Cooling Water Stream Research Articles

Numerical Study on V Shaped Natural Draft Cooling Tower Supporting System

Cooling towers generally used to extract waste heat to the atmosphere from cooling water stream to a lower temperature and hence it rejects heat from water. The size of the cooling tower is large, with thin wall and complex geometry. Wind load plays a dominant role in the design of cooling tower. These cooling towers are subjected to self-weight and dynamic loads such as wind and earthquake. This paper presents the study of cooling tower of height 200m above the ground level. The Analysis of a cooling tower is done for a wind load using a finite element analysis considering V frame shell base supporting system. The analysis is performed in Commercial software STAAD PRO and the results obtained are presented in this paper.

Cryptic Species of Freshwater Sculpin (Cottidae: Cottus) in California, USA.

The Riffle Sculpin (Cottus gulosus) is a small, bottom-dwelling fish regarded as widespread in the cool-water streams that flow into Californias Central Valley and into streams of the central California coast. Using population genomics, supported by other genetic, distributional, and meristic studies, we demonstrate that C. gulosus consists of three cryptic species with four subspecies (five lineages), all but one entirely endemic to California: Cottus pitensis, Pit Sculpin Bailey and Bond 1963 Cottus gulosus, Inland Riffle Sculpin (Girard 1854) g. gulosus: San Joaquin Riffle Sculpin (Girard 1854), nominate subspecies g. wintu: Sacramento Riffle Sculpin, Moyle and Campbell 2022, new subspecies Cottus ohlone, Coastal Riffle Sculpin Moyle and Campbell 2022, new species o. ohlone, Ohlone Riffle Sculpin Moyle and Campbell 2022, nominate subspecies o. pomo, Pomo Riffle Sculpin Moyle and Campbell 2022, new subspecies. The three species are endemic to California watersheds although the range of C. pitensis extends into southeastern Oregon. All are confined to cool headwater streams or to rivers with cold water releases below dams. Their populations are increasingly isolated from one another because of anthropogenic changes to Californias river systems and some are threatened with extinction. Providing taxonomic recognition of the distinct forms will improve conservation efforts on their behalf. This study also demonstrates how genomics can be used to resolve situations where signals from mitochondrial and nuclear DNA are in conflict.

A novel lung-inspired 3D-printed desiccant-coated heat exchanger for high-performance humidity management in buildings

Offering an independent humidity management method for buildings, desiccant-coated heat exchangers (DCHXs) are deemed a promising approach to improve the overall energy efficiency of air conditioning (AC) systems. State-of-the-art DCHXs, however, are bound with conventional HX topologies either providing limited desiccant-air interfacial areas or introducing excessive pressure drop penalties. Here, a novel 3D-printed DCHX concept inspired by the bronchi arrangement of a human lung is introduced to address the shortcomings inherent in existing DCHX designs. The proposed lung-inspired DCHX utilizes two intertwined bicontinuous flow networks enabling highly efficient heat and mass transfer characteristics for augmented adsorption and regeneration processes at low pressure drop penalties. While the first network evenly distributes an incoming air stream through the entire volume of the lung-inspired DCHX, the second network volumetrically splits a cooling water stream within and through the first network. Effects of various parameters including air flow rate, outdoor air humidity ratio, and regeneration temperature on dehumidification performance and energy efficiency of the proposed lung-inspired DCHX were investigated. Experimental results indicated the proposed lung-inspired 3D-printed DCHX outperforms existing DCHX systems by demonstrating an excellent balance between a high volumetric adsorption rate and a low pressure drop penalty. The volumetric adsorption rate of the proposed lung-inspired DCHX technology is 54.8 g/m3-s, a more than two-fold improvement compared with state-of-the-art DCHX systems. Additionally, the lung-inspired DCHX offers high thermal energy efficiency of 56% at a low regeneration temperature of 40 °C. Therefore, the proposed lung-inspired 3D-printed DCHX offers a new solid-desiccant-based air dehumidification pathway for next-generation high-performance AC systems.

