ON THE CALCULATION OF THERMAL TRANSPIRATION

1955 ◽  
Vol 33 (2) ◽  
pp. 279-285 ◽  
Author(s):  
S. Chu Liang
Keyword(s):  
Pressure Difference ◽  
Thermal Transpiration ◽  
Reasonable Approximation ◽  
Single Maximum ◽  
Measured Pressure ◽  
General Fact ◽  
Kinetic Concept

The equation proposed earlier has been derived from a new kinetic concept. It is shown to be a reasonable approximation of this new consideration. The equation is also shown to be mathematically consistent with the general fact that when the thermomolecular pressure difference is plotted against the normally measured pressure, a single maximum is obtained. The curves calculated from this equation are shown to agree closely with those from the Weber equation using van Itterbeek and de Grande's data. The practical use of the equation is discussed.

Scale modeling studies on stack effect in tall vertical shafts

2011 ◽  
Vol 29 (6) ◽  
pp. 531-542 ◽  
Author(s):  
W. K. Chow ◽  
J. H. Zhao
Keyword(s):  
Air Temperature ◽  
Pressure Difference ◽  
Natural Ventilation ◽  
Performance Based Design ◽  
Scale Model ◽  
Vertical Shaft ◽  
Stack Effect ◽  
Scale Modeling ◽  
Measured Pressure ◽  
Indoor And Outdoor

Natural ventilation was provided by tall vertical shafts such as solar chimney while designing some green buildings. For buildings with a tall vertical shaft located in very cold countries, measured pressure difference due to stack effect was up to 300 Pa. Air motion induced by stack effect would give adequate ventilation flow rate. However, stack effect would also give adverse effect if not utilized properly in this green design. Smoke would spread faster to other parts of the building in an accidental fire. Therefore, estimations of stack pressure by simple hydrostatic equation used to be criticized in performance-based design. Further studies are required and will be justified by scale model experiments in this article. Stack effect in a vertical shaft was studied experimentally by a model shaft of size 0.05 × 0.05 m2 and height 2.0 m. Air temperature inside the model was kept at constant values above outdoor by wounding hot electric wires. Vertical air temperature profiles inside and outside of the model at different heights were measured. Measured air pressure difference profiles between indoor and outdoor were then compared with those estimated from the air temperature difference. Results were then applied to justify stack pressure estimations by the hydrostatic models. From this study, hydrostatic equations are confirmed to be acceptable for studying stack pressure in tall vertical shafts.

Thermal transpiration flow through a single rectangular channel

2014 ◽  
Vol 744 ◽  
pp. 169-182 ◽  
Author(s):  
Hiroki Yamaguchi ◽  
Marcos Rojas-Cárdenas ◽  
Pierre Perrier ◽  
Irina Graur ◽  
Tomohide Niimi
Keyword(s):  
Relaxation Time ◽  
Pressure Difference ◽  
Rectangular Channel ◽  
Circular Cross Section ◽  
Pressure Variation ◽  
Published Data ◽  
Geometrical Parameters ◽  
Normal Distribution Function ◽  
Thermal Transpiration ◽  
Flow Through

AbstractA thermal transpiration flow through a single rectangular micro-channel was studied experimentally for various gas species, including all rare gases, in order to investigate the influence of gas species on the flow properties. The final equilibrium flow characteristics and relaxation time of the pressure variation were evaluated as functions of the rarefaction parameter. The thermal molecular pressure difference was well fitted by the log-normal distribution function, and its magnitude was found to be strongly dependent on the gas species: a larger pressure difference was obtained for molecules of smaller diameter. However, for the thermal molecular pressure ratio and the thermal molecular pressure exponent, which are dimensionless quantities, the dependence on the gas species was negligible. The relaxation time of the pressure variation was well normalized by the characteristic time of the system. The influence of the geometry was evaluated by comparing the present results, obtained for the case of a rectangular channel, with already published data obtained for the case of a circular cross-section tube. The comparison showed that these two geometrical configurations influence the fluid flow in equal manner, if appropriate geometrical parameters are used for their representation.

Dependence of Blood Clot Lysis on the Mode of Transport of Urokinase into the Clot - A Magnetic Resonance Imaging Study in Vitro

1991 ◽  
Vol 65 (05) ◽  
pp. 549-552 ◽  
Author(s):  
A Blinc ◽  
G Planinšič ◽  
D Keber ◽  
O Jarh ◽  
G Lahajnar ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Pressure Difference ◽  
Volume Flow Rate ◽  
Blood Clot ◽  
Linear Regression Analysis ◽  
Imaging Study ◽  
Clot Lysis ◽  
Resonance Imaging

SummaryMagnetic resonance imaging was employed to study the dependence of clot lysing patterns on two different modes of transport of urokinase into whole blood clots. In one group of clots (nonperfused clots, n1 = 10), access of urokinase to the fibrin network was possible by diffusion only, whereas in the other group (perfused clots, n2 = 10) bulk flow of plasma containing urokinase was instituted through occlusive clots by a pressure difference of 3 .7 kPa (37 cm H2O) across 3 cm long clots with a diameter of 4 mm. It was determined separately that this pressure difference resulted in a volume flow rate of 5.05 ± 2.4 × 10−2 ml/min through occlusive clots. Perfused clots diminished in size significantly in comparison to nonperfused ones already after 20 min (p <0.005). Linear regression analysis of two-dimensional clot sizes measured by MRI showed that the rate of lysis was more than 50-times faster in the perfused group in comparison to the nonperfused group. It was concluded that penetration of the thrombolytic agent into clots by perfusion is much more effective than by diffusion. Our results might have some implications for understanding the differences in lysis of arterial and venous thrombi.

