Decrease In Water Temperature Research Articles

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.

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 %

Effect of acute temperature stress on energy metabolism, immune performance and gut microbiome of largemouth bass (Micropterus salmoides)

Frequent occurrences of extreme weather events, particularly severe temperature fluctuations, have significantly impaired the growth and health of fish and resulted in detrimental impacts on aquaculture production. Despite recognition of the crucial role that temperature plays in aquaculture, there is currently inadequate research to assess the consequences of extreme temperature fluctuations on fish health. Hence, we set up acute warming (AW) and cooling groups (AC) by increasing or decreasing water temperature by 8 °C and then gradually restoring the initial temperature (22 °C), to investigate the adaptive regulation of energy metabolism, immune function, and gut microbiota in largemouth bass (Micropterus salmoides). The fish antioxidant system responded to assist their environmental adaptation: both groups showed activation of serum superoxide dismutase (SOD) and catalase (CAT) secretion, and a significant increase in serum total antioxidant capacity (T-AOC) (P < 0.05). Distinct metabolic strategies were employed to cope with sudden environmental perturbations: upon experiencing a temperature decrease (AC1), largemouth bass exhibited a significant increase in serum triglyceride (TG) and cholesterol (CHOL) levels (P < 0.05), coupled with a reduction in blood glucose levels (P < 0.05). However, a considerable reduction in serum TG and CHOL levels was observed after acute warming stage (AW1) (P < 0.05). Following the recovery of temperature, both groups demonstrated a tendency towards normal energy metabolism (CON). Compared to the AW group, the immune function of largemouth bass in the AC group was dramatically affected: alkaline phosphatase (AKP), aspartate transaminase (AST), and alanine transaminase (ALT) increased significantly, while lysozyme (LZM) decreased significantly when the temperature dropped sharply (P < 0.05). After the temperature fluctuations, there were apparent changes in the gut morphology and microbiota of largemouth bass. Microbial functional analysis using the KEGG database revealed apparent alterations in microbial biological functions, especially during the cooling fluctuation (AC). The results indicated that dramatic weather changes, particularly extreme cold, may be detrimental to the health and welfare of largemouth bass.

Cold Stress Induces Apoptosis in Silver Pomfret via DUSP-JNK Pathway.

We cultured silver pomfret for 20 days, decreasing water temperature from 18 to 8 ℃, and sampled muscle every 5 days. Muscle fiber degeneration and apoptosis began to increase at 13 ℃ detected by HE and TUNEL staining. Further analysis of transcriptome revealed that several apoptosis-related pathways were highly enriched by differentially expressed genes (DEGs). We analyzed 10 DEGs from these pathways by RT-qPCR during the temperature-decreasing process. JNK1, PIDD, CytC, Casp 3, and GADD45 were up-regulated after 15 and 20 days, while DUSP3, JNK2, and PARP genes were down-regulated after 15 and 20 days. DUSP5 was up-regulated from 10 to 20 days, and C-JUN was up-regulated after 20 days. We analyzed apoptosis in PaM cells under different temperatures (26 ℃, 23 ℃, 20 ℃, 17 ℃, and 14 ℃). The cell viability significantly declined from 14 to 20 ℃; the TUNEL and IHC results showed that the apoptosis signal increased with the temperature dropping, especially in 17 ℃ and 14 ℃; DUSP5, JNK1, CytC, C-JUN, Casp 3, and GADD45 were up-regulated at 17 ℃ and 14 ℃, and PIDD was up-regulated at 20 ℃, 17 ℃, and 14 ℃. DUSP3 was up-regulated at 20 ℃ but down-regulated at 17 ℃ and 14 ℃, and PARP was down-regulated at 17 ℃ and 14 ℃. JNK2 was up-regulated at 20 ℃ but down-regulated at 17 ℃ and 14 ℃. Our results suggest that DUSP could help inhibit apoptosis in the initial stage of cold stress, but low temperature could down-regulate it and up-regulate JNK-C-JUN, inducing apoptosis in a later stage. These data provide a basis for the study of the response mechanism of fish to cold.

