Differences In Water Temperature Research Articles

Application of energy-saving control strategy in air conditioning terminal equipment based on constant temperature difference of chilled water

Effectively reducing the energy consumption of central air conditioning systems is an important aspect of building energy efficiency. The energy consumption of terminal equipment accounts for over 25% of that of air conditioning systems. Although the heat and moisture exchange mechanism of the terminal unit has been extensively studied, studies on control strategies for terminal unit operation are lacking. This study proposes an energy-saving optimization control strategy for terminal units based on the constant temperature difference of chilled water in an engineering application study. A fan coil unit (FCU) controller was designed and manufactured, and a Local Area Network (LAN) control system was constructed and compared to determine the optimal control strategy. When adopting the energy-saving optimization control strategy for the terminal unit based on a constant chilled water temperature difference, the energy consumption of the terminal equipment was significantly decreased by 7.2%. The flow rate of chilled water was reduced by 26.94% when the indoor air temperature requirements were met, effectively reducing the energy consumption of the central air-conditioning system. The adjustment time required to reach a stable indoor temperature was reduced and environmental comfort was improved. These results demonstrate the potential of this control strategy for use in engineering practices to replace traditional control modes.

Control strategy for energy saving of refrigerating station systems in public buildings

In this work, a global energy saving optimal control strategy is proposed to address the high energy consumption of chilled water pumps caused by the small temperature difference between supply and return water, and the low efficiency of the chillers. The developed control strategy consists of two parts: the group control scheme and an optimal controller for variable water temperature/volume control. The group control scheme coordinates each chiller's operating time based on its running time and the chiller load rate. The optimal controller regulates the chilled water pump frequency according to the chilled water temperature difference and the valve opening at important terminal air conditioning units, and calculates the chilled water supply temperature under optimal comprehensive energy consumption of chillers and pumps. The proposed control strategy is easy to be embedded into the existing control systems of refrigerating stations. This scheme is then applied to the air conditioning system of a large public building in Beijing, China. Experimental results show that the proposed strategy can save up to 63% of energy consumption from the chilled water pumps and 6% from the chillers compared to the original control scheme.

Effects of rearing temperature on yolksac volume and growth rate in Lake Sturgeon, A. fulvescens, from hatch to age-1

In fishes, differences in egg incubation and water temperature in early rearing environments can have a significant impact on phenotypic development. This is particularly relevant during the first year of life when growth rate peaks and influences an individual's life history trajectory. In the present study, we examined the effect of differences in egg incubation, water temperature and overwintering on growth in Lake Sturgeon, A. fulvescens, throughout the first year of life. Developing embryos were incubated at 12–14 °C supplied with flow-through water and ambient light conditions in MacDonald hatching jars or allowed to adhere to substrate. Upon hatch (~9 days post-fertilization, dpf) larvae from each incubation treatment were then transferred to 16, 18 or 20 °C water increasing at a rate of 0.5 °C.day−1 and held at those temperatures until approximately 24 days post-hatch (dph). Experimental treatments were then transferred to a common garden set-up where duplicate treatment tanks were fed flow through river water at ambient temperature with natural light cycles. These were compared to fish transferred from a standard hatchery rearing treatment to the common garden tanks at the same time. Experimental fish were fed ad libitum twice daily throughout the growing season, but food was withheld when water temperature reached 1.5 °C (~6 months post-hatch, mph). Food was re-introduced at the start of spring the following year when water temperature exceeded 2 °C for three days in a row, (~ 10.5 mph). In experimental treatments, growth rate was highest in the 20 °C group during the first 3 months but converged with all other experimental treatments during winter before once again exceeding the other treatments following recovery from overwintering. Our data suggest that a temperature dependent growth phenotype was fixed during the first month of life in Lake Sturgeon that could have significant implications on hatchery rearing of this endangered species for conservation purposes.

