scholarly journals The Process Characteristics of Rapid Freezing: Continuous and Discrete Heat Removal Method

2019 ◽  
Vol 49 (1) ◽  
pp. 104-112
Author(s):  
Евгений Неверов ◽  
Evgeniy Neverov ◽  
Людмила Лифенцева ◽  
Lyudmila Lifenceva ◽  
Андрей Усов ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flux Density ◽  
Heat Sink ◽  
Heat Flux Density ◽  
Meat Products ◽  
Freezing Process ◽  
Rapid Freezing ◽  
Process Characteristics ◽  
Continuous Heat

The research features the rational conditions of the process of rapid freezing for unpackaged small-sized foods by the method of continuous and discrete heat sink. The paper presents a graphical interpretation of the calculations of the average volume temperature for various temperature regimes that are used to freeze semi-finished products. The method makes it possible to determine the temperature at any time. The experiment defined the most rational range of air circulation speeds with a continuous heat sink in the range from 4 m/s to 6 m/s. The article features curves of changes in temperature and heat flux density during the rapid freezing of small-sized semi-finished meat products. They show the nature of the changes in the air coefficient of the meat sample heat transfer curves and the medium velocity of the object air. An increase in the heat flux density and a reduction in the duration of freezing by about 1.4 times occurred when the temperature of the cooling medium decreased from –20°C to – 40°C at an air speed of 6 m/s. The research determined the process characteristics of rapid freezing in continuous mode using a discrete heat sink. The authors describe the comparative characteristics of the change in the duration of the freezing process and the speed of the process with continuous and discrete heat sinks. The study presents the curves of changes in temperature and heat flux density during rapid freezing of small-sized semi-finished meat products, depending on the conditions of heat transfer. When a discrete heat sink was used, the duration of the freezing process was fpund to be 20 min, while with a continuous heat sink it lasted 26 min. The paper also includes a thermogram and the kinetics of heat sink during freezing in discrete conditions, as well as a software program for quick freezing of semi-finished minced meat products. The indicators of the meat quality are considered depending on the conditions of the heat sink, as well as the change in the physicochemical properties of the product after freezing and during storage. Studies of quality indicators of small-sized semi-finished meat products were carried out in the laboratory of the scientific-innovative enterprise “Sibagropererabotka” (Novosibirsk, Russia).

Heat Removal and Thermal Stabilization of High-temperature Surfaces by a Dispersed Coolant Flow

Vestnik MEI ◽  
2021 ◽  
pp. 19-26
Author(s):  
Valentin S. Shteling ◽  
◽  
Vladimir V. Ilyin ◽  
Aleksandr T. Komov ◽  
Petr P. Shcherbakov ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flux Density ◽  
Flow Rate ◽  
Heat Flux Density ◽  
Coolant Flow ◽  
Transfer Coefficients ◽  
Stationary Heat ◽  
Heat Transfer Coefficients ◽  
Stationary Heat Transfer

The effectiveness of stabilizing the surface temperature by a dispersed coolant flow is experimentally studied on a bench simulating energy intensive elements of thermonuclear installations A test section in which the maximum heat flux density can be obtained when being subjected to high-frequency heating was developed, manufactured, and assembled. The test section was heated using a VCh-60AV HF generator with a frequency of not lower than 30 kHz. A hydraulic nozzle with a conical insert was used as the dispersing device. Techniques for carrying out an experiment on studying a stationary heat transfer regime and for calculating thermophysical quantities were developed. The experimental data were obtained in the stationary heat transfer regime with the following range of coolant operating parameters: water pressure equal to 0.38 MPa, water mass flow rate equal to 5.35 ml/s, and induction heating power equal to 6--19 kW. Based on the data obtained, the removed heat flux density and the heat transfer coefficients were calculated for each stationary heat transfer regime. The dependences of the heat transfer coefficient on the removed heat flux density and of the removed heat flux density on the temperature difference have been obtained. High values of heat transfer coefficients and heat flux density at a relatively low coolant flow rate were achieved in the experiments.

scholarly journals ON THE CALCULATION OF CONVECTIVE HEAT TRANSFER UNDER MUTUAL-ACTION OF A JET WITH LIMITING SURFACE

2019 ◽  
Vol 62 (3) ◽  
pp. 208-214
Author(s):  
I. A. Pribytkov ◽  
S. I. Kondrashenko
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convective Heat Transfer ◽  
Flux Density ◽  
Convective Heat ◽  
Heat Flux Density ◽  
Flat Surface ◽  
Dynamic Potential ◽  
Velocity Coefficient ◽  
Limiting Surface

