scholarly journals DETERMINATION OF HEAT TRANSFER EFFICIENCY IN THE CONDITIONS OF FORCED CONVECTION FROM PIPES WITH SPECIAL RIBS

2021 ◽  
Vol 43 (2) ◽  
pp. 21-29
Author(s):  
S.І. Kostyk ◽  
V.Yu. Shybetskyi ◽  
S.V. Plashykhin ◽  
Y.О. Bykoriz
Keyword(s):  
Heat Transfer ◽  
Computer Simulation ◽  
Heat Exchange ◽  
Forced Convection ◽  
Technical Solution ◽  
Transfer Processes ◽  
Heat Transfer Efficiency ◽  
Urgent Task ◽  
Finned Surface ◽  
Almost All

Today, heat transfer processes are present in almost all technological processes of various industries. In heat exchange processes, shell-and-tube heat exchangers are quite effective and easy to manufacture, as the long-term practice of using these devices has shown. Therefore, intensification of heat transfer processes, improvement and development of appropriate equipment is a very urgent task. The object of research is a heat-exchange element with special finning on heat-exchange tubes. The subject of research is the heat transfer processes implemented in a heat exchange element with special finning. The aim of the study is to determine the efficiency of heat transfer of the finned surface of the heat exchange element under conditions of forced convection and to evaluate its efficiency by means of experimental and computer research. This article presents a computer simulation that allows to adequately assess the efficiency of using various designs of finning elements of heat exchange equipment. This is confirmed by the convergence of the experimental data and the results of computer simulation (the discrepancy between the results of the experiment and computer simulation does not exceed 5 %). Experimental and computer studies have shown that the proposed technical solution is more effective than standard ones and can be used in the design of new equipment or improvement of the existing one.

scholarly journals Thermo-Hydraulic Performance of U-Tube Borehole Heat Exchanger with Different Cross-Sections

2021 ◽  
Vol 13 (6) ◽  
pp. 3255
Author(s):  
Aizhao Zhou ◽  
Xianwen Huang ◽  
Wei Wang ◽  
Pengming Jiang ◽  
Xinwei Li
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Resistance ◽  
Cross Sections ◽  
Three Dimensional ◽  
Thermal Response ◽  
Transfer Efficiency ◽  
Cross Sectional ◽  
Heat Transfer Efficiency ◽  
Oval Tube

For reducing the initial GSHP investment, the heat transfer efficiency of the borehole heat exchange (BHE) system can be enhanced to reduce the number or depth of drilling. This paper proposes a novel and simple BHE design by changing the cross-sectional shape of the U-tube to increase the heat transfer efficiency of BHEs. Specifically, in this study, we (1) verified the reliability of the three-dimensional numerical model based on the thermal response test (TRT) and (2) compared the inlet and outlet temperatures of the different U-tubes at 48 h under the premise of constant leg distance and fluid area. Referent to the circular tube, the increases in the heat exchange efficiencies of the curved oval tube, flat oval tube, semicircle tube, and sector tube were 13.0%, 19.1%, 9.4%, and 14.8%, respectively. (3) The heat flux heterogeneity of the tubes on the inlet and outlet sides of the BHE, in decreasing order, is flat oval, semicircle, curved oval, sector, and circle shapes. (4) The temperature heterogeneity of the borehole wall in the BHE in decreasing order is circle, sector, curved oval, flat oval, and semicircle shapes. (5) Under the premise of maximum leg distance, referent to the heat resistance of the tube with a circle shape at 48 h, the heat exchange efficiency of the curved oval, flat oval, semicircle, and sector tubes increased 12.6%, 17.7%, 10.3%, and 7.8%, respectively. (6) We found that the adjustments of the leg distance and the tube shape affect the heat resistance by about 25% and 12%, respectively. (7) The flat-oval-shaped tube at the maximum leg distance was found to be the best tube design for BHEs.

Heat Transfer by Combined Forced Convection and Thermal Radiation in a Heated Tube

1962 ◽  
Vol 84 (4) ◽  
pp. 301-311 ◽  
Author(s):  
M. Perlmutter ◽  
R. Siegel
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchange ◽  
Thermal Radiation ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Tube Wall ◽  
Tube Length ◽  
Tube Surface ◽  
Gas Temperature

An analysis is made to study the heat exchange by combined forced convection and thermal radiation in a tube when there is a specified heat flux imposed at the tube wall. The gas flowing in the tube is assumed transparent to radiation, so that the radiation which is included takes place between the elements of the internal tube surface and between this tube surface and the environment at each end of the tube. The inside surface of the tube is a black emitter and the outside is assumed perfectly insulated. The heat-transfer coefficient for convection alone from the tube wall to the gas is assumed constant. The energy equation governing the heat exchange is solved by two methods which provide results that are in good agreement with each other. Numerical examples of the wall and gas-temperature variations along the tube show the influence of the system parameters such as inlet gas temperature, tube length, and convective heat-transfer coefficient. A simple method is outlined, which can be used under some conditions to obtain an approximate wall-temperature distribution.

