bluuebunny/crossref_metadata_2025 huggingface dataset:
The time course of the effect of thyroid hormones upon basal oxygen consumption and plasma concentration of free fatty acid in rats
Authors: Myant N. B. , Witney Sarah
Published: December 2014

1. Basal O2 consumption and plasma free fatty acid (FFA) concentration were measured in normal and hypothyroid rats at various intervals after the initiation of a course of treatment with thyroid hormones.

2. A significant rise in basal O2 consumption was detectable in both groups of rats before there was any change in plasma FFA level.

3. It is concluded that the stimulatory effect of thyroid hormones on the basal O2 consumption of the whole animal is not mediated entirely by a rise in plasma FFA level.
The effect of 5‐hydroxytryptamine on the potassium exchange of human platelets
Authors: Born G. V. R.
Published: December 2014

1. The concentration of potassium in platelets freshly isolated from nine persons was 74 ± 4·8 μmole/1011 platelets (mean ±
S.E.M.).

2. The influx of potassium into platelets from citrated plasma at 37° C, estimated with the use of 42K, was 18·3 ± 1·6 n‐mole/sec. 1011 platelets.

3. When plasma contained 5‐hydroxytryptamine (5‐HT) at a concentration of about 5 μg/ml., the influx of potassium into platelets was increased for as long as they took up 5‐HT. This effect was absent when the concentration of 5‐HT was either lower (2 μg/ml.) or much higher (50 μg/ml.).

4. The concentration of 5‐HT in the platelets did not affect their potassium flux.
Membrane properties of the smooth muscle of guinea‐pig ureter
Authors: Kuriyama H. , Osa T. , Toida N.
Published: December 2014

1. The membrane properties of the guinea‐pig ureter were studied in physiological Krebs solution by intra‐ and extracellular stimulating methods.

2. The mean membrane potential was 50 mV. Action potentials triggered by external stimulation were composed of repetitive spikes and a plateau phase.

3. The effects of intracellular polarization on the membrane activity elicited by extracellular stimulation were observed. Anodal polarization enhanced the amplitude and the maximum rate of rise of the spike while cathodal polarization reduced them. The number of the spikes, the duration and amplitude of the plateau phase were not changed by polarization of any direction.

4. The spikes triggered by intracellular stimulation were mostly graded, but repetitive spikes sometimes continued even after cessation of the stimulation. The effective membrane resistance was 15‐23 MΩ and the time constant was 2‐3 msec.

5. Conduction velocity (V), chronaxie, time constant (τ) and space constant (λ) of the tissue were measured by extracellular stimulation. These values were as follows: V, 3‐6 cm/sec; chronaxie, 20‐40 msec; τ, 200‐300 msec; λ, 2·5‐3 mm. The conduction of excitation might be related to the cable properties of the tissue.

6. The relative refractory period measured by extracellular stimulation was as long as 30 sec. During the relative refractory period dissociation of the slow depolarization and the spikes was observed by successive stimuli.

7. The plateau phase was prolonged and the frequency of the spontaneous discharges was increased by treatment with Ba2+. Tetrodotoxin had no effect on spike activity nor on the plateau phase, but Mn2+ blocked the membrane activity.
Cardiac sympathetic adrenergic pathways in which synaptic transmission is blocked by atropine sulphate
Authors: Brown A. M.
Published: December 2014

1. Stimulation of the thoracic sympathetic nerve trunk caused a rise in arterial blood pressure and heart rate which was reduced but not abolished during the infusion of hexamethonium chloride, pentolinium tartrate, mecamylamine or tetraethylammonium chloride.

2. Preganglionic stimulation no longer elicited a synchronous sC elevation in the post‐ganglionic nerves. The persistent blood pressure and heart rate response was associated with an asynchronous discharge in these nerves.

3. Both the persistent response and the asynchronous discharge were abolished by the intravenous injection of atropine sulphate in doses of 30 μg/kg.

4. Atropine had no effect on spike amplitude or shape, conduction velocity or frequency response in either the pre‐ or post‐ganglionic nerve trunks. Nor did it affect the rise in blood pressure and heart rate evoked by stimulation of the post‐ganglionic cardiac sympathetic nerves.

5. It is concluded that atropine partially blocked synaptic transmission in cardiac sympathetic adrenergic pathways.
Determination of plasma kinin and kininogen levels in man
Authors: Brocklehurst W. E. , Zeitlin I. J.
Published: December 2014

1. A method for the estimation of free plasma kinin and kininogen is described, which is suitable for samples of blood taken in hospital.

2. The method permits the assay of very low levels of kinin and substantially eliminates errors due to the presence of amines and other interfering substances.

3. In normal subjects the mean value of free kinin is 2·8 ng (bradykinin equivalent)/ml. plasma, and 6·1 μg kininogen/ml.

4. In vasovagal fainting, carcinoid flush, and dumping syndrome, during the phase of peripheral vasodilatation, the free kinin exceeds 10 ng/ml., and is often in excess of 30 ng/ml.

5. Sudden release of free kinin is accompanied by a fall in kininogen level.
Effects of gestation and prenatal asphyxia on pulmonary surface properties of the foetal rabbit*
Authors: Humphreys P. W. , Strang L. B.
Published: December 2014

1. The pulmonary surface properties of foetal rabbits were studied after delivery by Caesarean section at 26‐30 days and after normal delivery at term (31 days).