Integrated Vapor Compression Chiller with Bottoming Organic Rankine Cycle and Onsite Low-Grade Renewable Energy

The present study offers a scheme to improve the performance of existing large-scale chillers. The system involves raising the temperature of the chiller’s cooling water stream using renewable energy sources by incorporating an organic Rankine cycle (ORC). The thermal analysis was conducted by raising the temperature of one-third of the approximately 200 ton chiller’s cooling water. The investigation was considered for ORC evaporator inlet temperature of 90~120 °C by the step of 10 °C. Various working fluids for the different ORC evaporator inlet temperatures were examined. Sensitivity analyses conducted on the degree of superheating, degree of subcooling, condenser saturation temperature, pinch point temperature differences of the ORC evaporator and condenser, and the mass flowrates of the heating and cooling streams were also reported. Genetic algorithm was employed to carry out the optimization. The best options for the ORC working fluid at the heating source ORC evaporator inlet temperatures of 90 °C was found to be DME, presenting an improvement of 48.72% in comparison with the rated coefficient of performance (COP) value of the VCC, with a renewable energy input requirement of 710 kW. At the heat source temperatures of 100 °C and 110 °C, butene, which presented an improvement in the COP equal to 48.76% and 68.85%, respectively, with the corresponding renewable energy requirements of 789.6 kW and 852 kW, was found to be the ideal candidate. Meanwhile, at the heat source inlet temperature of 120 °C, R1233zd (E), representing an improvement of 140.88% with the renewable energy input of around 1061 kW, was determined to be the most favorable ORC working fluid candidate.

Impact of Weather Conditions on the Operation of Power Unit Cooling Towers 905 MWe

The paper presents the results of measurements and calculations concerning the influence of weather conditions on the operation of wet cooling towers of 905 MWe units of the Opole Power Plant (Poland). The research concerned the influence of temperature and relative humidity of air, wind and power unit load on the water temperature at the outlet from the cooling tower, the level of water cooling, cooling efficiency and cooling water losses. In the cooling water loss, the evaporation loss stream and the drift loss stream were distinguished. In the analyzed operating conditions of the power unit, for example, an increase in Tamb air by 5 °C (from 20–22 °C to 25–27 °C) causes an increase in temperature at the outlet of the cooling tower by 3–4 °C. The influence of air temperature and humidity on the level of water cooling ΔTw and cooling efficiency ε were also found. In the case of ΔTw, the effect is in the order of 0.1–0.2 °C and results from the change in cooling water temperature and the heat exchange in the condenser. The ε value is influenced by air temperature and humidity, which determine the wet bulb temperature value. Within the range of power changes of the unit from 400 to 900 MWe, the evaporated water stream m˙ev, depending on the environmental conditions, increases from 400–600 tons/h to the value of 1000–1400 tons/h. It was determined that in the case of the average power of the unit at the level of 576.6 MWe, the average values of the evaporation and drift streams were respectively 0.78% and 0.15% of the cooling water stream. Using statistical methods, it was found that the influence of wind on the level of water cooling, cooling efficiency and cooling water losses was statistically significant.

Innovative process solutions in the field of water decarbonisation as an element of integrated management in environmental protection – A case study

Abstract Most waters in Poland are classified as medium or very hard. In case of industrial waters, their chemical composition and physical parameters play an essential role. The water ought to be soft and should not contain dissolved salts and gases. This water, which has not undergone a softening process, may cause damage to heating devices and boiler scale within a few years. Therefore, water softening is mainly used for heating and energy purposes. However, an important issue is technological processes in which water is used both as a product additive or as an agent in exchange of heat and mass [Reference Document…2001; Nawrocki, Biłozor 2000; Kiedryńska, Papciak, Granops 2006; Biłozor 2012]. The aim of the work was to determine the effect of changes in the proportion of decarbonised water in the process water stream on its parameters (oxidability, general hardness) and parameters of cooling water in water cycles. The possibility of limiting the consumption of raw water to the processes carried out on the premises of the plant and the possibilities of improving energy efficiency in the area of water and wastewater management with a variable stream of decarbonised water in the technological water was checked. It was found that the increase in the share of decarbonised water in the technological and cooling water stream is important in the implementation of process solutions in this area and has a positive effect on reducing costs related to the operational functioning of the water and wastewater management area.

High-Flux Direct-Contact Pervaporation Membranes for Desalination.

