Controlled Production of Natural Gas Hydrates in an Experimental Device with an Internal Circulation Circuit

For countries with limited access to conventional hydrocarbon gases, methane hydrates have emerged as a potential energy source. In view of the European Union’s requirements to reduce the energy intensity of technological processes and increase energy security, it appears promising to accumulate natural gas and biomethane in the form of hydrate structures and release them if necessary. Storing gas in this form in an energy-efficient manner creates interest in developing and innovating technologies in this area. Hydrates that form in gas pipelines are generated by a more or less random process and are an undesirable phenomenon in gas transportation. In our case, the process implemented in the proposed experimental device is a controlled process, which can generate hydrates in orders of magnitude shorter times compared to the classical methods of generating natural gas hydrates in autoclaves by saturating water only. The recirculation of gas-saturated water has been shown to be the most significant factor in reducing the energy consumption of natural gas hydrate generation. Not only is the energy intensity of generation reduced, but also its generation time. In this paper, a circuit diagram for an experimental device for natural gas hydrate generation is shown with complete description, principle of operation, and measurement methodology. The natural gas hydrate formation process is analyzed using a mathematical model that correlates well with the measured hydrate formation times. Hydrates may become a current challenge in the future and, once verified, may find applications in various fields of technology or industry.

Integration of a Solar Parabolic Dish Collector with a Small-Scale Multi-Stage Flash Desalination Unit: Experimental Evaluation, Exergy and Economic Analyses

In this study, a small-scale two-stage multi-stage flash (MSF) desalination unit equipped with a vacuum pump and a solar parabolic collector (PDC) with a conical cavity receiver were integrated. To eliminate the need for heat exchangers, a water circulation circuit was designed in a way that the saline feedwater could directly flow through the receiver of the PDC. The system’s performance was examined during six days in July 2020, from 10:00 a.m. to 3:00 p.m., under two distinct scenarios of the MSF desalination operation under the vacuum (−10 kPa) and atmospheric pressure by considering three saline feedwater water flow rates of 0.7, 1 and 1.3 L/min. Furthermore, the performance of the solar PDC-MSF desalination plant was evaluated by conducting energy and exergy analyses. The results indicated that the intensity of solar radiation, which directly affects the top brine temperature (TBT), and the values of the saline feedwater flow rate have the most impact on productivity. The maximum productivity of 3.22 L per 5 h in a day was obtained when the temperature and saline feedwater flow rate were 94.25 °C (at the maximum solar radiation of 1015.3 W/m2) and 0.7 L/min, respectively, and the MSF was under vacuum pressure. Additionally, it was found that increasing the feedwater flow rate from 0.7 to 1.3 L/min reduces distillate production by 76.4% while applying the vacuum improves the productivity by about 34% at feedwater flow rate of 0.7 L/min. The exergy efficiency of the MSF unit was obtained as 0.07% with the highest share of exergy destruction in stages. The quality parameters of the produced distillate including pH, TDS, EC and DO were measured, ensuring they lie within the standard range for drinking water. Moreover, the cost of freshwater produced by the MSF plant varied from 37 US$/m3 to 1.5 US$/m3 when the treatment capacity increased to 8000 L/day.

Heparin-induced thrombocytopenia diagnosis: a retrospective study comparing heparin-induced platelet activation test to 14C-serotonin release assay