The paper proposes a method for calculating convective heat transfer in the interaction of a single circular jet with a flat surface. The differences of the proposed method from the existing ones are given. The concepts “energodynamic potential of the flow” and “energodynamic power of the flow” are introduced, allowing to determine the intensity of convective heat transfer at “gas-solid” boundary. Differences of the proposed definitions from the existing ones are given: heat flux and heat flux density. The principal difference between the heat flux density q and the energy dynamic potential qэ is as follows: the heat flux density q for convective heat transfer problems means the amount of heat that is transferred from a liquid to a solid surface (or vice versa) per unit of time through a unit of heat exchange surface area. Thus, quantity q characterizes the intensity of convective heat transfer process at the interface. The energy dynamic potential qэ characterizes the flow property as a source or carrier of heat. Value of qэ characterizes the specific energy power of the fluid flow. When calculating the heat transfer, it was proposed to divide the jet when interacting with the flat surface into two parts: before the interaction – the jet part, after – the fan flow. The method for calculating convective heat transfer under jet heating, in which the Reynolds criterion calculated by characteristics of the gas at the nozzle exit is decisive, is not entirely correct. It is proposed to use criteria specific to the fan flow. Characteristic values for the fan flow are its initial average velocity Uвп, distance from the critical point of the jet (point of intersection of vertical axis of the jet with the surface) to the current coordinate of radius downstream. To assess the changes in basic characteristics of a free jet at different distances from the nozzle exit to limiting surface, dependences of the following criteria are presented: jet expansion coefficient; jet injection coefficient; velocity coefficient for any jet section; velocity coefficient for any jet section, except h/d0 = 0; relation of the Reynolds criteria, confirming the need to carry out calculations of heat transfer on the values characteristic separately for the fan flow.

Condensation of Flowing Vapor on a Horizontal Tube—Numerical Analysis as a Conjugate Heat Transfer Problem

1984 ◽  
Vol 106 (4) ◽  
pp. 841-848 ◽  
Author(s):  
H. Honda ◽  
T. Fujii
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Flux Density ◽  
Wall Temperature ◽  
Heat Flux Density ◽  
Tube Wall ◽  
Horizontal Tube ◽  
Uniform Wall

Condensation of flowing vapor on a horizontal tube is numerically analyzed under given conditions of vapor and coolant. Besides the usual boundary layer concept, some approximations are introduced for the determination of shear stress at the vapor-liquid interface. The conjugation of the two-phase boundary layer equations and the heat conduction equation within the tube wall is achieved by using an iterative scheme at the outer surface of the tube wall. The solution thus obtained reveals the effects of vapor velocity, tube material, heat transfer of coolant side, etc., upon circumferential distributions of temperature, heat flux density, and Nusselt number at the outer tube surface. Also the solution compared well with available experimental results for the wall temperature distribution and average Nusselt number. The heat transfer characteristics of steam and refrigerant vapors resemble those of the tubes with uniform wall heat flux density and uniform wall temperature, respectively.

Experimental and Numerical Investigation of a Domestic Refrigerator

2014 ◽  
Author(s):  
Chaolei Zhang ◽  
Yongsheng Lian ◽  
Michael Kempiak ◽  
Erik Hitzelberger ◽  
Scott Crane
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Numerical Investigation ◽  
Flux Density ◽  
Heat Loss ◽  
Heat Flux Density ◽  
Loss Rate ◽  
Domestic Refrigerator ◽  
Heat Loss Rate ◽  
Temperature Controlled

An integrated experimental and numerical investigation was carried out to gain insight into the heat transfer phenomena and flow characteristics inside a domestic refrigerator. A refrigerator model was constructed using insulation foam sheets according to the inner dimensions of a household refrigerator. A reversal heat leak analysis was conducted on the constructed model in a temperature-controlled chamber, where the chamber temperature was lower than the inner temperature of the refrigerator. A temperature-controlled heater was mounted where the evaporator was. The heater was enclosed in a heater box to heat the air and to maintain a high temperature in the refrigerator. A variable speed fan was used to force air circulation. Thermocouples were used to measure the temperature at specified positions and to measure the average temperature difference across the refrigerator side walls. The correlation between the status of the heater and the control temperature variation pattern was analyzed. Heat loss rate was calculated using the data from the thermocouples too. The calculated heat loss rate closely matched the generated heat by the heater and the fan. Moreover, according to the results with different input voltages, the variation trend of the heat flux density was analyzed. A conjugate heat transfer analysis was conducted based on the constructed model using Fluent. The heater was modeled as a heat volume source and the fan was modeled using a pressure jump condition based on the experiment result. Comparisons were made between the experimental and numerical results. The predicted heat loss rate and the heat flux density through the walls matched very well with the experimental results. And the variation trend of the heat flux density with different input voltages also showed the same trend as the experimental result. And the airflow pattern and the temperature distribution were also analyzed in detail.