To solve the pore-wetting problems of membrane distillation, we developed a series of three-layer composite pervaporation (PV) membranes that could be applied in direct contact mode. Specifically, a porous poly(vinylidene fluoride) (PVDF) layer was placed on top of a polytetrafluoroethylene (PTFE) microfiltration membrane using the nonsolvent-induced phase inversion method, and then a poly(vinyl alcohol) (PVA) dense layer was coated on the PVDF/PTFE substrate. The hydrophobic PTFE layer prevented the permeate side of the PVA/PVDF/PTFE membrane from being wetted with cooling water. The PVDF intermediate layer acted as a glue to the PVA and PTFE layers. Also, the PVA dense layer provided a high water flux, salt rejection, and antifouling property. As a result, a high water flux of 44.5 ± 3.0 kg/(m2 h) with the NaCl rejection of >99.99% were achieved for the direct-contact pervaporation (DCPV) membranes when separating a 3.5 wt % NaCl solution at 75.0 ± 0.9 °C using a cooling water stream of 20.6 ± 0.3 °C. Moreover, when the NaCl solution contained 10 mg/L Tween20 (acting as a contaminant), a stable water flux of 45.8 ± 0.6 kg/(m2 h) was maintained for at least 24 h, indicating excellent antifouling property. Furthermore, when the permeate side was under vacuum, the water flux increased to 83.4 ± 6.5 kg/(m2 h), similar to the highest reported data of all the existing PV desalination membranes. More importantly, the easy-to-scale-up fabrication method indicated great potential of DCPV membranes for commercialization.

Characterization of aqueous streams in a petrochemical industry: A study for the reuse of industrial effluents

The scarcity of water is an increasingly alarming issue all over the world, and each sector of society must take action to reduce water use in its activities. In chemical and petrochemical industries, water is a fundamental resource for the production process. This industrial sector has a demand for great quantities of water with specified qualities for each process. As the water runs through the industrial processes, it incorporates several substances and its characteristics modify. It becomes an effluent that must be treated so as to accommodate the emission standards established in the regulations. In most cases, the standards for disposal are less restrictive than the quality standards for industrial reuse of this effluent. If it is not considered for reuse, all related activities will be compromised. This work presents a case study of a Brazilian petrochemical industry where various aqueous streams were characterized to evaluate the quality requirements necessary for water reuse in the production process. The work examines water use and the quality of each aqueous stream, characterizing them with respect to alkalinity, chlorides, electrical conductivity, chemical oxygen demand, total hardness, iron, pH, silica, total solids, sulfates, and turbidity. The study demonstrates that the cooling water stream has elevated concentrations for these parameters and thus demands less quality for water reuse. In general, demineralized water presents the lowest concentrations for the parameters under evaluation and therefore requires greater quality for water reuse.

Fish assemblage production estimates in Appalachian streams across a latitudinal and temperature gradient

AbstractProduction of biomass is central to the ecology and sustainability of fish assemblages. The goal of this study was to empirically estimate and compare fish assemblage production, production‐to‐biomass (P/B) ratios and species composition for 25 second‐ to third‐order streams spanning the Appalachian Mountains (from Vermont to North Carolina) that vary in their temperature regimes. Fish assemblage production estimates ranged from 0.15 to 6.79 g m−2 year−1, and P/B ratios ranged from 0.20 to 1.07. There were no significant differences in mean assemblage production across northern cold‐water, southern cold‐water and southern cool‐water streams (p = .35). Two warm‐water streams, not included in these comparisons, had the highest mean production and biomass values. Mean assemblage P/B was significantly higher in northern cold‐water streams relative to southern cold‐water and cool‐water streams (p = .01). Species evenness in production declined with stream temperature and differed significantly across the lower latitude cold‐water, cool‐water and warm‐water streams and the higher latitude (i.e. more northern) cold‐water streams. Our fish assemblage production estimates and P/B ratios were both lower and higher compared to previously published estimates for similar stream habitats. This study provides empirical fish assemblage production estimates to inform future research on southern Appalachian streams and on the potential impacts of varying temperature regimes on cold‐water, cool‐water and warm‐water fish production in the coming decades as climate change continues to threaten fish assemblages.

