Mixing Valve Research Articles

Pitting corrosion failure of an AISI stainless steel pointer rod

In this study, failure analysis of a thermostatic mixing valve pointer rod made of AISI 304 stainless steel was performed. Visual examination, followed by an in-depth microstructural characterization using optical and scanning electron microscopy, was carried out for understanding the primary cause of failure. Energy dispersive X-ray, X-ray diffraction analysis and transmission electron microscopic analyses were also necessary supplements to this investigation. Finally, the obtained results infer that the combined effect of large amounts of MnS inclusions and the presence of deformation induced martensite adversely affected the pitting corrosion resistance of the pointer rod material. It is concluded that the pointer rod material was not properly investigated for defects prior to and after its fabrication.

Droplet breakage and coalescence models for the flow of water-in-oil emulsions through a valve-like element

An experimental and theoretical study was carried out regarding the evolution of droplet size distributions for the flow of water in oil emulsions through a valve-like element that simulates a mixing valve. The water droplets had diameters in the 0.1–100μm range, which includes droplets that are either smaller or larger than the Kolmogorov length scale for the experimental conditions. Droplet breakage and coalescence models that can be used for this size range were proposed. A simplified population balance model was developed to interpret the experimental data and solved by the method of classes. The model parameters were estimated by the orthogonal distance regression method. The simplifying assumption of the model was verified by global optimization using a parallel implementation of the particle swarm optimization method. The agreement between simulated and experimental droplet volume size distributions was good. The predictions of the DeBroukere mean diameter, d43, were unbiased with mean errors of 8%.

Operation of a Mixing Seal Valve in Calcium Looping for CO2 Capture

Calcium looping has attracted a great deal of attention among researchers investigating CO2 capture systems. Energy consumption in the regeneration reactor is one of the most important issues. However, as a high-temperature process, calcium looping enables an efficient heat recovery in the capture process itself. The objective of this study is to reduce the energy consumption in the calciner by increasing the temperature of the solids entering this reactor. A calcium looping system including a mixing seal valve is modeled and analyzed to determine the potential advantages this configuration entails. The influence of different seal valve aeration gases, carbonator inventories and solid circulation between reactors is assessed. The reduction of the fuel consumption when the mixing seal valve is aerated with flue gas tends to dilute the CO2 stream. When using CO2, the achievement of substantial energy savings may imply an important increase of the solid flows in the system. Aeration of the mixing seal valve ...

Design and Research of a New Thermostatic Valve

This study designed a new type of intelligent thermostatic mixing valve which could keep the temperature and flux of the outlet water constant by the adaptive controller. It firstly established mathematical model of the valve about angle-flux and angle-temperature and then it applied the Fluent software to numerical simulation of the valve about flow field based on the two-equation turbulence model. Finally, it designed the intelligent controller hardware and developed the controlling software of the valve. With the controller and it finished experiments with the thermostatic valve prototype. The results of simulation and experiments prove that the correctness of the theoretical research and they can be used to improve designing of the thermostatic valve.

Financial analysis of the implementation of a Drain Water Heat Recovery unit in residential housing

One of the ways of diminishing energy consumption for hot water heating is the use of Drain Water Heat Recovery (DWHR) units. The aim of the use of these devices is thermal energy recovery from warm drain water and transferring it to incoming cold water. This paper presents the calculation model that allows the estimation of the financial efficiency of the project involving the construction of a shower Drain Water Heat Recovery system in a single-family dwelling house. The presented method of investment risk assessment can be used for decision making by individual users, designers and others. The study of the financial performance was carried out for the various parameters of the installation and the different heat recovery system configurations. From investors point of view the most beneficial option of heat recovery system installation is the system in which preheated water is fed to both the hot water heater and shower mixing valve. Additionally, it was proved that obtained financial results are affected by showering time and water consumption. DWHR units will be therefore particularly beneficial to apply in case of swimming pools, sports facilities or fitness clubs, where high rotation of users is observed.

