Applied Sciences

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24 pages, 9141 KiB

Open AccessArticle

Saturated Boiling Enhancement of Novec-7100 on Microgrooved Surfaces with Groove-Induced Anisotropic Properties

by Ho-Ching Lin, Cheng-Hsin Kang, Hui-Chung Cheng, Tien-Li Chang and Ping-Hei Chen

Appl. Sci. 2024, 14(2), 495; https://doi.org/10.3390/app14020495 - 05 Jan 2024

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The effects of the anisotropic properties (wettability and roughness) of microgrooved surfaces on heat transfer were experimentally investigated during pool boiling using Novec-7100 as a working fluid. The idea for introducing the concept of anisotropic wettability in boiling experiments draws inspiration from biphilic [...] Read more.

The effects of the anisotropic properties (wettability and roughness) of microgrooved surfaces on heat transfer were experimentally investigated during pool boiling using Novec-7100 as a working fluid. The idea for introducing the concept of anisotropic wettability in boiling experiments draws inspiration from biphilic surfaces. The investigation is also motivated by two-phase immersion cooling, which involves phase-change heat transfer, using a dielectric liquid as a working fluid. Very few studies have focused on the effects of surfaces with anisotropic properties on boiling performance. Thus, this study aims to examine the pool-boiling heat transfer performance on surfaces with microgroove-induced anisotropic properties under the saturation condition. A femtosecond-laser texturing method was employed to create microgrooved surfaces with different groove spacings. The results indicated that anisotropic properties affected the heat transfer coefficient and critical heat flux. Relative to the plain surface, microgrooved surfaces enhanced the heat transfer performance due to the increased number of bubble nucleation sites and higher bubble detachment frequency. An analysis of bubble dynamics under different surface conditions was conducted with the assistance of high-speed images. The microgrooved surface with a groove spacing of 100 μm maximally increased the BHTC by 37% compared with that of the plain surface. Finally, the CHF results derived from experiments were compared with related empirical correlations. Good agreement was achieved between the results and the prediction correlation. Full article

(This article belongs to the Special Issue Fluid Flow and Heat Transfer: Latest Advances and Prospects)

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13 pages, 4748 KiB

Open AccessArticle

Flow Condensation of Low-GWP Zeotropic Mixtures Inside 5 mm OD Micro-Finned Tube

by Nima Irannezhad, Luisa Rossetto and Andrea Diani

Appl. Sci. 2024, 14(1), 373; https://doi.org/10.3390/app14010373 - 31 Dec 2023

Viewed by 779

Abstract

In response to stringent rules inhibiting the implementation of refrigerants with high global warming impact, alternative candidates should undergo assessments to prove their viability. The mixtures R450A and R454B, being the center of the current focus, underwent experimentation for flow condensation inside a [...] Read more.

In response to stringent rules inhibiting the implementation of refrigerants with high global warming impact, alternative candidates should undergo assessments to prove their viability. The mixtures R450A and R454B, being the center of the current focus, underwent experimentation for flow condensation inside a mini-scale micro-finned tube of 5 mm outer diameter. The operating conditions were set to be in the range of 0.1 to 0.95 for vapor quality, 75 to 400 kg m⁻² s⁻¹ for mass flux, and recorded at saturation temperatures of 30 and 40 °C. Having concluded the evaluations of thermal and hydraulic properties of heat transfer coefficient (HTC) and frictional pressure drop (FPD), a comparison was drawn between the two candidates, where R450A possessed superior HTC and higher FPD per unit length at higher vapor qualities due to lower vapor density. Ultimately, empirical models pertinent to flow condensation were compared with the acquired experimental results. Full article

(This article belongs to the Special Issue Fluid Flow and Heat Transfer: Latest Advances and Prospects)

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20 pages, 4567 KiB

Open AccessArticle

Boundary Treatment with Additive Boundary Particles for Incompressible Smoothed Particle Hydrodynamics Method

by Fanfan Sun, Bingyue Song and Mingyi Tan

Appl. Sci. 2023, 13(20), 11448; https://doi.org/10.3390/app132011448 - 18 Oct 2023

Viewed by 585

Abstract

A new boundary treatment considering uniform particle distribution using additive boundary particles for the incompressible smoothed particle hydrodynamics (ISPH) method is proposed. With this new boundary treatment, the solid boundary can be easily modeled just following the geometry configuration and consequently the simulations [...] Read more.

