected as the study object. Samples were collected from hot and cold springs and surface water in the area. This study is based on the analysis of water chemistry and isotopes, and aims (1) to discuss the chemical characteristics of groundwater in Da Qaidam, (2) to estimate the deep reservoir temperatures, recharge elevation and circulation depth of geothermal waters, and (3) to figure out the heat source beneath the geothermal area and its genetic mechanism. The result showed the following: The hydrochemical type of the hot spring is Cl·SO4-Na and Cl-Na, and the hydrochemical type of cold spring is SO4·HCO3-Na·Ca and Cl·HCO3·SO4-Ca·Na. The main source of groundwater recharge is snow and ice melt water. The recharge elevation ranges from 4666.8 m to 5755.9 m. The geothermal reservoir temperature is about 119.15–126.6 °C. Ice and snow melt water infiltrate into the high mountainous areas on the north side of Da Qaidam and circulate underground through the developed deep and large fractures. Part of the groundwater migrates upwards under the water conduction of the Da Qaidam fault fracture zone to form cold springs, while another part is heated by deep circulation and exposed to the surface in the form of medium to low temperature tectonic hot springs. The research results can provide a scientific basis for geothermal resource exploitation and utilization in Qinghai Province.

Hydrochemical characteristics and salinity formation mechanism of different water bodies in the southern Tibet, China.

Understanding the hydrochemical evolution of surface water and groundwater is crucial for protecting regional ecological environments. Currently, there are few quantitative studies on the relative contributions of different processes to salinity enrichment of water bodies. In this study, sixty-seven water samples were collected for chemical, and isotopic analysis, along with simulation calculations. The results reveal distinct hydrochemical types of river water, phreatic water, lake water and hot spring water in the investigated area are Ca-Mg-HCO3, Na-Ca-HCO3, Na-SO4-HCO3 and Na-HCO3, respectively. Average temperature and depth of geothermal water storage are 196℃ and 1338m, respectively. Average arsenic (As) content in hot spring water (298μg/L) higher than that in lake water (39.2μg/L), river water (9.59μg/L) and phreatic water (4.02μg/L). The ∑REEs content of river water in the study area is much higher than that of phreatic water and lake water. Result of δD and δ18O indicate that atmospheric precipitation is the source of recharge for all water bodies in the study area. Quantitative calculations indicate that evapo-concentration significantly enriches lake water salinity, contributing on average 90% of its salt content. In contrast, mineral dissolution contributes predominantly to the salinity of hot spring water (90.7%), phreatic water (65.8%), and river water (45.2%). Evapo-concentration emerges as the dominant mechanism for lake water salinity, while carbonate mineral dissolution primarily affects river water. Phreatic water and hot spring water are mainly controlled by the weathering and dissolution of silicate. The results can provide a theoretical basis for the study of the formation mechanism of water salinity in other regions with similar geological environment in the world.

Genomic Characterization of Bacillus sp. THPS1: A Hot Spring-Derived Species with Functional Features and Biotechnological Potential

Bacillus sp. THPS1 is a novel strain isolated from a high-temperature hot spring in Thailand, exhibiting distinctive genomic features that enable adaptation to an extreme environment. This study aimed to characterize the genomic and functional attributes of Bacillus sp. THPS1 to understand its adaptation strategies and evaluate its potential for biotechnological applications. The draft genome is 5.38 Mbp with a GC content of 35.67%, encoding 5606 genes, including those linked to stress response and sporulation, which are essential for survival in high-temperature conditions. Phylogenetic analysis and average nucleotide identity (ANI) values confirmed its classification as a distinct species within the Bacillus genus. Pangenome analysis involving 19 others closely related thermophilic Bacillus species identified 1888 singleton genes associated with heat resistance, sporulation, and specialized metabolism, suggesting adaptation to nutrient-deficient, high-temperature environments. Genomic analysis revealed 12 biosynthetic gene clusters (BGCs), including those for polyketides and non-ribosomal peptides, highlighting its potential for synthesizing secondary metabolites that may facilitate its adaptation. Additionally, the presence of three Siphoviridae phage regions and 96 mobile genetic elements (MGEs) suggests significant genomic plasticity, whereas the existence of five CRISPR arrays implies an advanced defense mechanism against phage infections, contributing to genomic stability. The distinctive genomic features and functional capacities of Bacillus sp. THPS1 make it a promising candidate for biotechnological applications, particularly in the production of heat-stable enzymes and the development of resilient bioformulations.