Modeling and Simulation of Thermostatic Mixing Valve

It researched a new type of intelligent thermostatic mixing valve which could keep the temperature and flux of the valve outlet water constant through the adaptive controller. It firstly established the mathematical model about angle - flux and angle - temperature of the valve. And then it based on thekεturbulence model and applied Fluent software to numerical simulation of the valve about the flow field. Finally, it compared the simulation results with the calculated value. The results show that they are basically consistent, prove the correctness of the theoretical research, and can be used to improve designing of the thermostatic valve.

On-pump fibrillating heart mitral valve replacement with the SAPIEN XT transcatheter heart valve

In some high-risk patients, standard mitral valve replacement can represent a challenging procedure, requiring a risky extensive decalcification of the annulus. In particular, high-risk redo patients and patients with a previously implanted transcatheter aortic valve, who develop calcific mitral disease, would benefit from the development of new, minimally invasive, transcatheter or hybrid techniques for mitral valve replacement. In particular, mixing transcatheter valve therapies and well-established minimally invasive techniques for mitral replacement or repair can help in decreasing the surgical risk and the technical complexity. Thus, placing transcatheter, balloon-expandable Sapien™ XT stent-valves in calcified, degenerated mitral valves through a right thoracotomy, a left atriotomy and on an on-pump fibrillating heart, represents an attractive alternative to standard surgery in redo patients, in patients with concomitant transcatheter aortic stent-valves in place and in patients with a high-risk profile. We describe this hybrid technique in detail.

Still Too Hot

Although water heater manufacturers adopted a voluntary standard in the 1980s to preset thermostats on new water heaters to 120°F, tap water scald burns cause an estimated 1500 hospital admissions and 100 deaths per year in the United States. This study reports on water temperatures in 976 urban homes and identifies water heater and household characteristics associated with having safe temperatures. The temperature of the hot water, type and size of water heater, date of manufacture, and the setting of the temperature gauge were recorded. Demographic data, including number of people living in the home and home ownership, were also recorded. Hot water temperature was unsafe in 41% of homes. Homeowners were more likely to have safer hot water temperature (<120°F) than renters (63 vs 54%; P < .01). For 11% of gas water heaters, the water temperature was >130°F, although the gauge was set at less than 75% of its maximum setting. In a multivariate logistic regression, electric water heaters were more likely to have safe hot water temperatures than gas water heaters (odds ratio R=4.99; P < .01). Water heaters with more gallons per person in the household were more likely to be at or below the recommended 120°F. Our results suggest that hot water temperatures remain dangerously high for a substantial proportion of urban homes despite the adoption of voluntary standards to preset temperature settings by manufacturers. This research highlights the need for improved prevention strategies, such as installing thermostatic mixing valves, to ensure a safer temperature.

Experimental analysis of an on demand external domestic hot water production system using four control strategies

In the paper, an experimental investigation on the performance of a space/water heating system using an on demand external domestic hot water production system (DHWPS) with different control strategies is reported. The tested DHWPSs consisted of a plate heat exchanger, a circulating pump, a flow switch and a thermostatic regulation valve. Four different control valves were considered in the analysis, comprising a 3-way mixing valve on the DHW-side, two different 2-way valves on the tank-side and a 3-way valve on the tank-side. Experiments have been performed heating the water in the tank up to 80°C and considering DHW draw-off flow rates of 5, 10, 15 and 20 l/min at a set temperature of 45°C. In the study the thermal behaviour of the four DHWPSs is analysed and compared, as well as its effects on the thermal performance of the tank during consumption operation. Results show that the control strategy of the DHWPS significantly influences the quality of the DHW supply and the thermal performance of the storage tank.

