Allam proposed to realize problem of CO2 emissions by using supercritical CO2 cycle as working fluid with heating by carbon fuel burning in pure oxygen and then pumps CO2 into underground volumes remaining after oil production.Interest in the Allam cycle shows readiness for technological difficulties and high costs for combating CO2 accumulation in atmosphere. The formic acid cycle begins with the conversion of CO2 from the atmosphere or from flue gases to an aqueous solution and the electrochemical reduction of CO2 into formic acid. Formic acid is a convenient and safe energy storage for fuel cells, since the electrochemical process is reversible. In the reverse process (oxidation), the released CO2 can be immediately immobilized and further buried as a component of the building foam concrete. The formic acid cycle can serve as a "green" alternative to the dominant oil cycle of basic chemical production. It should be noted that even if the task of combating CO2 emissions and global warming will be no longer relevant, the value of the formic acid cycle will be preserved, since it solves a broader spectrum of tasks for the ecologization of energy generation and organic chemistry.

The article presents the results of modeling the process of operation of seamless hotextruded pipes with helical inner ribbing of the inner surface. The modeling was carried out in the CAD software SolidWorks using the integrated calculation module Flow Simulation. After modeling and finding the coefficients of the linear regression function, the corresponding equations were obtained for calculating the hydrodynamic and kinematic parameters of the water-steam mixture flow.

Reheaters (LPR-3 and LPR-4). Heat exchange surfaces were made of welded or all-welded tubes of 08Х18Н10Т stainless steel (AISI 321) with a diameter of 16х1mm. LPR-3 and LPR-4 have identical design. The heating steam moves horizontally between the seven horizontal partitions and crossing successively vertical tubes of the second running and then the main condensate first running, condenses on the vertical heat exchange tubes and flows down along the tubes surface. The pressure in the tubes is about 1.2 MPa, and the pressure of the heating steam is 0.3 MPa. After the ban on the use of copper-containing materials in the second circuit of nuclear power plants, their gradual replacement began with steel ones. After a relatively recent installation of stainless steel tubes in LPR-3, significant damages of the tubes occurred with a violation of their tightness. Overwhelming majority of the damaged tubes were along the first running of the heated water and inside the three lower horizontal sections. The form of the damages appeared to be of a cavitation character, although the distribution of temperature and pressure did not completely satisfy this statement. It was shown that the presence of such effects can be explained using the model of internal non-stationary nature of two-phase flows proposed in the NPO CKTI JSC. Relative values of local pressure fluctuations correspond to the maximum of the density (or quality) fluctuations and can be about 0.03-0.05 MPa. Thus, the pulsations of local saturation temperature can reach 5-7°C and cause the effects of steam bubbles formation and their collapse in the condensate near the partitions. At the same time, it is possible to explain the location of the injuries and formulate some proposals for weakening or even elimination the observed effects. Although the described effects were found at NPP, but they, of course, can occur at conventional Power Plants.

The article is devoted to numerical simulation of heat transfer processes occurring during the flow of a coolant in seamless hot-extrusion pipes with a spiral inner fin surface (TMK-IRS). A description of the numerical modeling technique is given along with the interface of the program used to create different types of internal fins. Thermohydraulic analysis of finned pipes for transient, turbulent and laminar flow regimes has been carried out. An estimate of the critical Reynolds number characterizing the transition to a turbulent regime, the nature of the transient flow regime in comparison with other classical cases is given.