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Refrigeration Systems and Applications 2019

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "J: Thermal Management".

Deadline for manuscript submissions: closed (30 September 2019) | Viewed by 44262

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Special Issue Editors

Prof. Dr. Ciro Aprea

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Department of Industrial Engineering, University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, SA, Italy
Interests: thermal engineering; heat exchangers; heat transfer; vapour compression refrigeration systems; autocascade systems; magnetic refrigeration; elastocaloric refrigeration; electrocaloric refrigeration
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Dr. Angelo Maiorino

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Department of Industrial Engineering, University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, SA, Italy
Interests: thermal engineering; refrigeration; magnetic refrigeration; elastocaloric refrigeration; electrocaloric refrigeration; artificial neural network in the field of refrigeration; natural refrgierants; transcritical refrigeration systems
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Dr. Adrián Mota Babiloni

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ISTENER Research Group, Department of Mechanical Engineering and Construction, Universitat Jaume I, E12071 Castelló de la Plana, Spain
Interests: refrigeration; heat pumps; low global warming potential refrigerants; organic Rankine cycle; energy conversion; phase change materials; energy efficiency
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Special Issue Information

Dear Colleagues,

We are pleased to invite you to submit your high-level scientific papers to a Special Issue of Energies (IF 2.676) entitled “Refrigeration Systems and Applications”.

Refrigeration applications, mostly based on vapour compression systems, represent a significant contribution to global climate change. While refrigeration is necessary for the appropriate development of humanity, it is predicted that an increase in the number of refrigeration applications will worsen the issue of climate change. Hence, energy efficient systems with a lower contribution to global warming are required. In the last years, the research and development of new working fluid, technologies, and methodologies have provided an opportunity for the transition from vapour compression systems based on fluorine fluids to more sustainable solutions.

For instance, the potential advantages and drawbacks of hydrofluoroolefins are being investigated, and mixtures with hydrofluorocarbons are being developed to find trade-off solutions. Furthtermore, the applications of hydrocarbons are being extended to installations that require a lower refrigerant charge. Lower flammability refrigerants require new flammability and risk analysis studies to determine their possible hazard. Heat and mass transfer phenomena studies are being carried out for new pure and mixture refrigerants. Ejectors are being studied to increase energy performance in particular applications. Alternative technologies based on renewable energy or solid states, such as solar cooling or magnetic refrigeration, are being developed and integrated into new processes. The integration of phase change materials and slurries is becoming a new option. Finally, nanoparticles and nanofluids have opened an entirely new world of possibilities.

The literature available on these topics is still in an early stage, and these working fluids, technologies, and methodologies cannot be considered as mature. However, this creates significant potential for improving the energy efficiency as well as the operation and capacity range of these new approaches. The Special Issue “Refrigeration Systems and Applications” aims to encourage researchers to solve the concerns associated with these topics and to further the transition to more sustainable technologies and methodologies of tomorrow through theoretical, experimental, and review research on the different applications of refrigeration and associated topics.

We look forward to your submissions, which will be peer-reviewed by international colleagues with broad expertise in this specific topic.

Prof. Dr. Ciro Aprea
Prof. Dr. Angelo Maiorino
Dr. Adrián Mota Babiloni
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

new low global warming potential refrigerants
natural refrigerants
air source and ground source heat pumps
energy efficiency optimisation of refrigeration systems
advanced refrigeration architectures
solid state refrigeration technologies (magnetic, elastocaloric, and electrocaloric refrigeration)
refrigeration technologies based on renewable energies (solar cooling)
heat and mass transfer in refrigeration systems
phase change materials and slurries
determination of thermophysical and transport properties
nanorefrigerants and nanolubricants
control methods in refrigeration systems

Published Papers (11 papers)

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Research

21 pages, 6759 KiB

Open AccessFeature PaperArticle

Looking for Energy Losses of a Rotary Permanent Magnet Magnetic Refrigerator to Optimize Its Performances

by Angelo Maiorino, Antongiulio Mauro, Manuel Gesù Del Duca, Adrián Mota-Babiloni and Ciro Aprea

