Complete Pump Research Articles

Effects of thapsigargin and cyclopiazonic acid on twitch force and sarcoplasmic reticulum Ca2+ content of rabbit ventricular muscle.

Thapsigargin (TG) and cyclopiazonic acid (CPA) are reported to be specific high-affinity inhibitors of the sarcoplasmic reticulum (SR) Ca2+ pump in isolated membranes and cells, with TG causing complete pump inhibition at nanomolar concentrations. To evaluate the effectiveness of TG and CPA in small multicellular cardiac preparations, we used rapid cooling contractures (RCCs) to assess the SR Ca2+ load. In contrast to observations in single myocytes, TG caused remarkably slow and incomplete SR Ca2+ depletion in multicellular preparations. A 45-minute exposure to 500 microM TG at 30 degrees C and 0.5-Hz stimulation only decreased RCCs by 76 +/- 5% (and 100 microM CPA reduced RCCs by 59 +/- 10% [mean +/- SEM]). In contrast, 10 minutes with 20 mM caffeine completely abolished RCCs. This confirms that there was still a caffeine-sensitive pool of Ca2+ in the TG-treated muscle. The time constant of rest decay of RCCs was accelerated by both TG (from 83 +/- 18 to 26 +/- 6 seconds) and CPA (from 68 +/- 11 to 10 +/- 5 seconds). This might be expected since Ca2+ leaking from the SR during rest cannot be taken back up as efficiently, favoring Ca2+ extrusion by the sarcolemmal Na(+)-Ca2+ exchanger. TG and CPA decreased twitch force (by 44 +/- 7% and 40 +/- 11%, respectively) and increased twitch duration, presumably because of the SR effects. We conclude that complete blockade of SR Ca2+ uptake by TG or CPA in multicellular preparations cannot be assumed, even at high [TG] or [CPA], unless evaluated (eg, by RCC).

High-brightness, high-purity spin-polarized cesium beam.

We describe a cesium atomic beam (${10}^{14}$ atoms ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$, 6\ifmmode\times\else\texttimes\fi{}${10}^{16}$ atoms ${\mathrm{sr}}^{\mathrm{\ensuremath{-}}1}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$) spin polarized using light from two diode lasers. Of the atoms, 95% may be placed into either the 6${\mathit{S}}_{1/2}$(F,${\mathit{m}}_{\mathit{F}}$)=(3,3) or (4,4) state, with less than 2\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$ of the atoms left in the depleted hyperfine level. The latter fraction rises linearly with atomic beam intensity because of reabsorption of light scattered during the optical pumping process. This and other effects limiting complete hyperfine pumping are discussed.

Optical parametric oscillation with intracavity sum-frequency generation

Theoretical calculations of an optical parametric oscillator containing an intracavity sum-frequency crystal are presented for the case in which only the signal beam from the parametric generation process oscillates in the cavity. The pump beam that is not converted in the parametric generation process is summed with the signal beam to produce a beam at the desired frequency. The stable steady-state configurations that completely deplete the incident pump radiation are determined. When the sum-frequency crystal precedes the parametric-oscillator crystal, steady states with nearly complete pump depletion can occur for over a factor of twelve variation in the pump intensity. Other regimes of operation display period-doubling routes leading to chaotic solutions. A numerical calculation for conversion of 1.064- mu m radiation to 589-nm light yields an intensity conversion efficiency of 86.6%.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Wind Evaporator Heat Pumps—Part I: Test Methods

Wind evaporators are alternative evaporators for air source heat pumps which rely on wind-driven or natural convection to move air across the heat transfer surfaces. It is believed that, in certain climates, wind evaporators can operate satisfactorily with frost on their surfaces for extended periods of time and defrost passively during switch-off periods. If so, an active defrost cycle would be unnecessary in these climates. Wind evaporators present an opportunity for heat pumps to be less expensive, more reliable, and more energy-efficient. However, the heat transfer performance of wind evaporators varies as a result of changes in a wide range of climatic variables. To determine the technical feasibility of wind evaporators, it is necessary to test complete wind evaporator heat pumps and to compare their monitored field performance over extended periods to that of conventional heat pumps with fan-assisted, finned-tube evaporators. In this paper, a test facility which allows side-by-side testing of wind evaporator and conventional heat pumps and monitoring of weather conditions is described. The choice of measurement technique for each variable is discussed and estimates of the measurement uncertainty for each sensor are made.

Light generation in a system of two coupled waveguides

A laser structure consisting of two active films on a common substrate with a higher refractive index is proposed. The films are coupled by radiation modes through their common substrate. Dispersion curves are found for such structures. The distance over which there is a complete pumping of energy from one waveguide to another is found as a function of the substrate thickness. Generation has been achieved in a structure consisting of two polymethyl methacrylate films activated by the dye rhodamine 6G on a lithium niobate substrate with two external mirrors.

