scholarly journals Heating Impact of a Tropical Reservoir on Downstream Water Temperature: A Case Study of the Jinghong Dam on the Lancang River

Water ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 951 ◽  
Author(s):  
Bo Jiang ◽  
Fushan Wang ◽  
Guangheng Ni
Keyword(s):  
Solar Radiation ◽  
Water Temperature ◽  
Residence Time ◽  
Cold Water ◽  
Three Dimensional ◽  
Tropical Reservoir ◽  
Ecological Processes ◽  
Outflow Rate ◽  
Different Temperatures ◽  
The Impact

Reservoirs change downstream thermal regimes by releasing water of different temperatures to that under natural conditions, which may then alter downstream biodiversity and ecological processes. The hydropower exploitation in the mainstream Lancang-Mekong River has triggered concern for its potential effects on downstream countries, especially the impact of the released cold water on local fishery production. However, it was observed recently that the annual water temperature downstream of the Jinghong Reservoir (near the Chinese border) has increased by 3.0 °C compared to its historical average (1997–2004). In this study, a three-dimensional (3D) model of the Jinghong Reservoir was established to simulate its hydro- and thermodynamics. Results show that: (1) the impoundment of the Jinghong Reservoir contributed about 1.3 °C to the increment of the water temperature; (2) the solar radiation played a much more important role in comparison with atmosphere-water heat exchange in changing water temperatures; and (3) the outflow rate also imposed a significant influence on the water temperature by regulating the residence time. After impoundment, the residence time increased from 3 days to 11 days, which means that the duration that the water body can absorb solar radiation has been prolonged. The results explain the heating mechanism of the Jinghong Reservoir brought to downstream water temperatures.

scholarly journals Thermal functioning of a tropical reservoir assessed through three-dimensional modelling and high-frequency monitoring

RBRH ◽  
2021 ◽  
Vol 26 ◽  
Author(s):  
Denis Furstenau Plec ◽  
Talita Fernanda das Graças Silva ◽  
Brigitte Vinçon-Leite ◽  
Nilo Nascimento
Keyword(s):  
Water Temperature ◽  
High Frequency ◽  
Three Dimensional ◽  
Frequency Measurement ◽  
Three Dimensional Model ◽  
Anthropogenic Pressures ◽  
Tropical Reservoir ◽  
River Temperature ◽  
Lake Morphology ◽  
The Impact

ABSTRACT Urban lakes and reservoirs provide important ecosystem services. However, their water quality is being affected by anthropogenic pressures. The thermal regime is a strong driver of the vertical transport of nutrients, phytoplankton and oxygen. Thermal stratification can modify biogeochemical processes. In this paper, a three-dimensional hydrodynamic model was implemented and validated with high-frequency measurement of water temperature. The simulation results were in agreement with the measurements. For all simulation period, the model performance was evaluated based on hourly values, presenting a maximum RMSE of 0.65 ºC and Relative Error of 2.08%. The results show that high-frequency measurement associated with a three-dimensional model could help to understand and identify the reasons for the changes in the thermal condition of a shallow urban lake. The impact of the stream inflow on the temperature was highlighted, showing that during higher discharge events, when the river temperature is colder than the lake water, it flows into the lake deeper layers. The inflow water sank to the deeper layers where the lake morphology changes. The model showed an impact along the entire lake, showing the importance of monitoring the inflow water temperature. This modelling tool could be further used to study specific patterns of reservoir hydrodynamics.

Numerical study of asymmetric and axisymmetric thermal jet with entropy generation concept

2021 ◽  
Vol 15 (1) ◽  
pp. 7628-7636
Author(s):  
D. Belakhal ◽  
Kouider Rahmani ◽  
Amel Elkaroui Elkaroui ◽  
Syrine Ben Haj Ayech ◽  
Nejla Mahjoub Saïd ◽  
...  
Keyword(s):  
Entropy Generation ◽  
Numerical Study ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Variable Density ◽  
Current Investigation ◽  
Numerical Resolution ◽  
Different Temperatures ◽  
Density Ratios ◽  
The Impact

