Intensity Of Heat Exchange Research Articles

Lagrangian analysis on mechanism of forced convection heat transfer control for cylinder via deep reinforcement learning

Forced convection heat transfer plays a vital role in engineering; however, its control presents significant complexity. In this paper, a closed-loop deep reinforcement learning framework is introduced to optimize cooling tasks in a heat exchanger, where a cylindrical heat source is immersed in a narrow cavity. The online learning deep Q-networks (DQN) algorithm is implemented, and an offline learning conservative Q-learning soft actor-critic (CQL-SAC) algorithm is first proposed to learn based solely on preexisting databases without interacting with the environment. Taking the continuous blowing mode as the baseline, the CQL-SAC control obtains a temperature reduction of 49.1% greater than that under the optimal human control and consumes only 0.53% of the time required by online learning. While the DQN control achieves the best cooling performance, with a temperature reduction exceeding that of the optimal human control by 91.4%. The underlying mechanisms are analyzed. Particle tracking technology and Lagrangian coherence structures (LCS) are employed to identify regions of sufficient heat exchange and precisely map from where a cold particle can be captured to undergo sufficient heat exchange or swiftly escapes with inadequate heat exchange. The mechanism of the enhanced cooling effect under the DQN control is clarified from a particle capturing and escaping perspective. The greater overlap between the cold particle capture region and hotspots correlating with the more saddle points of the LCS within this region indicates more intense heat exchange in areas closer to hotspots, thus resulting in better cooling performance.

METHODOLOGY OF EXPERIMENTAL STUDY OF LOCAL CONDITIONS OF NON-STATIONARY HEAT TRANSFER

The task of studying the conditions of heat exchange of a sprayed liquid – water with different concentrations of surfactants with a high-temperature surface has defined a number of problems that need to be solved. Two tasks: development of means for experimental study of non-stationary local conditions of heat exchange of a high-temperature surface with a sprayed liquid, taking into account the possibility of implementing a change in the level of determining factors in the range corresponding to their real values ​​in full-scale energy and metallurgy facilities, and the task of choosing a method for identifying the boundary conditions of heat exchange, from our point of view, are the main ones. Analysis of scientific publications and our own research have allowed us to establish that the central factor influencing local heat exchange conditions is the local irrigation density, which would be one of the factors for developing effective cooling systems, or for determining the thermal state of an object under various external influences. The next objective of the study is to investigate the intensity of heat exchange as a function of underheating of the sprayed liquid – water with different concentrations of surfactants at different local irrigation densities and surface temperatures. Since we are considering a multifactorial problem, modern requirements of the theory of experimental planning have made it possible to develop a methodology for experimental study of local conditions of non-stationary heat exchange, which will allow us to conduct a study of the boundary conditions of heat exchange as a function of the interrelated influence of the irrigation density, surface temperature, velocity and angle of impingement of the sprayed liquid onto the surface. The measurement technique we have developed will allow us to obtain reliable research results. Solving the inverse problem of heat conduction will allow us to establish the degree of influence of almost all factors noted as determining. It is obvious that in this case, studying the boundary conditions of heat exchange as a function of the speed of movement of a high-temperature surface results in a large independent problem.

EXPERIMENTAL STAND FOR STUDYING LOCAL CONDITIONS OF TRANSIENT HEAT TRANSFER

An experimental setup has been designed to study local conditions of non-stationary heat exchange during cooling of a high-temperature surface with a sprayed liquid: from nozzles of various modifications (including sprayers); water-air; steam-air; steam-water; superheated liquid; water with different concentrations of surfactants. An analysis of scientific sources has determined a research methodology that will allow the study of the influence of irrigation density, surface temperature, degree of liquid underheating, its velocity and angle of flow onto the surface, taking into account the possibility of implementing a change in the determining factors in the range of their corresponding real values ​​in natural energy and metallurgy facilities and the task of selecting a method for identifying the boundary conditions of heat exchange. We have not come across any studies of heat exchange intensity as a function of underheating of sprayed liquid – water with different concentrations of surfactants at different local irrigation densities and surface temperatures in scientific publications. Therefore, these studies, as well as the development of effective cooling systems or determination of the thermal state of objects under various external influences, are of primary importance to us. In order to implement our planned research program, in addition to developing a method for identifying the boundary conditions of heat exchange, it was necessary to solve a number of special problems associated with determining the operating parameters of the cooling medium. These include the local irrigation density and the velocity of the dispersed medium at the surface of the thermal probe. For reliable determination of local irrigation flow rate, as well as determination of the dispersed composition of drops, the pulse counting method, which has the possibility of practical implementation in our country, should be used. To determine local conditions of non-stationary heat exchange, we have developed a scheme for measuring the EMF of temperature detectors installed in the body of the rod of the thermal probe, and also selected high-speed digital recording equipment. The solution of the inverse problem of heat conduction will allow us to establish the degree of influence of practically all factors indicated as determining ones.

