Heat exchange during condensation of freons has been studied quite well; however, various flow regimes of the steam-condensate mixture may arise during condensation inside heat-exchange pipes. There is a large amount of experimental data on the condensation of freons inside pipes with different internal diameters. However, the results obtained by different authors are contradictory, and experimental dependencies can give a high error in the event of a discrepancy between the calculated and actual flow regimes of the steam-condensate mixture. Due to the difficulty of identifying these modes for each such case, reliable recommendations for the calculation and design of heat exchangers must be based on experimental data. In order to obtain such materials, an experimental stand was developed and manufactured, allowing the study of condensation processes of various working fluids in a horizontal cooled tube. The working section of the stand was a copper pipe with an external diameter of 32 mm and a wall thickness of 2 mm, built into an external steel pipe with a diameter of 45 × 3 mm with an annular gap of 3.5 mm. Five chromel-copel thermocouples were installed in the gap to measure the water temperature; they were led to the measuring instruments through the wall of the outer pipe. Thermocouples were also installed in the copper pipe wall. The stand’s thermocouples were precalibrated, and the freon and cooling water consumption was determined by the differences on the flow diaphragms with an error not exceeding 1.5

It is shown that the vibration transfer and working medium pressure pulsations through vibration-isolating pipeline junctions of various plants may increase by two or three orders of magnitude with an increase in the vibration frequency and in the presence of incompressible working fluid. The results of research of the found physical models that determine this phenomenon are presented. The experimental results for a spatial three-component broadband active vibration-protection system (AVS) for vibration damping beyond the vibration isolation junction with liquid are considered. An experimental plant scheme for studying the simultaneous spatial active damping of dynamic forces, vibrations and pressure pulsations downstream from the junction has been given. Calculated dependences of the maximum efficiency of considered AVS on frequency are obtained. Efficient active damping of forces is shown to be attainable in an open loop without feedback. While damping in an open loop at the experimental plant, the efficiency of active damping of dynamic forces is obtained in three directions up to 10 dB or more in the frequency range from 5 to 800 Hz (more than seven octaves). The analysis of scientific publications reveals the uniqueness of this result. In this case, there are no zones of negative efficiency outside the active damping frequency range, which appear while using other methods of active damping.

The article proposes a methodology for using digital twins for modeling thermal power plants. Building a digital equivalent allows for virtual testing, monitoring technical condition, optimizing performance and reducing maintenance costs and resource consumption. The method is based on neural network predictive architectures. The input and output parameters of the system are considered as time series. The measured characteristics of installations are taken into account, including state characteristics and external factors. Research has been carried out on MLP and LSTM architectures. The best results were obtained for the LSTM network. The method allows you to predict about ten minutes of work from data about twenty minutes of work.

A concept has been proposed for the creation of regional liquefied natural gas (LNG) fuel complexes on the basis of thermal power plants, ensuring the expansion and reliable functioning of the gas fuel market. The concept provides for the transfer of fuel reserve systems for electric power facilities to LNG, which is produced directly at power plants, as well as the supply of LNG from power plants to regional consumers. A description of a foreign installation for extinguishing gas consumption peaks is given: the closest analogue of a power plant with an LNG fuel backup system. A comparative technical and economic analysis of projects for the construction of a fuel oil facility and an LNG backup fuel system for CHPP-22 of PAO Mosenergo showed that, with comparable capital costs, backup using LNG can provide an economic effect of up to 654 million rubles per year at 2023 prices. If there are large volumes of LNG storage, peak fuel shipments to consumers can be ensured, and the standard reserve will be restored using a liquefaction unit. Data are provided for calculating the costs and investments required to create complexes that guarantee the maintenance of standard emergency fuel reserves in the form of LNG for the CCGT-220 power unit (1778 million rubles excluding VAT). A methodology has been proposed for allocating the costs of a complex of emergency fuels, attributable to the cost of electric power and LNG sold to third-party consumers. It is shown that the relative increase in capital costs for the construction of CCGT-220 with emergency fuel in the form of LNG in relation to similar costs for a power unit with emergency diesel fuel is 1

