Determination of the Coefficients of Heat Transfer and Friction in Supercritical-Pressure Nuclear Reactors with Account of the Intensity and Scale of Flow Turbulence on the Basis of the Theory of Stochastic Equations and Equivalence of Measures

2017 ◽  
Vol 90 (6) ◽  
pp. 1288-1294 ◽  
Author(s):  
A. V. Dmitrenko
Keyword(s):  
Heat Transfer ◽  
Nuclear Reactors ◽  
Stochastic Equations ◽  
Supercritical Pressure ◽  
Equivalence Of Measures ◽  
Flow Turbulence

Progress in Developing an Improved Empirical Heat Transfer Equation for Use in Connection With Advanced Nuclear Reactors Cooled by Water at Supercritical Pressure

2009 ◽  
Author(s):  
J. Derek Jackson
Keyword(s):  
Heat Transfer ◽  
Nuclear Reactors ◽  
Supercritical Pressure ◽  
Thermal Design ◽  
Mean Flow ◽  
Flow Acceleration ◽  
Design Procedures ◽  
Structure Changes ◽  
Physically Based ◽  
Semi Empirical

Consideration of advanced power plant such as nuclear reactors cooled by water at pressures above the critical value has stimulated a renewed interest in heat transfer to supercritical pressure fluids. Severe deterioration in the effectiveness of heat transfer can be encountered as a result of the extreme dependence on temperature of the physical properties of such fluids, particularly near the pseudocritical temperature where their molecular structure changes from being liquid-like to gaseous. This deterioration arises mainly as a result of the non-uniformity of density, which can lead to significant influences of bulk flow acceleration and fluid buoyancy. A good physical understanding has been arrived at of the mechanisms by means of which such influences can modify the mean flow and turbulence fields and thereby the advection and turbulent diffusion of heat and effectiveness of heat transfer. However, this progress in understanding the physics has so far not resulted in such effects being reliably accounted for in the empirical equations which are available for thermal design. With a view to addressing this matter, the author has recently attempted to update and improve an existing physically-based semi-empirical model of variable property heat transfer. The aim has been to combine it with a soundly-based empirical forced convection equation to extend the applicability and reliability of currently available thermal design procedures. In the present paper, progress in validating this approach and optimising the performance of the extended equation is reported.

scholarly journals Determination of Critical Reynolds Number for the Flow Near a Rotating Disk on the Basis of the Theory of Stochastic Equations and Equivalence of Measures

Fluids ◽  
2020 ◽  
Vol 6 (1) ◽  
pp. 5
Author(s):  
Artur Dmitrenko
Keyword(s):  
Reynolds Number ◽  
Power Plants ◽  
Critical Reynolds Number ◽  
Thermal State ◽  
Rotating Disk ◽  
Stochastic Equations ◽  
Analytical Dependence ◽  
Steam Turbines ◽  
Equivalence Of Measures

The determination of the flow regime of liquid and gas in power plants is the most important design task. Performing the calculations based on modern calculation methods requires a priori knowledge of the initial and boundary conditions, which significantly affect the final results. The purpose of the article is to present the solution for the critical Reynolds number for the flow near a rotating disk on the basis of the theory of stochastic equations of continuum laws and equivalence of measures between random and deterministic motions. The determination of the analytical dependence for the critical Reynolds number is essential for the study of flow regimes and the thermal state of disks and blades in the design of gas and steam turbines. The result of the calculation with using the new formula shows that for the flow near a wall of rotating disk, the critical Reynolds number is 325,000, when the turbulent Reynolds is 5 ÷ 10 and the degree of turbulence is 0.01 ÷ 0.02. Therefore, the result of solution shows a satisfactory correspondence of the obtained analytical dependence for the critical Reynolds number with the experimental data.

INFLUENCE OF HEAT TREATMENT OF MOUNTAIN MASSIVE ON TEMPERATURE MODE OF GEOTHERMAL CIRCULATION SYSTEM

2018 ◽  
pp. 44-50
Author(s):  
Yu. P. Morozov
Keyword(s):  
Heat Transfer ◽  
Operating Time ◽  
Fluid Motion ◽  
Coolant Temperature ◽  
Circulation System ◽  
Thermal Processes ◽  
Temperature Mode ◽  
Heat Influx ◽  
Stationary Heat Transfer

Based on the solution of the problem of non-stationary heat transfer during fluid motion in underground permeable layers, dependence was obtained to determine the operating time of the geothermal circulation system in the regime of constant and falling temperatures. It has been established that for a thickness of the layer H <4 m, the influence of heat influxes at = 0.99 and = 0.5 is practically the same, but for a thickness of the layer H> 5 m, the influence of heat inflows depends significantly on temperature. At a thickness of the permeable formation H> 20 m, the heat transfer at = 0.99 has virtually no effect on the thermal processes in the permeable formation, but at = 0.5 the heat influx, depending on the speed of movement, can be from 50 to 90%. Only at H> 50 m, the effect of heat influx significantly decreases and amounts, depending on the filtration rate, from 50 to 10%. The thermal effect of the rock mass with its thickness of more than 10 m, the distance between the discharge circuit and operation, as well as the speed of the coolant have almost no effect on the determination of the operating time of the GCS in constant temperature mode. During operation of the GCS at a dimensionless coolant temperature = 0.5, the velocity of the coolant is significant. With an increase in the speed of the coolant in two times, the error changes by 1.5 times.

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