A numerical method for cooling and dehumidifying process of air flowing through a deeply buried underground tunnel with unsaturated condensation model. (August 2019)

• Record Type: Journal Article
• Authors: Gao, Xiangkui; Qu, Yongtong; Xiao, Yimin
• Is Part Of: Applied thermal engineering. Volume 159(2019)
• Publication Date: 2019-08
• Subjects: Earth air tunnel -- Geothermal energy -- Numerical method -- Field test -- Heat and moisture transfer; Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2019.113891
• Languages: English
• ISSNs: 1359-4311

Abstract

Highlights: An advanced model for calculating air flowing through deeply buried tunnel is proposed. The new model can calculate the three-step cooling and dehumidifying process of air. The formula of minimum relative humidity of condensation is fitted. The new model greatly improves the accuracy of results during the condensation stage. Abstract: Earth-air tunnel heat exchanger (EATHE) system is a potential passive cooling/heating air conditioning technology to pre-treat the ventilation air. Predicting the heat and mass transfer is critically important to ensure sufficient ventilation for occupational safety, while the existing method calculates it without the unsaturated condensation process. In this paper, the description failure of dehumidifying process of unsaturated air is attempted by proposing an advanced model for a deeply buried underground tunnel. Based on the experimental results, the minimum relative humidity of condensation was fitted with air flow rate, equivalent radius of tunnel, inner wall temperature, air temperature and relative humidity. Then, the advanced model was validated with the measured data and good agreement was achieved. Finally, comparisons between new model and existing model were conducted. The results show that the advanced model can calculate the unsaturated condensation process. Besides, the new model has higher calculation accuracy. Specifically, the relative error of temperature and relative humidity of condensation period is reduced by 50% when compared to the existing model.