Water temperature dynamics and heat transport in a typical Japanese river

The water temperature regime of the Oita River on Kyushu Island (33°N latitude) in southern Japan is illustrated and analyzed, and related to the river’s hydrology. The river is short (55 km) and steep (ave. slope = 0.088), and has a flashy flow regime. Precipitation is high (1653 mm year−1) and divided between a wet monsoon season, typhoons, and a dry season in winter. A base flow analysis showed that groundwater contributes about 50 % of the annual flow to the Oita River and controls the river’s heat budget. At a measured mean annual temperature of ~16 °C, groundwater (base flow) input causes unexpected cool (≤24 °C) river temperatures in summer and warm (≥8 °C) river temperatures in winter. The Oita River is typical of many Japanese rivers. Its hydraulic residence time is very short (0.5–1.5 days) and limits the heat exchange with the atmosphere so that a significant deficit remains between observed river water temperatures and equilibrium temperatures in mid-summer and mid-winter. Correlations of recorded stream temperatures with atmospheric temperatures (air, dew point and equilibrium temperatures) were strong. Weekly air and stream temperature data (averaged from 10-min measurements) were fitted by linear regressions with R 2 = 0.98 and RMSE = 0.83 °C. Daily data were only slightly less well correlated with R 2 = 0.96 and RMSE = 1.17 °C. The relationships were highly linear. The slope of the stream temperature vs. air temperature correlation was in the range from 0.63 (weekly) to 0.58 (daily) indicating that stream temperatures are dominated by groundwater input. Air and stream temperatures have a strong correlation in both wet (monsoon) and dry seasons, and geothermal heat input has no basin-wide effect; the 50 % groundwater (base flow) input raises the annual mean and reduces seasonal temperature amplitude in the Oita River and provides a cool-water stream. Water temperatures were gathered from a long-term monitoring database and by recent (2012–2013) high-resolution in-stream monitoring. Key drivers of stream temperature were identified. Linear regressions were used to relate air temperature, dew point temperature, and equilibrium temperature with stream temperature. Groundwater was identified as a key input of water consistently around 16 °C, moderating temperatures in the summer and winter due to very short water residence times in the steep and short river. This paper contributes to the body of knowledge about global stream temperatures, and clarifies specific questions for Japanese rivers.

Potential spread of Great Lakes fishes given climate change and proposed dams: an approach using circuit theory to evaluate invasion risk

The Great Lakes currently harbour a number of non-native fishes that are thermally limited to the comparatively warm waters of Lake Erie and Lake Ontario. Climate change could facilitate the inland spread of many non-native species as the Great Lakes and their tributaries warm, putting thousands of inland lakes and streams at risk. We investigated how watershed network configurations, climate change and proposed hydro-power development could influence invasion risk in the Great Lakes Basin. Electric circuit theory was used to model hydrologic accessibility of aquatic ecological networks (i.e., lake, river, and impoundment chains) within tertiary watersheds. Risk of invasion was measured as the product of probability of non-native species spread (hydrologic accessibility) and amount of suitable thermal habitat under an ensemble of air temperature projections. Proposed hydro-power dam sites and their upstream catchments were used to evaluate changes in total risk of invasion given passable, semi-passable, and impassable dams. We show that projected climate change will lead to more coolwater stream and warmwater lake habitat. Overall invasion risk of cool- and warmwater species was highest in southern Ontario and surprisingly in northern watersheds draining into Lake Superior. This risk could be partially mediated by proposed dams if dams reduce connectivity and access to potentially suitable habitat. Our evaluation of mean invasion risk provides a broad-scale comparative tool for management of invasive species control options.

Synthesis of cooling water systems with multiple cooling towers

This paper presents a systematic approach for the synthesis of re-circulating cooling water systems consisting of a cooler network and a cooling tower network (i.e. a general arrangement of multiple interconnected cooling towers with different supply temperatures). An overall superstructure is developed, which contains all the different alternatives for the cooler and cooling tower networks, as well as all their potential interconnections for fixed data of hot process streams. The synthesis problem is formulated as a mixed integer nonlinear programming problem. The continuous variables include the flow rates and temperatures of the circulating cooling water in the superstructure while the integer variables describe the existence of the coolers and the cooling towers. The objective function is to minimize the total annual cost, which includes the investment costs of cooler units and cooling towers, as well as the operating costs due to make-up water and power consumption of the circulating-water pumps and cooling tower fans. The solution of the proposed MINLP formulation provides simultaneously both the optimal configuration and operating conditions of the cooler and cooling tower network to comply with given process cooling demand at minimum total annual cost. One of the most important design variables is the number of cooling water sources (i.e. cooling water streams at different temperatures originated from the outlets of cooling towers) for removing heat from several hot process streams at different temperature ranges. Results show that cooling systems consisting of multiple cooling towers with different supply temperature yield significant better results than traditional systems with a cooler network in parallel arrangement that is supplied with cooling water from a single cooling tower.

