Cooling Technologies and Applications

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Applied Sciences applsci	2.5	5.3	2011	17.8 Days	CHF 2400
Electronics electronics	2.6	5.3	2012	16.8 Days	CHF 2400
Energies energies	3.0	6.2	2008	17.5 Days	CHF 2600
Materials materials	3.1	5.8	2008	15.5 Days	CHF 2600
Thermo thermo	-	2.1	2021	21.6 Days	CHF 1000

21 pages, 5606 KiB

Open AccessArticle

Operation Optimization of Thermal Management System of Deep Metal Mine Based on Heat Current Method and Prediction Model

by Wenpu Wang, Wei Shao, Shuo Wang, Junling Liu, Kun Shao, Zhuoqun Cao, Yu Liu and Zheng Cui

Energies 2023, 16(18), 6626; https://doi.org/10.3390/en16186626 - 14 Sep 2023

Cited by 3 | Viewed by 1184

Abstract

With the increasing depth of metal mining, thermal damage has become a serious problem that restricts mining. The thermal management system of refrigeration and ventilation is an indispensable technology in the mining of deep metal mines, which plays a key role in improving [...] Read more.

With the increasing depth of metal mining, thermal damage has become a serious problem that restricts mining. The thermal management system of refrigeration and ventilation is an indispensable technology in the mining of deep metal mines, which plays a key role in improving the thermal and humid environment of mines. Optimizing the performance of refrigeration and ventilation systems to reduce energy consumption has become a focus of researchers’ attention. Based on the heat current method, this research establishes the overall heat transfer and flow constraint model of the refrigeration and ventilation system, and proposes an iterative algorithm that combines the refrigerator energy consumption model and the artificial neural network model of heat exchangers. The Lagrange multiplier method is used to optimize the system with the goal of minimizing the total power consumption of the system. The results show that under 9.1 kW cooling load conditions, the total energy consumption of the system reduces by 16.5%, and the COP of the refrigerator increases by 11.6%. The optimization results provide significant guidance for the production and energy consumption reduction of the deep metal mines. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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23 pages, 1657 KiB

Open AccessFeature PaperArticle

Simulation-Based Sizing of a Secondary Loop Cooling System for a Refrigerated Vehicle

by Maximilian Lösch, Markus Fallmann, Agnes Poks and Martin Kozek

Energies 2023, 16(18), 6459; https://doi.org/10.3390/en16186459 - 6 Sep 2023

Viewed by 1220

Abstract

Refrigerated transport by road is essential for the food industry but also contributes significantly to global energy consumption. In particular, last-mile transport, where the doors of the cooling chamber are opened frequently, puts a strain on energy efficiency and temperature control due to [...] Read more.

Refrigerated transport by road is essential for the food industry but also contributes significantly to global energy consumption. In particular, last-mile transport, where the doors of the cooling chamber are opened frequently, puts a strain on energy efficiency and temperature control due to the high heat ingress from outside into the cooling chamber. These difficulties can be reduced by thermal energy storage systems, such as secondary loop refrigeration systems, if combined with a sophisticated control scheme. Although the storage capacity of such systems is critical for the overall performance of the cooling system, little research was performed regarding the sizing of the secondary loop thermal storage capacity. Therefore, this article examines the effect of the secondary loop thermal storage capacity on energy consumption and controller performance utilizing closed-loop simulations of a refrigerated vehicle model. Both a mixed-integer model predictive control scheme that can anticipate door openings and a conventional temperature controller are analyzed. An optimal thermal storage capacity of the secondary loop is found with the model predictive controller, whereas the conventional controller cannot exploit the secondary loop and thus shows significantly inferior performance. By using a dimensionless parameter for the thermal storage capacity of the secondary loop, the optimum found can be easily applied to refrigerated vehicles with various cooling chamber dimensions. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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22 pages, 14827 KiB

Open AccessArticle

Study on Flow and Heat Transfer Characteristics and Anti-Clogging Performance of Tree-Like Branching Microchannels

by Linqi Shui, Zhongkai Hu, Hang Song, Zhi Zhai and Jiatao Wang

Energies 2023, 16(14), 5531; https://doi.org/10.3390/en16145531 - 21 Jul 2023

Cited by 5 | Viewed by 1252

Abstract

In this paper, a tree-like branching microchannel with bifurcating interconnections is designed for gas turbine blade cooling. A theoretical analysis, experimental study, and numerical simulation of the heat transfer and hydrodynamic characteristics of the tree-like branching microchannel is performed, and the influence of [...] Read more.

