Optimization of circulating cooling water systems based on chance constrained programming

Recent research on deterministic methods for circulating cooling water systems optimization has been well developed. However, the actual operating conditions of the system are mostly variable, so the system obtained under deterministic conditions may not be stable and economical. This paper studies the optimization of circulating cooling water systems under uncertain circumstance. To improve the reliability of the system and reduce the water and energy consumption, the influence of different uncertain parameters is taken into consideration. The chance constrained programming method is used to build a model under uncertain conditions, where the confidence level indicates the degree of constraint violation. Probability distribution functions are used to describe the form of uncertain parameters. The objective is to minimize the total cost and obtain the optimal cooling network configuration simultaneously.An algorithm based on Monte Carlo method is proposed, and GAMS software is used to solve the mixed integer nonlinear programming model. A case is optimized to verify the validity of the model. Compared with the deterministic optimization method, the results show that when considering the different types of uncertain parameters, a system with better economy and reliability can be obtained(total cost can be reduced at least 2%).

Effects of Nutrients on Biofouling Formation and Preponderant Bacteria Diversity in Recirculating Cooling Water System

A series of orthogonal array experiments were conducted using carbon source, ammonia nitrogen and total phosphorus （TP） as major influencing factors to investigate the effects of nutrients on biofouling formation and preponderant bacteria diversity in the recirculatiug cooling water system. Carbon source was demonstrated to be the most significant determinant affecting the biofouling formation. A minimum biofouling outcome was obtained when BOD2, NHa＋-N and TP were 25, 10, and 1 mg/L, respectively. Then the preponderant bacteria strains in biofouling mass under two typical culture conditions （negative and favorable） were identified applying both traditional biochemical methods and further molecular biology technology with phylogenetic affiliation analysis, which indicated that Enterobacteriaceae Enterobacter, Micrococcaceae Staphylococcus, Bacillaceae Bacillus, Enterobacteriaceae Proteus, Neisseriaceae Neisseria and Pseudomonadaceae Pseudomonas were dominant under negative condition, while Enterobacteriaceae Klebsiella, Enterobacteriaceae Enterobacter and Microbacterium - under favorable one.

Laccase Immobilized on Mesoporous Silica Materials and Its Corrosion Inhibition Performance in Circulating Cooling Water System

Mesoporous SiO_2 microspheres were synthesized using the sol-gel method and were characterized by TEM, FT-IR and BET techniques. The diameter of the microspheres is about 100—150 nm, and the average mesopore diameter is 2.55 nm, while the specific surface area is 1 088.9 m2/g. Mesoporous SiO_2 microspheres adsorb glutaraldehyde and immobilize laccase by means of the aldehyde group in glutaral which can react with the amidogen of laccase. The immobilization conditions were optimized at a glutaraldehyde concentration of 0.75%, a crosslinking time of 8 h, a laccase concentration of 0.04 L/L and an immobilization time of 10 h. When diesel leakage concentration was 80 mg/L, the highest corrosion inhibition efficiency of immobilized laccase reached 49.23%, which was slightly lower than the corrosion inhibition efficiency of free laccase(59%). The diesel degradation ratio could reach up to 45%. It has been proved that the immobilized laccase could degrade diesel to inhibit corrosion.

Model free optimization of building cooling water systems with refined action space

Deep Q Network(DQN)is an efficient model-free optimization method,and has the potential to be used in building cooling water systems.However,due to the high dimension of actions,this method requires a complex neural network.Therefore,both the required number of training samples and the length of convergence period are barriers for real application.Furthermore,penalty function based exploration may lead to unsafe actions,causing the application of this optimization method even more difficult.To solve these problems,an approach to limit the action space within a safe area is proposed in this paper.First of all,the action space for cooling towers and pumps are separated into two sub-regions.Secondly,for each type of equipment,the action space is further divided into safe and unsafe regions.As a result,the convergence speed is significantly improved.Compared with the traditional DQN method in a simulation environment validated by real data,the proposed method is able to save the convergence time by 1 episode(one cooling season).The results in this paper suggest that,the proposed DQN method can achieve a much quicker learning speed without any undesired consequences,and therefore is more suitable to be used in projects without pre-learning stage.

