Water Temperature Distribution Research Articles

Analysis on the Effects of Cooling Water Velocity on Temperature Rise of Motorized Spindle

In order to obtain the optimal cooling water velocity, the relationship between motor spindle temperature and cooling water velocity was derived by using the heat transfer and fluid mechanics. When the cooling water velocity was relatively small, its change has significantly influence on cooling effect; But when the cooling water velocity was relative large, the difference in cooling effect was inappreciable. Motor spindles water cooling system based on the software of ANSYS CFX was established. The cooling water velocity and temperature distribution in circular channel was analyzed. Motor spindle temperature of theory and simulation was compared under different cooling water velocity; Experiments were conducted according to the results of the simulation, Experimental temperature is consistent with simulation results, which verify the validity of motorized spindle simulation analysis and theoretical derivation. The study in this paper provides a reference for the motorized spindle selecting the rational velocity of cooling water.

Performance improvement on distillate flux of countercurrent-flow direct contact membrane distillation systems

The theoretical predictions of pure water productivity in a parallel-plate direct contact membrane distillation (DCMD) module using roughened-surface flow channel for enhancing heat transfer enhancement were obtained under countercurrent-flow operations. The device performance improvements with increasing the pure water productivity in saline water desalination were achieved as compared to the concurrent-flow operation. The roughened surface was fabricated using siphonic-blasting with aluminum oxide (Al2O3) sand grains and arc spraying for Ni film coating, and the experimental data were correlated in a simplified expression to predict the heat transfer coefficient for the DCMD device. The pure water productivity and temperature distributions of both hot and cold feed streams are represented graphically with the fluid flow rate and inlet saline temperature as parameters. Both flow-pattern and roughened-surface effects have demonstrated the technical feasibility in the roughened-surface channel device and up to 42.11% of the device performance enhancement was achieved for the countercurrent-flow DCMD system. The influences of operation and design parameters on the pure water productivity with the expense of energy consumption are also discussed.

Vertical Thermal Distribution at the near Dam Region of the Three Gorges Reservoir in the Initial Impoundment Period

Water temperature plays a crucial role in water ecological environment both in the reservoir and downstream area. Three Gorges Project (TGP) is the largest hydraulic engineering in the world, and changes of water quality attract much more attention, especially in the thermal structure since initial impoundment in 2003. In order to clearly understand water temperature distribution after the initial impoundment in the Three Gorges Reservoir (TGR), we monitored the temperature distribution of the Taipingxi section which was not far from the dam from early April to the end of July in 2004. According to the analyzing of the monitoring data of transverse and vertical temperature variation, we could find that when water level went up to 135m above sea level (a.s.l.) or 139m in the initial impoundment phase, the temperature mixed uniformly in transverse direction. Excepting April, there was basically had no temperature difference in vertical direction, even in April, the maximum temperature difference was only 1.39°C within 100 meters (April 22), the average temperature gradient was only 0.014°C/m; Both the temperature of water and atmosphere have similar variation tendency, but the response of the water temperature to atmosphere is delayed, especially the bottom water temperature. The result indicate that the reservoir displayed a mixed thermal structure during initial impoundment phase, therefore, the release had no change before and after impoundment, also had little influence on the aquatic organism and crops at downstream , the work provide a scientific basis for the development of pollution control and ecological protection measure.

Numerical Simulation and Experimental Study of the Tube Receiver's Performance of Solar Thermal Power Tower

A water-vapor tube receiver is a significant component in the solar thermal power tower plant. However, the tube flow performance is much different from others. Because semi-circumference of the tube is heated with an uneven heat flux, which is into a Gaussian distribution in this paper, and the other semi-circumference is insulated. A 5kW- Xe-arc lamp was used to simulate a solar light source. In this study, the effect of different entrance velocity on the flow performance and thermal efficiency of the tube receiver are investigated with numerical and experimental methods. The results of experiment and simulation agree well. The results show that the temperature distribution of water and tube wall are very uneven both in the axial and radial directions. The thermal efficiency of the tube receiver increases with the increase of entrance velocity.