In this paper, a tree-like branching microchannel with bifurcating interconnections is designed for gas turbine blade cooling. A theoretical analysis, experimental study, and numerical simulation of the heat transfer and hydrodynamic characteristics of the tree-like branching microchannel is performed, and the influence of the total number of branching levels m on the anti-clogging performance is also studied. The results indicate that the total heat transfer ratio and pressure drop ratio are closely related to the structur ne parameters. The comprehensive thermal performance increase with an increase in the ratio of L_b/L₀ and fractal dimension D. Nu/Nu_s, f/f_s, and η are increased as m increases from 3 to 5. Furthermore, the tree-like microchannel network exhibits robustness for cooling gas turbine blades. A greater total number of branching levels and a higher Re number are advantageous for enhancing the anti-clogging performance of the tree-like branching microchannel. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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15 pages, 5215 KiB

Open AccessArticle

Comparison and Evaluation of Transport Property Prediction Performance of Supercritical Hydrocarbon Aviation Fuels and Their Pyrolyzed Products via Endothermic Reactions

by Sung-rok Hwang and Hyung Ju Lee

Energies 2023, 16(13), 5195; https://doi.org/10.3390/en16135195 - 6 Jul 2023

Cited by 1 | Viewed by 973

Abstract

This study presents results of predicting the transport properties of hydrocarbon aviation fuels and their decomposed products after pyrolysis. Twenty-seven pure substances and two types of mixture, including both low and high molecular weight hydrocarbons as well as hydrogen, are considered. The specified [...] Read more.

This study presents results of predicting the transport properties of hydrocarbon aviation fuels and their decomposed products after pyrolysis. Twenty-seven pure substances and two types of mixture, including both low and high molecular weight hydrocarbons as well as hydrogen, are considered. The specified temperature and pressure ranges, 300 to 1000 K and 0.1 to 5.0 MPa, respectively, correspond to representative operating conditions of a hydrocarbon aviation fuel that circulates as a coolant in the regenerative cooling system of a hypersonic vehicle and include the critical temperatures and pressures of most of the hydrocarbon fuels of interest. Four methods are adopted for the prediction of viscosity and thermal conductivity; the Brule-Starling method is used to predict viscosity, the Modified Propane TRAPP method for thermal conductivity, and the Methane TRAPP, Propane TRAPP, and Chung et al. methods are used for both transport properties. A comparison of the total average values concludes that the Chung et al. and Brule-Starling methods perform best in predicting the viscosity of all substances ranging from hydrogen to high molecular weight hydrocarbons in the temperature and pressure ranges specified in the current study. The quantified comparison by the total average also confirms that the Modified Propane TRAPP method best predicts the thermal conductivity of all of the 29 substances over the set temperature and pressure ranges, although the Propane TRAPP and Chung et al. methods offer a similar level of accuracy. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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18 pages, 2404 KiB

Open AccessArticle

Experimental Study of the Heat Flow and Energy Consumption during Liquid Cooling Due to Radiative Heat Transfer in Winter

by Alexandr Tsoy, Alexandr Granovskiy, Dmitriy Koretskiy, Diana Tsoy-Davis, Nikita Veselskiy, Mikhail Alechshenko, Alexandr Minayev, Inara Kim and Rita Jamasheva

Energies 2023, 16(13), 4865; https://doi.org/10.3390/en16134865 - 22 Jun 2023

Viewed by 1259

Abstract

Radiation cooling is a passive energy saving cooling technology. The process of cooling heat transfer liquid due to the combined effect of night radiative cooling and convection of air at negative temperatures (in winter) is studied. The radiator used for cooling was built [...] Read more.

