Decrease In Water Temperature Research Articles

Water-surface photovoltaic systems have affected water physical and chemical properties and biodiversity

The implementation of water-surface photovoltaic systems as a source of renewable power has expanded rapidly worldwide in recent decades. Water-surface photovoltaic avoids negative impacts on terrestrial ecosystems, while the impacts on aquatic physical and chemical properties and biodiversity are unclear. To understand the ecological and environmental impacts of water-surface photovoltaic systems, here we conducted a field survey on water physical and chemical properties, plankton and bird communities of 26 water-surface photovoltaic systems in the Yangtze River basin in China during the winter and summer of 2022. We found that water-surface photovoltaic systems decreased water temperature, dissolved oxygen saturation and uncovered area of the water surface, which caused a reduction in plankton species and individual density, altering the community composition. Water-surface photovoltaic systems also caused an overall decrease in bird diversity and changed bird community compositions. These findings suggested that water-surface photovoltaic systems have impacts on the water environment and ecology. Since water-surface photovoltaic systems will continue to expand in the future, our results emphasize that rational planning is critical for the sustainable development of water-surface photovoltaic systems and the protection of the aquatic environment and biodiversity.

Influence of water saliny changes on the operation of the RAS biological treatment system under low temperature conditions

In fish-breeding circulation systems the change-over of a biofilter from operation in fresh water conditions to sea water conditions (or vice versa) requires a smooth gradual transition. However, a one-time water change is feasible faster and technologically easier. This determined the relevance of the study. The goal was to determine the influence of one-time water salinity changes (sea to fresh and fresh to sea) on the ability of the activated sludge biocenosis of biofilters to maintain or restore its activity in a cold-water RAS. Six model biofilters were filled with sea water and six with fresh water. With a simultaneous decrease of water temperature from 21 to 9 °C, at the first stage a start-up period of biological treatment was carried out. At the second stage — in a stable operating regime, sea water was simultaneously changed to fresh water, and fresh water to sea water. Concentrations of ammonium, nitrites and nitrates were determined at the start of experiment, then on the next day after a bacterial culture and ammonia as a source of ammonium nitrogen adding, and then — 2 times a week. A steady decrease in the concentration of ammonium in water to 0.2 mg/l, nitrite — to 0.3 mg/l was considered as the indicator of the end of each stage. The duration of the start period of biological treatment in both fresh and sea water was approximately the same and amounted to 138 and 134 days, respectively. With the simultaneous change of sea water to fresh or fresh water to sea, the complete destruction of the biofilter activated sludge biocenosis didn’t happen, that indicated by the continuing increase of the nitrates concentration. However, the ability of the biofilter biocenosis to purify circulating water from ammonia nitrogen and nitrites naturally decreases with the following gradual performance restoration. The adaptation of biofilter biocenosis to work under conditions of rapid desalination was 1.5 times faster than the adaptation of biocenosis to rapid salination.

Late-stage evolution of hypogene caves at Tyuya-Muyun (Kyrgyzstan): Quantitative insights from mineral deposits

The Tyuya-Muyun massif in SW Kyrgyzstan hosts a number of caves some of which contain Ra- and U-bearing minerals that were extensively mined in the early 20th century. Previous studies have suggested that the caves of the Tyuya-Muyun have experienced a complex speleogenetic history, including epigene and hypogene processes. Here, we reconstruct the late stages of hypogene processes by studying subaqueous (calcite and barite spars, cave clouds), near-water table (rafts, folia) and vadose (flowstone) mineral deposits in Great Barite and Surprise caves. We determined the chronology (230Th dating), stable isotope composition (δ18O, δ13C and Δ47), and formation temperature (fluid inclusion microthermometry and Δ47) of these minerals and reconstructed the oxygen isotopic composition of the paleo-water (δ18Ow). In contrast to previous hypotheses about cave evolution, we found no evidence of an initial epigenic karst phase. The earliest mineral deposits suggest already hydrothermal conditions, with calcite and barite forming at ~40–50 °C prior to 600 ka. Cave clouds in Great Barite Cave mark the beginning of the lowering of the groundwater table and also record a decrease in water temperature from 29.7 ± 8.3 °C to 12.7 ± 5.6 °C, as shown by Δ47 thermometry. The latter temperature remained stable, within analytical uncertainties, during the past 600 ka, as indicated by Δ47 results of near-water table and vadose speleothems in Surprise Cave. At the same time, the decrease in δ18Ow suggests a reduced contribution of thermal water and an increased input of colder meteoric water. By around 540–450 ka Surprise Cave emerged from the phreatic zone, as indicated by 230Th ages of the highest folia and flowstone. This lowering of the water table continued until 84 ka and may have been related to the final uplift phase of the Tyuya-Muyun massif and the concomitant incision of the Aravan River forming the Dangi Gorge.

