IIAR Developing Safety Guidance For CO2 Refrigeration ALEXANDRIA, Va.-The International Institute of Ammonia Refrigeration (IIAR) says it is developing a standard for CO2 that will specify criteria ...for the safe design and operation of CO2 refrigeration systems such as cascade and transcritical. By leveraging the store's existing refrigeration system, the product stores "cooling" at night by freezing tanks of salt water when energy costs are low.
•A novel SA-CCR system with an integrated air-cooled compression cycle is proposed.•The SSAR subsystem is cascaded with the EDCR subsystem with one evaporator.•An ACR cycle is coupled with a CCR ...cycle to meet the all-weather cooling demand.•The efficiency and the time of solar energy utilization is improved and extended.•The energy saving performance of the proposed system is proven to be excellent.
Due to intermittent and uncertainty natures of solar energy, the conventional solar absorption-compression cascade refrigeration (SA-CCR) system cannot meet the all-weather cooling/heating demand when solar inputs are insufficient. In this work, a novel SA-CCR system with an integrated air-cooled vapor compression refrigeration (ACR) cycle is proposed. It is coupled of two subsystems: a solar-driven single-effect absorption refrigeration (SSAR) subsystem and an electricity-powered dual-source vapor compression refrigeration (EDCR) subsystem. The two subsystems are cascaded by one evaporative-condenser. The following improvements are achieved by the novel system: (i) the efficiency and the time of solar energy utilization are respectively improved and extended dramatically; (ii) the all-weather cooling/heating demand is met by coupling an ACR cycle to the EDCR subsystem. The proposed system is applied to a building located in Zhengzhou city to evaluate its cycle and economic performance. On a basis of different grade energy, i.e., thermal and mechanical energy, the novel SA-CCR system with an integrated air-cooled compression cycle is respectively compared with the conventional SSAR and ACR systems. The results show that the whole cooling season power (energy) consumption is reduced by 26.70% as compared to the conventional ACR system, and that the proposed system has the better economic performance than the two conventional SA-CCR systems.
The phase‐down scenario of conventional refrigerants used in gas–vapor compressors and the demand for environmentally friendly and efficient cooling make the search for alternative technologies more ...important than ever. Magnetic refrigeration utilizing the magnetocaloric effect of magnetic materials could be that alternative. However, there are still several challenges to be overcome before having devices that are competitive with those based on the conventional gas–vapor technology. In this paper a rigorous assessment of the most relevant examples of 14 different magnetocaloric material families is presented and those are compared in terms of their adiabatic temperature and isothermal entropy change under cycling in magnetic‐field changes of 1 and 2 T, criticality aspects, and the amount of heat that they can transfer per cycle. The work is based on magnetic, direct thermometric, and calorimetric measurements made under similar conditions and in the same devices. Such a wide‐ranging study has not been carried out before. This data sets the basis for more advanced modeling and machine learning approaches in the near future.
Magnetic refrigeration utilizing the magnetocaloric effect of magnetic materials is a promising alternative to conventional gas–vapor technology. In this paper a rigorous assessment of the most relevant magnetocaloric material families is presented and compared in terms of their adiabatic temperature and isothermal entropy change under cycling, criticality aspects, and the amount of heat that they can transfer per cycle.
•A review of stationary and mobile CO2 refrigeration and AC is provided.•Thermodynamic justification for architectures and modifications is discussed.•Numerical and experimental analyses are ...summarized.•Exceptions, alternative approaches, and progressive findings are included.•Paths to overcome current challenges to broader acceptance of CO2 refrigeration are identified.
Since its resurgence as a refrigerant in the 1990s, Carbon Dioxide (CO2) has grown in popularity and breadth of application. Its negligible global warming potential (GWP) eliminates the risk of being phased out due to legislation, and its non-toxicity, non-flammability, and low cost allows its use in many vapor compression cycle applications. However, the high critical pressure and low critical temperature require significantly more compressor power under moderate and high-ambient conditions and thus, necessitate the addition of cycle modifications to reach coefficient of performance (COP) values equal to or greater than those of other working fluids. This paper provides a review of research conducted on the use of CO2 vapor compression cycles in refrigeration and air conditioning (AC) cycles for both transportation and stationary refrigeration. A primary intention of writing this review is to offer evidence and justification for many common cycle modifications, then connect these modifications to a broad array of applications. Thus, advanced cycles in mobile and stationary applications are shown and the individual modifications present have their own independent justification to create a complete picture of the topic. The designs of complete systems, as well as specific components within the system, are included, as are the relations between the thermo-physical properties of CO2 and their benefits in these particular applications. Additionally, economic analyses of the feasibility of using CO2 in place of existing fluids are reviewed. Challenges facing the use of CO2 refrigeration cycles in stationary and transportation refrigeration are discussed, as are potential future advancements to overcome them.
•Using solar concentrating collectors in refrigeration is reviewed and discussed.•The focus is on solar-driven absorption and adsorption refrigeration cycles.•Compound parabolic, trough, dish, and ...linear Fresnel collectors are considered.•Parabolic trough collector is dominant, among concentrating collectors.•Absorption refrigeration has been reported much more than the adsorption.
Considering the operating temperatures, there is a reasonable match between solar concentrating collectors and some thermal-powered cooling technologies. Both current and previous studies demonstrate that concentrating solar collectors have had a significant impact on the development of solar absorption and adsorption refrigeration technologies. Therefore, studying of sorption refrigeration, integrated with solar concentrating collectors, could be an important issue. On this basis, this paper is undertaken to present a detailed review of solar refrigeration, with a specific focus on the absorption and adsorption cooling cycles, driven by solar concentrating collectors, aiming for providing a comprehensive guideline for the future studies in this field. This review article is divided into four main sections, each of which presents the methods, results, and analyses, relating to the studies in the field of cooling systems powered by concentrating collectors. These four main contents include parabolic trough, compound parabolic, dish, and linear Fresnel collectors for refrigeration purposes, either direct or indirect. The thermodynamic properties of the related refrigeration cycles are reviewed and analyzed. As a general conclusion, a solar sorption refrigeration could be competitive with the conventional coolers, if a suitable combination of working fluid, solar collector, and refrigeration subsystems would be selected. The present study could provide the possibility of an appropriate selecting of the solar cooling sub-systems for future studies. Finally, it is worth mentioning that there is more need for further research works on the solar-based absorption refrigeration cycles, to make them more economic and more efficient.
PDF
