Variable Flow Pump Research Articles

CONSTRUCTIVE-FUNCTIONAL ANALYSIS AND CALCULATION OF FLOW CONTROL VALVES

In hydraulic installations, the flow regulation is performed in two ways: volume regulation (by variable flow pump) and resistive regulation, with the help of the flow regulation equipment. The second variant, although with lower energy efficiency, is most often preferred in small and medium power installations, due to the constructional simplicity and easy maneuverability of the equipment, as well as the ease of performing operation control. The paper presents the construction of the most important devices for resistive flow regulation, the mode of operation and installation in the structure of the systems, as well as certain elements of their calculation.

Calibration and validation of models to estimate the hydraulic parameters of a confined aquifer in a tropical region

This article deals with the calibration and validation of models for water yield from a confined aquifer in a tropical region. From 2015 to 2019, 20 variable flow pumping tests were carried out. The average pumping flows varied between 0.07 and 17.4 L/s; the average drawdown of the water levels, between 5.99 and 50.94 m; the values of transmissivity and storage coefficient were lower than 77 m 2 /day and 6 x 10 -5, for probability of non-exceedance of 85%. In the calibration stage, the mean values of the coefficients of the proposed models a and b were in the order of 10 1 and 10 3. The determination coefficients obtained in the statistical adjustment of the proposed models are satisfactory, they varied between 76 and 85%. The validation stage revealed that the models need to be tested with a larger number of data.

Development of simulation models of the hydraulic system of passenger and transport aircraft in normal and failure situations

The paper presents a simulation model of the hydraulic system of an aircraft containing a block supply with a variable flow pump, the discharge line of which is presented in the form of a certain container with liquid, the modulus of elasticity of which is constant, and a hydraulic accumulator is installed in the discharge line a certain capacity and pre-charge pressure, resistance of the discharge and drain lines. The developed simulation model allows failure situations, such as: violation of the internal and external tightness, changing the parameters of the accumulator, reducing the pressure of zero flow due to a change in the stiffness of the springs of the control spool and the servo piston of the regulator, jamming regulator in an intermediate position, etc. In addition, the model allows you to calculate the heat losses associated both with the aircraft flight mode and with changes in the hydrodynamic parameters of the system in regular and failure modes.

Selection of design parameters of the system for changing the supply of power supplies for hydraulic systems of aircraft

The article develops a mathematical model of the variable flow pump of the aircraft power supply, designed to simulate the operation of the power supply depending on the speed of the sustainer engine, oil temperature, pressure and supply (removable power). In addition, a control algorithm has been developed that provides the required quality of the transient process, which is achieved by installing additional hydraulic resistances between the servo piston cavity, the drain hydraulic line and the control spool, which change the flow characteristic of the pump and contribute to the fastest attenuation of the transient process and reduce its oscillation.

Constructive-Functional Analysis and Calculation of Flow Control Valves

In hydraulic installations, the flow regulation is performed in two ways: volume regulation (by variable flow pump) and resistive regulation, with the help of the flow regulation equipment. The second variant, although with lower energy efficiency, is most often preferred in small and medium power installations, due to the constructional simplicity and easy maneuverability of the equipment, as well as the ease of performing operation control. The paper presents the construction of the most important devices for resistive flow regulation, the mode of operation and installation in the structure of the systems, as well as certain elements of their calculation.

A young patient burdened with many diseases with a very high cardiovascular risk; a therapeutic challenge not only for the doctor

A 39-year-old patient with hypertension and a 28-year history of type 1 diabetes with numerous complications in the form of microangiopathy and macroangiopathy was admitted to the Cardiology Clinic due to recurrent angina pectoris accompanied by the intensification of ischemic electrocardiographic (ECG) changes and symptoms of heart failure. In addition, a history of hyperlipidemia, chronic kidney disease, Graves’ disease at euthyroid stage. On admission, the patient hemodynamically stable, arterial pressure — 129/75 mm Hg, regular heart rate, without signs of losses in the pulmonary circulation, visible swelling of the lower limbs and trophic changes on the lower shink. In laboratory tests, mildly impaired renal function (glomerular filtration 56 ml/min), high blood glucose values (up to 350 mg/dL), glycated hemoglobin 8.7%, hypercholesterolemia. The echocardiographic study showed a worsening of the left ventricular systolic function compared to the previous assessment — a decrease in ejection fraction from 46 to 35%, on ECG — left anterior hemiblock, features of past and anterior wall infarction. During hospitalization, the therapy of coronary heart disease, hypertension (ramipril, bisoprolol, spironolactone, and furosemide), diabetes (insulin initially used at a variable flow pump, followed by intensive insulin therapy and hyperlipidemia was modified), obtaining satisfactory results in relation to the initial ones. Extended release nitrates were included, and antiplatelet treatment with ticagrelor was continued. Due to elevated cholesterol, the dose of atorvastatin was increased. In case of therapy failure, the PCSK9 inhibitor (evolucumab) and family diagnosis of hypercholesterolemia were considered. Despite the treatment, angina ailments increased, the ECG performed during the pain revealed ischemic lesions. By decision of the Heart Team, the patient was qualified for accelerated surgery for myocardial revascularization.