The results of a numerical analysis of the condensation of R113 freon vapor in a horizontal round pipe with a standard size of 38 × 3 mm in the range of mass velocities from 50 to 150 kg/(m 2 s) were presented. Studies of the features of hydrodynamics and heat transfer in the stratified and stratified wave regimes of condensate flow are still relevant due to their insufficient knowledge. Thus, according to recent data, the heat-transfer intensities in the zone occupied by a stream and in the sections of the inner surface of a horizontal pipe wetted with a thin condensate film are comparable. Therefore, for an adequate assessment of the real contribution of the stream region to the average heat transfer coefficient along the pipe perimeter, the existing methods should be refined. The VOF (Volume of Fluid) method realized in in-house CFD-code ANES was used to simulate a two-phase flow. The intensity of mass transfer was calculated using a modified Lee model in which the relaxation coefficient was determined automatically based on the algorithm proposed by the authors of this work in previous publications. To describe the turbulent transport, a version of Menter’s SST turbulence model was used. Models of mass transfer, turbulent flows of a liquid film and vapor phase, VOF algorithms, and software tools that implement them were verified on experimental data on R113 freon condensation in a downward flow in a vertical pipe. Numerical modeling of condensation processes has been performed and the obtained data have been compared with the results of calculations using various methods recommended in the literature. Information is presented on the distribution of local characteristics along the length and perimeter of the pipe. It is noted that at low values of mass velocity [50 kg/(m 2 s)] at some distance from the pipe inlet, a hydraulic jump occurs, leading to a significant change in the distribution of the vapor void fraction along the length of the channel.

Airborne noise (AN) levels were measured at workshops in the premises of boiler and turbine compartments (BTCs) of the Mosénergo heating and power plants (HPPs) for T-250/300-240 turbine units and their auxiliary equipment, and the results were analyzed. During the simultaneous operation of the equipment, the primary sources of elevated AN levels were identified. Despite the apparent popularity, simplicity, and extent of examination of the problem, it is yet to be resolved at thermal power plants (TPPs), although the primary sources of noise at TPPs and means of controlling them have long been known and detailed in the literature. An important result inferred from the measurements and their analysis was the absence of a completely diffused AN field in the BTC premises. This enabled us to establish the locations of the sources of elevated AN levels (e.g., location of the brush assembly of a generator exciter), and it suggested that the installation of local soundproof casings can provide necessary reduction in AN levels. Further, it indicated that possible solutions for reducing noise at the BTC workshops of HPP include the improvement of sound proofing and absorption utilizing new, highly effective scientific and technical developments. Particularly, the issue can be mitigated by employing a new, low-frequency, heavy rubber coating. The data and recommendations obtained for the T-250/300-240 turbine units can be used for other types of turbine units at Russian TPPs with similar equipment.

— The article presents the results from studying methods and means for reducing the transfer of vibration and pressure pulsations from power installations through elastic vibration isolators of pipelines carrying liquids (cooling water, condensate, or petroleum products) by suppressing the vibration forces and pulsations of the medium by active suppression systems. The results of studies into this subject carried out within the framework of the agreement between the Russian Scientific Foundation and the Tsiolkovskii Kaluga State University are reported. The article discusses the results from calculation and experimental studies aimed at determining the influence of liquid on the vibration-isolating performance of different kinds of pipeline compensators, including those based on bellows, sleeve-type ones made of rubber cord materials, those based on rubber cord shells, and compensators of a new type containing elastic inserts made using thin-layered rubber-metal elements with the minimal interaction between the structure and working medium. The investigations were carried out with the aim to minimize the transfer of vibration through the compensator by improving its design. The results from experimental studies into the effectiveness of joint suppression of the vibration and pressure pulsations by active methods for reducing the transfer of vibration from power installations to the foundation by means of pipeline compensators are presented. It is shown both analytically and experimentally that there is a frequency band in which the vibration forces transferred through the compensator structure are suppressed by the forces from pressure pulsations. The transfer of vibration becomes a factor of ten or more less than it is in the compensator tested without liquid. A physical explanation for this phenomenon is given, and ways of using it in practice are suggested. A two-channel active vibration protection system with a digital control device containing controllers in the form of standard Butterworth, Chebyshev, and band-pass filters, as well as resonance sections in its feedback circuit, is experimentally studied. With the active joint wide-band suppression of vibration forces and pressure pulsations determining the transfer of vibration through the compensators of pipelines with liquid, the effectiveness was found to be up to 32 dB in the frequency band from 10 to 350 Hz.

Heat transfer enhancement in the interfin space of an air capacitor due to the use of a package of in-line oval-trench dimples inclined at an angle of 45° to the incoming flow at Re=6000 is numeric...

