Heat and moisture transfer kinetics and temperature during drying of fabrics

The methods of approximation of the curve of the drying rate of fabrics according to the methods of A. V. Lykov and V. V. Krasnikov are described. The results of processing experimental data on convective tissue drying are presented. Equations are given for determining the drying time of fabrics, the density of heat flows and the temperature of fabrics during the drying process. The equations for determining the drying coefficient and the relative drying rate are given. An analytical method for determining the temperature for the period of falling drying rate is considered. The comparison of the temperature values according to the results of analytical solutions with the values obtained by the experimental formula is given. It is shown that the number of Bio during drying of fabrics is less than one, and the main limiting factor is the external heat and moisture exchange of the evaporation surface from the surface of the material with the environment. Verification of the reliability of the calculated values obtained with experimental ones is presented. The discrepancy between the values is within 5 % of the accuracy of the experiment and processing.

A Comparison between Evaporation Ponds and Evaporation Surfaces as a Source of the Concentrated Salt Brine for Salt Gradient Maintenance at Tajoura’s Solar Pond

One of the main problems that negatively affect the operation of salt gradient solar ponds and influence its thermal stability is the maintenance of salt gradient profile. Evaporation pond (EP) is designed to generate the salt which is lost by upward salt diffusion from the lower convective zone (LCZ) of the solar pond. Another attractive method is the Evaporation Surface facility (ES). Regions with moderate to high precipitation favor Evaporation Surfaces over Evaporation Ponds. Dry climates will generally favor Evaporation Ponds for the brine re-concentration. This paper investigates the differences between (EP) and (ES) both as a source for salt brine generation by evaporation. The effect of (EP) depth on the area ratio and daily variations of salt concentrations for three years of operation is shown. Results show that evaporation can be a reasonable method for salt brine generation. Reducing the depth of (EP) improves the capability of (EP) for brine re-concentration. It also increases the (EP) surface area for the same quantity of saline water used. Therefore, ESs are more powerful than Eps in salt re-concentration.

A bioinspired solar evaporator for continuous and efficient desalination by salt dilution and secretion

In recent years, solar interfacial evaporation has been one of the most promising techniques to alleviate freshwater scarcity. However, the salt deposition on the evaporation surface limits the long-term operation...

Investigation of the evaporation in the boundary layer

THE PURPOSE. Consider a stationary diffusion problem when a pure liquid evaporates from a flat surface of evaporation into a laminar boundary layer of a forced gas flow (in the absence of deepening of the evaporation surface and wave formation on it) at the number. In the classical model of the diffusion problem of the flow of mass from a flat surface into the laminar boundary layer, only the additional slowing down effect arising in this case is taken into account. However, the resulting solution does not correspond to the general case of evaporation, since in this case the mass transfer can significantly depend on the thermal conditions of the problem, conjugate in phases; in criterion form, this circumstance is expressed by the appearance of an additional parameter [1-3]. Note that this parameter is related to the value of the derivative of the relative concentration along the transverse coordinate on the evaporation surface. In the course of the proposed solution, the temperature of the evaporation surface and, accordingly, the value of this parameter were taken constant. METHODS. When solving the problem, we used approximate numerical methods for integrating the diffusion equation (Euler's method, integro-differential equation method, and also the method of successive approximations). In this case, the retarding effect of the vapor flow from the surface of the phase transition was assumed to be relatively insignificant in our case (which corresponded to the experimental data used in [1-3]. RESULTS. The article analyzes the well-known classical solution of the diffusion equation according to the Hartnett - Eckert model and notes that the result obtained in this case does not correspond to the general case of evaporation, when the mass transfer in the gas phase also depends on the complex. Based on the solution obtained in our work, we come to the conclusion that the effect of this parameter manifests itself in an increase in the thickness of the diffusion boundary layer. In addition, this effect is also associated with the value of the longitudinal coordinate, being more noticeable at its small values. CONCLUSION. The indicated evaporation pattern can be physically explained by a relatively larger amount of evaporated substance than in the “standard” case (since values, in turn, are associated with higher values of the evaporation surface temperature). It can also be assumed that in the region of the gas flow immediately adjacent to the evaporation surface, these factors manifest themselves in a similar way in the case of turbulent flows.