Characterization by 16S Amplicon Sequencing of Bacterial Communities Overall and During the Maturation Process of Peloids in Two Spas of an Italian Thermal Complex

Peloids are made by mixing clay materials with thermo-mineral waters, enriched with organic substances from microorganisms during maturation. Their beneficial properties may depend on clay minerals, water characteristics, and microbial components, although strong evidence is lacking. Next Generation Sequencing (NGS) allows a comprehensive approach to studying the entire microbial community, including cultivable and uncultivable bacteria. Our study aims to characterize, by NGS, the bacterial community overall and during the maturation process of thermal muds in two spas (A-B) of an Italian thermal complex. Peloids were produced from sulfurous-bromine-iodine thermal water and clay material: natural mud for spa A and sterile clay for spa B. Thermal waters and peloids at different maturation stages (2/4/6 months) were analyzed for microbiome characterization by 16S amplicon sequencing. Biodiversity profiles showed a low level of similarity between peloids and water used for their maturation. Peloids from spa A showed greater microbial richness than those from spa B, suggesting that natural mud with an existing bacterial community leads to greater biodiversity than sterile clay. Genera involved in sulfur metabolism were prevalent in both spas, as expected considering peloids matured in sulfide-rich water. For all three maturation stages, the prevalent genera were Thiobacillus and Pelobacter in spa A and Thiobacillus, Thauera, Pelobacter, and Desulfuromonas in spa B. Richness and diversity indices showed that the community seemed to stabilize after 2–4 months. The 16S amplicon sequencing to study bacterial communities enables the identification of a biological signature that characterizes a specific thermal matrix, defining its therapeutic and cosmetic properties. The bacterial composition of peloids is affected by the thermal water and the type of clay material used in their formulation and maturation.

Biodegradation of different keratin waste by newly isolated thermophilic Brevibacillus gelatini LD5: Insights into the degradation mechanism based on genomic analysis and keratin structural changes.

Keratin is an abundant environmental solid waste. This work isolated a thermophilic strain from a hot spring with efficient keratinolytic ability. The strain was identified and named as Brevibacillus gelatini LD5 based on whole-genome sequence analysis. The strain has genes related to keratin degradation, including disulfide reduction, keratin denaturation, protein proteolysis and metabolism of amino acids. The keratinases derived from this strain were the endo-acting M4, M16 and S8 proteases, exo-acting S9 protease and oligo-acting M3 and M32 peptidases via Conserved Unique Peptide Patterns (CUPP) prediction. The LD5 can degrade different keratin biomass, e.g. chicken feathers (CF), goose feathers (GF), pig hair (PH), cat hair (CH) and dog hair (DH). The degradation rate of CF was 62.45% after 24-h fermentation. The hydrolysates from different keratin biomass have all shown keratinolytic activity, antioxidant and antiradical activities. The random structure of keratin was easier to be degraded by LD5 from Fourier transform infrared (FT-IR) analysis. The optimum temperature-pH conditions of the keratinases were 79.8°C and pH7.5, and thermal stability of the keratinases reached 71.5min at 70°C. These results demonstrated that B. gelatini LD5 has potential application in keratin wastes biodegradation and thermal stable keratinase production.

Warm Spring Days are Related to Shorter Durations of Reproductive Phenophases for Understory Forest Herbs.