Gyroid Lattice Heat Exchangers: Comparative Analysis on Thermo-Fluid Dynamic Performances

In recent years, additive manufacturing has reached the required reliability to effectively compete with standard production techniques of mechanical components. In particular, the geometrical freedom enabled by innovative manufacturing techniques has revolutionized the design trends for compact heat exchangers. Bioinspired structures, such as the gyroid lattice, have relevant mechanical and heat exchange properties for their light weight and increased heat exchange area, which also promotes the turbulent regime of the coolant. This work focuses its attention on the effect of the relevant design parameters of the gyroid lattice on heat exchange performances. A numerical comparative analysis is carried out from the thermal and fluid dynamic points of view to give design guidelines. The results of numerical analyses, performed on cylindrical samples, are compared to the experimental results on the pressure drop. Lattices samples were successfully printed with material extrusion, which is a low-cost and easy-to-use metal AM technology. For each lattice sample, counter pressure, heat exchange, and turbulence intensity ratio are calculated from the numerical point of view and discussed. At the end, the gyroid lattice is proven to be very effective at enhancing the heat exchange in cylindrical pipes. Guidelines are given about the choice of the best lattice, depending on the considered applications.

Heat transfer characteristics of buried pipes under groundwater seepage in Karst regions

Utilising geothermal energy through ground-source heat pump (GSHP) systems is a viable option. Karst regions, renowned for their abundant geothermal resources and complex geological structures, present a unique challenge owing to the presence and fluctuations of groundwater, which significantly alter the operational environment of GSHPs. Therefore, it is crucial to explore the mechanisms and performance of GSHPs in such areas. Based on actual Karst geological structures and using similarity theory, a multi-layer experimental model of a ground heat exchanger (GHE) was established in a laboratory. To enhance the GSHP performance, a forced seepage plan for shallow soil layers was proposed. Then, a controlled variable method was employed to investigate the impact of aquifer-related groundwater seepage factors on the heat transfer performance of buried pipes. Thresholds for groundwater velocity and temperature that enhanced thermal performance were identified. Groundwater seepage shortens the recovery time of the temperature field in geotechnical materials and influences the heat exchange intensity based on the flow temperature. This study focuses on a layered heat transfer model and proposes a relationship between aquifer thickness and geotechnical heat transfer, providing theoretical support for the application and optimisation of GSHP systems in Karst regions.

ВЛИЯНИЕ ТЕПЛОФИЗИЧЕСКИХ СВОЙСТВ ТЕПЛОНОСИТЕЛЕЙ НА ПРОЦЕСС ТЕПЛООБМЕНА В ЗАМКНУТЫХ ДВУХФАЗНЫХ ТЕПЛОПЕРЕДАЮЩИХ СИСТЕМАХ

The analysis of low-temperature heat carriers (ozone-safe freons) properties for use as heat carriers in thermosyphon elements has been carried out. The most significant thermophysical properties of heat carriers that affect the intensity of heat exchange in closed two-phase heat-transfer devices have been determined. The calculation of the FOM quality index of the heat carrier for the selected freons is given. The dependence of the thermal resistance of the thermosyphon element on the supplied heat load is established. Recommendations are given for choosing a heat carrier for two-phase heat-transfer elements

Configuration method for medium-deep ground source heat pump system considering renewable energy consumption and smart grid interaction