Two-Dimensional Flow Analysis of a Laboratory Centrifugal Pump

Two-dimensional potential flow was used to determine the velocity field within a laboratory centrifugal pump. In particular, the finite element technique was used to model the impeller and volute simultaneously. The rotation of the impeller within the volute was simulated by using steady-state solutions with the impeller in ten different angular orientations. This allowed the interaction between the impeller and the volute to develop naturally as a result of the solution. The results for the complete pump model showed that there are circumferential asymmetries in the velocity field, even at the design flow rate. Differences in the relative velocity components were as large as 0.12 m/s for the radial component and 0.38 m/s for the tangential component, at the impeller exit. The magnitude of these variations was roughly 25 percent of the magnitude of the average radial and tangential velocities at the impeller exit. These asymmetries were even more pronounced at off-design flow rates. The velocity field was also used to determine the location of the tongue stagnation point and to calculate the slip within the impeller. The stagnation point moved from the discharge side of the tongue to the impeller side of the tongue, as the flow rate increased from below design flow to above design flow. At design flow, values of slip ranged from 0.96 to 0.71, from impeller inlet to impeller exit. For all three types of data (velocity profiles, stagnation point location, and slip factor) comparison was made to laser velocimeter data, taken for the same pump. At the design flow, the computational and experimental results agreed to within 17 percent for the velocity magnitude, and 2 deg for the flow angle. The stagnation point locations coincided for the computational and experimental results, and the values for slip agreed to within 10 percent.

Experimental study of melting ice cylinders in a warm air cross-flow

An experimental study is reported which investigates the melting of ice cylinders transverse to a warm humid flow, under controlled conditions in an air-conditioned wind tunnel. This work was initiated prior to a more general study of warm air defrosting of a complete heat pump evaporator. Tests were conducted with air at various temperatures, relative humidities and velocities. Similarly, the temperature of the core tube, on which the ice cylinders were mounted, was varied by alteration of the water-glycol mixture flowing through it. Two diameters of ice cylinder, 20 and 27 mm, were used. For core temperatures below the melting point of ice, the melting rate was shown to be a strong function of air humidity and temperature. With the core temperature above 0°C, the melting process was dominated by this factor so that air conditions were relatively unimportant.

Evaluation of centrifugal pump performance in nuclear power plants

A systematic approach is developed for prediction of performance of single, as well as double-entry, centrifugal pumps in a specific speed range of 600 to 2500 engineering units. Complete pump characteristics can be mapped, from shut-off conditions to 130% of the design flowrate. Given the dimensions of a centrifugal pump, as well as the impeller rotational speed, the method can be employed in prediction of head vs flowrate ( H- Q), shaft power vs flowrate (BHP- Q) and efficiency vs flowrate ( E- Q) curves. Pump characteristics can then be used to model pump performance in state-space. This allows for development of optimal control strategies, for design of controllers. and for examination of the sensitivity of operation to changes in design and performance parameters. Hence, optimization of process design and operation becomes attainable. Application of the method to a nuclear-grade coolant pump demonstrated the viability of the model as a tool in simulation of pump response to various inputs. State-space representation is shown to be invaluable in simulation of performance at normal and abnormal operation conditions, synthesis of surveillance schemes and in detection of abnormalities caused by degradation of the components.

The Pumping Dynamics of a Positive Displacement Pump Employing Self-Acting Valves

The paper describes a general purpose digital computer model for the analysis of the pumping dynamics of positive displacement pumps employing self-acting valves. This model is verified by comparison with experimental tests on a diaphragm separator pump. Predicted and simulated cylinder pressure transients and inlet and delivery valve dynamics are compared over the complete pumping cycle. Close agreement between theory and experiment is achieved. The induction performance of the pump is examined in detail and the effects of operating conditions on volumetric efficiency are presented. The effect of inlet valve timing on delivery manifold pressure fluctuations is also discussed.