2. Quasi‐static pressure—volume curves were defined for the lungs and the surface properties of the same lungs were further studied both by the bubble‐stability method and by means of a surface balance and trough. Results given by each method are compared and discussed.

3. At the 26th day of gestation the pulmonary surface properties, characteristic of the animal at term, were not yet present. These properties were first evident on the 28th day.

4. A period of 16 min intense prenatal asphyxia on the 28th day of gestation failed to produce a change in pulmonary surface properties.
The distribution of acetylcholine in normal and in regenerating nerves
Authors: Evans C. A. N. , Saunders N. R.
Published: December 2014

1. The distribution of acetylcholine (ACh) in various nerves which had been regenerating for different periods after crushing has been compared with that in uncrushed nerves.

2. Normal ventral roots from cats contained 78·1 ± 22·7 (
S.D.) μmole ACh/kg (blotted wet wt.); rabbit ventral roots contained 48·0 μmole/kg ± 19·0 (
S.D.) and rabbit sciatic nerves 16·6 ± 7·3 (
S.D.) μmole/kg. In the sciatic nerves the distal cm of 5 cm lengths taken from the thigh contained 30% more ACh than the most central cm portion. Possible explanations for this difference have been discussed.

3. After both sciatic nerves and ventral roots had been crushed, there was an initial build‐up (4 times control) of ACh central to the lesion and a decline (¼ control) distal to the lesion. These changes were maximum around 5 days after crushing. In sciatic nerves in which long periods of regeneration were investigated, the central build‐up fell off to 1½ times control by 25 days and the distal decline reversed to 2 times control in about 10 days. It then again decreased towards the control level by 25 days after crushing. These changes have been discussed in relation to the morphological changes which occur in a nerve following crushing.

4. A peak of ACh content moved distally along the nerve from the crushed region at a rate of 1·0‐1·5 mm/day. This was considered to represent an average rate of regeneration of the bulk of the axons. The amplitude of the peak declined progressively with time in the more distal parts of the nerve, probably because of dispersion as axons regenerated at different rates.
The sensitivity of the sodium pump to external sodium
Authors: Garrahan P. J. , Glynn I. M.
Published: December 2014

1. When red cells are incubated in potassium‐free solutions, ouabain‐sensitive sodium efflux is nearly absent with 5 m
M‐Na externally, but increases as the external sodium concentration is reduced from 5 m
M to zero. This increase suggests that the transport mechanism is very sensitive to small amounts of sodium at the outside surface of the cell membrane. Further evidence for such sensitivity has been obtained from the effects of external sodium on the relation between potassium influx and external potassium concentration.

2. With 5 m
M‐[K]o, potassium influx is rather insensitive to [Na]o but at low potassium concentrations even low levels of sodium inhibit.

3. With 140 m
M‐[Na]o the potassium influx curve is S‐shaped below 1 m
M [K]o. At much lower sodium concentrations, the S‐shaped region and the value of [K]o for which potassium influx is half‐maximal are both shifted progressively towards zero. At 10 μ
M‐[Na]o, potassium influx is half maximal at 0·14 m
M‐[K]o and the curve is close to a rectangular hyperbola down to 22 μ
M‐[K]o; there seems to be a trace of inflexion at about 15 μ
M‐[K]o.

4. When [Na]o is reduced from 5 m
M to zero, removal of the inhibitory effect of external sodium ions on sodium: potassium exchange could lead to an increase in sodium efflux into nominally potassium‐free solutions if these solutions did in fact contain traces of potassium. Such traces could arise by leakage from the cells, but, in a number of experiments, direct measurements showed that [K]o was too low to account in this way for all of the observed ouabain‐sensitive sodium efflux. A further reason for rejecting this explanation is that ouabain‐sensitive potassium loss into nominally (Na+K)‐free solutions was unaffected by adding 5 m
M‐Na. (A slight increase in ouabain‐resistant loss was observed.)

5. The ouabain‐sensitive efflux of sodium into (Na+K)‐free solutions therefore seems to represent a mode of behaviour of the transport mechanism distinct both from the sodium: potassium exchange that occurs under physiological conditions and from the sodium: sodium exchange that occurs in K‐free, Na‐rich media.
The relation between secretion of urate and p‐aminohippurate in the rabbit kidney
Authors: Møller Jesper V.
Published: December 2014

1. The renal excretion of urate in the rabbit was examined during infusion of other anions which are secreted by the kidney. A reduction of urate excretion occurred after administration of p‐aminohippurate (PAH) and Diodrast which was proportional to the secretory rate of these compounds. On the other hand, urate was a less efficient inhibitor of PAH secretion.

2. Stop‐flow experiments showed that tubular secretion of urate at maximal values for secretion of PAH and Diodrast was almost completely suppressed.

3. 2,4‐Dinitrophenol, fumarate, succinate, salicylate, and probenecid depressed the excretion of urate and PAH, but the tubular secretion of urate was apparently more depressed than that of PAH by these inhibitors.