Biological traits of a commercial mussel species Mytilus platensis from the South Atlantic Ocean: Environmental drivers affecting on its intertidal population

Population density, morphometric relationships, maximum age and shell growth rate were studied in an intertidal commercial mytilid species, the blue mussel Mytilus platensis d’Orbigny, 1842, at Villa Gesell (37° 15′S; 56° 57′W), Argentina, Southwest Atlantic Ocean. The population density and mean shell length showed variation across the year, i.e., the month with the highest density (December) was mostly characterized by smaller sized individuals, representing the newly settled recruits during the austral summer months. Shell cross sections and acetate peels of M. platensis revealed an internal shell growth pattern alternating broad opaque and narrow translucent bands, corresponding to fast and slow-growing periods, respectively. Translucent bands representing external rings were formed mostly during July, coinciding with a decrease in sea water temperature (austral winter) and gonadal maturation processes. Data confirmed the annual formation of translucent bands in this species, showing a maximum age of 8 years. The generalized von Bertalanffy growth curve showed values of SL∞ = 38.46 mm, k = 0.28 yr−1 and t0 = −0.57 yr−1 (R2 = 0.80). Compared to studies of subtidal populations, lower shell growth rate in this intertidal population were observed, which may be associated with the stressful environmental conditions in this habitat, such as desiccation, exposure to waves and fluctuating sea water temperature. The characteristics described throughout the study highlight that the variability associated with intertidal environments could limit the sustainability of commercial exploitation of M. platensis in these ecosystems compared with conspecific subtidal populations.

Response of Water Temperature to Wind Speed and Air Temperature in Lake Laut Tawar, Aceh Province, Indonesia

Changes in water temperature impact the dynamics of lake ecosystems. Changing climate factors, including wind speed and air temperature, influence the water temperature of lakes. This research aims to analyze the response of water temperature to wind speed and air temperature in Lake Laut Tawar. Observations were conducted from August to September 2023, with a sampling frequency of every two weeks. The results revealed that water temperature, wind speed, and air temperature in Lake Laut Tawar fluctuated according to the presence of light, namely day and night factors. Variations in sunlight intensity lead to hourly fluctuations in air temperatures, while wind speeds vary hourly due to changes in air pressure, consequently resulting in hourly variations in water temperature as well. During daylight hours, air temperature surpasses water temperature, whereas during nighttime hours, water temperature exceeds air temperature. Heat transfer from the air to the water contributes to an increase in water temperature, while the release of heat energy from the surface water into the air leads to a decrease in water temperature. Changes in the water temperature of Lake Laut Tawar are primarily influenced by changes in wind speed and air temperature by 80 percent simultaneously. However, while air temperature showed a partial response, wind speed did not exhibit a significant response. The relationship between these variables can be expressed through a mathematical model Tw = 0.356 Ta + 0.025 W + 15.674, where Tw is water temperature (°C), Ta is air temperature (°C), and W is wind speed (km/minute). Another factor that influences the water temperature of Lake Laut Tawar is the inlet water temperature, which was not observed in this research.

