Abstract
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.
Highlights
Phase – change heat exchangers are widely used in many areas of engineering e.g. in refrigeration and air conditioning systems or cooling of electronic devices
The present paper discusses the use of metal – fibrous microstructures and the enhancement of boiling heat transfer, which is offered as a result of their application
The heat transfer coefficient for water boiling on a sample of 85% porosity at the pressure of 0.1 MPa was highest for the 0.8 mm structure height and was 5.5 times higher than for the smooth surface at the same heat flux
Summary
Phase – change heat exchangers are widely used in many areas of engineering e.g. in refrigeration and air conditioning systems or cooling of electronic devices. The heat transfer coefficient for water boiling on a sample of 85% porosity at the pressure of 0.1 MPa was highest for the 0.8 mm structure height and was 5.5 times higher than for the smooth surface at the same heat flux. Wójcik (2005) investigated water boiling heat transfer on a horizontal isothermal tube of the diameter of 19 mm covered with a copper – fibrous microstructure of 40% porosity and height 0.5–2.0 mm. The coating was produced with fibers of 50 mm diameter and 3 mm long To his earlier work (Wójcik, 2004) a significant enhancement was recorded for the porous structures – the highest for the layer height of 2 mm. Kalawa et al (2017) tested pool boiling of distilled water heat transfer on horizontal isothermal surfaces covered with coatings made of stainless steel fibers. There is a need to expend the experimental database regarding the analysis of porous metal – fibrous coatings, especially due to the fact that heat exchangers found in engineering applications are usually non-isothermal
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