Current Status on Natural Working Fluids in Cooling, Heating and Power Systems

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Energy Science and Technology".

Deadline for manuscript submissions: closed (20 January 2022) | Viewed by 15217

Special Issue Editors


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Guest Editor
Department of Mechanical and Electrical Engineering, University of Southern Denmark (SDU), 6400 Sønderborg, Denmark
Interests: eco-friendly cooling and heating technologies; two-phase ejectors; exergy; renewable energy technologies; natural working fluids; CCHP systems

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Guest Editor
Department of Mechanical Engineering, Technical University of Denmark (DTU), Lyngby, Denmark
Interests: optimization and dynamic modeling; waste heat recovery units; organic rankine cycles; control strategies; renewable energy technologies; pumped thermal energy storage; power generation

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Guest Editor
Department of Mechanical Engineering, Université de Sherbrooke, Sherbrooke, QC J1K 2R1, Canada
Interests: energy efficiency; computational fluid dynamics; exergy analysis; thermodynamic cycles; heat transfer fluids; refrigeration system; supersonic ejectors; vortex tubes
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Special Issue Information

Dear Colleagues,

Cooling, heating and power systems are of vital importance for mankind, being essential for most of the activities of modern society. However, these systems also contribute dramatically to climate change. Therefore, the adoption of eco-friendlier cooling, heating and power solutions is mandatory in order to mitigate the contemporary environmental challenges and to respect the different regulations on the progressive ban of hydrofluorocarbons. Indeed, natural working fluids, such as hydrocarbons, carbon dioxide, water, ammonia and air, with negligible/zero global warming potential and zero ozone depletion potential are bound to play a key role in this context.

The purpose of this Special Issue is to attract state-of-the-art research and review articles on the use of natural working fluids in cooling, heating and power systems. Topics of interest include, but are not limited to, the following:

  • System and component modeling;
  • CFD analyses;
  • Experimental investigations;
  • Exergy-based assessments;
  • Life cycle climate performance and life cycle assessment;
  • District heating and cooling;
  • Heat-driven systems;
  • Vapor-compression HVAC&R systems;
  • Reverse Joule/Brayton cycles;
  • Organic Rankine and Kalina cycles;
  • Supercritical CO2 power cycles;
  • Polygeneration systems;
  • Expanders, jet pumps and ejectors;
  • Vortex tubes;
  • Pumped thermal energy storage;
  • Natural-working-fluid-based mixtures;
  • Safety issues and risk assessment for flammable refrigerants.

Dr. Paride Gullo
Mr. Roberto Pili
Prof. Dr. Sébastien Poncet
Guest Editors

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Published Papers (6 papers)

