On the reduction of hydraulic resistance based on the hydrophobization of functional surfaces

Analysis of various studies has shown that one of the most promising ways to reduce hydraulic resistance in pipelines during transportation of liquid fluid is a method based on changing the wettability of functional surfaces, i.e. hydrophobization. This paper presents the results of experimental studies of the effect of hydrophobization of pipe surfaces on hydraulic losses. For this purpose, experimental tube samples of steel (20Kh13) were made, on the surface of which a spiral relief was formed using laser equipment, resulting in a hydrophobic state, and the value of the contact angle was 160.7°. From the analysis of the results of experimental studies, the dependence of hydraulic resistance on Reynolds number was obtained, from which it follows that the use of hydrophobic surfaces during water transportation helps to reduce the hydraulic resistance to 9.7%.

Analysis of kinetics of local hydraulic losses on the laterals of radial wells at Belgrade groundwater source

An analysis of the dynamics of the process of biochemical colmation of laterals of radial wells at the Belgrade Groundwater Source is presented. A very good correlation between the rate of forming of the colmations and the concentration of bivalent iron was obtained, on the basis of which the maximum recommended flows and velocities were defined, which are in good agreement with the values from previous articles and studies. The effects of regenerations on yield and the total volume of extracted water (up to 2 times higher than in the case of no regeneration) were investigated using a mathematical and software model. A correlation was developed linking the ratio of the amounts of water extracted with and without regeneration, to the aquifer hydraulic resistance, the coefficient of local hydraulic losses reduction due to regeneration, and the number of regenerations. The factor equal to the square root of the number of regenerations increased by one was added to the expressions for the maximum recommended values of inlet velocities and flows per lateral. The differences in flows and extracted volumes between operating modes with constant flow between regenerations and a constant, minimal water level were also examined using the model. The ratio between the total extracted volumes when the drawdown is kept equal to maximum and when the flow between the regenerations is kept constant reaches up to 1.25.

CALCULATION OF DAMPERS OF LOW-FREQUENCY ACOUSTIC FILTERS TYPE

The article provides analytical dependencies that allowing harmonization the required dynamic characteristics of fluid pressure pulsation dampers with the parameters of their main elements at the given level of hydraulic losses on the devices.

Effect of an Inducer-Type Guide Vane on Hydraulic Losses at the Inter-Stage Flow Passage of a Multistage Centrifugal Pump

A multistage centrifugal pump was developed for high head and high flow rate applications. A double-suction impeller and a twin-volute were installed at the first stage followed by an impeller, diffuser and return vanes for the next four stages. An initial design feasibility study was conducted using three-dimensional computational fluid dynamics tools to study the performance and the hydraulic losses associated with the design. Substantial losses in head and efficiency were observed at the interface between the first stage volute and the second stage impeller. An inducer-type guide vane (ITGV) was installed at this location to mitigate the losses by reducing the circumferential velocity of the fluid exiting the volute. The ITGV regulated the pre-swirl of the fluid entering the second stage impeller. The pump with and without ITGV is compared at the design flow rate. The pump with ITGV increased the stage head by 63.28% and stage efficiency by 47.17% at the second stage. As a result, the overall performance of the pump increased by 5.78% and 3.94% in head and efficiency, respectively, at the design point. The ITGV has a significant impact on decreasing losses at both design and off-design conditions. An in-depth flow dynamic analysis at the inducer-impeller interface is also presented.

Exergetic Evaluation of Steel Coaxial Heat Exchangers

Background: A proven option to found buildings are geothermally activated steel pipes. Statics determine their dimensions. Energy improvement research focuses on the radius of inner pipe of such coaxial geothermal probes. Mass flow rate is often constant when optimizing inner pipe dimensions. In contrast, in this study flow conditions in outer pipe are constant (constant Reynolds number) to ensure that they not change during optimization. Aim is to maximize net exergy difference for the desired flow type by changing inner pipe radius (after deduction of hydraulic effort). System technology can be selected based on this optimal design and its associated boundary conditions for mass flow and temperatures.Methods: Thermal calculations based on Hellström are carried out to quantify an influence of changing inner pipe radius on thermal yield. A hydraulic optimization of inner pipe radius is performed. Increasing inner pipe radius results in decreasing hydraulic losses in inner pipe but increases hydraulic losses in outer circular ring. Net exergy difference is a key performance indicator to combine thermal and hydraulic effects. Optimization of net exergy difference is carried out for selected scenarios. All calculations are based on various, but fixed Reynolds numbers in the circular ring (Re = [4e3; 1e4; 1e5]), instead of fixed mass flow rates. This ensures fixed flow conditions and no unnecessary high mass flow rate.Results: Optimal inner radius is approximately as large as outer radius considering thermal results. Reynolds numbers are always bigger in inner pipe, due to the constant Reynolds number in circular ring. Both indicate that from a thermal point of view, a high mass flow rate and a high degree of turbulence are particularly important. Hydraulic optimal inner pipe radius is 54% of outer pipe radius for laminar flow scenarios and 60% for turbulent flow scenarios. Exergetic optimization shows a predominant influence of hydraulic losses, especially for small temperature gains.Conclusions: Design of coaxial geothermal probes should focus on the hydraulic optimum and take energetic optimum as a secondary criterion to maximize net exergy difference.

Ways to reduce hydraulic losses in multistage centrifugal pumping equipment for mining and oil-producing industries

Purpose. To study hydraulic losses in pumping units during pumping and transportation of liquids, to develop the design and technology solutions to improve the energy efficiency of centrifugal pumps in the mining and oil-producing industries. Methodology. In the theoretical and experimental analysis of hydraulic losses during the transportation of liquids, the hydraulics and experimental analysis methods were used. Findings. As a result of the research carried out, a new design scheme of a multistage centrifugal pump has been developed, providing a coaxial arrangement of impellers, which allows reducing hydraulic losses in pump elements and increasing the energy efficiency of pumping units. Originality. Based on the analysis of existing designs of multistage blowers of axial and centrifugal types, the distribution of hydraulic losses in the elements of a centrifugal blower with coaxial impellers is considered. Experimental dependences on the establishment of pressure flow and power characteristics are presented. Based on the accounting of hydraulic losses, the energy efficiency of the design of the pumping unit with the coaxial arrangement of the impellers was assessed. Practical value. The new design of a centrifugal pump with coaxial impellers reduces hydraulic losses by more than 23% compared to traditional designs of centrifugal pumps. The results of the work can be used by design, research, and industrial organizations engaged in the design and operation of pumping equipment.

Hydrodynamic characteristics of the groundwater source "Kljuc" of the city of Pozarevac

Geological and hydrogeological research conducted in the area of groundwater source "Kljuc" of the city of Pozarevac aimed primarily for determining the groundwater's balance amd reserves. The study groundwater source is used for water supply of about 55 000 inhabitants in the Branicevo district, with a total capacity of approximately 250 l/s. As part of the applied field hydrogeological methods in the study area, by its significance the method of Step-Test pumping, can be singled out. The data from the groundwater source obtained in this way were processed by graphoanalytical method of processing experimental pumping data in transient flow regime, ie application of Theiss solution of differential flow to define hydraulic parameters of well (hydraulic losses in well and filter zone), filtration parameters of the medium and maximum allowed capacities of the well. Hydraulic losses that occur mainly indicate the aging process of wells which usually results in a decrease in their capacity.