4. It is concluded that a common transport system for urate and PAH is involved in the tubular secretion of urate and PAH in the rabbit. However, the affinity of urate for the transport system appears to be smaller than that of PAH.
Local and reflex factors affecting the distribution of the peripheral blood flow during arterial hypoxia in the rabbit
Authors: Chalmers J. P. , Korner P. I. , White S. W.
Published: December 2014

1. The effects of severe arterial hypoxia on the blood flow in the portal vein, and in kidney, muscle and skin beds have been determined in normal unanaesthetized rabbits, in animals without functioning autonomic effectors, and in rabbits with section of the carotid sinus and aortic nerves.

2. The resting blood flows in the above regions were not significantly different in the three groups.

3. The susceptibilities of the various beds to the local dilator effects of arterial hypoxia (assessed from the responses of animals without functioning autonomic effectors) were markedly different; vasodilatation was by far the greatest in the portal bed, followed in order by the renal, skin and muscle beds.

4. Section of the carotid sinus and aortic nerves completely abolished reflex activity, and the pattern of peripheral blood flow changes was similar to that of animals without functioning autonomic effectors. The findings suggest that the arterial chemoreceptors are the primary afferent source of reflex control of the peripheral circulation in arterial hypoxia.

5. In normal animals with intact reflexes there was sustained vasoconstriction throughout the treatment period in the portal and renal bed. The net vasomotor effects in muscle and limb skin were small owing to the operation of a number of factors, which opposed the effects of reflexly increased sympathetic nerve activity.
The responses of thalamic neurones to iontophoretically applied monoamines
Authors: Phillis J. W. , Tebēcis A. K.
Published: December 2014

1. The effects of noradrenaline (NA), adrenaline, dopamine (DA) 5‐hydroxytryptamine (5‐HT) and a number of related drugs were tested on the extracellularly recorded responses of neurones in the feline thalamus. Substances were applied iontophoretically and tested on synaptically, antidromically and chemically evoked neuronal activity.

2. NA, adrenaline, isoprenaline and 5‐HT had a variety of effects, depressing some cells, exciting others and not affecting the responses of a third group. DA depressed most of the cells tested; excitation was not observed with this compound.

3. The magnitude of depressant actions and their duration varied considerably. The more sensitive cells responded to extremely small amounts of catecholamine or 5‐HT and recovery often took several minutes. Recovery after DA was always rapid. Neurones in the dorsal thalamus were generally more susceptible to depression than those in the ventro‐basal complex.

4. Excitatory responses were most marked in the ventro‐basal complex of the thalamus. Desensitization occurred if NA or adrenaline was applied repeatedly and this tachyphylaxis lasted for several minutes. After desensitization to the excitatory effects, some of these cells were depressed by catecholamines. These findings suggest the presence of at least two types of membrane receptor.

5. β‐adrenergic antagonists (alderlin,
D‐INPEA and MJ 1999) and α‐antagonists (phentolamine, dibenzyline and chlorpromazine) had pronounced depressant actions on some thalamic neurones. With the exceptions of
D‐INPEA and MJ 1999 they also excited cells that were excited by the catecholamines. Alderlin and phentolamine had both excitatory and inhibitory effects on some cells.

6. The monoamine oxidase inhibitor, iproniazid, depressed neurones which were sensitive to NA depression. It did not appear to potentiate the effects of NA on most of the cells tested.

7. Reticular formation stimulation depressed some neurones in the thalamus and excited others. The depressant effects of NA and reticular formation stimulation were reduced or abolished by an intravenous injection of picrotoxin (1 mg/kg).

8. It is suggested that NA and 5‐HT may be inhibitory transmitters in the thalamus, released at the terminals of ascending pathways from the brain stem that have been defined by fluorescence microscopy. The excitatory actions of these compounds may also be related to a synaptic role.
Circulatory responses of supine subjects to the exposure of parts of the body below the xiphisternum to subatmospheric pressure
Authors: Ardill B. L. , Bannister R. G. , Fentem P. H. , Greenfield A. D. M.
Published: December 2014

1. Observations are reported on the effects of exposure of parts of the body below the level of the xiphisternum of supine subjects to a pressure 70 mm Hg below atmospheric for 1 min.

2. The stress on the circulation was greater than when parts below the iliac crests were similarly exposed. Heart rate increased by 15‐20 beats/min, there was a sustained fall in arterial blood pressure, and forearm blood flow fell profoundly and in some subjects was reduced to below 0·1 ml./100 ml. min.

3. In arms that were sympathectomized, or had received an intraarterial infusion of an adrenergic blocking drug, the fall in forearm blood flow was much less and could be related to the fall in arterial pressure.

4. When the suction was released there was a brief overshoot of arterial blood pressure and brief cardiac slowing. Forearm blood flow rose to reach a peak some 15 sec after the release.

5. In the sympathectomized forearm on release of suction there was an immediate rise in blood flow which was proportionately much greater than the rise in arterial blood pressure.

6. This rise was not due to circulating vasodilator substances or to the activity of cholinergic vasodilator nerves. The possibility that it was the result of a change in the tone of the resistance vessels occurring in response to the sudden change in transmural pressure is discussed.
Intracellular autogenetic and synergistic effects of muscular contraction on flexor motoneurones
Authors: Green D. G. , Kellerth J.-O.
Published: December 2014

1. Intracellular records have been taken from cat motoneurones innervating flexor muscles of the hind limb. Contractions of the ankle flexors tibialis anterior and extensor digitorum longus were elicited by stimulation of the peripheral end of the cut L 7 ventral root and the reflex effects of these contractions were recorded in silent and repetitively firing motoneurones.