Transfemoral Placement of the Left Ventricular Assist Device “Hemopump” During Mechanical Resuscitation

The Hemopump is a new left-ventricular assist device (21 F diameter), which provides up to 3.5 L/min output after placement in the left ventricle via the femoral artery. We describe the first case in which the device was inserted during resuscitation. The patient developed untreatable sustained ventricular tachycardias/fibrillation 40 hours after coronary artery bypass grafting. After prolonged mechanical resuscitation (about 3 hours) as a last resort the Hemopump was inserted and rhythm and hemodynamics stabilized. In the following hours a decrease in aortic pressure pulsatility indicated, effective left ventricular support when the Hemopump was running. For short periods the patient had nonpulsatile aortic pressure wave forms, implying complete pump dependence. In this situation cardiac output was about 3.0 L/min, mean aortic pressure reached nearly 50 mmHg using high dosage of catecholamines. The patient remained pump-dependent and died due to untreatable ventricular fibrillation. There was no significant hemolysis during the 20 hours the Hemopump was running. Autopsy revealed no signs of thrombembolism, but intimal lesions of the A. iliaca and of the abdominal aorta with subsequent thrombus formation were demonstrated. In view of the experimentally proven benefit in cardiogenic shock and problems and risks caused by the insertion, future indications for clinical use of this new device are discussed.

Two-dimensional analysis of beat wave current drive with intense microwave pulses

Current drive in tokamak plasmas by a beat wave is considered in two-dimensional (2-D) geometry. The beat wave is excited by the non-linear interaction of two intense microwave pulses (free electron lasers) in the plasma. The three-wave non-linear interaction equations in steady state are solved numerically. The 2-D toroidal effect and the effect of finite spatial width of the pump microwave pulses are taken into account for the excitation of the beat mode. To illustrate the principle, two types of tokamak are considered: one is small, such as, typically, the Microwave Tokamak Experiment (MTX), and the other one is larger, such as the Joint European Torus (JET). In both cases, it is found that good beat wave coupling exists for a Langmuir beat wave with a phase velocity of around 2.0 to 4.0 times the thermal velocity of the electrons. The fraction of total input power of the right circularly polarized pump waves deposited in the beat mode can be as high as 29% in JET and 32% in MTX. In these cases, there is almost complete pump depletion of the higher frequency pump microwave. It is also found that, for the same input parameters, left circularly polarized pump waves are less efficient than right circularly polarized pump waves for depositing power in the beat mode.

Design of an ultrahigh-vacuum specimen environment for high-resolution transmission electron microscopy

A JEOL 200CX high-resolution transmission electron microscope with point-to-point resolution of 2.5 Å has been modified to achieve an ultrahigh-vacuum specimen environment (∼10−9τ). In situ heating and evaporation are provided in the specimen viewing position, where high resolution can be maintained at temperatures exceeding 600 °C. Our design employs complete differential pumping of the specimen chamber and the use of a He-cooled cyroshield at the specimen for best vacuum attainment. Our design philosophy permits the instruments to be used for a wide variety of in situ experiments, including low-pressure (&amp;lt;10−1τ) gas reaction.

Unsteady compressible two-phase flow model for predicting cyclic heat pump performance and a comparison with experimental data

A dynamic model of vapour compression heat pumps is presented. Due to the importance of thermal expansion and compressibility effects, a detailed mathematical treatment of the condenser, evaporator and accumulator is given. Brief descriptions of the modelling techniques used for the remaining heat pump components and the solution methodology employed in the complete heat pump model are presented. Lumped-parameter models were developed for the expansion device, natural-gas-fueled internal combustion engine and compressor (open and hermetic). Inclusion of an appropriate void fraction model was found to be essential in determining the spatial refrigerant mass distribution, therefore a discussion pertaining to this model is also given. Simulations results and experimental data are favourably compared for transient operation of a hermetic water-to-water heat pump and an air-to-air system with an open compressor. The spatial variations of temperature, enthalpy, mass flow rate and density are predicted at each point in time for the two heat exchangers. The refrigerant pressures in the condenser and evaporator are determined such that the boundary conditions for the governing set of parabolic partial differential equations are satisfied. The summary provides a list of on-going work in the area of heat pump simulation and applications.

Performance Optimization of Induction Motor-Pump System Using Photovoltaic Energy Source

The optimization of a photovoltaic pumping system based on an induction motor driven pump that is powered by a solar array is presented in this paper. The motor-pump subsystem is analyzed from the point of view of optimizing the power requirement of the induction motor, which has led to an optimum u-f relationship useful in controlling the motor. The complete pumping system is implemented using a dc-dc converter, a three-phase inverter, and an induction motor-pump set. The dc-dc converter is used as a power conditioner and its duty cycle is controlled so as to match the load to the array. A microprocessor-based controller is used to carry out the load-matching.

Charts for water hammer in high head pump discharge lines resulting from pump failure and check valve closure

Maximum pressure head drops and rises resulting from pump failure and subsequent check valve closure are calculated and plotted for a simple pump discharge line at pump end, midpoint, and three-quarter point. Basic parameters such as pipeline constant, pipe wall friction, complete pump characteristics, and pump inertia constant are accounted for in the analyses. Computer studies indicate that pipe friction, pipeline constant, and pump inertia have a major effect on pressure head drops and rises.Studies indicate further that whereas for large pump inertia the pressure head rise or drop at the midpoint is only moderately larger than one-half of the rise or drop at pump end, for small pump inertia this difference is much greater. For very small pump inertia, the pressure head drop or rise at midpoint approaches the values at pump end. This increase in pressure head drop and rise for very small pump inertia is even more pronounced at the three-quarter point.

