Optimal Water Flow Research Articles

Fitting rectangles under vulnerability curves: Optimal water flow through plants

We study an optimization problem for a model of steady‐state water transport through plants that maximizes water flow subject to the constraints on hydraulic conductance due to vulnerability to embolism (air blockage of conduits). The model has an elementary geometric interpretation and exhibits bottleneck behavior where one of the plant segments limits the overall optimal flow, sometimes in a counterintuitive way. The results show good agreement with experimental measurements and provide support for the hypothesis that leaves serve as a safety buffer protecting stems against excessive embolism.

Energy-Optimal Pump Scheduling and Water Flow

This paper focuses on the optimal operation of water supply networks. We model water supply networks using hydraulic constraints, and formulate a joint optimal pump scheduling and water flow problem (OWF) using the hydraulic characteristics of variable speed pumps. OWF is a mixed-integer nonlinear program . This problem is nonconvex, and hence NP-hard. To compute an exact solution of OWF, we first focus on the feasibility region of OWF, and propose a mixed-integer second-order cone relaxation for the feasibility region of OWF. We prove that the proposed relaxation is exact for several relevant network topologies. We then focus on the objective function in OWF, and show that for some energy metrics, OWF can be transformed into a mixed-integer second-order cone program . Furthermore, we propose an ADMM-based algorithm to compute suboptimal solutions to OWF and lower bounds on the optimal value of the objective in OWF when the objective function is nonconvex. Finally, we consider a real-world water network, and demonstrate the effectiveness of the proposed relaxation in computing the optimal pump schedules and water flows.

A performance of a heat pump system connected a new conic helicoidal geothermal heat exchanger for a greenhouse heating in the north of Tunisia

The aim of this experimental study is made to examine the performance of a new conic helicoidal geothermal heat exchanger (CHGHE) for greenhouse heating. The main advantage of this geometry of heat exchangers type is to reduce the used area and the operating cost compared to horizontal and vertical, respectively. An experimental study is composed of CHGHE implanted in 3 m depth connected to a geothermal heat pump which is connected to a ceiling panel installed into a greenhouse. This ceiling unit is constituted of an exchangers suspended in internal air and others placed on the ground. This conditioning system allowed a recover the energy in excess into the greenhouse during the day by the exchangers placed on the ground, or, this energy stored is brought back to heat the air in the greenhouse by the suspended exchangers during the night. The experimental results showed that the recovered heat rate from the ground by the CHGHE is about 4.7 kW. However, they are between 12 kW and 10 kW in into greenhouse. The coefficient of the performance of the heat pump (COPhp) and the overall system (COPsys) were found to be 3.93 and 2.64 respectively. The geothermal system insure a quantity of heat equal to 692.208 kW witch correspond to a temperature increasing of 3 °C under greenhouse for an optimal water flow rate of 0.6 kg/s.

FLUE GAS DEDUSTING IN VENTURI SCRUBBERS AT THERMAL POWER PLANTS

In this paper, an improved engineering model and analysis techniques are presented of the fly ash particles coagulation with droplets in Venturi tubes of industrial scale, based on spatial variation of the collection efficiency of particles on individual droplets, accounting for spray water flow polydispersity and particle size distribution, which allows to define optimal droplets size and spray water flow rate at different modes of thermal power units operation. The model is validated with the published experimental data on the wet Venturi scrubbers operations at the thermal power plants (TPP) in Ukraine, Russia and Kazakhstan. The results of calculations demonstrate good coincidence with experimental data. The influence of the boiler load and spray water consumption on an efficiency of the TPP Venturi wet scrubbers was studied. The simulation results have shown that moderate increment of spray water consumption up to 0.24 L/m3 allows increasing of the Venturi wet scrubber s efficiency without threat of reaching the dew point in flue gas flow, thus preventing potential corrosion of the power plant equipment downstream. The calculations confirmed that without retrofit of wet scrubbers installed at Ukrainian power plants it will not be possible by these stations to meet European requirements on the allowable levels of emissions from the coal firing power plants.