2. Contraction usually produces a hyperpolarizing response inside flexor motoneurones. This hyperpolarization is tension‐sensitive in the sense that when, at constant muscle extension, the strength of the contraction is increased, the magnitude of the inhibitory response is augmented.

3. Increasing the resting length of the muscles, while using a stimulus of constant strength to the ventral root, causes this inhibitory response to increase in some cells. More often, however, the hyperpolarization caused by contraction is gradually reduced in duration and/or amplitude as the muscles are extended.

4. Even with the muscles slackened, so that they develop no tension at their ends, contraction usually produces prominent hyperpolarization of the motoneurones.

5. By passing polarizing currents or injecting chloride ions through the intracellular micro‐electrode, the hyperpolarizing potentials produced by contraction of the slack and extended muscles are shown to be, at least in part, genuinely post‐synaptic inhibitory events.

6. When the neurone is fired repetitively by injected current, the ‘silent period’ in contraction corresponds to the hyperpolarization of the post‐synaptic membrane.

7. Monosynaptic testing of the flexor motoneurone pool has been used to confirm the essential features of the intracellularly recorded activity.

8. Acutely spinalizing the animal increases the magnitude of the inhibitory responses caused by contraction.

9. Recordings from dorsal root fibres show that Golgi tendon organs of the ankle flexors are very sensitive to contraction and are indeed often activated by the internal forces developed in a contracting slack muscle.

10. A number of muscle spindles of the ankle flexors are activated by stimulation of the ventral root at a strength submaximal or just maximal for the α‐motor fibres, despite the simultaneous unloading effect of the contracting extrafusal fibres. This spindle activation, which occurs mainly during the phase of tension development in contraction, is favoured by an increased extension of the muscle. Attempts were made to establish whether it is due to α‐motor innervation of the receptors or to some mechanical interaction between the intra‐ and extrafusal muscle fibres.

11. The possible central and peripheral causes of the changes in motoneurone excitability produced by flexor muscle contraction are discussed. It is suggested that tendon organs of flexor muscles strongly inhibit flexor motoneurones and that α‐motor innervation of muscle spindles is likely to play a more prominent role in flexors than in extensor muscles.
Transport of potassium by the colon of normal and sodium‐depleted rats
Authors: Edmonds C. J.
Published: December 2014

1. Ascending and descending segments of colon of normal and Nadepleted rats were perfused with solutions of differing KCl concentration. Net K flux, electrical p.d. and, in some experiments, unidirectional K fluxes were measured.

2. Variation of luminal K concentration over the range 0‐40 m
M did not affect p.d. or K efflux rate.

3. K secretion rate fell about 30% when Na‐free choline chloride solution was perfused.

4. Net flux was a linear function of the luminal K concentration, and fell as the latter increased. Na depletion increased K secretion rate and passive permeability of the mucosa to K. Adrenalectomy had the reverse effect. The luminal K concentration, associated with zero net K flux was much greater than expected if the colonic mucosa behaved passively with respect to K.

5. Unidirectional fluxes determined when 5 m
M‐KCl was in the lumen showed that the ratio influx/efflux was much less than predicted by Ussing's flux ratio equation.

6. It was concluded that K influx was due to simple diffusion and K efflux to diffusion and active transport, both processes being increased by Na depletion.
The experimental induction of hypophosphataemia in goats using anion exchange columns
Authors: Symonds H. W. , Treacher R. J.
Published: December 2014

1. Inorganic phosphate was selectively removed from the circulating blood of five anaesthetized goats by means of columns of anion‐exchange resin. Concentrations of other ions were unaffected by the column.

2. Rates of inorganic phosphate extraction in excess of 5 m‐moles/hr caused a fall in plasma inorganic phosphate of up to 50% in 30 min.

3. In four of the goats the calculated inorganic phosphate mobilization rate rose sharply to a maximum between 5.8 and 12.7 m‐moles/hr and then fell progressively as more phosphate was removed.

4. During the course of the experiments a fall in blood pressure occurred, accompanied by a rise in blood glucose. The reasons for this are discussed.
High Efficiency SOFC Power Cycles With Indirect Natural Gas Reforming and CO2 Capture
Authors: Campanari Stefano , Gazzani Matteo
Published: December 2014

