| 1. |
- Liu, Zhan, et al.
(författare)
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An ultralow-temperature cascade refrigeration unit with natural refrigerant pair R290-R170 : Performance evaluation under different ambient and freezing temperatures
- 2023
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Ingår i: Thermal Science and Engineering Progress. - 2451-9049. ; 46
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Tidskriftsartikel (refereegranskat)abstract
- The global demand for ultralow-temperature (ULT) refrigeration units gets greatly promoted, for storage, transportation, and distribution of COVID-19 vaccines. In this work, a ULT freezer is developed with a cascade refrigeration system (CRS) utilizing environmentally friendly refrigerants R290 and R170. The performance of the ULT freezer is experimentally evaluated under different ambient temperatures Tamb and freezing temperatures Tfreezing. The result shows that once the refrigeration system starts, the freezer enters a pull-down period and then reaches stable or periodic on-off operation. The monitored temperatures present drastic variations in the low-temperature cycle (LTC) and show a relatively stable start-up process in the high-temperature cycle (HTC). The monitored temperature rises when Tamb increases from 16 °C to 32 °C. The increasing Tamb brings about a larger temperature drop crossing the pre-cooled condenser, cascade heat exchanger, and high-temperature condenser, and a smaller temperature reduction through the anti-condensation. As Tfreezing decreases from −60 °C to −86 °C, the suction/discharge gas temperatures increase in the low-temperature compressor, while the other monitored temperatures reduce. The largest temperature non-uniformity in the freezer is 9.19 °C, and the lowest wall temperature can reach −90.52 °C. With Tamb ranging from 16 °C to 32 °C, the power consumption of the freezer increases from 896 W to 912 W. When Tfreezing varies from −60 °C to −86 °C, the CRS's consumed power reduces from 804 W to 904 W. The present freezer can easily obtain low temperatures e.g., −81 °C, and reach a lower temperature, such as −86 °C with proper improvements to reduce cold loss.
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| 2. |
- Liu, Zhan, et al.
(författare)
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Experimental study on a -86 °C cascade refrigeration unit with environmental-friendly refrigerants R290-R170
- 2023
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Ingår i: Environmental Science and Pollution Research. - 0944-1344. ; 30:43, s. 97339-97352
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Tidskriftsartikel (refereegranskat)abstract
- Ultralow-temperature refrigeration faces significant issues linked to the security of the cold chain for the production, storage, transportation, and distribution of COVID-19 vaccines. The use of environmentally friendly refrigerants in cascade refrigeration systems (CRS) to provide low-temperature range is motivated by the high demand for ultralow-temperature refrigeration units. In the current study, a CRS is built to generate a low temperature of -86 °C for the storage of COVID-19 vaccines. In the CRS, the natural refrigerant combination R290-R170 is used as high-temperature and low-temperature fluids. The pull-down performance of the -86 °C freezer is explored experimentally, and the stable operating performance is determined at two different dry bulb and wet bulb temperatures. Various status monitors are set up to analyze the CRS's operation features, and several temperature monitors are put in the freezer to analyze temperature variations. The power consumption of the CRS is examined and evaluated. Finally, several key findings are summarized. The current work is the first to involve experimental measurements on -86 °C temperature generated by a CRS, which can substantially enhance experiment data in ultralow-temperature refrigeration and contribute to a more in-depth understanding of the operation performance of a -86 °C ultralow-temperature freezer.
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| 3. |
- Liu, Zhan, et al.
