For designing facilities operating on organic working fluid according to the Rankine cycle, reliable methods for calculating organic coolant condensation processes in channels, including inclined ones, are required. In this regard, the problem of special importance is to determine condensation heat transfer in the cases when the heat transfer intensity on the coolant side is commensurable with that on the condensation side. The article describes the results of the activity aimed at studying the condensation of R-245fa (considered as a promising coolant) in horizontal and inclined tubes using the Volume of Fluid (VOF) method. By using this method, supplemented with the model of heat and mass transfer at the phase interface, one can visualize the flow structure and obtain data on the local heat transfer characteristics. The prediction results are compared with the experimental data obtained on the experimental setup at the CJSC Turbokon, intended for studying heat and mass transfer processes during condensation of various promising working media. The predicted data have been compared with the experimental data obtained in condensation regimes in a 2 m long copper tube 32 × 2 mm in diameter at mass fluxes up to 27 kg/(m2 s) and tube inclination angles up to ‒24.3°. For simulating the processes at the phase interface, the Lee model was used with automatically calculating the relaxation constant based on the working fluid properties and computation mesh parameters. All calculations were carried out using the in-house CFD code ANES. The article presents data on the distribution of heat transfer coefficients along the tube inner surface. The prediction results are in good agreement with the experimental data, which have shown that the heat transfer coefficient increases significantly even at a small tube inclination. The accomplished study helps gain deeper insight into the condensation heat transfer processes in horizontal and inclined tubes, which is of importance for designing heat transfer apparatuses, such as air and water cooled condensers of the vapors of refrigerants, petroleum products, and other chemical substances. The obtained results can be used for improving the accuracy of engineering calculations and elaborating new design solutions for condensers with taking into account local flow features.

The article points out the relevance of and prospects for integrated use of geothermal resources for solving various problems, first of all, in the field of electricity and heat generation, which is connected with the fact that a significant potential for the development of geothermal energy sources is available in a number of regions in Russia. The article describes the Khankala geothermal power plant as a unique facility for implementing pilot commercial operation of electricity generating units operating based on the organic Rankine cycle (ORC) with applying a low-grade heat source, the use of which in power units of other types is inexpedient. A thermal cycle circuit arrangement for combined use of a geothermal resource is proposed: for electricity generation in an ORC power unit (with using isopentane as working fluid) and for supplying heat to greenhouses. The electric energy obtained in such power unit is consumed to cover the external energy expenditures, namely, for driving the greenhouse facility network pump. Calculations for different geothermal fluid flowrates were carried out, in the course of which the power capacity of the ORC power unit itself and energy expenditures for geothermal fluid reinjection into the well were evaluated, and the optimal parameters of the system considered were determined. For the proposed thermal cycle circuit arrangement implemented at the Khankala geothermal power plant, the geothermal fluid flowrate at which the minimal amount of electric energy is consumed from the external grid, was adopted as the optimal one. In that case, the additional capital outlays for implementing the ORC power unit, which are mainly characterized by the increase in the heat transfer surface sizes of the power plant’s existing delivery water heater and condenser are also minimized. A conclusion has been drawn that incorporation of such power units into low-grade heat recovery systems for electricity generation purposes is very promising, whereas separation of heat supply and electricity generation is less preferred.

Vibration isolating compensators of various designs are used to reduce vibrations in power‑plant piping. Their efficiency can be significantly reduced by pressure pulsations of the working fluid arising from various sources. Pressure pulsations can be mitigated by different types of pulsation dampers. Results are presented for pulsation reduction obtained by the combined use of a broadband damper based on spherical air cavities located outside the main pipe cross‑section and a Helmholtz resonator. Tuning the Helmholtz resonator to the frequency at which the spherical damper exhibits negative efficiency reduces the amplitude of the low‑frequency resonance by two orders of magnitude and widens the frequency range over which pulsations are efficiently attenuated. The design of a test rig is described for investigating the influence of the placement of high‑efficiency broadband pulsation dampers on vibration levels, pressure pulsations, and dynamic forces in a three‑dimensional pipeline system with a pump and working‑fluid flow, including placement of the dampers inside compensators.