In the current investigation, numerical study of a thermal jet of asymmetric (rectangular and elliptical) and axisymmetric (circular) geometry was investigated with variable density to verify the impact of the ratio of density and geometry on the generation of entropy. The central jet was brought to different temperatures (194, 293 and 2110 K) to obtain density ratios (0.66, 1 and 7.2) identical to a mixture jet ((Air-CO2), (Air-Air) and (Air-He)), respectively. Solving the three-dimensional numerical resolution of the Navier Stocks for turbulent flow permanent enclosed on the turbulence model K-εstandard was made. The results acquired are compared with that carried out in previous experimental studies, where it was concluded that, the axisymmetric (circular) geometry increases the entropy generation.

scholarly journals Quantifying the impact of release operations and weather conditions on the flow and temperature dynamics in the cascade-reservoir system

2018 ◽  
Vol 246 ◽  
pp. 01027
Author(s):  
Gang Chen ◽  
Yue Zhai ◽  
Hui Fan ◽  
Xing Fang ◽  
Chuanhai Wang
Keyword(s):  
Water Temperature ◽  
Air Temperature ◽  
Cold Water ◽  
Temperature Drop ◽  
Weather Conditions ◽  
Density Currents ◽  
Three Dimensional Model ◽  
Bottom Water Temperature ◽  
Reservoir System ◽  
The Impact

The objective of this study was to investigate the flow dynamics and temperature characteristics under different reservoir operation scenarios and weather conditions in the river-reservoir system, which can be used to set scientific guidelines for river management and conservation planning strategies. The calibrated three-dimensional model provided simulated unsteady water surface elevation, temperature, velocity and discharge at different layers (depths) in different locations. A series of operation scenarios were modeled to understand and quantify formation, propagation, and disappearance of density currents that are resulted from combinations of daily repeated large release (DRLR) of different durations and solar heating. DRLRs (140 m3/s) with longer durations pushed the bottom cold water further downstream and maintained the bottom water temperature cooler. Variations of weather conditions (e.g., drops of air temperature and solar radiation) directly controled variations of bottom-layer water temperature. The daily drop rate of bottom temperature was related to the rate and duration of air temperature drop. Under the practice for the water turbines running at downstream, it clearly showed the shocking withdrawal and stopping effect from the downstream operation. The velocity for the whole cross-section were almost increased with same magnitude of about 0.1 m/s at GOUS and JML.

scholarly journals The effect of water temperature on the number of moults and growth of juvenile signal crayfish Pacifastacus leniusculus Dana

2009 ◽  
Vol 54 (No. 6) ◽  
pp. 286-292 ◽  
Author(s):  
P. Kozák ◽  
M. Buřič ◽  
J. Kanta ◽  
A. Kouba ◽  
P. Hamr ◽  
...  
Keyword(s):  
Growth Rate ◽  
Water Temperature ◽  
Cold Water ◽  
Pacifastacus Leniusculus ◽  
Warm Water ◽  
Average Weight ◽  
Experimental Conditions ◽  
Stage Of Development ◽  
Different Temperatures ◽  
Rate Frequency

The growth rate, frequency of moulting, and intermoult intervals of juvenile <I>Pacifastacus leniusculus</I> were studied under experimental conditions over a period of 3 months. Juveniles were reared individually in small boxes at two different temperatures: 14.31 ± 0.64°C (cold water) and 20.54 ± 0.69°C (warm water). Although the average weight and length of consecutive stages were similar at both temperatures, juveniles in warm water attained more moults. Within the age group juveniles achieved a higher length and weight in warm water than in cold water. Three month-old juveniles reached 147 mg and 18.5 mm in cold water at the 6<sup>th</sup> stage of development, and 259 mg and 22.2 mm in warm water at the 8<sup>th</sup> stage. Specific growth rate (SGR) decreased (5.6 and 10.4 for cold and warm water in the first stage, respectively) and reached final values of 1.4 and 1.5 after 3 months of growth. SGR was significantly higher in warm water and showed negative correlations with the number of days after hatching and number of moults. Duration of intermoult periods was significantly influenced by water temperature, with five moults attained in cold water compared to seven in warm water. All intermoult periods were significantly longer in cold water than in warm water. The average percent weight and length increments decreased with increasing number of moults, length, weight and number of days after hatching. In warm water increments were higher (89.8% and 21.8% for weight and length, respectively) than in cold water (68.5% and 20.3% for weight and length, respectively), and the decrease was faster. However, the final values were similar at both temperatures (about 36% and 11% for weight and length, respectively). The mean absolute weight and length moult increments were not significantly influenced by water temperature. Although the temperature influenced growth due to the number of moults, the duration of individual intermoult periods did not affect the weight and length of juveniles in particular stages.

