Development of technological line for obtaining flax trust

One of the most effective ways to intensify heat transfer when blowing surfaces with air is jet blowing. High intensity of transfer processes during jetting, relatively low energy costs for its implementation, simplicity and flexibility of control of this process have led to its widespread use in various fields. Mathematical modeling of heat transfer regularities in systems of impact jets is significantly complicated due to the three-dimensional nature of the flue-channel flow near the surfaces of complex shape. Therefore, it is advisable to use experimental research methods. The purpose of this study is to justify the use of the method of regular thermal regime to determine the average heat transfer coefficient during jet cooling of the surface. Regular mode of cooling (heating) of bodies is characterized by the fact that the relative rate of change of excess temperature for all points of the body remains constant. Since the thermal model was made of a highly thermally conductive duralumin alloy, the condition Bi <0.1 was met, when the average temperatures on the surface and volume will be the same. Therefore, the experiments recorded the readings of only one thermocouple. To compare the results of this experimental study with the results of other authors, cases of blowing a smooth concave surface with single - and three - row jet systems were chosen. The first case was studied in [3,4], the second - in [5]. The results of the performed test experiments agree satisfactorily with the data of these works, which were obtained both by the method of regular mode [5] and other methods of recording heat fluxes ([3] - passive heat flux sensor; [4] - electrocalorimetry). The difference between the average heat transfer coefficients and the known literature data does not exceed ±7..12%, which indicates a sufficient probability of the results obtained in this work, and the possibility of using the method of regular thermal regime in the study of jet cooling of complex bodies. Key words: heat exchange, jet system, cooling, concave surface

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Convective heat transfer measured directly with a heat flux sensor

Journal of Applied Physiology ◽

10.1152/jappl.1990.68.3.1275 ◽

1990 ◽

Vol 68 (3) ◽

pp. 1275-1281 ◽

Cited By ~ 12

Author(s):

U. Danielsson

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Convective Heat Transfer ◽

Convective Heat ◽

Convective Heat Transfer Coefficient ◽

The Body ◽

Heat Flux Sensor ◽

Calibration Constant

A heat flux disk has been developed that directly measures the convective heat transfer in W/m2. When the sensor is calibrated on an aluminum cylinder, the calibration constant obtained is greatest in still air. As air movement increases, the calibration constant is reduced with increasing convective heat transfer coefficient, 0.5%.W-1.m2.K. The influence of wind on the calibration value is greatly reduced when the sensor is attached to a surface with lower thermal conductivity. The local convective heat transfer coefficient (hc) of the human body was measured. The leg acts in a manner similar to that of a cylinder, with the highest hc value at the front facing the wind and the lowest approximately 90 degrees from the wind, and in the wake a value is obtained that is close to the average hc value of the leg. When hc is measured at several angles and positions all over the body, the results indicate that the body acts approximately as a cylinder with a hc value related to the wind speed as hc = 8.6.v0.6 W.m-2.K-1, where v is velocity.

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HEAT TRANSFER ANALYSIS OF AN IMPINGING SLOT JET ON A CONCAVE SURFACE

10.1615/tfec2019.cmd.027616 ◽

2019 ◽

Author(s):

Gérard J. Poitras ◽

A. Babineau ◽

Gilles C. Roy ◽

L.-E. Brizzi

Keyword(s):

Heat Transfer ◽

Heat Transfer Analysis ◽

Concave Surface

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Local Heat Transfer Distribution from a Row of Impinging Jets to a Cylindrical Concave Surface

6th International Energy Conversion Engineering Conference (IECEC) ◽

10.2514/6.2008-5725 ◽

2008 ◽

Author(s):

Vadiraj Katti ◽

S. V. Prabhu

Keyword(s):

Heat Transfer ◽

Local Heat Transfer ◽

Local Heat ◽

Impinging Jets ◽

Concave Surface

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A Computational Study on the Role of Parameters for Identification of Thyroid Nodules by Infrared Images (and Comparison with Real Data)

Sensors ◽

10.3390/s21134459 ◽

2021 ◽

Vol 21 (13) ◽

pp. 4459

Author(s):

José R. González ◽

Charbel Damião ◽

Maira Moran ◽

Cristina A. Pantaleão ◽

Rubens A. Cruz ◽

...

Keyword(s):

