The CO2 with superior thermo-physical properties has numerous applications in nuclear reactor, power plant, refrigeration and air conditioning systems as well as in many engineering and industrial ...applications. The complex phenomenon of thermal and hydrodynamic behaviour associated with supercritical CO2 is a continuing research topic for many researchers. The conventional correlations of turbulent forced convection heat transfer failed to predict the heat transfer and flow behaviour especially in the vicinity of the critical condition. The present paper presents a comprehensive review of heat transfer characteristics and correlations with supercritical CO2 employed under heating and cooling condition in horizontal channel or tube. An exhaustive review of implementation of supercritical CO2 used with horizontal and vertical orientation of tubes under turbulent flow condition and other operating parameters (inlet sCO2 pressure, mass flux, temperature, and heat flux) is also reported. In the present work, possible reasons for heat transfer deterioration under heating of supercritical CO2 are discussed. The characteristics of pressure drop, convective heat transfer behaviour, effect of buoyancy, the wall temperature distribution and finally the comparison among different correlations are reviewed extensively for supercritical CO2. The study of these correlations with their range of applicability provides a good insight for efficient thermal design and optimization of heat exchanger especially in thermal power plants.
•Review of heat transfer correlations for supercritical CO2 in horizontal tubes.•Review of experimental and numerical works in different flow configurations.•Influence of operating conditions on heat transfer mechanism and flow behaviour.•Physical reasoning on the variation of correlations with experimental dataset.•Heat transfer deterioration of supercritical CO2 under heating application.
•Longitudinal variation in the ionospheric trough position are studied.•The Interkosmos-19, Kosmos-900 and CHAMP data are used.•All the local time hours, the Northern and Southern hemispheres are ...considered.•The winter conditions at low and high solar activity are discussed.
For the first time a comprehensive pattern of the longitudinal effect of the ionospheric trough position was obtained. We present new results with longitudinal variations of the winter trough position as a function of geomagnetic latitude for both hemispheres and conditions of high and low solar activity and all local time hours. We used a large observational data set obtained onboard the Kosmos-900, Interkosmos-19 and CHAMP satellites for quiet geomagnetic conditions. We found that a magnitude of the trough position longitudinal effect averaged for a fixed local time is greater in the daytime (6–8°) than in the nighttime (3–5°). The longitudinal effect magnitude reaches its maximum (16°) in the morning (at 08 LT) in the Southern hemisphere at high solar activity. But on certain days at any solar activity the longitudinal effect magnitude can reach 9–10° even at night. The shape of the longitudinal effect was found to differ significantly in two hemispheres. In the Northern hemisphere the trough is usually closest to the pole in the eastern (American) longitudinal sector, and in the Southern hemisphere the trough is closest in the western (Eurasian) longitudinal sector. The magnitude and shape of the longitudinal effect is also different during low and high solar activity. The Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere (GSM TIP) simulations demonstrate that during low solar activity, the longitudinal variations of the daytime trough position is mainly determined by longitudinal variations of the ionization function, formed due to the longitudinal variations in the solar zenith angle and the atomic oxygen density distribution. The longitudinal variations of the nighttime trough position is formed by the longitudinal variations in ionization of precipitating auroral particles, neutral atmosphere composition, and electric field.
The aims of this work are to analyze the changes in the world power industry during the time after the adoption of the United Nations Framework Convention on Climate Change of 1992 and to assess the ...extent to which the commitments of the Kyoto Protocol of 1997 have been met and evaluate the prospects of implementing the tasks of the Paris Agreement of 2015. Based on data on the production and consumption of various kinds of energy and the emissions of greenhouse gases, primarily carbon dioxide, in 1990–2017, changes in the structure of the global energy consumption, trends in electric power generation, and the influence of different factors on the carbon dioxide emissions in power-generating enterprises are investigated. It is shown that the power industry, which is the main source of anthropogenic greenhouse gases (GHGs), is the most inertial branch of the economy in terms of its contribution to the reduction in GHG emissions. Thus, in the first 2008–2012 commitment period of the Kyoto Protocol, GHG emissions in the state parties to the protocol decreased by 7.6% compared the base year, while other GHG sources reduced the emission by 18%. The corresponding figures for the following 2013–2017 commitment period were 10.6 and 17.1%, respectively. The maximum reduction in the carbon dioxide emissions in the power industry resulted from an increase in the global average efficiency of the thermal power stations from 32% in 1990 to 36% in 2017; as a consequence, the cumulative decrease in the CO
2
emissions in the world during the 1990–2017 period was approximately 22 billion t. The increase in the electric power generation at HPPs and NPPs resulted in a reduction in GHG emissions by 16.7 and 10.7 billion t, respectively. The substitution of coal and fuel oil by gas at thermal power stations facilitated reducing the emissions by 5.2 billion t, while the use of renewable energy sources for generation of electric energy resulted in a reduction of 1.1 billion t. The contribution of the carbon capture and storage technologies amounting to only 0.2 billion t is not noticeable so far.
