scholarly journals The so-called thermoid effect and the question of superheating of a plantinum-silver resistance used in continuous-flow calorimetry

1912 ◽  
Vol 86 (587) ◽  
pp. 330-332 ◽  
Keyword(s):  
Specific Heat ◽  
Continuous Flow ◽  
High Speed ◽  
Electric Heating ◽  
Flow Calorimeter ◽  
Heating Current ◽  
Liquid Moving ◽  
Absolute Measurements ◽  
Good Agreement ◽  
Made In

In a recent paper by Glazebrook, Bousfield, and Smith some doubt has been east on the accuracy of my absolute measurements of the specific heat of water by the continuous-flow calorimeter. It is stated that an error of as much as 6 parts in 10,000 might have occurred in the superheating of the oil-stirred platinurn-silver resistances from which the values of the electric heating current were obtained. On the other band, it is also stated that this error might have been as small as 2.5 parts in 10,000. It was with some surprise that I read this statement, inasmuch as the authors could not have been aware of the rapidity of oil circulation which I used. It has been shown by Osborne Reynolds and others that the heat loss from a surface immersed in a liquid moving in turbulent motion is directly proportional to the velocity of flow. The degree of superheating of a wire immersed in oil will depend then directly on the rate of circulation, bully realising this fact, the resistances which I used were designed by Prof. Callendar and myself to be immersed in oil which could be circulated with great rapidity, These resistances are described in our papers, where the illustration shows approximately to scale the relative sizes of the stirrer and resistances. The paddle was rotated at a high speed by a powerful water motor, and the oil was thrown down with such force that a considerable depression was made in the surface. The oil, thrown sideways, passed up around the bars wires, which were wound loosely on the mica frames. I do not know by what standard Glazebrook, Bousfield, and Smith decide what is "normal stirring" or "very vigorous stirring," but it was evident to me at ones that I must have bad much more rapid circulation than anything used by these authors. In testing the accuracy of my experiments special attention was taken of possible superheating, and tests of stirring were made at the time. The good agreement of the various determinations of the specific heat, made with such different values for the heating current and flow of water, make evident that no large superheating error could have existed without being detected.

Design and Performance of a Miniaturized High-Speed Continuous-Flow Analyzer

1974 ◽  
Vol 20 (4) ◽  
pp. 424-427 ◽  
Author(s):  
William E Neeley ◽  
Stephen C Wardlaw ◽  
Helen C Sing
Keyword(s):  
Sample Size ◽  
Continuous Flow ◽  
High Speed ◽  
Clinical Laboratory ◽  
Small Animal ◽  
Sample Volume ◽  
Small Sample ◽  
Reagent Consumption ◽  
And Performance ◽  
Made In

Abstract Design features and performance of a miniaturized high-speed continuous-flow analyzer are described. Special emphasis is made in the design towards a system that is free from the operational and mechanical complexities found in most of today’s advanced systems. Depending on the particular analyses, sample size varies from 3 to 25 µl and reagent consumption is less than 180 µl per sample. Analyses are performed under steady-state conditions at sampling rates of 150 samples per hour with a 2:1 or 3:1 sample-to-wash ratio. The marked reduction in sample size makes the system ideal for microanalyses, especially in the pediatric clinical laboratory, in small animal research, and in any other cases where small sample volume is especially important.

scholarly journals The time course of the heat effects in rapid chemical changes. Part I.—Apparatus and methods

1930 ◽  
Vol 126 (802) ◽  
pp. 439-469 ◽  
Keyword(s):  
Specific Heat ◽  
Continuous Flow ◽  
Time Course ◽  
Electric Heating ◽  
Volume Of Fluid ◽  
Heating Zone ◽  
Flow Calorimetry ◽  
Chemical Changes ◽  
Heat Effects ◽  
Moving Fluid

Continuous flow calorimetry has now been in use for upwards of 30 years, having been adopted in the first instance by Callendar and Barnes for determination both of the specific heat of water at various temperatures and of J, the mechanical equivalent of heat. The principle of the method is simply that the fluid, upon which calorimetric observations are to be made, is driven continuously through a tube, and at a definite point or part of the tube acquires a certain amount of heat (by electric heating, mixture with another fluid or otherwise). The amount of heat in question is determined by noting the temperature of the moving fluid just before it reaches the heating zone, the temperature of the moving fluid just after it has passed the heating zone and M, the volume of fluid moving through the tube per second. Then the amount of heat received by the fluid per second = Mρσ(θ 1 - θ 2 ) where ρ = density and a = specific heat of the fluid, omitting the slight cor­rections for the exchange of heat between the fluid and its surroundings as it travels between the two points of the tube, at which the temperature observa­tions are made.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