A new boundary treatment considering uniform particle distribution using additive boundary particles for the incompressible smoothed particle hydrodynamics (ISPH) method is proposed. With this new boundary treatment, the solid boundary can be easily modeled just following the geometry configuration and consequently the simulations of fluid–structure interaction problems can be simplified. The efficiency of this new boundary treatment is analyzed, and the implementations are compared with other exiting boundary treatments such as repulsive force and ghost particles. Simulations of the 2D dam-breaking case, static tank, and 2D u-tube test are carried out as examples to demonstrate the performance of this new boundary treatment. It is shown that better predictions can be gained with the new boundary treatment for the pressure distribution in these cases than those obtained from other boundary treatments. Full article

(This article belongs to the Special Issue Fluid Flow and Heat Transfer: Latest Advances and Prospects)

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26 pages, 16047 KiB

Open AccessArticle

Numerical Study on Cooling Performance of a Steam-Cooled Blade Based on Response Surface Method

by Zhen Zhao, Lei Xi, Jianmin Gao, Liang Xu and Yunlong Li

Appl. Sci. 2023, 13(11), 6625; https://doi.org/10.3390/app13116625 - 30 May 2023

Cited by 1 | Viewed by 717

Abstract

In order to investigate the cooling mechanism of the turbine blade and to enrich and supplement the experimental study of the blade, a numerical study of a steam-cooled blade with five cooling channels was carried out based on the response surface model. The [...] Read more.

In order to investigate the cooling mechanism of the turbine blade and to enrich and supplement the experimental study of the blade, a numerical study of a steam-cooled blade with five cooling channels was carried out based on the response surface model. The surface cooling efficiency and dimensionless temperature distribution of the steam-cooled blade were obtained with different mainstream inlet temperature, outlet pressure, pressure ratio of inlet to outlet, temperature ratio and flow ratio of steam to mainstream by using the flow-solid coupling numerical method. The influence of the working parameters on the cooling performance of air-cooled blade and steam-cooled blade, including the average cooling efficiency, temperature non-uniformity, and average dimensionless temperature, was comparatively investigated; the correlation equation of the working parameters on the cooling performance of the steam-cooled blade was obtained. The results show that the influence of mainstream inlet temperature and outlet pressure on the cooling performance of the steam-cooled blade is not significant; the cooling efficiency of the steam-cooled blade increases by 5.92%, 7.35% and 26.51% respectively as the mainstream inlet to outlet pressure ratio, the temperature ratio and the flow ratio of steam to mainstream increase; the dimensionless temperature increases by 3.74% as the temperature ratio increases and decreases by 0.93% and 4.09% as mainstream inlet to outlet pressure ratio and flow ratio increase; the temperature non-uniformity decreases by 4.09% and 30.08% respectively, as the mainstream inlet to outlet pressure ratio and temperature ratio increase and increases by 37.99% as the flow ratio increases; the effect of working parameters on air-cooled blade and steam-cooled blade is the same, but the steam-cooled blade has 14.06–17.81% higher cooling efficiency, 18.47–29.01% higher temperature non-uniformity and 1.86–2.58% lower dimensionless temperature compared to the air-cooled blade under the same working parameters; the correlation equation obtained by fitting the response surface model has higher accuracy. Full article

(This article belongs to the Special Issue Fluid Flow and Heat Transfer: Latest Advances and Prospects)

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22 pages, 9833 KiB

Open AccessArticle

Water Heating and Circulating Heating System with Energy-Saving Optimization Control

by Feng-Chieh Lin, Chin-Sheng Chen and Chia-Jen Lin

Appl. Sci. 2023, 13(9), 5542; https://doi.org/10.3390/app13095542 - 29 Apr 2023

Cited by 1 | Viewed by 1234

Abstract

Over the past few years, due to an aging population and a longer life expectancy, traditional high-oil, high-calorie, and high-temperature culinary concepts have been widely replaced by healthier, low-temperature heating methods. However, while the key device of the Sous-Vide heating system ordinarily operates [...] Read more.

Over the past few years, due to an aging population and a longer life expectancy, traditional high-oil, high-calorie, and high-temperature culinary concepts have been widely replaced by healthier, low-temperature heating methods. However, while the key device of the Sous-Vide heating system ordinarily operates at full power to achieve the target temperature, pump speed control is not currently considered within the water heating and circulating system framework. This study develops a model for a water heating and circulating system and examines the characteristics of the lowest power point and pump speed. Building upon these results, we present the LPPT control method as a means of optimizing input power for heating. The effectiveness of this method is supported by simulations and experiments, which demonstrate a significant reduction in energy consumption. The control concept calculates the real-time input power based on the input voltage and current, and it can achieve the most efficient input power by perturbing the pump speed. It is demonstrated that applying LPPT to daily pot capacity reduces the Sous-Vide Cooker’s input power by up to 17% and achieves efficiency optimization control by removing the need to calculate the foods and other parameters of the water heating and circulating system environment. Full article

(This article belongs to the Special Issue Fluid Flow and Heat Transfer: Latest Advances and Prospects)

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18 pages, 24320 KiB

Open AccessArticle

Studies on Influence of Chromium Layer on Inner Surface of Steel Tube on Heat Transfer

by Mateusz Zieliński, Piotr Koniorczyk and Zbigniew Surma

Appl. Sci. 2023, 13(9), 5523; https://doi.org/10.3390/app13095523 - 28 Apr 2023

Cited by 3 | Viewed by 1050

Abstract

This paper presents the results of numerical calculations of heat transfer in the steel wall of a tube with different chromium layer thicknesses on the inner surface for a single and a sequence of heat impulses. In modeling the thermal phenomenon, the tube [...] Read more.