Solar water heating systems for different buildings under a hot climate; parametric optimization and economic analysis

Building applied solar thermal systems are considered by different stakeholders an attractive alternative to traditional space and water heating systems. However, their performance depends largely on climatic conditions, water heating needs and operational parameters which, in turn, offer opportunities for performance optimization. The present research attempts to provide architects with a design decision tool that integrates solar thermal collectors efficiently to meet hot water demand for various building types inclusive of residential, commercial and industrial in a hot climate. The analysis is conducted numerically through a thermal model developed and executed in TRNSYS and validated experimentally. The parameters investigated include the collector tilt angle, azimuth angle and collector inlet fluid flow rate. Finally, the collector aperture area required per building foot print area is determined. The research revealed that for a 1000 m2 footprint building area of schools, offices, residential, factories and hospitals would require respectively 8 m2, 10 m2, 14 m2, 24 m2 and 38 m2 of the static collector installed at 24° tilt angle with optimal water flow rate. Additional operational aspects of collector tracking, and solar radiation concentration were investigated and further reduce the required collector area. A simple payback period analysis reveals a return on investment of 2 years applying subsidized tariff rates under the climatic conditions of, or similar to Dubai, in the United Arab Emirates.

Experimental Study to Estimate the Required Flow of Fire Extinguishing System for Flame Spread Prevention on Composite Panel

복합패널은 다른 종류의 재료를 샌드위치 모양으로 쌓아 올려 접착제로 접합한 특수 합판으로서, 시공성 및 경제 성이 좋기 때문에 건축물 재료로 많이 사용되고 있다. 그러나 표면판은 철판 재질로 되어 있기 때문에 화재 시 일반 적인 소화설비를 이용한 소화방법이 외부의 철판에 막혀 심재 부분의 화원에 도달하지 못하여 소화를 하는데 어려 움이 있으며, 화재 시 붕괴에 따른 소화활동에도 어려움이 많다. 본 연구에서는 이와 같은 문제를 해결하기 위하여 복합패널의 심재에 소화배관을 설치하여 화재 시 화재확산을 방지할 수 있는 소화설비시스템에 대하여 연구하였다. 소화시스템의 소화용수의 소요유량을 산정할 수 있도록 수공급 시험 장치를 제작하여 최소량의 소화수를 사용하여 화재확산을 방지할 수 있게 하였다. 또한 실물화재 실험을 통하여 최적의 공급유량(0.5 L/min)을 설정하였다.Composite panel refers to the particular plywood produced in a way of stacking the different kinds of material in sandwich form and adhering them using adhesives and is widely used as building material for its constructability and cost efficiency. But as the surface is finished with steel plate, fire extinguishing agent cannot reach to the core material because of such steel plate on surface which causes the difficulties in suppressing the fire as well as in fire-fighting activities due to collapse. This study, to deal with such problem, is intended to set the fire pipe in core material to prevent the fire from spreading and in a bid to achieve this using minimized fire water, water supply test device was fabricated to estimate the required water flow of fire extinguisher and consequently, optimal water flow (0.5 L/min) was determined through a full-scale fire test.

Granulomatous enteritis in rainbow trout (Oncorhynchus mykiss) associated with soya bean meal regardless of water dissolved oxygen level

This study investigated morphological changes associated with soya bean meal-induced enteritis (SBMIE) in distal intestine (DI) of rainbow trout (Oncorhynchus mykiss) fed a soya bean meal (SBM)-based diet and exposed to normoxia or hypoxia created by optimal and low water flow rates, respectively. A 28-day adaption period was followed by a 42-day challenge period where 600 fish were subjected to dietary challenge and/or hypoxia. Twelve tanks each containing 50 juvenile trout were assigned randomly in triplicate to each treatment. Histopathological and immunohistochemical evaluation revealed pathological features that have not previously been described in association with SBMIE. Vacuolar degeneration of epithelial cells mainly at the base of mucosal folds, epithelial cysts, epithelial dysplasia, necrosis, shedding of necrotic cells, and granulomatous inflammation including infiltration of enlarged, sometimes finely vacuolated or "foamy" macrophages, multinucleated giant cells and increased proliferation of fibroblasts were observed. Acid-fast bacteria were not detected in enlarged macrophages; however, these cells contained AB-PAS- and sometimes cytokeratin-positive material, which was interpreted to be of epithelial/goblet cell origin. Hypoxia did not affect the morphological changes in DI. These results suggest that SBM was associated with a granulomatous form of enteritis in DI of rainbow trout regardless of water oxygen level.