Driven by the search for the highest theoretical efficiency, several studies have investigated in the last years the adoption of fuel cells (FCs) in the field of power production from natural gas with CO2 capture. Most of the proposed power cycles rely on high temperature FCs, namely, solid oxide FCs (SOFCs) and molten carbonate FCs (MCFCs), based on the concept of hybrid FC plus gas turbine cycles. Accordingly, high temperature FCs are integrated with a simple or modified Brayton cycle. As far as SOFCs are concerned, CO2 can be separated downstream the FC via a range of available technologies, e.g., chemical or physical separation processes, oxy-combustion, and cryogenic methods. Following a literature review on promising plant configurations, this work investigates the potential of adopting an external natural gas conversion section with respect to the plant efficiency. As a reference plant, we considered a power cycle proposed by Adams and Barton (2010, “High-Efficiency Power Production From Natural Gas With Carbon Capture,” J. Power Sources, 195(7), pp. 1971–1983), whose performance is the highest found in literature for SOFC-based power cycles, with 82% LHV electrical efficiency. It is based on a prereforming concept where fuel is reformed ahead the SOFC, which thus works with a high hydrogen content fuel. After reproducing the power cycle with the ideal assumptions proposed by the original authors, as second step, the simulations were focused on revising the power cycle, implementing a complete set of assumptions about component losses and more conservative operating conditions about FC voltage, heat exchangers minimum temperature differences (which were previously neglected), maximum steam temperature (set according to heat recovery steam generator (HRSG) practice), turbomachinery efficiency, component pressure losses, and other adjustments. The simulation also required to design an appropriate heat exchangers network, which turned out to be very complex, instead of relying on the free allocation of heat transfer among all components. Considering the consequent modifications with respect to the original layout, the net electric efficiency changes to around 63% LHV with nearly complete (95%+) CO2 capture, a still remarkable but less attractive value. On the other hand, the power cycle requires a complicated and demanding heat exchangers network and heavily relies on the SOFC performances, not generating a positive power output from the gas turbine loop. Detailed results are presented in terms of energy and material balances of the proposed cycles. All simulations have been carried out with the proprietary code GS, developed by the GECOS group at Politecnico di Milano.
Unsteady Computational Fluid Dynamic Analysis of the Behavior of Guide Vane Trailing‐Edge Injection and Its Effects on Downstream Rotor Performance in a Francis Hydroturbine
Authors: Lewis Bryan J. , Cimbala John M.
Published: December 2014

A unique guide vane design, which includes trailing-edge jets, is presented for a mixed-flow Francis hydroturbine. The water injection causes a change in bulk flow direction at the inlet of the rotor. When properly tuned, altering the flow angle results in a significant improvement in turbine efficiency during off-design operation. Unsteady CFD simulations show nearly 1% improvement in overall turbine efficiency with the use of injection. This revolutionary concept also has the ability to reduce the intensity of the rotor–stator interactions (RSI) by compensating for the momentum deficit of the wicket gate wakes. This technology may be equally applied to other turbomachinery devices with problematic rotor–stator flow misalignments.
Synthesis of Spatial Mechanism UR-2SS for Path Generation
Authors: Chung Wen-Yeuan
Published: December 2014

This article presents a new spatial mechanism with single degree of freedom (DOF) for three-dimensional path generation. The path can be defined by prescribing at most seven precision points. The moving platform of the mechanism is supported by a U-R (universal-revolute) leg and two S–S (spherical–spherical) legs. The driving unit is the first axis of the universal pair. The U-R leg is synthesized first with the problem of order defects being considered. Precision points then lead to prescribed poses of the moving platform. Two S–S legs are then synthesized to meet these poses. This spatial mechanism with a given input is analogous to a planar kinematic chain so that all possible configurations of the spatial mechanism can be constructed. A strategy consisting of three stages for evaluating branch defects is developed with the aid of the characteristic of double configurations and the technique of coding three constituent four-bar linkages. Two numerical examples are presented to illustrate the design, the evaluation of defects, and the performance of the mechanism.
Uniform Equations in the Inlet and Exit Zones of Heavily Loaded Point and Line Elastohydrodynamically Lubricated Contacts Involved in Various Steady Motions
Authors: Kudish Ilya I.
Published: December 2014

Heavily loaded point elastohydrodynamically lubricated (EHL) contacts involved in steady purely transitional, skewed transitional, and transitional with spinning motions are considered. It is shown that in the central parts of the inlet and exit zones of such heavily loaded point EHL contacts the asymptotic equations governing the EHL problem along the lubricant flow streamlines for the above types of contact motions can be reduced to two sets of asymptotic equations: one in the inlet and one in the exit zones. The latter sets of equations are identical to the asymptotic equations describing lubrication process in the inlet and exit zones of the corresponding heavily loaded line EHL contact (Kudish, I. I., 2013, Elastohydrodynamic Lubrication for Line and Point Contacts: Asymptotic and Numerical Approaches, Chapman and Hall/CRC). For each specific motion of a point contact, a separate set of formulas for the lubrication film thickness is obtained. For different types of contact motions, these film thickness formulas differ significantly (Kudish, I. I., 2013, Elastohydrodynamic Lubrication for Line and Point Contacts: Asymptotic and Numerical Approaches, Chapman and Hall/CRC). For heavily loaded contacts, the discovered relationship between point and line EHL problems allows to apply to point contacts most of the results obtained for line contacts (Kudish, I. I., 2013, Elastohydrodynamic Lubrication for Line and Point Contacts: Asymptotic and Numerical Approaches, Chapman and Hall/CRC; Kudish, I. I., and Covitch, M. J., 2010, Modeling and Analytical Methods in Tribology, Chapman and Hall/CRC).
Refrigerated Railroad Car Design for Shipping Frozen Meat Using Alternative Refrigerants
Authors: Alkan Beyza , Celen Ali , Çebi Alican , Dalkilic Ahmet Selim , Wongwises Somchai
Published: December 2014

