Heat transfer in the vortex zone of a cyclone-bed chamber of furnace unit with fluidized bed

An experimental investigation of the heat-transfer coefficient to a spherical probe in a cyclone-bed chamber with fluidized bed in the “cold” and “hot” regimes has been carried out. The heat-transfer coefficient was determined by the regular thermal regime. The dependences of the heat-transfer coefficient in the vortex-bed furnace on the various parameters: the diameter of the outlet hole, the air flow rate, the share of the bottom blast and the location of the probe were determined. It is revealed that in the “cold” regime the heat-transfer coefficient has practically constant value in the radial direction, it almost does not depend on the diameter of the outlet hole and the share of the bottom blast and depends significantly on the position of the probe along the height of the furnace and the air flow rate. The effect of flow swirling on the heat-transfer coefficient in a cyclone-bed chamber with fluidized bed is determined. When the fuel burns (“hot” regime), the heat-transfer coefficient is not constant in the radial direction and accept the maximum values in the central area of the chamber. At the same time, the part of conductive-convective component in the total heat-transfer coefficient to the spherical probe, depending on its radial position, is estimated at 40–70 %. The results can be used in the design and creation of modern high-efficiency furnaces for burning local solid biofuels.

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Comparison of heat transfer performance of ZnO-PG, α-Al2O3-PG, and γ-Al2O3-PG nanofluids in car radiator

Nanomaterials and Nanotechnology ◽

10.1177/1847980419876465 ◽

2019 ◽

Vol 9 ◽

pp. 184798041987646 ◽

Cited By ~ 3

Author(s):

XiaoRong Zhou ◽

Yi Wang ◽

Kai Zheng ◽

Haozhong Huang

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Propylene Glycol ◽

Flow Rate ◽

Volume Concentration ◽

Maximum Heat ◽

Cooling Performance ◽

Maximum Heat Transfer ◽

The Heat Transfer Coefficient

In this study, the cooling performance of nanofluids in car radiators was investigated. A car radiator, temperature measuring instrument, and other components were used to set up the experimental device, and the temperature of nanofluids passing through the radiator was measured by this device. Three kinds of nanoparticles, γ-Al2O3, α-Al2O3, and ZnO, were added to propylene glycol to prepared nanofluids, and the effects of nanoparticle size and type, volume concentration, initial temperature, and flow rate were tested. The results indicated that the heat transfer coefficients of all nanofluids first increased and then decreased with an increase in volume concentration. The ZnO-propylene glycol nanofluid reached a maximum heat transfer coefficient at 0.3 vol%, and the coefficient decreased by 25.6% with an increase in volume concentration from 0.3 vol% to 0.5 vol%. Smaller particles provided a better cooling performance, and the 0.1 vol% γ-Al2O3-propylene glycol nanofluid had a 19.9% increase in heat transfer coefficient compared with that of α-Al2O3-propylene glycol. An increase in flow rate resulted in a 10.5% increase in the heat transfer coefficient of the 0.5 vol% α-Al2O3-propylene glycol nanofluid. In addition, the experimental temperature range of 40–60°C improved the heat transfer coefficient of the 0.2 vol% ZnO-propylene glycol nanofluid by 46.4%.

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3D Numerical Simulation of Laminar Flow and Conjugate Heat Transfer through Fabric

Autex Research Journal ◽

10.1515/aut-2015-0052 ◽

2017 ◽

Vol 17 (1) ◽

pp. 53-60 ◽

Cited By ~ 2

Author(s):

Guocheng Zhu ◽

Dana Kremenakova ◽

Yan Wang ◽

Jiri Militky ◽

Rajesh Mishra ◽

...

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Laminar Flow ◽

Transfer Coefficient ◽

Heat Loss ◽

Human Skin ◽

Human Body ◽

Conjugate Heat Transfer ◽

Air Flow ◽

The Heat Transfer Coefficient

AbstractThe air flow and conjugate heat transfer through the fabric was investigated numerically. The objective of this paper is to study the thermal insulation of fabrics under heat convection or the heat loss of human body under different conditions (fabric structure and contact conditions between the human skin and the fabric). The numerical simulations were performed in laminar flow regime at constant skin temperature (310 K) and constant air flow temperature (273 K) at a speed of 5 m/s. Some important parameters such as heat flux through the fabrics, heat transfer coefficient, and Nusselt number were evaluated. The results showed that the heat loss from human body (the heat transfer coefficient) was smallest or the thermal insulation of fabric was highest when the fabric had no pores and no contact with the human skin, the heat loss from human body (the heat transfer coefficient) was highest when the fabric had pores and the air flow penetrated through the fabric.