Development and validation of two fish-based indices of biotic integrity for assessing perennial coolwater streams in Wisconsin, USA

Perennial coolwater streams (maximum daily mean water temperature 20.7–24.6°C; 90th percentile annual exceedence flow≥0.0283m3/s) are common in the Laurentian Great Lakes region of North America, including the state of Wisconsin, but they lack specific and effective bioassessment tools. I used landscape-scale ecological modeling of geographically referenced data on stream location, stream and valley slope, watershed surficial geology, air temperatures, riparian and watershed land cover, watershed road and population densities, and watershed nutrient and wastewater inputs to classify Wisconsin stream sites based on water temperature, flow, and degree of environmental degradation. Fish data from sites classified as perennial coolwater were then analyzed with objective standardized procedures to develop coolwater indices of biotic integrity (IBI). Because of substantial differences in their fish assemblages, separate IBI's were formulated for cool-cold transition (20.7–22.5°C) and cool–warm transition (22.6–24.6°C) streams. The cool–cold transition IBI had five metrics: numbers of darter, madtom, and sculpin species, of coolwater species, and of intolerant species, and the percentages of individuals as tolerant species and as generalist feeders. Scoring criteria differed between northern and southern Wisconsin (boundary at 44.6°N latitude) for the coolwater species metric. The cool–warm transition IBI also had five metrics: numbers of native minnow, of intolerant, and of benthic invertivore species, and percentages of individuals as tolerant species and as omnivores. Scoring criteria differed between small and large streams (boundary at 200km2 watershed area) for the intolerant species, benthic invertivore species, and percentage tolerants metrics. In validation tests, scores for both IBI's were significantly related to independent measures of human disturbance, indicating that the IBI's would be useful tools for assessing the environmental quality of coolwater streams. However, for any given level of human disturbance, scores for both IBI's varied substantially, suggesting that multiple IBI samples from multiple sites would be needed to provide a reliable evaluation of a particular stream segment.

Environmental Variation, Fish Community Composition, and Brown Trout Survival in the Pigeon River, Ottawa County, Michigan

ABSTRACT The Pigeon River, a small coolwater stream in western Michigan, has a history of hydrologic, stream habitat, and water quality degradation that led to the loss of its trout population by the late 1980s. After regulatory and watershed management efforts to reduce point- and nonpoint source pollution in the 1990s, the Michigan Department of Natural Resources reinstituted brown trout ( Salmo trutta ) stocking in 2003. As part of these efforts, we monitored water quality in the Pigeon River each fall between 1996 and 2008, and conducted stream surveys in 2006 and 2007 to evaluate the fish community and outcome of trout stocking. Water quality tended to improve and stabilize through time, although point- and nonpoint source pollution still contributed to water quality problems. Hydrologic instability, caused by wetland drainage, agricultural land use, and irrigation withdrawals from the lower mainstream, created periods of environmental stress. As a result, the fish community of the Pigeon River was dominated by common tolerant warmwater species, typical of agricultural watersheds in southern Michigan. Nonetheless, brown trout surviving from initial stockings in 2003 and 2004 had attained lengths of between 18 and 24 inches by 2007, suggesting the thermal regime, water quality, stream habitat, and forage base of macroinvertebrates and small fish were suitable to maintain a stocked brown trout population. Continued efforts to improve water quality, protect in-stream habitat, reduce high stormflows, and maintain adequate summer baseflows are needed to fully restore environmental conditions for the native fish community and stocked brown trout in the Pigeon River.

