Density Irrigation Research Articles

Heat transfer and irrigating liquid hydrodynamics on one-row vertical bundle of inclined tubes in falling film heat exchanger

Spiral-wound heat exchangers widely used currently in various industries provide efficient heat transfer between media through spiral tube winds at evaporation and boiling of falling liquid film. The investigated bundle in the form of one-row vertical bundle of inclined tubes (5 degrees to the horizon) simulates a part of a spiral-wound heat exchanger. Heat transfer and hydrodynamics processes are studied at falling film irrigation by liquid R21 refrigerant at 3 bar of absolute pressure with water as heat carrier. The bundle is placed inside of rectangular heat exchanger with optical windows. Heat transfer measurements are performed for tubes at different positions on the bundle height. Irrigation densities corresponded to falling film Reynolds numbers 300 – 1100, heat flux values within the range of 5000 – 10000 W/m2.

Energy resource efficient designs of small-sized devices for recycled water cooling

Introduction. To use natural sources in rational way, plantsof continuous cooling of closed systems of recycling water supply are used. The paper presents designs of small-sized devices for recycling water cooling which are energy resource effective due to twisted motion of air flow, moving countercurrent to the cooled water. Heat and mass transfer is a nanotechnological process that occurs at the intermolecular level. Methods and materials. Countercurrent mini cooling towers are widely used in all industries,but there are some disadvantages, the main of which is the insufficient interaction time of the moving phases. Screw motion of air flow is created by the tangential supply of cooling air in the bottom part of cylindrical small-sized cooling tower. The rate of rotary motion decreases as air flow moves up in cooling towers, and vertical parameter of the rate – increases. Such scheme of the air flow motionmakes it possible to decrease average vertical parameter of the rate and to increase phases contact time. Laboratory research. To determine the technological and hydroaerothermal characteristics, as well as to estimate the efficiency of cooling recycled water, and to carry out mass-heat exchange at the intermolecular stagean experimental facility of small-sized cooling tower with twisted air flow has been developed. Conclusions. In accordance with the exponential law it is shown that the rotational component decreases at increasing height, and in accordance with the power law the vertical component increases component with the exponent ~1,79. It is determined that moisture content x and air temperature tv in the volume of the height of the sprinkler varies according to a power law, in particular for a screw cooling tower proportionally x ~ h0,83, t в ~ h1,25. It was determined that the coefficients of mass transfer βxv and heat transfer αv of a mini cooling tower with twisted air flow at the intermolecular level with equal irrigation densities are 20% higher than the coefficients of a mini cooling tower with counter-current flow. Also it has been determined experimentally a dependence of aerodynamics resistance coefficient of the twisted irrigator of the cooling tower on criterium Refor air flow, and it was determined that it decreases like Re–K2 as the exponent K2 varies in the range 0.114÷0.193 depending on the irrigation density

Styrene and Bioaerosol Removal from Waste Air with a Combined Biotrickling Filter and DBD–Plasma System

A combined system of a biotrickling filter and a non-thermal plasma (NTP) in a downstream airflow was operated for 1220 days for treatment of emissions of styrene and secondary emissions of germs formed in the biological process. The biotrickling filter was operated at variable inlet concentrations, empty bed residence times (EBRT), type and dosage of fertilizers, irrigation densities, and starvation periods, while dielectric barrier discharge and corona discharge were operated at different specific input energy levels to achieve optimal conditions. Under these conditions, efficiencies in the removal of volatile organic compounds (VOCs), germs and styrene of 96–98%, 1–4 log units and 24.7–50.1 g C m−3 h−1 were achieved, respectively. Fluid simulations of the NTP and a germ emission-based clocking of the discharge reveal further energy saving potentials of more than 90%. The aim of an energy-efficient elimination of VOCs through a biotrickling filter and of secondary germ emissions by a NTP stage in a downstream airflow for potential re-use of purified waste gas as process gas for industrial application was successfully accomplished.

Analysis of dual-flow plates with a large free section

The object of research is the dual-type plates with a large free section. One of the most problematic areas of such plates is their low efficiency, which depends on the operating mode of the dual-type plates with a large free section. The gas-liquid layer on such plates is represented by drops and films of liquid, which are the dispersed phase. In this case, the continuous phase is gas. Insufficient liquid supply on dual-flow plates with a large free section leads to a decrease in the efficiency of such plates.During the research, the method of hydrodynamic modeling was used. This method consists in the fact that the dual-flow plates are investigated first in experimental installations, and their results, according to a certain method, are used to calculate industrial plates.A study of dual-flow plates with a large free section in a wide range of gas and liquid loads has been carried out. The range of work of the plates has been determined. It has been established that the hydraulic resistance of the dual-flow plates with a large free section depends little on the diameter of the column apparatus. An almost complete coincidence of the dependence of the height of the gas-liquid layer on the gas velocity in the column cross-section is shown for dual-flow plates with a large free section installed in columns with diameters D=0.057, 0.4 and 2 m. It is revealed that a column with a diameter of D=0.057 m can be used to simulate the operation of dual-flow plates with a large free section of industrial diameter. For example, for dual-flow plates of the usual free section during hydrodynamic modeling, it is necessary to use pilot plants with columns of larger diameter D=0.15–0.25 m with a large free cross-section can operate at significantly higher gas and liquid velocities compared to the dual-flow plates with a conventional free cross-section.The use of dual-flow plates with a large free section is recommended in absorption processes at high irrigation densities.

