Browsing by Author "Chen, Minzhou"

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The effect of local thermal sensation on overall thermal sensation in older people under warm conditions: a chamber room study
(2022-08-31) Chen, Minzhou; Velashjerdi Farahani, Azin; Kosonen, Risto; Kilpeläinen, Simo; Lestinen, Sami
A4 Artikkeli konferenssijulkaisussa
Global aging and climate warming have made scholars begin to pay attention to the thermal comfort of the elderly. The deterioration of the function of body organs and systems caused by aging affects the thermoregulatory system of the elderly, resulting in a narrowing of their thermoregulatory range. To ensure their thermal comfort, personalised thermal comfort systems can be used, for example. When designing a system or selecting equipment, the impact of local thermal sensation on the overall thermal sensation needs to be considered. Most of the existing studies are based on young people, however, the local thermal sensation of the elderly may not be consistent with that of the young. This study recruited 26 Finnish older adults to conduct a series of human thermal comfort experiments under warm conditions in a climate chamber. The local and overall thermal sensations of the elderly were analyzed, and the weights of the influence of different parts on the overall thermal sensation of the elderly were obtained. The study found that the head and torso had a greater impact on the overall thermal sensation in a warm environment.
Enhancing thermal comfort of older adults during extreme weather : Combined personal comfort system and ventilated vest
(2024-09-01) Younes, Jaafar; Chen, Minzhou; Ghali, Kamel; Kosonen, Risto; Melikov, Arsen Krikor; Kilpeläinen, Simo; Ghaddar, Nesreen
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This study proposes using a personal comfort system (PCS) with a ventilated vest to improve the thermal comfort of older people in hot conditions with low energy requirements. A chair-based PCS that establishes a cool microclimate around body parts influential for thermal comfort is used with a ventilated vest that draws cool air from the established microclimate. The vest acts as an additional heat removal measure to provide adequate elderly thermal sensation (TS) with the chair PCS. The research methodology incorporates a ventilated vest model integrated with an elderly bioheat and TS models, as well as computational fluid dynamics for predicting the flow and thermal fields of microclimate and space. Models are validated by i) conducting experiments on a chair-based PCS with a vest on thermal manikin in a climatic chamber and ii) comparing predictions with published data on elderly TS. The validated models are used to evaluate the effect of combining the vest and the chair PCS on improving elderly TS. The combined system reduced the elderly TS from 0.8 to 0.5 (between neutral and slightly warm) at 33 °C microclimate with a chair PCS supply flow rate of 21 l/s and a vest suction fan flow rate of 11 l/s. In contrast, achieving a TS of 0.5 using the chair PCS alone necessitate a supply flow rate of 34 l/s, which results in 19 % higher energy consumption compared to the combined mode. Using the vest with the chair PCS is a viable solution for elderly individuals in hot conditions.
Evaluating thermal response when elderly people using local cooling devices : Correlation among overall and local thermal sensation with skin temperature
(2024-03-01) Chen, Minzhou; Younes, Jaafar; Farahani, Azin Velashjerdi; Kilpeläinen, Simo; Kosonen, Risto; Ghaddar, Nesreen; Ghali, Kamel; Melikov, Arsen Krikor
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The thermal comfort of elderly people in warm indoor environments is important because of their higher risk of heat stress. The use of local cooling devices may help alleviate heat stress. In this study, 26 elderly participants were recruited for climate chamber experiments in neutral (26 °C, 40 % relative humidity (RH)), slightly warm (29 °C, 40 % RH; 28 °C, 60 % RH), and warm (33 °C, 40 % RH; 32 °C, 50 % RH) environments. Three local cooling devices were tested: a table fan, evaporative cooling device, and air-cooled jacket. This study found, in different warm environments, the use of local cooling devices by the elderly results in an mean skin temperature decrease of no more than 0.5 °C. The thermal sensation in the head and torso has the most significant impact on overall thermal sensation. The mean skin temperature (MST) remains an effective physiological indicator for estimating overall thermal sensation after using local cooling devices. The skin temperature in the head, limbs, and extremities plays a substantial role in predicting overall thermal sensation. The thermosensory mean skin temperature (TMST) proposed based on the skin temperature of these parts can more accurately predict overall thermal sensation than MST. This study provides a reference for the development of future local cooling devices. This study has implications for guiding the selection of devices for nursing homes or residential environments for the elderly, and it can be utilized to formulate recommendations for improving device design.