Medium-deep ground source heat pump (GSHP) systems have the advantages of low carbon, high heat exchange intensity, good thermal storage capacity, and intermittent operation characteristics, which are conducive to renewable energy consumption and grid demand response. The source-side parameters affect the configuration of underground borehole engineering, heat pump units, and other equipment. However, current research mainly focuses on the underground heat exchanger modeling, underground heat exchange, and system operation control, while there are few studies on multi-factor ground source-side parameter design and optimal configuration. In this study, the indicator analyzing the unsteady features and thermal balance state of medium-deep geothermal resources was introduced, and the source-side water temperatures were optimized based on the dynamic characteristics of the geothermal and building sides. A simulation configuration methodology for the source-side flow rate and storage capacity was developed considering the electricity prices, life-cycle cost (LCC), and grid interaction. The optimization of the ground source-side design temperature, flow rate, and capacity parameters of residential and office building heating scenarios were analyzed in northern China, respectively. The results showed that the borehole inlet and outlet temperature can be designed to 5.5 °C/17.5 °C under the annual sustainable state, and the optimal flowrate can be set to 65.77 m3/h, to achieve the lowest cost and highest heating season guarantee rate for the residential scenario. For the office building with optimal system and storage capacity, the average annual LCC is 192,000 yuan/year, with the cumulative peak shaving of 55.8 %, and an increase of 103.3MWh renewable electricity consumption.

Lattice Boltzmann study on magnetohydrodynamic double-diffusive convection in Fe3O4–H2O nanofluid-filled porous media

Magnetohydrodynamic double-diffusive convection (MHD-DDC) in porous media has substantial significance in broad applications. However, due to the complexity of the DDC problems involving nanofluid, porous media, and external magnetic field at the same time, the MHD-DDC in nanofluid-filled porous media has rarely been studied. Besides, previous research on MHD convection problems usually focuses on magnetic fields or nanofluid effects. Effects of the thermal-to-mass properties, including the buoyancy radio (Br) and Lewis number (Le), on MHD-DDC problems have rarely been studied, seriously limiting the understanding and regulation of heat and mass transfer. Herein, we numerically study heat and mass transfer in the MHD-DDC within a square cavity containing a nanofluid of Fe3O4–H2O and a porous medium using a lattice Boltzmann method. A series of case studies are carried out to investigate the effects of Br, Le, and the medium porosity (ε) on the velocity, temperature, and nanoparticle concentration. Results indicate that Br determines the rotation pattern of the streamline, while Le and ε can be utilized to regulate the intensity of heat and mass exchange. The results of this paper present a quantitative insight into regulating heat and mass transfer patterns in MHD-DDC problems.

Method of reliability control of thermoelectric systems to ensure thermal regimes

The paper presents the results of research of controllability of the thermoelectric system for ensuring thermal modes of electronic equipment, including a regulator, a cooler, and a component of excess heat removal to the environment. It is shown that for the use of methods of optimization of automatic control systems it is necessary to study the transfer and dynamic characteristics of the object - thermoelectric cooling device with one input and one output. The mathematical model of the thermoelectric cooler of the system of providing thermal modes of a given design is presented, which takes into account the influence of the conditions of interaction of the heat sink with the medium on the main significant parameters, reliability indicators, dynamic and energy characteristics of the single stage cooler. The model is created for the operating range of cooling, level of thermal load, geometry of thermocouple branches, different temperature of the medium, for the characteristic thermal regime of maximum cooling capacity. The results of calculations of the main significant parameters, reliability indicators, dynamic and energy characteristics of the cooler for different medium temperature in the operating temperature range and variation of conditions of heat exchange of the heat sink with the medium are given. It is shown that as the intensity of heat exchange of the heat sink with the medium increases, the temperature difference between the heat sink and the medium decreases. This makes it possible to significantly reduce the relative failure rate, increase the probability of failure-free operation of the thermoelectric cooler and control the reliability indicators of the device of a given design during operation.

Mathematical model of the evaporative condenser for on-site condition simulation

Evaporative condensers (ECs) have been widely adopted in the fields of refrigeration, petrochemicals, etc. owing to the advantages of low water and energy consumption. However, due to the lack of a reliable mathematical model, the energy-saving potential of ECs remains unexplored. To realize thermodynamic performance predictions under on-site conditions, a generic model with 4 characteristic parameters, that could be identified specifically for different ECs, is innovatively proposed in this paper. Taking the refrigeration system of a food factory as a case study, a well-organized data processing method including filtering, screening, and supplementation is established. The processed real-operating data is used for characteristic parameters identification and model validation. Simulations indicate satisfactory transferability and a good agreement between the test and simulated results, with average relative errors of 2.10 % and 2.87 % for the training and test sets, respectively. Based on the proposed model, the overall performance and the working fluids’ thermodynamic state of the EC during operation are investigated carefully. It could be concluded that the air–water mass transfer is the dominating factor in enhancing EC's thermodynamic performance, and air flow shows greater significance than water in improving heat exchange capacity. The heat exchange intensity of the superheating and two-phase zones is similar, while that of the subcooling zone is the lowest, averaging only 37.9 %.

