Homogeneous Venturi-effect concentrators for creeping flows: Magnifying flow velocities and heat fluxes simultaneously

The critical heat fluxes (CHFs) of subcooled water flow boiling are systematically measured for the flow velocities (u = 4.0 to 13.3 m/s), the outlet subcoolings (ΔTsub,out = 3 to 129 K) and the outlet pressure (Pout = 800 kPa). The SUS304 test tubes of 3, 6, 9 and 12 mm in inner-diameter, d, and 33, 66, 99 and 133 mm in length, L, respectively for L/d = 11 are used. The CHFs first become lower and then become higher with the increase in subcooling. The CHFs for four different inner-diameters with L/d = 11 measured here become higher with the decrease in the diameter. CHF correlation for the latter increasing regime was given in non-dimensional form against average outlet subcoolings based on the experimental data. The correlation can describe not only the CHFs obtained in this work at the outlet pressure of 800 kPa but also the authors’ published CHFs (1284 points) for the wide range of Pout = 159 kPa to 1 MPa, d = 6, 9 and 12 mm, L = 49, 99 and 149 mm, ΔTsub,out = −4 to 130 K and u = 4.0 to 13.3 m/s within 15% difference for 50 K≤ΔTsub,out≤130 K and within +30 to −10% for 30 K<ΔTsub,out<50 K.

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Critical Heat Fluxes of Subcooled Water Flow Boiling Against Outlet Subcooling in Short Vertical Tube

Journal of Heat Transfer ◽

10.1115/1.1725101 ◽

2004 ◽

Vol 126 (3) ◽

pp. 312-320 ◽

Cited By ~ 18

Author(s):

Koichi Hata ◽

Masahiro Shiotsu ◽

Nobuaki Noda

Keyword(s):

Experimental Data ◽

Water Flow ◽

Flow Boiling ◽

Vertical Tube ◽

Heat Fluxes ◽

Outlet Pressure ◽

Subcooled Water ◽

Wide Range ◽

Inner Diameter ◽

Flow Velocities

The critical heat fluxes (CHFs) of subcooled water flow boiling are systematically measured for the flow velocities (u=4.0 to 13.3 m/s), the outlet subcoolings (ΔTsub,out=3 to 129 K) and the outlet pressure Pout=800kPa. The SUS304 test tubes of 3, 6, 9 and 12 mm in inner-diameter, d, and 33, 66, 99 and 133 mm in length, L, respectively for L/d=11 are used. The CHFs first become lower and then become higher with the increase in subcooling. The CHFs for four different inner-diameters with L/d=11 measured here become higher with the decrease in the diameter. CHF correlation for the latter increasing regime was given in non-dimensional form against average outlet subcoolings based on the experimental data. The correlation can describe not only the CHFs obtained in this work at the outlet pressure of 800 kPa but also the authors’ published CHFs (1284 points) for the wide range of Pout=159kPa to 1 MPa, d=6, 9 and 12 mm, L=49, 99 and 149 mm, ΔTsub,out=−4 to 140 K and u=4.0 to 13.3 m/s within 15% difference for 50K⩽ΔTsub,out⩽140K and within −10 to +30% for 30K<ΔTsub,out<50K.

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Patterns of Cerebral Blood Flow and Systemic Hemodynamics During Arithmetic Processing

Journal of Psychophysiology ◽

10.1027/0269-8803.22.2.81 ◽

2008 ◽

Vol 22 (2) ◽

pp. 81-90 ◽

Cited By ~ 21

Author(s):

Natalie Werner ◽

Neval Kapan ◽

Gustavo A. Reyes del Paso

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Time Course ◽

Doppler Sonography ◽

Transcranial Doppler Sonography ◽

Systemic Hemodynamics ◽

Heart Period ◽

Blood Flow Velocities ◽

Flow Velocities

The present study explored modulations in cerebral blood flow and systemic hemodynamics during the execution of a mental calculation task in 41 healthy subjects. Time course and lateralization of blood flow velocities in the medial cerebral arteries of both hemispheres were assessed using functional transcranial Doppler sonography. Indices of systemic hemodynamics were obtained using continuous blood pressure recordings. Doppler sonography revealed a biphasic left dominant rise in cerebral blood flow velocities during task execution. Systemic blood pressure increased, whereas heart period, heart period variability, and baroreflex sensitivity declined. Blood pressure and heart period proved predictive of the magnitude of the cerebral blood flow response, particularly of its initial component. Various physiological mechanisms may be assumed to be involved in cardiovascular adjustment to cognitive demands. While specific contributions of the sympathetic and parasympathetic systems may account for the observed pattern of systemic hemodynamics, flow metabolism coupling, fast neurogenic vasodilation, and cerebral autoregulation may be involved in mediating cerebral blood flow modulations. Furthermore, during conditions of high cardiovascular reactivity, systemic hemodynamic changes exert a marked influence on cerebral blood perfusion.

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SAFARI 2000 MODIS WATER AND HEAT FLUXES, MAUN, BOTSWANA, DRY SEASON 2001

ORNL Distributed Active Archive Center Datasets ◽

10.3334/ornldaac/762 ◽

2004 ◽

Author(s):

W. J. TIMMERMANS

Keyword(s):

Dry Season ◽

Heat Fluxes

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Investigation of the natural ventilation of wind catchers with different geometries in arid region houses

JOURNAL OF MECHANICAL ENGINEERING AND SCIENCES ◽

10.15282/jmes.14.3.2020.12.0557 ◽

2020 ◽

Vol 14 (3) ◽

pp. 7109-7124

Author(s):

Nasreddine Sakhri ◽

Younes Menni ◽

Houari Ameur ◽

Ali J. Chamkha ◽

Noureddine Kaid ◽

...

Keyword(s):

Arid Region ◽

Natural Ventilation ◽

Reduction Rate ◽

Internal Flow ◽

Climatic Conditions ◽

Maximum Pressure ◽

Ventilation Technique ◽

Window Position ◽

The One ◽

Flow Velocities

The wind catcher or wind tower is a natural ventilation technique that has been employed in the Middle East region and still until nowadays. The present paper aims to study the effect of the one-sided position of a wind catcher device against the ventilated space or building geometry and its natural ventilation performance. Four models based on the traditional design of a one-sided wind catcher are studied and compared. The study is achieved under the climatic conditions of the South-west of Algeria (arid region). The obtained results showed that the front and Takhtabush’s models were able to create the maximum pressure difference (ΔP) between the windward and leeward of the tower-house system. Internal airflow velocities increased with the increase of wind speed in all studied models. For example, at Vwind = 2 m/s, the internal flow velocities were 1.7, 1.8, 1.3, and 2.5 m/s for model 1, 2, 3, and 4, respectively. However, at Vwind = 6 m/s, the internal flow velocities were 5.6, 5.5, 2.5, and 7 m/s for model 1, 2, 3, and 4, respectively. The higher internal airflow velocities are given by Takhtabush, traditional, front and middle tower models, respectively, with a reduction rate between the tower outlet and occupied space by 72, 42, 36, and 33% for the middle tower, Takhtabush, traditional tower, and the front model tower, respectively. This reduction is due to the due to internal flow resistance. The third part of the study investigates the effect of window (exist opening) position on the opposite wall. The upper, middle and lower window positions are studied and compared. The air stagnation or recirculation zone inside the ventilated space reduced from 55% with the lower window to 46% for the middle window and reached 35% for the upper window position. The Front and Takhtabush models for the one-sided wind catcher with an upper window position are highly recommended for the wind-driven natural ventilation in residential houses that are located in arid regions.

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