RATE OF EVAPORATION FROM A FREE-WATER SURFACE AS INFLUENCED BY EXPOSURE

1961 ◽  
Vol 41 (1) ◽  
pp. 199-203 ◽  
Author(s):  
A. C. Carder
Keyword(s):  
Water Surface ◽  
Meteorological Factors ◽  
Free Water ◽  
Water Evaporation ◽  
High Wind ◽  
Progressive Decrease ◽  
Factors Affecting ◽  
Wind Velocities ◽  
Rate Of Evaporation ◽  
Low Rate

In a 3-year free-water evaporation study, an evaporimeter tank in the open field lost 34.5 per cent more water than a tank sheltered by buildings and trees. Meteorological factors responsible for this difference appear to be high wind velocities and long daily periods of sunshine. Changes in temperature regime had no effect.Difference in evaporation from the two tanks led to examination of data obtained over 35 years from the sheltered tank. It was found that, although there was a progressive decrease in amount of evaporation over the years from this tank, rainfall at the same time had increased and that the effect of this increase on evaporation was roughly equal to that of all other factors affecting evaporation, such as a change in exposure, etc. Thus, the comparatively low rate of evaporation from the sheltered tank was undoubtedly due in part to the proximity of buildings and trees which had been established.

The Rate of Evaporation of Water through Duplex Films

1948 ◽  
Vol 1 (2) ◽  
pp. 197 ◽  
Author(s):  
AR Gilby ◽  
E Heymann
Keyword(s):  
Atmospheric Pressure ◽  
Interfacial Layer ◽  
Water Surface ◽  
Complex Nature ◽  
Water Molecules ◽  
Total Evaporation ◽  
Film Evaporation ◽  
Wind Velocities ◽  
Rate Of Evaporation ◽  
The Stability

The stability of duplex films of hydrocarbon oils containing spreaders is discussed in this paper. Duplex films containing spreaders of high molecular weight and of complex nature, e.g. stand oil, eucalyptus residue, polymerized oleic acid, may remain spread for long periods but are thermodynamically metastable. The penetration of water molecules from a water surface through a duplex film has been discussed in terms of the evaporation resistances of the interfacial layer of spreader, the bulk layer of oil and the stagnant layer of air above the film. Evaporation through duplex films of thickness 1-100 μ has been studied in conditions of " still air " at atmospheric pressure and in a vacuum, and in non-turbulent winds at several controlled wind velocities. The efficiency of duplex films in reducing evaporation is greater in wind than in still air and Increases with the wind velocity. When duplex films thicker than 10 μ are placed on water surfaces, even a wind at 8 miles per hour does not increase the rate of evaporation. Thus with such films the resistance of the stagnant layer of air above the film is small compared with that of the oil layer and of the interfacial film of spreader. With all duplex films thicker than 10 μ the total evaporation resistance is proportional to the film thickness and depends on the nature of the spreader. An analysis of the experimental results suggests that the interfacial layer of spreader makes an appreciable contribution to the evaporation resistance of the duplex films under investigation. Approximate relative figures characterizing the magnitude of this contribution are calculated for several spreaders.

scholarly journals Development of mass-transfer evaporation model for Lake Nasser, Egypt

2019 ◽  
Author(s):  
Mohamed El-Sayed El-Mahdy ◽  
Mohamed S. Abbas ◽  
Hassan M. Sobhy
Keyword(s):  
Mass Transfer ◽  
Water Surface ◽  
Free Water ◽  
Meteorological Station ◽  
Coefficient Of Determination ◽  
Water Evaporation ◽  
Evaporation Model ◽  
Free Water Surface ◽  
Lake Nasser ◽  
Simple Mass