Variations in Temperature and Pressure in the “Reservoir–Well” System Triggered by Blasting Recovery of Iron Ore at the Kursk Magnetic Anomaly

This paper presents the results of precise measurements of temperature and pore pressure in the “reservoir–well” system during the development of iron ore deposits of the Kursk Magnetic Anomaly (KMA) via blasting. For the observation period from October 2021 to June 2024, variations in compressibility, permeability and temperature in the upper Albian-Cenomanian confined aquifer, which is used for district water supply, were determined. The general trend in a decrease in water temperature was traced (from 12 °C to 11.4 °C). It was accompanied by an increase in the hydrostatic head (from 3.7 m to 7.4 m). Water temperature in the upper aquifer was measured for 9 industrial explosions in the mine and for 30 explosions in the quarry. For one explosion in the mine and five explosions in the quarry the coseismic changes in water temperature with amplitudes of 0.06–0.09 °C were established, while changes in pore pressure in the “reservoir–well” system were 0.4–2.2 kPa. Local changes in the permeability of the reservoir in the vicinity of the well (the skin effect) are considered to be the main factor that controls the coseismic response of temperature during industrial explosions. As the reservoir permeability increases, the water temperature in the “reservoir–well” system can decrease and vice versa. The same pattern was observed according to regime measurements performed in 2022–2023. The recorded coseismic responses of water temperature in the upper aquifer in the high-frequency range are similar to the effects observed during propagation of seismic waves originated from earthquakes in the low-frequency range at different sites all over the world for the seismic energy density of 0.05–0.45 J/m3. The observed variations in aquifer temperature in the “reservoir–well” system under episodic dynamic impacts are of particular interest from the point of view of activating hydrogeochemical processes that accompany the development of iron ore deposits.

Heat and Mass Transfer Model of Horizontal Tubular Absorbers for LiBr/H2O Absorption Refrigeration

This study delves into the absorption efficiency of a horizontal absorber using a LiBr-H2O solution. We developed a computationally fast and accurate two-dimensional model, which we validated against experimental data. The analysis focuses on key operational parameters such as solution inlet temperature, mass flow rate, and cooling water inlet temperature, revealing their intricate interplay and impact on absorption performance. Our findings highlight the substantial influence of cooling water temperature, showing a significant boost in absorption efficiency as the cooling water temperature decreases. Additionally, we explore the effects of solution mass flow rate, uncovering the delicate balance between increased heat transfer resistance and initial absorption efficiency at near the impingement region. This comprehensive study provides valuable insights into the dynamics of absorption systems, offering pathways to optimize design and operational strategies for enhanced performance.

Underwater temperature and pressure monitoring for deep-sea SCUBA divers using optical techniques

The safety of SCUBA divers remains at high risk in deep-sea owing to multiple factors such as dangerous surrounding, rely upon technical equipment necessary for life support, decreased underwater navigation, and communication infrastructure. Gradual decrease and increase in water temperature and pressure corresponding to depth are among the most common problems that cause most of the fatalities in deep-sea diving. Therefore, different gadgets for accurate measurement of vital parameters, reliable navigation, and seamless communication are of prime importance. In this paper, we propose an all-optical technique for local and remote monitoring of underwater temperature and pressure for deep-sea SCUBA divers based on fiber Bragg grating (FBG) sensors and underwater optical communication-single mode fiber (UWOC-SMF) integrated transmission system. The proposed technique is implemented using two FBG temperature and pressure sensors fixed over diver’s suit and UWOC-SMF integrated transmission system for simultaneous local and remote monitoring of underwater temperature and pressure. Remote monitoring of underwater temperature and pressure is achieved at ship station through a remotely operated underwater vehicle (ROV) and UWOC-SMF integrated transmission system by means of shifts in the original Bragg wavelengths of sensors due to temperature and pressure variations. The performance of the sensors is analyzed for pressure and temperature in the range of 0 to 6.4 MPa (≈0 to 655 mH2O) and 40 to −2°C, respectively corresponding to different depths. The results show that the proposed technique can work well in the deep ocean over a range of pressures and temperatures of 0–7 MPa and 40 to −2°C while achieving a temperature sensitivity of 4.3 p.m./°C and a pressure sensitivity of 30.5 p.m./MPa. Clear spectra of reflected signals from FBG sensors at ship station are achieved after signal transmission over UWOC-SMF hybrid link.