The influence of brackish artesian waters used for drip irrigation of gardens in the Sivash area of Crimea on the composition of salts and exchangeable cations of two soils located at different ...distances from Lake Sivash has been studied. Observations of the dynamics of mineralization and salt composition of irrigation water during three years (2019–2021) indicate that this water is neutral (pH 6.88–7.43) and slightly to moderately saline (1.5–3.4 g/L) with variable chemical composition of soluble salts: calcium chloride—sodium sulfate–chloride—calcium sulfate. Water salinity increases with time and towards Lake Sivash. The high contents of chlorides (15–25 meq/L), sulfates (6–31 meq/L), and Ca
2+
(14–26 meq/L) and a stable and relatively low concentration of
(3 meq/L) are characteristic of the irrigation water. Local moistening of soils during drip irrigation has favored local slight sulfate–chloride and chloride magnesium–sodium salinization in a layer of 0–60 cm, which is toxic for fruit crops. The total salt content in the soil has a pulsating regime: it increases in the fall after the irrigation season and decreases in the spring due to salt leaching by atmospheric precipitation deep into the profile and to the sides from tree rows. Slightly brackish water of this salt composition with a salinity of 1.5–2.7 g/L and SAR 2–4 has led to solonetzization of Haplic Kastanozem with an increase in the content of exchangeable Na
+
up to 6–8% of the sum of exchangeable cations. Irrigation water with salinity above 3 g/L and SAR 3–7 increases the content of exchangeable Na
+
up to 9–10% of the sum of exchangeable cations in a slightly solonetzic Luvic Kastanozem. Under conditions of progressive salinization of irrigation water and soils, it is necessary to continue monitoring of the salt composition and ion exchange processes in irrigated soils.
Earlier the model studies demonstrated that equatorial F2 layer stratification and an additional F3 layer appear in simulation results only by taking into account zonal electric field. Nanan Balan ...concluded that F3 layer forms during morning–noon period, when the ionization processes dominate over chemical losses and when there is a large upward flow of ionization due to the combined effect of E×B drift and neutral wind. Our recent studies specify that during geomagnetic storms, a non-uniform in height zonal electric fields at the geomagnetic equator form the additional layers above regular F2 layer. In this paper, we consider the formation mechanism of the additional layers in a near-equatorial ionosphere during quiet geomagnetic conditions. This study presents the comparison of the GSM TIP numerical simulations and observation data of Intercosmos-19 satellite. We confirmed that the non-uniform in height vertical plasma drifts form the additional layers at the geomagnetic equator.
► We confirmed that the non-uniform in height vertical plasma drifts form the additional layers. ► Our mechanism can explain F3 layer occurrence at different LT epochs. ► The additional layers are formed above regular F2 layer between two EIA crests. ► The occurrence of the multilayer pattern in electron density profile depends on season and solar activity.
For the first time we developed an empirical model of the main ionospheric trough, MIT, for quiet (Kp=2) nighttime (18:00–06:00 LT) winter conditions in the Northern and Southern hemispheres for all ...levels of solar activity. The model consists of two parts: (1) the MIT position model in terms of geographical latitude and longitude; (2) the MIT shape model in terms of the latitudinal–longitudinal foF2 variations in the range of 45–75°N latitudes in the Northern hemisphere and of 40–80°S in the Southern hemisphere. Thus, an empirical model of the quiet nighttime subauroral ionosphere has been developed. To construct this model the Interkosmos-19 and CHAMP satellites data have been used. The in-situ Ne measurements at the CHAMP heights were transformed to the electron density at F2 layer peak height (i.e. to NmF2 and then to foF2). In the frame of the model the diurnal and longitudinal variations in the MIT minimum position were revealed and studied in detail. Also the longitudinal and latitudinal variations in foF2 in the MIT region were investigated. Accuracy of the model was tested according to the ground-based ionospheric stations data. It is shown that the constructed model much more adequately reproduces the variations in the winter nighttime subauroral ionospheric structure, including the MIT position and shape variations, than the International Reference Ionosphere model (IRI-2012). The online version of the MIT model is available on the IZMIRAN website: http://www.izmiran.ru/ionosphere/sm-mit/ for free using and more detailed testing.
•Empirical model of the main ionospheric trough (MIT) for quiet nighttime winter conditions in the both hemispheres for all levels of solar activity was developed. The model consists of two parts: MIT position model in terms of geographical latitude and MIT shape model in terms of the foF2 maps. Interkosmos-19 and CHAMP data were used. The model is available on: www.izmiran.ru/ionosphere/sm-mit/.
The measurements of GPS signal delays show that the local areas of increased/decreased Total Electron Content (
TEC) of the ionosphere can be observed before strong earthquakes. The main possible ...cause of these
TEC disturbances is the vertical plasma drift under the action of zonal electric field. The spatial pattern of electric potentials for such electric field was proposed. The model calculations were done to investigate the efficiency of the proposed mechanism. The calculation results revealed the agreement with
TEC variations observed before strong earthquakes and showed that the equatorial electrojet variations can be considered as precursors of earthquakes.
We studied the main morphology of the formation of summer ionospheric anomalies which includes the Weddell Sea Anomaly (WSA) and the Yakutsk Anomaly (YA) in terms of positive night-to-day foF2 ...differences. For this purpose, we have for the first time used topside sounding (Interkosmos-19 satellite) and ground-based (ionosonde) data as well as results from an empirical model (International Reference Ionosphere – IRI) and from a first-principles model (Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere – GSM TIP). The main spatial morphological characteristics of the WSA and YA are similar which points to a common cause for their occurrence. Our preliminary GSM TIP model results showed that the foF2 values at nighttime are greater than at daytime due to: (1) the horizontal plasma transport due to electromagnetic drift; (2) the vertical component of plasma transport along the geomagnetic field lines via meridional neutral wind; (3) the distribution of the neutral composition of the thermosphere.
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