Virulence is context-dependent in a vertically transmitted aquatic host–microparasite system

Recent work has suggested that the outcomes of host–symbiont interactions can shift between positive, neutral and negative depending on both biotic and abiotic conditions. Even organisms traditionally defined as parasites can have positive effects on hosts under some conditions. For a given host–parasite system, the effects of infection on host fitness can depend on host vigour, route of transmission and environmental conditions. We monitored sublethal microsporidian infections in populations of Gammarus pseudolimnaeus (Amphipoda: Gammaridae) from four cool water streams in southwestern Michigan, USA. Our objectives were to: (i) infer the mechanism of transmission (horizontal, vertical or mixed) from observed effects of infection on host fitness, (ii) determine if the magnitude of the effects on host fitness is a function of parasite load (infection intensity) compared with simple presence or absence of infection, and (iii) determine if there is variation in parasite effects on host fitness in isolated populations. PCR and DNA sequence analyses revealed that there were two microsporidia present among the four host populations: Dictyocoela sp. and Microsporidium sp. PCR screening of a subset of infected hosts showed that Dictyocoela sp. accounted for 90% of infections and was present in all four G. pseudolimnaeus populations, while Microsporidium sp. was found in two populations but was only relatively common in one. We found very low prevalence in males (∼5%), but high prevalence in females (range: 37–85%). Female fitness was positively associated with infection in two streams, resulting from either higher fecundity or more reproductive bouts. Infection had a negative effect on the number of reproductive bouts in a third population, and no effect on fecundity in a fourth population. Infection intensity explained additional variation in fecundity in one population; females with intermediate infection intensity had higher fecundity than females with either light or heavy infection intensity. Given the high prevalence of infection in females compared with males and the generally weak negative fitness effects coupled with some positive fitness effects, it is likely that both Dictyocoela sp. and Microsporidium sp. are primarily vertically transmitted, feminizing microsporidia. Our results suggest that microsporidian effects on G. pseudolimnaeus fitness were context-dependent and varied with host sex and local environment.

Local Stream Temperature and Drainage Network Topology Interact to Influence the Distribution of Smallmouth Bass and Brook Trout in a Central Appalachian Watershed

ABSTRACT We developed and validated a predictive model of water temperature that could be applied to mapped stream segments in a West Virginia. USA watershed. We then tested the hypothesis that local water temperature and the topology of stream thermal networks interact to determine the distribution of two fishes known to differ in their thermal preference—smallmouth bass (Micropterus dolomieu) and brook trout (Salvelinus fontinalis). Two measures of regional thermal topology were constructed—mean distance to the nearest five coldwater stream segments and distance to the nearest warmwater stream segment. Consistent with expectations, brook trout were more likely to be found in colder streams, and smallmouth bass were in warmer streams. However, brook trout distributions were statistically independent of the regional thermal context suggesting that regional thermal conditions have less influence on brook trout than local thermal conditions in this system. In contrast, there was a significant effect of stream network topology on the distribution of smallmouth bass. Bass were often present in coolwater streams located in close proximity to warmwater mainstems but not in coolwater streams highly isolated from warm water. Furthermore, sympatry in these two species was associated with cool- and coldwater streams located in close proximity to warmwater streams. These findings indicate that overall fish assemblage response to thermal conditions may be the result of species-specific responses to both local thermal conditions and the regional topology of cold, cool, and warmwater streams.

Defining and Characterizing Coolwater Streams and Their Fish Assemblages in Michigan and Wisconsin, USA

AbstractCoolwater streams, which are intermediate in character between coldwater “trout” streams and more diverse warmwater streams, occur widely in temperate regions but are poorly understood. We used modeled water temperature data and fish assemblage samples from 371 stream sites in Michigan and Wisconsin to define, describe, and map coolwater streams and their fish assemblages. We defined coolwater streams as ones having summer water temperatures suitable for both coldwater and warmwater species and used the observed distributions of the 99 fish species at our sites to identify coolwater thermal boundaries. Coolwater streams had June‐through‐August mean water temperatures of 17.0–20.5°C, July mean temperatures of 17.5–21.0°C, and maximum daily mean temperatures of 20.7–24.6°C. We delineated two subclasses of coolwater streams: “cold transition” (having July mean water temperatures of 17.5–19.5°C) and “warm transition” (having July mean temperatures of 19.5–21.0°C). Fish assemblages in coolwater streams were variable and lacked diagnostic species but were generally intermediate in species richness and overlapped in composition with coldwater and warmwater streams. In cold‐transition streams, coldwater (e.g., salmonids and cottids) and transitional species (e.g., creek chub Semotilus atromaculatus, eastern blacknose dace Rhynichthys atratulus, white sucker Catostomus commersonii, and johnny darter Etheostoma nigrum) were common and warmwater species (e.g., ictalurids and centrarchids) were uncommon; in warm‐transition streams warmwater and transitional species were common and coldwater species were uncommon. Coolwater was the most widespread and abundant thermal class in Michigan and Wisconsin, comprising 65% of the combined total stream length in the two states (cold‐transition streams being more common than warm‐transition ones). Our approach can be used to identify and characterize coolwater streams elsewhere in the temperate region, benefiting many aspects of fisheries management and environmental protection.

