A Physiological Evaluation of Air Microclimate Cooling System's Performance

Air microclimate cooling is an effective approach for alleviating heat stress of pilots. The inlet temperature and flow rate of air cooling systems are two pivotal parameters, which not only determine cooling capacity and cooling efficiency, but also affect body's physiological responses and thermal comfort. Objective of the study is to evaluate the tradeoff between inlet temperature and flow rate. Four healthy young mate volunteers participated in heat exposure experiments in 45 degrees C, 40% relative humid chamber for 90 min with air microclimate cooling system. Inlet air temperatures were 10, 15, 20 degrees C, flow rates were 200, 250, 300L/min, respectively. The results indicated that sweat production, sweat evaporation, mean skin temperature, heat storage and subjective rating basically correlate positively with inlet temperature and negatively with flow rate. Sweat evaporation efficiency, change of rectal temperature and heart rate were not significantly affected by inlet temperature and flow rate. In addition, cooling capacity correlated positively with flow rate but negatively with temperature. While cooling efficiency correlated negatively with flow rate and didn't significantly correlate with inlet temperature. It was concluded that lower temperature was superior to higher flow rate under the condition of the same cooling efficacy obtained.