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Research

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16 pages, 11674 KiB  
Article
An Ultra-Low Temperature Transcritical R744 Refrigeration System for Future Detectors at CERN LHC
by Pierre Barroca, Armin Hafner, Bart Verlaat, Paolo Petagna, Wojciech Hulek, Lukasz Zwalinski, Pierre Hanf, Michele Battistin, Loic Davoine and Daniella Teixeira
Appl. Sci. 2021, 11(16), 7399; https://doi.org/10.3390/app11167399 - 11 Aug 2021
Cited by 1 | Viewed by 2987
Abstract
The cooling systems of the future tracking detectors of the ATLAS and CMS experiments at the Large Hadron Collider (LHC) at CERN will be entirely based on CO2 refrigeration technology. The system is a booster refrigeration system, composed of a two stage [...] Read more.
The cooling systems of the future tracking detectors of the ATLAS and CMS experiments at the Large Hadron Collider (LHC) at CERN will be entirely based on CO2 refrigeration technology. The system is a booster refrigeration system, composed of a two stage primary part with transcritical R744 equipment and a low temperature secondary CO2 pumped loop. The primary refrigeration sub-system installed on surface provides cold R744 at 53C to the CO2 pumped loops installed 100 m underground and rejects the heat exchanged. The process must be reliable and remain stable regardless of the amount of heat exchanged, which will amount to hundreds of kilowatts and is expected to vary throughout the lifetime of the detectors. The paper discusses the concept adopted for the innovative transcritical R744 cycle and describes the technical details of the first prototype built. Full article
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15 pages, 5429 KiB  
Article
Experimental Thermodynamic Investigation on the Refrigerant Charge in a Transcritical CO2 Electric Bus Air Conditioning System
by Haidan Wang, Shengbo Li, Yulong Song, Xiang Yin, Feng Cao and Paride Gullo
Appl. Sci. 2021, 11(12), 5614; https://doi.org/10.3390/app11125614 - 17 Jun 2021
Cited by 4 | Viewed by 1661
Abstract
Due to its considerable impact on climate, bus air conditioning systems are being pushed to take a new and sustainable path. Electric buses relying on transcritical CO2 air conditioning units are perceived to be eco-friendly and future-proof solutions to achieving such a [...] Read more.
Due to its considerable impact on climate, bus air conditioning systems are being pushed to take a new and sustainable path. Electric buses relying on transcritical CO2 air conditioning units are perceived to be eco-friendly and future-proof solutions to achieving such a target. However, in order to have highly efficient air conditioning systems, the CO2 charge needs to be optimized. In this paper the energy and exergy-based analyses were performed to investigate the effect of normalized refrigerant charge on the system performance by using a test rig of a transcritical CO2 air conditioning unit for an 8 m electric bus. Results showed that the normalized refrigerant charge range of 0.248~0.336 was recommended in order to ensure the maximum coefficient of performance (COP). In addition, in sufficient charge conditions, the optimal COP, cooling capacity and exergy efficiency were 1.716, 18.97 kW and 29.79%, respectively, under the standard refrigeration condition of 35 °C/27 °C. As the ambient temperature rose from 35 °C to 40 °C, the COP, cooling capacity and exergy efficiency decreased by 16.03%, 10.90% and 12.22%, respectively. Furthermore, the exergy efficiency was found not to be sensitive to slightly insufficient charge, whereas overcharge was observed to be even beneficial to exergy efficiency under the condition of ensuring the maximum COP. In addition, insufficient refrigerant charging seriously affected the irreversible losses in the indoor and outdoor heat exchangers, whereas slight overcharge had little effect on the component exergy efficiency. Finally, the need to improve the CO2 compressor efficiency to enhance the system performance was revealed. Full article
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13 pages, 3639 KiB  
Article
Coupling Effect of Air Flow Rate and Operating Conditions on the Performance of Electric Vehicle R744 Air Conditioning System
by Anci Wang, Jianmin Fang, Xiang Yin, Yulong Song, Feng Cao and Paride Gullo
Appl. Sci. 2021, 11(11), 4855; https://doi.org/10.3390/app11114855 - 25 May 2021
Cited by 1 | Viewed by 1705
Abstract
The air flow rate on the gas cooler side is one of the key parameters affecting the performance and running safety of transcritical CO2 electric vehicle air conditioning systems. After experimentally analyzing the effects of the air volume flow rate in the [...] Read more.
The air flow rate on the gas cooler side is one of the key parameters affecting the performance and running safety of transcritical CO2 electric vehicle air conditioning systems. After experimentally analyzing the effects of the air volume flow rate in the gas cooler on the cycle parameters and system performance, a novel method to evaluate the optimal air flow rate was proposed. In addition, the effect of the gas cooler air volume flow rate on the key performance parameters of the system (e.g., optimal discharge pressure) was explored. Finally, the coupling effects of the compressor speed, ambient temperature and optimal air flow rate on the system performance was also exhaustively assessed. It was found that as the discharge temperature, the CO2 temperature at the gas cooler outlet and the discharge pressure did not vary more than ±2%, the corresponding gas cooler air volume flow rate was optimal. For the single-row and dual-process microchannel evaporator used in this work, the recommended value of the optimal gas cooler air volume flow rate was 2500 m3·h−1. The results could provide reference for the fan speed design of electric vehicle CO2 air conditioning systems, especially for the performance under idling model. Full article
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21 pages, 3789 KiB  
Article
Parametric Analysis of a Polygeneration System with CO2 Working Fluid
by Evangelos Bellos and Christos Tzivanidis
Appl. Sci. 2021, 11(7), 3215; https://doi.org/10.3390/app11073215 - 03 Apr 2021
Cited by 9 | Viewed by 1555
Abstract
The objective of the present work is the investigation of a novel polygeneration system for power, refrigeration and heating production at two temperature levels. The present system uses CO2 as the working fluid, which is an environmentally friendly fluid. The total configuration [...] Read more.
The objective of the present work is the investigation of a novel polygeneration system for power, refrigeration and heating production at two temperature levels. The present system uses CO2 as the working fluid, which is an environmentally friendly fluid. The total configuration is a combination of a transcritical refrigeration cycle coupled to a Brayton cycle with recompression, which is fed by a biomass boiler. The examined system, at nominal operating conditions, produces refrigeration at 5 °C, and heating at 45 °C and 80 °C. Additionally, the system can be converted into a trigeneration system where the two heating outputs are produced at the same temperature level. The system was studied parametrically by changing the following seven critical parameters: turbine inlet temperature, high pressure, medium pressure, heat exchanger effectiveness, refrigeration temperature, heat rejection temperature and high heating temperature. In nominal operating conditions, the system energy and exergy efficiencies were 78.07% and 26.29%, respectively. For a heat input of 100 kW, the net power production was 24.50 kW, the refrigeration production was 30.73 kW, while the low and high heating production was 9.24 kW and 13.60 kW, respectively. The analysis was conducted with a developed model in Engineering Equation Solver. Full article
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12 pages, 2590 KiB  
Article
Application of Plant Oils as Ecologically Friendly Hydraulic Fluids
by Artur Olszak, Karol Osowski, Ireneusz Musiałek, Elżbieta Rogoś, Andrzej Kęsy and Zbigniew Kęsy
Appl. Sci. 2020, 10(24), 9086; https://doi.org/10.3390/app10249086 - 18 Dec 2020
Cited by 4 | Viewed by 1900
Abstract
This paper presents the results of physicochemical and tribological tests of vegetable oils obtained by the supercritical fluid extraction method from berry seeds. The research was conducted by using these oils as the raw material for the biodegradable hydraulic working fluids. The oils [...] Read more.
This paper presents the results of physicochemical and tribological tests of vegetable oils obtained by the supercritical fluid extraction method from berry seeds. The research was conducted by using these oils as the raw material for the biodegradable hydraulic working fluids. The oils were assessed in terms of kinematic viscosity, anti-wear properties, resistance to oxidation and corrosive effects to copper and the pour point. The best results were achieved in the case of the blackcurrant seed oil. In order to confirm the practical possibility of using vegetable oils as working fluids for hydraulic couplings, experimental tests of the hydrodynamic clutch filled with blackcurrant seed oil were carried out. Based on the obtained research results, it was found that oils from berry plant seeds produced by supercritical extraction could be used in the future as potential working fluids for hydraulic systems. Full article
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Review

