Principal effective factors on the dynamic pull-down performance of a zeotropic mixture based ultra-low temperature freezer. (25th January 2021)

• Record Type: Journal Article
• Authors: Song, Yulong; Wang, Haidan; Cao, Feng
• Is Part Of: Applied thermal engineering. Volume 183: Part 1(2021)
• Publication Date: 2021-01-25
• Subjects: Ultra-low temperature freezer -- Two-stage cascade system -- Pull-down performance -- Mixture -- Dynamic features; Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2020.116070
• Languages: English
• ISSNs: 1359-4311

Abstract

Highlights: The dynamic parameters of operating stability and security during the pull-down process are clearly studied. The charging amount, zeotropic component fraction, and heat collector opening are selected as independent variables. The law of highest discharge temperatures of both subsystems are reported in detail. The basic principle of discharge temperature protection is proposed. Abstract: Cascade technology with less than −80 ℃ has risen sharply with the development of the biomedical industry. Although appropriate refrigerant-couples and corresponding improving-approaches have been presented, dynamic parameters of operating stability and security rather than COP are more important to evaluate an ultra-low temperature freezer. Refrigerant-couple R404A/R508A with pentane as oil carrier in the low stage is employed to be working fluids in this study, and the main dynamic parameters during the pull-down process are clearly discussed experimentally, especially the laws of highest discharge temperatures in both subsystems. Results demonstrate that the highest discharge temperature is generally appeared in the first half of the cooling-process, which should be the key-point of the discharge temperature protection. Additionally, the operating stability and security would be highly strengthened with decreasing charging amount, increasing zeotropic component fraction, and declining heat collector opening, however, corresponding negative effects will be definitely caused to a great extent.