Abstract Evaporation from free water surface is considered a very important constituent in both the energy and hydrologic cycles. Precise measurement of evaporation from the free water surface is almost impossible. This is why we need a calculation model for free water evaporation. In this study, a simple mass-transfer evaporation model was developed to be applicable over Lake Nasser in the hyper-arid region located in the south of Egypt. Measured meteorological data (2011–2014) at two stations, Aswan and Abu-Simbel, were used to calculate free water surface evaporation using Priestly–Taylor equation. Priestly–Taylor equation was used because it is the most appropriate equation for Lake Nasser evaporation according to the literature. Results from this model were used to develop a simple mass-transfer evaporation model. The statistical analysis for both calibration and validation periods were very good. The slope of the regression line is about 0.9, with a coefficient of determination of 0.98. The t value is 0.6, at p value of 0.544, which is much greater than 0.05. The developed model could be used with confidence at Aswan meteorological station or on the average of the two meteorological stations, while it should be used carefully on Abu-Simbel meteorological station.

Rate of Evaporation from a Free Water Surface by a Perpendicular Air Stream

1938 ◽  
Vol 30 (10) ◽  
pp. 1131-1138 ◽  
Author(s):  
M. C. Molstad ◽  
P. Farevaag ◽  
J. A. Farrell
Keyword(s):  
Water Surface ◽  
Free Water ◽  
Free Water Surface ◽  
Air Stream ◽  
Rate Of Evaporation

Impacts on Water Consumption in Wet Flue Gas Desulfuration

2014 ◽  
Vol 986-987 ◽  
pp. 151-155 ◽  
Author(s):  
Hai Ping Xiao ◽  
Lin Dong ◽  
Gao Yan Han ◽  
Xiang Ning
Keyword(s):  
Waste Water ◽  
Heat Release ◽  
Sulfur Content ◽  
Water Consumption ◽  
Flue Gas ◽  
Material Balance ◽  
Bound Water ◽  
Free Water ◽  
Water Evaporation ◽  
Factors Affecting

Material balance calculation was adopted to a bubbling desulfurization system of 600MW unit for water-saving measures. Analysis was made on main factors affecting water consumption. Results showed that heat release of desulfurization reaction and water evaporation went up with sulfur content increasing; Free water and bound water in gypsum increased rapidly with calcium improved; When sulfur content enhanced from 0.5% to 3.5%, water evaporation of reactor increased by 28.9% and waste water increased by 7.8%; With inlet flue temperature of WFGD raised from 120°C to 200°C, waste water increased by 25.3% and evaporation of water increased by 102.35%; Once gas-gas heater (GGH) was installed, heat release of original flue gas decreased by 43.72% and the total water consumption decreased by 39.06%. Therefore, with sulfur content and temperature of inlet flue increasing, water consumption raises. Installation of gas-gas heater (GGH) can effectively reduce water consumption of WFGD system.

Dewatering of Sludge by Natural Methods

1990 ◽  
Vol 22 (3-4) ◽  
pp. 239-246 ◽  
Author(s):  
S. Marklund
Keyword(s):  
Water Surface ◽  
Winter Season ◽  
Free Water ◽  
Two Phase ◽  
Closed Chamber ◽  
Free Water Surface ◽  
Critical Moisture ◽  
Sludge Drying ◽  
Rate Of Evaporation ◽  
Full Scale Tests

Drying fron a free water surface and from a waste activated sludge was studied In three separate experimental arrangements. Evaporation in a closed chamber with a surface area of 1.0 m2 was studied with temperatures between 20 and 60°C and air flows between 75 and 300 m3/hour. The rate of evaporation varied between 351 and 746 gram/m2 hour. The efficiency varied between 11 and 20%. To increase the efficiency the air-liquid area has to be enlarged. Evaporation from two pilot sludge drying beds was studied in an open air test lasting four months. One similar bed was tested in a controlled environment. The results showed that above a critical moisture content between 600 and 1100% evaporation from sludge equals the rate of evaporation from a free water surface. Below the critical moisture level the rate decreases rapidly. Further work should be directed towards full-scale tests with covered drying beds. Special attention should be drawn to methods to improve the drying rate during the falling rate period, to two phase drying and to the evaluation of a combined dewatering system with sludge freeze drying in winter season and sludge drying in summer season.