基于光纤Bragg光栅的冰与水交界面附近的温度场分布检测研究

Through the study of ice and water temperature distribution near the interface,a new method of ice detection is found and the theoretical guidance is provided for the research of ice and water transformation.By putting the ice into the water,the ice-water heat transfer have an effect on the water temperature near the interface.Through the study of the temperature distribution,which is 5~9cm、0~4cm、-4~0cm、-5~-9cm to the ice water interface,the fitting section function is got,which named relation function of points from ice and water interface between the distance and temperature.The fitting values and monitoring error is between±0.1~0.3℃.The temperature difference of ice and water interface is bigger;the ice change into water is faster,which is more easily leaded to ice.

20802 受熱期の貯水池流入部における成層形成が光合成藻類の増殖に及ぼす影響

In the shallow of dam reservoirs, a blue-green algae consisted of Microcystis can be partially occurred. In the present work, three major growth factors of the algae which are the water temperature, sunlight, besides that the vertical movement of the algae have been investigated to elucidate the effect of thermal stratification on algae-growth in the inflow reservoir. During the "heating season", the algae blooms are occurred. Then, the water mixing in the vertical direction is difficult due to the water temperature stratification formed by the density deference. Moreover, the water temperature distributions in a vertical direction and the number density of blue-green algae have a good relation with hourly variation.

Thermodynamics and stratification in Xin'anjiang Reservoir(Lake Qiandao)

利用2012年1-12月在新安江水库(千岛湖)6个点位的每月一次的水温及其他环境因子的周年观测资料,分析了水库水温逐月变化、季节变化、垂直分布及温跃层的形成与变化,探讨了温跃层特征量(温跃层深度、厚度、强度)与表层水温、水体透明度的关系.新安江水库表层和中层水温与气温存在显著的线性相关,又以表层水温线性关系最好,而下层水温与气温没有显著相关性,说明下层水温受气温的影响很小,全年处于相对恒温状态.水库表层和中层水温逐月变化明显,呈现夏季最高、春秋季次之、冬季最低的变化趋势,其中中层水温最高值出现的季节较表层水温明显后延,下层水温没有明显的逐月变化和季节变化.水温垂直分布显示,4个季节均存在不同程度的温跃层和温度分层现象,其中水深最深的大坝前水温分层最明显.小金山、三潭岛和大坝前3个典型点位从春季的4月份到冬季的2月份温跃层深度由1.61±0.47 m逐渐增加至39.37±5.35 m,而温跃层厚度和强度则在夏季最高、冬季最低,温跃层随着季节的变化呈现增强稳定减弱消失的周期变化.温跃层深度与水体透明度存在显著正相关,与表层水温存在显著负相关,并基于透明度和表层水温建立温跃层深度的多元线性回归模型.;Based on the in situ investigation data obtained during the period from January to December in 2012 in Xin'anjiang Reservoir, the monthly and seasonal variations, and vertical distributions of water temperature are analyzed. In addition, the thermocline depth, thickness and strength were calculated and the correlations between thermocline depth and water temperature at the surface and secchi disc depth were developed. Significant and positive linear relationships were found between air temperature and water temperature at the surface and middle layers with the marked high correlation coefficient for water temperature at the surface layer. However, no significantly positive relationship was found between air temperature and water temperature at the bottom layer where temperature was maintained almost as an approximate constant indicating that water temperature at the bottom layer was not affected by air temperature. The monthly and seasonal variations of water temperature at the surface and middle layers were as follows:summer > spring, autumn > winter, with a maximum in July or August and a minimum in February or March. The maximal water temperature at the middle layer was lagged to September or October compared to that of the surface layer. In addition, no marked monthly and seasonal variations were found for water temperature at the bottom layer. There is no obvious temperature differences and thermal stratification between the surface and the deep layer water in all four seasons. From April to February, the mean thermocline depth gradually increased from 1.61 ± 0.47 m to 39.37 ± 5.35 m for the three typical sites (Xiaojinshan, Santandao and Dabaqian). In contrast, the thermocline thickness and strength had the highest values in summer and the lowest values in winter. Seasonally, a periodic variation of thermocline from amplification to stabilization, to weakness and further to disappearance was recorded from April to March. Significant and positive linear relationships between the thermocline depth and secchi disc depth, but negative linear relationships between the thermocline depth and water temperature at the surface layer were found. A multiple linear regression model between the thermocline depth and secchi disc depth, water temperature at the surface layer was developed to model the thermocline depth in Xin'anjiang Reservoir.