Simulation and evaluation of stratified discharging and charging devices in combined solar thermal systems

Abstract This simulation study investigates different discharging and charging strategies and their effects on the performance of a combined solar thermal system in a single family house. Based on the system according to Task 32 of the Solar Heating and Cooling Program of the International Energy Agency (IEA SHC) the system layout and in specific the storage connections are modified to investigate different stratified charging and discharging concepts realized by external valves or devices within the storage tank. A broad literature overview shows that a comprehensive comparison of charging and discharging strategies under the same boundary conditions and after optimization of the storage connection heights is not available. The results of this study show that a good thermal stratification within the storage and thus higher energy savings can be reached by both a stratified charging and discharging. Depending on the system size and the design of charging and discharging connections the stratified discharging leads to the same or even higher energy savings than a stratified charging. Already one single four-way mixing valve in the space heating flow (i.e. two tapping points) leads on the one hand to more than 80% of the advantage of an idealized discharging with seven tapping points, and on the other hand in all cases to significantly higher energy savings if compared to two charging devices with three-way valves. The relative energy savings increase with increasing solar fraction, e.g. with larger dimensions and better insulated buildings. The best option with the highest benefit depends on the system design like storage in- and outlet positions, system size and load conditions. Therefore, the decision for the best suited strategy can only be determined by simulations representing the respective system. The results presented in this paper, however, allow deriving general dependencies.

Modeling and Simulation of a Mixing System With Water Saving Function

This work focuses on the modeling and simulation of a mixing system for domestic use, which includes the water saving function. Water to be saved is the cold or partially cold water that reaches the mixing valve through the hot water inlet, as the tube length between the hot water source and the mixing valve is initially filled with cold water. Water saving function is obtained through a storage tank for accumulation of the initially cold or partially cold water, which is later used to feed the cold water inlet of the mixing valve. The accumulation system is designed such that accumulated water is preferably used than the cold water coming from the main cold water supply/distribution system to feed the cold water inlet of the mixing valve. Modeling considers fluid flow through the internal chambers of the system, the pressure evolution of water when flowing through the internal chambers of the system, and the temperature evolution of the separated and mixed water flows along the system. Simulation of the overall system is made using specialized tools to deal with stiff equations’ systems. Results show that, under real conditions, potable water savings of nearly 80% can be obtained relative to the water that is usually lost.

Feedforward control of a class of hybrid systems using an inverse model

Abstract In this paper we describe the design of a control algorithm for MISO systems, which can be modelled as hybrid fuzzy models. Hybrid fuzzy models present a convenient approach to modelling nonlinear hybrid systems. We discuss the formulation of a hybrid fuzzy model, its structure and the identification procedure. This is followed by a derivation of the inverse model and its implementation in the control algorithm. The control scheme we are discussing splits the control algorithm in two parts: the feedforward part and the feedback part. In the paper, we deal with the feedforward part of the control algorithm, which is based on an inverse of a hybrid fuzzy model. Next, a batch-reactor process is introduced. The modelling of the batch reactor is tackled and the results of the simulation experiments using the proposed control algorithm are presented. The experiments involved controlling the temperature of a batch reactor using two on/off input valves and a continuous mixing valve. The main advantage of the proposed approach is that the feedforward part of the control algorithm can bring the system close to the desired adjusted feasible trajectory, which avoids the need for a very complex feedback part of the algorithm. Therefore, the control algorithm presents a low computational burden, particularly comparing to the standard model predictive control algorithms. These usually require a considerable computational effort, which often thwarts their implementation on real industrial systems. Nevertheless, we show that using the proposed control approach the hybrid fuzzy model framework presents a convenient option for modelling complex systems for control purposes in practice.

Aerodynamic characteristics of nebulized terbutaline sulphate using the Andersen Cascade Impactor compared to the Next Generation Impactor

Characterization of the aerosol emitted from nebulizers is determined using the Next Generation Impactor (NGI). The Andersen Cascade Impactor (ACI) was previously used but the limitation of high flow rate used decreased its uses. We have investigated the use of ACI with different operational conditions compared to the NGI methodology. NGI was operated at a flow rate of 15 L min−1 after cooling at 5°C for 90 min. ACI was operated using flow rates 15 and 28.3 L min−1 at room (ROOM) temperature and after cooling at 5°C for 60 min (COLD). ACI was also operated using a flow rate 15 L min−1 through the nebulizer T-piece with a flow rate 28.3 L min−1 through ACI (15 Mix) using the mixing valve at ROOM and COLD. Two nebulizer systems, the Sidestream (SIDE) and the Aeroneb Pro (AERO) were used to nebulize terbutaline sulphate respiratory solution. Overall there was a highly significant difference (P < 0.001) between different ACI operating conditions for FPF and MMAD of both nebulizer systems. The ACI at higher flow rate increased the evaporation effect whilst cooling minimized evaporation of both nebulizer systems. Hence cooling and using slow flow rate minimizes evaporation effects with ACI. The ACI 15COLD results were similar to that of NGI. That supports the use of ACI at inhalation flow rate 15 L min−1 without fear of domination of gravity on ACI stages.