Energies 2019, 12(22), 4388; https://doi.org/10.3390/en12224388 - 19 Nov 2019

Cited by 7 | Viewed by 2855

Abstract

In this paper, an extensive study on the energy losses of a magnetic refrigerator prototype developed at University of Salerno, named ‘8MAG’, is carried out with the aim to improve the performance of such a system. The design details of ‘8MAG’ evidences both mechanical and thermal losses, which are mainly attributed to the eddy currents generation into the support of the regenerators (magnetocaloric wheel) and the parasitic heat load of the rotary valve. The latter component is fundamental since it imparts the direction of the heat transfer fluid distribution through the regenerators and it serves as a drive shaft for the magnetic assembly. The energy losses concerning eddy currents and parasitic heat load are evaluated by two uncoupled models, which are validated by experimental data obtained with different operating conditions. Then, the achievable coefficient of performance (COP) improvements of ‘8MAG’ are estimated, showing that reducing eddy currents generation (by changing the material of the magnetocaloric wheel) and the parasitic heat load (enhancing the insulation of the rotary valve) can lead to increase the COP from 2.5 to 2.8 (+12.0%) and 3.0 (+20%), respectively, and to 3.3 (+32%), combining both improvements, with an hot source temperature of 22 °C and 2 K of temperature span. Full article

(This article belongs to the Special Issue Refrigeration Systems and Applications 2019)

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14 pages, 1921 KiB

Open AccessArticle

HFO1234ze(e) As an Alternative Refrigerant for Ejector Cooling Technology

by Van Vu Nguyen, Szabolcs Varga and Vaclav Dvorak

Energies 2019, 12(21), 4045; https://doi.org/10.3390/en12214045 - 24 Oct 2019

Cited by 9 | Viewed by 2877

Abstract

The paper presented a mathematical assessment of selected refrigerants for the ejector cooling purpose. R1234ze(e) and R1234yf are the well-known refrigerants of hydrofluoroolefins (HFOs), the fourth-generation halocarbon refrigerants. Nature working fluids, R600a and R290, and third-generation refrigerant of halocarbon (hydrofluorocarbon, HFC), R32 and R152a, were selected in the assessment. A detail mathematical model of the ejector, as well as other components of the cycle, was built. The results showed that the coefficient of performance (COP) of R1234ze(e) was significantly higher than R600a at the same operating conditions. R1234yf’s performance was compatible with R290, and both were about 5% less than the previous two. The results also indicated that R152a offered the best performance among the selected refrigerants, but due to the high value of global warming potential, it did not fulfill the requirements of the current European refrigerant regulations. On the other hand, R1234ze(e) was the most suitable working fluid for the ejector cooling technology, thanks to its overall performance. Full article

(This article belongs to the Special Issue Refrigeration Systems and Applications 2019)

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11 pages, 2346 KiB

Open AccessArticle

Enhancement of a R-410A Reclamation Process Using Various Heat-Pump-Assisted Distillation Configurations

by Nguyen Van Duc Long, Thi Hiep Han, Dong Young Lee, Sun Yong Park, Byeng Bong Hwang and Moonyong Lee

Energies 2019, 12(19), 3776; https://doi.org/10.3390/en12193776 - 04 Oct 2019

Cited by 6 | Viewed by 3934

Abstract

Distillation for R-410A reclamation from a waste refrigerant is an energy-intensive process. Thus, various heat pump configurations were proposed to enhance the energy efficiency of existing conventional distillation columns for separating R-410A and R-22. One new heat pump configuration combining a vapor compression (VC) heat pump with cold water and hot water cycles was suggested for easy operation and control. Both advantages and disadvantages of each heat pump configuration were also evaluated. The results showed that the mechanical vapor recompression heat pump with top vapor superheating saved up to 29.5%, 100.0%, and 10.5% of the energy required in the condenser duty, reboiler duty, and operating cost, respectively, compared to a classical heat pump system, and 85.2%, 100.0%, and 60.8%, respectively, compared to the existing conventional column. In addition, this work demonstrated that the operating pressure of a VC heat pump could be lower than that of the existing distillation column, allowing for an increase in capacity of up to 20%. In addition, replacing the throttle valve with a hydraulic turbine showed isentropic expansion can decrease the operating cost by up to 20.9% as compared to the new heat pump configuration without a hydraulic turbine. Furthermore, the reduction in carbon dioxide emission was investigated to assess the environmental impact of all proposed sequences. Full article

