Evaporation of liquids at low temperatures

Ukrainian enterprises annually generate millions cubic meters of mineralized water, which is discharged into surface reservoirs, and millions cubic meters of highly concentrated solutions and suspensions, which are accumulated and stored in special sludge storages. This waste water causes irreparable damage to the environment. A new method for the evaporation of industrial concentrates by fibrous materials with capillary properties was proposed not so long ago. The use of such materials allows an effective, autonomous, cheap, and extremely simple system to be created for the evaporation for various liquids and concentrates. The research methodology was as follows. Two graduated cylinders of the same diameter were used in our research. One cylinder was filled with the liquid phase to a certain level and used to control evaporation from the surface of the aqueous medium. In the other, experimental cylinder, a vertical cotton strip was additionally placed (from 1 to 21 layers of fabric). The width of the strip was 5 cm. The length of the strip was 50 cm. The density of cotton was 100 g/m2. The research method was to determine the height of liquid phase capillary rise along the strip of fabric and to evaluate reduction in the volume of liquid that evaporates in both cylinders at set temperatures. It was found that in the absence of wind and the distance between the vertically placed strips of 7–15 mm were sufficient to ensure the maximum evaporation intensity. Our long-term experiments in natural conditions confirmed the high efficiency of the proposed method. At an average daily air temperature of 2.3 °C, there was a significant evaporation from the surface of the fabric during the day. In this case, evaporation from the water surface was not observed. It should be noted that the intensity of evaporation under natural conditions depends on a significant number of factors (temperature, wind speed, luminosity, humidity, etc.), so it is difficult to detect a direct relationship between some of them. With increase only in the liquid phase temperature, the evaporation efficiency decreased. At a temperature of 20 °C, the laboratory installation (15 layers of cotton strip) increased the evaporation intensity by more than 2 times, at 46 °C by more than 5 times, at 57 °C by almost 3 times, but at 75 °C only by about 67 %. It is obvious that heating of the liquid phase alone less influences the evaporation process from the surface of the fabric strip, which was cooled rapidly in the atmosphere at a much lower temperature. Therefore, to increase the evaporation intensity, it is necessary to increase temperature for all components of the liquid–fabric system. A fabric with suitable properties, stretched between two metal racks and immersed into the liquid phase with the lower end, can be used as a simple evaporator. Our research has shown that the use of materials with capillary properties in the treatment of liquid solutions allows simple, cheap, and efficient devices to be created for evaporating water and converting liquid waste into a solid phase.

Evaporation of aqueous solution of ethanol into an accelerated laminar boundary layer of air

The results of numerical studies of heat and mass transfer during adiabatic evaporation of an aqueous solution of ethanol into an accelerated steam-air laminar boundary layer on a flat wetted plate are presented. The flow acceleration is realized due to the inclination of the upper channel wall, which ensures the constancy of the Kays acceleration parameter. The dependences of the evaporation intensity of the components of solutions of various compositions are obtained for the acceleration parameter 0 and 10-6 for the flow temperature from 20 to 50 °C. A significant effect of the accelerating pressure gradient on the evaporation intensity and its weak effect on the equilibrium wall temperature are shown.

Application of the TDR Sensor and the Parameters of Injection Irrigation for the Estimation of Soil Evaporation Intensity

The objective of the study was to develop a precise method of determination of the evaporation rate in a soil irrigated with the use of a mobile injection irrigation system. Two methods of constructing functions approximating the value of evaporation have been developed. In the first method, the domain comprises the parameters of injection irrigation, i.e., the dose and the depth of injection, and in the second, the volumetric moisture of soil in the layer immediately below the soil surface, which was measured with time-domain reflectometry (TDR) sensors. For that purpose, a laboratory experiment was carried out, based on 12 physical models. The study was conducted on a natural soil material, with particle size distribution of its mineral parts corresponding to that of a loamy sand soil. It was demonstrated that evaporation intensity increases with irrigation and decreases with increase in the depth of water application. Using TDR sensors, it was also shown that evaporation intensity increases proportionally to the weighted arithmetic mean of the volumetric moisture. Comparison of the two methods indicates that the evaporation intensity of injection-irrigated soil can be estimated with higher accuracy when the domain of the approximating function is the injection depth and dose than when the domain of the function is the weighted mean of volumetric moisture of the surface horizon of the soil. However, the method using TDR sensors for the estimation of evaporation intensity of an injection-irrigated soil has a greater potential for the construction of universal approximating models. In addition, the advantage of the method based on the use of TDR sensors is that it uses arguments for the approximating function, f2(θ˜), in real time.