Automatic electrochemical sequential processing in a microsystem for urea detection

To demonstrate the possibility of automatic serial operation in a microanalysis system, components for valve operation, adjustment of mixing time, pH regulation, and sensing functions were integrated. Electrodes for actuation and sensing were formed on a glass substrate and flow channels and compartments were formed using poly(dimethylsiloxane) (PDMS). When a urea standard solution was filled in half of a mixing area, a mixing valve opened automatically and the solution merged with a urease solution initially filled in the other half. The length of time required for the mixing of components was adjusted by using a delay line, which extended from the electrode used for the mixing valve. After a time delay, an injection valve at the end of the mixing chamber was opened automatically. After the solution was injected into the compartment of the pH regulator using a nonstandard three-electrode system, the solution pH was elevated automatically. Gaseous ammonia produced accompanying the change was detected using an air-gap ammonia sensor. The existence of ammonia was clearly indicated by a change in electrode potential. The dependence of the potential on the logarithm of the concentration was linear, confirming the Nernstian response.

Techbits: Efficiency Improvements for Facilities Focus of Workshop

Techbits Innovations aimed at improving efficiencies in surface facilities were the focus of an SPE Applied Technology Workshop (ATW) titled "Surface Facilities: Improving Efficiencies in Production, Energy Conservation, CO2 Reduction, and Waste Management" held in Dubai. More than 50 attendees from 25 companies and 16 countries reviewed the challenges of oil/water/gas separation, conservation, emission, and waste management in the backdrop of increasingly stringent regulatory requirements. Abbas Ahmed Yousef, field manager for Adco's Bab field, opened the ATW with a keynote address focusing on the means to improve surface-facility efficiency, emphasizing the need for operators to adopt more enhanced oil recovery (EOR) techniques to improve production efficiencies. He also touched on the importance of energy conservation and emissions and waste management, particularly as producing fields mature. Oil/Water/Gas Separation and Handling In the ATW's first session, Ahmed Abdulmajeed of Saudi Aramco discussed process enhancements in gas/oil separation plants within his company. He reviewed how a new mixing valve for wash water going to desalters was able to reduce wash water consumption from 50 to 30 gallons per minute, resulting in more than 10 million gallons of water savings over one year. He also discussed how the implementation of a smokeless, high-pressure air-assisted flare system, which employs a new flare-tip design and additional flare-tip shield, provides for better gas combustion. Saudi Aramco is also testing an in-line water separator that promises to remove approximately 70–80% of water without the need to treat in a gas/oil separation plant and with quality in the range of 22–35 ppm of oil in water. Alexander de Kruijf of Petroleum Development Oman (PDO) discussed the pitfalls of improper oil and gas sampling and made predictions on future process-equipment design. Inaccurate measurement of H2S in one PDO application led to deteriorating sales gas quality, with H2S concentrations reaching 5 ppm. The result was 4 months of deferment equivalent to approximately 100,000 BOPD. To prevent acid corrosion in equipment, de Kruijf stressed the importance of routinely measuring for organic acid, using corrosion-resistant alloys with increased corrosion allowances, and implementing organic pH neutralizers. In general, he advised that production chemistry programs should be an integral part of a project's process. Oliver Garnier of Total reviewed a strategy to maintain production from his company's mature Abu Al-Bukhoosh field. The field has been producing since 1974, and present production is 15,000 BOPD with an average basic sediment and water (BS&amp;W) of 86%. By implementing improvements, including increasing the impeller size in the gas recovery compressor, closing wells with too high a BS&amp;W, optimizing well productivity by using multiphase flowmeters, and implementing de-emulsifier injection with gas lift, Total has managed to level the oil production potential to above 16,000 BOPD since 2007.

