scholarly journals Determination of heat transfer coefficient in advanced rotary film evaporator

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.

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

2019 ◽  
Vol 9 ◽  
pp. 184798041987646 ◽  
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%.

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

2019 ◽  
Vol 64 (1) ◽  
pp. 87-97
Author(s):  
E. A. Pitsuha ◽  
E. K. Buchilko ◽  
Yu. S. Teplitskii ◽  
D. S. Slizhuk
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Fluidized Bed ◽  
Flow Rate ◽  
Radial Direction ◽  
Air Flow ◽  
Air Flow Rate ◽  
Outlet Hole ◽  
The Heat Transfer Coefficient

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.

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

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%.

The Simulation of Boiling Heat Transfer in Metal Foam Tube

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.

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

1980 ◽  
Vol 102 (2) ◽  
pp. 342-346 ◽  
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.

scholarly journals C INVESTIGATION OF HEAT TRANSFER COEFFICIENT AUGMENTATION IN DIVERGENT RECTANGULAR DUCT FOR TWO PHASES FLOW (AIR-WATER)

2020 ◽  
Vol 20 (2) ◽  
pp. 111-121
Author(s):  
Hadi O . Basher ◽  
Riyadh S Al-Turaihi ◽  
Ahmed A. Shubba
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Water Volume ◽  
Maximum Heat ◽  
Air Volume ◽  
The Heat Transfer Coefficient

In this project, the flow distribution for air and water, and the enhancement of the heattransfer coefficient are experimentally studied. Experimental studies have been performed totest the influence of discharge, pitch, the height of ribs at a constant heat flux on thetemperature and pressure distributions. Along the channel of the test and the heat transfercoefficient, the water volume flow rate was about (5-12 L/min), the air volume flow rate wasabout (5.83-16.66 L/min), and heat were (80, 100,120, watt). An experimental rig wasconstructed within the test whole system. On the other hands, the channel has a divergentsection with an angle =15o with vertical axis. The study included changing in the ribs heightby using three values (12, 15, 18 mm) and changing the ribs pitch into three values (5, 8, 10mm).The results indicated an increasing in the local heat transfer coefficient as a result ofincreasing the discharge. While there was an inverse influence for the temperature distributionalong the test channel which drops when the discharge rise. The results also confirm that theincreasing in the pitch distance leads to reduce the heat transfer coefficient. Increasing theribs height increases the coefficient of heat transfer. However, the experiment heat transfercoefficient improves about (15.6 %) when the water volume flow rate increased from (5 to 12L/min), and about (18.7%) when the air volume flow rate increased from (5.83 to 16.66L/min). The best heat transfer coefficient was about (35.6 %) which can be achieved whenthe pitch decreased from (10 to 5mm). The increasing of the height from (12 to 18) mmimproves the heat transfer coefficient about (11.2 %). The best rib dimension was 18 mmheight, and 5 mm pitch, which give a maximum heat transfer coefficient (1212.02 W/m2. oC).

scholarly journals Convective Bubbly Flow of Water in an Annular Pipe: Role of Total Dissolved Solids on Heat Transfer Characteristics and Bubble Formation

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1566 ◽  
Author(s):  
M. M. Sarafraz ◽  
M. S. Shadloo ◽  
Zhe Tian ◽  
Iskander Tlili ◽  
Tawfeeq Abdullah Alkanhal ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Contact Angle ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Rate ◽  
Bubble Diameter ◽  
Nucleate Boiling ◽  
Heat Transfer Characteristics ◽  
The Heat Transfer Coefficient

Formation of bubbles in water inside an annulus pipe in a flow boiling regime was experimentally investigated. The effect of various variables, such as total dissolved solid materials (TDS) in terms of mass fraction, flow rate of water, and applied heat flux (HF) on the heat transfer coefficient (HTC) and bubble behavior of water, was experimentally investigated. A regression formula was fitted to estimate the average bubble diameter at various TDS values, with accuracy of <4.1% up to heat flux of 90 kW/m2. Results show that the presence of TDS materials can increase the contact angle of bubble and bubble diameter, and also promotes the HTC value of the system. However, flow rate of water suppressed bubble generation, and increased the heat transfer coefficient due to the renewal of the thermal boundary layer around the boiling surface. Likewise, it was identified that forced convective and nucleate boiling heat transfer mechanisms contribute to the flow of boiling water, and heat flux is a key parameter in determining the mechanism of heat transfer. In the present study, heat flux of 15 kW/m2 at 50 °C was the heat flux in which onset of nucleate boiling was identified inside the annulus pipe. The contact angle of water at TDS values of 300 mg/L and 1200 mg/L was 74° and 124°, respectively, showing the improvement in heat transfer characteristics of water due to the presence of TDS materials.