EFEKTIVITAS TANAMAN GENJER DALAM MENURUNKAN BOD DAN COD LIMBAH CAIR TAHU HASIL PROSES ANAEROB

2016 ◽  
Vol 4 (1) ◽  
Author(s):  
Muhammad Irvan Nurliansyah
Keyword(s):  
Water Surface ◽  
Free Water ◽  
Surface Flow ◽  
Free Water Surface

ABSTRAK Limbah cair tahu merupakan limbah cair yang berasal dari proses pembuatan tahu. Limbah cair tahu mengandung senyawa organik yang tinggi. Pembuangan limbah cair tahu secara langsung ke badan air tanpa dilakukan pengolahan dapat mempengaruhi dan mencemari lingkungan. Suatu cara untuk menanggulangi permasalahan tersebut adalah melakukan pengolahan limbah cair tahu. Salah satu alternatif pengolahan limbah cair tahu yang dapat digunakan adalah fitoremediasi menggunakan tanaman genjer. Penelitian ini bertujuan untuk mengetahui efisiensi pengolahan dan efektivitas waktu tinggal pengolahan limbah cair tahu menggunakan tanaman genjer dalam menurunkan BOD dan COD effluen hasil proses pengolahan anaerob limbah cair tahu. Metode yang digunakan dalam penelitian ini adalah fitoremediasi menggunakan tanaman genjer pada sistem lahan basah buatan Free Water Surface flow dengan waktu tinggal 3 hari, 5 hari dan 7 hari. Hasil penelitian menunjukkan bahwa efisiensi pengolahan secara fitoremediasi pada hari ke 3 untuk BOD dan COD berturut-turut sebesar 21,28% dan 16,13%. Pada hari ke 5 efisiensi pengolahan yang diperoleh untuk BOD dan COD berturut-turut sebesar 52,60% dan 45,93% sedangkan efisiensi pengolahan pada hari ke 7 untuk BOD dan COD berturut-turut sebesar 76,42% dan 70,74%. Waktu tinggal efektif yang diperoleh pada penelitian ini adalah  7 hari dengan nilai BOD dan COD telah berada dibawah baku mutu yaitu berturut-turut sebesar 72,72 mg/l dan 213,33 mg/l.   Kata kunci : limbah cair tahu, fitoremediasi, tanaman genjer, efisiensi pengolahan, waktu tinggal

Remote turbidity measurement with a laser reflectometer

1998 ◽  
Vol 37 (12) ◽  
pp. 255-261 ◽  
Author(s):  
Mark Johnson
Keyword(s):  
Water Surface ◽  
Free Water ◽  
Optical Scattering ◽  
Flowing Water ◽  
Water Stream ◽  
Water Turbidity ◽  
Water Colour ◽  
Contact Measurement ◽  
Optical Instruments ◽  
Better Than

A simple, laser-based reflectometer is described for the measurement of water turbidity via 180° optical scattering. Applications exist both in clean source waters (0-1000NTU) with a minimum detectable turbidity better than 1NTU, and in dense wastewater primary-clarifier sludges. The non-contact measurement is performed from a distance at least up to 10m, substantially avoiding the usual window fouling problems of optical instruments. By measuring directly in the process, through a free water surface or on the side of a flowing water stream, the difficulties of transporting sample to the instrument are also avoided. Extensions to be described allow measurement also of water colour.

A Free Water Surface Constructed Wetland in Treating Sugarcane Wastewater

2011 ◽  
Vol 33 (1) ◽  
pp. 71-86
Author(s):  
Doorce S. Batubara ◽  
Donald Dean Adrian
Keyword(s):  
Constructed Wetland ◽  
Water Surface ◽  
Free Water ◽  
Free Water Surface
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