查看更多>>摘要：Most COVID-19 vaccines require ambient temperature control for transportation and storage. Both Pfizer and Moderna vaccines are based on mRNA and lipid nanoparticles requiring low temperature storage. The Pfizer vaccine requires ultra-low temperature storage (between -80 degrees C and -60 degrees C), while the Moderna vaccine requires -30 degrees C storage. Pfizer has designed a reusable package for transportation and storage that can keep the vaccine at the target temperature for 10 days. However, the last stage of distribution is quite challenging, especially for rural or suburban areas, where local towns, pharmacy chains and hospitals may not have the infrastructure required to store the vaccine. Also, the need for a large amount of ultra-low temperature refrigeration equipment in a short time period creates tremendous pressure on the equipment suppliers. In addition, there is limited data available to address ancillary challenges of the distribution framework for both transportation and storage stages. As such, there is a need for a quick, effective, secure, and safe solution to mitigate the challenges faced by vaccine distribution logistics. The study proposes an effective, secure, and safe ultra-low temperature refrigeration solution to resolve the vaccine distribution last mile challenge. The approach is to utilize commercially available products, such as refrigeration container units, and retrofit them to meet the vaccine storage temperature requirement. Both experimental and simulation studies are conducted to evaluate the technical merits of this solution with the ability to control temperature at -30 degrees C or -70 degrees C as part of the last mile supply chain for vaccine candidates.
查看更多>>摘要：In the supermarket refrigeration industry, the natural refrigerant R744 (CO2) has been designated as a long-term solution to mitigate HFC refrigerants' global warming. In this study, booster (BB) and parallel compression (BP) configurations were assessed through a detailed and novel energetic modelling, which includes a semi-empirical "four-parameter" for reciprocating and scroll compressor models and a one-zone model for the gas cooler, and a three zones model for the condenser. Model validation showed a mean deviation of 4.23% against reference values. The COP of the BP configuration was 14% higher than BB, for ambient temperatures between 0 degrees C and 35 degrees C. This study presents for the first time, the simulation of transcritical systems with R744 throughout out different locations in Chile. Simulation results of fourteen Chilean cities showed that the BP system allows reducing the annual energy consumption between 4% for very cold climates and 12% for desert regions. An economic analysis revealed that only in most desert and warm climates (Arica, Antofagasta and Santiago), the differential capital expenditures of the BP system over the BB were recovered within 20 years with the operational expenditure savings. For the rest of the evaluated cities, the BB system is a more profitable solution than BP. The study aims to support the introduction of refrigeration system with R744 in Chilean supermarkets.
Abd-Elhady, Mahmoud M.Salem, Mohamed S.Hamed, Ahmed M.El-Sharkawy, Ibrahim I....
16页
查看更多>>摘要：Desiccant dehumidification systems are thermally regenerated systems that can be used either as standalone or as complementary additives for conventional cooling systems. One of their best competitive qualities is the potential to utilize low-grade heat sources for the regeneration process, thus decreasing electrical power consumption and scaling back the emissions of greenhouse gasses. However, up till now, desiccant dehumidification systems saw limited practical applications, due to their relatively high capital costs and low efficiency. To enhance the commercial competitiveness of desiccant dehumidification systems and expand their fairly tiny niche market, it was necessary to improve the system's performance and reliability and reduce their costs. A detailed discussion of the current designs configurations and the main differences between them may help future researchers to come up with novel, innovative designs, to overcome the system's drawbacks and make them actual viable alternative competitors in the dehumidification market. Consequently, this paper presents and analyzes the development of those configurations in the following three main aspects: packed bed, fluidized bed, and rotating desiccant wheel.
NSTL
Elsevier