Study on the Influence Factors of Heat Transfer Coefficient of Supercritical Water Under Different Circulation Modes

2020 ◽  
Author(s):  
Peng Xu ◽  
Tao Zhou ◽  
Jialei Zhang ◽  
Juan Chen ◽  
Zhongguan Fu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Flow Rate ◽  
Supercritical Water ◽  
Natural Circulation ◽  
Inlet Temperature ◽  
The Heat Transfer Coefficient

Abstract There are many factors that can affect the heat transfer coefficient (HTC) of supercritical water in forced and natural circulation. The correlation between the factors with the HTC under different circulation modes has an important influence on the reactor core design. By extracting the experimental data of supercritical water in forced circulation and natural circulation, the grey correlation model was used to analyze the relational degree between these factors with HTC. The results show that: Under the condition of forced circulation, there is a positive correlation between the inlet temperature, mass flow velocity, the thickness of the grid body with the HTC of supercritical water, and the order is: mass flow velocity &gt; inlet temperature &gt; the thickness of the grid body; there is a negative correlation between the pressure, heat flux with the heat transfer coefficient of supercritical water, and the order is: pressure &gt; heat flux. Under the condition of natural circulation, there is a positively correlation between heating power, inlet temperature and circulation flow rate with HTC, and the order of magnitude is: circulation flow rate &gt; heating power &gt; inlet temperature; diameter and pressure are negatively correlated with heat transfer coefficient, and the order of magnitude is: pressure &gt; diameter. In the two circulation modes, mass flow rate is an important factor affecting the heat transfer capacity of supercritical water, while the effect of heat flux on the heat transfer coefficient is contrary.

Thermal Analysis of Plate Condensers in Presence of Flow Maldistribution Using Refrigerant R134a

2006 ◽  
Author(s):  
P. R. Bobbili ◽  
B. Sunden ◽  
S. K. Das
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Rate ◽  
Thermal Performance ◽  
Flow Rate Ratio ◽  
Two Phase ◽  
Wide Range ◽  
Flow Maldistribution ◽  
The Heat Transfer Coefficient

Flow maldistribution in plate heat exchangers causes deterioration of both thermal and hydraulic performance. The situation becomes more complicated for two phase flows during condensation where uneven distribution of the liquid to the channels reduces heat transfer due to high liquid flooding. The present study evaluates the thermal performance of falling film plate condensers with flow maldistribution from port to channel considering the heat transfer coefficient inside the channels as a function of channel flow rate. A generalized mathematical model has been developed to investigate the effect of maldistribution on the thermal performance as well as the exit vapor quality of a refrigerant, namely R-134a. A wide range of parameters are studied and these show the effects of the mass flow rate ratio of cold fluid (water) and two-phase refrigerant fluid, flow configuration, number of channels and correlation for the heat transfer coefficient. The analysis presented here also suggests an improved method for heat transfer data analysis for plate condensers.

scholarly journals Characteristics of a micro-fin evaporator: Theoretical analysis and experimental verification

2013 ◽  
Vol 17 (5) ◽  
pp. 1443-1447
Author(s):  
Hui-Fan Zheng ◽  
Xiao-Wei Fan ◽  
Fang Wang ◽  
Yao-Hua Liang
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Water Mass ◽  
Water Mass Flow Rate ◽  
The Heat Transfer Coefficient

A theoretical analysis and experimental verification on the characteristics of a micro-fin evaporator using R290 and R717 as refrigerants were carried out. The heat capacity and heat transfer coefficient of the micro-fin evaporator were investigated under different water mass flow rate, different refrigerant mass flow rate, and different inner tube diameter of micro-fin evaporator. The simulation results of the heat transfer coefficient are fairly in good agreement with the experimental data. The results show that heat capacity and the heat transfer coefficient of the micro-fin evaporator increase with increasing logarithmic mean temperature difference, the water mass flow rate and the refrigerant mass flow rate. Heat capacity of the micro-fin evaporator for diameter 9.52 mm is higher than that of diameter 7.00 mm with using R290 as refrigerant. Heat capacity of the micro-fin evaporator with using R717 as refrigerant is higher than that of R290 as refrigerant. The results of this study can provide useful guidelines for optimal design and operation of micro-fin evaporator in its present or future applications.

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