Low Suction Pressure Research Articles

Performance of a single-stage Linde-Hampson refrigerator operating with binary refrigerants at the temperature level of −60 °C

The optimization of the performance of a single-stage Linde-Hampson refrigerator (LHR) operating with six different binary refrigerants (R23/R134a, R23/R227ea, R23/R236ea, R170/R290, R170/R600a and R170/R600) with ozone depletion potentials (ODPs) of zero was conducted using a new approach at the temperature level of −60 °C. Among these binary refrigerants, the 0.55 and the 0.6 mole fractions of R23 for R23/R236ea are the most prospective nonflammable ones for the medium and low suction pressure compressors, respectively. For these two kinds of compressors, the 0.6 and the 0.65 mole fractions of R170 for R170/R600, respectively, are the most prospective binary refrigerants with low global warming potentials (GWPs). The results of optimization of pressure levels indicate that the optimum low pressure value for coefficients of performance (COP) is achieved when the minimum temperature differences occur at both the hot and the cold ends of the recuperator at a specified composition and pressure ratio. Two useful new parameters, the entropy production per unit heat recuperated and the ratio of heat recuperating capacity to the power consumption of the compression, were introduced to analyze the exergy loss ratio in the recuperator. The new approach employed in this paper also suggests a promising application even to the optimization of the performance with multi-component refrigerants.

An easy-to-make suction drain system

Multiple holes are made in the distal part of a feeding tube. The proximal end of the feeding tube is then connected to the syringe. The drain is put in place and secured. The fluid is first drained out manually. Then the needle cover of the syringe is put as a stopper between the end of the piston and the end of the body of the syringe in order to maintain the negative suction in the syringe. The system is secured by an adhesive tape around the piston and the needle cover. A piece of gauze can be used to wrap around the needle cover to make the systemmore stable. The suction pressure can easily be adjusted in our system. If a lower suction pressure is required, a small amount of air is aspirated into the syringe and then the syringe is fixed to the tube again. The system can be left in place for several days as a continuous suction drain system and it is very easy to monitor the content and the quantity of the fluid in the syringe (see Fig. 1).

Low-pressure continuous suction of bile and pancreatic juice from the hepatic duct and jejunal limb after major hepatectomy with pancreatoduodenectomy

We describe an effective technique for the low-pressure continuous suction of bile and pancreatic juice from the hepatic duct and jejunal limb after major hepatectomy with pancreatoduodenectomy (PD). After hepatectomy and PD, reconstruction is performed by a modification of Child's method. A pancreaticojejunostomy is completed with interrupted sutures between the pancreatic duct and mucosa, without inserting a stent. During hepaticojejunostomy, a 10-F silicone drain with side channels (Blake Silicone Drain; Ethicon, Somerville, NJ, USA) is placed within the hepatic duct via the stump of the jejunal limb to drain bile and pancreatic juice. The drain is connected to a continuous suction device and low suction pressure is started. We found that the low-pressure continuous suction of bile and pancreatic juice from the hepatic duct and jejunal limb was very effective after major hepatectomy with PD.

Suppression Effect of Upstream Installed Ring-Shaped Obstacle Plate on Cavitation Surge in Pump Inducers

The attachment of an inducer upstream of a main impeller is a powerful method to improve the suction performance. It is known, however, that the cavitation surge oscillation, which is focused in the present paper, occurs under the operation condition with partial flow rate and low suction pressure. The attempts to suppress the cavitation surge have been made by installing a ring-shaped obstacle plate just upstream of inducer. The ring-shaped inlet plates with various blockage rates of 14%, 27% and 39% have been tested to examine the effect of blockage rates on the suppression of cavitation surge for two kinds of inducers having two blades with the solidity of 2.0 and the different blade angles of 8° and 14° at the blade tip. In the present paper, the changes of the onset region of cavitation surge are clarified and the mechanism of cavitation surge suppression is discussed with the measured casing wall pressure distribution and inlet velocity distribution.