Inundation, Hydrodynamics and Vegetation Influence Carbon Dioxide Concentrations in Amazon Floodplain Lakes

Extensive floodplains and numerous lakes in the Amazon basin are well suited to examine the role of floodable lands within the context of the sources and processing of carbon within inland waters. We measured diel, seasonal and inter-annual variations of CO2 concentrations and related environmental variables in open water and flooded vegetation and estimated their habitat area using remote sensing in a representative Amazon floodplain lake, Lake Janauacá. Variability in CO2 concentrations in open water resulted from changes in the extent of inundation and exchange with vegetated habitats. Depth-averaged values of CO2 in the open water of the lake, 157 ± 91 µM (mean ± SD), were less than those in an embayment near aquatic vegetation, 285 ± 116 µM, and were variable over 24-h periods at both sites. Within floating herbaceous plant mats, the mean concentration was 275 ± 77 µM, while in flooded forests it was 217 ± 78 µM. The best statistical model that included CO2 in aquatic plant mats, water clarity, rate of change in water level and chlorophyll-a concentrations explained around 90% of the variability in CO2 concentration. Three-dimensional hydrodynamic modeling demonstrated that diel differences in water temperature between plant mats and open water as well as basin-scale motions caused lateral exchanges of CO2 between vegetated habitats and open water. Our findings extend understanding of CO2 in tropical lakes and floodplains with measurements and models that emphasize the importance of flooded forests and aquatic herbaceous plants fringing floodplain lakes as sources of CO2 to open waters.

Seasonal/Interannual Variation and Controlling Factors for Oxygen and Carbon Isotopes of Ostracod Shells Collected From a Time-Series Sediment Trap in Lake Qinghai

Because the shell substance of an ostracod is derived entirely from the water body where it lives, its chemical compositions are sensitive to aquatic environment and thus have been used to reconstruct past climatic and environmental changes. However, there is controversy about the controlling factors for the different compositions of ostracod shells from various water bodies. In this study, seasonal and interannual variations in daily flux and stable oxygen-carbon isotopic compositions (δ18O, δ13C) for two species of ostracod shells (Limnocythere inopinata and Eucypris mareotica) and their controlling factors are discussed, based on ostracod shell samples collected from a time-series sediment trap from July 2010 through September 2012 and from surface sediments in Lake Qinghai, which were correlated with the state-of-the-art sensing data of the lake water. The results show that the daily flux of L. inopinata shells is an order of magnitude higher than that of E. mareotica. The δ18O and δ13C of both L. inopinata and E. mareotica shells have distinctly interannual and seasonal variations, with species differences. Interannual differences of δ18O for the two species of ostracod shells directly reflect the systematic differences of the summer water temperature between 2010 and 2012. We propose that seasonal variations of both δ18O and δ13C for the two species are affected by the precipitation of authigenic carbonates in microenvironment induced by high water temperature in summers, highlighting their environmental implications in Lake Qinghai.

How Can We Use Ocean Energy to Generate Electricity?

The oceans represent almost 70% of the surface of our planet, and they are in constant movement through waves, tides, and currents. These movements are formed differently: waves develop because of the action of the wind; tides because of the moon and the sun, and currents because of differences in water temperature and the rotation of the planet. Ocean movements bring food and oxygen to the plants and animals that live in the oceans and on the coasts. Waves and tides also help shape the coastline by erosion and accumulation of sand. Ocean movement is also important for humans: we have fun swimming in the waves, the tides help with fishing, and the currents are useful for moving ships across the ocean. This unending movement of the ocean can also be used to produce clean, renewable electric power.

Geographic variability in the gonadal development and sexual ontogeny of Hemigymnus, Cheilinus and Oxycheilinus wrasses among Indo-Pacific coral reefs.

