Additional Head Loss Research Articles

Head Loss Characteristics of a Fibrous Bed in a PWR Chemical Environment

This paper examines the generation and effect of secondary materials created by chemical reactions between dislodged fiberglass insulation debris and simulated cooling system water that would be present within the containment of a pressurized water reactor following a loss-of-coolant accident (LOCA). Corrosion and subsequent precipitation of metals (aluminum, iron, zinc, and calcium) pose an important safety concern because the surface area of exposed metal inside containment represents a large potential source term of chemical debris products that may be capable of blocking the recirculation sump. The Advisory Committee on Reactor Safeguards (ACRS) cited the presence of gelatinous material recovered from the Three Mile Island containment pool after its 1979 accident and noted that the formation of adverse chemical products had not been previously examined under Generic Safety Issue 191 (GSI-191) research program.Based on small-scale tests, the following key issues related to corrosion and precipitation were investigated:1. Do credible corrosion mechanisms exist for leaching metal ions from bulk solid surfaces, and if so, what are the typical reaction rate constants?2. Can corrosion products accumulate in the containment pool water to the extent that they might precipitate as new chemical species at pH and temperature levels that are relevant to the LOCA accident sequence?3. How do chemical precipitants affect the head loss across an existing fibrous debris bed?Findings from these tests confirmed that corrosion of metal can occur and that artificially induced metallic precipitants can cause substantial additional head loss.

Overbank Flow in Symmetrically Narrowing Floodplains

Experimental data are presented for flow in compound channels with symmetrically narrowing floodplains. In such a geometry, the flow behavior presents similarities with the more complex flow in a meandering compound channel, yet without the curvature effects, because of mass transfers between the floodplains and the main channel, and secondary currents induced in the main channel. An estimation of the momentum transfer generated by the mass transfer is found significant compared to the frictional losses. It mainly depends on the geometrical parameters and is practically independent of the friction slope. Free-surface profile computations are performed with the exchange discharge model (EDM) to incorporate the effects of the momentum transfer in terms of an additional head loss. Agreement was found between measured and computed water surfaces, thus validating the EDM approach.

Cyclone as a precleaner to ESP ‐ a need for Indian coal based thermal power plants

Almost all coal based thermal power plants (CTPP) in India use electrostatic precipitator (ESP) for reduction of particulate matter (PM) in flue gas generated due to the combustion of Indian coal. This coal is characterized by high ash content, low calorific value and low sulfur content resulting in the generation of a very large amount of highly electrically‐resistive fly‐ash; thereby requiring a very large size ESP to minimize the fly‐ash emissions. However, the flue‐gas particle size distribution analysis showed that 60% of the particles are above 15 μm size, which can be conveniently removed using a low‐cost inertial separator such as a cyclone separator. It is proposed that a cyclone be used, as a pre‐cleaner to ESP so that the large size fraction of fly‐ash can be removed in the pre‐cleaning and the remaining flue‐gas entering the ESP will then contain only small size particles with low dust loading, thereby requiring a small ESP, and improving overall efficiency of dust removal. A low efficiency (65%), high throughput cyclone is considered for pre‐cleaning flue gas and the ESP is designed for removal of the remaining 35% fly‐ ash from the flue gas. It is observed that with 100% dust load, the ESP requires six fields per pass, whereas with cyclone as a pre‐cleaner, it requires only five fields per pass. Introducing cyclone into the flue gas path results in additional head loss, which needs to be overcome by providing additional power to induced draft (ID) fan. The permissible head loss due to the cyclone is estimated by comparing the power requirement in the bag filter control unit and cyclone‐ESP combined unit. It is estimated that a head loss of 10 cm of water can be permitted across the cyclone so as to design the same for 65% efficiency.

Head Loss IN TAPPING SLEEVES

When they install a branch from a water distribution main, water utility managers often debate the benefits of using a tap as opposed to shutting down the line to install a T-fitting. Part of the discussion centers around the fact that a tap, especially a size-on-size tap, will have a smaller orifice size than will a T-fitting. The concern is that this will lead to additional head loss and decreased capacity. For low-flow conditions, this loss in capacity is negligible, but during fire flows, this loss can become significant. This article reports the results of experiments that indicate the loss of carrying capacity in distribution systems is not significant as long as the orifice (tap cutout) is greater than 90% of the pipe size.

Momentum Transfer for Practical Flow Computation in Compound Channels

A new theoretical 1D model of compound channels flows-the exchange discharge model-is presented. The interactions between main channel and floodplains are taken into account as a momentum transfer proportional to the product of the velocity gradient at the interface by the mass discharge exchanged through this interface due to turbulence. Geometrical changes in cross sections are also modeled; they generate a similar momentum transfer, proportional to the actual mass transfer. Both effects are incorporated into the flow equations as an additional head loss. This make the formulation suitable for stage-discharge computation but also enables practical water-profile simulations. The model is tested successfully against available experimental data for (1) stage-discharge relations; and (2) water-profile computation applied to a field case.