Charts for water hammer in low head pump discharge lines resulting from water column separation and check valve closure

Maximum pressure head rises resulting from water column separation and check valve closure are calculated and plotted for a simple low head pump discharge line with one well-defined high point. Basic parameters such as pipeline constant, pipe wall friction, complete pump characteristics, pump inertia constant, and the relative location of the high point are accounted for in the analyses. The results of this paper can be used to determine (a) when water column separation is expected, (b) how to avoid water column separation, and (c) the necessary wall thickness in cases where no protection against water column separation is provided. Computer studies indicate that both the vertical and horizontal location of the high point as well as the pipe friction, the pipeline constant, and the pump inertia have a major effect on pressure head rises. Water column separation does not always constitute a danger to the pipeline. Key words: waterhammer, water column separation, check valve closure, pressure rise, pump discharge line, chart.

Optimal Design of Branched Water Supply Networks

A rational procedure for the optimization of branched water supply networks is developed in closed form. Two case studies are presented to illustrate the procedure for the optimal design of complete gravity systems and direct pumping systems.

Intracellular Na+ and Ca2+ in leech Retzius neurones during inhibition of the Na+-K+ pump.

The intracellular Na activity, aNai, and the intracellular Ca activity, aCai, were measured with double-barrelled neutral carrier Na+- and Ca2+-sensitive microelectrodes in Retzius neurones in the central nervous system of the leech Hirudo medicinalis. The aNai was measured to be 8.0 mM (corrected for Ca interference), which corresponds to a cytoplasmic Na+ concentration of 10.7 mM, assuming a Na activity coefficient of 0.75. The calculated Na+ equilibrium potential was 59 mV, giving a total Na+ electrochemical gradient of approximately 102 mV. The aCai was found to range between 1 and 5 X 10(-7) M, from which a Ca2+ equilibrium potential near + 120 mV was estimated. When the Na+-K+ pump was inhibited by lowering the external K+ concentration or by adding the glycoside ouabain (5 X 10(-4) M), the aNai reversibly increased severalfold. When aNai increased to high levels following complete pump inhibition, the aCai increased above 10(-6) M, and the membrane input resistance decreased. After removal of ouabain, aNai, aCai and the membrane resistance recovered within 30 min after a delay of 20-40 min. Our results suggest that a large increase of aNai produces a rise in aCai, possibly by means of a Na+-Ca2+ exchange across the cell membrane. The elevation of the aCai may be responsible for the decrease in membrane resistance, and may also be related to the uncoupling of the paired Retzius neurones observed in the presence of Na+-K+ pump inhibitors.

Mechanical vacuum pumping equipment for applications involving corrosive and aggressive materials

In chemical environments such as those encountered in the semiconductor industry it is important to specify a complete pumping system including pumps, accessories, oils, and an operating procedure. The paper discusses certain features of the pump design that are important in ensuring reliability when pumping aggressive materials. Further the accessories designed to augment the performance of the pump in aggressive situations are discussed with specific data on their performance under controlled conditions. Special attention is given to a range of oils and oil filtration methods, as in most cases it is the results of oil degradation and contamination that cause operating difficulties in aggressive atmospheres.

Studies, testing, and development of a line of brine recirculating pumps for sea water desalination installations

The very special running conditions of Brine recirculation pumps coming from the nature and the characteristics of the fluid pumped, of its temperature, of the large range in capacity and low suction head are doing that these pumps are submitted to very hard conditions more than others. The development programme of a complete pumping range facing to the present needs involved in the MSF desalination plants has been realized with the following way : • Design and realization of a model test of the hydraulic part, • Research platform tests for checking and increasing of hydraulic performance especially for cavitation (with visualization) • Design and realization of one pump prototype for 6, 000m 3/day MSF unit ( 1.6-Mgd) • Endurance test on loop simulating in live-size the last stage of flash distillation like for hydraulic than for physico-chemic. These tests have been realized in campaign of 1,000 hours with dismentling and examination of all parts at the end of each campaign. 4,000 running hours have been carried out in 1980 under harder conditions during the last campaign, • Designs of pumps for MSF industrial plants of 10,000 and 20,000 m 3/day (3 and 6-Mgd). The paper exposes the results of the different steps of designs and tests insisting more particularly upon the materials reliability against both wearing and corrosion.