Radiation cooling is a passive energy saving cooling technology. The process of cooling heat transfer liquid due to the combined effect of night radiative cooling and convection of air at negative temperatures (in winter) is studied. The radiator used for cooling was built into the roof of the building. Its radiating plate was made of a steel sheet coated with zinc oxide. In it, heat dissipation was carried out both from the upper and lower sides of the radiating plate. The experimental values of the heat flux ranged from 20 to 80 W·m⁻² at a temperature difference between heat transfer liquid and air from 5 to 15 °C and ambient air temperature from −17 to +5 °C. The correctness of the model for calculating the heat flux in winter conditions was confirmed. A theoretical calculation showed that, in winter, the heat flux removed by the radiator will be 15% less than the heat flux in summer. The amount of heat transferred per watt of electrical power of the refrigeration unit reached 8 W·W⁻¹. To keep the refrigeration unit with radiative heat transfer more efficient than in a conventional vapor compression chiller, the heat transfer liquid temperature should be 6 °C above the atmospheric temperature air. The results of the study show that radiative cooling can be used in winter and may be useful for the development of energy-efficient cooling systems for various purposes (air conditioning, industrial cooling systems and fruit storage chambers). Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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16 pages, 2536 KiB

Open AccessArticle

On the Use of Ultrasonic Flowmeters for Cooling Energy Metering and Sub-Metering in Direct Expansion Systems

by Ciro Aprea, Laura Canale, Marco Dell’Isola, Giorgio Ficco, Andrea Frattolillo, Angelo Maiorino and Fabio Petruzziello

Energies 2023, 16(12), 4775; https://doi.org/10.3390/en16124775 - 17 Jun 2023

Viewed by 1331

Abstract

The Energy Efficiency Directive (EED, Directive 2012/27/EU) has made mandatory the installation of individual metering systems in the case of buildings with centralized heating/cooling and hot water sources (multi-apartment and multi-purpose buildings), provided it is economically and technically feasible. Individual metering of heating/cooling [...] Read more.

The Energy Efficiency Directive (EED, Directive 2012/27/EU) has made mandatory the installation of individual metering systems in the case of buildings with centralized heating/cooling and hot water sources (multi-apartment and multi-purpose buildings), provided it is economically and technically feasible. Individual metering of heating/cooling systems is mainly based on thermal energy meters (TEM), which are widely used for direct metering in heating applications. On the other hand, direct metering of energy consumption in cooling systems still represents a challenge, given the different types of cooling units and the lack of regulations from the technical and legal points of view. In this context, this paper briefly overviews the available centralized cooling systems and the possible solutions for metering and sub-metering, which depend on the specific application. Vapour Compression Refrigeration (VCR) systems are spreading worldwide for air conditioning applications. Particular attention has been paid to the direct metering of cooling energy and specifically to refrigerant flow rate measurement, which represents a critical issue because of the small-diameter pipes and the different thermodynamic properties of the fluid used. Thus, an experimental campaign has been developed and carried out in order to compare a clamp-on ultrasonic flowmeter with a more accurate Coriolis one in a direct expansion (DE) system. The experimental tests have been performed at two different temperature conditions, showing a relative error in the mass flow rate measurements within ±10%. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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20 pages, 10389 KiB

Open AccessArticle

Comparing the Performance of a Straight-Channel Heat Sink with Different Channel Heights: An Experimental and Numerical Study

by Mahsa Hajialibabaei, Mohamad Ziad Saghir and Yusuf Bicer

Energies 2023, 16(9), 3825; https://doi.org/10.3390/en16093825 - 29 Apr 2023

Cited by 4 | Viewed by 1845

Abstract

Straight-channel heat sinks are widely used as a cooling method for electronic devices and lithium battery thermal management. This study aims to enhance the thermal performance of a straight-channel heat sink while decreasing the pressure drop. In this design, the height of inside [...] Read more.

Straight-channel heat sinks are widely used as a cooling method for electronic devices and lithium battery thermal management. This study aims to enhance the thermal performance of a straight-channel heat sink while decreasing the pressure drop. In this design, the height of inside channels is reduced to provide open space above the channel while the size of the heat sink remains constant. Both experimental investigation and numerical analysis were conducted to study the thermal efficiency of heat sinks with varying heights, at flow rates ranging from 6.94 to 19.56 m³/s and heat fluxes between 3.8 and 7.43 W/cm². The comparison is carried out between channels with four different heights in terms of temperature distribution, local Nusselt number, velocity, and flow characteristic. The results indicate that lowering the height of the channel from 12.7 to 7 and 4 mm raises the highest temperature of the heat sink, whereas the change in height to 10 mm reduces the temperature. Furthermore, increasing the flow rate has a higher impact on improving the Nusselt number in channels with a height of 10 mm. When the height is decreased from 12.7 to 10 mm, the performance evaluation criterion is obtained higher than one for all flow rates. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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17 pages, 4464 KiB