98/00768 Process controls for the addition of a common FGD unit to a three-boiler, coke-fired utility plant

Suncor Inc.`s oil sands bitumen extraction and upgrading facilities in Fort McMurray, Alberta incorporate a utilities plant to provide electrical power, process steam and other utilities to the site. The utilities plan contains three Foster Wheeler downshot type coke-fired boilers, each capable of generating 790 psig, 750 F steam at a maximum rate of 825,000 lb/hr. These boilers burn an average of approximately 2,300 tons per day of coke. The coke, which is a byproduct of the bitumen upgrader, contains about 6% sulfur, which converts to mainly SO{sub 2} in the flue gas stream, with some SO{sub 3} as well. In order to reduce the sulfur emissions, a single common FGD unit has been installed to serve all three boilers. The boilers previously operated under forced draft mode. To accommodate the increased head requirement due to the addition of the FGD unit, an induced draft fan was added to each boiler. This was necessary to overcome the additional head loss caused by the JBR. Simultaneously, the three boilers were converted from forced draft to balanced draft operation. This had the side benefit of eliminating fugitive SO{sub 2} emissions inside the utilities building. All three ID fans are capable of variable more » speed operation.Two of the ID Fans are steam turbine driven for increased reliability. The third is electric motor driven to provide startup capability without steam supply. « less

Filtration of Non-ferrous Alloys in Gating Systems—an Investigation using a Hydraulic Analogy

The authors show how a simulation study, using a hydraulic analogy, of in-mould filtration of non-ferrous alloys has made it possible:To measure the additional head losses introduced by the placement of a filtration device in a filling system, and so work out the dimensions of a filter-insert chamber that introduces the smallest head losses, and b to test and compare filters of several types, such as extruded multicellular and ceramic foam filters, filters of sintered materials, and metal grids.The influence of the thickness of one type of filter and the fineness of another on the evolution of head losses were checked, together with the effect of clogging under well-defined modelling conditions.

Head loss through porous dikes

Porous dikes have been proposed for use in blocking access of fish to cooling water intakes in power plants using large cooling ponds for heat dissipation. Flow through such dikes is neither of the Darcy type nor quadratic, the friction factor depending on both the Reynolds number and material properties. Full-scale tests of the dike material proposed for the LaSalle County power plant confirmed the material-property and Reynolds-number dependencies reported in the literature and permitted calibration of the head-loss parameters for the prototype material under two placement configurations. Limited tests on dike clogging by surface debris permitted quantification of the additional head loss which clogging could cause. Key words: porous media, cooling ponds, dikes, scale model tests.

Flow in Collecting Conduits

Steady conduit flow with spatially increasing discharge is analysed by a hydraulic approach. Particular attention is paid to the effects of viscosity, wall roughness, additional head-loss due to the lateral inflow and the lateral inflow intensity on the flow characteristics in the manifold. The governing system of equations is presented for collecting manifolds consisting of a large number of laterals and solved for prismatic perforated collecting pipes. The comparison with observations indicates a good agreement. Finally, collecting conduits by which uniform lateral inflow is achieved are discussed.

L'écoulement dans des déversoirs latéraux

The main flow characteristics of side weirs are presented. In particular, the discussion accounts for the dynamic effects on the lateral outflow intensity, the additional head losses due to the lateral and the frictional effects on the free surface profile. The pseudouniform flow condition is considered in detail. Using typical nondimensional parameters, the general solution for the free surface profiles and the local discharge distribution is presented graphically. The computational procedure is illustrated by examples. Key words: hydraulics, side weir, open channel flow, water distribution, bifurcation.

Flow in Distribution Conduits

Steady conduit flow with spatially decreasing discharge is analysed by a hydraulic approach. Particular attention is paid to the effects of frictional slope, additional head-loss due to the single or manifold lateral, and the lateral outflow. The governing system of equations is then presented and solved for a common configuration. The results are compared to observations and several design recommendations are given.