Experimental study on the influence of gas-blowing flow rate on the cold discharge characteristics of external ice-melting ice storage system

External ice-melting ice storage system has the advantage of fast cold discharge. However, the instability of outlet water temperature limits its practical application. In this paper, an experimental bench is built for testing cold discharge performance of the external ice-melting ice storage system combined with a gas-blowing device based on theoretical analysis. The influence of different gas-blowing flow rates on the vertical temperature distribution inside the ice storage tank, outlet water temperature, cold discharge rate, instantaneous cold discharge capacity, and total cold discharge capacity is analyzed and compared during the cold discharge process by experiments. The experimental results show that as the gas-blowing flow rate increases, the convective heat transfer between the water and ice in the water space of the ice storage tank is enhanced, the outlet water temperature decreases, and the cold discharge rate increases. Through comprehensive analysis, it is found that for a small external ice-melting ice storage system in this experiment, the outstanding comprehensive performance can be achieved with 1L/min gas-blowing flow rate, which. The average outlet water temperature during the latent heat phase is 1.9 °C lower and the cold discharge rate is 34.8 % higher than that without gas blowing.

Shallow estuarine reef as nursery habitat for Australasian snapper (Chrysophrys auratus)

ABSTRACT Estuaries are important recruitment sites for many fish species, with structurally-complex habitats such as subtidal seagrass beds on soft sediments particularly valuable due to their provision of food and shelter. Soft sediments dominate most estuaries, but where hard-bottom reefs are present they have the potential to act as nursery habitats for juvenile fish. We document recruitment of juvenile Australasian snapper (Chrysophrys auratus) to a shallow linear sandstone reef in Whangateau Harbour, a small estuary in north-eastern New Zealand. Up to several hundred 0 + juveniles (∼20–70 mm fork length) were present on the reef during early summer to mid-late autumn each year from 2018 to 2021. Numbers were consistently highest at the seaward end of the reef, facing into incoming tidal currents, and lowest in the deeper central part of the reef, where larger, potentially cannibalistic, snapper were common. Juveniles disappeared from the reef fairly abruptly at the end of each season, with departure in at least two of the years appearing to follow a sudden decrease in water temperature rather than being associated with body size or absolute temperature. Although relatively small in area, estuarine reefs may be increasingly important nursery habitats in the future given the widespread loss of subtidal seagrass beds.

Physiological adaptations to semi‐aquatic habits: the thermogenic macronutrient intake of the Eurasian otter

Abstract Maintaining thermal homeostasis in water is a major challenge for semi‐aquatic mammals, which entails morphological, behavioural and physiological adaptations. Foraging strategies and dietary‐induced thermogenesis (DIT) contribute to regulating body temperature in cold environments. As DIT differs among macronutrients, semi‐aquatic mammals may be expected to regulate their macronutrient ratios to enhance their capability of thermoregulating. We estimated the nutritional intake target of a widespread semi‐aquatic mustelid, Eurasian otter Lutra lutra by reviewing the available literature on otters' diet throughout Europe and assessing the nutritional composition of non‐commercial fish species forming the bulk of otter diet through laboratory analyses. The macronutrient intake target for the otter was assessed as 61% protein and 39% lipid energy ratios. The mean percent protein energy was higher than that reported for typical hypercarnivores and tended to increase with decreasing water temperatures. The additional source of heat provided by the thermogenic effect induced by protein digestion may contribute to balance heat loss, compensating for the costs associated with protein overconsumption. If, as suggested by fossil records, semi‐aquatic habits appeared after the development of otter's ‘fish specialist’ dentition, the thermogenic effect of its fish‐based diet may have promoted the tight relationship occurring between otters and water habitats.

Effect of rainfall in shaping microbial community during Microcystis bloom in Nakdong River, Korea

Various environmental factors play a role in the formation and collapse of Microcystis blooms. This study investigates the impact of heavy rainfall on cyanobacterial abundance, microbial community composition, and functional dynamics in the Nakdong River, South Korea, during typical and exceptionally rainy years. The results reveal distinct responses to rainfall variations, particularly in cyanobacterial dominance and physicochemical characteristics. In 2020, characterized by unprecedented rainfall from mid-July to August, Microcystis blooms were interrupted significantly, exhibiting lower cell densities and decreased water temperature, compared to normal bloom patterns in 2019. Moreover, microbial community composition varied, with increases in Gammaproteobacteria and notably in genera of Limnohabitans and Fluviicola. These alterations in environmental conditions and bacterial community were similar to those of the post-bloom period in late September 2019. It shows that heavy rainfall during summer leads to changes in environmental factors, consequently causing shifts in bacterial communities akin to those observed during the autumn-specific post-bloom period in typical years. These changes also accompany shifts in bacterial functions, primarily involved in the degradation of organic matter such as amino acids, fatty acids, and terpenoids, which are assumed to have been released due to the significant collapse of cyanobacteria. Our results demonstrate that heavy rainfall in early summer induces changes in the environmental factors and subsequently microbial communities and their functions, similar to those of the post-bloom period in autumn, leading to the earlier breakdown of Microcystis blooms.