Open AccessArticle

Drop-In Replacement of R134a in a Household Refrigerator with Low-GWP Refrigerants R513A, R516A, and R1234ze(E)

by Juan M. Belman-Flores, Yonathan Heredia-Aricapa, Juan J. García-Pabón, Vicente Pérez-García and César G. Pérez-Reguera

Energies 2023, 16(8), 3422; https://doi.org/10.3390/en16083422 - 13 Apr 2023

Cited by 3 | Viewed by 4399

Abstract

This study proposes the experimental evaluation of alternative refrigerants with low global warming potentials (GWPs) such as R1234ze(E), R513A, and the mixture R516A as a drop-in replacement for R134a in a domestic refrigerator with a volumetric capacity of 513 L. Initially, the optimal [...] Read more.

This study proposes the experimental evaluation of alternative refrigerants with low global warming potentials (GWPs) such as R1234ze(E), R513A, and the mixture R516A as a drop-in replacement for R134a in a domestic refrigerator with a volumetric capacity of 513 L. Initially, the optimal charge for each refrigerant was defined based on the minimum energy consumption of the refrigerator, then the thermal and energy performance of the refrigerator was evaluated. Finally, a total equivalent warming impact analysis (TEWI) was performed. The main results indicated that the optimal charge of the alternative refrigerants was below that corresponding to R134a (105 g), of which R516A (86 g) presented the greatest charge reduction. Regarding the average temperature of the refrigerator compartments, very adequate thermal conditions were observed; thus, the alternative refrigerants showed very similar conditions to R134a. For the coefficient of performance (COP) and considering R134a as a reference, it was observed that R513A presented the greatest reduction of around 28%, while R1234ze(E) showed an increase of 13% in relation to R134a. Finally, the TEWI analysis showed R1234ze(E) as the refrigerant with the least impact. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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15 pages, 3472 KiB

Open AccessArticle

Cost-Effective and Efficient Cool Nanopigments Based on Oleic-Acid-Surface-Modified ZnO Nanostructured

by Ashraf H. Farha, Abdullah F. Al Naim and Shehab A. Mansour

Materials 2023, 16(6), 2159; https://doi.org/10.3390/ma16062159 - 8 Mar 2023

Cited by 3 | Viewed by 1711

Abstract

In this paper, as-synthesized and oleic acid (OA)-surface-treated zinc oxide (ZnO) nanocrystals were successfully synthesized and investigated for cool-nanopigment applications. ZnO nanocrystals were synthesized using the thermal decomposition method. The OA-surface-treated ZnO sample was obtained with an OA:ZnO ratio of 1:1. The structural, [...] Read more.

In this paper, as-synthesized and oleic acid (OA)-surface-treated zinc oxide (ZnO) nanocrystals were successfully synthesized and investigated for cool-nanopigment applications. ZnO nanocrystals were synthesized using the thermal decomposition method. The OA-surface-treated ZnO sample was obtained with an OA:ZnO ratio of 1:1. The structural, optical and morphological properties of the samples were characterized via X-ray diffraction (XRD), Fourier transform infrared (FTIR), UV-VIS-NIR diffused reflectance spectroscopy (DRS) and field-emission scanning electron microscopy (FE-SEM) techniques. ZnO nanocrystals possess a well-known zincate phase of ZnO, as confirmed for the as-synthesized sample with a reduction in the integrity of the ZnO crystalline structure upon the application of the OA coating. XRD peaks broadening and decreasing in crystallite size were obtained upon the surface modification of the ZnO by OA. The average crystallite size decreased from 31.5 to 17.4 nm, and the surface area changed from 23.37 to 7.48 m²/g upon OA treatment. These changes were attributed to the well-capping of the ZnO nanoparticles by OA, and, furthermore, OA increased the dispersion of the nanoparticles. The optical band gap of the investigated samples demonstrated a blue shift from 3.06 eV to 3.22 eV upon treatment. Both samples showed high NIR reflectance (

R_{N I R}^{*}

) values, which makes them well qualified for use as cool nanopigments. Additionally, the as-synthesized sample showed an

R_{N I R}^{*}

value higher than that of the treated sample. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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59 pages, 19428 KiB

Open AccessReview

A Review of Nanoparticle Material Coatings in Passive Radiative Cooling Systems Including Skylights

by Gopalakrishna Gangisetty and Ron Zevenhoven

Energies 2023, 16(4), 1975; https://doi.org/10.3390/en16041975 - 16 Feb 2023

Cited by 10 | Viewed by 8728

Abstract

Daytime passive radiative cooling (DPRC) has remained a challenge over the past decades due to the necessity of precisely defined materials with a significantly high emissivity of thermal radiation within the atmospheric transparent window wavelength range (8–13 μm) as well as high reflectivity [...] Read more.