Negative pressure therapy is effective to manage a variety of wounds in infants and children

Negative pressure therapy (NPT) has been accepted as a valuable adjunct for wound closure in adults; however, reports on its effectiveness in young children and infants, including neonates, are limited. A retrospective chart review was conducted on children treated with NPT at a single institution between January 2003 and December 2005. Wound volumetric measurements were calculated at the start and end of therapy. Sixty-eight patients with 82 wounds were identified. The mean age was 8.5 years (range 7 days-18 years). Twenty patients (29%) were 2 years of age or younger, including eight neonates. Wound types included: pressure ulcers (n=13), extremity wounds (n=18), dehisced surgical wounds (n=19), open sternal wounds (n=10), wounds with fistulas (n=3), and complex abdominal wall defects (n=6). Low suction pressures (<100 mmHg) were generally used in children younger than 4 years of age. Following NPT, 93% of wounds decreased in volume. The average wound volume decrease was 80% (p<0.01, n=56). NPT can be effectively used to manage a variety of wounds in children and neonates. No major complications were identified in our retrospective review. Prospective studies are required to better refine the use of this technology in children.

Water retention of nonwoven polyester geotextiles

Planar polymeric geotextile materials are increasingly used in geotechnical and geoenvironmental engineering applications to perform various functions such as filtration, drainage and reinforcement. In most cases, they are placed above the groundwater table where soil and geotextiles pores are filled with water and air (i.e. under unsaturated conditions). In this respect, the development of the geotextile water-retention curves is of great importance to model the transient water flow in earthen systems containing geotextiles where unsaturated conditions may prevail. This paper, presents the results of a study on the cross-plane and in-plane water-retention characteristics of two nonwoven, polyester geotextiles. The geotextiles’ cross plane water-retention data demonstrated their hydrophobic nature with both specimens being essentially non-conductive to water beyond suction heads of 0.2–0.3 kPa. Pore size and porosity seemed to have a controlling effect on both the desaturation and resaturation processes. The geotextile with the larger apparent opening size and porosity de-saturated at very low suction pressure (0.4 kPa), whereas a slightly higher suction (0.9 kPa) was needed to de-saturate the geotextile with smaller apparent opening size and porosity. Both specimens exhibited significant hysteresis in their water-retention function, such that at a given suction a geotextile contained more water when drying than when wetting. The in-plane water retention of drying geotextiles indicates that both geotextile specimens absorbed no water at suctions greater than zero; thus the water retention of a dry specimen in the in-plane direction is effectively equal to zero. This implies that the geotextiles used in the present study were more hydrophobic in the in-plane than the cross-plane direction during wetting.

Suppression Effect of Cavitation Surge of Pump Inducer by Installing Ring-Shaped Obstacle Plate Upstream of Inducer

The attachment of an inducer upstream of the main impeller is a powerful method to improve the cavitation performance. It is known, however, that the cavitation surge oscillation, which is focused in the present paper, occurs under operation condition of partial flow rate and low suction pressure. The attempts to suppress the cavitation surge were made by installing a ring-shaped obstacle plate just upstream of inducer. The ring-shaped inlet plates with various blockage rates of 14%, 27% and 39% were tested to examine the effect of blockage rates on the suppression of cavitation surge for two kinds of inducers having two blades with the solidity of 2.0 and the different blade angle of 14° and 8°at the blade tip. In the present paper, the changes of the onset region of cavitation surge are clarified and the mechanism of cavitation surge suppression is discussed with casing wall pressure distribution and inlet velocity distribution.