Discharge‐Mediated Temperature Management in a Large, Regulated River, With Implications for Management of Endangered Fish

AbstractFor large, regulated rivers, operators can impact abiotic conditions for the benefit of the ecosystem, primarily by controlling the volume of discharge from upstream reservoirs. Understanding the decision space around discharge is necessary for evaluating tradeoffs between environmental and other objectives. As a result of climate change, warming water temperatures are increasingly becoming a concern for thermally‐sensitive fauna. In California's largest river, the Sacramento, extinction risk of salmon populations is linked to high water temperatures. Yet, little is known about how much water temperature in lower reaches can be affected by reservoir discharge operations, and the potential benefits to salmon. We used a process‐based water temperature model to estimate the ability of reservoir discharge to mediate river temperature heating processes impacting downstream locations (discharge‐mediated temperature management). To bound this analysis, we used historical forcings over a recent 29‐year span. Results indicate reservoir discharge increases of up to 340 cms over the historical record could have decreased water temperature in the lower reaches by up to 3.6°C. Salmon require water below 20°C during most stages of their lifecycle, and we found that normative water operations could ensure 20°C was rarely exceeded for two potential management seasons, in late‐spring and early‐fall. These periods coincide with important rearing and migratory periods for salmon, during which they frequently experience excessive temperatures under the management status‐quo. This analysis provides stakeholders tools to manage conditions for native fauna in the face of a warming climate, and a framework for developing similar tools in other large, regulated rivers.

Evaluating Habitat Suitability and Tidal Wetland Restoration Actions With ECOSTRESS

AbstractAs temperatures rise, it is increasingly important to monitor changes in habitat conditions for aquatic species and mitigate emerging stressors. The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) instrument provides temperature products at a spatial and temporal scale not previously available. Here, we utilize ECOSTRESS temperature products to assess fluctuations in thermal habitat suitability for an endangered fish species and we also demonstrate the utility of the data set to assess water surface and bulk temperature changes following completion of two tidal wetland restoration efforts in the San Francisco Estuary and Sacramento–San Joaquin River Delta (Bay Delta). During all hours of the day throughout the 2018–2022 study period, key Delta Smelt habitat areas including Honker Bay, West Suisun Bay, and Mid Suisun Bay had greater than 75% of their areas suitable; there were several instances during which less than 25% of the area was thermally suitable generally coinciding with heatwave events. Overall, midday hours are less frequently suitable than morning and evening hours. Early evidence from ECOSTRESS indicates that there may be a decrease in surface water temperature of up to several degrees in tidal restoration areas, but more data is needed to show statistically significant outcomes. The ECOSTRESS record began in summer of 2018, and a longer record is needed to fully capture temperature changes associated with wetland processes and restoration efforts. Future applications of ECOSTRESS products can the capacity to help further understand ecosystem conditions and how restoration efforts affect water temperature, informing decisions that benefit Delta Smelt and other at‐risk aquatic species.

Betaproteobacteria are a key component of surface water biofilters that maintain sustained manganese removal in response to fluctuations in influent water temperature

The health risks associated with manganese (Mn) in drinking water, and an improved understanding of Mn accumulation within, and subsequent release from, distribution systems, have increased the need for robust, sustainable treatment options to minimize Mn concentrations in finished water. Biofiltration is an established and effective method to remove Mn in groundwater however, Mn removal in surface water biofilters is an emerging treatment process that has not been extensively studied. Seasonal variations in water temperature can present an operational challenge for surface water biofilters which may see reduced Mn removal under colder conditions. This study examined the microbiomes of surface water biofilters at three utilities (ACWD WTP, WTP B, and WTP D) which all experienced similar seasonal fluctuations in influent water temperature. High Mn removal was observed at the ACWD WTP for much of the year, but Mn removal decreased with a concurrent decrease in the influent water temperature (58% ± 22%). In contrast, both WTP B and WTP D achieved year-round Mn removal (84% ± 5% and 93% ± 8% respectively). Marker gene (16S rRNA) sequencing analysis of the biofilter microbiomes identified a high abundance of Betaproteobacteria in WTP B and WTP D (37% ± 12% and 21% ± 3% respectively), but a low abundance of Betaproteobacteria in the ACWD WTP (2% ± 2%). The microbiomes of new bench-scale biofilters, in operation at the ACWD WTP, were also investigated. The abundance of Betaproteobacteria was significantly greater (p < 0.05) after the biofilters had acclimated than before acclimation, and differential abundance analysis identified 6 genera within the Betaproteobacteria class were enriched in the acclimated microbiome. Additionally, the acclimated biofilters were able to maintain high Mn removal performance (87% ± 10%) when the influent water temperature decreased to 10 °C or less. Further analysis of previously published studies found the abundance of Betaproteobacteria was also significantly greater (p < 0.001) in biofilters with sustained Mn removal than in biofilters which did not treat for Mn as a contaminant, despite differences in design scale, source water, and media type. Microbiome network analysis identified multiple co-occurrence relationships between Betaproteobacteria and Mn oxidizing bacteria in the WTP B and WTP D biofilters, suggesting indirect contributions by Betaproteobacteria to biological Mn oxidation. These co-occurrence relationships were not present in the full-scale ACWD WTP microbiome. Whether the role of Betaproteobacteria in biological Mn oxidation is direct, indirect, or a combination of both, they are consistently present at a high abundance in both groundwater and surface water biofilters with sustained Mn removal, and their absence may contribute to the seasonal fluctuations in Mn removal observed at the ACWD WTP. This new insight to Betaproteobacteria and their role in Mn biofiltration could contribute to water innovation and design that would improve the reliability of Mn removal.