Evaluation of optimal water flow and temperature in response to outdoor air temperature in plastic greenhouse with recirculated water curtain system

This study evaluated the optimal supply water temperature and flow rate in response to the outdoor air temperature in order to maintain a target indoor air temperature and minimize the amount of energy required to reheat a recirculated water curtain in a plastic greenhouse. This paper proposed a multiple regression model that estimated the indoor air temperature using the outdoor air and the inlet water temperatures, as well as the water flow rate, as independent variables. We also established a multiple regression model that estimated the average amount of energy required to reheat the recirculated water curtain. To this end, the study analyzed and quantified a reasonable inlet water temperature and water flow rate in response to the outside air temperature using isothermal and iso-energy curves. The results indicated that maintaining a higher water flow rate was preferable to maintaining a higher inlet water temperature for cultivation purposes.

A new model of respiration in blastoid (Echinodermata) hydrospires based on computational fluid dynamic simulations of virtual 3D models

AbstractHydrospires are internal structures in blastoids that primarily served a respiratory function. Historically, hydrospires have been modeled as passive-flow respiratory structures with a vertical orientation. This project constructed virtual 3D models of blastoids from legacy acetate peel collections at the Naturalis Museum in the Netherlands. Computational fluid dynamic (CFD) simulations of the blastoid models reconstructed in living position indicated that hydrospires likely were oriented horizontally when the blastoid was in feeding mode in current velocities>0.5 cm/s to 10 cm/s. In this range of current velocities, passive water flow through the hydrospires did not produce conditions optimized for efficient gas exchange. However, optimal water flow through the hydrospires could be achieved if the excurrent velocity of water exiting the hydrospire through the spiracle was approximately one-half the velocity of ambient environmental currents. Maintaining such a ratio in the dynamic current systems in which blastoids lived suggests that cilia-driven active water flow through the hydrospires is a better model for optimizing respiratory effectiveness.

Thermal Performances of Two Stage Molten Salt Steam Generator

Abstract Thermal performances of two stage molten salt steam generator were experimentally investigated in this article. The two stage system consisted of primary U shape heat exchanger and secondary shell and tube heat exchanger, and its overall heat transfer coefficient, steam generation rate and thermal efficiency were further analyzed under different molten salt flow rates and water flow rates. According to the experimental results, the overall heat transfer coefficients of the primary and secondary heat exchanger both increase as the molten salt flow rising. As the water flow rate increases, the overall heat transfer coefficient of the primary heat exchanger first increases and then decreases, while that of the secondary heat exchanger gradually increases. As the molten salt flow rate and water flow rate increase, the steam generation rate and the thermal efficiency of the secondary heat exchanger both increase, while the thermal efficiencies of the primary heat exchanger and the whole system first increase, approaching their maximums with optimal molten salt flow rate and water flow rate respectively, and then begin to drop.

Sequential synthesis of heat integrated water networks: A new approach and its application to small and medium sized examples

This paper presents a new step-wise sequential solution strategy for the synthesis of heat integrated water networks (HIWNs) comprising of two mathematical models. The first model minimizes water and energy costs. The optimal freshwater and water flow rates within the HIWN are determined from this model. Using these optimal flow rates, different configurations of HIWN are evaluated for the purpose of heat integration. The second model is the stage-wise heat exchanger network (Yee and Grossmann, 1990), which is solved for each of the evaluated network configuration in a sequential manner. Using this proposed strategy, a set of locally optimal HIWNs are produced and the best one is chosen based on the minimum total annual cost (TAC). The proposed sequential strategy is applied to small and medium sized examples in the literature. The results show that the proposed new sequential solution strategy can be successfully applied to small and medium sized HIWN problems.

Modeling and Simulation Assessment of Solar Photovoltaic/Thermal Hybrid Liquid System Using TRNSYS

The PV/T hybrid system is a combined system consisting of PV panel behind which heat exchanger with fins are embedded. The PV/T system consists of PV panels with a battery bank, inverter etc., and the thermal system consists of a hot water storage tank, pump and differential thermostats. In the present work, the modeling and simulation of a Solar Photovoltaic/Thermal (PV/T) hybrid system is carried out for 5 kWp using TRNSYS for electrical energy and thermal energy for domestic hot water applications. The prominent parameters used for determining the electrical efficiency, thermal efficiency, overall thermal efficiency, electrical thermal efficiency and exergy efficiency are the solar radiation, voltage, current, ambient temperature, mass flow rate of water, area of the PV module etc. The simulated results of the Solar PV/T hybrid system are analyzed for the optimum water flow rate of 25 kg/hr. The electrical efficiency, thermal efficiency, overall thermal efficiency, equivalent thermal efficiency, exergy efficiency are found to be 10%, 34%, 60%, 35% and 13% respectively. The average tank temperature is found to be 50°C.

