The Evaporation of Water from Helix Aspersa

1964 ◽  
Vol 41 (4) ◽  
pp. 783-792
Author(s):  
JOHN MACHIN
Keyword(s):  
Air Flow ◽  
Complex Form ◽  
Ambient Air ◽  
Helix Aspersa ◽  
Flat Surfaces ◽  
Wind Speeds ◽  
Low Wind Speeds ◽  
Rate Of Evaporation ◽  
Snail Helix Aspersa

1. The construction and use of a wind-tunnel apparatus is described in which measurements of evaporation under controlled conditions of temperature, humidity and air flow can be made. 2. Two mathematical formulae, applicable to evaporation in relatively low wind speeds, are described. It is suggested that a promising approach to evaporation from moist-skinned animals is provided by the application of Leighly's formula: E = K(p0-pd)c(v/x)n, where the rate of evaporation (E) is expressed in terms of the vapour pressure at the evaporating surface (p0) and in the ambient air (pd), the wind speed (v) and the length of the evaporating surface parallel to the wind (x). The constant, K, is calculated independently and the terms n and c are left for empirical determination. 3. Values of n and c for different types of evaporating surface are given together with the method used in their calculation. Those relating to flat evaporators and to the snail, Helix aspersa, are shown to differ significantly. 4. In general n increases and c decreases as the amount of air disturbance caused by the snail increases. 5. The fact that n for flat surfaces is in good agreement with previously established theory is taken as evidence that Leighly's formula may be validly applied. 6. The combined determination of n and c is introduced as a convenient assessment of a complex form in terms of air flow and evaporation.

Determination of oral uptake and biodistribution of platinum and chromium by the garden snail (Helix aspersa) employing nano-secondary ion mass-spectrometry

Chemosphere ◽  
2013 ◽  
Vol 90 (6) ◽  
pp. 1829-1838 ◽  
Author(s):  
Tanja Eybe ◽  
Jean-Nicolas Audinot ◽  
Thomas Udelhoven ◽  
Esther Lentzen ◽  
Brahime El Adib ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Helix Aspersa ◽  
Oral Uptake ◽  
Ion Mass Spectrometry ◽  
Snail Helix Aspersa ◽  
Secondary Ion

Performance Evaluation of New Designs of Wind Towers

2002 ◽  
Author(s):  
Mehdi N. Bahadori ◽  
Amir R. Pakzad
Keyword(s):  
Performance Evaluation ◽  
Natural Ventilation ◽  
Evaporative Cooling ◽  
Ambient Air ◽  
Passive Cooling ◽  
High Wind ◽  
Flow Rates ◽  
Wind Speeds ◽  
Low Wind Speeds

Wind towers are architectural designs employed for natural ventilation and passive cooling of buildings. In this study, it is shown that the performance of these towers can be improved appreciably by incorporating evaporative cooling in them. Two designs, called wetted columns and wetted surfaces, were employed, and their performances were evaluated and compared with those of the conventional towers. It is found that both designs can deliver air to the building they serve at higher flow rates and at temperatures very near the ambient air wet-bulb temperatures. In general, the wind tower with wetted columns performs better in areas with relatively high wind speeds, whereas the designs with wetted surfaces performs better in areas with no winds, or with very low wind speeds.

Heat Exchange Effectiveness and Pressure Drop for Air Flow Through Perforated Plates With and Without Crosswind

1994 ◽  
Vol 116 (2) ◽  
pp. 391-399 ◽  
Author(s):  
C. F. Kutscher
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Pressure Drop ◽  
Air Flow ◽  
Ambient Air ◽  
Perforated Plates ◽  
Wind Speeds ◽  
New Type ◽  
Flow Through ◽  
Heat Exchange Effectiveness

Low-porosity perforated plates are being used as absorbers for heating ambient air in a new type of unglazed solar collector. This paper investigates the convective heat transfer effectiveness for low-speed air flow through thin, isothermal perforated plates with and without a crosswind on the upstream face. The objective of this work is to provide information that will allow designers to optimize hole size and spacing. In order to obtain performance data, a wind tunnel and small lamp array were designed and built. Experimental data were taken for a range of plate porosities from 0.1 to 5 percent, hole Reynolds numbers from 100 to 2000, and wind speeds from 0 to 4 m/s. Correlations were developed for heat exchange effectiveness and also for pressure drop. Infrared thermography was used to visualize the heat transfer taking place at the surface.