Refrigerated railroad cars, known as reefers, are railroad rolling stock designed to carry perishable freight at specific temperatures. They are insulated boxcars that keep the cargo at a regulated temperature. As soon as railroad cars had the capability to keep a load cold, the potential growth of the meat, dairy, fruit and brewery industries became nearly unlimited. In this paper, a cold-room system in a railroad car was investigated as a case study to illustrate the use of the sample model. The change of substitute refrigerants and insulation thickness of the cold rooms’ refrigeration system was also considered in the model. The coefficient of performance (COP), refrigerant flow rate and capacities of each component of the refrigeration system were calculated for the refrigerants R12, R22, R134a, R290, R410A, R430A, R431A, R436A, R507A, R600a as part of this analysis. As a result of the energy analyses, all of the substitute refrigerants have a slightly lower COP and require higher compressor work than R12 and R22 for a condensation temperature of 40°C. The frozen meats have an evaporation temperature of −25°C related to the preserved product in the case studies. Influences of the insulation thickness of the wall on evaporator capacity and outside temperature of various cities on the condenser are also studied.
Predictive Erosion Modeling in an ESP Pump
Authors: Pirouzpanah Sahand , Morrison Gerald L.
Published: December 2014

Electrical Submersible Pumps (ESPs) are widely used in upstream oil production. The presence of a low concentration solid phase, particle-laden flow, in the production fluid may cause severe damage in the internal sections of the pump which reduces its operating lifetime. To better understand the ESP pump’s endurance, an ESP-WJE1000, manufactured by Baker Hughes Company was studied numerically to determine the pump’s flow behavior at its best efficiency point. Computational Fluid Dynamics (CFD) analysis was conducted on two stages of the pump’s primary flow path employing Eulerian-Granular scheme in ANSYS-Fluent. The key parameters affecting the erosion phenomena within the pump such as turbulence kinetic energy, local sand concentration and near wall relative sand velocity were identified. The predictive erosion model applicable to pumps was developed by correlating the erosion key parameters with available experimental results.
Numerical Simulation of Condensation of Upward Flow in a Vertical Pipe
Authors: Qiu Guodong , Wu Zhiyong , Jiang Yiqiang , Li Shulei , Cai Weihua
Published: December 2014

A transient three-dimensional volume of fluid (VOF) simulation on condensation of upward flow of wet steam inside a 12 mm i.d. vertical pipe is presented. The effect of gravity and surface tension are taken into account. A uniform wall heat flux have been fixed as boundary conditions. The mass flux is m=130∼6000 kg m−2 s−1 and the turbulence inside the vapor phase and liquid phase have been handled by Reynolds Stress (RS) model. The vapor quality of fluid x=0∼0.4. The numerical simulation results show that in all the simulated conditions only the bubbly flow, slug flow, churn flow and annular flow are observed, in addition the results of flow pattern are in good agreement with the regime map from Hewitt and Roberts. The typical velocity field characteristic of each flow pattern and the effect of velocity field on heat transfer of condensation are analyzed. It can be found that only slug flow has an obvious local eddy around the slug gas in all simulated flow patterns. The trend of heat transfer coefficients rises throughout with the increase of vapor quality for all simulated conditions, which is good agreement with the correlation from Boyko and Kruzhilin.
Influence of a Stability Control Device on the Performance of a Cavitating Water Pump Inducer
Authors: Lundgreen R. , Maynes D. , Gorrell S. , Oliphant K.
Published: December 2014

An inducer performance has been explored with and without the implementation of a stability control device. Multiphase, time-accurate computational fluid dynamic simulations have been conducted at the design flow coefficient and at two low off-design flow coefficients. At the design flow coefficient, the inducer performance was similar with and without the stability control device. At low flow coefficients, the inducer without the stability control device exhibited significant cavitation instabilities, which led to high rotordynamic forces on the inducer blades. When the stability control device was incorporated into the inducer design, nearly all of the cavitation instabilities were suppressed at low flow coefficients and the rotordynamic forces were reduced by more than an order of magnitude. Stable operation at flow coefficients far below the design value leads to a significant increase in the suction performance of the inducer, allowing pumps to operate at lower inlet pressures.
Designing Wind Turbines for Areas With Low Wind Speeds
Authors: Mayeed Mohammed S. , Khalid Adeel
Published: December 2014

Today’s wind turbines are designed in a wide range of vertical and horizontal axis types. In this study, several wind turbines are designed for low wind speed areas around the world mainly for domestic energy consumption. The wind speed range of 4–12 mph is considered, which is selected based on the average wind speeds in the Atlanta, GA and surrounding areas. These areas have relatively low average wind speeds compared to various other parts of the United States. Wind energy has been identified as an important source of renewable energy. Traditionally wind energy utilization is limited to areas with higher wind speeds. In reality a lot of areas in the world including Atlanta, GA., have low average wind speeds and demand high energy consumption. In most cases, wind turbines are installed in remote offshore or away from habitat locations, causing heavy investment in installation and maintenance, and loss of energy transfer over long distances. Therefore, the main focus of this study is to extract wind energy domestically at low wind speeds. A few more advantages of small scale wind turbines include reduced visibility, less noise and reduced detrimental environmental effects such as killing of birds, when compared to traditional large turbines. With the latest development in wind turbine technology it is now possible to employ small scale wind turbines that have much smaller foot print and can generate enough energy for small businesses or residential applications. The low speed wind turbines are typically located near residential areas, and are much smaller in sizes compared to the large out of habitat wind turbines. In this study, several designs of wind turbines are modeled using SolidWorks. Virtual aerodynamic analysis is performed using SolidWorks Flow simulation software, and then optimization of the designs is performed based on maximizing the starting rotational torque and acceleration. From flow simulations, forces on the wind turbine blades and structures are calculated, and used in subsequent stress analysis to confirm structural integrity. Critical insight into the low wind speed turbine design is obtained using various configurations and the results are discussed. The study will help identify bottlenecks in the practical and effective utilization of low speed wind energy, and help devise possible remedial plans for the areas around the globe that get low average wind speeds.
Characterizing Jetting in an Acoustic Fluidized Bed Using X-Ray Computed Tomography
Authors: Escudero David R. , Heindel Theodore J.
Published: December 2014