Effect of water flow rate on polyculture of koi carp (Cyprinus carpio var. koi) and goldfish (Carassius auratus) with water spinach (Ipomoea aquatica) in recirculating aquaponic system

A 45-day experiment was conducted for standardization of water flow rate for koi carp (Cyprinus carpio var. koi) and gold fish (Carassius auratus) along with water spinach (Ipomoea aquatica) in water recirculating aquaponic system. Different flow rates, viz., 0.8, 2.4, and 4 l min−1, were assigned as T1, T2, and T3, respectively, with stocking density ratio of 1:2 for koi carp and goldfish. Treatment T1 showed maximum fish growth in terms of percentage weight gain and specific growth rate. Plant height, percentage height gain, and yield of water spinach plants were observed highest in treatment T1 as compared to T2 and T3. All the treatments effectively removed nutrients, but treatment T1 showed maximum percentage of nutrient removal (NO3-N, PO4-P, and K). The plant growth and nutrient removal were increased with decrease in flow rate. Flow rate in T1 (0.8 l min−1) showed the highest growth in both fish species. Thus, 0.8 l min−1 can be suggested as optimum water flow rate for the polyculture of koi carp and goldfish with water spinach in an aquaponic system.

Estimation of Seaweed Twist Based on Diffusion Kernels in Physical Simulation

In the optimization of seaweed cultivation now being extensively researched, a problem arises in avoiding twisting seaweed. Twisting is a complex phenomenon and difficult to formulate. Producing the optimal water flow, requires calculating the risk of twisting occurring. In this paper, we propose a method to calculate and estimate the twist state based on the results of physical simulation. We devise a seaweed model using multiple rigid bodies that mutually and physically interfere. One result of physical interference, is that the model has two internal state variables – contact time and the number of contact points between individual pieces of seaweed. We introduce an evaluation function to quantify twisting using these state variables in each time step, and propose a way to calculate twist risk based on the von Neumann and Laplacian diffusion kernels, in a dynamic network.

Effect of water flow rates on growth of Cyprinus carpio var. koi (Cyprinus carpio L., 1758) and spinach plant in aquaponic system

The experiment was aimed at standardization of water flow rate in aquaponic system in order to correlate nutrient removal and water quality with growth of Cyprinus carpio var. koi (koi carp fingerlings) and Beta vulgaris var. bengalensis (spinach). Different flow rates, i.e., 3.2, 1.5, and 1.0 l min−1, were assigned as treatments T1, T2, and T3, respectively, with spinach plants (28 plant m−2), whereas S1 and S2 were the treatments having flow rates of 1.5 and 1.0 l min−1, respectively, without plants. Control (C) was set at flow rates of 3.2 l min−1 without plants. Treatment T2 (1.5 l min−1) showed highest weight gain of koi carp fingerlings and also height gain of spinach plants as compared to other treatments. There was no significant difference in length gain, percentage weight gain, specific growth rate, feed conversion ratio, feed efficiency ratio, and protein efficiency ratio as compared to other treatments and control. All the treatments, T1, T2, and T3, effectively remove nitrate (77–78 %), phosphate (47.04–55.06 %), and potassium (22.85–29.16 %) from fish effluent tanks. These results suggest that flow rates 3.2, 1.5, and 1.0 l min−1 were effective under aquaponic system. Of which, 1.5 l min−1 can be suggested as optimum water flow rate for the growth of spinach and koi carp in aquaponic system as percentage weight gain in fish, percentage height gain, and yield of plants were higher compared to flow rates 3.2 and 1.0 l min−1.