Patterns of reproductive ontogeny in four species of coral reef wrasses (F: Labridae) Hemigymnus melapterus, Hemigymnus fasciatus, Cheilinus fasciatus and Oxycheilinus digramma were investigated. Populations of each species were sampled from two island groups of the central Great Barrier Reef (GBR), Australia, and from coral reefs in the central Philippines. These three sampling locations span 30° of latitude. The GBR and Philippine reefs experience biologically significant differences in water temperature, geography and human activity. The studied wrasses are effectively unfished in Australia but heavily fished in the Philippines. Gonad weights, histology and demographic data were obtained across the entire size and age range of H. melapterus, C. fasciatus and O. digramma from all locations. Analysis identified three processes of male recruitment: functional gonochorism and both forms of protogynous hermaphroditism, monandry and diandry. The expression of these distinct sexual ontogenies was locality dependent. Populations of H. melapterus, H. fasciatus, C. fasciatus and O. digramma on the GBR showed consistently uniform patterns of sexual ontogeny, with all species being exclusively monandric. H. melapterus, C. fasciatus and O. digramma in the Philippines displayed complex sexual ontogenies, with all species showing histological evidence of both diandry and functional gonochorism. Reproductive investment in gonadal tissue, and population sex structure, also differed between GBR and Philippine coral reefs. Philippine populations had substantially lower gonado-somatic indices than populations on the GBR. Nonetheless, Philippine populations matured more rapidly and displayed a protracted timing of sex change over a large size and age range. Thus, mature females appeared earlier and persisted later into ontogeny in the Philippines than on GBR reefs. Protracted timing of sex change on Philippine reefs is likely linked to the presence of primary males in the population, which is known to reduce the strength of selection for mature females to undergo sex change and become male. Hypotheses based on social structure of fish populations, environmental factors and evolutionary history were developed to account for the different patterns of sexual ontogeny in the focal wrasses.

Experimental and theoretical analysis of heat transfer in a solar collector storage

The current research includes a practical study of the thermal performance of solar collector integral storage system (ISCS) in which different types of heat exchangers are immersed in its enclosure for comparison. The first type is a straight tube heat exchanger (ST) and the other is a heat exchanger in the form of a coiled tube (CT). The effect of single and double glass layers and fluid flow rates inside the heat exchanger on the natural convection heat transfer of ISCS system is experimentally evaluated by determining the temperature difference of inlet and outlet water through the heat exchanger immersed into the ISCS enclosure, the temperature distribution inside the enclosure, the ISCS efficiency, and the amount of thermal storage during evening times. Three sets of experiments are performed for a different water flow rates (1.0, 1.5, 2.0, and 2.5 Lpm) inside the heat exchanger that is immersed in the thermally insulated enclosure and different glassing layers. The first set represents the presence of a heat exchanger in the form of a straight tube with a single glass was layer on the top face of the enclosure that is called (STSG). The second set uses a coiled tube heat exchanger with a single glass on the upper side of the enclosure and it’s named as (CTSG). The last set of experiments is represented by a heat exchanger in the form of a coiled tube with a double glass on the upper face of the enclosure and it’s abbreviated as (CTDG). At water flow rate of 1 Lpm, the CTDG exhibited higher temperature difference (28 °C and 19.9 °C than (19.4 and 11.4 °C) for CTSG and (12 and 7.3°C) for STSG during day and night times, respectively. The results reveal that the thermal efficiency (84.5 - 77.8 %) of the (CTDG) case at water flow rate of 2.5 Lpm was higher than the efficiency (68.8 - 56.6%) of (CTSG) case and that (41.7 - 39.7%) of STSG) case during day and night times, respectively. It was also observed that the internal energy exceeds the amount of solar radiation during the day and provides a thermal storage at night due to the complete isolation of the collector. The temperature measurements near the tube allow the calculation of the Rayleigh number during the heat transfer process, and empirical relationships haves been deduced for each set of experiments between the Nusselt number and the Rayleigh number.

Morphological Study of Fabricated PVDF Based Hydrophobic Membrane for Different Additives and Coagulation Bath Temperature

The demand of membrane distillation (MD) has increased since last few decades for numerous applications. The membrane used in MD is hydrophobic; therefore, the focus has been emphasised on the development of a suitable membrane with desired microstructure. In this study, the flat sheet hydrophobic membrane of suitable properties has been casted with various additives such as water, ethane-di-ol, and propan-2-ol in dope solution using a non-solvent induced phase separation (NIPS) technique. The effect of water content in dope solution has been studied on casted membrane porosity and contact angle. The maximum contact angle and porosity were found to be 96° and 53.23% at 4 weight percent of water content in dope solution of PVDF polymer and di.methyl.acetamide as solvent. It was found that SEM micrograph when ethane-di-ol and propan-2-ol are used as an additive shows more finger-like pores and nodules, respectively, in the microstructure of the casted membrane. Furthermore, synergistic effects using water with other additives were also identified using SEM micrograph of casted membrane and it was observed that water with ethane-di-ol and propan-2-ol form contact angle of 98° and 105°, respectively, for 2 weight percent each additive in dope. In this study, the membrane was also cast by dissolving PVDF powder in di.methyl.acetamide solvent with lithium chloride and the effect of the temperature difference between coagulation bath and film temperature was investigated using an SEM micrograph. Overall, it was found that water content and temperature difference aid in developing hydrophobic porous membrane of desired properties for MD applications.

