Condensation heat transfer and pressure drop characteristics of R-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting

Wang, Xuwen; Ho, Jin Yao; Leong, K.C.; Wong, Teck Neng

doi:10.1016/j.ijheatmasstransfer.2018.04.163

Cited by 26 publications

(8 citation statements)

References 40 publications

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“…However, the problem of its efficiency remains unsolved [14][15][16][17][18][19], and the application of the method in each case requires significant energy and finances, which hampers the development of this production technique and its applications. Today, common conventional selective laser melting (SLM) or selective laser sintering (SLS) machines allow for producing parts with a maximum laser power of about 400 W [20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Power Density Distribution for Laser Additive Manufacturing (SLM): Potential, Fundamentals and Advanced Applications

et al. 2018

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Problems with the laser additive manufacturing of metal parts related to its low efficiency are known to hamper its development and application. The method of selective laser melting of metallic powders can be improved by the installation of an additional laser beam modulator. This allows one to control the power density distribution optically in the laser beam, which can influence the character of heat and mass transfer in a molten pool during processing. The modulator contributes alternative modes of laser beam: Gaussian, flat top (top hat), and donut (bagel). The study of its influence includes a mathematical description and theoretical characterization of the modes, high-speed video monitoring and optical diagnostics, characterization of processing and the physical phenomena of selective laser melting, geometric characterization of single tracks, optical microscopy, and a discussion of the obtained dependences of the main selective laser melting (SLM) parameters and the field of its optimization. The single tracks were produced using the advanced technique of porosity lowering. The parameters of the obtained samples are presented in the form of 3D graphs. The further outlook and advanced applications are discussed.

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Section: Introductionmentioning

confidence: 99%

Power Density Distribution for Laser Additive Manufacturing (SLM): Potential, Fundamentals and Advanced Applications

et al. 2018

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“…Despite being a powder bed fusion technology, our work along with others [ 28,33 ] have shown that AM parts produced by SLM are robust and can operate in high pressure environments. These characteristics along with our developed nanostructuring technique provide opportunities for a wider range of dropwise condensation applications of AM surfaces involving low‐surface‐tension fluids commonly found in chemical plants, [ 68 ] biomass production [ 69 ] and refrigeration systems.…”

Section: Discussionmentioning

confidence: 93%

“…Here, we use AlSi10Mg as a rational material selection because of three reasons: 1) micro and nanostructuring of the Al phase can be easily achieved using conventional methods due to the high chemical reactivity of pure Al when compared to other widely used metals, 2) the presence of Si as an alloying element represents a less reactive secondary phase, resulting in the potential to fabricate cellular-like nanostructures, and 3) the ubiquitous use of Al-alloys in many industrial applications due to the their excellent thermophysical properties and relatively low density. Here, we use the SLM280HL AM facility to fabricate samples with a laser power of 200 W, scanning speed of 1.3 m s −1 and a hatch spacing of 80 μm, selected based on previous fabrication of bulk components with good structural integrity [27,28,[31][32][33] (see Section S2 of the Supporting Information for the detailed AM fabrication process). Flat AM samples having 1 in.…”

Section: Resultsmentioning

confidence: 99%

Ultrascalable Surface Structuring Strategy of Metal Additively Manufactured Materials for Enhanced Condensation

Rabbi

Khodakarami

et al. 2022

Advanced Science

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Metal additive manufacturing (AM) enables unparalleled design freedom for the development of optimized devices in a plethora of applications. The requirement for the use of nonconventional aluminum alloys such as AlSi10Mg has made the rational micro/nanostructuring of metal AM challenging. Here, the techniques are developed and the fundamental mechanisms governing the micro/nanostructuring of AlSi10Mg, the most common metal AM material, are investigated. A surface structuring technique is rationally devised to form previously unexplored two-tier nanoscale architectures that enable remarkably low adhesion, excellent resilience to condensation flooding, and enhanced liquid-vapor phase transition. Using condensation as a demonstration framework, it is shown that the two-tier nanostructures achieve 6× higher heat transfer coefficient when compared to the best filmwise condensation. The study demonstrates that AM-enabled nanostructuring is optimal for confining droplets while reducing adhesion to facilitate droplet detachment. Extensive benchmarking with past reported data shows that the demonstrated heat transfer enhancement has not been achieved previously under high supersaturation conditions using conventional aluminum, further motivating the need for AM nanostructures. Finally, it has been demonstrated that the synergistic combination of wide AM design freedom and optimal AM nanostructuring method can provide an ultracompact condenser having excellent thermal performance and power density.