Pressure dependence of Kapitza resistance at gold/water and silicon/water interfaces

We conducted non-equilibrium molecular dynamics simulations to investigate Kapitza length at solid/liquid interfaces under the effects of bulk liquid pressures. Gold and silicon were utilized as hydrophilic and hydrophobic solid walls with different wetting surface behaviors, while the number of confined liquid water molecules was adjusted to obtain different pressures inside the channels. The interactions of solid/liquid couples were reparameterized accurately by measuring the water contact angle of solid substrates. In this paper, we present a thorough analysis of the structure, normal stress, and temperature distribution of liquid water to elucidate thermal energy transport across interfaces. Our results demonstrate excellent agreement between the pressures of liquid water in nano-channels and published thermodynamics data. The pressures measured as normal stress components were characterized using a long cut-off distance reinforced by a long-range van der Waals tail correction term. To clarify the effects of bulk liquid pressures on water structure at hydrophilic and hydrophobic solid surfaces, we defined solid/liquid interface spacing as the distance between the surface and the peak value of the first water density layer. Near the gold surface, we found that interface spacing and peak value of first water density layer were constant and did not depend on bulk liquid pressure; near the silicon surface, those values depended directly upon bulk liquid. Our results reveal that the pressure dependence of Kapitza length strongly depends on the wettability of the solid surface. In the case of the hydrophilic gold surface, Kapitza length was stable despite increasing bulk liquid pressure, while it varied significantly at the hydrophobic silicon surface.

Study of the Temporal and Spatial Distribution of Water Temperature in Ertan Reservoir Based on Prototype Observation

When a reservoir is built, it will change the hydraulic features of the natural river, and cause thermal stratification which has significantly influence on the reservoir area and downstream ecological environment. Through analysis of the temporal and spatial variations of the observed temperature in terms of the prototype temperature observations in Ertan reservoir, the preliminary conclusions can be gained as follows: the water temperature distribution in Ertan reservoir is basically represented as isothermal in the same depth plane, and as stratifies along water depth. The great monthly variations of water-temperature in the reservoir are affected by the air temperature obviously.

Computation of maximum water temperature in the Beloyarskoe Reservoir

Presented is a three-dimensional model for computing hydrothermodynamic processes in the Beloyarskoe Reservoir used as a basin-cooler of the Beloyarskaya nuclear power plant. In view of the designing of new power units for the station and due to the absence of reliable reservoir-analogs in the region under consideration, the computation is carried out of the distribution of maximum water temperature in the reservoir for natural conditions. The results of these computations are subsequently used as background parameters for designing a system of technical water supply of NPP and for the ecological feasibility report.

Quantifying the importance of daily stream water temperature fluctuations on the hyporheic thermal regime: Implication for dissolved oxygen dynamics

• We model the heat transport in the hyporheic zone by using a Lagrangian approach. • We examine the role of the stream water temperature on hyporheic thermal regime . • We examine the role of hyporheic thermal regime on dissolved oxygen (DO) kinetics. • Via a thermal Damköhler number we relate stream morphology and temperature signal. • We show the impact of temperature variation on the evolution of DO concentration. Water temperature is a primary driver of aquatic organism migration, drift, growth and metabolism in both stream and hyporheic zone. Here, we focus on the role of the naturally occurring daily stream water temperature oscillations on the hyporheic thermal regime and on dissolved oxygen (DO) dynamics within the hyporheic zone. We choose DO as target dissolved element because of its importance for aquatic habitat quality and its role in controlling biogeochemical reactions and pool-riffle morphology as bed form because of its ubiquity and ecological relevance. To address the first objective, we introduce a new thermal Damköhler number, Da T , which is the ratio between the median residence time of stream water and the time scale of daily amplitude attenuation of water temperature within the hyporheic zone. Application of the model to a wide range of pool-riffle dimensions shows the dependence of hyporheic water temperature distribution on hyporheic residence time. The latter is a function of the interaction between stream flow and bed form morphology. Our results show that Da T increases with stream size indicating that large streams have more thermally stable hyporheic zones than small streams. To address the second objective, we analytically solve the heat and dissolved oxygen transport equations through the streambed sediment with isotropic and homogeneous hydraulic properties by means of a Lagrangian approach, under the hypothesis that transverse dispersion can be neglected and the DO reaction rate is temperature dependant. We apply these coupled transport models to characterize the distribution of DO concentrations within the hyporheic zone. This analysis shows a relation between the patterns of water temperature and of DO concentrations with important feedbacks on the life and metabolism of aquatic organisms; as well as on the reaction rates, which control the biogeochemical processes within the streambed sediment. We analyze the effects of temperature variations on the kinetics of DO assuming constant and periodic fluctuations of DO concentrations in the stream water. Our results show that for streams with pool and riffle morphology, the latter effect is more important than that of temperature dependent reaction rates.