Comparative transcriptomic analysis of the brain-liver Axis reveals molecular mechanisms underlying acute cold stress response in Gynogenetic Mrigal carp

In this study, we produced a population of gynogenetic mrigal carp (Cirrhinus mrigala, GMCJ) through artificial gynogenesis using UV-inactivated white crucian carp spermatozoa. The GMCJ exhibited a faster growth rate and strong resistance to low temperatures, surviving natural winter conditions with temperatures below 10 °C. To gain a deeper insight into GMCJ's molecular response to acute cold stress (a decrease in water temperature from 26 °C to 14 °C within 1 h at a rate of 0.2 °C/min), we conducted a comparative analysis of the histology and transcriptomics of the brain-liver axis. Transmission electron microscopy of the heart tissues revealed that acute cold stress result in widened myofilament spacing, along with enlarged, deformed mitochondria that developed vacuoles and ruptured. We identified differentially expressed genes (DEGs) in the brain (2463 upregulated and 3288 downregulated genes) and liver (1210 upregulated and 1224 downregulated genes). Analysis of the DEGs' correlations indicated that major pathways involved in immunity, disease, metabolism, and growth were active and interconnected. KEGG functional analysis showed that the most enriched pathways in the brain-liver axis involved the regulation of the glucagon pathway, PI3K-Akt signaling pathway, and herpes simplex infection. Numerous genes associated with the nervous-endocrine system were activated, suggesting a coordinated response of the brain-liver axis to acute stress. These findings enhance our understanding of how farmed, particularly gynogenetic fish respond to acute cold stress.

Factors influencing migration of short-finned eels (Anguilla australis) over 3 years from a wetland system, Lake Condah, south-east Australia, downstream to the sea.

Anguillid eel populations are under threat globally. A particularly vulnerable life-cycle stage is the migration of mature adult eels downstream from freshwater habitats through estuaries into the sea to spawn. This study investigated the factors associated with downstream migration of the short-finned eel Anguilla australis (Richardson 1841) from a coastal wetland (Lake Condah) in south-east Australia, using acoustic telemetry. Migration was associated with time of the year, higher water level and river flows, decreasing water temperature, and darker moon phases. Larger individuals and those in better condition were more likely to migrate from the wetland. Downstream migration peaked in spring, in contrast to the typical autumn migration period for other temperate anguillids. Variable responses, in comparison to other studies, highlight how migration cues may not be universal. In south-east Australia, short-finned eels may have evolved to migrate in multiple phases by first migrating to the estuary during typical seasonal spring flow pulses (e.g., to avoid being stranded in upland reaches during dry summer periods) and then migrating into the ocean in autumn. More research is needed to unravel these processes and causes, especially considering that the relationship between migration and hydrology may be complex and confounded (e.g., by human-induced disruptions to migratory pathways).

Unusual weakening trend of the East Asian winter monsoon during MIS 8 revealed by Chinese loess deposits and its implications for ice age dynamics