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25 pages, 8956 KiB  
Review
Identification of Existing Challenges and Future Trends for the Utilization of Ammonia-Water Absorption–Compression Heat Pumps at High Temperature Operation
by Marcel Ulrich Ahrens, Maximilian Loth, Ignat Tolstorebrov, Armin Hafner, Stephan Kabelac, Ruzhu Wang and Trygve Magne Eikevik
Appl. Sci. 2021, 11(10), 4635; https://doi.org/10.3390/app11104635 - 19 May 2021
Cited by 6 | Viewed by 4028
Abstract
Decarbonization of the industrial sector is one of the most important keys to reducing global warming. Energy demands and associated emissions in the industrial sector are continuously increasing. The utilization of high temperature heat pumps (HTHPs) operating with natural fluids presents an environmentally [...] Read more.
Decarbonization of the industrial sector is one of the most important keys to reducing global warming. Energy demands and associated emissions in the industrial sector are continuously increasing. The utilization of high temperature heat pumps (HTHPs) operating with natural fluids presents an environmentally friendly solution with great potential to increase energy efficiency and reduce emissions in industrial processes. Ammonia-water absorption–compression heat pumps (ACHPs) combine the technologies of an absorption and vapor compression heat pump using a zeotropic mixture of ammonia and water as working fluid. The given characteristics, such as the ability to achieve high sink temperatures with comparably large temperature lifts and high coefficient of performance (COP) make the ACHP interesting for utilization in various industrial high temperature applications. This work reviews the state of technology and identifies existing challenges based on conducted experimental investigations. In this context, 23 references with capacities ranging from 1.4 kW to 4500 kW are evaluated, achieving sink outlet temperatures from 45 °C to 115 °C and COPs from 1.4 to 11.3. Existing challenges are identified for the compressor concerning discharge temperature and lubrication, for the absorber and desorber design for operation and liquid–vapor mixing and distribution and the choice of solution pump. Recent developments and promising solutions are then highlighted and presented in a comprehensive overview. Finally, future trends for further studies are discussed. The purpose of this study is to serve as a starting point for further research by connecting theoretical approaches, possible solutions and experimental results as a resource for further developments of ammonia-water ACHP systems at high temperature operation. Full article
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