Tank Outlet Research Articles

Turbulence in continuous flow surface aeration systems.

Turbulence characteristics in an optimal continuous surface aeration system were investigated in this study. The experimental system consists of a rectangular tank, where flow is driven by equally spaced aerators placed on the liquid surface. The mass-transfer coefficient and turbulent parameters at the tank's inlet and outlet were measured to enable analysis of their interdependent relationships. The turbulence parameters are linked closely to the system's mass-transfer process. Turbulent bursting analysis has shown that ejection and sweep events govern the hydrodynamics of the systems. Turbulent intensity increases with increasing speed of rotation, and consequently the mass-transfer coefficient also increases. The universal probability distribution functions of the velocity fluctuations in continuous flow surface aeration systems follow the Gram-Charlier series, based on exponential distribution, and the theoretical and experimental curves match.

Research on the variation law of heating temperature field and the effective energy utilization rate of a steam coil for the floating roof tank

ABSTRACTAs per the way of heat transfer and its main characteristics for oil tank, the theoretical model of steam coil heating in large oil storage tanks was established. The Visual Basic language was applied for calculating the temperature field of crude oil in the heating process by the trial method procedure, and the variation law of temperature field and the energy effective utilization rate of oil tank could be obtained. Results show that the temperature of crude oil and the energy effective utilization rate became higher with the increase of the ambient temperature, steam pressure, and the reduction of storage liquid level. The temperature of crude oil near the steam coil became higher with the increase of steam pressure. The oil temperature at the tank outlet presented periodic change, which was affected simultaneously by the steam pressure and the ambient temperature.

Transient pressure measurements at part load operating condition of a high head model Francis turbine

Hydraulic turbines are operating at part load conditions depending on availability of hydraulic energy or to meet the grid requirements. The turbine experiences more fatigue during the part load operating conditions due to flow phenomena such as vortex breakdown in the draft tube and flow instability in the runner. The present paper focuses on the investigation of a high head model Francis turbine operating at 50% load. Pressure measurements have been carried out experimentally on a model Francis turbine. Total six pressure sensors were mounted inside the turbine and other two pressure sensors were mounted at the turbine inlet pipe. It is observed that the turbine experiences significant pressure fluctuations at the vaneless space and the runner. Moreover, a standing wave is observed between the pressure tank outlet and the turbine inlet. Analysis of the data acquired by the pressure sensors mounted in the draft tube showed the presence of vortex breakdown co-rotating with the runner. The detailed analysis showed the rotating and plunging components of the vortex breakdown. The influence of the rotating component was observed in the entire hydraulic circuit including distributor and turbine inlet but not the plunging one.

A Novel Prototype of a Small-Scale Solar Power Plant: dynamic Simulation and Thermoeconomic Analysis

The paper presents an innovative prototype of a solar power plant, purposely designed for small-scale applications such as residential and/or small commercial buildings. The system consists of 10 kWe Organic Rankine Cycle (ORC) plant and innovative solar thermal collectors. In particular, 235 m2 of flat-plate evacuated solar collectors are designed to heat diathermic oil up to 180°C. A variable volume pump is managed by a feedback controller in order to obtain the desired outlet set point temperature for the different weather/load conditions. The hot diathermic oil passes through a storage tank, which is adopted with the purpose to reduce the oscillations due to the solar radiation variability. By means of the tank, a better exploitation of solar energy is also achieved, reducing the time-shift between production and demand. For achieving a constant ORC inlet temperature the tank outlet hot diathermic oil passes through a gas-fired burner, which provides auxiliary additional thermal energy. Therefore, the ORC simultaneously produces electrical energy and low temperature (45°C) cogeneration heat. This solar power plant was dynamically simulated in TRNSYS environment. The simulation tool includes a novel model in order to simulate the dynamic thermal behavior of solar collectors, whereas the ORC dynamic was simulated by means of a performance data map provided by the manufacturer. The model also includes a tool for the calculation of energy and economic parameters and the evaluation of the optimum thermoeconomic configuration. Results indicated that the best pay-back period is obtained for a solar field area of about 200 m2 and a solar fraction of about 75%. Nevertheless, the system may be competitive from the economic point of view only if incentives can be made available, as commonly occurs for renewable applications, i.e., solar systems. This prototypal system aims to become a potential solar power system for small residential and/or commercial buildings. The presented study will be suitably used as a basis for the installation of a working prototype in located Naples, Italy.