Culture Trials of Catfish (Clarias Gariepinus) Fingerlings and Juveniles Using Floating Plastic Enclosure System

There is paucity of information on the suitable floating catfish fingerling/nursery production system for juvenile catfish which are in very high demand. The effects of enclosure shape, stocking density, water quality on production of catfish fingerlings and juveniles were evaluated by carrying out two experiments. Experiments involved the use of two plastic enclosure shapes (circular and rectangular of 60litres each) and dosage of eggs (5g, 10g, and 15g of eggs). There were 3 replicates per treatment (enclosure shape and dosage). Eggs were incubated and hatched in the enclosures. Data collected were number of fingerlings, weight and length, pH and water temperature inside and outside the enclosures were also monitored. Parameters monitored included number of juveniles, percentage of shooters and suspected cannibalized fish. Data were subjected to ANOVA. Results showed that mean water pH inside the enclosures were not significantly different (p>0.05) with respect to enclosure shape. Weight and length of fish at fingerling stage were affected significantly (p<0.001) by dosage. 5g dosage recorded highest mean weight (3.6g) and the length (6.7cm) of fish at fingerling stage while the 15g dosage had the least mean weight (2.0g) and length (5.0cm). There were no significant differences (p>0.05) in water temperature and pH within and outside the enclosure under different egg dosages, percentage of shooters and suspected cannibalized fish were not significantly different (p> 0.05) between enclosure shapes. However, the mean weight of fish in circular enclosure was significantly higher (p<0.001) than in rectangular enclosure. Fish in circular enclosures weighed 7.7g each while those in rectangular enclosures weighed 7.0g. Percentage survival and number of shooters were not significantly different (p>0.05) among the three stocking densities. In contrast, number of fish harvested and suspected cannibalized fish were affected significantly (p<0.001) by stocking densities. Length of fish harvested was significantly different (p<0.001) among the stocking densities. The higher the stocking density the shorter the length of fish harvested. The same inverse trend was observed in weight of shooters, stocking density at 60 fish/enclosure yielded the lightest shooters (6.4g) compared with the highest (8.3g) in 15 fish/enclosure. There was no significant difference (p>0.05) in number of shooters under the different stocking densities, however it is concluded that lower stocking density is preferred to higher stocking density. It is therefore recommended that enclosure of either shape could be adopted. DOI: 10.7176/JBAH/11-14-04 Publication date: July 31 st 2021

Temperature and multiple parasites combine to alter host community structure

Predicting the effects of climate change requires understanding complex interactions among multiple abiotic and biotic factors. By influencing key interactions among host species, parasites can affect community and ecosystem structuring. Yet, our understanding of how multiple parasites and abiotic factors interact to alter ecosystem structure remains limited. To empirically test the role of temperature variation and parasites in shaping communities, we used a multigenerational mesocosm experiment composed of four sympatric freshwater crustacean species (isopods and amphipods) that share up to four parasite species. Mesocosms were assigned to one of four different treatments with contrasting seasonal temperatures (normal and elevated) and parasite exposure levels (continuous and arrested (presence or absence of parasite larvae in mesocosm)). We found that parasite exposure and water temperature had interactive effects on the host community. Continuous exposure to parasites altered the community structure and differences in water temperature altered species abundance. The abundance of the amphipod Paracalliope fluviatilis decreased substantially when experiencing continuous parasite exposure and elevated water temperatures. Elevated temperatures also led to parasite‐induced mortality in another amphipod host, Paracorophium excavatum. Contrastingly, isopod hosts were affected much less, suggesting increasing temperatures in conjunction with higher parasite exposure might increase their relative abundance in the community. Changes in invertebrate host populations have implications for other species such as fish and birds that consume crustaceans as well as having impacts on ecosystem processes, such as aquatic primary production and nutrient cycling. In light of climate change predictions, parasite exposure and rise in average temperatures may have substantial impacts on communities and ecosystems, altering ecosystem structure and dynamics.