scholarly journals Can the impacts of cold-water pollution on fish be mitigated by thermal plasticity?

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
M A Parisi ◽  
R L Cramp ◽  
M A Gordos ◽  
C E Franklin
Keyword(s):  
Water Pollution ◽  
Metabolic Rate ◽  
Water Temperature ◽  
Cold Water ◽  
Thermal Sensitivity ◽  
Exposure Period ◽  
Thermal Pollution ◽  
Locomotor Performance ◽  
Thermal Plasticity ◽  
The Impact

Abstract Increasingly, cold-water pollution (CWP) is being recognised as a significant threat to aquatic communities downstream of large, bottom-release dams. Cold water releases typically occur during summer when storage dams release unseasonably cold and anoxic hypolimnetic waters, which can decrease the temperature of downstream waters by up to 16°C. Depending on the release duration, these hypothermic conditions can persist for many months. The capacity of ectothermic species to tolerate or rapidly adjust to acute temperature changes may determine the nature and magnitude of the impact of CWP on affected species. This study assessed the impacts of an acute reduction in water temperature on the physiological function and locomotor performance of juvenile silver perch (Bidyanus bidyanus) and examined their capacity to thermally compensate for the depressive effects of low temperatures via phenotypic plasticity. Locomotor performance (Ucrit and Usprint) and energetic costs (routine and maximum metabolic rate) were measured at multiple points over a 10-week period following an abrupt 10°C drop in water temperature. We also measured the thermal sensitivity of metabolic enzymes from muscle samples taken from fish following the exposure period. Cold exposure had significant depressive effects on physiological traits, resulting in decreases in performance between 10% and 55%. Although there was partial acclimation of Ucrit (~35% increase in performance) and complete compensation of metabolic rate, this occurred late in the exposure period, meaning silver perch were unable to rapidly compensate for the depressive effects of thermal pollution. The results of this study have substantial implications for the management of cold water releases from large-scale dams and the conservation of native freshwater fish species, as this form of thermal pollution can act as a barrier to fish movement, cause reduced recruitment, ecological community shifts and disruptions to timing and success of reproduction.

scholarly journals Financial Analysis of the Use of Two Horizontal Drain Water Heat Recovery Units

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4113 ◽  
Author(s):  
Kamil Pochwat ◽  
Sabina Kordana-Obuch ◽  
Mariusz Starzec ◽  
Beata Piotrowska
Keyword(s):  
Heat Exchanger ◽  
Water Temperature ◽  
Heat Recovery ◽  
Cold Water ◽  
Financial Analysis ◽  
Global Scale ◽  
Drain Water ◽  
Actual Distribution ◽  
Cold Water Temperature ◽  
The Impact

The growing interest in the use of unconventional energy sources is a stimulus for the development of dedicated devices and technologies. Drain water heat recovery (DWHR) units can be an example of such devices. They allow the recovery of part of the heat energy deposited in grey water. This paper describes the results of research on the assessment of the financial profitability of the use of two horizontal heat exchanger solutions, taking into account the actual distribution of cold water temperature during the operating year in the plumbing and two operating regimes of the premises as the residential and service facilities. The analysis showed that the use of a horizontal heat exchanger with increased efficiency in a dwelling in a 15-year life cycle allowed for achieving more than twice as much savings (reaching up to EUR 1427) compared to a classic horizontal heat exchanger. At the same time, it was shown that the installation of this type of equipment was more profitable the greater the water consumption of the premises. The article also notes the impact of cold water temperature in the installation on the results of the analysis. It was featured that taking temperature on the basis of installation design recommendations led to significant distortions in the financial analysis. On the other hand, comparing the method of averaging the cold water temperature (daily, monthly and yearly), it was determined that averaging the temperature over the annual cycle was an acceptable simplification of the model. The research results presented in the paper have a practical aspect and may constitute guidelines for designers and potential investors. In addition, they can be an incentive to continue research on heat exchangers by other scientific centers, which on a global scale will increase the universality of their use.