Understanding the jetting phenomena near the gas distributor plate in a fluidized bed is important to gas-solids mixing, heat and mass transfer, and erosion on any bed internals, which can all affect the performance of the bed. Moreover, acoustic vibration in a fluidized bed can be used to enhance the fluidization quality of particulate matter. Characterizing the jetting structure using X-ray computed tomography in a 3D fluidized bed, with and without acoustic intervention, is completed in this study. A 10.2 cm ID fluidized bed filled with glass beads, with material density of 2500 kg/m3 and particles sizes ranging between 212–600 μm, is used in these experiments. X-ray computed tomography (CT) imaging is used to determine local time-average gas holdup. From this information, qualitative characteristics of the hydrodynamic structure of the multiphase flow system are determined. Local time-average gas holdup images of the fluidized bed under acoustic intervention at a high superficial gas velocity show that jets produced near the aeration plate merge with other jets at a higher axial position of the bed compared to the no acoustic condition. Acoustic fluidized beds also have a fewer number of active jets than the no acoustic fluidized bed, which allowed for a more homogeneous gas holdup region deep into the bed. Hence, the acoustic presence has a significant effect on the jetting phenomena near the distributor plate of the fluidized bed.
Numerical Prediction of Solid Particle Erosion for Elbows Mounted in Series
Authors: Felten Frederic N.
Published: December 2014

Erosive wear due to solid-particle impact is a complex phenomenon where different parameters are responsible for causing material removal from the metal surface. Some of the most critical parameters regarding the solid particles are the size, density, roundness, and volume concentration. The properties of the carrying fluid (density, dynamic viscosity, bulk modulus…), the geometry of the flow path (straight or deviated), and the surface material properties are also major contributors to the overall severity of the solid-particle erosion process. The intent of this paper is to focus on the impact of the flow path geometry on surface erosion for a specific carrier fluid, flow rate, sand type and sand-volume concentration. A numerical approach using the commercial CFD code FLUENT is applied to investigate the solid particle erosion in two 90° pipe elbows mounted in series. The distance between the two elbows is varied, as is the angle between them. A total of 16 cases are analyzed numerically. The relationships between the parameters pertinent to the two elbows and the erosion pattern, erosion intensity, and location of maximum erosion are presented. Prior to the analyses for the two elbows mounted in series, an in-depth validation effort for a single elbow geometry is undertaken to determine the appropriate mesh requirement, turbulence model, and to calibrate the inputs to the erosion model.
A Study of the Development of an Analytical Wall Function for LES
Authors: Amano R. S. , Hasegawa Takahiko , Shen Shaohua
Published: December 2014

In order to invent a new near-wall treatment for turbulence in Computational Fluid Dynamics (CFD) simulation, an Analytical Wall Function (AWF) has been studied and shown that it is possible to work accurately with Reynolds Averaged Navier-Stokes (RANS) Simulation even for complicated geometry such as impinging jet flow or separation and reattachment flow. One of the most common wall functions is the Standard Wall Function (SWF) which assumes log-law inside the boundary layer. However, there is a problem that SWF has been used for industrial applications even though it is difficult to analyze the turbulence phenomenon in a complicated geometry accurately because log-law is not applicable in that geometry. On the other hand, since AWF derives the boundary condition on the wall by integrating analytically the boundary layer equation in wall adjacent cells, it can analyze the turbulence accurately even in complicated geometry. AWF has an advantage over SWF from this point of view.

In this study, AWF was improved and optimized for Large Eddy Simulation (LES) by changing the way of modeling of eddy viscosity inside the boundary layer for steady state simulation to that for unsteady state simulation. This is because RANS is a steady state simulation; on the other hand, LES is unsteady state simulation, which is one of the largest differences between them. The accuracy of the new AWF for LES (LES-AWF) was validated by both of experimental results and CFD simulation results. Both of the experiment and CFD simulation are conducted in the wind tunnel.
Effect of Particle Size on Magnitude and Location of Maximum Erosion in S-Bend
Authors: Mazumder Quamrul H.
Published: December 2014

