Local cooling of the human body using ventilated matress in hospitals

A series of experiments were conducted in order to examine the cooling of the human body in bed equipped with a ventilated mattress (VM). The experiments were performed in a climate chamber (4.65 m width x 5.3 m length x 2.6 m height) which was air-conditioned by mixing ventilation system. A thermal manikin lying in the bed with the VM was used to simulate a person. The surface temperature and heat loss of the thermal manikin were controlled to correspond to those of an average person in a state of thermal comfort. The local cooling effect of the VM was studied at room air temperatures of 23, 26 and 30 oC. The performance of the VM was tested when VM was operating at different air flow rates (1.5, 3, 4.5 and 6 L/s). The impact of body covering on the cooling effect from the VM was also studied. The performance of the cooling method was evaluated based on comparison of the segmental and whole body equivalent temperature (teq) with those determined at the reference temperature of 23 oC or when at the same room temperature with VM not in operation. The obtained results reveal that the body segments in contact with the VM were cooled, especially the back side and the back. The cooling effect increased with the increase of the airflow rate through the VM. These results suggest that in warm environment the VM may improve thermal comfort of people lying in bed. The use of the VM may lead to energy saving by operating the background ventilation system at elevated set point for the room temperature or by use of natural ventilation. However the non-uniform body cooling may cause local thermal discomfort. This needs to be further studied in human subject experiments.