Seed vigor testing of coffee [Coffea sp.] to gibberellin hormone [GA3] concentration and water temperature differences

West Sumatra is one producing coffee region in Indonesia that contributes to the economy in Indonesia because unstable need expand. Optimizing generative propagation of coffee plants with gibberellin hormone treatment and different water temperatures on coffee seed germination stage. The research was conducted at the Seed Technology Laboratory Faculty Agriculture, Andalas University from July to September 2020. Research methods used randomized block design [RBD] with 2 treatments namely concentration hormone gibberellin and immersion water temperature differences. Measurement parameters are maximum growth potential [%], First Count Test [FCT] [%], and Index Value Test [IVT] [days]. All parameter observation results showed a significant effect on the treatment of gibberellin hormone concentration and water temperature treatment. G4S1 sample [the combination of 200 ppm gibberellin hormone concentration and room water temperature treatments] has resulted as the best treatment for all parameters. Respectively, 0.79 days for index value test, 76.67% for the first count test, and 85% for the maximum growth potential parameters.

Abundance and distribution of zooplankton communities inhabiting the intertidal zone of the Suez Gulf, Red Sea, Egypt

Zooplankton communities at the Gulf of Suez were investigated during the current study and their abundance was correlated with the physicochemical parameters of the area. The goal of the study was to estimate the distribution and abundance of zooplankton taxa under various habitat stressors and update the ecological database of the study area. The study recorded 39 species of zooplankton in 16 taxa with a total abundance of 66300 organisms across all investigated sites. The organisms were distributed between holoplankton that recorded approximately 55560 organisms (84.2 %) and meroplankton which recorded approximately 10740 organisms (15.8 %). The most abundant groups were Copepoda 52340 organisms (78.9 %), larval stages (11%) and Maxillopoda (3 %). While, Anthomedusea, Leptomeduea, and Pteropods were rarely recorded. Among the surveyed sites, Zafarana recorded the highest abundance (23537 Organisms) with a percentage of 63 of the total zooplankton populations, whereas the lowest site in abundance was Port-Tewfik which recorded (6656 organisms), represented a percentage of 10 % of the total populations. The current work showed that copepods recorded a significant difference in spatial distribution, while copepods, dissolved oxygen, water temperature, and total dissolved solids differed significantly at temporal distribution.

Energy/exergy analysis of solar driven mechanical vapor compression desalination system with nano-filtration pretreatment

The performance of the mechanical vapor compression desalination system is limited due to the required vacuum pressure and associated high temperature scaling problem. Thus, a new solar driven mechanical vapor compression desalination plant with nano-filtration pretreatment operating at atmospheric pressure is developed for a production of 500 m3/day. The electrical and thermal energies of the new system are generated using the integration of solar photovoltaic modules and parabolic trough collectors. To evaluate the performance of the new system, energy/exergy analysis is performed by employing a MATLAB package and a Graphical User Interface (GUI) tool. Also, an economic evaluation for the plant's direct, indirect, and unit product costs ($/m3) is presented. The predicted results are validated with the available measurements. The effects of different design parameters such as feed water temperature, distilled and brine water temperature difference, salt rejection and recovery ratio on plant performance are investigated. The proposed plant's exergy efficiency is found to vary from 14.59 to 20% consistently with design parameters. The enhancement in exergy efficiency is estimated to be 153.7%, 56.3%, 32.63% and 27% compared with Multi-Effect evaporation mechanical and conventional vapor compression, forward feed multi-effect mechanical vapor compression and reverse osmosis systems, respectively. The salt rejection and recovery ratio are found to be the most significant parameters to enhance the plant exergy efficiency. Furthermore, the photovoltaic unit has a significant effect on exergy destruction of the plant with a percentage of 85.79%. The parabolic trough collectors also have high exergy destruction of about 69.53%. The economic analysis reveals that the unit water price for the proposed plant is equal to 1.54 $/m3. Therefore, the developed solar-NF-MVC system suits small scale units for remote communities.