Numerical Analysis of Thermal Stratification in Large Horizontal Thermal Energy Storage Tanks

This paper presents the results of a numerical study on the thermal performance of large horizontal thermal energy storage tanks. The numerical model was validated using measurements obtained from Drake Landing Solar Community (DLSC), which is located in Alberta, Canada. A total of seven different baffle configurations were assessed for a range of operating conditions. Characterization of the tank performance was done by monitoring the tank outlet temperature and computing the Huhn efficiency, which is a characterization index based on the second law of thermodynamics. Results show that the current tanks at DLSC experience excessive mixing due to fluid entrainment from the inlet jet. A newly introduced design that confines the inlet jet mixing shows the potential to enhance the level of stratification during charging or discharging at a constant temperature. In addition, most designs tested have a relatively high level of stratification during charging, discharging, and simultaneous charging and discharging, but fail to sustain the level of stratification when a positive buoyant jet is introduced.

Performance evaluation of a vapor injection refrigeration system using mixture refrigerant R290/R600a

This work presents a performance evaluation of a vapor injection refrigeration system using a mixture refrigerant R290/R600a, through steady-state simulations used to accomplish a parametric analysis considering the influence of the refrigerant composition over the following parameters: COP; compressor power; refrigerant mass flow rate; refrigerant temperature glide; mass flow ratio between vapor and feed streams in the flash tank; liquid and vapor composition of flash tank outlet streams and compression ratio. Two cases, denominated A and B, considering different fixed temperatures at the refrigeration system were studied and their performances were compared with the one of a basic vapor compression cycle. A maximum COP was obtained for a mixture containing 40 wt% of R290. COP of vapor injection refrigeration cycle is 16–32% greater than the one of a vapor compression cycle, depending on the composition of the mixture refrigerant and pressure drop at the cycle upper-stage expansion valve.

Optimizing the Locations of Intermediate Rechlorination Stations in a Drinking Water Distribution Network

The preservation of the water quality in the distribution network requires maintaining permanently minimum residual chlorine at any point of the network. This is possible only if we plan chlore’s injections in various points of the network for intermediate rechlorination, or when increasing the initial level of chlorine in the tank outlet. In the latter case, there is a risk of disruption of the taste and smell of water for consumers near the tanks. Therefore, to avoid an excessive increase in the chlorine concentration in the tanks and to avoid affecting the taste of the distributed water, intermediate rechlorination stations should be implemented. These stations will proceed with the chlorine regulation. Given the high cost of the implementation of such stations, the optimization of the number and the choice of location of these stations are needed. This paper is focused on the implementation of an algorithm for such optimization. We used dynamic programming in this algorithm. Performance tests of our decision support system were done on real sites of the Wilaya Rabat-Sale (network of Morocco's capital).

Effectiveness of Vetiver System for the Treatment of Wastewater from an Institutional Kitchen

This paper investigates the potential of using Vetiver System (VS) for the treatment of wastewater generated from an Institutional kitchen. Vetiver grass is a perennial grass with deep root and has high biomass system. Researchers proved that Vetiver grass have extraordinary ability to with stand extreme environmental conditions such as elevated levels of salt, acidity, alkalinity, sodicity as well as whole range of heavy metals, nitrogen (N), and phosphorous (P). There are around 800 inmates in this institutional hostel; as a result large amount of wastewater have been produced everyday in campus kitchen wastewater outlet. A pilot experimental setup was made for the treatment of wastewater produced from the wastewater outlet and the capability of using VS for the treatment was studied. Experimental setup includes 5 drums of130 liters capacity and is filled with soil, the Vetiver grass is planted in them and was connected in series using different pipe fittings. Each tank has outlet at the bottom of the tank and inlet provided at top with sufficient free board. The wastewater was supplied through the inlet of the 1st tank and was allowed to pass through the 2nd, 3rd, 4th and 5th tanks and the treated water was collected at the outlet of the 5th tank. The water quality parameters of wastewater and treated water were analysed and the effectiveness of using VS for the treatment was assessed. The various water quality parameters like pH, turbidity, acidity, alkalinity, BOD, COD, DO, Ecoli were analysed for the wastewater and treated water. It is observed that the wastewater treatment using VS has significant potential to reclaim the wastewater. The VS is able to remove 80 to 85% of BOD, 85 to 90% of COD, and 85% of total Coliform. Most of the water quality parameters are within permissible limits as per IS 10550, 2012 and IS 2292, 1992.

