scholarly journals The flow boiling heat transfer coefficient determination in a minichannel used the FEM combined with Trefftz functions

2018 ◽  
Vol 240 ◽  
pp. 01033
Author(s):  
Magdalena Piasecka ◽  
Kinga Strąk ◽  
Beata Maciejewska
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Conduction Problem ◽  
Flow Boiling ◽  
Inverse Heat Conduction Problem ◽  
Basis Functions ◽  
Heated Wall ◽  
Heated Plate ◽  
Plate Temperature

The method of solving the inverse heat conduction problem, by means of the FEM with Trefftz-type basis functions, during flow boiling in a minichannel was shown. This basis functions were constructed with using the Hermite interpolation and Trefftz functions. The aim of the numerical calculations was to determine the local heat transfer coefficient on the basis of experimental data in a horizontally oriented minichannel. The refrigerant flowing along the minichannel (HFE-649 or HFE-7100) was heated by a thin enhanced plate by vibration-assisted laser texturing. The temperature on an outer smooth side of the plate was detected by means of infrared thermography. On the heated wall–fluid contact surface in the minichannel the heat transfer coefficient was obtained from the Robin boundary condition. It was assumed that the temperature distribution in the heated plate was described by the Poisson equation. The unknown values of temperature and temperature derivatives at nodes were computed by minimizing the functional which describes the mean square error of the approximate solution on the boundary and along common edges of neighbouring elements. The results were presented as the heated plate temperature and heat transfer coefficient versus the minichannel length.

scholarly journals The heat transfer coefficient determination with the use of the Beck-Trefftz method in flow boiling in a minichannel

2018 ◽  
Vol 180 ◽  
pp. 02099 ◽  
Author(s):  
Kinga Strąk ◽  
Beata Maciejewska ◽  
Magdalena Piasecka
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Transfer Problem ◽  
Heat Conduction Problem ◽  
Flow Boiling ◽  
Inverse Heat Conduction Problem ◽  
Heated Wall ◽  
Trefftz Method

In this paper, the solution of the two-dimensional inverse heat transfer problem with the use of the Beck method coupled with the Trefftz method is proposed. This method was applied for solving an inverse heat conduction problem. The aim of the calculation was to determine the boiling heat transfer coefficient on the basis of temperature measurements taken by infrared thermography. The experimental data of flow boiling heat transfer in a single vertical minichannel of 1.7 mm depth, heated asymmetrically, were used in calculations. The heating element for two refrigerants (FC-72 and HFE-7100, 3M) flowing in the minichannel was the plate enhanced on the side contacting with the fluid. The analysis of the results was performed on the basis of experimental series obtained for the same heat flux and two different mass flow velocities. The results were presented as infrared thermographs, heated wall temperature and heat transfer coefficient as a function of the distance from the minichannel inlet. The results was discussed for the subcooled and saturated boiling regions separately.

Time-dependent study of boiling heat transfer coefficient in a vertical minichannel

2019 ◽  
Vol 30 (6) ◽  
pp. 2953-2969 ◽  
Author(s):  
Beata Maciejewska ◽  
Magdalena Piasecka
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Flow Boiling ◽  
Basis Functions ◽  
Time Dependent ◽  
Heated Wall ◽  
Content Type ◽  
Saturated Boiling

Purpose The purpose of this paper is to determine the time-dependent heat transfer coefficient during FC-72 flow boiling in a 1.7-mm-deep vertical and asymmetrically heated minichannel. Design/methodology/approach The temperature of the minichannel heated wall was recorded continuously with the use of thermocouples. The heat transfer coefficients for the subcooled and saturated boiling regions at the heated wall–fluid contact surface were calculated from the Robin boundary condition. Both the wall and fluid temperatures were obtained from the solution of the inverse nonstationary problems in two adjacent domains: the heated wall and flowing fluid. The FEM with Trefftz-type basis functions was applied to solve the inverse problem. Findings The obtained time-dependent heat transfer coefficient in subcooled boiling achieved rather low values, whereas in saturated boiling, the coefficient was the highest at the channel inlet. The boiling curves were plotted to illustrate the results. Practical implications The results of experiments are the best source of information for the design of minichannel cooling systems used for thermoregulation of components and heat exchangers. High-tech minichannel heat exchangers are applied in various industrial applications as microelectronics devices, gas turbines, internal combustion engines, nuclear reactors, X-ray sources and organic rankine cycle (ORC) modules. Originality/value In the study, the Trefftz functions for the nonstationary Fourier–Kirchhoff equation with the factor describing void fraction were determined and then used to construct the time-dependent basis functions in FEM.

scholarly journals Vibration-Assisted Laser Surface Texturing and Electromachining for the Intensification of Boiling Heat Transfer in a Minichannel