Experimental and numerical investigations into the fabrication of alumina ceramic surface microchannel by electrochemical discharge machining

The electrochemical discharge machining (ECDM) is an advanced and promising technology for fabricating micro structures. This method is effectively applicable for non-conductive hard and brittle materials micromachining, such as glass and ceramics. However, the ceramics high melting point and intense heat exchange effects during microchannel fabrication lead to the easy dissipation of thermal energy and the difficulty in processing. To address this issue and expanded the ECDM processing range. This paper dedicated to the investigation of the material removal mechanism and process characteristics for the alumina ceramic surfaces microchannels preparation. Firstly, this study explained the difference of the ECDM critical applied voltage and gas film generation mechanism by analyzing the volt-ampere characteristic curve of 20 wt% NaOH electrolyte with a tool immersed depth of 2 mm and 10 mm respectively. Then, a thermal removal finite element model (FEM) for ECDM was developed. The heat cumulative and intermittent cooling effects applied on the alumina ceramic surface dominated the materiel removal. Additionally, it can be found that the microchannel machining accuracy and bottom surface quality depended on the Gaussian heat source characteristics, gas film formation mechanism, heat accumulation effect, and temperatures spatial and temporal distribution. And a series of single factor experiments for evaluating the parametric studies such as the effect of discharge frequency, applied voltage, duty ratio and tool feed rate on the fabricated microchannel performance are executed. Finally, the complex three-dimensional structures of cross microchannel grid and zigzag microchannel array with variable depth were successfully fabricated on aluminum oxide ceramic surface. Notably, the results highlighted and enriched the ECDM stability, consistency and applicability for alumina ceramic surface microchannel fabrication.

Моделирование гидродинамики, теплообмена и процесса усреднения гранулированных сред в пневматическом циркуляционном аппарате

The mathematical modeling of hydrodynamics, heat transfer, and averaging of a highly concentrated granular medium in the working area of a vertical pneumatic circulation apparatus is performed. The hydrodynamics of a dense layer of the granular medium is described by a non-Newtonian model with partial slip conditions on solid walls. Such a representation of the granular medium dynamics allows one to approve theoretical calculations with available experimental data for a steady flow in a flat channel. The numerical applicability of the partial slip condition for a non-Newtonian fluid is confirmed by the analytical dependences obtained by the authors for a steady flow in a circular tube and a flat channel, which are transformed into the known analytical formulas under no-slip conditions for a non-Newtonian medium. On the basis of the proposed model, the heat exchange intensity is analyzed when setting the constant heat flux density or the constant temperature on the annular shelves in the apparatus. The intensity of the granular mixture averaging in the bunker with the introduction of additional annular shelves is studied, and the efficiency of granular mixture mixing during rotation is considered. A method for analyzing the mixing of a granular medium in dynamics in each local area of the apparatus is proposed, which is based on the determination of the inhomogeneity coefficient. The results of this study can be used when developing powder technology devices for drying, mixing, dosing, and transport.

EFFECT OF AN INWARD-FACING BAFFLE ON LAMINAR FORCED CONVECTION HEATING ALONG A CYLINDRICAL HORIZONTAL PIPE FOR DIFFERENT NANOFLUIDS

Improving heat exchange intensity is a major goal in the heat exchanger industry. The use of baffles is one of the techniques employed to achieve this goal. In this numerical work, the effect of an inward-facing baffle placed on the wall of a cylindrical horizontal pipe is treated for the case of nanofluid. A sequential analysis is offered to better understand the different effects and their consequences, particularly on the average exchange rate, in addition to somewhat filling the gap identified in the literature for the case of nanofluid with various shapes of the baffle. The study, divided into three parts, begins for 10 ≤ Re ≤ 250 with the case of pipe without baffle, where the water-based nanofluid effect is treated. Three types of nanoparticles (Cu, Al<sub>2</sub>O<sub>3</sub>, and TiO<sub>3</sub>) at volume concentration 0 ≤ φ ≤ 10% are considered. An insulated primary pipe is placed to ensure dynamic establishment at the entrance to the heating pipe assumed to be under imposed temperature. The results showed the clear effects of modifying the kinematic viscosity and thermal diffusivity on the dynamic and thermal lengths, respectively, with the addition of nanoparticles compared to the base fluid. Correlations are proposed for their determination. A heat exchange rate that improves as the volume concentration increases is recorded, particularly for nanoparticles with high thermal conductivity. In the second part, a rectangular baffle is assumed in the heated pipe, where the effects of its position, length and width are analyzed respectively. The results showed a greater interest in placing the baffle close to the entrance, especially if it is longer. In the last part of the work, three other shapes of the baffle are proposed (trapezoidal, triangular, and elliptical). The results confirm that the non-smooth shape of the baffle creates more disturbances in the dynamic and thermal fields, and therefore a greater improvement in the heat exchange rate. For the last two parts, the nanofluid effect remains similar to that recorded for pipe without baffle.