Hydraulics of a distributing pipeline for spreading sludge and prediction of the distribution of the deposited soil fractions

1. In sluiced-in sludge as a distributed release, the distributing pipeline smooths out variations in the initial conditions and so their variation has practically no effect on the nature of distribution of the discharges and densities of the sludge issuing from the outlets. 2. In computations for the distributing pipeline, the additional head losses caused by the diversion of flow in the zone of the outlet are linked with the reconstruction of its kinematic structure and are proportional to variations in the shape of the velocity-distribution pattern. 3. The outlet size is selected so as to ensure the specified unit discharges per m of the sluiced-in front by using the proposed nomograph (Fig. 1). 4. A method is proposed for anengineering computation of the sluiced-in material, which is based on the law governing the nature of distribution of the fractions according to size onto the sluiced-in beach, as is also a formula for determining the coefficient of permeability of the sluiced-in ash-slag material.

An Experimental Study on Flat Disk Valves

This study has clarified the relations between the coefficient of additional head loss and valve lifts, and the relations between the pressure distribution and valve lifts. We assume that the total head (head of valve center) is equal to the summation of frictional loss of head in the parallel plate, velocity head at outlet and additional loss of head. For those purpose we have experimented on many valves under the condition of various valve lifts and three fluids; water, kerosene and motor oil. There three fluids are used to expand the equivalent Reynolds number range. The conclusion is that the coefficient of additional head loss in nearly zero but a positive value and gets larger in proportion as valve lifts increase at the same equivalent Reynolds number in the range of the experiments. The pressure distribution at the inlet of valves does not show the same tendency as each valve and it depends on valve lifts.

Siphon intakes at hydroelectric plants

1. Siphon intakes, introduced in the Soviet Union for the first time at the Kuban' hydroelectric plants, exhibit essential advantages over intakes equipped with quick-acting and emergency-maintenance gates, which recommends them for use at other divided-fall hydroelectric plants. 2. Experience with the siphon intakes at the Kuban' hydroelectric plants revealed their high reliability and ease of operation. 3. The main disadvantage of siphon intakes is the additional head loss, the value of which depends on the geometric dimensions of the siphon. For this reason the dimensions should be selected on the basis of technicaleconomic analyses. 4. The limiting value of the vacuum in the siphon should not exceed 6–7 mm of water; this condition rules out the use of siphon intakes in hydroelectric and pumped-storage plants with large fluctuations of the upstream water level.

Performance Characteristics and Cavitation Conditions of Three Axial-Flow Pump Impellers

In order to obtain wider and better performances of an axial-flow pump, the suction performances must be improved. Three impellers having different solidities and blade sections were tested to study the overall-and suction-performances and to observe the cavitation conditions inside the impellers. The additional head loss due to cavitation and the head rise ratio have been shown as the function of the product of cavitation parameter by solidity. The cavitation zone parameter has been illustrated as the pressure distribution on the blade surface. The suction performance may be estimated from it.

On the Relation between Cavitation Aspect in a Centrifugal Pump and Fall of Pump Head or Shaft Power Due to Cavitation : Studies of Cavitation Aspect and Suction Performance of Centrifugal Pumps, 3rd Report

In this report, the authers try to investigate the relation between the cavitation aspect in a centrifugal pump impeller and the fall of the pump head due to cavitation, by the method of dividing the decrease of the pump head due to cavitation into the decrease of the work-done of the impeller per unit weight for-rate of water and the increase of the head loss in the pump. First, the relations between the increase and decrease of the work-done of the impeller per unit weight flow-rate of waler and the region where the cavitation takes place are discussed and verified by the results of observation of the cavitation aspect. Next, the relations between the additional head loss due to cavitation and the cavitation aspect in the impeller are investigated. Further, the flow-rate where the reverse-flow occurs at the inlet of the impeller is investigated, using the nature that the additional head loss changes abruptly at this flow-rate.

The Use of Cone Valves in Distribution Systems

WATER works operators have long been familiar with the lengthy process of shutting a gate valve as far as possible and then repeating the procedure at the next valve up the line, to absorb some of the pressure differential. By working back and forth it is possible to shut off a large line with gate valves, but a great deal of time is consumed while the damage from a break continues to increase. The installation of rotary plug (cone) valves offers relief from these difficulties. A plug valve can be operated by one man to a full shut-off against a differential of the full designed pressure of the valve, and can be opened again without special measures for equalizing the pressure on both sides. Further comparison of plug and gate valves discloses the difference in friction between the two types. Plug valves present a smooth passage for the water, resulting in a friction loss of approximately half of that sustained in the use of gate valves. Thus, a direct saving in head loss is provided, or the size of a plug valve may be reduced without additional head loss. On the other side of the ledger are two important drawbacks: high cost and a complicated mechanism. Plug valves as usually designed cost several times the price of the ordinary doubledisc gate valve. The operating mechanism is rather complicated for the ordinary employee, and there are several adjustments that he would find difficult to accomplish without engineering advice. Plug valves can be built with single seats that are intended to give a tight shut-off with pressure in only one direction. Such a valve will serve to