Power plants with CO2 utilization have been designed by Allam, Mateant, Turbocon, etc. One of the main problems of this plant is a condenser for steam-gas mixture with high concentration of non-condensable gas. The process of development of steam condenser for steam-gas mixture is described. Its design is based on the idea of maintaining a constant steam-gas mixture velocity along the steam condensation channel. The shape of the channel with constant SGM velocity is described. To research the heat-mass transfer of gas-team mixture the test plant with tubes crosscut by thermocouples is realized. In the process of testing, gas-steam mixture velocity, pressure and air concentration changed from 0% to 18%. The experimental results have been summarized in a dimensionless equation. The pressure drop and increase of air concentration contribute to the decrease of saturation temperature. The optimal velocity is reached when the surface area of the channel in the condenser is minimal. The optimal velocity is about 30 – 50 m/s. The research results are implemented in the experimental model of high-efficiency condenser. The heat transfer coefficient in this model is equal to about 4500 – 2700 W/(m2K) if air concentration at the inlet is 0–8 %. The designs of high-efficiency condenser for gas-steam turbine plant of 25 MW capacity and the condenser with vertical tubes have been presented.

Enhancement of heat transfer in laminar air flow in narrow channels, whose walls are provided with regularly spaced single-row inclined oval-trench dimples, is associated with designing mini- and micro-channels of microelectronics cooling devices, compact miniature heat exchangers, air capacitors, radiators. Vortex heat transfer is considered using the computational domain of the narrow micro-channel of dimensionless height 1, width 6 and length 4 at periodic boundary conditions. An oval-trench dimple of dimensionless width 1 and length 4.5 is located in the center of the heated wall at an angle of 45 degrees to incoming flow. To solve the Navier-Stokes equations and the energy equation, multiblock computational technique realized in the VP2/3 code on overlapping grids of different topology and with a different density of computational cells has found use. The Reynolds number is equal to 10(3). The dimple depth Delta is varied from 0 to 0.375. Dimples are classified: shallow dimples and dimples of moderate and large depth. As Delta is increased, substantial laminar separated flow augmentation on the entrance portion of the inclined dimple is revealed and explained. Maximum absolute value of relative friction at Delta = 0.375 is twice increased in comparison to this quantity at Delta = 0.1125-0.25. A maximum absolute value of the secondary flow velocity in the dimple reaches 0.72 of bulk velocity. In the case of single-row inclined oval trench dimples with a depth of more than 0.25, in the narrow channel the phenomenon of laminar flow acceleration with a 1.5-fold growth of a maximum core velocity is discovered. It is established that a reason for laminar separated and secondary flow augmentation in the inclined oval-trench dimple lies in a sharp static pressure drop (maximum pressure value is 0.34 and minimum pressure value is -0.14 at Delta = 0.3125) at a very small distance between the centers of high and low pressure zones on the entrance portion of the dimple. By increasing Delta, local relative heat loads on the entrance portion of the dimple on the windward side grow and reach values of 16-17. Maximum thermal performance determined by relative total Nusselt numbers averaged over a streamlined wall section with an inclined dimple is 1.8 at Delta = 0.3125; maximum thermal-hydraulic performance is 1.3 at Delta = 0.25. (C) 2018 Published by Elsevier Ltd.

Vacuum condensers for steam turbines are usually designed at design conditions when all condenser sections are cooled identically with the flowrate of cooling water (or air for air-cooled condensers) and the same air inleakage in each section. A deviation from the design operating conditions occurs due to several causes, such as nonuniform cooling of the condenser heat transfer surface because of its fouling or a fan failure (in air-cooled condensers) and local air inleakage. To investigate condensation under nonuniform cooling conditions, a test facility simulating a condenser was constructed. It consists of two parallel channels. Nonuniformity of cooling in one of the channels was simulated by reducing the cooling water flow. There were regimes with steam feeding into air to model air inleakage occurring in actual condensing units. The experiments were performed in the condensation pressure range of pc = 8–20 kPa. The previous predictions suggest that installation of orifices with a low-pressure drop can reduce the condenser pressure in case of nonuniform cooling. The effect of orifices with different diameters on the condensation process parameters was studied in this test facility. It has been demonstrated that installation of the orifices facilitates a decrease in the condenser pressure with a cooling water flow rate through one of the channels less than 50% of the design value. A range of optimal orifice diameters for this experimental condenser model was determined. According to the experiments, the benefit of orifice installation is observed only in case of joint operation of the condenser with a volumetric degasser, such as a steam jet ejector. The experimental data demonstrate an increase in the efficiency of joint operation of a condenser and an ejector under nonuniform cooling conditions due to installation of orifices in the line of steam-air mixture ejection.