Calculation of Mass Concrete Temperature Containing Cooling Water Pipe Based on Substructure and Iteration Algorithm

Mathematical physics equations are often utilized to describe physical phenomena in various fields of science and engineering.One such equation is the Fourier equation,which is a commonly used and effective method for evaluating the effectiveness of temperature control measures for mass concrete.One important measure for temperature control in mass concrete is the use of cooling water pipes.However,the mismatch of grids between large-scale concrete models and small-scale cooling pipe models can result in a significant waste of calculation time when using the finite element method.Moreover,the temperature of the water in the cooling pipe needs to be iteratively calculated during the thermal transfer process.The substructure method can effectively solve this problem,and it has been validated by scholars.The Abaqus/Python secondary development technology provides engineers with enough flexibility to combine the substructure method with an iteration algorithm,which enables the creation of a parametric modeling calculation for cooling water pipes.This paper proposes such a method,which involves iterating the water pipe boundary and establishing the water pipe unit substructure to numerically simulate the concrete temperature field that contains a cooling water pipe.To verify the feasibility and accuracy of the proposed method,two classic numerical examples were analyzed.The results showed that this method has good applicability in cooling pipe calculations.When the value of the iteration parameterαis 0.4,the boundary temperature of the cooling water pipes can meet the accuracy requirements after 4∼5 iterations,effectively improving the computational efficiency.Overall,this approach provides a useful tool for engineers to analyze the temperature control measures accurately and efficiently for mass concrete,such as cooling water pipes,using Abaqus/Python secondary development.

Hydroxyl carboxylate based non-phosphorus corrosion inhibition process for reclaimed water pipeline and downstream recirculating cooling water system

A combined process was developed to inhibit the corrosion both in the pipeline of reclaimed water supplies（PRWS） and in downstream recirculating cooling water systems（RCWS）using the reclaimed water as makeup. Hydroxyl carboxylate-based corrosion inhibitors（e.g.,gluconate, citrate, tartrate） and zinc sulfate heptahydrate, which provided Zn^2＋ as a synergistic corrosion inhibition additive, were added prior to the PRWS when the phosphate（which could be utilized as a corrosion inhibitor） content in the reclaimed water was below 1.7 mg/L, and no additional corrosion inhibitors were required for the downstream RCWS.Satisfactory corrosion inhibition was achieved even if the RCWS was operated under the condition of high numbers of concentration cycles. The corrosion inhibition requirement was also met by the appropriate combination of PO4^3- and Zn^2＋ when the phosphate content in the reclaimed water was more than 1.7 mg/L. The process integrated not only water reclamation and reuse, and the operation of a highly concentrated RCWS, but also the comprehensive utilization of phosphate in reclaimed water and the application of non-phosphorus corrosion inhibitors. The proposed process reduced the operating cost of the PRWS and the RCWS, and lowered the environmental hazard caused by the excessive discharge of phosphate. Furthermore, larger amounts of water resources could be conserved as a result.

Preparation and application of a phosphorous free and non- nitrogen scale inhibitor in industrial cooling water systems

A novel environmentally friendly type of calcium carbonate, zinc （Ⅱ） and iron （Ⅲ） scale inhibitor Acrylic acidallylpolyethoxy carboxylate copolymer （AA- APEL） was synthesized. The anti-scale property of the AA-APEL toward CaCO3, zinc （Ⅱ） and iron （Ⅲ） in the artificial cooling water was studied through static scale inhibition tests. The observation shows that both calcium carbonate, zinc （Ⅱ） and iron （Ⅲ） inhibition increase with increasing the dosage of AA-APEL. The effect on formation of CaCO3 was investigated with combination of scanning electronic microscopy （SEM）, transmission electron microscopy （TEM）, X-ray powder diffraction （XRD） analysis and fourier transform infrared spectrometer, respectively. The results showed that the AA-APEL copolymer not only influenced calcium carbonate crystal morphology and crystal size but also the crystallinity. The crystallization of CaCO3 in the absence of inhibitor was rhombohedral calcite crystal, whereas a mixture of calcite with vaterite crystals was found in the presence of the AA- APEL copolymer. Inhibition mechanism is proposed that the interactions between calcium or iron ions and polyethylene glycol （PEG） are the fundamental impetus to restrain the formation of the scale in cooling water systems.

Multiperiod optimization of cooling water system with flexible topology network

Cooling water systems(CWSs)are extensively utilized in various industries to eliminate the excess heat and converse energy.Studies on CWSs mainly concentrated on finding the optimal cooler network structure.In addition,some works also considered the optimal design under varied operation conditions.However,in these works,once the optimal design of the cooler's network is determined,its arrangement remains fixed and cannot be adapted to accommodate diverse operating conditions.In this work,a flexible topology network concept is proposed to make the adjustment of network structure possible under different operation conditions.The CWS with integrated air cooler and flexible topology network has better overall performance,represented by a mixed integer nonlinear programming(MINLP)model that require advanced tools such as GAMS software.Case studies revealed that the proposed methodology can realize better energy-saving performance,and improve the economic performance under varied operation conditions.The impact of critical flexible nodes on system configuration and economy is achieved by sensitivity analysis.

