Computational model development for heat production of Al-CaO flameless ration heaters (FRHs): The effect of temperature, pressure, and pH on the exothermic characteristics. (March 2023)

• Record Type: Journal Article
• Authors: Liu, Chongxin; Si, Kai; Zielinska, Magdalena; Huang, Xinlei; Fang, Jiajia; Xiao, Hong-Wei; Zhang, Chunjiang
• Is Part Of: Food packaging and shelf life. Volume 35(2023)
• Publication Date: 2023-03
• Subjects: Self-heating packaging -- Flameless ration heaters -- Exothermic chemical reaction -- Energy conversion efficiency -- Exothermic characteristics -- Mathematical model; Food -- Packaging -- Periodicals; Food -- Preservation -- Periodicals; Food -- Packaging; Periodicals; 664.0905
• DOI: 10.1016/j.fpsl.2022.101011
• Languages: English
• ISSNs: 2214-2894

Abstract

Abstract: The principle of the Al-CaO flameless ration heaters (FRHs), as a kind of portable chemical energy device for self-heating food packaging, is to release a large amount of heat mainly through the complex chemical reactions of the mixture of aluminium powder, calcium oxide, and water for reheating food. The effect of temperature (20–130 °C), pressure (101.325–607.95 kPa), and pH (12.70–13.40) on the heat production of the thermogenic agent were investigated. A computational model for FRHs' actual heat production was established based on the internal stratification phenomenon and then verified with five ratios of Al to CaO (45:55, 50:50, 55:45, 60:40, 65:35). Results showed that temperatures greater than 120 °C would promote the increase in solids content and decrease in liquid water of the reaction products. It mainly caused the insufficient reaction response of the thermogenic agent in the inner layer of the heater. The increasing pH could vastly increase the reaction rate and shorten the response time. The pressure has no apparent effect on the chemical reaction of the mixture. The computation method proposed in this study enables stable and precise calculation of the actual heat production by Al-CaO FRHs. The results of this study provide a deep understanding and insight into Al-CaO FRHs and are helpful for designing and optimizing food self-heating units. Graphical Abstract: ga1 Highlights: Non-uniform temperature and pH of FRH during reaction results in the stratification. Al-to-CaO ratios affect the internal stratification numbers and the heat release of FRH. Microstructures of the thermogenic agent before reaction and after usage were characterized by SEM. Hydrogen production of each layer was used to explore the reaction degrees of FRH. The proposed model could provide more comprehensive information than the standard method.