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Determination of heat transfer coefficient in advanced rotary film evaporator

Technology audit and production reserves ◽

10.15587/2706-5448.2021.237979 ◽

2021 ◽

Vol 4 (3(60)) ◽

pp. 42-45

Author(s):

Aleksey Zagorulko ◽

Andrii Zahorulko ◽

Maksym Serik ◽

Vyacheslav Оnishchenko ◽

Alexander Postadzhiev

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Flow Rate ◽

Fruit And Vegetable ◽

Important Indicator ◽

Periodic Action ◽

Film Evaporator ◽

Rotary Film ◽

The Heat Transfer Coefficient

The object of research is the process of concentrating fruit and vegetable purees in an improved rotary film evaporator. The existing hardware design of traditional processes for processing fruits and vegetables, as a rule, is not unified enough, inconvenient in operation and is designed for high productivity. Concentration of fruit and vegetable purees occurs mainly in vacuum evaporators of periodic and continuous operation at a temperature of 60–80 °C under vacuum, which allows them to significantly preserve their nutritional value. But the duration of the process remains very significant (in devices of periodic action up to 75–90 minutes). One of the most problematic areas in the concentration of fruit and vegetable raw materials is significant losses of biologically active substances. At the same time, an important indicator of the quality of the process of concentrating pasty fruit and vegetable pastes is the value of the heat transfer coefficient, which characterizes the efficiency of the heat transfer method and the design features of the mixing device, taking into account the thermophysical characteristics of the product. To create conditions for conducting research to determine the heat transfer coefficient, it is necessary to use instrumentation with precise regulation of the necessary technological parameters. To study the heat transfer coefficient when concentrating fruit and vegetable purees, an automatic installation of an improved rotary evaporator was designed. The improvement of the rotary film evaporator (RFE) is carried out due to the lower location of the separating space by installing a screw discharge of the paste and preheating the output puree with secondary steam. The experimental dependences of the heat transfer coefficient on the product flow rate make it possible to determine the rational values of the flow rate of the RFE feedstock at various values of the rotor shaft speed. It is found that the heat transfer coefficient is influenced to a large extent by the product consumption, and the rotor speed acts to a lesser extent, only the relative speed of fluid passage around the developed hinged blade changes. It is found that when the frequency changes from 0.3 to 1.7 s–1, an increase in the heat transfer coefficient by 1.45 times is observed, which is explained by a more intensive degree of mixing of the product by the blades.

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Study on Heat Transfer Coefficient of Supercritical Water Based on Factorial Analysis

10.1115/icone28-63216 ◽

2021 ◽

Author(s):

Peng Xu ◽

Tao Zhou ◽

Ning Chen ◽

Juan Chen ◽

Zhongguan Fu

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Mass Flow Rate ◽

Flow Rate ◽

Supercritical Water ◽

Prediction Error ◽

Inlet Temperature ◽

Percentage Contribution ◽

The Heat Transfer Coefficient

Abstract Heat transfer coefficient has an important influence on the flow and heat transfer of supercritical water in the core channels. The effects of different factors and their interactions on the heat transfer coefficient of the supercritical water were studied by full factorial experimental design method, such as pressure, mass flow rate, heat flux, and inlet temperature. The results show that: Within the range of the tested working conditions, effect D (inlet temperature), effect B (mass flow rate) and effect A (pressure) had a significant impact on the heat transfer coefficient, where the percentage contribution of effect D was 48.21%; effect B was 21.58%; effect A was 15.1%. The percentage contribution of other factors and their interactions on the heat transfer coefficient of the supercritical water can be ignored. At the same time, a prediction formula of heat transfer coefficient on supercritical water was fitted, and it was found that the prediction error of this formula conformed to the assumption of normality, and the prediction error was 10.5%.