The use of non-metal materials in the filler units of cooling towers with circulating water supply system

The design of cooling tower`s filler unit, consisting of inclined-corrugated contact elements, and made of polymer material, is developed and described in this research paper. The experimental studies were conducted to determine the efficiency of cooling the circulating water in the proposed cooling tower. The authors obtained the results of evaluating the heat-mass transfer efficiency coefficient of cooling tower, when changing the mass flow rates of liquid and gas phases. The research results showed that the highest efficiency of cooling the circulating water is observed at relatively low irrigation densities equal to 15-25 m3/(m2·h), while the heat-mass transfer efficiency of cooling tower achieves 72%.The use of non-metal materials as the main elements of cooling tower allows to abandon the use of chemical reagents against bacteria and microorganisms in favor of circulating water ozonation method.

Исследование теплообмена при кипении фреономасляной смеси в трубах испарителей судовых холодильных установок

The paper describes small-capacity irrigation evaporators that improve the performance of a refrigeration unit, as they exclude the release of liquid freon into the compressor suction pipe under sharp increasing of heat load or during ship rolling. The relevance of studying heat transfer at freons boiling in a moving film has been proved. The results and analysis of experimental data on average heat transfer coefficients are presented. The graph shows the dependence of the average heat transfer coefficients on the heat flux density at various irrigation densities. There are presented the results of special experiments determining the effect of irrigation density on heat transfer. It has been stated that the effect of pressure or saturation temperature in the modes of evaporation and developed boiling manifests itself in different ways. With developed boiling, the beam pitch does not have a significant effect on heat transfer. The experiments were carried out on two stands: small-row and multi-row. The pipes were heated with an internal electric heater. It has been inferred that heat transfer in the film is more intense than in volume, therefore, smooth steel pipes can be used in irrigation evaporators instead of finned copper tubes, which are used in flooded devices. The boiling process in a film can be described by equations valid for a large volume, taking into account quantitative differences. The values of a constant coefficient and the criteria exponents are given; the similarity equation for the regime of developed bubble boiling of freons is derived. The calculated dependencies can be applied in evaluating the operation of irrigation evaporators of ship refrigeration units.

Application of the Pulse Tracer Injection Method for Estimating the Mass Transfer Efficiency at Extremely Low Irrigation Densities for the Case of Structured CY Sulzer Packing

The liquid flow pattern of the countercurrent phase water isotope exchange process used for the removal of tritiated water vapor from gases has been studied via the pulse injection of a tracer into a liquid flow. A specific feature of this process is an extremely low water irrigation density in a column. Based on the performed experiments, the liquid holdups have been calculated and the liquid flow pattern has been determined. It has been demonstrated that the standard estimation of the longitudinal mixing effect on the masstransfer characteristics of this process has a limited character and may result in incorrect conclusions at a low irrigation density on packings.

Production functions of irrigated coffee under different planting densities

The aim of this study was to evaluate criteria for irrigation and planting densities best suited to coffee growing to maximize yield. The experiment was conducted in an area of the Department of Agriculture, Federal University of Lavras, Minas Gerais, Brazil, in a randomized complete block design with split-plots and four replications. Planting was carried out using healthy coffee seedlings of the Ruby MG-1192 cultivar. It was observed that the use of irrigation provided for significant increases in processed coffee yield in high density planting from 10,000 to 20,000 plants ha-1. Irrigations based on tensions from 60 kPa to 100 kPa are sufficient to meet the water requirements of coffee in dense plantings, but the increase in the number of plants from 10,000 to 20,000 compromises the sustainability of the crop through the disproportionate increase in water consumption for irrigation, with small increases in yield. For the irrigation tension of 60 kPa, the relative increase in yield outweighs the other criteria for irrigation, with 13,750 plants ha-1 being the number of plants indicated.

Effects of fertilization and cropyears on maize (Zea mays L.) yields in different crop rotations

Four basic elements of crop management of maize production — crop rotation, fertilizer application, irrigation and population density — were studied on chernozem soil in long-term experiments. The weather in all the three years (2004, 2005 and 2006) studied was basically favourable both as regards water supply and temperatures. In the critical phenophase (tasseling and silking in July), however, due to the precipitation amounts differences could be found. In years with favourable water supplies it was the crop rotation and fertilizer application that basically determined maize yields whereas irrigation and population densities did not have significant effects. According to our long-term experimental results we can state that we have to harmonize the key-agrotechnical elements (crop rotation, fertilization, irrigation, plant density) to realize sustainable maize production.