Various design versions of the rotor of hydro-steam turbines (HSTs) and their application fields are reviewed. It is shown that the design with nozzles arranged over the periphery has certain shortcomings resulting in a decreased energy efficiency, including a thermodynamically unjustified increase of pressure at the nozzle inlet, which results in excessively high velocities in the nozzle “throat,” a short period of time for which the evaporating medium resides in the nozzle divergent part, and poor aerodynamic characteristics of the peripheral area, which cause increased friction losses during the impeller rotation in a two-phase medium. A hydro-steam turbine impeller design with helical nozzle-channels is proposed. Such design has features that create prerequisites for increasing the turbine efficiency, including a longer time for which the medium resides in the nozzle, a possibility to obtain aerodynamically smooth lateral and peripheral surfaces of the impeller, and better conditions for moisture separation from the medium surrounding the rotating impeller. The conditions under which superheated water enters the impeller are considered, and statements on shaping the impeller profile part are formulated. A procedure for determining the nozzle-channel divergent part’s camber line shape is proposed proceeding from the minimal force interaction between the liquid phase fragments and channel walls. An algorithm for determining the areas of the channel divergent part’s cross sections when the velocity increase and pressure decrease patterns become monotonic in nature as the flow moves from the inlet to the outlet is developed. A solid-state 3D model of the HST four-nozzle impeller obtained in designing the turbine is presented.

To design hydrosteam turbines of the Segner-wheel type, it is necessary to have reliable characteristics of a Laval nozzle with a large expansion ratio when water strongly subcooled to a saturation temperature is fed to the nozzle. The authors have given a review of a number of works on determining the flow-rate coefficient μ and the coefficient of velocity ϕ when water subcooled to a saturation temperature flows out of Laval nozzles. The complexity of the process of outflow of a steam–water mixture has been noted, which is dependent on the relation of the temperature and pressure at entry into the nozzle, pressure behind the nozzle and the nozzle expansion ratio, and the configuration of the entrance region. Experimental data have been given on blowdowns of geometrically similar nozzles with measuring the jet thrust and determining the flow-rate and velocity coefficients. It has been shown that the linear dimensions of the nozzle throat do not influence μ when a constant relation of the length of the throat to its diameter is observed. The velocity coefficient during the outflow of a boiling liquid depends on the linear dimensions of the expanding section of the nozzle, i.e., testing of geometrically similar nozzles do not ensure a correct determination of φ. It has been shown that the nozzles' efficiency must be compared in the design regime when the pressure on the exit section is equal to the pressure in the chamber where the steam–water mixture flows. Analysis results will be useful for calculating and designing a reaction hydrosteam turbine.

The anomalous enhancement of laminar separation flow and heat transfer (AELSFHT) is studied in a channel with two rows of 26 densely packed grooves inclined at angles of ±45° in the case of uniform flow at the entry and the Reynolds number Re varying from 1000 to 5500. The local flow acceleration is validated, when the greatest flow velocity becomes of the order of 1.8 in dimensionless units and the wall layer becomes thinner above the spherical entry segments. In this case, the longitudinal velocity increases to a value of 1.4 at a distance y = 0.005 from the wall for Re = 2500. The interrelation between the local acceleration at the channel center and the AELSFHT is established, the minimum value of the negative acceleration amounting to –25 at Re = 5500 and the relative heat removal from the structured region of the channel reaching up to 5.2.

Consideration has been given to the specific features of the work process of a hydro-steam turbine operating on the principle of Segner′s wheel. A method has been suggested for the organization of entry into the turbine channels that ensures minimum hydraulic losses. It has been shown that losses due to the friction of the rotor wheel rotating in a steam-water medium have a number of specific features that do not allow their reliable calculation assessment at present. At the same time, some maximum estimates have shown that these losses can be quite significant in the turbine’ s total energy balance and force one to pay serious attention to the aerodynamic properties of the periphery zone of the turbine rotor wheel. It has been established that the diversion of the nozzle axes′ direction from the direction of the circumferential velocity of motion of the center of the nozzles' outlet cross section with a view to preventing structure elements from getting into their jets results in a drop of the turbine capacity, which brings about the need for seeking a compromise solution in selecting the angle of this deviation. The calculation assessment of the optimum ratio of the circumferential velocity of motion of the nozzle outlet section to its fictitious velocity corresponding to the available heat drop in a hydro-steam turbine has shown that it lies within 0.32–0.37, depending on the nozzle velocity coefficient, and the flat pattern of the said dependence provides certain freedom to the designer in selecting the turbine design dimensions.