Daytime passive radiative cooling (DPRC) has remained a challenge over the past decades due to the necessity of precisely defined materials with a significantly high emissivity of thermal radiation within the atmospheric transparent window wavelength range (8–13 μm) as well as high reflectivity in the solar spectrum (0.2–3 μm). Fortunately, recent advances and technological improvements in nanoscience and metamaterials are making it possible to create diverse metamaterials. This enables the production of DPRC in direct solar irradiation. The development of a material that is appropriate for effective DPRC is also a noteworthy development in this field of technology. This review gives a thorough introduction and discussion of the fundamental ideas, as well as the state-of-the-art and current trends in passive radiative cooling, and describes the cutting-edge materials and various photonic radiator structures that are useful in enhancing net cooling performance. This work also addresses a novel skylight window that offers passive cooling developed at the Åbo Akademi (ÅA) University, Finland. In conclusion, nanomaterials and nanoparticle-based coatings are preferred over all other approaches for commercialization in the future because of their low cost, the ability for large-scale production, simplicity in fabrication, and great potential for further increasing cooling performance. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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12 pages, 3871 KiB

Open AccessArticle

Numerical Simulation of the Heat Transfer and Flow Characteristics of Pulse Tube Refrigerators

by Yuan Meng, Zheng Cui, Wei Shao and Wanxiang Ji

Energies 2023, 16(4), 1906; https://doi.org/10.3390/en16041906 - 14 Feb 2023

Cited by 1 | Viewed by 1562

Abstract

Because of the unequal diameter between the pulse tube and the heat exchangers at the two sides, the fluid entering the pulse tube from the heat exchanger easily forms a complex disturbing flow in the pulse tube, which causes energy loss and affects [...] Read more.

Because of the unequal diameter between the pulse tube and the heat exchangers at the two sides, the fluid entering the pulse tube from the heat exchanger easily forms a complex disturbing flow in the pulse tube, which causes energy loss and affects the performance of a pulse tube refrigerator. This study proposes a numerical model for predicting the flow and heat transfer characteristics of pulse tube refrigerators. Three cases of adding conical tube transitions between the pulse tube and the heat exchanger are studied, and the results indicate that the conical tube transition can reduce the fluid flow velocity at the inlet and outlet of the pulse tube and reduce the size of the vortex at the boundary of the pulse tube. In comparison with the tapered transition of 45° on only one side of the pulse tube, both sides can maintain the temperature gradient, effectively decrease the effect of the disturbing flow, and significantly improve the cooling performance of the pulse tube. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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28 pages, 10533 KiB

Open AccessArticle

Numerical Modeling of Shell-and-Tube-like Elastocaloric Regenerator

by Žiga Ahčin, Parham Kabirifar, Luka Porenta, Miha Brojan and Jaka Tušek

Energies 2022, 15(23), 9253; https://doi.org/10.3390/en15239253 - 6 Dec 2022

Cited by 12 | Viewed by 2702

Abstract

Elastocaloric cooling is considered an environmentally friendly future alternative to vapor-compression technology. Recently, a shell-and-tube-like elastocaloric regenerator loaded in compression has demonstrated record-breaking heat-pumping performance and fatigue-resistant operation. The aim of this work is thus to present a new 1D numerical model to [...] Read more.

Elastocaloric cooling is considered an environmentally friendly future alternative to vapor-compression technology. Recently, a shell-and-tube-like elastocaloric regenerator loaded in compression has demonstrated record-breaking heat-pumping performance and fatigue-resistant operation. The aim of this work is thus to present a new 1D numerical model to simulate and optimize the operation of an elastocaloric regenerator with a shell-and-tube-like design. In the first part of this work, the superelastic and elastocaloric properties of a single NiTi tube, which serve as input data for the numerical model, were determined through experimental characterization and phenomenological modeling. In the second part, the results of the numerical model were compared with the experimentally obtained results. Relatively good agreement was found regarding the temperature span, cooling and heating power, and COP values, which indicates that the developed numerical model could be used for accurate optimization of shell-and-tube-like elastocaloric regenerators. Finally, the effects of operating conditions and hysteresis losses on the performance of the shell-and-tube-like elastocaloric regenerator are modeled and discussed. This work shows that the shell-and-tube-like elastocaloric regenerator with this configuration can achieve a maximum temperature span of more than 50 K at zero-thermal-load conditions and a maximum cooling/heating power of up to 4000 W·kg⁻¹ and COP of about 4 (at zero temperature span). Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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18 pages, 8070 KiB