scholarly journals Impact of increase in temperature and light intensity on development and metamorphosis of hatchery reared silver pompano Trachinotus blochii (Lacepede, 1801) larvae

2018 ◽  
Vol 65 ◽  
Author(s):  
R. Jayakumar ◽  
M. Sakthivel ◽  
A. K. Abdul Nazar ◽  
G. Tamilmani ◽  
P. Rameshkumar ◽  
...  
Keyword(s):  
Growth Rate ◽  
Light Intensity ◽  
Water Temperature ◽  
Light Stress ◽  
Growth Reduction ◽  
Light Intensities ◽  
Different Temperatures ◽  
The Impact ◽  
Trachinotus Blochii

The impact of increase in temperature and light intensity on development and metamorphosis of hatchery produced larvae of silver pompano <em>Trachinotus blochii</em> (Lacepede, 1801) was studied. Two sets of larviculture tanks (Set 1 and Set 2) in triplicate were exposed to two different temperatures and varying light intensities. The growth of the larvae from day one to day 25 post-hatch (dph) and metamorphosis were studied. It was found that an increase of 2°C water temperature and increased light intensity significantly reduced the growth. The percentage of growth reduction gradually decreased and got stabilised towards the end of larviculture with a mean reduction of 15%. Further, a delay of three days in metamorphosis was also observed in Set 2. The reduced growth rate coupled with change in pigmentation of larvae can be considered as the resilience response of the larvae to combat temperature and light stress without compromising survival.

scholarly journals Deep-mixing and deep-cooling events in Lake Garda: Simulation and mechanisms

2021 ◽  
Vol 80 (2) ◽  
Author(s):  
Bouke Biemond ◽  
Marina Amadori ◽  
Marco Toffolon ◽  
Sebastiano Piccolroaz ◽  
Hans Van Haren ◽  
...  
Keyword(s):  
Water Temperature ◽  
Deep Water ◽  
Cold Water ◽  
Vertical Mixing ◽  
Three Dimensional ◽  
Surface Cooling ◽  
Deep Mixing ◽  
Lake Garda ◽  
Turbulence Production ◽  
Strong Winds

A calibrated three-dimensional numerical model (Delft3D) and in-situ observations are used to study the relation between deep-water temperature and deep mixing in Lake Garda (Italy). A model-observation comparison indicates that the model is able to adequately capture turbulent kinetic energy production in the surface layer and its vertical propagation during unstratified conditions. From the modeling results several processes are identified to affect the deep-water temperature in Lake Garda. The first process is thermocline tilting due to strong and persistent winds, leading to a temporary disappearance of stratification followed by vertical mixing. The second process is turbulent cooling, which acts when vertical temperature gradients are nearly absent over the whole depth and arises as a combination of buoyancy-induced turbulence production due to surface cooling and turbulence production by strong winds. A third process is differential cooling, which causes cold water to move from the shallow parts of the lake to deeper parts along the sloping bottom. Two of these processes (thermocline tilting and turbulent cooling) cause deep-mixing events, while deep-cooling events are mainly caused by turbulent cooling and differential cooling. Detailed observations of turbulence quantities and lake temperature, available at the deepest point of Lake Garda for the year 2018, indicate that differential cooling was responsible for the deep-water cooling at that location. Long-term simulations of deep-water temperature and deep mixing appear to be very sensitive to the applied wind forcing. This sensitivity is one of the main challenges in making projections of future occurrences of episodic deep mixing and deep cooling under climate change.

scholarly journals Deep-mixing and deep-cooling events in Lake Garda: Simulation and Mechanisms