Surface Heat Transfer Coefficient’s Calculation of W9Mo3Cr4V during Cryogenic Treatment

2010 ◽  
Vol 43 ◽  
pp. 424-429
Author(s):  
Zi Ran Liu ◽  
Cai Xia Ren ◽  
Xian Guo Yan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flux Density ◽  
Heat Flux Density ◽  
Cryogenic Treatment ◽  
Surface Heat ◽  
Surface Heat Transfer ◽  
Surface Heat Transfer Coefficient

In the process of the finite element analogy of the Cryogenic Treatment of the high speed steel cutter with respect to the material of W9Mo3Cr4V, the surface heat transfer coefficient is a crucial parameter. In order to get this parameter, this paper employed the method of inverse heat conduction to process the temperature curve generated through the cryogenic treatment of the tested work piece with the material of W9Mo0Cr4V, thereby obtaining the surface heat transfer coefficient of the tested work piece. This coefficient can be considered the surface heat transfer coefficient of cryogenic treatment of the cutter with the same material. The principle of the inverse heat conduction is as follows: firstly, according to the boundary condition and the initial value in the tri-dimensional space, the equation of the sensitivity coefficient and the temperature field can be deduced. Second, the coupling of two equations is carried out, and the heat flux density is calculated based on above result. The heat flux density will be revise to get the reasonable value . Lastly, the surface heat transfer coefficient can be obtained by the heat flux density. In this paper, all the work is automatically accomplished with the aid of FEPG soft ware and Visual C++ programmable language.

Dependence of unsteady heat transfer on heat flux density

1966 ◽  
Vol 10 (5) ◽  
pp. 335-336 ◽  
Author(s):  
E. V. Kudryavtsev ◽  
I. A. Turchin
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flux Density ◽  
Heat Flux Density ◽  
Unsteady Heat Transfer

Study of Heat Transfer of Gas Flow Heated by Nano-Probe via Direct Stimulation Monte Carlo (DSMC)

2008 ◽  
Author(s):  
X. J. Liu ◽  
J. P. Yang ◽  
Y. W. Yang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Monte Carlo ◽  
Flux Density ◽  
Data Storage ◽  
Spatial Resolution ◽  
Heat Flux Density ◽  
Rational Design ◽  
Gas Flow ◽  
Direct Stimulation

Applications of heated tip/surface configuration for micro-/nano-electromechanical systems (MEMS/NEMS) have been widely explored in these years. Since the small gaps in these MEMS/NEMS are comparable to the mean free path of gaseous molecules, the heat transfer via gaseous molecules from the heated tip to the substrate is fundamentally different from macroscopic conduction or convection heat transfer in gases. In this paper, the heat transfer of the rarefied gases heated by hot nano-tip is investigated by means of the Direct Simulation Monte Carlo (DSMC) method. The results show that both tip geometry and tip-substrate distance affect the heat flux density distribution. With the increase of the crossing-angle θ of the nano-tip, the heat flux tends to decrease, while the spatial resolution tends to improve. Moreover, the heat flux density and spatial resolution tend to decrease with the increase of distance between the nano-tip and the substrate. Simulation results provide valuable information for the rational design and optimization of the heated nano-probe for topography applications such as thermally assisted data storage.

scholarly journals Measurement of heat flux density and heat transfer coefficient

2010 ◽  
Vol 31 (3) ◽  
pp. 3-18 ◽  
Author(s):  
Dawid Taler ◽  
Sławomir Grądziel ◽  
Jan Taler
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flux Density ◽  
Heat Flux Density ◽  
Temperature Dependent ◽  
Practical Applications ◽  
Sensor Material ◽  
The Heat Transfer Coefficient

Measurement of heat flux density and heat transfer coefficientThe paper presents the solution to a problem of determining the heat flux density and the heat transfer coefficient, on the basis of temperature measurement at three locations in the flat sensor, with the assumption that the heat conductivity of the sensor material is temperature dependent. Three different methods for determining the heat flux and heat transfer coefficient, with their practical applications, are presented. The uncertainties in the determined values are also estimated.

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