INTERARM SYSTOLIC BLOOD PRESSURE DIFFERENCE IS ASSOCIATED WITH A HIGH PREVALENCE OF CARDIO VASCULAR DISEASES- A CROSS-SECTIONAL STUDY IN POLICE WORKER

2020 ◽  
Vol 4 (11) ◽  
Author(s):  
Somesh Raju ◽  
Rina Kumari ◽  
Sunita Tiwari ◽  
NS Verma
Keyword(s):  
Blood Pressure ◽  
Systolic Blood Pressure ◽  
Blood Sugar ◽  
Pressure Difference ◽  
Systolic Pressure ◽  
Working Environment ◽  
Vascular Events ◽  
Cross Sectional ◽  
Blood Pressure Difference ◽  
High Prevalence

Background: Interarm systolic blood pressure difference more than 10 mm of Hg is predictor of cardiovascular and metabolic risk. Despite of sufficient physical activity there is high prevalence of obesity in police personal because of stressful working environment. No studies have addressed the significance of interarm pressure difference among them. Therefore, the present study conducted to access the relation of interarm blood pressure difference with obesity in police personnel. Aims and Objective: To estimate the interarm pressure difference in police personal to see its association with their obesity. Material and Method: This cross-sectional observational study done on 245 police workers in PAC, Sitapur, India. Subjects having more than ten years of working experience were included in study. Anthropometric measurements of subject recorded by following standard protocol. Measurement of systolic pressure in both arm recorded simultaneously by mercury sphygmomanometer. Available data analyze and expressed in percentage, mean with SD and chi square test to see the significance of association. Results: According to anthropometric results of subjects 77.14 prcent subjects were having generalised obesity and 82.04 percent of subjects having abdominal obesity. 34.29 percent of subjects showed abnormally high (?10 mmHg) inter-arm systolic blood pressure difference. Both type of obesity showed positive association with blood sugar level but no association with interarm pressure difference. Conclusion: Interarm blood pressure difference is greater in individual having obesity or prolong duration of service. Such subjects are more susceptible to develop coronary artery disease or peripheral arterial disease in future. Early screening can help to detect the vascular events likely to occur in the future Keywords: Body mass index, Waist circumference, Interarm pressure difference, Random blood sugar

Methods

2017 ◽  
Author(s):  
Stefan Homburg
Keyword(s):  
Labor Supply ◽  
Money Demand ◽  
Rational Expectations ◽  
Overlapping Generations ◽  
Final Section ◽  
Price Setting ◽  
Reasonable Approximation ◽  
Planning Horizons ◽  
Elastic Labor Supply ◽  
Made In

Chapter 8 concludes the text with methodical remarks. It defends key assumptions made in the main text and compares them, to the extent they deviate, with more conventional premises. The chapter starts with a comparison of adaptive versus rational expectations. Thereafter, it contrasts infinite planning horizons, finite planning horizons, and overlapping generations models. The third section, which is devoted to modeling money, discusses money-in-the-utility, the transaction costs approach, and more recent theories that derive money demand from a microeconomic framework. The forth section shows that assuming a highly elastic labor supply is empirically unconvincing, whereas a constant labor supply simplifies the model greatly and appears as a reasonable approximation. The final section contrasts behavioral and choice theoretic approaches to price setting.

scholarly journals Effects of Blade Parameters on the Flow Field and Classification Performance of the Vertical Roller Mill via Numerical Investigations

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Chang Liu ◽  
Zuobing Chen ◽  
Weili Zhang ◽  
Chenggang Yang ◽  
Ya Mao ◽  
...  
Keyword(s):  
Flow Field ◽  
Pressure Difference ◽  
Continuous Phase ◽  
Classification Performance ◽  
Field Analysis ◽  
Discrete Phase Model ◽  
Roller Mill ◽  
Discrete Phase ◽  
Vertical Roller ◽  
Classification Efficiency

The vertical roller mill is an important crushing and grading screening device widely used in many industries. Its classification efficiency and the pressure difference determine the entire producing capacity and power consumption, respectively, which makes them the two key indicators describing the mill performance. Based on the DPM (Discrete Phase Model) and continuous phase coupling model, the flow field characteristics in the vertical roller mill including the velocity and pressure fields and the discrete phase distributions had been analyzed. The influence of blade parameters like the shape, number, and rotating speed on the flow field and classification performance had also been comprehensively explored. The numerical simulations showed that there are vortices in many zones in the mill and the blades are of great significance to the mill performance. The blade IV not only results in high classification efficiency but also reduces effectively the pressure difference in the separator and also the whole machine. The conclusions of the flow field analysis and the blade effects on the classification efficiency and the pressure difference could guide designing and optimizing the equipment structure and the milling process, which is of great importance to obtain better overall performance of the vertical roller mill.

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