COMPUTER SIMULATION OF TRANSFER PROCESSES IN MICROJET BURNER DEVICES WITH SPECIAL COOLING SYSTEMS

2017 ◽  
Author(s):  
Nataliia Fialko ◽  
Viktor Prokopov ◽  
Sergiy Alioshko ◽  
Julii Sherenkovskiy ◽  
Nataliia Meranova ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Computer Simulation ◽  
Cooling System ◽  
Cooling Systems ◽  
Transfer Processes ◽  
Flow And Heat Transfer ◽  
Inner Surface ◽  
Air Blowing

The analysis of efficiency of cooling system of the microjet stabilization burner devices is performed. The features of the flow and heat transfer in cooling systems with air blowing of the inner surface of flame stabilizator and with flat and circular impact jets are studied.

DEVELOPMENT OF A METHOD FOR DETERMINING THE LENGTH TUBE EVAPORATORS AND HEAT PUMP CONDENSERS USING ZEOTROPIC MIXTURES OF WORKING AGENTS

2020 ◽  
pp. 66-77
Author(s):  
А. В. Рулев ◽  
Е. Ю. Усачева
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Heat Pump ◽  
Air Conditioning ◽  
Liquid Mixture ◽  
Transfer Processes ◽  
Temperature Conditions ◽  
Cost Efficient ◽  
Air Conditioning Systems

Постановка задачи. Необходимо разработать методику определения длины трубных испарителей и конденсаторов тепловых насосов, использующих зеотропные смеси рабочих агентов. Результаты. Приводится описание процессов теплообмена в трубных испарителях и конденсаторах тепловых насосов, использующих в качестве рабочих агентов зеотропные смеси предельных углеводородов, таких как пропан и н-бутан. Указанные смеси полностью озоно-экологически безопасны и наиболее экономичны при подогреве приточного воздуха в системах вентиляции и кондиционирования. Выводы. Разработанная методика позволяет учитывать изменение интенсивности теплообмена и температурных условий в зависимости от непрерывно изменяющихся состава и режимов течения парожидкостной смеси, протекающих в следующей последовательности: расслоенно-пробковый, кольце-волновой и дисперсный. Statement of the problem. It is essential to develop a method for determining the length of tube evaporators and heat pump condensers using zeotropic mixtures working agents. Results. The paper describes heat transfer processes in tube evaporators and heat pump condensers that use zeotropic mixtures of limiting hydrocarbons, such as propane and n-butane, as working agents. These mixtures are completely ozone-friendly and most cost-efficient when heating the supply air in ventilation and air conditioning systems. Conclusions. The developed method allows us to account for changes in the intensity of heat exchange and temperature conditions depending on the continuously changing composition and flow modes of the vapor and liquid mixture, which occur in the following sequence: stratified - cork, ring - wave and dispersed.

THERMAL RESISTANCE OF POWER SEMICONDUCTOR MODULES OF SOLDERED CONSTRUCTION

2020 ◽  
Vol 5 ◽  
pp. 122-130
Author(s):  
S.I. MATYUKHIN ◽  
D.O. MALYI ◽  
A.S. VISHNYAKOV ◽  
E.Yu. ORLOV ◽  
V.I. KAZAKOV
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Computer Simulation ◽  
Thermal Resistance ◽  
Comsol Multiphysics ◽  
Power Semiconductor ◽  
Transfer Processes ◽  
Main Effect

The heat transfer processes in power semiconductor modules of soldered construction are studied using the methods of computer simulation in Comsol Multiphysics software. The problem of the thermal resistance of such modules is solved. The factors showing the main effect on the thermal resistance of the modules are studied. A mathematical model allowing engineering calculations of this resistance is developed.

Hydrodynamics and Warmth Trade in Cycles of Cooling of an Attractive Plate in an Attractive Fluid in the Attractive Field

2021 ◽  
Vol 19 (11) ◽  
pp. 32-39
Author(s):  
S.A.A. Alsaati ◽  
Qasim Shakir Kadhim ◽  
Maher Hassan Rashid ◽  
Tuqa Mohammed Jawad Abd UlKadhim
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Exchange ◽  
Cooling Rate ◽  
Steel Plate ◽  
Lower Intensity ◽  
Transfer Processes ◽  
Magnetic Forces ◽  
Air Cavities ◽  
The Magnetic Field

The effect of the magnetic field on heat transfer processes of a magnetized steel plate cooled in a magnetic fluid is experimentally studied. Thermocouples were installed at six points on the surface of the plate along its length. The plots of temperature versus time are obtained in the absence of a magnetic field and in magnetic fields of different intensity. It is found that the intensity of heat exchange depends to a large extent on the magnitude of the magnetic field and on the location of points on the surface of the plate. In a magnetic field, cooling of the central part of the plate occurs with the same intensity as in the absence of a magnetic field and with a lower intensity in comparison with other points on the surface of the plate. Near the plate ends, the cooling rate of the surface is much greater in the magnetic field than in the absence of it. With increasing magnetic field strength, the cooling rate of points in the central part of the plate decreases and is less than in the absence of a magnetic field. The dependence of heat transfer on the magnitude of the magnetic field is explained by the distribution of the magnetic forces acting on the liquid surrounding the plate and the nature of the vapor-air cavities formed near its surface. Experiments on simulation of formation and the shape of vapor-air cavities in a liquid surrounding a magnetizing plate are described.