A novel application of a submerged nanofiltration membrane bioreactor (NF MBR) for wastewater treatment

Nanofiltration (NF) membrane technology has made rapid progress and then extended its application fields. It has obtained in particular the good results in the removal of organic and inorganic matters or microbes in the water and wastewater. To investigate the applicability and characteristics of NF membrane, the membrane bioreactor (MBR) using the cellulose acetate NF membrane was performed to treat synthetic wastewater. A hollow-fiber-type cellulose acetate membrane was chosen to get enough water productivity regardless of its biodegradability. As a result of the experiments, enough water productivity was obtained for 60 days without fatal fouling and membrane cleaning. This raised the applicability of cellulose acetate membrane to the MBR system. Electrolytes were not accumulated in the bioreactor, as its rejection was also low. This enabled the NF MBR to be operated under a low suction pressure and prevented from inhibition against microorganisms, whose activity might be deteriorated by high salt concentration. Nitrification and denitrification happened simultaneously and this might be achieved by the module configuration. The phosphorus was not removed with the loose NF membrane. According to AFM investigation, the cellulose acetate membrane after 71 days has larger voids because of the biodegradation.

논문 : 옆미끄럼이 있는 삼각 날개 / LEX 형상의 와류와 공력 특성

The vortex flow and aerodynamic load characteristics of a sweep delta wing with the leading edge extension in sideslip condition is investigated experimentally. The freestream velocity is 40 m/sec, which corresponds to a Reynolds number per meter of 1.76X based on the wing root chord. The angles of attack range from to 28{^{\circ}}, and the sideslip angles treated are 0{^{\circ}}, -10{^{\circ}}, 20{^{\circ}}. The LEX vortex of the leeward side. The LEX and wing vortics coalesce to to become a concentrated strong vortex or to break down at down at downstream position. Due to the interation of the LEX and wing vortices, a high suction pressure is maintained on the windward wing surface, and a low suction pressure is formed on the leeward wing surface.ﾖ⨀

Helical liquid ring compressor for a steam compression heat pump: I. Concept and basic running characteristics

The liquid ring compressor (LRC) is a compressor suitable for a heat pump which uses water as a working fluid. The LRC has several features: (1) large suction speed; (2) low discharge temperature realized by the ring liquid; and (3) simple structure. However, in order to enlarge the working temperature region of such heat pumps toward lower temperature levels, it is necessary to improve the volumetric efficiency of the LRC, especially in the low suction pressure region. Therefore, a helical liquid ring compressor (HLRC) which has helical blades has been newly designed, as one of the attempts to obtain a higher volumetric efficiency. The HLRC is able to separate a suction space from a compression space along the axis and improve the volumetric efficiency. An experimental test has verified that the suction/compression mechanism of the HLRC functions as expected. © 2000 Scripta Technica, Heat Trans Asian Res, 29(8): 660–673, 2000

Hydraulic conductivity and pore-size distribution in small microcosms with and without enchytraeids (Oligochaeta)

Enchytraeids can influence pore structure by enlargement of pores, reduction of pore-size and formation of new pores. The distribution of enchytraeids through soil is strongly related to the placement of plant residues which is, therefore, expected to influence their effect on porosity and pore-size distribution. Fifteen cm soil columns with a bulk density of ca. 1.4 g/cm 3 were built using 3 metal rings each 5 cm high. Two types of columns were created: buried litter (BL) with organic matter mixed through the whole column and surface litter (SL), where the litter was added onto the surface of the column. To half of the columns of each treatment 45 enchytraeids were added. Saturated hydraulic conductivity was determined at time 0 and then after 4, 8 and 12 weeks. After the hydraulic conductivity measurements, the columns were separated into 3 depths and soil moisture retention was measured at a range of low suction pressures (0.5–20 kPa). Hydraulic conductivity decreased with time in the BL columns. At each time interval, K sat was higher in the BL columns containing enchytraeids compared to columns without enchytraeids. Presence and distribution of organic matter, the number of enchytraeids present and the duration of the experiment, influenced the impact of enchytraeids on hydraulic conductivity. Frequent ingestion and egestion of soil reduced its stability, especially in the SL columns, thereby decreasing pore size and continuity.

Helical Liquid Ring Compressor for a Steam Compression Heat Pump. 1st Report. Concept and Basic Running Characteristic.