Effect of temperature, chloride ions and sulfide ions on the electrochemical properties of 316L stainless steel in simulated cooling water

The influence of temperature, chloride ions and sulfide ions on the anticorrosion behavior of 316L stainless steel in simulated cooling water was studied by electrochemical impedance spectroscopy and anodic polarization curves. The results show that the film resistance increases with the solution temperature but decreases after 8 days’ immersion, which indicates that the film formed at higher temperature has inferior anticorrosion behavior; Chloride ions and sulfide ions have remarkable effects on the electrochemical property of 316L stainless steel in simulated cooling water and the pitting potential declines with the concentration of chloride ions; the passivation current has no obvious effect; the rise of the concentration of sulfide ions obviously increases the passivation current, but the pitting potential changes little, which indicates that the two types of ions may have different effects on destructing passive film of stainless steel. The critical concentration of chloride ions causing anodic potential curve’s change in simulated cooling water is 250 mg/L for 316 L stainless. The effect of sulfide ions on the corrosion resistance behavior of stainless steel is increasing the passivation current density Ip. The addition of 6 mg/L sulfide ions to the solution makes Ip of 316 L increase by 0.5 times.

Application of a water cooling treatment and its effect on coal-based reduction of high-chromium vanadium and titanium iron ore

A water cooling treatment was applied in the coal-based reduction of high-chromium vanadium and titanium （V-Ti-Cr） iron ore from the Hongge region of Panzhihua, China. Its effects on the metallization ratio （η）, S removal ratio （Rs）, and P removal ratio （Rp） were studied and analyzed on the basis of chemical composition determined via inductively coupled plasma optical emission spectroscopy. The metallic iron particle size and the element distribution of Fe, V, Cr, and Ti in a reduced briquette after water cooling treatment at 1350℃ were determined and observed via scanning electron microscopy. The results show that the water cooling treatment improved the η, Rs, and Rp in the coal-based reduction of V-Ti-Cr iron ore compared to those obtained with a furnace cooling treatment. Meanwhile, the particle size of metallic iron obtained via the water cooling treatment was smaller than that of metallic iron obtained via the furnace cooling treatment; however, the particle size reached 70 μm at 1350℃, which is substantially larger than the minimum particle size required （20 μm） for magnetic separation. Therefore, the water cooling treatment described in this work is a good method for improving the quality of metallic iron in coal-based reduction and it could be applied in the coal-based reduction of V-Ti-Cr iron ore followed by magnetic separation.

Application of Cooling Water in Controlled Runout Table Cooling on Hot Strip Mill

The controlled runout table cooling is essential in determining the final mechanical properties and flatness of steel strip.The heat of a hot steel strip is mainly extracted by cooling water during runout.In order to study the heat transfer by water jet impingement boiling during runout,apilot facility was constructed at the University of British Columbia.On this pilot facility,the water jet impingement tests were carried out under various cooling conditions to investigate the effect of processing parameters,such as cooling water temperature,water jet impingement velocity,initial strip temperature,water flow rate,water nozzle diameter and array of water nozzles,on the heat transfer of heated strip.The results obtained contribute to the optimization of cooling water during runout.

CFD Analysis and Optimization of a Diesel Engine Cooling Water Jacket

The STAR-CCM+software is used to investigate the flow inside a cooling water jacket of an in-line six-cylinder diesel engine.The results show that the average flow velocity of the cooling water inside the jacket is 1.669 m/s while the flow velocity distribution is not uniform for each cylinder.Moreover,the fluid velocity in proximity to the cylinder head is too low,thereby affecting the cooling performances of the water jacket.Two corresponding structural optimization schemes are proposed to mitigate this issue and the post-optimization performances of the water jacket are discussed in detail.

Cooling System Design and Thermal Analysis of Modular Stator Hybrid Excitation Synchronous Motor

