The effect of adjustable cooling jet on thermal comfort and perception in warm office environment – a laboratory study

The aim was to study how the cooling jet from the ceiling, with individual control over the airflow, is perceived and how it affects the thermal comfort in warm office environment. 32 undergraduate university students participated in the experiment. Two thermal conditions were tested: (1) no cooling jet and (2) adjustable cooling jet from the ceiling. Subjects were able to use a controller with seven different settings to adjust the airflow coming from the nozzles so that the target velocity varied from 0.3 m/s to 1.5 m/s. The cooling jet was directed into the upper body.
The whole experimental session lasted for 110 minutes including acclimatization (30 minutes) and both thermal conditions (40 minutes each). The order of thermal conditions was counterbalanced between participants. Clothing insulation and activity level were controlled. Subjects’ work performance was measured with two different tasks: short term memory task and working memory task. Whole body thermal comfort, local thermal comfort, symptoms and subjects perception were assessed with questionnaires.
Most of the subjects adjusted the airflow of the cooling jet. 65% of the subjects adjusted the jet so that at the end of session the target velocity was 1.1-1.3 m/s. Adjustable cooling jet improved thermal comfort, perceived indoor air quality and perception of the work environment. It also reduced symptoms, perceived fatigue, tiredness and subjective workload. Thermal environment with the adjustable cooling jet was perceived to be better for working efficiently for a long time. Condition did not affect work performance.