This paper presents the results of numerical calculations of heat transfer in the steel wall of a tube with different chromium layer thicknesses on the inner surface for a single and a sequence of heat impulses. In modeling the thermal phenomenon, the tube material was assumed to be homogeneous, and the inner surface of the tube had a protective chromium layer. The calculations were performed for temperature-dependent parameters of the 30HN2MFA steel and chromium. The tube was divided into 30 zones. The time varying the heat transfer coefficient and the heat flux density on the inner surface of the tube in each zone were calculated. The numerical simulations of heat transfer in the tube wall were performed using the FEM implemented in COMSOL Multiphysics software. On account of the high thermal conductivity of chromium, after the first and subsequent heat impulses, as the thickness of the chrome layer increases, the highest peak temperature drops, while the temperature inside the steel wall of the tube increases. After the first heat impulse, the temperature of the wall at a depth 0.5 mm below the inner surface is twice as high for a tube with a 200 µm thick chrome coating compared to a tube without this coating. This paper showed that, after seven heat impulses, the temperature of the steel tube substrate does not exceed 750 °C, at which the shrinkage of the material occurs, causing cracks in the chrome coating. Full article

(This article belongs to the Special Issue Fluid Flow and Heat Transfer: Latest Advances and Prospects)

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14 pages, 2833 KiB

Open AccessArticle

Heat Transfer Optimization of an Electronic Control Unit Immersed in Forced Liquid Coolant

by Cristina Georgiana Lates, Catalin Gabriel Dumitras, Petrica Vizureanu and Andrei Victor Sandu

Appl. Sci. 2023, 13(9), 5310; https://doi.org/10.3390/app13095310 - 24 Apr 2023

Viewed by 1936

Abstract

The current paper aims to present a cooling concept for future centralized platforms of ECUs (Electronic Control Units) from the automotive industry that involves grouping multiple electronic devices into a single system and cooling them with forced convection dielectric coolant. The enhancement consists [...] Read more.

The current paper aims to present a cooling concept for future centralized platforms of ECUs (Electronic Control Units) from the automotive industry that involves grouping multiple electronic devices into a single system and cooling them with forced convection dielectric coolant. The enhancement consists of replacing the inside air of the module with a dielectric coolant that has a higher thermal conductivity than air and employing an additional prototype system that aids in forced liquid cooling. To meet automotive requirements, the experiments were exposed to an ambient temperature of 85 °C. Temperature measurements on these solutions’ hot spots were compared to those on a thermal paste-only reference electronic module. This study used DFSS (Design for Six Sigma) techniques to determine the ideal pump flow rate, fan air flow rate, and liquid volume in the housing, leading to an optimization in heat dissipation. Finding a trustworthy transfer function that could forecast the impact of the crucial design parameters that had been found was the main goal. The electronics cooled by forced convection coolant improved heat dissipation by up to 60% when compared to the reference module. This demonstrates that the DoE (Design of Experiments) method, which is based on a limited number of measurements, can estimate the behavior of the ECU without the need for a more involved theoretical framework. Full article

(This article belongs to the Special Issue Fluid Flow and Heat Transfer: Latest Advances and Prospects)

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19 pages, 5926 KiB

Open AccessArticle

Development of FEM Calculation Methods to Analyse Subcooled Boiling Heat Transfer in Minichannels Based on Experimental Results

by Magdalena Piasecka, Beata Maciejewska and Paweł Łabędzki

Appl. Sci. 2022, 12(24), 12982; https://doi.org/10.3390/app122412982 - 17 Dec 2022

Cited by 1 | Viewed by 1176

Abstract

Even though two-phase heat transfer of refrigerants in minichannel heat sinks has been studied extensively, there is still a demand for improvements in overall thermal performance of miniature heat transfer exchangers. Experimental investigation and sophisticated heat transfer calculations with respect to heat transfer [...] Read more.

Even though two-phase heat transfer of refrigerants in minichannel heat sinks has been studied extensively, there is still a demand for improvements in overall thermal performance of miniature heat transfer exchangers. Experimental investigation and sophisticated heat transfer calculations with respect to heat transfer devices are still needed. In this work, a time-dependent experimental study of subcooled boiling was carried out for FC-72 flow in a heat sink, comprising of five asymmetrically heated minichannels. The heater surface temperature was continuously monitored by an infrared camera. The boiling heat transfer characteristics were investigated and the effect of the mass flow rate on the heat transfer coefficient was studied. In order to solve the heat transfer problem related to time-dependent flow boiling, two numerical methods, based on the FEM were applied, and based on the Trefftz functions (FEMT) and using the ADINA program. The results achieved with these two calculation methods were explored with an emphasis on the impact of the mass flow rate (range from 5 to 55 kg/h) on the resulting heat transfer coefficient. It was found that, with increasing mass flow, the heat transfer coefficient increased. Good agreement was found between the heat transfer coefficients, determined according to two numerical methods and the simple 1D calculation method. Full article

(This article belongs to the Special Issue Fluid Flow and Heat Transfer: Latest Advances and Prospects)

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