(författare)
-
Experimental test on the performance of a −80 °C cascade refrigeration unit using refrigerants R290-R170 for COVID-19 vaccines storage
- 2023
-
Ingår i: Journal of Building Engineering. - : Elsevier BV. - 2352-7102. ; 63
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Tidskriftsartikel (refereegranskat)abstract
- With the urgent demand for ultralow-temperature refrigerators worldwide, the operation reliability and stability of the refrigeration system becomes greatly crucial. In this study, a -80 oC ultralow-temperature cascade refrigeration system (CRS) is developed. From aspects of global warming potential (GWP) and ozone depletion potential (ODP), the environmentally friendly refrigerants R290 and R170 are utilized in the high-temperature cycle and low-temperature cycle of CRS. The experimental measurement is conducted in a Type-laboratory with a dry bulb temperature of 25.0 °C and a wet bulb temperature of 20.2 °C. The pull-down and stable operation performance of the CRS freezer are experimentally investigated. Both the inlet and outlet temperature and pressure of two compressors are monitored, and the operation characteristic of the CRS is analyzed. With some temperature test points arranged in the freezer, the temperature drop and temperature fluctuation variation of air are assessed. The operation power consumption of the CRS is also measured during the whole process. It shows that the −80 °C temperature can be generated and realized by the developed ultralow-temperature freezer.
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| 4. |
- Tan, Haihui, et al.
(författare)
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Experimental study on the pull-down performance of a −80°C cascade refrigeration freezer
- 2023
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Ingår i: Asia-Pacific Journal of Chemical Engineering. - : Wiley. - 1932-2135 .- 1932-2143. ; 18:3
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Tidskriftsartikel (refereegranskat)abstract
- To cope with global climate change, chlorofluorocarbons and hydrofluorocarbons refrigerants have been or will be abandoned by different countries worldwide. Natural refrigerants seem to be promising substitutes in the near future. In this study, eco-friendly refrigerants R290 and R170 are adopted as high-temperature and low-temperature fluid in a cascade refrigeration freezer to generate −80°C. The experimental measurements are carried out to investigate the pull-down performance of the freezer. The inlet and outlet pressure of two compressors are monitored and tested. Temperatures of different state monitors in high-temperature cycle and low-temperature cycle are measured to analysis the operation performance of the cascade refrigeration system. Different temperature test points are set to research the temperature drop and temperature distribution in the freezer. Some new findings are obtained. Due to the lack of ultralow temperature experimental data on cascade refrigeration system, this study can enrich and deepen the understanding on operation mechanism of ultralow temperature cascade refrigeration freezer.
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| 5. |
- Tan, Haihui, et al.
(författare)
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Operation performance of an ultralow-temperature cascade refrigeration freezer with environmentally friendly refrigerants R290-R170
- 2023
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Ingår i: Environmental Science and Pollution Research. - : Springer Science and Business Media LLC. - 0944-1344 .- 1614-7499. ; 30:11, s. 29790-29806
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, the operation performance of an ultralow-temperature cascade refrigeration freezer is experimentally researched. The natural refrigerants R290-R170 are adopted as high-temperature and low-temperature fluids. The experimental test is conducted in a type laboratory with a dry bulb temperature of 32.0 °C and a wet bulb temperature of 26.5 °C. Different state monitors are set to display the system operation performance, and several temperature monitors are arranged to study the pull-down performance and temperature variations in the freezer. Based on the established experimental rig, three freezing temperatures, including − 40 °C, − 80 °C, and − 86 °C, are measured and compared. The results show that it takes about 240 min for the freezer to be pulled down to − 80 °C. During the pull-down period, different monitors all experience rapid temperature drop, and the power consumption reduces from 1461.4 W to 997.5 W. Once the target temperature is achieved, the freezer comes into periodic start–stop operation. With the set temperature ranging from – 40 °C to – 86 °C, the inlet temperature of two compressors gradually decreases, while the discharge temperature has an increase trend. The cooling effect of the pre-cooled condenser reduces with the freezing temperature, while the long connection pipe has opposite variation profile. Moreover, it is observed that for different freezing temperatures, most of the space in the freezer can be cooled down to the target temperature. It is confirmed that the present ultralow-temperature freezer can be used for the storage and transportation of COVID-19 vaccines. However, it is also found that the cascade refrigeration system is not suitable for high freezing temperature, due to high power consumption and extensive start–stop switch of refrigeration system.
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