2021 ◽  
Author(s):  
Bouke Biemond ◽  
Marina Amadori ◽  
Marco Toffolon ◽  
Sebastiano Piccolroaz ◽  
Hans van Haren ◽  
...  
Keyword(s):  
Water Temperature ◽  
Deep Water ◽  
Cold Water ◽  
Vertical Mixing ◽  
Three Dimensional ◽  
Surface Cooling ◽  
Deep Mixing ◽  
Lake Garda ◽  
Entire Depth ◽  
Strong Winds

&lt;div&gt; &lt;div&gt; &lt;div&gt; &lt;p&gt;A calibrated three-dimensional numerical model&amp;#160;&lt;span&gt;(Delft3D) and in-situ observations are used to study the relation between deep water temperature and mixing in Lake Garda (Italy). A model-observation comparison indicates that the model is able to adequately capture the production of turbulent kinetic energy in the surface layer and its vertical propagation during unstratified conditions. Here, the model is used as a support to identify the main processes causing deep water cooling and deep mixing in the lake. The analysis indicated that two processes cause mixing over the entire depth. The first process is thermocline tilting due to strong and persistent winds. This is found to generate a temporary disappearance of stratification followed by vertical mixing over the entire depth. The second process is turbulent cooling, which arises as a combination of negative-buoyancy produced by surface cooling and turbulence injection from strong winds. Turbulent cooling acts when vertical temperature gradients are absent over the whole depth and cools and mixes the lake over its entire vertical. The third identified process is associated to differential&amp;#160;cooling between the shallow southern part and the deep northern trunk. This generates the advection of cold water from the southern, colder and well-mixed basin to the norther trunk along the sloping bottom of the lake. Such differential cooling is found to be a consequence of the turbulent cooling and is not associated with mixing over the entire depth in the northern trunk. Available observations indicate that the three processes identified from the model indeed occur in Lake Garda. Long- term simulations of deep water temperature and related deep mixing appear to be very sensitive to the atmospheric forcing,&amp;#160;whose accurate reproduction is essential for the prediction of the future occurrence of deep mixing events.&lt;/span&gt;&lt;/p&gt; &lt;/div&gt; &lt;/div&gt; &lt;/div&gt;

Analysis of a CRDM Nozzle Break LOCA Without Scram Using the U.S. NRC Coupled Code TRAC-M/PARCS

2002 ◽  
Author(s):  
A. Cuadra ◽  
J. Ragusa ◽  
T. Downar ◽  
K. Ivanov
Keyword(s):  
Nuclear Power ◽  
Cold Water ◽  
Three Dimensional ◽  
Control Rod ◽  
Operation Conditions ◽  
Wide Range ◽  
Core Conditions ◽  
The Impact ◽  
Power Response ◽  
The U.S

Recently, through-wall circumferential cracks in several control rod drive mechanism (CRDM) nozzle penetrations were detected at the Oconee-3 nuclear power plant. The presence of these cracks was seen as a potential precursor to a small break loss of coolant accident. In order to assess the impact of a postulated failure of a CRDM housing, analyses were performed using the U.S. NRC coupled thermal-hydraulics and neutronics code TRAC-M/PARCS. Although deemed highly unlikely, it was assumed that no control rods inserted in order to bound any possible reactivity transient associated with the break. The thermal-hydraulic model used to perform the study is based on an existing model of Oconee, built for PTS analysis, which models the whole plant and some of its control systems. A refined vessel model based on a TMI model was used to increase the resolution of the results and facilitate coupling to PARCS. All relevant ECCS systems were modeled and the control system allowed for, in addition to automatic actions, some assumed operator intervention. In particular, HPI throttling was modeled to maintain the hot leg subcooled at 42 +/- 7 K, and prevent an excessive amount of cold water from being injected into the system. A spatial kinetics analysis of this event was necessary because of the wide range of core conditions which occurred during the transient, from hot full power operation conditions to the cold zero power shutdown state. Analysis of the event with point kinetics and “best estimate” reactivity coefficients resulted in significant miss-prediction of the core power response. Conversely, the three-dimensional kinetics solution with cross section data generated over the entire range of the event led to a more accurate calculation of the power response and the overall analysis of the system transient response. This paper will describe the analysis of the control rod drive nozzle break event without scram using TRAC-M/PARCS.

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