새만금호 내 방수제 공사 및 준설에 의한 수리동역학적 특성 변화 수치 모델링

The study area is located on the western coast, and the inner development construction has been ongoing since 2011. The purposes of current study are to effectively simulate and quantitatively predict a temporal and spatial distributions of water temperature and salinity due to the stages of inner development construction in saemangeum reclaimed area. The transient-state numerical modeling using EFDC model is done, and the numerical simulation results are validated reasonably by repetitive numerical model calibration procedures with respect to field measurements of water temperature and salinity. The spatial distributions of water temperature and salinity show similar trends before and after construction of the dikes. In spring season, the salinity has maximum value of 21 psu, while, in summer season, the salinity shows 7 psu in a whole modeling domain. Thus, it is clearly observed that salt water is replaced by freshwater. However, the salinity and temperature reach their initial conditions at the end of the year. The salinity after construction of the dikes is lower than that before construction of them at Mankyeong area. On the other hands, after construction of the dikes, the salinity after dredging operations is higher than that before dredging. Because drastical increasing of water volume in Saemangeum Lake leads to increasing of stagnation time at bottom layer, and salt water is easily intruded to the two estuaries. Therefore, it may be concluded that hydrodynamic characteristics on Saemangeum are dominated by either Mankyeong and Dongjin discharge or sluice gates in/out-flow amounts, and thus they must be properly considered when rigorous and reasonable predictions of water temperature and salinity according to the stages of inner development construction.

Ocean current and temperature analysis using satellite data for the effective operation of SWRO desalination plant in Gijang-gun, Busan, South Korea

The salt concentration of seawater is a significantly sensitive factor in the seawater reverse osmosis desalination plant that applies different pressures in freshwater production, depending on the salinity of the seawater. For the efficient operation of the plant, it needs to be grounded on investigations and analyses of seawater salt concentration and water temperature distribution and change. The conventional research methods, however, have temporal and spatial limitations. This research uses the latest satellite data to analyze the flows and the seasonal temperature distributions of ocean currents that affect mostly the changes in the seawater salt concentration in the neighboring waters of the seawater desalination plant that is being built in Gijang-gun, Busan, South Korea. The results of this research showed that the ocean current in the neighboring waters of Gijang-gun, Busan had a relatively slow velocity (average: 0.05 m/s) but formed very comprehensive flow shapes as the warm and cold currents met and that the degree of the salinity change was significant because the temperatures of the sea surface differed considerably in summer unlike in the other seasons.

Investigation of the dynamic characteristics of a storage tank discharging process for use in conventional air-conditioning system

This paper presents a mathematical model for simulating the heat transfer process in a latent heat thermal energy storage tank containing spherical capsules that can be used in conventional air-conditioning systems. The thermal performance, including the melting point and melting latent heat, of a new phase change material (PCM), which is developed for use in conventional air-conditioning systems, is studied. The buoyancy of the encapsulated PCM during the melting process was specifically considered. The numerical method studied was an effective heat capacity method. An experimental cool storage air-conditioning system with a storage tank was designed and constructed. The model was validated by comparing the numerical results with experimental measurements. The effects of heat transfer fluid (HTF) inlet temperature, Stefan number, flow rate of heat transfer fluid, the complete discharging time, cold storage capacity of the storage tank and distribution of water temperature in the cold storage device were investigated. The results of the study indicate that although an increased flow rate does not appreciably change the total storage capacity, changing the inlet temperature does have an effect on total storage capacity.