A fundamental aspect of marine benthic foraminiferal δ18O records of the last one million years is their “saw-tooth” pattern, characterized by gradual cooling to full glacial conditions followed by very rapid glacial terminations. Understanding the mechanism of this pattern is crucial for understanding ice age dynamics. We investigated the climatic trend within each glacial of the last 880 kyr by comparing the signal of the East Asian winter monsoon (EAWM) with global terrestrial and marine paleoclimate records. Our new grain size record from the Huining loess-paleosol section in the western Chinese Loess Plateau, together with published climate records from the Yimaguan and Luochuan sections in the central Chinese Loess Plateau, demonstrates a strengthening trend of the EAWM within most glacials, which largely mirrors the “saw-tooth” pattern of the benthic foraminiferal δ18O record. However, the EAWM record during Marine Isotope Stage (MIS) 8 shows an unusual weakening trend which is the exception over the last 880 kyr. Based on the linkages between Arctic ice sheets, the Siberian High Pressure system, and the EAWM, we propose that the weakening trend of the EAWM throughout MIS 8 reflects the overall shrinking of Arctic ice sheets towards the glacial termination, in contrast to the increasing trend of the benthic foraminiferal δ18O values. This conclusion is supported by a compilation of global paleoclimate records suggesting that MIS 8 was a unique glacial period over the last 900 kyr, characterized by a mild climate in middle to high northern latitudes and a cold climate in high southern latitudes, during late MIS 8. The inferred changes in Arctic ice sheets would alone cause a decreasing trend in benthic foraminiferal δ18O values during MIS 8, which is the opposite to the observed trend. We suggest that an increased ice volume in high southern latitudes led to the cooling of Antarctic Bottom Water and hence to a decrease in ocean bottom water temperature with an effect to increase benthic foraminiferal δ18O during MIS 8 as observed. Our results highlight the complexity of using the benthic δ18O signal alone as a paleoclimate proxy, and that MIS 8 is an important time window for better understanding glacial dynamics driven by changes in the polar regions of both hemispheres.

Current state of juvenile roach (Rutilus rutilus caspicus)

Fluctuations in water temperature in the Northern Caspian Sea, especially in the shallow zone, are mainly due to fluctuations in air temperature and during the trawling period, in the fall, the water temperature at observation stations showed a decrease in water temperature, which caused the formation of dense aggregations in juvenile roach. To study the nutritional status of juvenile fish living in the Kazakh part of the Caspian Sea, material was selected from different depths of the sea from trawl catches during comprehensive research in the fall of 2022. In the course of studies conducted to assess nutrition using quantitative and qualitative indicators, it was determined that the nutritional spectrum of juvenile roach in the water Caspian Sea is represented mainly by the same bottom organisms with a dominance of crustaceans, with their preference for bivalves, which give a good growth rate. A parasitological study of juvenile roach showed the absence of pathogen circulation in the ecosystem of this reservoir. Based on the results of pathomorphological studies of fish gills, it was found that fragmentary hyperplasia is caused by the presence of protozoal invasion rather than by the influence of environmental factors.

Cytogenetic Analysis of the Crustacean Pontogammarus robustoides (Amphipoda, Gammaridae) at Increased Water Temperature under Conditions of Microcosm

Adaptive reactions of <i>Pontogammarus robustoides</i>, a representative of the family Gammaridae, were studied at the cellular level at the increase in water temperature to its critical values under conditions of a model ecosystem - a microcosm. A cytogenetic analysis of its embryo cells was carried out and the activity of nucleoli of somatic cells was investigated. It has been shown that normal development of <i>P. robustoides</i> embryo cells was observed within the temperature range from 25.0°C to 27.5°C. The increase in water temperature up to 30.0-30.5°C resulted in such structural and functional changes in its cells as the increase in chromosome aberrations and the increase in the number of micronuclei. At the prolonged exposure to the increased water temperature, these indices approached critical levels. The number of embryo cells with nuclear fragmentation increased, which is evidence of the development of the processes directed to apoptosis. The destruction of embryo cell structures was registered at 32.0°C. The total volume of nucleoli in the somatic cells increased, which can be indicative of the increased synthesis of proteins probably involved in the processes of adaptation. A decrease in water temperature to the initial level of 25.0°C favored recovery of the structural and functional indices of Gammaridae genome. However, a high contribution of cell division disorders was still observed, which was accompanied by a significant decrease in the number of micronuclei.