Open AccessArticle

Experimental Optimization of the Compound Angled Asymmetric Laidback Fan Shaped Film Cooling Hole

by Ye Rim Jo, Jin Young Jeong and Jae Su Kwak

Energies 2022, 15(21), 7985; https://doi.org/10.3390/en15217985 - 27 Oct 2022

Cited by 2 | Viewed by 1662

Abstract

In this study, the effect of shape variables on the film cooling effectiveness of the compound angled asymmetric laidback fan shaped hole was experimentally investigated, and the optimum values of select design variables were presented. Among the shape variables of the compound angled [...] Read more.

In this study, the effect of shape variables on the film cooling effectiveness of the compound angled asymmetric laidback fan shaped hole was experimentally investigated, and the optimum values of select design variables were presented. Among the shape variables of the compound angled asymmetric laidback fan shaped hole, the windward and leeward lateral expansion angles and the compound angle were selected as design variables. Test points were chosen using the central composite design method, and the selected design variables were optimized using the Kriging model. The film cooling effectiveness was measured using the PSP technique, and the experiment was conducted under the two density ratios of 1.5 and 2.0 and four blowing ratios of 1.0, 1.5, 2.0, and 2.5. Experimental results showed that the film cooling performance was improved for higher density ratios than lower density ratios. The main effects analysis indicated that larger windward and leeward lateral expansion angles induced higher film cooling effectiveness; however, the compound angle did not show consistent results. For the optimized hole at the density ratio 2.0, the results indicated that the overall averaged film cooling effectiveness of the optimized compound angled asymmetric laidback fan shaped hole was higher than that of the optimized fan shape holes of previous literature. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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11 pages, 2700 KiB

Open AccessArticle

Effective Cooling System for Solar Photovoltaic Cells Using NEPCM Impingement Jets

by Javad Mohammadpour, Fatemeh Salehi and Ann Lee

Thermo 2022, 2(4), 383-393; https://doi.org/10.3390/thermo2040026 - 26 Oct 2022

Cited by 1 | Viewed by 2015

Abstract

Attention to photovoltaic (PV) cells to convert solar irradiation into electricity is significantly growing for domestic usage and large-scale projects such as solar farms. However, PV efficiency decreases on hot days. This paper proposes an effective cooling technique consisting of a 2% nano [...] Read more.

Attention to photovoltaic (PV) cells to convert solar irradiation into electricity is significantly growing for domestic usage and large-scale projects such as solar farms. However, PV efficiency decreases on hot days. This paper proposes an effective cooling technique consisting of a 2% nano encapsulated phase change material (NEPCM) slurry and impinging jets (IJs) in a PV system. The impact of five influencing parameters on PV efficiency is studied using a multi-phase volume of fluid (VOF) model encompassing the effects of solar irradiation, latent heat, mass flow rate, number of nozzles, and jet-to-surface distance. The maximum efficiency of 15.82% is achieved under irradiation of 600 W/m². The latent heat shows a slight improvement at the low particle concentration. Increasing the mass flow rate to 0.12 kg/s enhances the PV output power by 17.32%. While the PV performance is shown to be improved over the increment of the number of nozzles, the jet-to-surface spacing of 5.1 mm records a remarkable PV surface temperature reduction to 33.8 °C, which is the ideal operating temperature for the PV panel. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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23 pages, 7815 KiB

Open AccessArticle

The Influence of Droplet Distribution Coverage and Additives on the Heat Transfer Characteristics of Spray Cooling under the Influence of Different Parameters

by Qian Niu, Yu Wang and Na Kang

Appl. Sci. 2022, 12(18), 9167; https://doi.org/10.3390/app12189167 - 13 Sep 2022

Viewed by 1567

Abstract

For the objective of enhancing the heat transfer ability of spray cooling, a single-nozzle open-loop spray cooling experiment platform was established with a data measuring system. Based on the surface heat transfer coefficient obtained from the experiment, combined with the visualization system to [...] Read more.