Morphodynamic modeling of the basal boundary of ice cover on brackish lakes

AbstractThe analysis considers a cold‐region brackish lake that develops an ice cover on its surface in winter. As the ice cover thickens due to freezing, black ice grows on the bottom side. The freezing process excludes the salt from the ice, resulting in an increase in dissolved salt concentration in the lake water just below the bottom of the ice. The density profile in this type of lake is then governed by two opposing factors: the water temperature distribution generally produces a stable stratification, whereas the excess salinity produced by exclusion tends to increase the density of the upper layers of the lake, resulting in an unstable contribution to stratification. Competition between these two factors can lead to unstable density gradients, so an initially motionless lake with a slowly thickening plane ice cover develops a convective flow field. This flow field can then feed back into the evolution of the morphology of the ice cover itself, resulting in a morphodynamic interaction between water and ice. This paper aims at investigating this morphodynamic instability. A mathematical model for the stability of a lake covered with an initially plane ice cover growing in time is proposed here. The results reveal threshold values of the main dimensionless parameters, expressed in the form of Rayleigh numbers, and in particular define a ratio between buoyancy effects and diffusivity that governs neutral stability conditions. When the system is unstable, i.e., for Rayleigh numbers above ~103 depending on the values of the input parameters, the analysis predicts the growth of convective flow circulation cells responsible for the morphodynamic evolution of the ice‐water interface.

Hydrodynamic Characteristics in a Valley Type Tributary Bay during the Raising and Falling Temperature Periods

The heat changes and distribution in water body provide one of the most important elements of structure influencing a host of chemical and biological processes. After the river-type reservoir was constructed, backwater entered into some tributaries, resulting in slow flow velocities in these tributaries. This paper made a reasonable description on the physical mechanism of hydrodynamic and water temperature distributions in a typical tributary bay, basing the hydrodynamic & water temperature coupled three-dimensional mathematical model. Through a large number of measured hydrologic, temperature and meteorological data, the paper simulated and obtained the hydrodynamic and water temperature distribution structure of the typical tributary bay and its evolution process, and described the hydrodynamic characteristics with precise values during the raising and falling temperature period; it is shown from the results that velocity vectors change displayed the water flow moved in a two-way circulation due to non-equilibrium warming and cooling on riverway cross-section, and the maximum flow velocity, turbulent kinetic energy and vorticity appeared on the surface water body, as well as wall near the tributary bay, and the turbulent kinetic energy is minimum on the center of tributary bay. The simulation experiment accurately captured the circulation phenomena caused by temperature difference, and proposed detailed distributions of flow field and related turbulent physical quantity, showed the strong coupling of flow field and temperature field change.

Going with the Flow: Spatial Distributions of Juvenile Coho Salmon Track an Annually Shifting Mosaic of Water Temperature

A critical challenge for ecologists is to understand the functional significance of habitat heterogeneity and connectivity for mobile animals. Here, we explore how a thermo-regulating fish responds to annual variation in the spatial patterning of thermal and trophic resources. In a third-order stream in coastal Alaska, juvenile coho salmon forage on sockeye salmon eggs at night in cold water and then move to warmer water to increase their digestive capacity. We mapped the spatial distributions of water temperature, juvenile coho salmon, and spawning sockeye salmon across a 5-year period during which summer discharge varied by greater than fivefold. In low flow years, warm water (9–12°C) was only available in thalweg (that is, main-channel) habitat at least approximately 400 m upstream of the cooler habitat (3–7°C) where sockeye salmon spawned. In high flow years, the entire stream thalweg was isothermal at 7–8°C, but inundated off-channel areas generated warm habitats (9–12°C) laterally adjacent to the downstream regions where sockeye salmon spawned. The daytime spatial distribution of juvenile coho salmon shifted from headwater thalweg habitats in low flow years, to downstream off-channel habitats in high flow years. In all years, the majority of juvenile coho salmon sampled during the daytime were found in warm habitat units without sockeye salmon present, yet they exhibited diet contents comprised virtually entirely of sockeye salmon eggs. Thus, thermoregulatory movements by coho salmon were able to track an annually shifting mosaic of water temperature. Our results demonstrate how the spatial habitat heterogeneity and connectivity of intact floodplains can in turn buffer aquatic organisms from high levels of temporal variation in habitat conditions and resource abundance.