Hybrid fuzzy predictive control based on genetic algorithms for the temperature control of a batch reactor

In this paper we describe the design of hybrid fuzzy predictive control based on a genetic algorithm (GA). We also present a simulation test of the proposed algorithm and a comparison with two hybrid predictive control methods: Explicit Enumeration and Branch and Bound (BB). The experiments involved controlling the temperature of a batch reactor by using two on/off input valves and a discrete-position mixing valve. The GA-hybrid predictive control strategy proved to be a suitable method for the control of hybrid systems, giving similar performance to that of typical hybrid predictive control strategies and a significant saving with respect to the computation time.

Hybrid Model Predictive Control of a Solar Air Conditioning Plant

This paper describes the development and experimental validation of a multi-layer hybrid controller for optimizing energy management in a solar air conditioning plant. The hybrid nature of the process is due to its multi-mode structure: the refrigeration circuit can be fed by flat solar collectors, a storage system, by an auxiliary gas heater, or by a combination of them. The selection of the operating mode is obtained by switching electrovalves, pumps, and three-way mixing valves. The proposed multi-layer hybrid controller consists of a high-level supervisor that decides on-line the optimal operating mode through a hybrid model predictive control strategy, a static lower-level controller defining proper set-points for the chosen mode, and existing standard low-level controllers that ensure robust tracking of such set-points. The overall controller was designed in Matlab/Simulink using the Hybrid Toolbox, and then tested experimentally a real process, showing the effectiveness of the approach.

Design of a Microstructured System for Homogenization of Dairy Products with High Fat Content

AbstractHigh pressure homogenization of dairy products is today state of the art but limited by the fat content (max 17 vol.‐%). This article describes the development of a novel simultaneous homogenization and mixing (SHM) valve which allows homogenization of dairy products with a fat content of up to 42 vol.‐%. The challenging task of homogenizing dairy products with high fat content is to stabilize disrupted fat droplets especially against extensive aggregation. Aggregation and coalescence rates could be significantly reduced by a new microstructured valve allowing the emulsifier‐containing phase to be injected directly into the zone of droplet disruption.

Adaptive Supervisory Predictive Control of a Hybrid Fed-Batch Reactor with Slow Actuator

In this paper, adaptive supervisory predictive functional control is discussed for applications in a fed-batch reactor with slow continuous mixing valve, which acts as an actuator. The optimal operation regime of the reactor is to follow the reference trajectory without significant overshoot and to minimize the overall batch time. By adding the ingredients during the batch procedure, the volume in the reactor varies, tending to increase with time, as does the heat-transfer surface inside the reactor. This change causes variations in the batch-reactor dynamics, which can produce serious problems with the reactor's core-temperature control. Another problem that arises is the disturbance in the temperature inside the reactor, when additional ingredients added are at the outside temperature. In the pharmaceutical industry, a huge number of fed-batch reactors similar to ours are used for the production of drugs. The quality control is extremely strict, and it is necessary to follow the exact production recipe....

Self-adaptive supervisory predictive functional control of a hybrid semi-batch reactor with constraints

In this paper self-adaptive supervisory predictive functional control is studied for applications in a semi-batch reactor in which the optimal operation is to follow the reference trajectory without significant overshoot, and to minimize the overall batch time. The volume in the reactor varies, bending to increase with time, as does the heat-transfer surface inside the reactor. This causes variations in the batch-reactor dynamics which means serious problems with the reactor’s core-temperature control. The semi-batch reactor is used in the pharmaceutical industry for the production of drugs, where quality control is extremely strict and it is necessary to follow the exact production recipe. The semi-batch reactor is an example of a hybrid process where there are some discrete on/off valves and a continuous mixing valve. The supervisory control is designed to cope with the constraints and the discrete actuators. A simulation study was carried out to investigate the possible use of the proposed self-adaptive control algorithm in a real application.