Hybrid excitation synchronous motor has the advantages of uniform and adjustable electromagnetic field, wide speed range and high power density. It has broad application prospects in new energy electric vehicles, wind power generation and other fields. This paper introduces the basic structure of hybrid excitation motor with modular stator, and analyzes the operation principle of hybrid excitation motor. The cooling structure of the water-cooled plate is designed, and the effects of the thickness of the water-cooled plate and the number of water channels in the water-cooled plate on the heat dissipation capacity of the water-cooled plate are analyzed by theoretical and computational fluid dynamics methods. The effects of different water cooling plate structures on water velocity, pressure drop, water pump power consumption and heat dissipation capacity were compared and analyzed. The influence of different inlet flow velocity on the maximum temperature rise of each part of the motor is analyzed, and the temperature of each part of the motor under the optimal water flow is analyzed. The influence of the traditional spiral water jacket cooling structure and the water-cooled plate cooling structure on the maximum temperature rise of the motor components is compared and analyzed. The results show that the water-cooled plate cooling structure is more suitable for the modular stator motor studied in this paper. Based on the water-cooled plate cooling structure, the air-water composite cooling structure is designed, and the effects of the air-water composite cooling structure and the water-cooled plate cooling structure on the maximum temperature rise of each component of the motor are compared and analyzed. The results show that the maximum temperature rise of each component of the motor is reduced under the air-water composite cooling structure.

Influence of CO_(2) inleakage on the slight-alkalization of generator internal cooling water

The slight-alkalization of generator internal cooling water(GICW)is widely used to inhibit the corrosion of hollow copper conductor and thereby ensure the safe operation of the generator.CO_(2) inleakage is increasingly identified as a potential security risk for GICW system.In this paper,the influence of CO_(2) inleakage on the slight-alkalization of GICW was theoretically discussed.Based on the equilibriums of the CO_(2)-NaOH-H_(2)O system,CO_(2) inleakage saturation was derived to quantify the amount of the dissolved CO_(2) in GICW.This parameter can be directly calculated with the measured conductivity and the[Na+]of GICW.The influence of CO_(2) inleakage on the slight-alkalization conditioning of GICW and the measurement of its water quality parameters were then analyzed.The more severe the inleakage,the narrower the water quality operation ranges of GICW,resulting in the more difficult the slight-alkalization conditioning of GICW.The temperature calibrations of the conductivity and the pH value of GICW show nonlinear correlations with the amount of CO_(2) inleakage and the NaOH dosage.This study provides insights into the influence of CO_(2) inleakage on the slight-alkalization of GICW,which can serve as the theoretical basis for the actual slight-alkalization when CO_(2) inleakage occurs.

Cooling Water Flow Rate Calculation for Hearth of Large Blast Furnaces

The cooling water flow rate for hearth of large blast furnaces was calculated by simulation. The results show that the cooling water flow rate shall be above 4 200m3/ h for hearth of large blast furnaces; to meet requirements of the increasing smelting intensity and to ensure the safety at the end of the first campaign,the designed maximum cooling water flow rate should be 5 900m3/ h; according to the flow distribution stability and the calculated resistance loss,hearth cooling stave pipes with the specification of 76 mm × 6 mm shall be adopted to assure the flow velocity in pipes of hearth cooling stave in the range of 1. 9- 2. 3 m / s.

Effects of air-atomized water spray cooling device structure on the quenching process,microstructure,and properties of wear-resistant steel

With its high strength and hardness, wear-resistant steel has become an important material in the field of construction machinery manufacturing.Given that quenching technology is a crucial component of wear-resistant steel production, the selection of the cooling method to be used during this process is important.In this study, the feasibility of quenching wear-resistant steel by air-atomized water spray cooling was studied, and the cooling rate, microstructure, and hardness of wear-resistant steel under various cooling device structures were analyzed.The results reveal that the air-atomized water spray cooling method is an effective technique in quenching wear-resistant steel.Furthermore, martensite and uniform hardness were obtained by the air-atomized water spray cooling technique.As the space between the nozzles in each row in the device increased, the cooling rate was reduced during quenching.Meanwhile, the martensite content decreased, and more carbides were observed in the martensitic structure.A mixture comprising self-tempered martensite and bainite was formed at a large distance over a longer period of time.All these factors resulted in lower hardness and worse property uniformity.

Strength-ductility balance of AZ31 magnesium alloy via accumulated extrusion bonding combined with two-stage artificial cooling Author links open overlay panel

AZ31 Mg alloy with heterogeneous bimodal grain structure(smaller grain size of 5-20µm and coarser grain size of 100-200µm)was subjected to accumulated extrusion bonding(AEB)at 250℃combined with two-stage artificial cooling in this work,viz.local water cooling and artificial cooling.The microstructure developed consecutively as a result of discontinuous dynamic recrystallization(DDRX)for the AEBed samples.{10-12}tensile twinning also played an important role for the AEB with local water cooling at the initial extrusion stage in the container.Local water cooling could further reduce the DRXed grain size to~2.1µm comparing that without water cooling.And the grain growth rate was reduced by artificial cooling out of extrusion die.Under the combination of two-stage cooling,the fine DRXed grains at sizing band were almost retained with average grain size of~2.3µm after the sheet out of extrusion die,and the unDRXed grains with high residual dislocation density accumulation were also reserved.The tensile tests results indicated that a good strength-ductility balance with a high ultimate tensile strength(319 MPa vs.412 MPa)and fracture elongation(19.9%vs.30.3%)were obtained.The strength enhancement was mainly owing to the grain refinement and local residual plastic strain reserved by the artificial cooling.The excellent ductility originated from fine DRXed microstructure and ED-tilt double peak texture.