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Heat Transfer Performance in a Superheater of an Industrial CFBC Using Fuzzy Logic-Based Methods

Entropy ◽

10.3390/e21100919 ◽

2019 ◽

Vol 21 (10) ◽

pp. 919 ◽

Cited By ~ 6

Author(s):

Krzywanski

Keyword(s):

Heat Transfer ◽

Fuzzy Logic ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Fluidized Bed ◽

Circulating Fluidized Bed ◽

Practical Significance ◽

Overall Heat Transfer Coefficient ◽

Bed Temperature ◽

The Heat Transfer Coefficient

The heat transfer coefficient in the combustion chamber of industrial circulating flidized bed (CFB) boilers depends on many parameters as it is a result of multifactorial mechanisms proceeding in the furnace. Therefore, the development of an effective modeling tool, which allows for predicting the heat transfer coefficient is interesting as well as a timely subject, of high practical significance. The present paper deals with an innovative application of fuzzy logic-based (FL) method for the prediction of a heat transfer coefficient for superheaters of fluidized-bed boilers, especially circulating fluidized-bed combustors (CFBC). The approach deals with the modeling of heat transfer for the Omega Superheater, incorporated into the reaction chamber of an industrial 670 t/h CFBC. The height above the grid, bed temperature and voidage and temperature, gas velocity, and the boiler’s load constitute inputs. The developed Fuzzy Logic Heat (FLHeat) model predicts the local overall heat transfer coefficient of the Omega Superheater. The model is in good agreement with the measured data. The highest overall heat transfer coefficient is equal 220 W/(m2K) and can be achieved by the SH I superheater for the following inputs l = 20 m, tb = 900 °C, v = 0.95, u = 7 m/s, M-C-R = 100%. The proposed technique is an effective strategy and an option for other procedures of heat transfer coefficient evaluation.

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The Simulation of Boiling Heat Transfer in Metal Foam Tube

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.448-453.3312 ◽

2013 ◽

Vol 448-453 ◽

pp. 3312-3315

Author(s):

Bin Sun ◽

Bin Bin Cui ◽

Chao Liang

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Boiling Heat Transfer ◽

Metal Foam ◽

Vapor Quality ◽

The Heat Transfer Coefficient

A three-dimensional physical mode of metal foam tube was built by CFD software. The Brinkman-Forchheimer extended Darcy equation and user-defined function (UFD) of the mass transfer and energy transfer between vapor phase and liquid phase compiled by C language were used in the simulation of boiling heat transfer in metal foam tube. The results show that, at a given mass flow rate, the pressure drop nonlinearly increases as the vapor quality rises; At the low mass flow rate, with the increasing of vapor quality, the flow pattern is transferred to wavy flow from stratified flow and then transfer to stratified wavy flow, while the heat transfer coefficient decreases with the increasing of vapor quality. At the high mass flow rate, with the increasing of vapor quality, the flow pattern is transferred to annular flow from slug flow, while the heat transfer coefficient increases with the increasing of vapor quality. The simulation results agree well with the experimental data.

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An Experimental Study of Falling Liquid Film Breakdown on a Horizontal Cylinder During Heat Transfer

Journal of Heat Transfer ◽

10.1115/1.3244285 ◽

1980 ◽

Vol 102 (2) ◽

pp. 342-346 ◽

Cited By ~ 50

Author(s):

E. N. Ganic ◽

M. N. Roppo

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Heat Transfer Coefficient ◽

Liquid Film ◽

Transfer Coefficient ◽

Flow Rate ◽

Film Flow ◽

Horizontal Cylinder ◽

Dry Patch ◽

The Heat Transfer Coefficient

In this study, an experimental investigation was conducted with subcooled water film flowing over an electrically heated horizontal cylinder. The combinations of film flow rate and heat flux at which film breakdown occurs (i.e., dry patches appear on the surface) were determined. At the conditions prior to dry patch formation, the heat transfer coefficient was determined as well. The results showed that the heat flux needed to cause a dry patch increases with film flow rate. Also, prior to dry patch formation, the heat transfer coefficient increases with film flow rate. The effects of the tube spacing and the liquid film inlet temperature on the breakdown heat flux and heat transfer coefficient were also studied.

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