Short report on the ectoparasitic fauna from a wild Epinephelus marginatus and osmotic shock efficiency on their removal

Short report on the ectoparasitic fauna from a wild Epinephelus marginatus and osmotic shock efficiency on their removal

Nondeterministic computational fluid dynamics modeling of Escherichia coli inactivation by peracetic acid in municipal wastewater contact tanks.

Wastewater disinfection processes are typically designed according to heuristics derived from batch experiments in which the interaction among wastewater quality, reactor hydraulics, and inactivation kinetics is often neglected. In this paper, a computational fluid dynamics (CFD) study was conducted in a nondeterministic (ND) modeling framework to predict the Escherichia coli inactivation by peracetic acid (PAA) in municipal contact tanks fed by secondary settled wastewater effluent. The extent and variability associated with the observed inactivation kinetics were both satisfactorily predicted by the stochastic inactivation model at a 95% confidence level. Moreover, it was found that (a) the process variability induced by reactor hydraulics is negligible when compared to the one caused by inactivation kinetics, (b) the PAA dose required for meeting regulations is dictated equally by the fixed limit of the microbial concentration as well as its probability of occurrence, and (c) neglecting the probability of occurrence during process sizing could lead to an underestimation of the PAA dose required by as much as 100%. Finally, the ND-CFD model was used to generate sizing information in the form of probabilistic disinfection curves relating E. coli inactivation and probability of occurrence with the average PAA dose and PAA residual concentration at the outlet of the contact tank.

Hourly dynamic simulation of solar ejector cooling system using TRNSYS for Jordanian climate

This work describes a simulation program developed on the TRNSYS-EES softwares. This program is used to design the solar collector subsystem components and to evaluate the performance of the solar ejector cooling system with R134a as a refrigerant. In addition dynamic hourly simulation of 7kW solar ejector cooling system (SECS) constant pressure mixing components, using TRNSYS software is carried out. The performance of solar collector and the overall system performance are investigated and the ejector sub-system is modeled with EES software.The solar collector type, area, storage tank size, and the flow rate through the cycle are optimized. Solar collector type and area are selected based on the maximum energy gain, where the maximum energy gain is a measure of the collector performance. The system performance is computed in the form of desired outlet temperature to run 7kW cooling cycle. The effect of tilt angle on the solar system performance is investigated and the optimum tilt angle for the best performance of the system is determined. Selection of the best refrigerant to meet the cooling requirement with the maximum COP is studied. In addition, the time fraction of the storage tank outlet temperature for different collector areas, at a mass flow rate of 50kg/hm2 is investigated. It is found that evacuated tube type has better performance than the flat plate type, where each collector is anchored at its optimal tilt angle of 28°. Furthermore, the energy required of the 7kW-cooling-system is adequately met with the selection of an evacuated-tube solar collector system with an area of 60–70m2. The solar fraction is in the range of 0.52–0.542 and the corresponding time fraction is 5.04h/days. Hourly and monthly simulation of SECS, which is supplemented with 2m3 storage tank size and operated at a flow rate of 50kg/h per square meter of collector area is carried out. Under peak solar radiation and highest ambient temperature, the overall system efficiency has a minimum value of 0.32, whereas the COPejec of the ejector cooling cycle for this model is in the range of 0.52–0.547, the solar collector efficiency is between 0.52 and 0.92, and the overall COPo is in the range of 0.32–0.47.

Performance optimization of an air source heat pump water heater using mathematical modelling

In South Africa, there is an ongoing constraint on the electricity supply at the national grid to meet the demand. Eskom is implementing various measures such as the Integrated Demand Management and the promotion and encouragement of the use of energy efficient devices like an Air Source Heat pump (ASHP) water heater to replace the high electrical energy consuming conventional geysers for sanitary hot water production. The ASHP water heater market is fast gaining maturity. A critical mathematical model can lead to performance optimization of the systems that will further result in the conservation of energy and significant reduction in global warming potential. The ASHP water heater comprises of an ASHP unit and a hot water storage tank. In this study, a data acquisition system (DAS) was designed and built which monitored the energy used by the geyser and the whole building, the temperature at the evaporator, condenser, tank outlet hot water, tank inlet cold water, the ambient temperature and relative humidity in the vicinity of the ASHP evaporator. It is also worthy to mention that the DAS also included to a flow meter and two additional temperature sensors that measured the volume of water heated and inlet and outlet water temperature of the ASHP. This work focused on using the mathematical equation for the Coefficient of Performance (COP) of an ideal Carnot’s heat pump (CHP) water heater to develop basic computation in M-file of MATLAB software in order to model the system based on two reservoir temperatures: evaporator temperatures (Tevp) of 0°C to 40°C (approximated to ambient temperature, Ta) and condenser temperatures (TCon) set at 50°C, 55°C and 60°C (approximated to the hot water set temperature of 50°C, 55°C and 60°C) respectively. Finally, an analytical comparison of a CHP water heater to the practical ASHP water heater was conducted on a hot water set point temperature of 55°C. From the modelling results, it can be deduced that at 0°C Tevp, the COP was 5.96 and 2.63 for CHP and ASHP water heater respectively, at a hot water set temperature of 55°C. Above 20°C Tevp, the rate of change of COP increased exponentially for the ideal CHP system, but was constant at 0.01/°C for the practically modelled ASHP water heater.