Removal of kathon by UV-C activated hydrogen peroxide:Kinetics,mechanisms,and enhanced biodegradability assessment

Kathon(CMI-MI),a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one(CMI)and 2-methyl-4-isothiazolin-3-one(MI),was extensively used in industry as a nonoxidizing biocide or disinfectant.However,it would show adverse effects on aquatic life when it is discharged into surface water.In this study,the removal performance,parameter influence,degradation products and enhancement of subsequent biodegradation of CMI-MI in UV/H_(2)O_(2)system were systematically investigated.The degradation rate of CMI-MI could reach 90%under UV irradiation for 20 min when the dosage of H_(2)O_(2)was 0.3 mmol·L^(–1).The DOC(dissolved organic carbon)mineralization rate of CMI-MI could reach 35%under certain conditions([H_(2)O_(2)]=0.3 mmol·L^(–1),UV irradiation for 40 min).kobs was inversely proportional to the concentration of CMI-MI and proportional to the concentration of H_(2)O_(2).The degradation rate of CMIMI was almost unchanged in the pH range from 4 to 10.Except the presence of CO_(3)^(2-)inhibited the removal rate of CMI-MI,SO_(4)^(2-),Cl^(-),NO_(3)^(-),and NH_(4)^(+) did not interfere with the degradation of CMI-MI in the system.It was found that UV/H_(2)O_(2)system had lower energy consumption and more economic advantage compared with UV/PS system by comparing the EEO(electric energy per order)values under the same conditions.Two main organic products were identified,namely HCOOH and CH_(3)NH_(2).There’s also the formation of Cl^(-)and SO_(4)^(2-).After UV and UV/H_(2)O_(2)photolysis,the biochemical properties of CMI-MI solution were obviously improved,especially the UV/H_(2)O_(2)treatment effect was better,indicating that UV/H_(2)O_(2)technology is expected to combine with biotechnology to remove CMI-MI effectively and environmentally friendly from wastewater.

A Study of Water Treatment Chemical Effects on Type I” Pitting Corrosion of Copper Tubes

It is known that one of the causes of pitting corrosion of copper tubes is residual carbon on the inner surface. It was confirmed that type I” pitting corrosion of the copper tube is suppressed by keeping the residual carbon amount at 2 mg/m2 or less, which is lower than that of the type I’ pitting corrosion, or by removing the fine particles that are the corrosion product of galvanized steel pipes. The developed water treatment chemical was evaluated using three types of copper tubes with residual carbon amounts of 0 mg/m2, 0.5 mg/m2, and 6.1 mg/m2. The evaluation was conducted for three months in an open-circulation cooling water system and compared with the current water treatment chemical. Under the current water treatment chemical conditions, only the copper tube with a residual carbon amount of 6.1 mg/m2 showed a significant increase in the natural corrosion potential after two weeks, and pitting corrosion occurred. No pitting corrosion and no increase in the natural corrosion potential were observed in any of the copper tubes that were treated with the developed water treatment chemical. In addition, the polarization curve was measured using the cooling water from this field test, and the anodic polarization of two cooling waters was compared. For copper tubes with a large amount of residual carbon, the current density near 0 mV vs. Ag/AgCl electrode (SSE) increased when the developed water treatment chemical was added.

Effect of cooling conditions on corrosion resistance of friction stir welded 2219-T62 aluminum alloy thick plate joint

Friction stir welding (FSW) with water cooling and air cooling was used to weld 2219-T62 aluminum alloy joints with a thickness of 20 mm. The effect of cooling conditions on the corrosion resistance of joints in 3.5% NaCl solution was investigated using the open circuit potential (OCP), the potentiodynamic polarization, and the corrosion morphology after immersing for different time. And the precipitates distribution was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results reveal that the weld nugget zone (WNZ) owning positive potential, lower corrosion current density and fine and uniform precipitates, is much more difficult to corrode than the heat affected zone (HAZ) and the base metal (BM). Compared with air-cooled joint, the water-cooled joint has better corrosion resistance. In addition, the results of microstructure observation show that the potential, distribution and size of second phase particles determine the corrosion resistance of FSW AA2219 alloy joints in chlorine-contained solution.