Effect of temperature on streambed vertical hydraulic conductivity

In this study, in situ and on-site permeameter tests were conducted in Clear Creek, Nebraska, USA to evaluate the effect of water temperature on streambed vertical hydraulic conductivity Kv. Fifty-two sediment cores were tested. Five of them were transferred to the laboratory for a series of experiments to evaluate the effect of water temperature on Kv. Compared with in situ tests, 42 out of the 52 tests have higher Kv values for on-site tests. The distribution of water temperature at the approximately 50 cm depth of streambed along the sand bar was investigated in the field. These temperatures had values in the range 14–19 °C with an average of 16 °C and had an increasing trend along the stream flow. On average, Kv values of the streambed sediments in the laboratory tests increase by 1.8% per 1 °C increase in water temperature. The coarser sandy sediments show a greater increase extent of the Kv value per 1 °C increase in water temperature. However, there is no distinct increasing trend of Kv value for sediment containing silt and clay layers.

Environmental characteristics of anopheline mosquito larval habitats in a malaria endemic area in Iran

ObjectiveTo determine the effects of environmental parameters of larval habitats on distribution and abundance of anopheline mosquitoes in Rudan county of Iran. MethodsThis cross-sectional study was conducted during the mosquito breeding season from February 2010 to October 2011. The anopheline larvae were collected using the standard dipping method. The specimens were identified using a morphological-based key. Simultaneously with larval collection, environmental parameters of the larval habitats including water current and turbidity, sunlight situation, and substrate type of habitats were recorded. Water samples were taken from breeding sites during larval collection. Before collection of samples, the water temperature was measured. The water samples were analysed for turbidity, conductivity, total alkalinity, total dissolved solid, pH and ions including chloride, sulphate, calcium, and magnesium. Statistical correlation analysis and ANOVA test were used to analyze the association between environmental parameters and larval mosquito abundance. ResultsIn total 2 973 larvae of the genus Anopheles were collected from 25 larval habitats and identified using morphological characters. They comprised of six species: An. dthali (53.21%), An. stephensi (24.22%), An. culicifacies (14.06%), An. superpictus (4.07%), An. turkhudi (3.30%), and An. apoci (1.14%). The most abundant species was An. dthali which were collected from all of the study areas. Larvae of two malaria vectors, An. dthali and An. stephensi, co-existed and collected in a wide range of habitats with different physico-chemical parameters. The most common larval habitats were man-made sites such as sand mining pools with clean and still water. The anopheline mosquitoes also preferred permanent habitats in sunlight with sandy substrates. The results indicated that there was a significant relationship between mean physico-chemical parameters such as water temperature, conductivity, total alkalinity, sulphate, chloride, and mosquito distribution and abundance. ConclusionsThe results of this study showed a correlation between certain environmental parameters and mosquito larvae abundance, and these parameters should be considered in planning and implementing larval control programs.

NUMERICAL SIMULATIONS AND VALIDATION OF WATER FLOW AND HEAT TRANSPORT IN A SUBSURFACE DRIP IRRIGATION SYSTEM USING HYDRUS‐2D

ABSTRACTSubsurface drip irrigation (SDI) systems are often recommended to overcome water scarcity in arid and semi‐arid regions. To properly manage SDI systems, precise prediction of distribution and transport of soil water content and temperature (important soil physical factors for plant growth) around the emitters must be known. In this paper, the computer software package HYDRUS‐2D was used to evaluate the distribution and transport of soil water content and temperature around an emitter in a silt loam soil. The model was validated by comparison with measured data from field experiments involving SDI with emitters installed at 25‐cm soil depths. Model performance in simulating soil moisture and temperature was evaluated by comparing measured and predicted values using three parameters: model efficiency (ME), root mean square deviation (RMSE) and mean bias error (MBE). Values of ME, RMSE and MBE between measured and simulated soil moisture ranged from 0.71 to 0.84, 0.013 to 0.019 and 0.004 to 0.007 and between measured and simulated soil temperature ranged from 0.81 to 0.86, 0.97 to 1.33 and 0.13 to 0.28, respectively. Based on these values, it can be concluded that there was good correspondence between simulations and observations and the HYDRUS‐2D can be commendably used to describe soil water and heat transport properties involving SDI and also for investigating and designing drip irrigation management practices. Copyright © 2013 John Wiley & Sons, Ltd.