Laboratory tests of the stability of disinfectants for different quality of water

The last water treatment process is disinfection and it has two purposes. The main purpose of disinfection is to kill or inactivate pathogens. A secondary purpose is to provide a residual disinfectant concentration in drinking water and to prevent microbial growth in water distribution systems. Although most pathogens (99 to 99.9%) are removed by coagulation, flocculation, sedimentation, and filtration, disinfection is a critical process for protecting the public from waterborne infections. Common disinfectants include chlorine gas, sodium hypochlorite, chloramines, chlorine dioxide, ozone and ultraviolet radiation. Each disinfection method has its advantages and disadvantages. Among the disadvantages of using sodium hypochlorite, in addition to the formation of disinfection by-products, the stability of the used agent is also important. Laboratory tests of the stability of disinfectants were carried out in drinking water of different quality depending on the pH value, water temperature and total water mineralization at different contact time in water (from 0 to 48 hours). To monitor the stability of disinfectants, chlorine-based disinfectants were selected, namely sodium hypochlorite prepared in the classic way and by electrolysis of brine. The stability of these disinfectants was verified in low-mineralized surface water from the Turček water reservoir, medium mineralized groundwater from the Sihot’ water source and groundwater from a private well in village of Ol’dza with highly mineralized water. Active chlorine doses in the range of 0.28-0.35 mg/L were used to verify the stability of sodium hypochlorite prepared in the classic way in selected drinking waters. When verifying the stability of sodium hypochlorite prepared by electrolysis of brine, doses of active chlorine in the range of 0.25-0.30 mg/L were applied. When verifying the stability of sodium hypochlorite produced by two different methods (chemical process, brine electrolysis), the dependence of the increasing stability of these disinfectants with a decrease in pH value and water temperature was demonstrated. The dependence of chlorine stability is significantly influenced by the water temperature, less so by the pH value of the water. Reaction kinetics of 0th, 1st and 2nd order was studied for better understanding of this process.

Experimental and heat transfer studies of MHP-PV/T by Reynolds number and heat transfer coefficient enhancement

The photovoltaic/thermal (PV/T) system, as an energy conversion system to generate electricity and heat, has great application potential in northwest zone of ample solar energy resource in China. The working media inside the micro heat pipe (MHP) of previous studies was acetone. Compared to acetone, R141b has better stability and lower solubility. For working fluid as R141b in the MHP, higher Reynolds Number (Re) theoretically means better heat transfer. During the typical winter season, when the inclination of the PV panel was 45°, the average power conversion efficiency (PCE) and thermal conversion efficiency (TCE) can reach 12.8 and 26.4 %. Furthermore, in order to reduce the simulation time and facilitate the research, the study establishes the fitting equation of MHP-PV/T surface temperature based on solar radiation intensity and environmental temperature with an average error of 7.6 %. Furthermore, a three-dimensional mathematical model of MHP-PV/T system was developed and validated with experimental results, investigating the Re of R141b in the MHPs and calculating the related heat transfer coefficient (h) based on Re. The simulation showed that the Re and h at the condensation section of the MHP were bigger than those at the evaporation section. The Re and h increased with the water temperature decrease of airfoil heat exchanger and solar radiation intensity rise. Lastly, when water temperature of airfoil heat exchanger was unchanged, the impact of solar radiation intensity on h was greater than Re. When the solar radiation intensity remained unchanged and the water temperature decreased, Re was the main reason for affecting the change of h. The research results will give a scientific foundation and technical application for the MHP-PV/T, as well as more efficient solar energy applications in the future.

A numerical study on oscillatory characteristics of unstable steam jet in water flow within a vertical pipe

In this study, a numerical investigation was conducted to examine the condensation and pressure oscillation characteristics of low mass flux steam jets in water flow within a vertical pipe under different operating conditions. Three bubble states were observed during the injection of subsonic steam in an upward direction into a subcooled water flow: bubble growth, bubble necking, and bubble detachment. Through a synchronously analysis of the bubble morphology and interface pressure, the oscillation mechanism of the unstable steam jet was revealed. The results showed that the pressure oscillation characteristics were consistent with the behavior of the vapor bubble. The frequency of pressure oscillation increased with the increase of steam inlet pressure and water Reynolds number, while decreased with the decrease of subcooled water temperature. The intensity of pressure oscillation exhibited a distinct peak at the position corresponding to the detachment of the primary and secondary bubbles. Moreover, a new predictive correlation for pressure oscillations in flowing water was presented by the frequency of steam injection, the condensation driving potential, the steam mass flux, the Weber number, and the water Reynolds number. The predicted values showed good agreement with the experimental values, with a maximum deviation of 24 %