ОСОБЕННОСТИ ПРИМЕНЕНИЯ И РАСЧЕТА МНОГОСЛОЙНЫХ МАТЕРИАЛОВ В ХИМИЧЕСКОЙ АППАРАТУРЕ С ТЕПЛООБМЕННЫМИ УСТРОЙСТВАМИ

The article analyzes the features of the operation of double-layer steels and bimetals, the ad-vantages and disadvantages of these structural materials are indicated. The main problems that are when welding joints made of double-layer steels are listed. The influence of the contact thermal resistance of a heat transfer surface made of multilayer materials on the intensity of heat exchange is considered. An approach to the determination of contact thermal resistance is proposed. The necessity of taking into account the contact thermal resistance in the design of chemical equipment with heat exchange devices made of double-layer steels and bimetals is shown

Numerical Analysis of the Effect of Floor Depression on the Extent of Thermal Interaction with the Ground and Energy Management Using a Vegetable Cold Store as an Example

The thermal interaction between cooling facilities and the ground is most often discussed in terms of the appropriate insulation of building partitions. Unfortunately, there is little information about the potential of using ground thermal accumulation to support the shaping of the microclimate in cooling facilities by embedding them in the ground. This problem is particularly important in the context of striving to reduce the energy demand of buildings. The article discusses a new scientific problem related to the effect of vegetable cold storage floors being recessed into the ground on the surrounding land’s impact range and on its energy management. Validation of the numerical model was performed based on actual year-round field surveys. These surveys were conducted in a free-standing vegetable cold storage facility located in southern Poland. The results of the study allowed us to determine the contribution of the land to the energy balance of the cold storage. A floor recessed into the ground doubled the ground’s contribution to the energy balance. The most important research results showed that the range of thermal impact on the surrounding ground also increased by 2.0 m more than that of a building with the floor located at ground level. An evaluation of the heat flow between the cold storage and the ground in the cases analyzed was also carried out. The analysis of the ground heat exchange balance on an annual basis showed high energy gains of 2055 kWh. The total energy demand for cooling was 1723 kWh, while it was 1204 kWh for heating. The results of the analysis of the heat exchange intensity between the indoor air and the ground showed that the ground contribution accounted for 16.6% of the total energy balance of the cold storage. The highest energy gains from the ground were found in October and amounted to 478 kWh. Due to the summer shutdown, there was an intense heat flow to the ground in July, which amounted to 588 kWh.

Wall friction and heat transfer in turbulent pulsating flow in a square duct

For the first time, a DNS study of pulsating turbulent flows and heat transfer in a square duct is performed. Calculations were carried out at Re=2200 in the current-dominance mode for eight values of the oscillation period and three values of the Prandtl number. It was found that the time-mean friction coefficient in the studied pulsating flows has a lower value than in the stationary flow. The difference reaches −14.7%. The values of the Nusselt numbers are also decreasing, albeit by a smaller amount. The features of secondary flows of Prandtl’s 2nd kind at different phases of the flow oscillations are studied. The profiles of the wall friction stress and heat transfer coefficients and their evolution over time are determined. The time-oscillations of the wall friction are entirely determined by the oscillations of the main flow, being ahead of it in phase by π/4, which coincides with the behavior of laminar pulsating flows at high frequencies. The oscillations in heat transfer on the wall are determined by oscillations in the intensity of turbulent heat exchange, and the change in the latter occurs almost in phase with a change in the volume-average intensity of the transverse velocity fluctuations.

