Built Environment and Thermal Comfort in a Low-Energy Dormitory: Field Assessment of Evaporative Cooling Performance in Beijing’s Transitional Climate

This study presents a multi-method, high-fidelity investigation into the thermal comfort performance of a window-type direct evaporative cooling (December) air-conditioning system installed in a student dormitory (Room 210, Building No. 1) at a university in Beijing. Conducted over a representative summer period (June 2025), the research integrates in situ physical measurements, standardized subjective questionnaire surveys (n = 198), and advanced computational thermal physiology modeling using ISO 7730–2021 and ASHRAE Standard 55–2023 frameworks. Environmental parameters—including dry-bulb temperature (t_a), relative humidity (RH), air velocity (v_a), and mean radiant temperature (t_r)—were monitored at eight spatially distributed points for 3 hours (12:00–15:00) with 1-minute resolution. Concurrently, clothing ensemble, activity level, and subjective thermal sensation votes (TSV) were collected via validated questionnaires aligned with ISO 10551 and ANSI/ASHRAE Standard 55 Annex B. The measured data served as input to a custom FORTRAN-based simulation platform implementing Fanger’s two-node thermoregulatory model, enabling deterministic calculation of the Predicted Mean Vote (PMV), Predicted Percentage Dissatisfied (PPD), Effective Temperature (ET*), and Standard Effective Temperature (SET*). Results demonstrate that the December unit achieved a stable outlet temperature depression of Δt = 8.48°C (inlet: 31.46°C; outlet: 22.98°C) with a wet-bulb efficiency of 59.6%, reducing indoor ta from ambient 31.5°C to a mean of 27.68°C while maintaining RH at 41.68%—a critical achievement given Beijing’s low summer humidity. The paper concludes with evidence-based design recommendations for December deployment in Northern Chinese educational buildings, emphasizing its energy-saving potential (32% lower electricity use), health advantages (no refrigerants, zero ozone depletion potential), and critical operational constraints (performance degradation above 65% RH). It provides a granular, academically rigorous critique of methodological, climatic, behavioral, and physiological limitations, establishing a definitive roadmap for future research.