Thermal regime of the Danube Delta and the adjacent lakes

Abstract The Danube Delta is a unique natural object influenced by natural and human factors. According to the available observation and remote sensing data, the features of the water temperature in the Danube Delta, as well as in nearby lakes and the adjacent area of the Black Sea, have been determined. The water temperature in the Danube River was found to be much higher than the air temperature, especially in autumn. Generally, it is also higher than in nearby lakes and the adjacent part of the Black Sea. During 1961–2021 the mean annual water temperature in the Danube Delta increased significantly, especially during the last three decades. It has been determined that water temperature is affected not only by air temperature, but also by water discharge and wind. With a large water discharge the mixing of water is intensified and it causes the decrease of surface water temperature during the main part of the year with the exception of the coldest months. The greatest impact of water discharge on the water temperature is observed in June. The cool breeze in summer months also has some effect on the surface water temperature of the river near the seashore. The results show the potential of remote sensing to track the changes of water temperature along the river and to identify the shallow sections.

Linear water column stratification and euphotic depth determine the number of phytoplankton taxa that create biomass peaks in a hypertrophic oxbow lake

The mixing regime, the spatial distribution of nutrients and light determine the distribution of phytoplankton in lakes to a large extent. Linear stratification is a unique phenomenon among the various forms the lakes can stratify, representing a continuous and gradual water temperature decrease with depth. Here, we aimed to understand how mixing, nutrient and light affect the vertical distribution of phytoplankton in the case of linear water column stratification using the taxonomic and functional group approaches. We sampled phytoplankton and physical and chemical variables in the Malom-Tisza oxbow lake (Hungary) monthly from May to September between 2007 and 2009. Our results revealed that multiple biomass peaks of taxa belonging to distinct phytoplankton functional groups could develop in response to the strong linear stratification of the water column. Although several different species represented the functional groups, only one or two species developed the peaks. Light irradiance did not influence the vertical distribution of biomass and taxonomic richness of phytoplankton, but the depth of the euphotic zone determined the number of distinct biomass peaks. We found that diversity indices could not reflect the phytoplankton compositional differences well in the case of linear stratification, but similarity indices calculated among water column layers.

Influence of Temperature on the Removal Efficiency of Organic Matter and Ammonia from Micro-Polluted Source Water

Temperature is an important factor influencing the treatment effect of biological aerated filters (BAFs). In this study, BAFs incorporating biological manganese oxides (BMOs) were used to treat micro-polluted source water containing organic masses and ammonia, and the influence of temperature on the removal efficiency of the pollutants was investigated. The results showed that after the formation of biogenic manganese oxides (BMOs) in the filter layer, the removal efficiency of CODMn significantly improved. When the water temperature was approximately 24 °C, 16 °C, and 6~8 °C, the removal rates of CODMn, ammonia, and manganese were 60.64, 42.55, and 20.48; 98.40, 95.58, and 85.04; and 98.70, 97.63, and 96.38%, respectively. The influence of water temperature on the removal efficiency of the pollutants was hierarchically structured as follows: CODMn &gt; ammonia &gt; manganese. Analysis of the removal efficiencies of the pollutants along the filter layer showed that CODMn had been eliminated in every filtration layer, and ammonia and manganese were mainly removed in the 0~0.4 m and 0~0.8 m regions of the filter layer, respectively. With a decreasing water temperature, the concentrations of CODMn, ammonia, and manganese along the filter layer increased. The biological CODMn, manganese, and ammonia removal processes were all first-order kinetic reactions. With a decreasing water temperature, the kinetic constant k gradually decreased, and the reaction half-life (t1/2) gradually increased.