(This article belongs to the Special Issue Refrigeration Systems and Applications 2019)

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18 pages, 3570 KiB

Open AccessArticle

Modeling of a PCM TES Tank Used as an Alternative Heat Sink for a Water Chiller. Analysis of Performance and Energy Savings

by Antonio Real-Fernández, Joaquín Navarro-Esbrí, Adrián Mota-Babiloni, Ángel Barragán-Cervera, Luis Domenech, Fernando Sánchez, Angelo Maiorino and Ciro Aprea

Energies 2019, 12(19), 3652; https://doi.org/10.3390/en12193652 - 24 Sep 2019

Cited by 10 | Viewed by 3327

Abstract

Phase change materials (PCMs) can be used in refrigeration systems to redistribute the thermal load. The main advantages of the overall system are a more stable energy performance, energy savings, and the use of the off-peak electric tariff. This paper proposes, models, tests, and analyzes an experimental water vapor compression chiller connected to a PCM thermal energy storage (TES) tank that acts as an alternative heat sink. First, the transient model of the chiller-PCM system is proposed and validated through experimental data directly measured from a test bench where the PCM TES tank is connected to a vapor compression-based chiller. A maximum deviation of 1.2 °C has been obtained between the numerical and experimental values of the PCM tank water outlet temperature. Then, the validated chiller-PCM system model is used to quantify (using the coefficient of performance, COP) and to analyze its energy performance and its dependence on the ambient temperature. Moreover, electrical energy saving curves are calculated for different ambient temperature profiles, reaching values between 5% and 15% taking the experimental system without PCM as a baseline. Finally, the COP of the chiller-PCM system is calculated for different temperatures and use scenarios, and it is compared with the COP of a conventional aerothermal chiller to determine the switch ambient temperature values for which the former provides energy savings over the latter. Full article

(This article belongs to the Special Issue Refrigeration Systems and Applications 2019)

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28 pages, 5159 KiB

Open AccessArticle

Thermodynamic Evaluation of LiCl-H₂O and LiBr-H₂O Absorption Refrigeration Systems Based on a Novel Model and Algorithm

by Jie Ren, Zuoqin Qian, Zhimin Yao, Nianzhong Gan and Yujia Zhang

Energies 2019, 12(15), 3037; https://doi.org/10.3390/en12153037 - 06 Aug 2019

Cited by 28 | Viewed by 5215

Abstract

An absorption refrigeration system (ARS) is an alternative to the conventional mechanical compression system for cold production. This study developed a novel calculation model using the Matlab language for the thermodynamic analysis of ARS. It was found to be reliable in LiCl-H₂O and LiBr-H₂O ARS simulations and the parametric study was performed in detail. Moreover, two 50 kW water-cooled single effect absorption chillers were simply designed to analyze their off-design behaviors. The results indicate that LiCl-H₂O ARS had a higher coefficient of performance (COP) and exergetic efficiency, particularly in the lower generator or higher condenser temperature conditions, but it operated more restrictively due to crystallization. The off-design analyses revealed that the preponderant performance of LiCl-H₂O ARS was mainly due to its better solution properties because the temperature of each component was almost the same for both chillers in the operation. The optimum inlet temperature of hot water for LiCl-H₂O (83 °C) was lower than that of LiBr-H₂O (98 °C). The cooling water inlet temperature should be controlled within 41 °C, otherwise the performances are discounted heavily. The COP and cooling capacity could be improved by increasing the temperature of hot water or chilled water properly, contrary to the exergetic efficiency. Full article

(This article belongs to the Special Issue Refrigeration Systems and Applications 2019)