Energy Efficiency Analysis of Fixed-Speed Pump Drives with Various Types of Motors

The paper presents a comparative analysis of energy consumption by 2.2 kW electric motors of various types and energy efficiency classes in the electric drive of a pump unit with throttle control in a water supply system. Line-start permanent-magnet synchronous motors of the IE4 energy efficiency class and induction motors of the IE4 and IE3 energy efficiency classes of various manufacturers were considered (IE4 and IE3 are labels of energy efficiency classes of electric motors according to IEC 60034-30-1 standard). Energy consumption at a hydraulic load changing under a typical duty cycle was calculated based on the nameplate data of the pump and electric motors. The developed method shows that selecting an electric motor based on the IE energy efficiency class under the IEC 60034-30-1 standard (i.e., based on efficiency at a rated load) may not provide the minimum energy consumption of a variable flow pump unit over a typical duty cycle. In particular, the considered IE4 class line-start permanent-magnet synchronous motors do not provide significant advantages over IE4 class induction motors, and sometimes even over IE3 class induction motors when they are used in variable flow pump units.

Identification of Design Criteria for District Cooling Distribution Network with Loop-Type System

The most expensive portion of a large-scale district cooling system is the distribution network that conveys chilled-water to multiple buildings at controlled rates for use in comfort cooling. As the piping system needs large initial investment cost, a thorough investigation would be required to properly design the network. In order to come up with the solution a methodology for an optimal design of district cooling distribution network with loop-type system is needed. In this study, a district cooling distribution network model with loop-type system was investigated by calculating the system pressure drop, system volumetric flow rate and volumetric flow rate for each building. Friction factor identification, system simulation and optimization were performed based on the design temperature difference of 9°C with supply temperature of 4.5°C. The governing equations consisted of mass conservation, performance curve of variable primary flow pumping scheme, energy equations due to pipe friction and an equation that indicates the algebraic sum of head losses around any closed loop must be zero. Multivariable Newton-Raphson method was used to solve the system of nonlinear equations with the elements of solution vector determined using singular-value decomposition method. Exhaustive search method was used to solve the objective function and subsequently determine the piping network design criteria that yields minimum overall cost. Numerical results were also compared with traditional methods and have found some degree of similarities of pipe sizes except for pressure drop values exceeding 100 Pa/m.

Theoretical Analysis and Design of a Variable Delivery External Gear Pump for Low and Medium Pressure Applications

This paper describes a unique design concept that is capable of electronically controlling the flow delivered by an external gear pump (EGP). The principle used for varying the flow relies on the variable timing concept which has been previously demonstrated by the author's research team for EGP's operating at high pressures (HPs) (p > 100 bar). This principle permits to vary the flow within a certain range, without introducing additional sources of power loss. In this paper, the above concept has been applied to formulate a design for a variable delivery EGP for low pressure (LP) applications (p < 30 bar), suitable for direct electric actuation. Specific design principles for the gear and the flow variation mechanisms are introduced to limit the force required by the electric actuation, and for maximizing the flow variation range. Also, the low target pressure allows the variable timing principle to be realized with an asymmetric solution, with only one variable timing element present at one side of the gears. A detailed analysis concerning the relationship between the electrically commanded position of the flow varying element and the theoretical flow delivered by the pump is also presented. This analysis is used to formulate analytical expressions for the instantaneous flow rate and the flow nonuniformity of the pump. The paper details the design principle of the proposed variable flow pump and describes the multi-objective optimization approach used for sizing the gears and flow variation mechanism. The paper also discusses the experimental activity performed on a prototype of the proposed unit, able to achieve a flow variation of 31%.