On the basis of the Reynolds-averaged Navier-Stokes equations closed by the shear stress transport model with the consideration of streamline curvature, turbulent flow acceleration in the channel with inclined single-row oval-trench dimples, earlier found in the laminar regime, has been revealed. It is shown that the velocity in the flow core increases up to 1.4 times when dimples are densely packed. The influence of the dense arrangement of dimples on abnormal intensification of the separated flow in the stabilized area of the channel has been assessed. Absolute friction in the backflow zone in the dimple is found to grow up to 5.5 times compared with friction at the smooth channel wall.

An experimental unit has been created to study the processes of boiling and condensation in a closed loop. Experimental studies of non-stationary thermo-hydraulic processes at freon R 113 boiling have been carried out inside tubes of low pressure natural circulation systems. Key factors have been identified affecting auto-oscillations characteristics: filling level of the loop, pressure, heat flux density, geometric characteristics of the evaporating elements. Four characteristic modes of operation of such units have been found out. Thermohydraulic auto-oscillations at high thermal loads have been studied. Process parameters and conditions under which there is no thermo-hydraulic instability have been determined. The phenomenon of thermo-hydraulic resonance has been detected. The influence of the heating method on the instability characteristics has been revealed.

The results of a compact and mobile heat recovery plant design based on the organic Rankine cycle (ORC) with a capacity of 1 MW, which can meet the gas pumping station auxiliaries in power, are presented. The choice of n-pentane as a working fluid, as the cheapest and most affordable on the market and providing condensation of exhaust steam at the atmospheric pressure, and thermal oil 'Thermolan LT' as an intermediate heat carrier has been substantiated. The choice of the work process parameters is focused on reliable long-term work with a minimum amount of maintenance. The plant is designed with the possibility to place its main units outside the technological zone of the main production. The design of the plant main components is presented. The turbine is axial, with five stages with a direct generator drive without a reduction gear. The turbine and generator are placed in a ventilated container. The steam generator is a vertically placed shell-and-tube heat exchanger. The air condenser is with horizontally arranged heat exchange tubes and screw-knurled fins. The recuperator is a shell-and-tube heat exchanger with horizontally arranged longitudinally finned tubes. It has been substantiated that for low-potential heat sources and in the conditions of low air temperatures, the use of heat-recovery plants based on the ORC is the optimal solution.

In the present study it is found that enhancement of air turbulent flow and heat transfer at Re = 10(4) is influenced by a set of one-row oval-trench dimples of depth 0.25 inclined at an angle of 65 degrees to the incoming flow and located at the heated wall of the rectangular (9 x 1) narrow channel when the dimple step H is varied. The periodic section of the dimpled channel 8 in length is considered. The dimple step H is varied from 8 to 2. Abnormal enhancement of flow and heat transfer at H = 2 is followed by both a 4-fold decrease in relative negative friction and a 6.5-fold increase in relative heat transfer in the separated flow zone. A maximum secondary flow velocity in the dimple exceeds by 10% a maximum flow velocity in the plane-parallel channel, reaching 1.27 of bulk flow velocity in the channel. A reason for this phenomenon is associated with forming a very large (up to 1.2) pressure drop between closely spaced zones of high pressure on the windward side of a dimple and of low pressure on its entrance spherical portion. The phenomenon of turbulent flow acceleration with a 1.39-fold increase in the maximum flow velocity (at H = 2) in the dimpled narrow channel in comparison to the plane-parallel channel is discovered. (C) 2019 Elsevier Ltd. All rights reserved.

The absence of literature data on active reduction of the transmission of vibrations and pulsations of pressure through pipeline compensators with liquid is noted. A prototype of active broadband vibration damping system has been studied. The system is intended to determine the transmission of pressure pulsations through pipeline compensators with liquid. We present the results of active system testing with electromagnetic vibrator as a source of compensating force, a piezoceramic emitter as a source of compensating pressure pulsations, and a digital control device. Reducing the forces and pressure pulsations to 18 dB in the frequency band from 10 to 246 Hz has been obtained.

