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Title of the thesis: Thermal Comfort of Older Adults in Hot Environments: Experimental and Numerical Investigation of Local Cooling Devices

Thesis defender: Minzhou Chen
Opponent: Prof. Dolaana Khovalyg, EPFL, Switzerland
Custos: Prof. Risto Kosonen,Aalto University School of Engineering

The doctoral thesis by Minzhou Chen titled Thermal comfort of older adults in hot environments: experimental and numerical investigation of local cooling devices addresses the growing challenge of protecting older adults from heat-related risks during hot weather. Older adults, as a vulnerable population, are more susceptible to heat-related mortality, especially in regions like Finland where climate change is increasing the occurrence of high indoor temperatures. With limited use of cooling systems and declining income levels, many older adults face uncomfortable and potentially unsafe indoor climates during heatwaves.

This research investigates the effectiveness of three types of local cooling devices—personal fans, ventilated jackets, and evaporative cooling—in enhancing thermal comfort and reducing energy consumption. Through a combination of controlled climate chamber experiments and numerical simulations, the study examined: (1) how these devices improve thermal comfort under different environmental conditions; (2) changes in thermal responses when older adults use local cooling; (3) the physiological and psychological factors affecting comfort sensation; and (4) energy-saving potential when combining local cooling with reduced space cooling.

The results of the study showed that the neutral temperature of the elderly from northern Europe was 26 °C, their preferred temperature was 26.5 °C and the upper limit of the acceptable temperature was 28 °C. The lowest thermal acceptance rate was observed in environments with high temperature and relative humidity. At 28 °C (60%) and 29 °C (40%), the use of a table fan, evaporative cooling device, or air-cooled jacket could reduce the elderly's thermal sensation to neutral and make more than 80% of people accept the thermal condition. At 33 °C (40%) and 32 °C (50%), the use of an evaporative cooling device or air-cooled jacket reduced thermal sensation significantly, but not to a neutral state. A combination of an evaporative cooling chair and a ventilated jacket can make older adults' thermal sensation reached to 0.5 in room at 33 °C. Meanwhile, it led to a notable 19 % reduction in electric energy consumption while maintaining similar elderly thermal sensation.

The findings provide new insights into low-energy, targeted cooling strategies that can protect vulnerable populations during heat waves. This thesis contributes to the development of sustainable and accessible cooling solutions for aging societies.

Thesis available for public display 7 days prior to the defence at . 

Contact information: 
E-Mail: minzhou.chen@aalto.fi