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15 pages, 2396 KiB

Open AccessArticle

Enhancing the Heat Transfer in an Active Barocaloric Cooling System Using Ethylene-Glycol Based Nanofluids as Secondary Medium

by Ciro Aprea, Adriana Greco, Angelo Maiorino and Claudia Masselli

Energies 2019, 12(15), 2902; https://doi.org/10.3390/en12152902 - 28 Jul 2019

Cited by 27 | Viewed by 3251

Abstract

Barocaloric cooling is classified as environmentally friendly because of the employment of solid-state materials as refrigerants. The reference and well-established processes are based on the active barocaloric regenerative refrigeration cycle, where the solid-state material acts both as refrigerant and regenerator; an auxiliary fluid (generally water of water/glycol mixtures) is used to transfer the heat fluxes with the final purpose of subtracting heat from the cold heat exchanger coupled with the cold cell. In this paper, we numerically investigate the effect on heat transfer of working with nanofluids as auxiliary fluids in an active barocaloric refrigerator operating with a vulcanizing rubber. The results reveal that, as a general trend, adding 10% of copper nanoparticles in the water/ethylene-glycol mixture carries to +30% as medium heat transfer enhancement. Full article

(This article belongs to the Special Issue Refrigeration Systems and Applications 2019)

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13 pages, 6146 KiB

Open AccessArticle

Modeling and Optimizing a Chiller System Using a Machine Learning Algorithm

by Jee-Heon Kim, Nam-Chul Seong and Wonchang Choi

Energies 2019, 12(15), 2860; https://doi.org/10.3390/en12152860 - 25 Jul 2019

Cited by 26 | Viewed by 4787

Abstract

This study was conducted to develop an energy consumption model of a chiller in a heating, ventilation, and air conditioning system using a machine learning algorithm based on artificial neural networks. The proposed chiller energy consumption model was evaluated for accuracy in terms of input layers that include the number of input variables, amount (proportion) of training data, and number of neurons. A standardized reference building was also modeled to generate operational data for the chiller system during extended cooling periods (warm weather months). The prediction accuracy of the chiller’s energy consumption was improved by increasing the number of input variables and adjusting the proportion of training data. By contrast, the effect of the number of neurons on the prediction accuracy was insignificant. The developed chiller model was able to predict energy consumption with 99.07% accuracy based on eight input variables, 60% training data, and 12 neurons. Full article

(This article belongs to the Special Issue Refrigeration Systems and Applications 2019)

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14 pages, 12560 KiB

Open AccessArticle

CFD Simulation and Experimental Study of Working Process of Screw Refrigeration Compressor with R134a

by Huagen Wu, Hao Huang, Beiyu Zhang, Baoshun Xiong and Kanlong Lin

Energies 2019, 12(11), 2054; https://doi.org/10.3390/en12112054 - 29 May 2019

Cited by 10 | Viewed by 3852

Abstract

Twin-screw refrigeration compressors have been widely used in many industry applications due to their unique advantages. The performance of twin-screw refrigeration compressors is generally predicted by one-dimensional numerical simulation or empirical methods; however, the above methods cannot obtain the distribution of the fluid pressure field and temperature field inside the compressor. In this paper, a three-dimensional model was established based on the experimental twin-screw refrigeration compressor. The internal flow field of the twin-screw compressor was simulated by computational fluid dynamics (CFD) software using structured dynamic grid technology. The flow and thermodynamic characteristics of the fluid inside the compressor were analyzed. The distribution of the internal pressure field, temperature field, and velocity field in the compressor were obtained. Comparing the P-θ indicator diagram and the performance parameters of the compressor with the experimental results, it was found that the results of the three-dimensional numerical simulation were consistent with the experimental data. The maximum error was up to 2.578% on the adiabatic efficiency at the partial load working condition. The accuracy of the 3D numerical simulation of the screw compressors was validated and a new method for predicting the performance of twin-screw refrigeration compressors was presented that will be helpful in their design. Full article

(This article belongs to the Special Issue Refrigeration Systems and Applications 2019)

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22 pages, 4518 KiB

Open AccessArticle

Evaluating Magnetocaloric Effect in Magnetocaloric Materials: A Novel Approach Based on Indirect Measurements Using Artificial Neural Networks

by Angelo Maiorino, Manuel Gesù Del Duca, Jaka Tušek, Urban Tomc, Andrej Kitanovski and Ciro Aprea