Modelling and optimal operation of a small-scale integrated energy based district heating and cooling system

This paper presents a comprehensive model of a small-scale integrated energy based district heating and cooling (DHC) system located in a residential area of hot-summer and cold-winter zone, which makes joint use of wind energy, solar energy, natural gas and electric energy. The model includes an off-grid wind turbine generator, heat producers, chillers, a water supply network and terminal loads. This research also investigates an optimal operating strategy based on Group Search Optimizer (GSO), through which the daily running cost of the system is optimized in both the heating and cooling modes. The strategy can be used to find the optimal number of operating chillers, optimal outlet water temperature set points of boilers and optimal water flow set points of pumps, taking into account cost functions and various operating constraints. In order to verify the model and the optimal operating strategy, performance tests have been undertaken using MATLAB. The simulation results prove the validity of the model and show that the strategy is able to minimize the system operation cost. The proposed system is evaluated in comparison with a conventional separation production (SP) system. The feasibility of investment for the DHC system is also discussed. The comparative results demonstrate the investment feasibility, the significant energy saving and the cost reduction, achieved in daily operation in an environment, where there are varying heating loads, cooling loads, wind speeds, solar radiations and electricity prices.

Estimation of Optimal Water Flow Rate of a Steel Roller Shutter with Water Film Cooling System

The hybrid inverse method to estimate the optimal water flow rate and surface temperature on the hot surface of the steel roller shutter with water film cooling system subjected to a fire environment is presented in this paper. The results show that the effect of the down-flowing water film flow rate on the present estimates cannot be negligible. The water-film system combined with the steel roller shutter can effectively improve the heat resistance and the temperature of the shutter slat surface can be controlled to around 100 °C. The optimal water flow rate is 110 L/min for a typical 3m x 3m steel roller shutter with water film cooling system.

Thermal and Hydraulic Design of a Solar Collector Field for a Primary School Pool

The methodology and results of the thermal and hydraulic design for a solar heating field of an elementary school's semi-olympic pool is presented. Improved flat solar collectors with copper tube and aluminum fins were used.From own experiences, many Mexican solar fields do not operate correctly because of their poor flow balance (irrigation), may be due to lack of attention given to this aspect. That's why the research of this work focuses on studying the behavior of the pressure drop in a hydraulic arrangement, particularly of this facility, in which all collector batteries are connected in parallel.Previously two solar collectors were sent to a specialized laboratory for certification tests, obtaining the optimum water flow value for maximum thermal efficiency. The results show an optimum range between 4 and 11 L/min.On the other hand, the development of a thermal model based on a temporal energy balance, allowed us to determine that the optimum solar heating area is around 338 m2, using 195 flat-coated solar collectors, with copper tube and aluminum fin.For this heating system a water volume/solar collection area relation, called REVA, of 1.45m3/m2 was obtained. Referred to the hydraulic design and using the program EPANET 2.0 it was found that in the proposed arrangement, 192 solar collectors were irrigated with the optimal range and only 2 solar collectors were below the lower range at 3 L/min.

Improving the Efficiency of Dehydrogenation Catalyst Resource while Reducing the H2 Gas Circulation Rate

In the research the various ways of increasing the selectivity of the dehydrogenation process and reducing the intensity of coke formation have been studied. All results were received by means of the mathematical model of the dehydrogenation process with the calculating technique of optimal water flow. The main conclusion consists in the fact that the decrease in molar ratio H2/feed leads to increasing the catalyst deactivation by coke. It can be partially compensated by increasing the supplied water flow to the reactor to 13-14 l/h instead of 9-10 l/h at the end of cycle. Reducing the life of the catalyst to 270-290 days even at an increased water flow is determined by the intensity of the coking reactions. However, the economic feasibility of operating in such condition causes a considerable increase in production of LAB to 181-186 t/day.

Modelling and operation optimization of an integrated energy based direct district water-heating system

This paper proposes a model of an integrated energy based direct district water-heating system, which makes joint use of wind energy, solar energy, natural gas and electric energy. The model includes a stand-alone wind turbine generator, heat producers, a water supply network and heating load. This research also investigates an optimal operating strategy in which the fossil fuel consumption of the system in daily operation is optimized. Based on the model, an objective function used to obtain the optimal control strategy is constructed with complex operating constraints. GSO (Group Search Optimizer) is used to trace the optimal set-point temperature of boilers and the optimal water flow of pumps to minimize fuels consumption while satisfying variable constraints. In order to verify the model and optimal operating strategy, simulation studies have been undertaken. The optimal operating strategy is evaluated in comparison with an unoptimized control strategy. The simulation results prove the validity of the model and show that the optimal operating strategy is able to make the system operation more energy efficient. The proposed system is also evaluated in comparison with a conventional natural gas heating system. The comparative results demonstrate the investment feasibility, the significant energy saving and cost reduction achieved in daily operation.