Experimental verification of a virtual water flowmeter applicable to air conditioning systems

The main purpose of this research is to suggest a virtual water flowmeter applicable in hydraulic systems with low-cost sensors. Practical procedures for realizing virtual water flowmeters for constant flow pumps (i.e., Cases 1 and 2) and variable flow pumps (i.e., Cases 3 and 4) are proposed in this paper. In Case 1, for measuring the water flow rate through a constant flow pump, the pump head was measured and the water flow rate was estimated using the pump characteristic curve obtained from the manufacturer or by deriving an empirical model based on the field measurement data. In Case 2, the water flow rate through a valve with a constant flow pump was estimated by measuring the pressure head between the valve and the valve opening position. The valve characteristic curve can be obtained by deriving an empirical model based on the initial field test results. The water flow rate through the variable flow pump was calculated, using the pump affinity laws and an empirical model, by measuring the frequency (i.e., Case 3) or input power (i.e., Case 4). The initial setup and test procedures for virtual flowmeters are also proposed in this research for practical use in the field. To verify the proposed procedures, experiments were conducted using constant and variable flow pumps in a pilot system. It was found that the virtual water flowmeters showed 2.9% to 6.7% of root mean square error from Case 1 to Case 4, compared with an ultrasonic water flowmeter, through long-term experimental verification.

A simulation-based analysis of variable flow pumping in ground source heat pump systems with different types of borehole heat exchangers: A case study

A simulation model of ground source heat pump systems has been used to investigate to what extent a variable flow of the heat-carrier fluid of the ground loop affects the energy efficiency of the entire system. The model contemporaneously considers the borehole heat exchangers, the heat pump, the building load, and the control strategies for the circulation pumps of the ground loop. A constant speed of the circulation pumps of the ground loop was compared with a variable flow controlled by means of a constant temperature difference across the heat pump on the ground side considering the load profile of an office building located in North Italy. The analysis was carried out for a single U-tube, double U-tube and coaxial pipe heat exchangers. The control strategies adopted to manage the flow rate of the heat-carrier fluid of the ground loop affect both the heat exchange rate of the borehole field and the heat pump’s long-term energy efficiency. The simulations show considerable differences in the system’s seasonal energy efficiency. The constant speed of the circulation pumps leads to the best results as far as the heat pump’s energy performance was concerned, but this advantage was lost because of the greater amount of electrical energy used by the circulation pumps; this, of course, affects the energy efficiency of the entire system. The optimal solution appears then to be a constant temperature difference in the heat-carrier fluid across the heat pump.

Effect of Flow Velocity on Chlorine Decay in Water Distribution Network:A Pilot Loop Study

Experiments were run in the pipe loop setup to estimate bulk and wall chlorine decay rates under varying flow and chlorine levels for groundwater. A recirculating loop of 50 mm inner diameter polyvinyl chloride pipe and a variable flow pump with feed and recirculation tank were used to design a pipe loop. Sodium hypochlorite was introduced as free chlorine into the test water. The study came up with three important findings: (a) bulk chlorine decay rate in test water decreased with increase in chlorine levels, which is attributed to the type and level of organic matter present in test water. (b) Chlorine decay rate in pilot loop setup increased with increase in flow velocity. The result showed that under turbulent conditions, in addition to chlorine, mass flux transfer from bulk to wall and biofilm removal from pipe surface contributed to chlorine decay. We also noted that with increase in flow velocity the contribution of bulk reaction to total chlorine decay in pipe loop decreased. (c) ANOVA test on experimental dataset showed that as compared to initial chlorine levels, flow velocity has statistically significant effect on chlorine dissipation in a pipe loop. We also found that after turbulent flow is achieved, the effect of flow velocity on the wall decay is negligible.

Identification of Design Criteria for District Cooling Distribution Network with Ice Thermal Energy Storage System

Two (2) distribution network models of district cooling system with ice thermal energy storage system are presented in which the theoretical system pressure drop, system flow rate and flow rate requirements in each energy transfer station were determined. The hydraulic calculation and system simulation of distribution networks with and without secondary lines are evaluated based on system temperature difference set-point of 11°C. Variable primary flow pumping system arrangement was used to improve energy usage and to eliminate the need for a distribution pump in the network. The system of nonlinear equations was solved using multivariable Newton-Raphson method. The linearized equations revealed that coefficient matrices formed between the two networks were different from each other which suggested that different decomposition algorithms must be used to properly determine the solution vectors. Optimization technique such as exhaustive search method was adopted to identify the piping network design criteria that could yield minimum overall cost.