Laboratory confirmation of heparin-induced thrombocytopenia (HIT) is of crucial importance and remains challenging and relies on platelet functional assays highlighting the presence of heparin-dependent platelet-activating antibodies in patient serum or plasma. Platelet functional assays using washed platelets include the 14C-serotonin release assay (SRA), usually described as the gold standard, and the heparin-induced platelet activation assay (HIPA). Since its first comparison with SRA there has been no additional published study regarding HIPA diagnostic performances compared to SRA. Aim of our retrospective study was to compare the concordance between HIPA and SRA in HIT suspected-patients with positive anti-PF4/heparin antibodies between October 2010 and October 2015. Fifty-five HIT-suspected patients who beneficiated from both HIPA and SRA were included. Positive and negative percent agreements were 83.8% (95% CI 68.0–93.8%) and 66.7% (95% CI 41.0–86.7%), respectively. Overall percent agreement was 78.2% (95% CI 65.0–92.2%). Agreement was higher in patients who underwent cardiopulmonary bypass with extracorporeal circulation circuit for cardiac surgery. We also confirm that the use of a minimum of 2 platelet donors to establish positive HIT diagnosis and 4 platelet donors to exclude HIT diagnosis allows obtaining a good agreement with SRA. Although HIPA and SRA were performed with different platelet donors and in different laboratories, HIPA had a good positive agreement with SRA for HIT diagnosis, showing that HIPA is a useful functional assay that does not require radioactivity and could be developed worldwide to improve HIT diagnosis.

Study on performance of thrust disk as auxiliary impeller

Thrust disk as auxiliary impeller has a vital effect on the big power pump unit with wet motor. It can balance the axial force of the unit, provide power for internal cooling circulation circuit of motor, and further reduce the axial length of the unit. Due to the motor chamber space is limited, and the transmission medium is liquid which needs to consider the effect of cavitation, the research of thrust disk of auxiliary impeller is different from the previous studies of rotating channel. In this paper, the hydraulic performance and cavitation characteristics of thrust disk as auxiliary impeller are investigated experimentally under different conditions. A thrust disk test rig was established to obtain data under different rotation speeds and flow points. Three types of volutes with different outlet angles were designed to match the thrust disk as auxiliary impeller in experiments. Results indicate that the law of speed proportion for the traditional centrifugal pump is not applicable to the head of thrust disk as auxiliary impeller. In addition, the flow coverage increases slightly with rotation speed. Furthermore, the higher the speed is, the larger the NPSHs is, and the narrower the range of NPSH is. Besides, the smaller the outlet angle is, the higher the head of the thrust disk as auxiliary impeller is, the worse anti-cavitation performance is. The research could provide reference and guidance for the design of thrust disk as auxiliary impeller.

Application of rooftop solar panels with coolant natural circulation

In line with the energy development strategy of Europe, it is necessary to implement energy efficient buildings, in which the external enclosures are converters of solar energy to thermal. Therefore, the purpose of the publication was the scientific substantiation and development of the solar heating system with the use of rooftop solar panels. Graphical and analytical dependences of the coefficient of thermal efficiency of the solar panel in heat supply system from the angles of solar radiation incoming and the density of the radiation flux were obtained. Analysis of the results showed that the coefficient of thermal efficiency of the solar panel without transparent coating with the placement of pipelines of the circulation circuit of the coolant over the heat absorber increases by 50%.

Marine integral water cooled reactors with steam-condensate process in the primary circuit

