Human response to the bed thermal environment generated by a ventilated mattress combined with local heating

Abstract

A ventilated mattress (VM) was designed to withdraw the polluted air of the bed micro-environment through an opening located near the feet, moving the air inside the mattress to where it was cleaned and could be discharged back to the room or ducted out of the room. Thermal manikin experiments indicated a risk of uncomfortable local cooling of user's feet. The design of the VM was therefore improved by incorporating local heating (LH). The response of 30 subjects to the bed thermal environment (BTE) generated by the improved design was studied while they lay awake on the VM at room temperatures: 19 °C, 23 °C and 28 °C. Based on the subjects' responses the flow rate through the VM and the LH were adjusted to provide acceptable whole body and local thermal sensation. The surface temperature of the mattress, the air temperature and relative humidity in the BTE and the temperature and flow rate of the air exhausted through the VM were measured. The results show that the VM if used alone may cause unacceptable local body cooling at 19 °C and 23 °C, so some LH was required. At 28 °C the VM improved subjects' thermal comfort. Continuous control of the VM and the LH improved the acceptability of the BTE and decreased the risk of local discomfort. The surface temperature of the mattress measured near the feet correlated well with occupant's thermal sensation and could be used to control the operation of the VM fan speed and the LH.