Research on Trait in Heat Exchange and Flow of Inner Single-Phase Currentin Micro Channel

2012 ◽  
Vol 516-517 ◽  
pp. 408-413 ◽  
Author(s):  
Yue Lian Hu
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Single Phase ◽  
Fluid Dynamic ◽  
High Heat ◽  
Micro Channel ◽  
Heat Transfer Efficiency ◽  
Flow And Heat Transfer ◽  
High Heat Transfer ◽  
Phase Water

During recent years,micro-channel heat transfer technique has been successfully used in many practical situations，and has notable advantages of high heat transfer efficiency and compact configuration.It is an important subject in modern hydrodynamic and heat transfer research field.Computational fluid dynamic program CFX will be used in this article to simulate flow and heat transfer of single-phase water in micro-channel ,flow and temperature felid will be described visually in CFX, and this object is searching a new method to research more flow and heat transfer of single-phase water.

scholarly journals MAINTAINING STABLE NANODISPERSED CERIUM OXIDE FOR HEAT TRANSFER PROCESSES

2020 ◽  
pp. 36-42
Author(s):  
S.Ya. Brychka ◽  
B.I. Bondarenko
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Particle Size ◽  
Heat Exchange ◽  
Cerium Oxide ◽  
Colloidal Particles ◽  
Correlation Spectroscopy ◽  
Oxide Nanoparticles ◽  
Transfer Processes ◽  
Heat Carriers

The introduction of heat carriers progressive types causes the productivity of heat exchange systems to increase. One of the challenges in thermal applied applications is the search for heat carriers that will provide revolutionary indicators of thermal conductivity and stability over time, thereby increasing the order of the heat transfer processes efficiency magnitude. The paper describes the creation of stable colloidal solutions using cerium oxide and organic stabilizers to provide better heat exchange performance compared to true solutions. Cerium oxide colloids were obtained by precipitation of the oxide from an aqueous solution of cerium nitrate with an aqueous ammonia solution in the presence of a polymer under vigorous stirring at room temperature. A number of cerium oxide nanosized dispersions, stabilized with polyvinylpyrrolidone, with a particle size of 1–10 nm were obtained. The content of CeO2 in the obtained dispersions was 1.72.10–3, 5.15.10–3, 8.6.10–3, 1.21.10–2, 1.72.10–2  % at a polymer content of 1.10–3 mol/l, the pH of the dispersions was 8–9. Electron microscopic images of the obtained nanodispersions showed a colloidal particles narrow distribution and cerium oxide nanoparticles in size. Colloidal particles are macromolecular tangles of polyvinylpyrrolidone with oxide nanoparticles strung in them. A volume of 20–50 nm organic matrix contains 10–40 particles of 1–10 nm cerium oxide. The particle size distributions of the dispersions established by the photon-correlation spectroscopy method have two areas of maxima for each sample. The first maximum for the dispersions of all investigated concentrations refers to particles with a diameter of 5–6 nm, which, in our opinion, are particles of cerium oxide, both in polymer beads and probably free from the stabilizer. Another maximum, depending on the sample, is observed at 30–70 nm or 100–300 nm, and relates to colloidal particles of PVP with cerium oxide encapsulated particles. The static stability of the cerium oxide obtained nanodispersions with polyvinylpyrolidone for two years under standard conditions is comparable to the true polymer solution. It is proposed by the method of UV spectroscopy to control the reproducibility of the obtaining materials technology. Tests of the thermal conductivity of the obtained 1.72.10–3 % stable cerium oxide nanodispersion were performed at 50 °C relative to distilled water with a thermal conductivity coefficient of 0.65 W/(m·deg). We found an increase in the coefficient for nanodispersions by 4–6 %, which is a significant value for dilute solutions. Ref. 15, Fig. 4 .

scholarly journals THERMOFILLER EFFECT ON HEAT-STRESSED MULTILAYERED ENCLOSING STRUCTURES

2018 ◽  
pp. 155-169
Author(s):  
A. N. Kozlobrodov ◽  
E. A. Ivanova ◽  
A. V. Golovko
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Thermal Properties ◽  
Heat Exchange ◽  
Quantitative Assessment ◽  
Thermal Conditions ◽  
Finite Element Program ◽  
Transfer Processes ◽  
Negative Effect ◽  
Element Program

The article deals with spatial heat-stressed elements that influence the thermal properties of multilayered enclosing structures. Using the ANSYS finite element program, the effect of thermofiller location on heat transfer processes is studied nearby the heat-stressed elements. A quantitative assessment is given to thermal conditions of heat-stressed elements of enclosing structure under extreme heat exchange conditions. Specific conditions are created to raise the temperature nearby the heat-stressed elements and reduce their negative effect.  

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