Application of a meta-analysis of aortic geometry to the generation of a compliant phantom for use in particle image velocimetry experimentation

The evolution of pressure-flow geometry in the aortic arch is increasingly understood as a key element in the treatment of hemodynamic dysfunction in patients. However, little is known about the properties of the flow across the aortic geometry and thus the sensitivity of sensor placement is also unknown. Compliant models of the aortic path can be built to allow techniques such as particle image velocimetry to measure the velocity fields.This paper presents the justification and production methodology used to generate a compliant model of the aortic arch that represents the geometry and compliance of typical hemodynamics patients. The information from twenty papers was synthesized to generate a single model of the aortic arch. The model incorporates the three branching arteries at an apex of a tapering aortic path experimental that has been manufactured as a flexible thin-walled silicon model. Calculations were undertaken to ensure that the model matches the in vivo compliance of the arteries.The experimental setup uses the compliant silicone model of the aorta with variable flow pump to mimic the cardiac cycle, and a variable extramural pressure to mimic changes in intrathoracic pressure. This research was necessary for the development of an accurate experimental setup that would enable results that are immediately applicable to the research of cardiovascular therapy optimization.

Combined optimization of a wind farm and a well field for wind-enabled groundwater production

Energy requirements constitute a significant cost in groundwater production and can also add to a large carbon footprint when fossil fuels are used for power. Wind-enabled water production is advantageous as it minimizes air pollution impacts associated with groundwater production and relies on a renewable resource. Also, as groundwater extraction represents a deferrable load (i.e., it can be carried out when energy demands within an area are low), it provides a convenient way to overcome the intermittency issue associated with wind power production. Multiple turbine wind farms are needed to generate large quantities of power needed for large-scale groundwater production. Turbines must be optimally located in these farms to ensure proper propagation of kinetic energy throughout the system. By the same token, well placement must reconcile the competing objectives of minimizing interferences between production wells while ensuring the drawdowns at the property boundary are within acceptable limits. A combined simulation–optimization based model is developed in this study to optimize the combined wind energy and water production systems. The wind farm layout optimization model is solved using a re-sampling strategy, while the well field configuration is obtained using the simulated annealing technique. The utility of the developed model is to study wind-enabled water production in San Patricio County, TX. Sensitivity analysis indicated that identifying optimal placement of turbines is vital to extract maximum wind power. The variability of the wind speeds has a critical impact on the amount of water that can be produced. Innovative technologies such as variable flow pumping devices and aquifer storage recovery must be used to smooth out wind variability. While total groundwater extraction is less sensitive to uncertainty in hydrogeological parameters, improper estimation of aquifer transmissivity and storage characteristics can affect the feasibility of wind-driven groundwater production.

A three-dimensional microfluidic approach to scaling up microencapsulation of cells

Current applications of the microencapsulation technique include the use of encapsulated islet cells to treat Type 1 diabetes, and encapsulated hepatocytes for providing temporary but adequate metabolic support to allow spontaneous liver regeneration, or as a bridge to liver transplantation for patients with chronic liver disease. Also, microcapsules can be used for controlled delivery of therapeutic drugs. The two most widely used devices for microencapsulation are the air-syringe pump droplet generator and the electrostatic bead generator, each of which is fitted with a single needle through which droplets of cells suspended in alginate solution are produced and cross-linked into microbeads. A major drawback in the design of these instruments is that they are incapable of producing sufficient numbers of microcapsules in a short-time period to permit mass production of encapsulated and viable cells for transplantation in large animals and humans. We present in this paper a microfluidic approach to scaling up cell and protein encapsulations. The microfluidic chip consists of a 3D air supply and multi-nozzle outlet for microcapsule generation. It has one alginate inlet and one compressed air intlet. The outlet has 8 nozzles, each having 380 micrometers inner diameter, which produce hydrogel microspheres ranging from 500 to 700 μm in diameter. These nozzles are concentrically surrounded by air nozzles with 2 mm inner diameter. There are two tubes connected at the top to allow the air to escape as the alginate solution fills up the chamber. A variable flow pump 115 V is used to pump alginate solution and Tygon® tubing is used to connect in-house air supply to the air channel and peristaltic/syringe pump to the alginate chamber. A pressure regulator is used to control the flow rate of air. We have encapsulated islets and proteins with this high throughput device, which is expected to improve product quality control in microencapsulation of cells, and hence the outcome of their transplantation.

Energy Consumption Analysis of Variable Flow Pump under Different Pipe Network

In the different types of pipe network, the running performances of the variable flow pump were calculated, using pipe valve control, the number of units control and the frequency control to adjust water flow of system, and the impacts of pipeline types on energy consumption of variable flow pump were discussed. The relationships between performance of the pipe network and pump operating condition were analyzed, including the relationship between various flow control methods and pump energy consumption. The calculated results show that the pipe characteristic produces a great impact on energy consumption of variable flow pump. The adjusting flow of system by increasing pipe resistance can also reduce pump’s energy consumption, and the amount of energy reduced is greater in closed circulation pipeline than in open type pipeline. The variable frequency drive mode has big and different impacts on energy consumption between closed circulation and open type pipeline, the greater the static pressure value, the smaller the energy saving effect. The number control and the frequency control for pump are two effective methods of energy adjustment in the loop pipe networks, the change rates of power and flow do not meet the similarity law dew to the pipe network changed.