Одним из путей улучшения массо-габаритных характеристик судовых водоохлаждаемых реакторов интегрального типа с естественной циркуляцией теплоносителя является реализация пароконденсатного цикла в первом контуре, при котором насыщенный пар с высокой степенью сухости генерируется непосредственно в активной зоне и затем конденсируется в парогенера­торе, отдавая тепло рабочему телу второго контура. Тепловыделяющий канал активной зоны с непосредственной генерацией насыщенного пара состоит из кольцевого твэла и установленной в его полости нетепловыделяющей трубки с навивкой для закрутки потока теплоносителя. Закрутка потока внутри твэла предотвращает кризис кипения на его внутренней поверхности (на наружной поверхности твэла имеет место закризисный режим теплоотдачи), что обеспечивает допустимые значения температур топлива и оболочек твэла при достаточно высокой плотности энерговыделений, характерных для активных зон судовых реакторов. В статье описаны особенности теплогидравлического расчета каналов активной зоны, парогенератора-конденсатора и контура естественной циркуляции интегрального реактора с пароконденсатным циклом в первом контуре. Представлены результаты расчета характеристик реакторов тепловой мощностью 150 и 25 МВт. Показано, что размеры интегральных реакторов с естественной циркуляцией теплоносителя при реализации пароконденсатного цикла в первом контуре не превышают размеры характерные для интегральных водоохлаждаемых реакторов с принудительной циркуляцией теплоносителя, предназначенных к использованию на объектах морской техники. One of the ways to improve the weight and size characteristics of integrated water-cooled reactors with natural coolant circulation is to implement a steam condensate cycle in the primary circuit, in which dry saturated steam is generated directly in the core and then condenses in the steam generator. The fuel channel of the core with the direct generation of saturated steam consists of an annular fuel rod and a non-fuel pipe installed in its cavity with a winding for swirling the coolant flow. The swirling of the flow inside the fuel element prevents a burn up its internal surface (there is a post-crisis heat transfer regime on the external surface of the fuel element), which ensures acceptable temperatures of the fuel and its cladding at a sufficiently high energy density typical for marine reactor core. The article discusses the features of thermal-hydraulic calculations of the core channel, steam generator – condenser and natural circulation circuit of integral type reactor with the steam-condensate cycle in the primary circuit. It is presents the characteristics of marine reactors with a thermal capacity of 150 and 25 MW. It is shown that size of the marine integrated reactors with natural coolant circulation and a steam condensate cycle in the primary circuit is similar to size of reactor with enforced coolant circulation.

The influence of the electromagnetic field on the electric properties of water

<p>This paper presents an experimental study to investigate the effect of using the electromagnetic field on the electric conductivity and dielectric properties of treated tap water by aqua 4 D system according to the time of exposition in a closed water circulation circuit. There is a portion where there is an electromagnetic field obtained by the electromagnetic device. This work includes tap water circulation in the region of the electromagnetic field for 5 min, 10, 15, 20 min. The dielectric and electrical properties were examined and analyzed using the technique impedance spectroscopy in the frequency range going from 0.1 Hz to 1 MHz.</p><p>To initiate the phenomena involving water after magnetization with the electromagnetic field. The results clearly show that the magnetic field reduces the dielectric constant and resistance of water and increase its electric conductivity. In this study, we also find that the electrical conductivity of magnetized water increases.</p>

Сontrol and Regulation of the Hydraulic Jet Pump Operation Mode

Permanent monitoring and remote control of the operation mode of the hydraulic jet pump allows increasing the efficiency of the hydrajet mode of oil wells operation. Based on the analysis of the workflow of the ejection system, the authors reveal the relation between the density and flow rate of the mixed flow and the operating parameters of the oil hydraulic jet pump in the form of nonlinear dependencies, which make it possible to carry out remote control over the flow rate in the bottomhole circulation circuit. In the process of modeling the hydraulic relations between the elements of the ejection system, a binary diagram is constructed. This binary diagram is created in the form of two combined quadrants and presents the obtained regularities between the parameters of the mixed flow at the well outlet and the operation mode of the jet pump. The authors present the method of remote control over the operation mode of a well ejection system by means of varying the flow-rate of power fluid directed to the well by a ground pump unit and by means of changing the dimensions of the components of the flowing part of the jet pump. The regulation of the operation mode of the hydraulic jet pump occurs by changing the position of the operating point of the pumping unit. In the process of regulating the operation mode of the jet pump by changing the operating flow rate, the authors obtain a series of characteristics of the hydraulic system which determine the coordinates of the operating point of the pumping unit. Adjusting the operation mode of the ejection system by changing the dimensions of the components of the flowing part of the jet pump involves creating a series of its own characteristics with constant characteristics of its hydraulic system. The replacement of the components of the flowing part of the jet pump is carried out in a hydraulic way and does not require round-trip operations in the well. The authors present the graphical interpretation of the proposed methods of regulating the operation mode of the well ejection system in the form of combined characteristics of the jet pump and its hydraulic system built in the single system of coordinates.