Evolução e partição de fitomassa seca do meloeiro em hidroponia

The work were aiming evaluate the influence of intervals between irrigation and fruits densities on evolution and paTrtitioning of dry biomass of muskmelon variety Cantalupensis cultivar Torreon. The treatment tested were constituted in two daily intervals, from 6 to 19 hours, between irrigation (15 min of irrigation in intervals of 15min - T15 and a period of irrigation of 15min and interval of 30min -T30), and two densities of fruit per plant: one fruit (D1) and two fruits (D2). No interaction between treatments for fenometric variable. The increase in intervals between irrigation no affected the growth, partitioning of dry mass and fruits yield muskmelon hidroponic. The increase from one to two fruits per plant allowed more allocation of fotossintates in organs reproductive (fruits) in 58,04 and 46,45% (correspond period from 742 to 843 degree days), being advantageous to provide enlargement yield of fruits of 44%.

Small‐Scale Variability in Solute Transport Processes in a Homogeneous Clay Loam Soil

Small‐scale variations in transport parameters may have a profound influence on larger scale flow processes. Fiber‐optic miniprobes (FOMPs) provide the opportunity to continuously measure solute resident concentration in small soil volumes. A 20‐channel multiplexed‐FOMP system was used in repeated miscible displacements in a repacked clay loam soil column (20 cm long and 10‐cm diam.) to examine small‐scale, point‐to‐point variability in convective–dispersive transport processes. Transport parameters, measured 10 cm below the surface, were compared at two drip irrigation point densities and two fluxes. Irrigation densities of one irrigation drip point per 4 cm2 and 11 cm2 of column surface area produced similar results. The breakthrough curves measured at 0.10 cm h−1 had a larger immobile phase than at a flux of 1.07 cm h−1 In the clay loam soil the mobile–immobile model fit the breakthrough curves better than the convective–dispersive equation (CDE), with r2 values of 99.6 and 97.1, respectively. This analysis demonstrated that dispersion and mass recovery were much more variable than pore water velocity in this repacked clay loam soil. However, even in the most variable transport conditions encountered, only 17 sampling points were necessary to describe the column average transport parameters within 20% of the mean.

Liquid flow distribution in packed beds by multipoint liquid distributors

A mathematical model of liquid flow distribution in a packing wetted by a multipoint distributor for arrangements of the spray points along the apices of equilateral triangles and squares was examined. The boundary conditions used accounted for the mutual influence of the individual points. The analytical solutions obtained can be applied to determine the local irrigation density at arbitrary points of the packing. An analysis of the effect of trickle finite diameter upon liquid distribution was carried out. Simple approximate equations were derived which can be used to determine the maximum and minimum irrigation densities.

Effect of mesh characteristics of mesh degasifier on the upper limit of steady operation and liquid reserve of bubble tray

In this work we studied the hydraulic mechanisms of operation of trays with overflow devices having mesh degasifiers. The effect of equivalent diameter of a mesh hole d h (at effective mesh cross section ~m =26%) and effective mesh cross section of 26-53% (at d h = 0.00037 m) on the upper limit of steady operation of the tray was studied. The requisite value of ~m was ensured by closing a part of the mesh degasifier with vertical strips placed all over the degasifier. The overflow device (Fig. i) was placed at the center of the sieve tray with a diameter of 0.215 m and a free cross section mt =4.75%. The investigations were carried out in the water--air system at irrigation densities L = 20-70 m3/m2.h and effective gas velocities in the free column cross section Wc = 0.3-1.2 m/sec. The upper limit of steady operation was determined from the effective gas velocity through the holes of the tray sieve Wh which corresponds to the beginnin$ of the rapid rise of liquid reserve hst on the tray at definite weight loads due to liquid L and to gas G. In the study of the effect of mesh characteristics of mesh degasifier on the liquid reserve hst on the bubble tray we used air as the gas phase and liquids whose characteristics are given in Table 1 as the liquid phase. The effect of viscosity of the liquid phase ~L on hst was studied making use of aqueous glycerin solutions because their surface tension changes negligibly within wide limits of viscosity of these solutions. Water and water mixed with the surface-active agent SV-102 and a microquantity of a defoaming agent, viz., tributyl sulfate, were used in the study of the effect of surface tension of the liquid phase OL on hst. Meshes with m m =48.6-62% and d h = 0.00037-0.00159 m were used in the experiments. The effective gas velocity in the column Wc. ef f referred to the bubbling zone was calculated by the equation

Study of the hydrodynamics and mass transfer on a tangential plate

The hydrodynamics and mass transfer during desorption of CO2 by air from water on a tangential plate have been studied at gas flow rates ranging from 0.6 to 3.5 m/sec and irrigation densities ranging from 6 to 22 m3/m2·h; these experiments have shown that the mass transfer and plate efficiency coefficients of the plate considered are high up to 3.5 m/sec air flow rate (referred to the empty column).