Heat Transfer ◽

Thyroid Nodules ◽

Numerical Study ◽

Computational Study ◽

Internal Heat ◽

Heat Transfer Process ◽

The Body ◽

Physical Parameters ◽

Infrared Sensors ◽

Wide Range

According to experts and medical literature, healthy thyroids and thyroids containing benign nodules tend to be less inflamed and less active than those with malignant nodules. It seems to be a consensus that malignant nodules have more blood veins and more blood circulation. This may be related to the maintenance of the nodule’s heat at a higher level compared with neighboring tissues. If the internal heat modifies the skin radiation, then it could be detected by infrared sensors. The goal of this work is the investigation of the factors that allow this detection, and the possible relation with any pattern referent to nodule malignancy. We aim to consider a wide range of factors, so a great number of numerical simulations of the heat transfer in the region under analysis, based on the Finite Element method, are performed to study the influence of each nodule and patient characteristics on the infrared sensor acquisition. To do so, the protocol for infrared thyroid examination used in our university’s hospital is simulated in the numerical study. This protocol presents two phases. In the first one, the body under observation is in steady state. In the second one, it is submitted to thermal stress (transient state). Both are simulated in order to verify if it is possible (by infrared sensors) to identify different behavior referent to malignant nodules. Moreover, when the simulation indicates possible important aspects, patients with and without similar characteristics are examined to confirm such influences. The results show that the tissues between skin and thyroid, as well as the nodule size, have an influence on superficial temperatures. Other thermal parameters of thyroid nodules show little influence on surface infrared emissions, for instance, those related to the vascularization of the nodule. All details of the physical parameters used in the simulations, characteristics of the real nodules and thermal examinations are publicly available, allowing these simulations to be compared with other types of heat transfer solutions and infrared examination protocols. Among the main contributions of this work, we highlight the simulation of the possible range of parameters, and definition of the simulation approach for mapping the used infrared protocol, promoting the investigation of a possible relation between the heat transfer process and the data obtained by infrared acquisitions.

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Heat Transfer in Highly Turbulent Separated Flows: A Review

Energies ◽

10.3390/en14041005 ◽

2021 ◽

Vol 14 (4) ◽

pp. 1005

Author(s):

Viktor I. Terekhov

Keyword(s):

Heat Transfer ◽

Turbulent Flow ◽

Separated Flow ◽

Separated Flows ◽

Turbulence Characteristic ◽

Wall Jets ◽

Average Heat ◽

Free Stream Turbulence ◽

External Turbulence ◽

Near Wall

The study of flows with a high degree of turbulence in boundary layers, near-wall jets, gas curtains, separated flows behind various obstacles, as well as during combustion is of great importance for increasing energy efficiency of the flow around various elements in the ducts of gas-dynamic installations. This paper gives some general characteristics of experimental work on the study of friction and heat transfer on a smooth surface, in near-wall jets, and gas curtains under conditions of increased free-stream turbulence. Taking into account the significant effect of high external turbulence on dynamics and heat transfer of separated flows, a similar effect on the flow behind various obstacles is analyzed. First of all, the classical cases of flow separation behind a single backward-facing step and a rib are considered. Then, more complex cases of the flow around a rib oriented at different angles to the flow are analyzed, as well as a system of ribs and a transverse trench with straight and inclined walls in a turbulent flow around them. The features of separated flow in a turbulized stream around a cylinder, leading to an increase in the width of the vortex wake, frequency of vortex separation, and increase in the average heat transfer coefficient are analyzed. The experimental results of the author are compared with data of other researchers. The structure of separated flow at high turbulence—characteristic dimensions of the separation region, parameters of the mixing layer, and pressure distribution—are compared with the conditions of low-turbulent flow. Much attention is paid to thermal characteristics: temperature profiles across the shear layer, temperature distributions over the surface, and local and average heat transfer coefficients. It is shown that external turbulence has a much stronger effect on the separated flow than on the boundary layer on a flat surface. For separated flows, its intensifying effect on heat transfer is more pronounced behind a rib than behind a step. The factor of heat transfer intensification by external turbulence is most pronounced in the transverse cavity and in the system of ribs.

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Investigations of Flow and Heat Transfer Characteristics in a Channel Impingement Cooling Configuration with a Single Row of Water Jets

Energies ◽

10.3390/en14144327 ◽

2021 ◽

Vol 14 (14) ◽

pp. 4327

Author(s):

Min-Seob Shin ◽

Santhosh Senguttuvan ◽

Sung-Min Kim

Keyword(s):

Heat Transfer ◽

Local Heat Transfer ◽

Target Surface ◽

Channel Height ◽

Heat Transfer Characteristics ◽

Transfer Coefficients ◽

Impingement Cooling ◽

Average Heat ◽

Transfer Characteristics ◽

Flow And Heat Transfer

The present study experimentally and numerically investigates the effect of channel height on the flow and heat transfer characteristics of a channel impingement cooling configuration for various jet Reynolds numbers in the range of 2000–8600. A single array consisting of eleven jets with 0.8 mm diameter injects water into the channel with 2 mm width at four different channel heights (3, 4, 5, and 6 mm). The average heat transfer coefficients at the target surface are measured by maintaining a temperature difference between the jet exit and the target surface in the range of 15–17 °C for each channel height. The experimental results show the average heat transfer coefficient at the target surface increases with the jet Reynolds number and decreases with the channel height. An average Nusselt number correlation is developed based on 85 experimentally measured data points with a mean absolute error of less than 4.31%. The numerical simulation accurately predicts the overall heat transfer rate within 10% error. The numerical results are analyzed to investigate the flow structure and its effect on the local heat transfer characteristics. The present study advances the primary understanding of the flow and heat transfer characteristics of the channel impingement cooling configuration with liquid jets.

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