Rapid development of the anomalous enhancement of separated turbulent Re = 6000 air flow and heat transfer in an in-line single-row package of 31 inclined grooves, 0.2 in dimensionless depth, in a singled-out longitudinal region of the wall of a narrow channel is studied. It is due to the interference of vortex wakes behind the grooves and the acceleration in the channel flow core with the formation of a zone of ultrahigh longitudinal velocity. The wave-shaped parameter characteristics are stabilized in the region of approximately 15th groove, whereupon the oscillation amplitudes are moderately reduced. The return flows in the grooves are enhanced with distance from the entry section, the minimum negative friction diminishing from −2 to −4. The total relative heat removal from the structured region increases at q = const by a factor of approximately 2.75 and by the factor of two at T = const with increase in the relative hydraulic losses by the factor of 1.7, as compared with the case of a plane–parallel channel. The relative heat removal from the surface bounded by the contour of the 20th inclined groove amounts to 3.7 (q = const) with increase in the hydraulic losses by the factor of 2.2. An increase in the local maximum of the longitudinal velocity up to a factor of 1.5, as compared with the mean-mass velocity, can be observable.

The results of experimental studies on the creation of highly efficient designs of vibration-isolating compensators for pipelines with liquid are considered. It is noted that the only way to evaluate the effectiveness of various compensators in reducing vibration at different frequencies currently is to compare their transient vibration stiffness or transient mechanical impedance, which were measured on special stands at a given frequency. The stiffness of the compensator increases significantly with increasing frequency vibrations. Hazardous frequencies may vary between piping systems. For this reason, it is impossible to set an integral criterion for the effectiveness of a vibration-isolating compensator, similar to static stiffness. The results of measurements carried out on a special stand on the transitional vibration stiffness of a new design compensator with thin-layer rubber-metal elements (TRME) are presented. The rigidity decreased by 10 or 100 times or more in the frequency range from 50 to 800 Hz relative to the rigidity of a serial compensator based on rubber cord casing (RCC), including in the presence of water inside it. It has been experimentally shown that the vibration-isolating ability of the same compensator as part of a pipeline system, determined by the value of the dynamic force transmitted by the compensator to the pipeline from the pump, significantly depends on the presence of water in them and its flow, which is not taken into account in known methods. The results of testing compensators with RCC and TRME with a bore diameter of 80 mm as part of a stand with a ring pipeline system, a pump, systems for monitoring the flow of the working fluid, vibrations, pressure pulsations, and dynamic (vibration) forces transmitted by the compensators to the pipeline are presented. In a stand with pipelines, the efficiency of vibration-isolating compensators with TRME is still 10 and 100 times higher than compensators with RCC in the absence of water and decreases by an order of magnitude in the presence of water without its flow when the pump is vibrated by a vibrator. Efficiency decreases even further if water flows through expansion joints and pipelines while the pump is running.

Energy-saving technologies are among the priority development lines of Russia’s power industry. In recovering the rejected heat from geothermal sources, especially those located in cold climatic zones in which there is no access to service cooling water resources, it is profitable to use organic coolants, e.g., CFC refrigerants, as working fluid for dry cooling towers. The properties of such coolants have, as a rule, been studied to a sufficient detail in the region of low temperatures, because they are mainly used as working fluids for refrigeration systems at moderate heat fluxes. To obtain data on the boiling of organic coolants on a tube bundle for taking into account the influence of bundle lower tubes on the heat transfer in the upper tubes, a vapor generator mockup with a horizontal tube bundle was developed. High-pressure water served as the heating medium; and electric heaters were provided for additionally heating the CFC refrigerant to a level close to the saturation temperature. The tube bundle includes twelve tubes arranged in three rows along the height: the central row consists of four measurement tubes, and two lateral rows consist of auxiliary tubes. Eight thermocouples are installed at the top and bottom in the slots of the central row heat-transfer tubes for measuring the surface temperature. For the lower and upper rows in the bundle, boiling heat-transfer coefficients were obtained in a wide range of specific heat fluxes. It is shown that the boiling on the upper rows is significantly more (by 30–35