Integration of variable refrigerant flow and heat pump desiccant systems for the heating season

Integration of the variable refrigerant flow (VRF) and heat pump desiccant (HPD) systems was investigated in a field performance test for a heating season. The HPD systems use only the moisture in the outdoor air and return air to humidify the indoors during ventilation in the heating season. Three different operating modes: non-ventilated, HPD ventilation assisted and HPD ventilation–humidification assisted VRF systems were investigated. It was found that the VRF systems provided an average of 93.5% of the total heating energy for the HPD ventilation assisted mode. The remainder was the recovered heat by the HPD systems during ventilation. The VRF systems provided an average of 46.8% of the total heating energy for the HPD ventilation–humidification assisted mode. The remainder was covered by the HPD systems which provided additional sensible and latent heating. Overall, among the three operating modes, it is concluded that the HPD ventilation–humidification assisted VRF outdoor units consume less energy than the HPD ventilation assisted ones (about the same energy as the non-ventilated ones), while providing the best indoor thermal comfort and indoor quality conditions. For the total system, the HPD ventilation–humidification assisted VRF systems consume less energy than the HPD ventilation assisted ones.

Abstract 5953: Flow Pulsation Affect Distal Pulmonary Artery Endothelial Cell mRNA Expression

Background: Due to the development of pulmonary arterial hypertension (PAH), distal pulmonary artery endothelial cells (dPAEC) are exposed to wall shear stress (SS) that is different in physical characteristics compared to normal condition. The effect of individual components of SS on PAEC biology has not been thoroughly examined. Thus the current study was designed to examine how dPAEC respond to different component of SS in regarding to gene expression including adhesion molecules: ICAM, VCAM, E-selectin; chemokine: MCP-1 and growth factors:VEGF, Flt-1. Methods: Bovine dPAEC were cultured and placed on fibronectin-coated slides till confluent. Cells were then exposed to SS with different frequency (1Hz, 2Hz), pulsation (low, medium and high with an average SS of 14 dynes/cm 2 ) and time (1hr or 6hrs). The flow studies were carried out using a flow chamber connected to a variable speed flow pump. All data was represented as fold change relative to static condition. Results: As shown in table below, The effect of flow frequency on gene expression depends on individual gene. There was no difference of ICAM expression between 1Hz and 2Hz. Frequency of 2Hz significantly increased VCAM and MCP-1 expression compared to frequency of 1Hz. Compared to static condition, steady flow increased all gene expression. One hour pulsatile flow further increased ICAM, VCAM, E-selectin and MCP-1 but not VEGF or Flt-1 expression as pulsation increased. 3) Prolonged pulsatile flow further increased all gene expression. Conclusion: Physical characteristics of flow, especially flow pulsation stimulate dPAEC gene expression which can contribute to the development of PAH.

Effectiveness of a Prolapsed Bird's Nest Filter

The authors evaluated the variable deployment of the Bird's Nest filter, including frequency and extent of prolapse in clinical use, and analyzed the effects of this variability on clot-trapping efficiency with an in vitro model. In the clinical placement of 20 filters, the average length of cephalic filter wires from the center of the filter was measured from radiographs obtained immediately after placement. To analyze the effects of prolapse, a variable-rate pump was used to mimic the effects of respiration on IVC flow. Four clot sizes (5 x 20, 5 x 40, 10 x 20, and 10 x 40 mm) were evaluated with four filter configurations with wires stretched to different lengths in a cephalic direction from the center of the filter: 2 cm (normal-tight), 5 cm (normal-loose), 8 cm (moderate prolapse), and to a maximum of 12 cm (maximum prolapse). Ten passes for each clot size were performed with each filter configuration in both the horizontal and vertical positions. The smallest clots were also tested with a slower constant-rate pump. In clinical use, the average length of the filter wire was 5.4 cm (range, 1.2-9.0 cm). With the variable flow pump, the in vitro degree of prolapse did not significantly decrease the trapping efficiency for any but the smallest (5 x 20-mm) clots, for the maximum prolapse configuration in the horizontal position (P = .01). In addition, for these clot sizes, the filter was more efficient with the slower constant rate compared with the faster variable rate; this difference was only statistically significant in the horizontal position for the maximum prolapse configuration (P = .007). The results suggest that in clinical practice, a prolapsed Bird's Nest Filter remains effective for all but small clots.