Spatiotemporal characteristics of indoor thermal and oxygen environments under combined thermal-oxygen supply in high-altitude buildings

The Qinghai-Xizang Plateau is characterized by a cold, severely hypoxic climate that threatens human health. While most studies focus on thermal-oxygen jets, the whole-room thermal-oxygen environment remains underexplored. This study investigates the distribution of combined thermal-oxygen airflow in high-altitude indoor environments. Key factors affecting convective thermal-oxygen supply were identified based on heat and oxygen balance principles. Experimentally validated CFD simulations were used to examine the spatiotemporal characteristics of indoor thermal-oxygen flow fields under different conditions. Results indicate distinct dynamic responses and distribution of temperature and oxygen concentration. The room-averaged temperature reached a steady state at approximately 1200 s, whereas oxygen concentration typically stabilized at around 4500 s. A higher supply air rate shortened oxygen stabilization, whereas a higher oxygen supply concentration prolonged it. Field uniformity was characterized using the Contribution Ratio of Indoor Heat Sources (CRIHS) and the Contribution Ratio of Indoor Oxygen Concentration (CRIOC). CRIHS varied with height, indicating significant thermal stratification. Higher supply air temperatures intensified stratification, whereas a moderate air-supply mode and higher supply air rates improved thermal uniformity. CRIOC remained close to 1 vertically, indicating a relatively uniform oxygen concentration field. This study provides guidance for regulating indoor convective thermal-oxygen combined supply in high-altitude regions.