scholarly journals ASPECTS OF COMPLEXITY OF METAL-FIBROUS MICROSTRUCTURE FOR THE CONSTRUCTION OF HIGH-PERFORMANCE HEAT EXCHANGERS: THERMAL PROPERTIES

Aviation ◽  
2020 ◽  
Vol 24 (3) ◽  
pp. 99-104 ◽  
Author(s):  
Łukasz J. Orman
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Boiling Heat Transfer ◽  
Air Conditioning ◽  
High Performance ◽  
Smooth Surface ◽  
Heat Pipes ◽  
Sintering Process ◽  
Enhancement Of Heat Transfer ◽  
Air Conditioning Systems

The paper considers the application of metal – fibrous microstructures in the development of highly efficient heat exchangers. Such structures can be successfully used in air conditioning systems of modern planes or in heat pipes located in planes and spacecraft. Copper fibers of 50 mm diameter have been used to produce coatings of different volumetric porosity. The sintering process was used to produce the samples. Pool boiling heat transfer tests have been performed on the non – isothermal surfaces of the fin with distilled water and ethyl alcohol (99.8% purity) as boiling agents. A significant enhancement of heat transfer has been recorded with the use of the metal – fibrous microstructures in comparison to the smooth surface without any coating. The enhancement proved to vary considerably depending on the superheat value.

scholarly journals COMPUTER PROGRAM FOR CALCULATION MICROCHANNEL HEAT EXCHANGERS FOR AIR CONDITIONING SYSTEMS

2016 ◽  
Vol 52 (3) ◽  
Author(s):  
Olga V. Olshevska
Keyword(s):  
Heat Transfer ◽  
Computer Program ◽  
Heat Exchangers ◽  
Software Package ◽  
Air Conditioning ◽  
Correlation Equation ◽  
Design Time ◽  
Software Packages ◽  
Air Conditioning Systems ◽  
Thermodynamic Equations

Creating a computer program to calculate microchannel air condensers to reduce design time and carrying out variant calculations. Software packages for thermophysical properties of the working substance and the coolant, the correlation equation for calculating heat transfer, aerodynamics and hydrodynamics, the thermodynamic equations for the irreversible losses and their minimization in the heat exchanger were used in the process of creating. Borland Delphi 7 is used for creating software package.

HEAT TRANSFER ENHANCEMENT IN PHASE-CHANGE HEAT EXCHANGERS

Aviation ◽  
2014 ◽  
Vol 18 (1) ◽  
pp. 40-43 ◽  
Author(s):  
Rafał Chatys ◽  
Milan Malcho ◽  
Łukasz J. Orman
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Atmospheric Pressure ◽  
Heat Exchangers ◽  
Boiling Heat Transfer ◽  
Smooth Surface ◽  
Transfer Enhancement ◽  
Mesh Structure ◽  
Heat Exchanger Surface ◽  
Copper Mesh

The paper presents the results of boiling heat transfer enhancement due to the application of additional mesh on the heat exchanger surface. The copper mesh of porosity of 75% was sintered to the copper heater producing strong bonds between the elements. The results indicate a possibility of significant improvement of heat transfer conditions in comparison to the smooth surface. The heat flux was found to be almost six times higher for the same superheat if the mesh structure was applied. Distilled water and ethanol were the working fluids. The investigations were performed under atmospheric pressure.

Visualization of Boiling Heat Transfer on Micro Porous Coated Surface in Confined Space

2013 ◽  
Author(s):  
Chien-Yuh Yang ◽  
Chien-Fu Liu
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Boiling Heat Transfer ◽  
Heat Transfer Performance ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Confined Space ◽  
Two Phase ◽  
Nucleate Boiling Heat Transfer ◽  
Coated Surface

Numerous researches have been developed for pool boiling on microporous coated surface in the past decade. The nucleate boiling heat transfer was found to be increased by up to 4.5 times than that on uncoated surface. Recently, the two-phase micro heat exchangers have been considered for high flux electronic devices cooling. The enhancement techniques for improving the nucleate boiling heat transfer performance in the micro heat exchangers have gotten more importance. Previous studies of microporous coatings, however, have been restricted to boiling in unconfined space. No studies have been made on the feasibility of using microporous coatings for enhancing boiling in confined spaces. This study provides an experimental observation of the vapor generation and leaving processes on microporous coatings surface in a 1-mm confined space. It would be helpful for understanding the mechanism of boiling heat transfer and improving the design of two-phase micro heat exchangers. Aluminum particles of average diameter 20 μm were mixed with a binder and a carrier to develop a 150 μm thickness boiling enhancement paint on a 3.0 cm by 3.0 cm copper heating surface. The heating surface was covered by a thin glass plate with a 1 mm spacer to form a 1 mm vertical narrow space for the test section. The boiling phenomenon was recorded by a high speed camera. In addition to the three boiling regimes observed by Bonjour and Lallemand [1], i.e., isolated deformed bubbles, coalesced bubbles and partial dryout at low, moderate and high heat fluxes respectively in unconfined space, a suction and blowing process was observed at the highest heat flux condition. Owing to the space confinement, liquid was sucked and vapor was expelled periodically during the bubble generation process. This mechanism significantly enhanced the boiling heat transfer performance in confined space.

scholarly journals Effect of the size of graded baffles on the performance of channel heat exchangers

2020 ◽  
Vol 24 (2 Part A) ◽  
pp. 767-775 ◽  
Author(s):  
Djamel Sahel ◽  
Houari Ameur ◽  
Touhami Baki
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchangers ◽  
Computer Code ◽  
Channel Length ◽  
Heat Transfer Characteristics ◽  
Enhancement Of Heat Transfer ◽  
Transfer Rates ◽  
Flow And Heat Transfer ◽  
Friction Factors

The baffling technique is well-known for its efficiency in terms of enhancement of heat transfer rates throught channels. However, the baffles insert is accompanied by an increase in the friction factor. This issue remains a great challenge for the designers of heat exchangers. To overcome this issue, we suggest in the present paper a new design of baffles which is here called graded baffle-design. The baffles have an up- or down-graded height along the channel length. This geometry is characterized by two ratios: up-graded baffle ratio and down-graded baffle ratio which are varied from 0-0.08. For a range of Reynolds number varying from 104 to 2 ? 104, the turbulent flow and heat transfer characteristics of a heat exchanger channel are numerically studied by the computer code FLUENT. The obtained results revealed an enhancement in the thermohydraulic performance offered by the new suggested design. For the channel with a down-graded baffle ratio equal to 0.08, the friction factors decreased by 4-8%

Enhancement of Heat Transfer in Heat Pipes Using TiO2/Benzene Based Nano-coolants

2016 ◽  
Author(s):  
Abhijit Dayal Raj ◽  
Anakh Pal Anakhi ◽  
Deepak Kumar Yadav ◽  
Balakrishnan Pandian ◽  
Harsumeet Singh ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Pipes ◽  
Enhancement Of Heat Transfer
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