2017 ◽  
Vol 62 (4) ◽  
pp. 1983-1990 ◽  
Author(s):  
M. Piasecka ◽  
K. Strąk ◽  
B. Grabas
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Metal Surfaces ◽  
Surface Texturing ◽  
Laser Surface ◽  
Laser Surface Texturing ◽  
Heated Plate ◽  
Plate Temperature ◽  
Saturated Boiling

AbstractThe paper describes applications of the vibration-assisted laser surface texturing and spark erosion process as methods of modifying properties and structures of metal surfaces. Practical aspects of the use of produced surfaces in the heat exchanger with a minichannel have been described. Compared with smooth surfaces, developed metal surfaces obtained by vibration-assisted laser surface texturing and electromachining show more effective heat transfer. The local heat transfer coefficient for the saturated boiling region obtained for developed surfaces had the values significantly higher than those obtained for the smooth plate at the same heat flux. The experimental results are presented as the heated plate temperature (obtained from infrared thermography) and relationships between the heat transfer coefficient and the distance along the length of the minichannel for the saturated boiling region.

Optically Based Rapid Heat Transfer Measurements in Complex Internal Flows

2007 ◽  
Vol 129 (12) ◽  
pp. 1655-1665 ◽  
Author(s):  
Charles W. Booten ◽  
John K. Eaton
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Boundary Conditions ◽  
Transfer Coefficient ◽  
Laser Heating ◽  
Heat Conduction Problem ◽  
Reynolds Numbers ◽  
Inverse Heat Conduction Problem ◽  
Inverse Heat Conduction ◽  
Thermal Boundary Conditions

Abstract An optically based technique was developed that involves fabrication of a thin-walled plastic model with laser heating applied to a small section of the outer surface. The heat flux distribution applied to the model by the laser was measured first using a short-duration, transient experiment. The external temperature distribution was then recorded using infrared thermography with steady laser heating. The measured heat flux and temperature distributions were used as thermal boundary conditions in a finite-element code to solve an inverse heat conduction problem for the heat transfer coefficient on the internal passage wall. Hydrodynamically fully developed turbulent flow in a round tube was used as a test case for the development of the new optical method. The Reynolds numbers used were 30,000 and 60,000. This flow was chosen because accurate computational tools were available to calculate the internal heat transfer coefficient for a variety of thermal boundary conditions. In addition, this geometry simplified both the model fabrication and the implementation of a finite-element model for the inverse heat conduction problem. Heat transfer coefficient measurements agreed with numerical simulations and semi-analytical solutions within 1.5% and 8.5% for the low and high Reynolds numbers, respectively. Additional simulations suggest that the method can be accurate with thermal boundary conditions more complex than in these experiments.

scholarly journals Experimental analysis of the evaporation of a thin liquid film deposited on a capillary heated tube: estimation of the local heat transfer coefficient

2021 ◽  
Vol 2116 (1) ◽  
pp. 012110
Author(s):  
L Cattani ◽  
F Bozzoli ◽  
V Ayel ◽  
C Romestant ◽  
Y Bertin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Film ◽  
Transfer Coefficient ◽  
Heat Conduction Problem ◽  
Thin Liquid Film ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Inverse Heat Conduction Problem ◽  
Two Phase

Abstract The aim of this work is to estimate the local heat flux and heat transfer coefficient for the case of evaporation of thin liquid film deposited on capillary heated channel: it plays a fundamental role in the two-phase heat transfer processes inside mini-channels. In the present analysis it is investigated a semi-infinite slug flow (one liquid slug followed by one single vapour bubble) in a heated capillary copper tube. The estimation procedure here adopted is based on the solution of the inverse heat conduction problem within the wall domain adopting, as input data, the temperature field on the external tube wall acquired by means of infrared thermography.

Infrared image filtering applied to the restoration of the convective heat transfer coefficient distribution in coiled tubes

2015 ◽  
Vol 23 (1) ◽  
Author(s):  
F. Bozzoli ◽  
L. Cattani ◽  
G. Pagliarini ◽  
S. Rainieri
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Conduction ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Conduction Problem ◽  
Convective Heat Transfer Coefficient ◽  
Inverse Heat Conduction Problem ◽  
Inverse Heat Conduction

AbstractThis paper presents and assesses an inverse heat conduction problem (IHCP) solution procedure which was developed to determine the local convective heat transfer coefficient along the circumferential coordinate at the inner wall of a coiled pipe by applying the filtering technique approach to infrared temperature maps acquired on the outer tube’s wall. The data−processing procedure filters out the unwanted noise from the raw temperature data to enable the direct calculation of its Laplacian which is embedded in the formulation of the inverse heat conduction problem. The presented technique is experimentally verified using data that were acquired in the laminar flow regime that is frequently found in coiled−tube heat−exchanger applications. The estimated convective heat transfer coefficient distributions are substantially consistent with the available numerical results in the scientific literature.

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