Novel concept on the enhancement of conventional solar still performance via constant heat rate supply to the saline water.

One of most reduction reasons of simple conventional solar still productivity is the coupling between high solar intensity and the high ambient temperature in the same time. The high intensity increases the saline water temperature, while the outside temperature increases the glass temperature, and consequently reduction in saline water and glass temperature difference leads to reduction in condensation and productivity. The present theoretical study focuses on the completion of the absorbed solar energy in the basin to be constant during the day. The basin water will be in high temperature level all day especially at the time of low outside temperature far away the noon. The absorbed heat in the basin is held constant at αw Imax by extra heat from wind turbine power with battery storage system all day hours. The results show that the solar still productivity with constant heat supply is more than that with same amount of variable energy during sun rise time only (6 AM to 6 PM) by 69.133%. So, constant absorbed heat in the water basin (αw Imax) through the 24 h of the day enhances the performance with productivity up to 248% with the hybrid solar and electric power consumption of the wind turbine power. The water in the basin is held constant at 2 cm via makeup water to compensate the evaporation rate.

Assessment of the efficacy of prophylactic health products on water quality and shrimp ( Penaeus monodon ) performance at the nursery phase

The aim was to assess the efficacy of prophylactic health products (PHPs) on shrimp (Penaeus monodon) post larvae (PL) during the nursery phase. This included five treatments: infeed probiotic (F_PRO), water probiotic (W_PRO), a combination of water and infeed probiotic (FW_SYN), biofloc, a combination of biofloc and infeed probiotic (F_PRO&biofloc), and a no-treatment control, five replicates each. Each tank was filled with 450 L water and stocked with 700 PL15, weight 0.008 ± 0.00 g at a density of 1.56 PL/L, reared for 27 days. There were no significant differences in water temperature, dissolved oxygen, alkalinity, and total ammonia nitrogen among treatments and control. pH and nitrite were lower in biofloc and F_PRO&biofloc compared to other treatments. The final body weight, weight gain, specific growth rate and food conversion ratio were significantly higher (p ≤ .05) in F_PRO&biofloc compared to other treatments and control. A salinity stress test showed a significantly higher survival rate in F_PRO&biofloc followed by biofloc than other treatments and control. Our study indicated that rearing shrimp in biofloc alone or combined with infeed probiotic might increase growth and resistance to environmental stressors. Further on-farm trials are required to confirm the efficacy of the PHPs.

Burrowing behaviour of unionid mussels in subtropical rivers: Implications for survey guidelines

Abstract Conservation efforts have increased in response to global mussel declines, and effective surveys are a crucial step in assessing and monitoring mussel populations and in determining their conservation status. The burrowing behaviour of mussels can affect their detectability, and a better understanding of these behaviours would help to improve survey design and guidelines. The burrowing depth of mussels may differ between seasons, habitat conditions, species, and individuals, and little is known about the burrowing behaviour of mussels in subtropical rivers. Burrowing depth variation was examined and compared at three sites in the San Marcos, Guadalupe, and San Antonio river drainages in central Texas. In addition, laboratory experiments were used to determine whether observed differences between field sites and seasons could be linked to differences in substrate type and water temperature and to examine differences between species. Seasonal variation in burrowing depth was found at all field sites, and water temperature was a significant factor for explaining variation in burrowing depth, but there was no clear relationship between burrowing depth and temperature in shorter term laboratory experiments, where individual variation was high and burrowing behaviour seemed to be solely a function of time. Mussels burrowed significantly deeper in finer substrate (sand vs. gravel) in both field and laboratory experiments. Few significant differences between species were found in the field, but no differences were found in the laboratory experiments. The results suggest that surveys may need to follow different guidelines depending on local conditions, such as substrate and water temperature. Surveys will be less efficient and may fail to detect larger proportions of populations in colder water temperatures. In addition, a larger proportion of burrowed mussels can be expected at sites with finer substrate, such as sand. Under these conditions, visual searches will not suffice, as a large part of the population or specific species may be overlooked.