Dynamic model for high-speed rotors based on their experimental characterization

2017 ◽  
Vol 2 (4) ◽  
pp. 25
Author(s):  
L. A. Montoya ◽  
E. E. Rodríguez ◽  
H. J. Zúñiga ◽  
I. Mejía
Keyword(s):  
Dynamic Model ◽  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Experimental Characterization ◽  
Rotating Systems ◽  
Computing Performance ◽  
The Impact ◽  
Stiffness Distribution ◽  
Good Agreement

Rotating systems components such as rotors, have dynamic characteristics that are of great importance to understand because they may cause failure of turbomachinery. Therefore, it is required to study a dynamic model to predict some vibration characteristics, in this case, the natural frequencies and mode shapes (both of free vibration) of a centrifugal compressor shaft. The peculiarity of the dynamic model proposed is that using frequency and displacements values obtained experimentally, it is possible to calculate the mass and stiffness distribution of the shaft, and then use these values to estimate the theoretical modal parameters. The natural frequencies and mode shapes of the shaft were obtained with experimental modal analysis by using the impact test. The results predicted by the model are in good agreement with the experimental test. The model is also flexible with other geometries and has a great time and computing performance, which can be evaluated with respect to other commercial software in the future.

Paper 23: The Collision of Drops with Dry and Wet Surfaces in an Air Atmosphere

1969 ◽  
Vol 184 (7) ◽  
pp. 57-63
Author(s):  
G. J. Parker ◽  
E. Bruen
Keyword(s):  
Steam Turbine ◽  
High Speed ◽  
Size Range ◽  
Drop Surface ◽  
Wet Steam ◽  
Air Atmosphere ◽  
Made In

This paper describes an investigation into the behaviour of drops which impinge upon dry and wet surfaces. This is of particular interest in the context of the wet steam turbine. Two approaches have been made in the studies; these are: (1) Drops were made to impinge normally on to various types of dry, stationary surfaces. The drops were in the size range 300–1500 μm diameter with velocities of 2–9 m/s. (2) Drops were made to impinge on to surfaces moving with considerable velocity at right angles to the motion of the drop. Surface velocities ranged up to 45 m/s. The latter study is of direct interest for the splashing of drops on turbine casings at small glancing angles, as occurs near drainage belts. Analysis of the mechanisms involved is made from the records of high-speed ciné photography.

Effect of Pressure on Bubble Growth Within Liquid Droplets at the Superheat Limit

1982 ◽  
Vol 104 (4) ◽  
pp. 750-757 ◽  
Author(s):  
C. T. Avedisian
Keyword(s):  
Vapor Bubble ◽  
Bubble Growth ◽  
High Speed ◽  
Ambient Pressure ◽  
Organic Liquid ◽  
Liquid Droplets ◽  
Growth Data ◽  
Two Phase ◽  
Photographic Evidence ◽  
Good Agreement

A study of high-pressure bubble growth within liquid droplets heated to their limits of superheat is reported. Droplets of an organic liquid (n-octane) were heated in an immiscible nonvolatile field liquid (glycerine) until they began to boil. High-speed cine photography was used for recording the qualitative aspects of boiling intensity and for obtaining some basic bubble growth data which have not been previously reported. The intensity of droplet boiling was found to be strongly dependent on ambient pressure. At atmospheric pressure the droplets boiled in a comparatively violent manner. At higher pressures photographic evidence revealed a two-phase droplet configuration consisting of an expanding vapor bubble beneath which was suspended a pool of the vaporizing liquid. A qualitative theory for growth of the two-phase droplet was based on assuming that heat for vaporizing the volatile liquid was transferred across a thin thermal boundary layer surrounding the vapor bubble. Measured droplet radii were found to be in relatively good agreement with predicted radii.

scholarly journals An approach to the modeling of a virtual thermal manikin

2014 ◽  
Vol 18 (4) ◽  
pp. 1413-1423 ◽  
Author(s):  
Dragan Ruzic ◽  
Sinisa Bikic
Keyword(s):  
Turbulence Models ◽  
Thermal Conditions ◽  
Heat Fluxes ◽  
Thermal Manikin ◽  
Flow Conditions ◽  
Body Segments ◽  
Nominal Size ◽  
Natural Flow ◽  
Good Agreement ◽  
Made In