Optimization of the PGV-1000MKO Steam Generator Using CFD

In the VVER -TOI project, new layout solutions were applied in the reactor plant as part of which the steam removal system from the steam generator was changed. Namely, in contrast to the VVER-1000 and VVER-1200 where the steam removal was organized through ten nozzles combined into a steam collector, in the VVER -TOI SG the steam removal was arranged through one nozzle located on the cold collector side. This change leads to the formation of a non-uniform velocity field in the separation volume. To ensure the steam separation characteristics of a horizontal steam generator with one steam nozzle, it was proposed to create a non-uniform resistance on the way of steam motion from the evaporation surface into steam nozzle applying a non-uniform degree of the distribution perforated plate (DPP) perforation. Two computer models of the SG steam volume with different steam removal schemes (one and ten nozzles) were developed, a set of studies on verification and validation was carried out and a set of calculations were performed. Further, to determine the non-uniform degree of DPP perforation, a set of optimization calculations of the SG steam volume with one steam removal nozzle was performed. The non-uniform degree of DPP perforation of the VVER-TOI SG was selected, which provide steam velocity distribution as close as possible to SG with ten steam nozzles. To justify the chosen design, sensitivity analysis was also carried out according to the hole diameters tolerance and steam load profile.

Application of the Surface Energy Balance in Richard's equation-based model using climatic data to calculate soil evaporation

<p>This research aims to observe the behaviour between heat flow at the limit of the unsaturated area and the earth's surface (evaporation) through different methods based on the surface energy balance. This behavior has been determined by the DRUtES. DRUtES is a free software able to determine the evaporation in the surface using climate and hydraulic parameters determined by the Richard equation. Richards’ equation describes the flow of water in an unsaturated porous medium due to the actions of gravity and capillarity neglecting the flow of the non-wetting phase, usually air (Farthing & Ogden, 2017). </p><p> </p><p>The results obtained have been compared with the Penman-Monteith potential evapotranspiration model, this one as a referenced value. The results obtained help to understand the loss of water in the unsaturated area. This first approach using DRUtES and evaporation methods will allow a deeper investigation in the future regarding the impact of climate change on climate variables and their effects on soil moisture (unsaturated area) and natural aquifer recharge.</p><p><strong>Key words</strong>: Evaporation, surface energy balance, Richard's Equation, zone unsaturated, Penman-Monteith.</p>

Methodology and results of studying soil moisture after the interaction with the operating devices

Operating devices for soil cultivation in arid conditions should not carry the lower layers to the surface of the field, since this leads to the loss of moisture due to its evaporation. Purpose of work is to determine the moisture content in the soil after using new operating devices. There been developed technique of determining the moisture content in the soil after exposure to operating devices by studying the movement of soil layers in the vertical direction and comparing their moisture. The movement of soil in the vertical direction is quantified by a comparative study of the moisture content in the upper and lower layers of the treated formation before and after exposure to operating devices. Using appropriate equipment, there were determined the moisture content in the most susceptible to evaporation surface layer of 0–5 cm and then the average value of the layer-by-layer measurement up to a depth of 25 ÷ 35 cm, depending on the selected operating modes of the operating device.

The influence of the heating scheme of a heterogeneous drop on the characteristics of micro-explosion fragmentation

According to the experimental results, a comparison of sizes of child-droplets after micro-explosion of drop based on water and diesel has been made. Convective, conductive, or radiative heat exchange has been dominated. The temperature of the medium and the relative volume concentration of the flammable liquid have been varied in ranges: 100-450 С, 10-90 vol. %. The ratios of the sizes of the formed drops to the initial ones have been established. The conditions, which make it possible to increase the total evaporation surface area of a liquid by tens of times, are shown.