As plants continue to respond to global warming with phenological shifts, our understanding of the importance of short-lived heat events and seasonal weather cues has lagged relative to our understanding of plant responses to broad shifts in mean climate conditions. Here, we explore the importance of warmer-than-average days in driving shifts in phenophase duration for spring-flowering woodland herbs across one growing season. We harnessed the combined power of community science and public gardens, engaging more than 30 volunteers to monitor shifts in phenology (documenting movement from one phenophase to the next) for 198 individual plants of 14 species twice per week for the 2023 growing season (March-October) across five botanic gardens in the midwestern and southeastern US. Gardens included the Holden Arboretum, Kirtland, OH; Dawes Arboretum, Newark, OH; Chicago Botanic Garden, Glencoe, IL; Missouri Botanical Garden, St. Louis, MO; and Huntsville Botanical Garden, Huntsville, AL. We tested: (1) that higher-than-average daily temperatures (deviation from 30-year historical mean daily temperatures for each location) would be related to truncated phenophase durations; and (2) that phenophase durations would vary among species. Our findings support both hypotheses. We documented significant inverse relationships between positive deviations in daily temperature from historic means (e.g., warmer-than-average days) and durations of three reproductive phenophases: "First Bud," "First Ripe Fruit," and "Early Fruiting." Similar (non-significant) trends were noted for several other early-season phenophases. Additionally, significant differences in mean phenophase durations were detected among the different species, although these differences were inconsistent across plant parts (vegetative, flowering, and fruiting). Results underscore the potential sensitivity of understory herb reproductive phenophases to warmer-than-average daily temperatures early in the growing season, contributing to our understanding of phenological responses to short-term heat events and seasonal weather cues.

HEAT TRANSFER IMPROVEMENT FOR A FILLED-TYPE COMPOUND PARABOLIC SOLAR COLLECTOR WITH U-TUBE: ENERGETIC AND ECONOMIC ANALYSIS

In this study, the thermal and economic performance of a compound parabolic collector (CPC) with a U-tube was evaluated. Different filling fluids of the evacuated tube and different mass flowrates were evaluated. A detailed analysis of the energy performance of the collector components was conducted, along with an evaluation of its optical and economic aspects. The evaluated collector presented an optical efficiency of about 63.6%. Air achieved the highest evacuated tube temperature (160.6 ºC), followed by thermal oil (84.6 ºC) and water (61.3 ºC). The increase in HTF mass flowrate reduced both temperature gain and thermal efficiency. Thermal oil demonstrated superior thermal performance, achieving 32.5% higher efficiency than air and 30.0% higher than water. Results showed the thermal oil as the most cost-effective fluid, with a leveled cost of heat of 0.034 $/kWh and a simple payback period of 2.8 years. These findings demonstrate the potential of CPC systems for efficient thermal energy applications, with thermal oil emerging as the optimal filling fluid for both thermal and economic performance. Additionally, this study provides valuable practical insights for designing more efficient and sustainable CPC-based solutions for thermal energy applications.

Data Visualisation To Understand How Data Is Structured Using K-Means And Hierarchical Cluster Analyses With Interactive Graphics

This study examines the structure of geothermal geochemisty data in India using k-means and hierarchical cluster analyses. The first attempt to list hot springs in India was made by Schlagintweit in 1852. The Geological Survey of India published a special publication titled 'Geothermal Atlas of India', and the government of India constituted a 'Hot Spring Committee' to examine the possibility of developing geothermal plants for power generation and other uses. In the Puga valley and Parvati projects, it is estimated that it is possible to harness 5000 MWh of geothermal energy from Puga valley, sufficient to sustain a 20 MWe power plant. The GSI, the repository of most information concerning geological and related data in the country, included an R&D item No. 7/WB-5 for the development of a computerised system of geothermal database system referred to as GTHERMIS in its field season 1993-94 program. The computational strategy involves assigning each data point to the cluster with the nearest center (or "centroid"), recalculating the centroids after each assignment, and repeating the procedure until the clusters are no longer statistically different. The k-means method, developed by MacQueen (1967), is one of the most widely used non-hierarchical methods, particularly suitable for large amounts of data. The data is scaled before cluster analysis, and the results are visualized using interactive graphics.

