scholarly journals Study heat exchange in porous structures

2022 ◽  
Vol 1216 (1) ◽  
pp. 012011
Author(s):  
A A Genbach ◽  
H I Beloev ◽  
D Yu Bondartsev ◽  
N A Genbach
Keyword(s):  
Heat Exchange ◽  
High Reliability ◽  
Thermal Power ◽  
Porous Structures ◽  
Cooling Systems ◽  
Power Plant Equipment ◽  
Heat Exchange Surface ◽  
Plant Equipment ◽  
Heat Loads ◽  
Exchange Surface

Abstract This paper shows the problem with heat exchange depending on units of thermal power plant equipment. The type of structures is determined and the heat flow for different pressures is proposed. Studies are developed for the condition of the heat exchange surface. Devices with porous coatings eliminate the development of cracks in the components and units of TPP equipment have been suggested. The research is applicable to gas turbine units of TPP. Comparable capillary-porous and flow systems have high reliability, but the former allowed the reduction of coolant consumption dozens up to 80 times. The results show that at higher heat loads it is suitable to use in porous surfaces to control the cooling surface. Evaluation of capillary-porous structures has shown their advantages over traditional cooling systems.

scholarly journals Heat transfer in laser passive and deformable mirrors

2021 ◽  
Vol 2088 (1) ◽  
pp. 012042
Author(s):  
E Leonov ◽  
A Chernykh ◽  
Yu Shanin
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Deformable Mirrors ◽  
Optical Surface ◽  
Optical Elements ◽  
Cooling Systems ◽  
Highly Efficient ◽  
Heat Exchange Surface ◽  
Exchange Surface

Abstract In work, the possibilities of using uncooled and cooled optical elements (including laser passive and deformable mirrors) with an increase in the power of laser facilities are analyzed. To increase the permissible light loads acting on the optical elements, the use of highly efficient cooling systems with minichannels (coplanar and multi-tiered), providing a high compactness of the heat exchange surface and the intensification of heat transfer, is considered. The advantages and efficiency of the proposed cooling systems for reducing the displacement of the optical surface of the mirror due to bending are estimated.

Summary of heat transfer processes and their comparative evaluation for capillary porous coatings in power plants

2019 ◽  
Vol 12 (1) ◽  
pp. 29-35
Author(s):  
A. A. Genbach ◽  
D. Yu. Bondartsev ◽  
A. Y. Shelginsky
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Power Plants ◽  
Cooling System ◽  
Heat Pipes ◽  
High Heat ◽  
Porous Structures ◽  
Heat Exchange Surface ◽  
Exchange Surface ◽  
Thin Fi Lm

The crisis of heat exchange at boiling of water in porous structures used for cooling of heat-stressed surfaces of various aggregates is investigated. The study refers to thermal power installations of power plants. The experiments were carried out on a stand with heat supply from an electric heater. Cooling of heat-exchange surfaces was performed by water supply to porous structures with diff erent cell sizes. It is shown that in porous cooling systems of elements of heat and power plants processes of fl uid boiling take place, and at high heat fl ows it is possible to approach a crisis situation with overheating of the heat-exchange surface. The heat exchange processes are described, the infl uence of thermophysical properties of heat exchange surface is shown, and optimal sizes of porous structure cells are determined. A calculated equation is obtained for determining the critical heat fl ux at high pressures. The calculation of the critical load with respect to the examined porous structures was carried out with taking into account the underheating and fl ow rate, from which it follows that the underheating of the liquid enables to expand slightly the heat transfer capabilities in a porous cooling system. The experimental data of the investigated capillary porous cooling system operating under the joint action of capillary and mass forces are generalized, and its characteristics q=f(ΔT) are compared with boiling in large volume, heat pipes and thin-fi lm evaporators. The limits of diff erent capillary-porous coatings are given. High heat transfer boosting is provided by combined action of capillary and mass forces and has advantages in comparison with boiling in large volume, thin-fi lm evaporators and heat pipes. It is shown that the results of theoretical calculations conform well with experimental data.

scholarly journals Science-Based Procedure for Designing Tubular Porous Cooling Systems for Thermal Power Plant Equipment Components

2019 ◽  
pp. 89-106
Author(s):  
A.A. Genbach ◽  
D.Yu. Bondartsev
Keyword(s):  
Thermal Conductivity ◽  
Power Plant ◽  
Thermal Power Plant ◽  
Thermal Power ◽  
High Heat ◽  
Short Exposure ◽  
Cooling Systems ◽  
Heat Flows ◽  
Power Plant Equipment ◽  
Plant Equipment

We investigated critical heat flux phenomena in metallic and porous structures characterised by low thermal conductivity. These structures are used to cool various thermal power plant equipment; their operation involves both gravity and capillary forces. The paper describes the failure mechanism in metallic steam generator surfaces and poorly thermally conductive low-porosity coatings made of natural mineral media (such as granite). We determined how heat flows depend on their duration and penetration depth of thermal disturbance. Tubular porous systems are less bulky and feature high intensity, higher thermal conductivity and reliability. We show that for granite coatings the maximum thickness of the particles detached due to compression forces is (0.25...0.3)·10--2 m. The compression curve sections that govern detachment of particles larger than 0.3·10--2 m are shadowed by the melt curve for high heat flows and short exposure times and by the tension curve in the case of low heat flows and short periods of time. The investigation should help us to design porous coatings usable in cooling systems.