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“…Using R134a in 8.7-mm channels, (Ho et al, 2019) determined that helically arranged conical fins could enhance the heat transfer coefficient by up to 2.44 times more than pressure drop was increased (Ho et al, 2019). This increase in heat transfer coefficient enhancement relative to increased pressure was not found to be true of the dome fins used by Wang et al (2018) also using R134a in 8.7-mm channels (Wang et al, 2018;Ho et al, 2019). Aroonrat and Wongwises (2019) used a 8.1-mm circular channel with R134a where dimples on the exterior of the tube were used to create hollow pin fins with depths of 0.5, 0.75, and 1 mm with diameters of 1, 1.5, and 2 mm, respectively, in the channel.…”

Section: Introductionmentioning

confidence: 99%

“…Other approaches to enhancing filmwise condensation include physically modifying the condensing surface with structures designed to increase condensing surface area, penetrate the film, or disrupt the film by the addition of fins, twisted tape, or corrugation inside of the condensing channel (Cavallini et al, 2003;Dalkilic and Wongwises, 2009;El Kadi et al, 2021). Ho et al (2019) used conical pin fins in a circular tube and compared them to dome shaped fins evaluated by Wang et al (2018). Using R134a in 8.7-mm channels, (Ho et al, 2019) determined that helically arranged conical fins could enhance the heat transfer coefficient by up to 2.44 times more than pressure drop was increased (Ho et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Visualizing and disrupting liquid films for filmwise flow condensation in horizontal minichannels

et al. 2022

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This paper investigates the effects of hemispherical mounds on filmwise condensation heat transfer in micro-channels. Also investigated were the impacts that spatial orientation of the three-sided condensation surface (i.e., gravitational effects) on steam condensation, where the cooled surfaces were either the lower surface (i.e., gravity pulls liquid towards the condensing surfaces) or upper surface (i.e., gravity pulls liquid away from the condensing surfaces). Two test coupons were used with 1.9-mm hydraulic diameters and either a plain copper surface or a copper surface modified with 2-mm diameter hemispherical mounds. Heat transfer coefficients, film visualization, and pressure drop measurements were recorded for both coupons in both orientations at mass fluxes of 50 kg/m2s and 125 kg/m2s. For all test conditions, the mounds were found to increase condensation heat transfer coefficients by at minimum 13% and at maximum 79%. When the test section was inverted (i.e., condensing surface on the top of flowing steam), minimal differences were found in mound performance, while the plain coupon reduces heat transfer coefficients by as much as 14%. Flow visualization suggests that the mounds enhanced heat transfer due to the disruption of the film as well as by reducing the thermal resistance of the film. Pressure drops followed parabolic behavior with quality, being higher in the mound coupon than the plain coupon. No significant pressure drop differences in the inverted orientation were observed.

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Condensation heat transfer and pressure drop characteristics of R-134a in horizontal smooth tubes and enhanced tubes fabricated by selective laser melting

Cited by 26 publications

References 40 publications

Power Density Distribution for Laser Additive Manufacturing (SLM): Potential, Fundamentals and Advanced Applications

Power Density Distribution for Laser Additive Manufacturing (SLM): Potential, Fundamentals and Advanced Applications

Ultrascalable Surface Structuring Strategy of Metal Additively Manufactured Materials for Enhanced Condensation

Visualizing and disrupting liquid films for filmwise flow condensation in horizontal minichannels

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