Experimental study of phase change material performance as thermal insulation of a double-walled spherical tank under partial vacuum for storing solar energy

In solar systems, conservation of stored energy is even more important than energy storage. In this study, as an innovative idea, the thermal behavior of a phase change material (PCM) is investigated as thermal insulation of an energy storage tank based on the unique feature of phase change at a constant temperature. Condition for creating an ideal insulation is the existence of a heat source at the border. The PCM surrounding the tank stores the solar energy latently in the process of thermal charging, and as a heat source in the process of thermal discharge. By releasing energy at a constant temperature through the PCM, the heat loss factor that is the temperature difference between the hot water and the surface of the tank is controlled. The PCM shows three different behaviors as the thermal insulation. One, as long as the energy stored in the PCM is sensibly released, the heat loss coefficient is almost constant, in which the PCM acts as a super insulator. Two, by releasing the latent energy, the heat loss coefficient tends to zero, and the PCM acts as an ideal insulator. Three, by releasing all the stored energy, the PCM acts as a normal insulator. Creating the relative vacuum between the tank and the glass cover improves the thermal performance, thereby the hot water temperature decreases by 7.4 °C in the best case, and the thermal efficiency reaches 85%.

Numerical Investigation of Cross-Flow Water Cooling Towers

Abstract In this study, thermal performance of the forced cross-flow water cooling tower is numerically investigated by using the commercial computational fluid dynamics software ansys-cfx. The temperature variation between inlet and outlet of the water, namely, process water temperature, is the main extracted result of simulations. Additionally, the cooling range (CR) that is the difference between inlet water temperature and outlet water temperature is the second representative result of the analysis. The effect of air velocity (Va), water droplet diameter (dw), and water temperature at the inlet of tower (Tw) are the variables that are considered to be the effective design parameters on the process temperature of the water. The process water temperature decreases, but the cooling range increases when the air velocity increases. When the inlet water temperature increases, the process water temperature and the cooling range also increase. On the other hand, the process water temperature decreases with the decreasing diameter of water droplets.

Experimental investigation of an autonomous liquid-cooled uninterruptible power supply (UPS)

This paper presents a new liquid-cooling technology for uninterruptible power supply (UPS) units in which an air-cooling system is combined with an indirect water-cooling system based on direct-chip cooling. This cooling architecture provides more opportunities to use free cooling as the main or only cooling system for optimal data centres (DCs). An experimental investigation was conducted using a 600 kW SOCOMEC UPS to identify the thermal behaviour of the system. Five thermal hydraulic tests were conducted under different thermal conditions, flow rates, and room temperatures. A 20 K temperature difference profile was validated with a safe operation of all UPS electronic equipment with a water flow rate of 13 l/min and inlet water and air room temperatures of 32 and 40 °C, respectively, resulting in a thermal efficiency of 82.27%. The experiments suggest that a DC-facility water-inlet temperature up to 41 °C is acceptable for UPS units. The effects of decreasing the water flow rate and increasing the water and air room temperatures were also analysed. A decrease in inlet water and air temperatures from 41 °C to 32 °C and from 47 °C to 40 °C, respectively, increased the thermal efficiency by 8.64%. A decrease in water flow rate from 20 l/min to 13 l/min reduced the thermal efficiency by 7.7%. Furthermore, an energy performance analysis comparison was performed between air- and water-cooled UPS units at both the UPS and infrastructure levels. A case study of a 600 kW UPS in a data centre in Roubaix, north of France, was investigated. The liquid-cooled UPS reduced the total annual energy consumption of the cooling system by at least 85% compared with an air-cooled UPS.