The aim of the research described in this paper, is to make a virtual thermal manikin that would be simple, but also robust and reliable. The virtual thermal manikin was made in order to investigate thermal conditions inside vehicle cabins. The main parameters of the presented numerical model that were investigated in this paper are mesh characteristics and turbulence models. Heat fluxes on the manikin's body segments obtained from the simulations were compared with published results, from three different experiments done on physical thermal manikins. The presented virtual thermal manikin, meshed with surface elements of 0.035 m in nominal size (around 13,600 surface elements) and in conjunction with the two-layer RANS Realizable k-? turbulence model, had generally good agreement with experimental data in both forced and natural flow conditions.

scholarly journals Post-liquefaction reconsolidation of sand

2016 ◽  
Vol 472 (2186) ◽  
pp. 20150745 ◽  
Author(s):  
O. Adamidis ◽  
G. S. P. Madabhushi
Keyword(s):  
Void Ratio ◽  
One Dimensional ◽  
Geotechnical Centrifuge ◽  
Significant Damage ◽  
Pore Water Pressures ◽  
The One ◽  
Crucial Parameter ◽  
Excess Pore ◽  
Good Agreement ◽  
Made In

Loosely packed sand that is saturated with water can liquefy during an earthquake, potentially causing significant damage. Once the shaking is over, the excess pore water pressures that developed during the earthquake gradually dissipate, while the surface of the soil settles, in a process called post-liquefaction reconsolidation. When examining reconsolidation, the soil is typically divided in liquefied and solidified parts, which are modelled separately. The aim of this paper is to show that this fragmentation is not necessary. By assuming that the hydraulic conductivity and the one-dimensional stiffness of liquefied sand have real, positive values, the equation of consolidation can be numerically solved throughout a reconsolidating layer. Predictions made in this manner show good agreement with geotechnical centrifuge experiments. It is shown that the variation of one-dimensional stiffness with effective stress and void ratio is the most crucial parameter in accurately capturing reconsolidation.

Theoretical Prediction of Motions of High-Speed Planing Boats in Waves

1978 ◽  
Vol 22 (03) ◽  
pp. 140-169
Author(s):  
Milton Martin
Keyword(s):  
High Speed ◽  
Damping Ratio ◽  
Nonlinear Effects ◽  
Theoretical Method ◽  
Valuable Insight ◽  
Response Characteristics ◽  
Theoretical Predictions ◽  
Response Amplitude Operators ◽  
Phase Angles ◽  
Good Agreement

A theoretical method is derived for predicting the linearized response characteristics of constant deadrise high-speed planing boats in head and following waves. Comparisons of the theoretical predictions of the pitch and heave response amplitude operators and phase angles with existing experimental data show reasonably good agreement for a wide variety of conditions of interest. It appears that nonlinear effects are more severe at a speed to length ratio of 6 than of, say, 4 or less, principally because of the reduction of the damping ratio of the boat with increasing speed, and the consequent increase in motions in the vicinity of the resonant encounter frequency. However, it is concluded that the linear theory can provide a simple and fast means of determining the effect of various parameters such as trim angle, deadrise, loading, and speed on the damping, natural frequency, and linearized response in waves, and that this can furnish valuable insight into the actual boat dynamics, even though the accurate predictions of large motions and peak accelerations would require a nonlinear analysis.

Estimating Critical Speeds of Stepped Shafts with Flexible Bearings

1971 ◽  
Vol 8 (03) ◽  
pp. 327-333
Author(s):  
R. H. Salzman
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Design Stage ◽  
Normal Range ◽  
Critical Speeds ◽  
Stepped Shaft ◽  
Bearing Stiffness ◽  
Variable Support ◽  
Method Show ◽  
Good Agreement

This paper presents a semi-graphical approach for finding the first critical speed of a stepped shaft with finite bearing stiffness. The method is particularly applicable to high-speed turbine rotors with journal bearings. Using Rayleigh's Method and the exact solution for whirling of a uniform shaft with variable support stiffness, estimates of the lowest critical speed are easily obtained which are useful in the design stage. First critical speeds determined by this method show good agreement with values computed by the Prohl Method for the normal range of bearing stiffness. A criterion is also established for determining if the criticals are "bearing critical speeds" or "bending critical speeds," which is of importance in design. Discusser E. G. Baker

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