Temperature control in a chemical reactor through variable area of the heat transfer surface. Simulation analysis

1982 ◽  
Vol 47 (2) ◽  
pp. 430-445
Author(s):  
Josef Horák ◽  
Zina Valášková
Keyword(s):  
Heat Exchange ◽  
Simulation Analysis ◽  
Batch Reactor ◽  
Chemical Reactor ◽  
Rate Of Change ◽  
Action Variable ◽  
Heat Exchange Surface ◽  
Relay With Hysteresis ◽  
Exchange Surface

An algorithm has been developed and on a mathematical model analyzed to stabilize the reaction temperature of a batch reactor. The reaction has been a zero-order one and the reactor has been operated in a instable operating point. The action variable is the heat exchange surface whose area is increased if the temperature is above, or decreased if the temperature is below the set point. The following two-point regulators have been studied: An ideal relay, a relay with hysteresis and an asymmetric PD relay. The effect has been discussed of the parameters of the regulators on the quality of regulation. Stability analysis has been made of the stationary switching cycles and the domains of applicability have been determined for individual regulators with respect to the rate of change of the area of heat exchange surface.

Thermodynamic Estimate of Minimal Dissipation for Heat Exchange System

2008 ◽  
Author(s):  
Andrei A. Akhremenkov ◽  
Anatoliy M. Tsirlin ◽  
Vladimir Kazakov
Keyword(s):  
Heat Exchanger ◽  
Heat Exchange ◽  
Heat Load ◽  
Point Of View ◽  
Exchange System ◽  
Heat Exchange System ◽  
Heat Exchange Surface ◽  
Minimal Dissipation ◽  
The Difference ◽  
Exchange Surface

In this paper we consider heat exchange system from point of view of Finite-time thermodynamics. At first time the novel estimate of the minimal entropy production in a general-type heat exchange system with given heat load and fixed heat exchange surface is derived. The corresponding optimal distribution of heat exchange surface and optimal contact temperatures are also obtained. It is proven that if a heat flow is proportional to the difference of contacting flows’ temperatures then dissipation in a multi-flow heat exchanger is minimal only if the ratio of contact temperatures of any two flows at any point inside heat exchanger is the same and the temperatures of all heating flows leaving exchanger are also the same. Our result based on those assumptions: 1. heat transfer law is linear (17); 2. summary exchange surface is given; 3. heat load is given; 4. input tempretures for all flows are given; 5. water equivalents for all flows are given.

Computer simulation of the reliability of the heat exchange surface of the steam turbine condenser

2022 ◽  
pp. 1748006X2110672
Author(s):  
Krzysztof Bernard Łukaszewski
Keyword(s):  
Heat Exchange ◽  
Steam Turbine ◽  
Cooling Water ◽  
Operating Conditions ◽  
Time Varying ◽  
Turbine Condenser ◽  
Heat Exchange Surface ◽  
Steam Turbine Condenser ◽  
The Relationship ◽  
Exchange Surface

The aim of the article is to demonstrate the relationship between the adaptive regulation of the heat exchange surface to specific operating conditions of a steam turbine condenser and the reliability and availability of this surface in a specific period of time. The article exemplifies the relationship between the settings of the condenser heat exchange surface and the resulting changes in the reliability structures of this surface. The method of creating a mathematical model of reliability estimation, which is characterized by the variability of the reliability structures of the heat exchange surface in relation to specific operating conditions in a specific period of time, was indicated. Then, exemplary simulations of the adaptation of reliability structures of specific pipe systems constituting the condenser’s heat exchange surface to specific processes of operation of this condenser are presented. The simulations refer to the time-varying thermal loads of the condenser, the time-varying mean thickness of the sediments, and changes in the temperature of the cooling water at the point of its intake over time. The adaptation of certain reliability structures consists in the adaptation of specific systems of pipes through which the cooling water flows to the currently existing operating conditions of the condenser in order to maintain the desired reliability of the heat exchange surface for a specified time. This is done by enabling or disabling the flow of cooling water through a given number of pipes in specific systems under given operating conditions. On the basis of computer simulations, the reliability functions, and the availability functions of the subsystem under consideration were estimated.

scholarly journals About mathematical modeling of aerodynamic characteristics in devices with a leakage of the impact systems of plane-parallel streams on the heat exchange surface

2018 ◽  
Vol 170 ◽  
pp. 03024
Author(s):  
Larisa Haritonova ◽  
Valery Azarov ◽  
Igor Stefanenko
Keyword(s):  
Heat Exchange ◽  
Heat Exchangers ◽  
Aerodynamic Resistance ◽  
Aerodynamic Characteristics ◽  
Plane Parallel ◽  
Heat Exchange Surface ◽  
Parallel Streams ◽  
The Impact ◽  
The Mathematical Model ◽  
Exchange Surface

The article is devoted to the development of the general aerodynamic theory in case of a leakage by the systems of plane-parallel impact jets on the plane heat exchange surface [1-2]. An analytical generalization of data on aerodynamic resistance with the blowout of flat surface by the system of the plane-parallel impact jets was implemented. These data were obtained as a result of the application of mathematical theory of planning an experiment. The equations of regression are the mathematical model of process. Functional dependences between the constructive factors and the regime parameters of these first obtained experimental dependences on aerodynamic resistance in the jet heat exchangers with the leakage of air in the form of the system of plane-parallel jets were established. Results of work can be used in developing of different methods of calculation for various new designs of highly effective heat exchangers or their optimization for various branches.

Sign in / Sign up

Export Citation Format

Share Document