Mass 47 clumped isotope signatures in modern lacustrine authigenic carbonates in Western China and other regions and implications for paleotemperature and paleoelevation reconstructions

With the development of the carbonate clumped isotope (Δ47) geothermometer, many Δ47–temperature calibrations based on biogenic and abiogenic carbonates have been generated in recent years. However, there is still not a robust empirical calibration relationship derived from lacustrine authigenic carbonates that can be used to calculate lake water temperatures from Δ47 values. In this study, we present a new calibration dataset that is comprised of measurements of the clumped isotope composition of 33 lacustrine authigenic carbonates collected from terminal lakes primarily in Western China that cover a substantial altitudinal gradient, and 5 samples from other regions. These data allow us to directly derive a temperature calibration for lacustrine authigenic carbonates. Our results show a robust correlation between modern lacustrine authigenic carbonate clumped isotope composition (Δ47carb) values and independently measured mean summer water surface temperatures (Twater) (ranging from 9.8 to 26.0°C), which confirms the utility of mass-47 clumped isotope measurements of lacustrine authigenic carbonates as a lake water temperature indicator and allows for the derivation of the following calibration equation: Δ47carb (‰) = 0.0521 ± 0.0071 × 106/Twater2 (K) + 0.0904 ± 0.0870 (R2 = 0.6224, P < 0.0001, n = 33). We observe that Δ47carb is significantly correlated to lake elevation at 35°N from 270 to 5,156 m a.s.l. The change in Δ47–derived water temperature differences through elevation gradients (i.e. lapse rate) is around 3.2°C/km. We do not observe a significant correlation between Δ47carb and carbonate oxygen isotopic composition or independently measured lake surface water oxygen isotopic composition. Additionally, in our dataset, we find that water chemistry, carbonate precipitation rate, carbonate content and mineral-specific differences do not significantly affect Δ47carb values. Hence, the mass-47 clumped isotope signal of lacustrine authigenic carbonate can be used in paleotemperature and paleoaltimetry studies if post-depositional diagenesis did not modify the isotopic composition.

Optimal setting parameters of cooling system under different climate zones for data center energy efficiency

The high rates of electricity consumption in data centers become a worldwide concern. Water-side free cooling is an effective solution to reduce the energy consumed by the data center's cooling system. However, the water-side free cooling system is not well planned, and the free cooling utilization rate is low in different climate zone. Moreover, the effects of local climatic conditions on the optimal setting parameters have not been researched. In this study, the optimal setting in chilled water supply temperature, temperature difference, and chilled water return temperature is analyzed to enhance the efficiency of the free cooling system. We observed that the optimal setting could reduce annual energy consumption by 23.5%–60.8% in various climate zones and has substantial energy-saving potential in the subtropical highland climate zone. The results show that the optimal setting parameters are highly affected by the annual accumulative wet-bulb temperature distribution. Furthermore, considering a monthly analysis of these enhanced parameters, we proposed a dual-working condition cooling system for the data center's future construction. This research work guides the design of such cooling systems in various climate zones.

Reduction in on-off operations of an air source heat pump with active thermal storage and demand response: An experimental case study

The air source heat pump (ASHP) in an air-conditioning system encounters frequent start-stop operations due to the fluctuation of cooling and heating load in buildings. A energy-storage tank is widely used as an effective device to solve this problem, and its flexible use can help to improve the operating efficiency of air-conditioning systems. Through building an air-conditioning system that can flexibly control the energy storage tank in a VAV experimental platform, this paper studies the operation mechanism of the storage tank as a buffer device (i.e., an active energy storage device) participating in the demand response in winter and summer. When using the storage tank, the time taken by return water temperature to exceed the set temperature range of the ASHP in the operating state is prolonged and the frequency of the start-stop operations of the ASHP is reduced. In the operation case of “large flow rate, small load”, the differences of water temperature between the inlet and outlet of the energy storage tank can compensate for the deficiency of small water temperature difference of air heading unit. As an active energy storage device, the energy storage water tank can provide a stable shedding peak load of the power grid when participating in demand response (DR). On non-DR days, ASHP is turned off before the air-conditioning is off, and the energy-storage tank provides the required energy for the terminal room, which can realize efficient energy utilization in the tank. The experimental results presented in this study can provide a reference for the flexible use of small-scale water storage systems.