The liquid ring compressor (LRC) is one of the compressors suitable for the heat pumps which use water as a working fluid. LRC has several features : 1) large suction speed, 2) low discharge temperature realized by the ring liquid, 3) simple structure. However, in order to enlarge the working temperature region of such heat pumps towards lower temperature level, it is necessary to improve the volumetric efficiency of LRC, especially at a low suction pressure region. Therefore a helical liquid ring compressor (HLRC) which has helical blades has been newly designed, as one of the attempts to obtain a higher volumetric efficiency. The HLRC is able to separate a suction space from a compression space along the axis and improve the volumetric efficiency. A test running has verified that the suction/compression mechanism of the HLRC functions as expected.

Pressures on surface-mounted prisms: The effects of incident turbulence

This paper discusses the effect of small-scale turbulence on the pressures observed on surface-mounted prisms placed in a variety of turbulent boundary layers. The effects of turbulence intensity and prism geometry are discussed in detail for oblique angles of attack with emphasis on observations on the top surface near the upstream corner and along its leading edges. In order to achieve a better simulation of the lateral turbulence intensity and the small-scale turbulence, small spires are placed directly upstream of the model location. Model/full scale comparison of the mean and fluctuating pressure coefficients are made to evaluate the effect of the spires on these coefficients in comparison with the conventional spire-roughness simulation method. Two specific situations are discussed with emphasis on the very low suction pressures usually encountered near the leading prism edges and under the corner vortices.

Morphology, Texture, and Microstructure of Halloysitic Soil Clays as Related to Weathering and Exchangeable Cation

AbstractThis paper aims at characterizing the morphology, texture, and microstructure of three hydrated kaolin rich clays (f &lt; 0.2 μm) from volcanic soils. These clays represent a weathering sequence in which CEC, halloysite content with respect to kaolinite, as well as smectite content in the halloysite-smectite mixed-layer clays decrease with increased weathering. The clay samples were made homoionic (K+ or Mg2+) and hydrated under a low suction pressure (3.2 kPa). After replacing water by a resin, ultrathin sections were cut and examined by TEM. Particle shape varies with increased weathering, as follows: spheroids → tubes → platelets. Higher aggregation and dispersion are observed by TEM after Mg2+ and K+ saturation, respectively, at two levels of the clay-water system organization: intraparticle and interparticle. The microstructure variations induced by the nature of the exchangeable cation become less pronounced with decreasing layer charge of the 2:1 layers. They are thus related here to the presence of smectite layers localized in the halloysite habitus, mostly at the particle periphery. These results show that small amounts of smectite largely affect the organization of clays rich in kaolins at a high water content, and that K+ behaves here as a dispersing ion.

Determining the Most Profitable Gas Injection Pressure for a Gas Lift Installation (includes associated papers 13539 and 13546 )

Gas injection pressure has a very decided effect on the efficiency and operation of a continuous flow gas lift well. Selection of a gas injection pressure that is too high can result in needless investment in compression and other equipment, whereas pressures that are too low can cause inefficient gas lift operations and failure to produce a well's full potential. This paper discusses the effect of various producing parameters on the selection of gas injection pressure and describes techniques for predicting and evaluating these effects on a specific gas lift installation to determine the most profitable operating system.