Optimizing conical solar still performance: The impact of broken glass color on distillate yield, energy, exergy efficiency, and economic viability

This study investigates the effects of incorporating broken glass waste of varying colors: brown, green, blue, and transparent on the thermal efficiency, water yield, and economic performance of conical solar stills (CSSs). A conventional conical solar still (CCSS) was modified with each color of broken glass in the basin, with experiments conducted over two days in August 2024 in El Oued, Algeria. On the first day, the performance of CSSs with brown (CSS-BG-Br) and green (CSS-BG-Gr) broken glass was compared to the CCSS. On the second day, CSSs with blue (CSS-BG-Bl) and transparent (CSS-BG-Tr) broken glass were evaluated. The cumulative daily distillate yields achieved were 4.90, 7.20, 6.80, 6.45, and 6.10 L/m2/day for the CCSS, CSS-BG-Br, CSS-BG-Gr, CSS-BG-Bl, and CSS-BG-Tr, respectively. The corresponding yield improvements were 46.94 %, 38.77 %, 31.63 %, and 24.49 % for brown, green, blue, and transparent glass, respectively. Results indicate that brown and green glass provide substantial enhancements in thermal performance and distillate yield, with brown glass achieving the highest productivity. Economic analysis shows that CSS-BG-Br achieved the lowest cost per liter of distilled water and a payback period of just 22 days. This study highlights the potential of using colored broken glass, particularly brown, as an eco-friendly and economical material to enhance solar still performance, offering a sustainable solution for water production in arid regions.

Alkalothermophilic Iron-Reducing Bacteria of the Goryachinsk Thermal Water Basin

A study of iron-reducing prokaryotes that use the poorly crystalline mineral ferrihydrite as an electron acceptor revealed their widespread occurrence on the planet. However, the ability of iron reducers to develop under polyextreme conditions (at elevated values of pH and temperature) has not been previously demonstrated. To confirm the existence of alkalothermophilic iron reducers, we studied the water and sediment samples from the Goryachinsk nitrogen-rich thermal water basin. These springs are associated with young tectonic fractures in the Baikal rift zone; their water is characterized by low salinity, alkaline pH (8.8‒9.2) and temperature of 53‒55°C. Enrichment cultures reducing synthesized ferrihydrite were obtained by adding this mineral to the water and sediment samples from the Goryachinsk thermal springs, followed by anaerobic incubation at 50 and 55°C. The 16S rRNA gene profiling of the water and sediment samples and of the primary enrichment cultures revealed high taxonomic diversity, almost exclusively represented by bacterial taxa. Subsequent transfers with ferrihydrite and organic acids or hydrogen as electron donors resulted in stable enrichment cultures of organo- and lithotrophic alkalothermophilic iron reducers. Members of the genus Parvivirga, one of the first cultured representatives of the OPB41 group (now the order Anaerosomatales, phylum Actinomycetota), constituted 30 to 50% of the total abundance.

Population genomics of a thermophilic cyanobacterium revealed divergence at subspecies level and possible adaptation genes

BackgroundCyanobacteria are diverse phototrophic microbes with ecological importance and potential for biotechnology applications. One species of thermophilic cyanobacteria, Thermosynechococcus taiwanensis, has been studied for biomass pyrolysis, estrogen degradation, and the production of bioethanol, monosaccharide, and phycocyanin. To better understand the diversity and evolution of this species, we sampled across different regions in Taiwan for strain isolation and genomic analysis.ResultsA total of 27 novel strains were isolated from nine of the 12 hot springs sampled and subjected to whole genome sequencing. Including strains studied previously, our genomic analyses encompassed 32 strains from 11 hot springs. Genome sizes among these strains ranged from 2.64 to 2.70 Mb, with an average of 2.66 Mb. Annotation revealed between 2465 and 2576 protein-coding genes per genome, averaging 2537 genes. Core-genome phylogeny, gene flow estimates, and overall gene content divergence consistently supported the within-species divergence into two major populations. While isolation by distance partially explained the within-population divergence, the factors driving divergence between populations remain unclear. Nevertheless, this species likely has a closed pan-genome comprising approximately 3030 genes, with our sampling providing sufficient coverage of its genomic diversity. To investigate the divergence and potential adaptations, we identified genomic regions with significantly lower nucleotide diversity, indicating loci that may have undergone selective sweeps within each population. We identified 149 and 289 genes within these regions in populations A and B, respectively. Only 16 genes were common to both populations, suggesting that selective sweeps primarily targeted different genes in the two populations. Key genes related to functions such as photosynthesis, motility, and ion transport were highlighted.ConclusionsThis work provides a population genomics perspective on a hot spring cyanobacterial species in Taiwan. Beyond advancing our understanding of microbial genomics and evolution, the strains collected and genome sequences generated in this work provide valuable materials for future development and utilization of biological resources.

