Micro-environmental control for efficient local cooling: Results from manikin and human participant tests

The micro-environment in this study refers to the air space and environment around a person that directly impacts their thermal sensation. This study aims at evaluating the performance of a newly developed microenvironmental control system (mu X) designed to cool the occupants locally for thermal comfort when the temperature in the ambient unoccupied space is raised from 23.9 degrees C to 26.1 degrees C in summer to reduce the HVAC cooling load. The mu X was tested first with a 20-segment thermal manikin wearing summer clothing in a full-scale stainless-steel chamber and then with human participants in a climate chamber. Results show that the heat loss by the manikin increased with the distance between the mu X air supply diffuser and the manikin and decreased with the clothing insulation. Changing the air delivery angle from 0 degrees to 10 degrees from the horizontal direction resulted in additional heat loss from the manikin. The heat loss from the manikin was found to be positively correlated with the supply air flow rate, but negatively correlated with the supply air temperature. However, the overall cooling efficiency dramatically increased with the supply air temperature. Overall, both the manikin test and the human participant test showed that the mu X was able to cool the occupant in a room of expanded temperature set-point, and the Clothing Independent Thermal Comfort Model gave a consistent prediction with the human participant test. However, slight thermal discomfort was reported when the mu X was used due to the effect of clothing, season, metabolic rate and local draught.