Influence of flow distribution on the thermal performance of dual-media thermocline energy storage systems

Dual-media molten-salt thermocline thermal energy storage (TES) systems can be used to maintain constant power production at Concentrated Solar Power (CSP) plants independent of weather changes at costs less than that of traditional two-tank molten-salt storage systems. The flow distribution is a critical parameter affecting the thermal performance but has rarely been considered for dual-media TES systems in previous studies. This study analyzes the influence of the flow distributions at the inlet and outlet of a salt-rock dual-media thermocline TES tank on the thermal performance. The flow distribution is characterized by radial component, and a two-temperature model is used to investigate the thermal performance of the thermocline tank. The model is first validated against experiment data available in the literature and then used to study the discharge process of the thermocline thermal storage tank for various flow distributions. The results show that even with a large (80% of the area) flow blockage at the inlet, the flow distribution has only a limited influence on the useable energy output (<3% change) of the dual-media storage tank. In fact, the flow non-uniformities reduce the thickness of the thermocline layer and slightly increase the useable energy output, whereas non-uniformities at the top outlet slightly decrease the output. An entropy generation analysis, including the effects from diffusion and interstitial heat transfer, is performed to further explain these phenomena. The interstitial heat transfer is found to be the main cause for the entropy generation in the discharge. Flow non-uniformities are also found to reduce the entropy generation.

The Optimization of Solar Heating System with Seasonal Storage Based on a Real Project

This article mainly describes a real project heating by solar energy. By introducing its details and the control strategies, we may discover the advantages in utilizing the technology and the disadvantages to improve. By establishing a TRNSYS model of the project and design a orthogonal schedule L36(63*33), we can simulate the operating condition to discover the relationships between each influences thus provide a optimum proposal. We can come to a conclusion that if the parameter of H/D of the pool is about 0.6-1.5, the system will get better heat storage. Of all influences, the solar areas takes up the vital part, the volume of the pool takes the second place. To this project, it is suggested the parameter to be 260m2 collectors, 500m3pool, 30m3 tank, the storing pump runs when the tank outlet temperature reaches 55̊C and the storing begins from May 1st.

The Numerical Simulation Analysis of Flow Field in Level Control Valve of Water Storage Tank

Level control valve of water storage tank is installed in the outlet of tank, which control the water level of water storage tank by adjusting the water emissions, which make great significance for the safe operation of the super (super) criticality thermal power unit boiler . Complete the simulation analysis of internal flow field by the method of numerical simulation ,in order to achieve structure improvements of level control valve of water storage tank, that make level control valve of water storage tank better meet the work requirements. Establish flow channel model and mesh models of level control valve of water storage tank in various stages of the open process. Make three dimensional viscous numerical simulation of the internal complex flow field by the computational fluid dynamics software of ANSYS CFX. The error between the simulation values of the flow coefficient and the theoretical values , trial values is less than 5% ,which verifies the correctness of the simulation results . Get pressure contour , velocity streamline diagrams and outlet mass flow of level control valve of water storage tank in various stages of the open process. According to the pressure contours and velocity streamline diagrams, make detailed analysis of the flow field of level control valve of water storage tank. According to the dates of outlet mass flow, fit the flow characteristic curve of level control valve of water storage tank. Provide a theoretical basis for the structural design of level control valve of water storage tank.