Moisture distribution, tensile strength, evaporation rate and origin of coastal honeycombs (Tuscan, Italy)

<p>Cavernous weathering is a typical example of the degradation pattern of both natural outcrops and cultural heritage. It is described from all environments on Earth and also on Mars. The most common examples are honeycombs and tafoni. Honeycombs are known from arid, humid, and cold deserts, but best developed honeycombs are often described from coastal areas. There are many ideas on the origin of cavernous weathering (case hardening, chemical alteration), but currently most authors believe that the origin is caused by salt weathering. Huinink et al. (2004) described a theory that inside the pits, the capillary zone is closer to the surface and therefore the intensity of the evaporation is higher than in walls separation the pits. As more evaporation accumulates more salts the pits enlarges faster than surface outsides the pits is retreating. To verify this theory, in the environment of coastal honeycombs in Tuscan (Italy), the depth of the vaporization plane (interface between dry surface zone and deeper capillary zone) was measured by the "uranine-probe" method (Weiss et al., 2020) inside and outside the ten honeycombs. From the depth of the vaporization plane and climatic conditions on the study site, the intensity of evaporation was calculated and from the mineralization of water the amount of precipitated salts was estimated. To determine the effect of case hardening, the tensile strength of honeycomb pits and walls was measured. The vaporization plane measurements show that for all honeycombs, the vaporization plane was closer to the surface in pits than outside. The evaporation intensity was calculated for the mean depth of vaporization plane inside the honeycombs (2 mm) and the mean depth outside the honeycombs (7 mm). In marine environment a solution on a vaporization plane should be saturated with halite which has an equilibrium relative humidity of 75 %. The evaporation intensity inside the honeycombs is 9.4 mm/year for 75 % RH and 2.7 mm/year outside the honeycombs. Considering that the evaporated water is of the same composition as seawater, 0.1-0.4 g salts precipitate from 1 m<sup>2</sup>, most of which is NaCl. Inside the honeycombs precipitate 3 times more salts than outside. The tensile strength inside the honeycombs is approximately the same as outside considering standard deviation (354±339 and 284±157 kPa, respectively), so case hardening does not have any effect. The results correspond to the theory of origin according to Huinink et al. (2004). For a detailed description of the moisture behavior in future studies, it is necessary to better understand the moisture conditions (especially relative humidity on the vaporization plane) and it is vital to perform repeated measurements during various seasons.</p><p> </p><p>References:</p><p>Huinink HP, Pel L, Kopinga K., 2004. Simulating the growth of tafoni. Earth Surface Processes and Landforms 29: 1225–1233.</p><p>Weiss T, Mareš J, Slavík M, Bruthans J. 2020. A microdestructive method using dye-coated-probe to visualize capillary, diffusion and evaporation zones in porous materials. Science of The Total Environment 704, 135339.</p>

Experimental study on the evaporating progress of hexane lens on immiscible liquid：Spreading and receding

The change of evaporation liquid on another immiscible liquid has important guiding significance for many applications. In this experiment, the geometric temperature distribution and evaporation rate of n-hexane droplets were observed and recorded by changing the temperature of deionized water. The results show that with the increase of temperature of deionized water-based solution, the maximum diameter of n-hexane droplet spreading after titration increases gradually, while the minimum diameter of n-hexane droplet disappearing decreases gradually. Meanwhile, the evaporation rate of n-hexane droplet is constant during the whole evaporation process. It should also be mentioned that if the base solution is changed from deionized water to a certain concentration of salt solution, the maximum diameter of n-hexane droplet spreading will be reduced, and the evaporation intensity will be relatively reduced. These experimental results will give us a better understanding of the mechanism and characteristics of droplet evaporation.