For the objective of enhancing the heat transfer ability of spray cooling, a single-nozzle open-loop spray cooling experiment platform was established with a data measuring system. Based on the surface heat transfer coefficient obtained from the experiment, combined with the visualization system to observe the distribution of droplets during the spray cooling process, the influence of heating power, medium flow rate, nozzle height and typical additives on heating surface coverage and heat transfer characteristics were investigated. The criterion non-dimensional criteria equations for Nu, Re, Pr and size coefficients were fitted and analyzed in comparison with experimental data. The main conclusions are as follows: considering the temperature distribution characteristics of the heating surface and the shape of the spray cone, the heat transfer performance can be optimized by increasing the coverage rate under high heat flux when the flow rate changes, appropriately reducing the coverage rate under low heat flux, and appropriately reducing the coverage rate when the height changes, which creates complete coverage in the droplet concentration area to improve the surface heat transfer capacity. Furthermore, the heat transfer coefficients were improved by 29.3%, 21.8% and 23.8% with different additives (CTAB, ethanol and CTAB–ethanol mixtures) in the working fluid. Each solution had an optimal concentration and heat transfer deterioration was observed at high concentrations. When using non-dimensional criteria equations for parameter calculations, the data are more accurate after considering the effect of dimensional coefficients. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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14 pages, 3557 KiB

Open AccessArticle

Multi-Objective Optimization of a Multilayer Wire-on-Tube Condenser: Case Study R134a, R600a, and R513A

by Yonathan Heredia-Aricapa, Juan M. Belman-Flores, Jorge A. Soria-Alcaraz, Vicente Pérez-García, Francisco Elizalde-Blancas, Jorge A. Alfaro-Ayala and José Ramírez-Minguela

Energies 2022, 15(17), 6101; https://doi.org/10.3390/en15176101 - 23 Aug 2022

Cited by 1 | Viewed by 2123

Abstract

This study presents the optimization of a multilayer wire-on-tube condenser exposed to forced convection, using the Optimized Multi-objective Particle Swarm Optimization (OMOPSO) algorithm. The maximization of the heat transfer and the minimization of the heat exchange area were defined as objective functions. In [...] Read more.

This study presents the optimization of a multilayer wire-on-tube condenser exposed to forced convection, using the Optimized Multi-objective Particle Swarm Optimization (OMOPSO) algorithm. The maximization of the heat transfer and the minimization of the heat exchange area were defined as objective functions. In the optimization process, the variations of eight geometric parameters of the condenser were analyzed, and the Multi-objective Evolutionary Algorithm based on Decomposition (MOEAD), Non-dominated Sorting Genetic Algorithm-II (NSGAII), and OMOPSO algorithms were statistically explored. Furthermore, the condenser optimization analysis was extended to the use of alternative refrigerants to R134a such as R600a and R513A. Among the relevant results, it can be commented that the OMOPSO algorithm presented the best option from the statistical point of view compared to the other two algorithms. Thus, optimal designs for the wire-on-tube condenser were defined for three proposed study cases and for each refrigerant, providing an overview of compact designs. Likewise, the reduction of the condenser area was analyzed in more detail, presenting a maximum reduction of 15% for the use of R134a compared to for the current design. Finally, the crossflow condition was studied with respect to the current one, concluding in a greater heat transfer and a smaller heat exchange surface. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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21 pages, 3939 KiB

Open AccessArticle

Experimental Study of Thermal and Pressure Performance of Porous Heat Sink Subjected to Al₂O₃-H₂O Nanofluid

by Oguzhan OZBALCI, Ayla DOGAN and Meltem ASILTURK

Electronics 2022, 11(15), 2471; https://doi.org/10.3390/electronics11152471 - 8 Aug 2022

Cited by 1 | Viewed by 2247

Abstract

With the developing technology, the dimensions of electronic systems are becoming smaller, and their performance and the amount of energy they need increases. This situation causes the electronic components to heat up more and the existing cooling systems to become inadequate. In this [...] Read more.