New Pogo Analysis Method Using Rational Fitting and Three-Dimensional Tank Modeling

Considering the flexibility of a liquid rocket propellant tank and the importance of the relationship between oscillatory pressure and outflow near the tank outlet, a three-dimensional modeling technique is developed to provide a more accurate tank simulation. This paper also presents a rational function fitting method that could be used to transform transcendental equations of a feed-line transfer function into a homogeneous second-order matrix form. It is shown that this form of feed-line transfer function can be easily coupled together with governing equations of a liquid rocket structural system, which could be further solved for system stability using mature eigenvalue solvers. By comparison with the telemetry data and traditional methods, this pogo stability method proves to be highly accurate and efficient.

Storm sewer pressurization transient – an experimental investigation

ABSTRACTPipe pressurization is examined experimentally by 144 laboratory experiments in a circular tilting pipe between two tanks, in which the transient was triggered by sudden closing of the downstream tank outlet. The experiments cover ranges of values of slope, velocity and filling ratio of the open-channel flow not explored in previous studies. Situations involving considerable air quantity and consequent intense pressure oscillations were also reproduced. Two different pressurization patterns, defined as “smooth” and “abrupt”, were observed, but only the abrupt pattern produced intense pressure oscillations. The comparison among all the abrupt pressurization surges showed how the oscillations changed in starting time, intensity and duration as the pipe slope, the flow rate and the free-surface flow filling ratio varied. The experimental results also stressed the major role of entrapped air in determining the oscillation characteristics, showing that oscillations were actually produced by the pulsating of large air pockets during their migration along the pipe and their release through the upstream manhole.

Reduction of COD in wastewater from a textile industry by Electro-fenton process

&lt;div&gt; &lt;p&gt;Advanced oxidation processes (AOPs) have led the way in the treatment of aqueous waste and are rapidly becoming the chosen technology for many applications. In this paper, COD reduction of textile industry wastewater by electro-Fenton (EF) oxidation, was studied at batch experimental conditions. The wastewater samples with a COD of 590 mg l&lt;sup&gt;-1&lt;/sup&gt; in average were taken from the outlet of an equalization tank of a textile industry in the Marmara Region in Turkey. The wastewater samples were treated in a batch reactor equipped with two iron electrodes. The EF tests were conducted at different H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; doses such as 313, 626, 940, and 1253 mg l&lt;sup&gt;-1&lt;/sup&gt; and constant electrical power of 24 W and pH of 3. For each EF test electricity consumption was determined based on per unit of COD mass removed&lt;br /&gt; (kW kg&lt;sup&gt;-1&lt;/sup&gt;). The COD removal increased with decreasing H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; dose. The highest treatment efficiency was attained at 313 mg l&lt;sup&gt;-1&lt;/sup&gt; of H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;, by which more than 85% of COD was removed within 10 min of reaction time. These results indicate that the EF process can be considered as an alternative method for textile wastewater treatment.&amp;nbsp;&lt;/p&gt; &lt;/div&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

On-field measurement method of vapor injection heat pump system

This paper examines air-to-air injection heat pumps (HPs) and proposes a method to determine both heating capacity and coefficient of performance (COP) in situ, allowing analyses of already-installed setups and long-term observation. Due to the uncertain nature of air enthalpy measurements, this method instead uses refrigerant enthalpies calculated from pipe contact temperatures and steady-state energy balances to determine the COP. However, these energy balances are highly dependent on the hypothesis that the working fluid remains strictly monophasic in certain locations, which is not always true in practice. A parametric variable analysis is conducted on the refrigerant vapor quality to calculate the deviation in the COP due to diphasic conditions at the compressor inlet, injection port, and condenser and flash tank outlets. A final in situ COP uncertainty is presented, due to both the measurement and vapor quality uncertainties.

Characteristics of biofilm development in an operating rainwater storage tank

For better understanding of the environmental conditions in rainwater tanks and the development of biofilms therein, the physicochemical and microbial conditions were investigated and compared along with the changes in biofilm cells and the bacterial community during biofilm development in the inlet and outlet of a rainwater tank. Differences were observed in some of the physicochemical and microbial parameters between the inlet and the outlet, and the bacterial composition differed at each stage of biofilm development with the bacterial community structure exhibiting greater evenness as the biofilm matured. It was confirmed that the biofilm development process takes place in four stages: an initial stage characterized by the colonization of different populations, an intermediate stage characterized by a limited number of dominant populations, a late/mature stage characterized by mature biofilms of a complex spatial structure, and a detachment stage. It was concluded that the nutrient and microbial parameters differed by location within the rainwater tank because of its baffle and inlet barrier design, which also appeared to have an influence on the bacterial composition and biofilm development rate.