Energies 2019, 12(10), 1871; https://doi.org/10.3390/en12101871 - 16 May 2019

Cited by 17 | Viewed by 3458

Abstract

The thermodynamic characterisation of magnetocaloric materials is an essential task when evaluating the performance of a cooling process based on the magnetocaloric effect and its application in a magnetic refrigeration cycle. Several methods for the characterisation of magnetocaloric materials and their thermodynamic properties are available in the literature. These can be generally divided into theoretical and experimental methods. The experimental methods can be further divided into direct and indirect methods. In this paper, a new procedure based on an artificial neural network to predict the thermodynamic properties of magnetocaloric materials is reported. The results show that the procedure provides highly accurate predictions of both the isothermal entropy and the adiabatic temperature change for two different groups of magnetocaloric materials that were used to validate the procedure. In comparison with the commonly used techniques, such as the mean field theory or the interpolation of experimental data, this procedure provides highly accurate, time-effective predictions with the input of a small amount of experimental data. Furthermore, this procedure opens up the possibility to speed up the characterisation of new magnetocaloric materials by reducing the time required for experiments. Full article

(This article belongs to the Special Issue Refrigeration Systems and Applications 2019)

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15 pages, 2409 KiB

Open AccessArticle

Analysis and Optimization of Exergy Flows inside a Transcritical CO₂ Ejector for Refrigeration, Air Conditioning and Heat Pump Cycles

by Sahar Taslimi Taleghani, Mikhail Sorin and Sébastien Poncet

Energies 2019, 12(9), 1686; https://doi.org/10.3390/en12091686 - 04 May 2019

Cited by 10 | Viewed by 3485

Abstract

In this study, the exergy analysis of a CO₂ (R744) two-phase ejector was performed using a 1D model for both single and double choking conditions. The impact of the back pressure on the exergy destruction and exergy efficiencies was presented to evaluate the exergy performance under different working conditions. The results of two exergy performance criteria (transiting exergy efficiency and Grassmann exergy efficiency) were compared for three modes of an ejector functioning: Double choking, single choking and at the critical point. The behavior of three thermodynamic metrics: Exergy produced, exergy consumed and exergy destruction were evaluated. An important result concerning the ejector’s design was the presence of a maximum value of transiting exergy efficiency around the critical point. The impact of the gas cooler and evaporator pressure variations on the different types of exergy, the irreversibilities and the ejector global performance were investigated for a transcritical CO₂ ejector system. It was also shown that the transiting exergy flow had an important effect on the exergy analysis of the system and the Grassmann exergy efficiency was not an appropriate criterion to evaluate a transcritical CO₂ ejector performance. Full article

(This article belongs to the Special Issue Refrigeration Systems and Applications 2019)

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16 pages, 3370 KiB

Open AccessArticle

Thermal and Energy Evaluation of a Domestic Refrigerator under the Influence of the Thermal Load

by Juan M. Belman-Flores, Diana Pardo-Cely, Miguel A. Gómez-Martínez, Iván Hernández-Pérez, David A. Rodríguez-Valderrama and Yonathan Heredia-Aricapa

Energies 2019, 12(3), 400; https://doi.org/10.3390/en12030400 - 27 Jan 2019

Cited by 17 | Viewed by 5456

Abstract

This study seeks to understand the thermal and energetic behavior of a domestic refrigerator more widely by experimentally evaluating the main effects of the thermal load (food) and the variation of the ambient temperature. To carry out the experiments, the thermal load was classified based on the results of a survey conducted on different consumers in the state of Guanajuato, Mexico. The thermal behavior of both compartments of the refrigerator, the total energy consumption, the power of the compressor in its first on-state, and the coefficient of performance, according to the classification of the thermal loads and the room temperature, were evaluated. Finally, it is verified that the thermal load and the room temperature have a significant influence on the energy performance of the refrigerator. Full article

(This article belongs to the Special Issue Refrigeration Systems and Applications 2019)

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