Modeling of voltage-limiting kinetics in two-layer varistor–posistor structures

PurposeThe purpose of this study is to model the dependences of the output voltage, temperature, current and electrical power dissipation of a voltage limiter based on a two-layer varistor–posistor structure on time and analysis the influence of operating modes and design parameters of such a limiter on these characteristics.Design/methodology/approachThe behavior of the limiting voltage, temperature and other parameters of the voltage limiter when an input constant overvoltage is applied is studied by the simulation method. The voltage limiter was a two-layer construction. One layer was a zinc oxide ceramic varistor. The second layer was a posistor polymer composite with a nanocarbon filler of PolySwitch technology.FindingsThe output voltage across the varistor layer decreases and reaches some fixed value related to its breakdown voltage after applying a constant overvoltage to the structure over time. The temperature of the structure increases to some steady state value, while the current decreases significantly. The amplitude of the transient current pulse increases, its duration and energy of the transient process decrease with increasing overvoltage. An increase in the internal resistance of the overvoltage source can cause a decrease in the amplitude and an increase in the duration of transient currents.Originality/valueThe ranges of values for the activation energy of conduction of the varistor layer in weak electric fields, the intensity of heat exchange between the structure under study and the environment are determined to ensure the stable operation of this structure as a voltage limiter. The results obtained make it possible to select the necessary parameters of the indicated structures to ensure the required operating modes of the voltage limiter for various applications.

Experimental Study of Heat Transfer in Bundles of Wavy Pipes of a Hot-water Boiler

The possibility of intensifying heat exchange by using wavy pipes and a membrane between them is considered. It is known that heat exchange in curved pipes and channels of the coil type proceeds more intensively than in straight ones. Increasing the intensity of heat exchange and the use of double-light screens will reduce the dimensions of the boiler unit, which will improve its technical characteristics. For this purpose, experimental studies of heat transfer and resistance in bundles of wavy pipes have been carried out in two flow directions: in the plane of bending of pipes and in the plane perpendicular to the bending of pipes. So, for the flow in the direction of bending pipes, heat transfer and resistance are 9% higher than in bundles of straight pipes. And for a flow perpendicular to the bending plane of wavy pipes, the heat exchange is 13%, and the resistance is 20% higher than in bundles of straight pipes. To further increase heat transfer, it is proposed to use finning by installing membranes between wavy pipes.

Energy load of metal brake frictions elements

Problem. The mathematical description of the temperature field of the rim of the brake pulley can have both an independent value and be the goal of solving a problem (for example, when calculating the time of heating or forced cooling), and also be used as an auxiliary result for solving another, more complex problem (for example, calculating thermoelastic stresses in brake pulley rim). Goal. The purpose of the work is to assess the energy load of metal friction brake elements during the braking process. Methodology. Solving the tasks involved taking into account the fact that the surface-volume temperatures of the polished working surface of the pulley rim are local when assessing the energy load of the belt pulley rim; surface-volume temperatures are always higher than the "pure" volume temperatures of the pulley rim; polished and matte surfaces of the pulley rim are considered. Results. It is proposed that a new approach to the calculation of local thermal stresses, which is implemented for the first time in the theory of friction and wear. The reliability of the obtained results was confirmed experimentally. Originality. The need to find the non-stationary field in the investigated single- ("pad-pulley") and in multi-pair ("tape-pad" and "pad-pulley") friction nodes is proposed. In the last friction nodes, the friction pads act as insulation between the tape, which is freed from the pads, and the working surface of the brake pulley rim. Practical value. The proposed approach made it possible to establish that the magnitude of stresses on the surface of heat release is almost 5 times greater than in the volume of the pulley rim. At the same time, the nature of the influence of the intensity of heat exchange on the magnitude of stresses is the same as during heating, which leads to a decrease in the formation of cracks on the surface of the pulley rim.

ВЛИЯНИЕ КОНТАКТНОГО ТЕРМИЧЕСКОГО СОПРОТИВЛЕНИЯ БИМЕТАЛЛИЧЕСКИХ МАТЕРИАЛОВ НА ИНТЕНСИВНОСТЬ ТЕПЛООБМЕНА

The influence of the structural material of heat exchange pipes and the contact thermal resistance of the heat transfer surface on the intensity of heat exchange is considered. An approach to the determination of contact thermal resistance is proposed. The necessity of taking into account the contact thermal resistance in the design of heat exchangers is shown