Iron sulfide-catalyzed gaseous CO2 reduction and prebiotic carbon fixation in terrestrial hot springs

Understanding abiotic carbon fixation provides insights into early Earth’s carbon cycles and life’s emergence in terrestrial hot springs, where iron sulfide (FeS), similar to cofactors in metabolic enzymes, may catalyze prebiotic synthesis. However, the role of FeS-mediated carbon fixation in such conditions remains underexplored. Here, we investigate the catalytic behaviors of FeS (pure and doped with Ti, Ni, Mn, and Co), which are capable of H2-driven CO2 reduction to methanol under simulated hot spring vapor-zone conditions, using an anaerobic flow chamber connected to a gas chromatograph. Specifically, Mn-doped FeS increases methanol production five-fold at 120 °C, with UV−visible light (300–720 nm) and UV-enhanced light (200–600 nm) further increasing this activity. Operando and theoretical investigations indicate the mechanism involves a reverse water-gas shift with CO as an intermediate. These findings highlight the potential of FeS-catalyzed carbon fixation in early Earth’s terrestrial hot springs, effective with or without UV light.

Enhancing the solar still performance with nano-coated seashells and surface-modified absorber plates for clean water production

The study focuses on enhancing the thermal efficiency and water productivity yield of a double slope solar still (DSSS) by integrating a roughened corrugated copper plate, and nano-coated seashells. The surface-modified absorber plate, combined with small and larger-sized conch shells, intends to enhance thermal absorption, thermal transfer, and water evaporation. Four different SS are considered in this study, namely (i) CSS, (ii) corrugated absorber plate with shot blasting (CSBSS) (iii) corrugated absorber plate with small conch shell (CSBSSS), and (iv) corrugated absorber plate with big conch shell (CSBBSS) incorporated SS. The corrugation process and the conch shells’’ addition enhance the absorption, improving heat transfer, maintaining water temperature, reducing heat loss, promoting efficient water evaporation, and augmentation of durability and adaptability of the solar still system. The increased heat flux was observed in the corrugated copper plate (6400.7 W/m2), compared with the flat plate (4723.8 W/m2), suggests that the corrugated design is more capable of capturing and transmitting solar energy effectively through ANSYS software. The daily productivity of CSS was 1468 ml/m2/day, and CSBSS achieved 1708 ml/m2/day. Promoting the implementation of corrugation and the integration of conch shells, CSBBSS and CSBSSS systems exhibited improved yields, reaching 2002 and 2193 ml/m2/day, respectively. CSBSS, CSBSSS, and CSBBSS showed thermal efficiencies surpassing CSS by 6.41 %, 35.53 %, and 24.48 %, respectively. The average exergy efficiencies attained for CSS, CSBSS, CSBSSS, and CSBBSS were 1.653 %, 2.451 %, 3.91 %, and 3.29 %, respectively at an 8 % interest rate.

Transient heat transfer analysis of airflow in a thermal water-bearing tunnel considering airflow turbulence and surrounding rock seepage effects

In deep tunnels traversing fractured water-rich strata, surface water descend, heats up at depth, and then rises into the tunnel, resulting in a ‘thermal water-bearing’ tunnel. This paper investigates the transient temperature evolution of such tunnels through laboratory-scale model experiment and numerical simulation, considering the convective heat transfer of thermal water in the surrounding rock. The experimental model was designed using similarity criteria derived from the equation analysis method. The 3D numerical model simulates the interaction between thermal water-saturated surrounding rock and tunnel airflow. The thermal field of the surrounding rock accounts for the coupling effects of the flow field, which follows Darcy's law. The tunnel airflow is governed by the RANS (Reynolds-Averaged Navier-Stokes) equations and the k−ω turbulence model, combined with the LRNM (Low-Reynolds Number Modeling) method for near-wall treatment. This approach is coupled with the energy balance equation to calculate the airflow temperature. The numerical model is validated using monitoring data from experimental measurements of grouted tunnel wall and airflow temperatures. Finally, parameter studies are conducted for both ungrouted and grouted tunnels, demonstrating the effectiveness of grouting in controlling airflow temperature by blocking thermal water.