223 NONNUTRITIVE SUCKING(NNS) ENHANCES MATURATION OF THE SUCKING REFLEX IN PREMATURE INFANTS

Coordinated sucking during feeding is rarely achieved until 33 -34 wks. gestation. To define sucking patterns after birth & to determine the influence of pacifier stimulation (NNS) during gavage(NG) feeding, 20 medically stable, NG fed AGA infants (mean gest. age(GA) 32 wks.(range 28-34) were studied. Infants matched for birthwt. & GA were randomized into 2 groups. NNS received a pacifier prior to and during every NG feeding, the control received no pacifier. Intraoral negative(suction) pressure and suck ing patterns were recorded weekly during NG feedings. Both groups at 30-33 wks. gest. had low suction pressure(35-65mmHg); after 33 wks., intraoral pressure increased and sucks were organized into repetitive bursts(>3 rapidly consecutive sucks) with fewer sporadic sucks. However, the NNS group showed greater suction pressures(p<.05) from 34 wks.(89vs.62mmHg) to 39 wks.(120vs.73mmHg). In both groups, burst frequency increased from 7 to 12/2min; however, sucks/burst were greater in NNS(p<.05) from 34wk(8vs5/burst through 39wk(12vs7/burst) with fewer sporadic sucks (avg. 2.5vs. 7.5/2 min, p<.05). Finally, the NNS completed their first bottle feeding more rapidly(6.4±2.1 vs10.4±4.3min/oz avg±SD, p<.05) and made an earlier transition to total PO feeding(10±2.7 vs. 16±6.8 days, p<.02). Conclusion: Following birth, the sucking pattern in prematures is characterized by an increase in intraoral negative pressure and a transition from sporadic sucking to organized bursts; NNS opportunities significantly enhance this pattern and also facilitate an easier transition to bottle feedings.

Vapour pumping groups

Design features. The vapour booster was introduced in the early 1960s. It is part diffusion pump and part ejector. A typical design is shown in Figure 1. The vertical jet operates in the same way as a diffusion pump, the operation of which is described later, and the horizontal jet is the ejector. At low suction pressures the oil vapour jet stream emerges from the ejector at a wide angle and throttling would occur if the oil vapour were not condensed. When the suction pressure increases, the angle of the vapour jet stream is reduced until when the maximum pumping throughput is reached the jet only impinges near the smallest diameter of the horizontal cone.

Behaviour of Phytophthora cinnamomi rands in different soils and water regimes

The effect of different soils, nutrient states and water regimes on the growth, sporulation and lysis of mycelial inocula of Phytophthora cinnamomi has been examined. It has been observed that the requirements for chlamydospore and sporangium production in soils are relatively non-specific with respect to soil type, pH, percentage organic matter and the presence or absence of an additional food source. In contrast to chlamydospore production, however, production of sporangia in soil depends on a sufficiently low water suction pressure. In some soils a low percentage water content or a water content well below field capacity did not necessarily inhibit sporangium production. The pathogen was a good competitor for pieces of both fresh and rotting Castanea sativa radicles. Trichoderma viride appeared to play a significant role in soil by lysing hyphae of P. cinnamomi and inducing it to produce oospores.

Jet Pump Cavitation

Mixing-throat cavitation in a liquid jet pump results from high jet velocities, low suction (NPSH) pressure, or low discharge pressure. Incipient cavitation at the jet boundary has no effect on jet pump efficiency, but under severe conditions it spreads to the walls. A limiting flow condition results which is independent of discharge pressure. Efficiency deteriorates rapidly and the pump head-flow characteristics can no longer be predicted by conventional theory. Eight correlation parameters (1937–1968) and their interrelations are examined. A Cavitation Index σL is recommended for correlation of cavitation-limited flow results. Limiting flow data from 14 references on water, oils, and mercury, plus additional data on three water jet pumps are compared, showing that 11 sets of data on water, oils, and mercury can be represented by the single-number index σL, with a range of 0.8 to 1.67. Conventional jet pumps are described by σL = 1.0 to 1.4 and σL = 1.35 is recommended for conservative use. The limiting flow function Y (NPSH) is shown to be a useful tool in comparing cavitation response to design changes. System design to avoid cavitation is facilitated by a simple limiting flow equation, ML(R, σL, NPSH, Vn), and the equation is compared with recently published data. Cavitation can be avoided by reducing Vn, and R, or by raising suction port pressure. Flow passage contours, including nozzle-to-throat spacing, influence σL and the limiting flow ratio can also be improved by reducing σL (0.9 or less) through careful design. Systems handling high gas-solubility liquids can be improved by reducing gas content; fluid properties otherwise have little effect on this jet pump phenomenon.