Solid particle erosion is a micromechanical process that is influenced by flow geometry, material of the impacting surface, impact angle, particle size and shape, particle velocity, flow condition and fluid properties. Among the various factors, particle size and velocity have been considered to be the most important parameters that cause erosion. Particle size and velocity are influenced by surrounding flow velocities and carrying fluid properties. Higher erosion rates have been observed in gas-solid flow in geometries where the flow direction changes rapidly, such as elbows, tees, valves, etc., due to local turbulence and unsteady flow behaviors. S-bend geometry is widely used in different fluid handling applications such as automotive, oil and gas, arteries and blood vessels. This paper presents the results of a Computational Fluid Dynamic (CFD) simulation of diluted gas-solid and liquid-solid flows through an S-Bend and the dynamic behavior of entrained solid particles in the flow. CFD analyses were performed at five different particle sizes ranging between 50 and 300 microns. Maximum erosive wear was observed at smaller particle sizes and compared to the larger sizes. The location of maximum erosion was at different locations in the first bend as compared to the second bend.
Numerical Prediction of Collection Efficiency of a Personal Sampler Based on Cyclone Principle
Authors: Badhan Antara , Bugarin Luz , Mao Shaolin
Published: December 2014

A personal bio-aerosol sampler is a self-contained, operation flexible, high-efficient device for indoor air quality (IAQ) and health risk exposure monitoring and measurement. Bio-aerosols such germ-laden viruses, microbial species, airborne microorganisms and volatile organic compounds (VOC) are sucked into the sampler and are deposited on the inner wall surface based on cyclone principal. The major concern with bio-aerosol samplers is the collection efficiency. In this study, we use computational fluid dynamics (CFD) tools to evaluate key design parameters, specifically the inlet tube angle and collection tube inner wall roughness. 3D incompressible turbulent flow is simulated using commercial software ANSYS FLUENT. Reynolds stress model (RSM) is used to investigate the turbulence effect with the following boundary conditions (velocity-inlet boundary condition at inlet, outflow boundary condition at outlet and no slip at walls). The numerical approach for air-aerosol interaction is based on an Eulerian-Lagrangian fluid dynamics framework, where the particles or droplets trajectories are computed in a Lagrangian method (discrete phase element) and then conjugate these particles to the continuous phase in the Eulerian frame. The variation of inlet angle affects the collection efficiency of the cyclone separator. In addition, the flow characterizations with different velocity fluctuation profiles validate the continuous phase model. The development and evolution of the vortex core region for the axial velocity are obtained and evaluated in the simulation of the cyclonic flow.
Investigation of Large-Scale Structures Behind a Single Tube (Finned and Foamed Tube) Using Two-Point Correlations
Authors: Abdi Iman Ashtiani , Khashehchi Morteza , Hooman Kamel
Published: December 2014

Flow structures downstream of a finned-tube are compared to those of an identical pipe; with the same diameter and length, covered with a foam layer. The standard case of cross-flow over a bare tube, i.e. no surface extension, is also tested as a benchmark. Experiments are conducted in a wind tunnel at Reynolds numbers of 4000 and 16000. Particle image velocimetry (PIV) was used for flow visualization on two different perpendicular planes. To characterize the size of the flow structures downstream of the tube, for each of the aforementioned case, two-point correlation, as a statistical analysis tool, has been used. It has been observed that by decreasing the Reynolds number, the flow structures are further stretched in streamwise direction for both bare and finned-tube cases. This is, however, more pronounced with the former. Interestingly, with a foam-wrapped tube the sizes of the flow structures are found to be independent of the Reynolds number. Finally, the structure sizes are smaller in the case of the foam-wrapped tube compared to those of finned-tube.
Unsteady Behavior of Leading Edge Vortex and Diffuser Stall Inception in a Centrifugal Compressor With Vaned Diffuser
Authors: Fujisawa Nobumichi , Hara Shotaro , Ohta Yutaka , Goto Takashi
Published: December 2014

Experiments and numerical analyses were used to investigate the unsteady behavior of a vortex generated on the leading-edge of a diffuser (i.e., leading-edge vortex (LEV)) and the diffuser stall inception in a centrifugal compressor equipped with vaned diffusers. The LEV is distinct from the separation vortex of the diffuser’s leading edge and passage vortex of the diffuser; it is generated by the accumulation of vortices caused by the velocity gradient of the impeller discharge flow. The LEV increases with decreasing velocity in the diffuser passage and forms a huge flow blockage within the diffuser passage. Therefore, the LEV may help cause the diffuser stall inception in the centrifugal compressor. A diffuser vane, that was tapered only on the hub side was designed and used in the experiment. The results of the computational fluid dynamics analysis and experiments showed that the tapered diffuser vane can suppress LEV evolution during off-design operations. Therefore, the tapered diffuser vane may control the diffuser stall inception in a centrifugal compressor by suppressing LEV evolution.
Numerical Investigation of the Flow Around a Generic Car Using Dynamic Mode Decomposition
Authors: Peichl Martin , Mack Steffen , Indinger Thomas , Decker Friedhelm
Published: December 2014

The drag of a car is highly dependent on the topology of its complex wake system. Small changes in the shape of the car, that do not have a big effect when considered separately, can lead to significant changes in the total drag when the vortex systems of the changed part of the car body interact with the wake vortices. To understand these interferences, a method is necessary that decomposes the flow based on dynamic information. In this paper, the feasibility of using the Dynamic Mode Decomposition (DMD) to analyze the dynamic behavior of the wake flow of a car is investigated. The DMD is found to extract useful information from the flow when applied to three dimensional velocity vector fields.

The CFD simulations are validated by yet unpublished experimental results from experiments in two different wind tunnels.