With the developing technology, the dimensions of electronic systems are becoming smaller, and their performance and the amount of energy they need increases. This situation causes the electronic components to heat up more and the existing cooling systems to become inadequate. In this study, instead of the fins used in existing systems, 10 PPI and 40 PPI PHS were placed inside a water block, and the Al₂O₃-H₂O nanofluid at a mass fraction of 0.1% was used as the cooling fluid. Experiments were carried out under constant heat flux of 454.54 W/m² and 1818.18 W/m², with volumetric flow rates varying between 100 mL/min and 800 mL/min. The heat transfer results were compared with the results obtained from the base fluid and the empty surface. The results showed that the nanofluid reduced the surface temperatures compared to the base fluid. Especially when PHSs were used together with the nanofluid, a significant increase in heat transfer occurred compared to the empty surface. The highest heat transfer was observed when both the nanofluid and 40 PPI PHS were used together. In addition, the highest thermal performance value was determined as 1.25 times compared to the empty surface when the nanofluid and 10 PPI PHS were used together. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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23 pages, 3845 KiB

Open AccessArticle

A Comprehensive Energy Model for an Optimal Design of a Hybrid Refrigerated Van

by Angelo Maiorino, Adrián Mota-Babiloni, Fabio Petruzziello, Manuel Gesù Del Duca, Andrea Ariano and Ciro Aprea

Energies 2022, 15(13), 4864; https://doi.org/10.3390/en15134864 - 2 Jul 2022

Cited by 7 | Viewed by 2382

Abstract

The path towards decarbonization requires a progressive adaptation of all refrigeration systems, but only stationary ones have been intensely studied to improve their environmental performance. However, refrigerated transport is vital in the cold chain and must be considered in the green transition. In [...] Read more.

The path towards decarbonization requires a progressive adaptation of all refrigeration systems, but only stationary ones have been intensely studied to improve their environmental performance. However, refrigerated transport is vital in the cold chain and must be considered in the green transition. In this paper, we propose a model for a hybrid refrigerated van that includes photovoltaic panels and electric batteries to decrease total greenhouse gas emissions from the engine. Thermal, electrical, and battery sub-models are considered and integrated into the comprehensive hybrid solar-powered refrigerated van model. Different technologies are compared, including lithium and lead-acid batteries and three different types of photovoltaic panels. The model was validated regarding van fuel consumption, showing a 4% deviation. Single and multiple delivery scenarios are considered to assess the energy, economic, and environmental benefits. Monthly CO₂,e emissions could be reduced by 20% compared to a standard refrigerated van. Despite the environmental benefits provided by this sustainable solution, the payback period is still too long (above 20 years) because of the necessary investment to adapt the vehicle and considering fuel and electricity prices currently. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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12 pages, 3119 KiB

Open AccessArticle

Optimizing the Power Usage of Anti-Sweat Heaters in Glass-Door Refrigerators According to the Dew Point

by Iztok Humar, Uroš Hudomalj, Alexander Marinšek and Mark Umberger

Energies 2022, 15(13), 4601; https://doi.org/10.3390/en15134601 - 23 Jun 2022

Cited by 1 | Viewed by 1595

Abstract

Putting glass doors on the display cases of refrigerators is one of the most efficient ways to reduce the energy consumption of supermarkets. However, the glass fogs up when opening the door because of the difference in air temperature inside and outside of [...] Read more.

Putting glass doors on the display cases of refrigerators is one of the most efficient ways to reduce the energy consumption of supermarkets. However, the glass fogs up when opening the door because of the difference in air temperature inside and outside of the refrigerator, thereby obscuring the view. To defog the glass, anti-sweat heaters (ASHs) are used. In this paper, the power usage of ASHs according to changes in the dew point (DP) inside a supermarket were evaluated for two types of ASH, i.e., the door-frame ASH and the glass ASH. The evaluation was based on measurements of the condensation on the glass doors of vertical display cases, used for the preservation of frozen foodstuffs. A mathematical model of the correlation between the ASH’s power usage and the DP was developed and used for predicting the long-term energy savings. The savings were calculated based on the measured DPs inside the supermarket, which were extrapolated over a longer time period based on their correlation with the outside DPs. Regulating the door-frame ASH according to the DP resulted in an 84.6% reduction in energy consumption and a 90.1% reduction in the case of the glass ASH, compared to the current state. The correlation between the DPs inside and outside the supermarket served as a basis for the proposed implementation of the power usage regulation of the ASH according to the DP. Full article

(This article belongs to the Topic Cooling Technologies and Applications)

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