In the energy and transport engineering, in oil and gas transportation systems, it is often necessary to reduce the vibration transfer through the pipelines. The use of compensators in pipelines is not enough for effective vibration isolation of equipment. There are no papers on the issue of reducing the vibration transfer through compensators with liquid, including active methods. The research carried out by the authors has demonstrated, that due to the interaction of the compensator structure vibration and pressure pulsations, with the growth of the frequency the vibration transfer through the compensator and its rigidity can grow by orders of magnitude. On the basis of experimental studies of the vibration transfer through the compensators with liquid, physical and analytical calculation models of compensators structure vibration and resulting pressure pulsations interaction have been created. The comparison of results of the vibration transfer calculations and pressure pulsations through the compensators based on bellows, rubber-shells, new types of compensators with thin-layer rubber-metal elements with the experiment has demonstrated the accuracy of the models. Analytically and experimentally it has been proved the existence of the frequency range, wherein the dynamic (vibration) forces, transferred through compensator Reduction of Vibration Forces and Pressure Pulsations in the Pipeline Compensators with Passive and Active Methods http://www.iaeme.com/IJMET/index.asp 1453 editor@iaeme.com structure, are compensated with the pressure pulsations forces. Vibration transfer decreases ten and more times compared to the compensator structure without fluid. A physical explanation of this phenomenon has been given and methods of its use in practice have been suggested. A two-channel active vibroprotective system (AVS) with a digital control device for broadband combined damping of dynamic forces and pressure pulsations, that determine the vibration transfer through the pipeline compensators with liquid, has been experimentally investigated. The efficiency was up to 32 dB at active damping of forces and up to 25 dB at the pressure pulsations damping in the frequency range from 10 to 350 Hz. Directions for further research have been determined.

The paper proposes a criterion for choosing low-boiling working medium type and the main parameters of the heat recovery unit using the heat of the gas-turbine drive exhaust gases with a capacity of 1 MW for the gas compressor station's own needs and the methodology for determining it at the initial design stage. The data of thermal design and capital costs calculations for the creation of an installation for five types of working mediums are given, as well as the choice of n-pentane as best-satisfying all the requirements.

Developmental active system with a digital control device for simultaneous wideband damping of dynamic forces and pressure pulsations in the pipeline compensators with liquid has been experimentally investigated. Excitation and compensation of vibration and dynamic forces were carried out with electro dynamical vibrators, pressure pulsations piezo electric emitters. The possibility of using standard bandpass filters of Butterworth, Chebyshev, elliptic of various orders types as regulators in the feedback loop has been investigated. Dynamic forces reduction and pressure pulsation damping up to 32 dB in the frequency ranges from 10 to 400 Hz has been obtained.

The possibility of applying the methods of active damping of vibration and pressure pulsations for reducing their transfer from power plants into the environment, the seating, and the industrial premises are considered. The results of experimental works implemented by the authors on the active broadband damping of vibration and dynamic forces after shock-absorption up to 15 dB in the frequency band up to 150 Hz, of water pressure pulsations in the pipeline up to 20 dB in the frequency band up to 600 Hz, and of spatial low-frequency air noise indoors of a diesel generator at discrete frequency up to 20 dB are presented. It is shown that a reduction of vibration transfer through a vibration-isolating junction (expansion joints) of pipelines with liquid is the most complicated and has hardly been developed so far. This problem is essential for vibration isolation of power equipment from the seating and the environment through pipelines with water and steam in the power and transport engineering, shipbuilding, and in oil and gas pipelines in pumping stations. For improving efficiency, reducing the energy consumption, and decreasing the overall dimensions of equipment, it is advisable to combine the work of an active system with passive damping means, the use of which is not always sufficient. The executive component of the systems of active damping should be placed behind the vibration isolators (expansion joints). It is shown that the existence of working medium and connection of vibration with pressure pulsations in existing designs of pipeline expansion joints lead to growth of vibration stiffness of the expansion joint with the environment by two and more orders as compared with the static stiffness and makes difficulties for using the active methods. For active damping of vibration transfer through expansion joints of pipelines with a liquid, it is necessary to develop expansion joint structures with minimal connection of vibrations and pulsations and minimal vibration stiffness in the specified frequency range. The example of structure of such expansion joint and its test results are presented.