Enhanced Surface Cooling as an Alternative for Thermal Discharges

Excess heat is an unavoidable by-product of electricity generation from fossil and nuclear fuels. In most cases, excess heat is transferred to a cooling water stream and discharged to a local receiving water body, or processed through on-site cooling towers. In many cases existing discharges are potentially responsible for significant ecological impacts, and regulatory authorities are mandating the construction of cooling towers, often at significant expense. Most existing cooling water discharges are designed to reduce excess temperatures through rapid dilution. Enhanced surface cooling is an alternative approach which involves the development of a thin surface plume, while limiting mixing of the discharge with ambient waters. This process encourages rapid transfer of heat to the atmosphere while limiting impacts to sensitive benthic environments and most of the volume of the receiving water body. This discharge approach may be particularly effective for receiving water bodies which have limited natural ...

Thermal plume transport from sand and gravel pits – Potential thermal impacts on cool water streams

Summary We investigated the potential thermal impacts from below-water-table aggregate extraction on a cool-water stream supporting Brook trout (Salvelinus fontinalis) and cool-water macroinvertebrates. We monitored thermal plumes emanating from an aggregate pit through an unconfined, glacial-outwash aquifer. Our objectives were to complete a detailed assessment to quantify the persistence of thermal plumes in the subsurface, and establish a framework for guiding these investigations as the growing demand for aggregate increases pressures to pursue extraction in ecologically sensitive areas. During a 10-year period, we measured ground and surface water temperatures in an outwash aquifer and cool-water stream, including two periods of intensive monitoring (22 months and 2.5 years) focusing on plume movement from one aggregate pit. We quantified the aquifer hydraulic conductivity K at the laboratory and field scale, and characterized the effective thermal conductivity λ at an unprecedented level of detail. The mean K’s from the multi-scale tests span two-orders of magnitude, 1.8 × 10−4 to 1.7 × 10−2 m s−1, and are related to the test support volume. The saturated λ has a mean of 2.42 W m−1 K−1, ranges from 2.14 to 2.69 W m−1 K−1, and is correlated to stratigraphic units (gravel, sand, and till). The annual temperature amplitude in the pit is 10 °C above up gradient ground water, and our results show that alternating warm and cool plumes persist in the aquifer for 11 months and migrate up to 250 m down gradient. The observed plume velocity (1.2 m d−1) lags the ground water velocity (2.8 m d−1) due to thermal retardation. Furthermore, hydraulic conductivity is shown to vary with the scale of the test and ground water velocities estimated from pumping tests may overestimate thermal plume velocities. While we focused on plume migration, our results demonstrate that assessing impacts on the aquatic community requires an integrated, multi-disciplinary study. This work can guide such assessments.

Thermal behavior of spiral fin-and-tube heat exchanger having fly ash deposit

This research investigates the effect of fly-ash deposit on thermal performance of a cross-flow heat exchanger having a set of spiral finned-tubes as a heat transfer surface. A stream of warm air having high content of fly-ash is exchanging heat with a cool water stream in the tubes. In this study, the temperature of the heat exchanger surface is lower than the dew point temperature of air, thus there is condensation of moisture in the air stream on the heat exchanger surface. The affecting parameters such as the fin spacing, the air mass flow rate, the fly-ash mass flow rate and the inlet temperature of warm air are varied while the volume flow rate and the inlet temperature of the cold water stream are kept constant at 10 l/min and 5 °C, respectively. From the experiment, it is found that as the testing period is shorter than 8 h the thermal resistance due to the fouling increases with time. Moreover, the deposit of fly-ash on the heat transfer surface is directly proportional to the dust–air ratio and the amount of condensate on heat exchange surface. However, the deposit of fly-ash is inversely proportional to the fin spacing. The empirical model for evaluating the thermal resistance is also developed in this work and the simulated results agree well with those of the measured data.