The Influence of Atmospheric and Subsoil Impact on the Evaporation Process During Firefighter’s Events

The influence of sun rays, wind speed, and different type of subsoil on the evaporation process was analyzed. A dedicated experimental set-up for investigation of evaporation process of three liquids (ethanol, petrol and tap water) deposited on glass and sand was created. Results indicated that for porous surfaces wind decreased the amount of evaporated liquids. After substitution of wind with sun rays for porous surface evaporation process increased for ethanol and petrol, respectively. Finally, the influence of both wind and sun rays indicated a 1% and 5% decrease of evaporation intensity for tap water and petrol, respectively. While, a 2% increase of evaporated liquid was observed for ethanol. It was noticed that application of porous surface caused the highest improvement of evaporation process for petrol and tap water, while the lowest for ethanol. Moreover, application of wind together with porous surface increased the intensity of evaporation for all analyzed liquids.

Determination of the liquid evaporation rate when categorizing rooms and outdoor installations

Возможность взрыва паровоздушной смеси при аварийном проливе жидкости из технологического аппарата во многом зависит от интенсивности испарения жидкости. Для определения интенсивности испарения существуют уравнения, в которые входят величины, характеризующие свойства жидкости, условия ее нахождения в аппарате перед аварией и условия, в которые попадает выливающаяся жидкость. Критически рассмотрены известные уравнения для определения интенсивности испарения, начиная от уравнения Ленгмюра - Кнудсена и заканчивая уравнениями, вошедшими в нормативные документы по обеспечению пожарной безопасности. Рассмотрены варианты аварийного пролива пожароопасных жидкостей в зависимости от сочетания следующих температур: температуры кипения жидкости, температуры вспышки жидкости, температуры жидкости до пролива и температуры окружающей среды. The possibility of an explosion of a steam-air mixture in the event of an emergency spillage of liquid from the process apparatus largely depends on the liquid evaporation intensity. The evaporation intensity is influenced by the following factors: the properties of the liquid (such as critical parameters, liquid temperature, saturated vapor pressure, flash point) as well as the temperature and pressure of the surrounding atmosphere. To determine the intensity of evaporation there are equations that include values that characterize the properties of the liquid, the conditions of its presence in the device before the accident, and the conditions for the spilling liquid after the accident. There is critically considered the wide range of known equations for determining the evaporation intensity beginning with the Langmuir-Knudsen equation and ending with the equations included in the normative documents on fire safety. The Langmuir-Knudsen equation is valid when liquid evaporation occurs in vacuum. When liquid vaporizes in real conditions it is necessary to take into account the non-isothermic nature of the process and the diffusion of vapors into the atmosphere, as well as the possible entrainment of vapors by convective air flows. After the appropriate corrections as a result of special tests there was obtained the equation for determining the evaporation rate. Variants of emergency spillage of fire-hazardous liquids are considered depending on a combination of the following temperatures: the boiling temperature of the liquid, the flash temperature of the liquid, the temperature of the liquid before the spill and the ambient temperature. Equations for calculating the evaporation intensity are defined for every variant. There is carried out correlation of the variants with liquid evaporation during emergency spill with the classification of liquids according to the state diagram in relation to the range of ambient temperatures according to Marshall.

Impact of Climate Change on Agricultural Total Factor Productivity Based on Spatial Panel Data Model: Evidence from China

To respond to the adverse impact of climate change on agricultural total factor productivity, the question of how to adopt actively appropriate strategies is particularly critical for the stakeholders. However, the previous researchers have paid more attention to investigating the measure methods, regional differences, and determinants of Chinese agricultural total factor productivity, but the possible impact of climate change factors like rainfall, temperature, and evaporation on regional agricultural total factor productivity in China have not yet received the attention that they deserve. Furthermore, more importantly, the study on how to take active measures to reduce and mitigate the negative effects from climate change is relatively small. Therefore, in allusion to the above-mentioned problems, using the data envelopment analysis and building a spatial panel data model embedded with climate change factors, this paper calculated Chinese agricultural total factor productivity and then explored the possible impact of climate change on regional agricultural total factor productivity at a provincial level in China. Results mainly show that the impact of some factors, like annual total precipitation, average temperature in the growing season, and evaporation intensity on regional agricultural total factor productivity, are all very significant and negative, which suggests that the more precipitation, the higher the temperature is, and the higher evaporation intensity would lower agricultural total factor productivity in China. Furthermore, in order to response to mitigate the adverse effects from climate change on agricultural total factor productivity, local governments should continue to increase financial support for the local agricultural economic development, because this action could be beneficial for the related stakeholders in improving agricultural total factor productivity. Summing up, our evidence study would provide an important basic theory basis in terms of increasing agricultural total factor productivity and promoting regional agricultural economic development in China.