The Evaporation of Water from Helix Aspersa

1964 ◽  
Vol 41 (4) ◽  
pp. 771-781
Author(s):  
JOHN MACHIN
Keyword(s):  
Boundary Layer ◽  
Layer Thickness ◽  
Water Vapour ◽  
Boundary Layers ◽  
Boundary Layer Thickness ◽  
Direct Method ◽  
Air Flow ◽  
Empirical Relationship ◽  
Helix Aspersa ◽  
Snail Helix Aspersa

1. Air flow and the water-vapour gradient over a freely evaporating surface is described, and the concept of boundary-layer thickness which expresses such a gradient is introduced. 2. A direct method of estimating boundary-layer thickness by means of a hot-wire anemometer is described. 3. Comparison of observed and effective boundary-layer thickness, calculated from evaporation data, have suggested that the gradient of water vapour is steeper than aerodynamic measurements indicate. 4. An empirical relationship between aerodynamic and vapour boundary layers has been obtained for a two-dimensional evaporator and for the snail, Helix aspersa, and a new evaporation formula derived. 5. Evidence for supposing that aerodynamic and vapour boundary layers do not coincide unless the evaporating surface is greater than 22 cm. In length is presented. 6. Possible errors in the estimation of boundary-layer thickness when air flow is interrupted by the snail's shell are considered. 7. The importance of differences in air flow produced by placing the animal in different positions relative to the wind is discussed.

Determination of segmental and overall ventilation of clothed walking human by means of electric circuit analogy

2016 ◽  
Vol 88 (5) ◽  
pp. 586-601 ◽  
Author(s):  
Nagham Ismail ◽  
Nesreen Ghaddar ◽  
Kamel Ghali
Keyword(s):  
Experimental Data ◽  
Air Flow ◽  
Electric Circuit ◽  
Simplified Model ◽  
Body Segment ◽  
Wind Speeds ◽  
Standard Deviation Range ◽  
Circuit Analogy ◽  
Ventilation Rates

A new simplified model has been developed to determine the ventilation induced by swinging motion and external wind for a fabric clothed cylinder representing a limb or a trunk. The simplified model is based on an analogy between air flow and an electric circuit. When a clothed body segment is subject to external wind, the microclimate air flow electric circuit is represented by resistances. When the clothed segment is subject to a swinging motion, the air flow electric circuit is composed of inductance and resistance elements. The model is validated by comparing the predicted ventilation rates to published experimental data in different conditions: varying permeability, wind speeds, swinging frequencies (for the clothed arm), walking conditions, and aperture configurations. The predictions of the simplified model lie within the standard deviation range of the published experiments. Moreover, although it is simplified, the relative error between the simplified model and the published experiment of an oscillating limb is considered acceptable (18%).

EXPERIMENTAL AND ANALYTICAL STUDIES OF VERTICAL AXIS WIND TURBINES

2018 ◽  
pp. 51-58
Author(s):  
B. P. Khozyainov
Keyword(s):  
Wind Turbine ◽  
Flow Velocity ◽  
Wind Power ◽  
Wind Turbines ◽  
Power Efficiency ◽  
Air Flow ◽  
Geometrical Parameters ◽  
Wind Speeds ◽  
Analytical Studies ◽  
Air Flow Velocity

The article carries out the experimental and analytical studies of three-blade wind power installation and gives the technique for measurements of angular rate of wind turbine rotation depending on the wind speeds, the rotating moment and its power. We have made the comparison of the calculation results according to the formulas offered with the indicators of the wind turbine tests executed in natural conditions. The tests were carried out at wind speeds from 0.709 m/s to 6.427 m/s. The wind power efficiency (WPE) for ideal traditional installation is known to be 0.45. According to the analytical calculations, wind power efficiency of the wind turbine with 3-bladed and 6 wind guide screens at wind speedsfrom 0.709 to 6.427 is equal to 0.317, and in the range of speed from 0.709 to 4.5 m/s – 0.351, but the experimental coefficient is much higher. The analysis of WPE variations shows that the work with the wind guide screens at insignificant average air flow velocity during the set period of time appears to be more effective, than the work without them. If the air flow velocity increases, the wind power efficiency gradually decreases. Such a good fit between experimental data and analytical calculations is confirmed by comparison of F-test design criterion with its tabular values. In the design of wind turbines, it allows determining the wind turbine power, setting the geometrical parameters and mass of all details for their efficient performance.

Sign in / Sign up

Export Citation Format

Share Document