A novel personal comfort system for older adults in hot conditions : Design, modelling, and performance
(2024-01-15) Younes, Jaafar; Chen, Minzhou; Ghali, Kamel; Kosonen, R; Melikov, Arsen Krikor; Kilpeläinen, S; Ghaddar, Nesreen
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This study introduces a novel personal comfort system aimed at establishing a relatively uniform thermal microclimate around the body to meet the thermal needs of seated elderly individuals under hot conditions. The system integrates cool air supply vents into a chair to provide thermal comfort by i) generating upward airflow by colliding jets to disperse cool air across the upper body; and ii) releasing air flow targeting the lower body by relying on buoyancy for air confinement. A computational fluid dynamic model was developed to predict the flow and thermal fields around the occupant who is seated on a chair equipped with the proposed system. The model was experimentally validated in a climatic chamber using a thermal manikin. An elderly bioheat and thermal sensation models were used to predict skin temperatures and corresponding sensation of elderly users. The microclimate was assessed in terms of effective confinement of cool air around users and improvement in elderly thermal sensation. At a total chair supply flow of 17 l/s, microclimate air confinement was attained. At 29 °C room temperature, the proposed system lowered the mean skin temperature from 34.15 °C to 33.33 °C and improved the whole-body TS, which decreased from slightly warm to neutral. At 33 °C room temperature, the mean skin temperature decreased from 35.6 °C to 33.99 °C and the sensation improved, decreasing from above warm to below slightly warm.
A review of thermal comfort modeling of elderly people
(2022-05-05) Chen, Minzhou; Kosonen, Risto; Kilpeläinen, Simo; Ming, Ru
A4 Artikkeli konferenssijulkaisussa
With the global warming and aging of society, the analysis of thermal comfort of elderly people is becoming more important. One example is during heat wave period, the elderly are exposed to a hot environment for a long time, the probability of health problems (cardiovascular disease, mental confusion, etc.) may increase, and even death may occur. The thermal comfort model can predict the human thermal response and evaluate the ambient thermal environment. Therefore, thermal comfort models have a significant effect to improve the thermal sensation of occupants in a built environment. But models being established with adults’ data may not be accurate enough in predicting the thermal response of the elderly. This paper reviews the existing thermal comfort models for the elderly and summarizes different types of thermal comfort models, including the thermoregulatory model, the thermal comfort model, and the machine learning model. The differences and the applicable conditions of models are summarized. This paper provides evidence from literature for the difference in thermal response between the elderly and young people, and also provides a reference for the establishment of a thermal comfort model for the elderly in the future.
Thermal comfort chamber study of Nordic elderly people with local cooling devices in warm conditions
(2023-05-01) Chen, Minzhou; Farahani, Azin Velashjerdi; Kilpeläinen, Simo; Kosonen, Risto; Younes, Jaafar; Ghaddar, Nesreen; Ghali, Kamel; Melikov, Arsen Krikor
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In this study, we investigated the thermal response of Nordic elderly people before and after using local cooling devices in warm conditions. A climate chamber was used to simulate warm environments. We studied three types of local cooling devices: a table fan, an evaporative cooling device, and an air-cooled jacket. A total of 26 elderly participants were recruited for this study. During the experiments, votes of thermal and air movement perception were collected. The elderly voted for a neutral temperature of 26 °C, preferred temperature of 26.5 °C, and an acceptable temperature of 28 °C. Local thermal sensation in the torso areas of the elderly affected their overall thermal sensation more than local thermal sensation in the extremities under warm conditions. When the ambient temperature was risen to 1 °C and 4 °C higher than 26 °C, the behavior pattern of using local cooling devices for the elderly was: 1) with the small rise the use rate reached 50% with the lower speed modes mainly chosen; and 2) the higher rise caused more people to choose higher speed modes. Our findings show that the three local cooling devices can increase thermal acceptability under warm conditions. More than 80% of elderly accepted the 28 °C thermal environment, and less than 80% accepted 32 °C. The acceptance rate for air movement after using devices was decreased and less than 80% in most conditions. Moreover, all devices performed better under low-humidity conditions.
A thermal sensation model for elderly under steady and transient uniform conditions
(2023-01) Younes, Jaafar; Chen, Minzhou; Ghali, Kamel; Risto, Kosonen; Melikov, Arsen K.; Ghaddar, Nesreen
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Sub-optimal thermal conditions influence the health and well-being of elderly people and deteriorate their cognitive functions due to age-induced changes in thermoregulatory mechanisms. Addressing the thermal comfort needs of elderly is better aided when a robust predictive thermal sensation (TS) model exists. However, available TS models in the literature are based on physiological and subjective data collected from young subjects, and their use to assess elderly TS is inappropriate. In this work, a model for predicting elderly TS under steady and transient states was developed from published experimental data under controlled environment. The model predicts the mean TS of elderly people in terms of their average skin temperature, rate of change of skin temperature and core temperature. The model was coupled with a robust elderly bioheat model, enabling the prediction of elderly TS from environmental conditions. The TS model was further extended with a correlation that links the required physiological data for sensation prediction with few segmental skin temperatures that can be measured to enable the development of TS monitoring devices for the elderly. The model and the approach of using segmental temperatures in TS prediction were validated using different experimental measurements and subjective data than those used in the model development. Good agreement between experimental and predicted TS was achieved under varying steady and transient environments. The model predicts the elderly TS in ambient temperatures ranging from 13 °C to 43 °C and in transient settings with up to a 10 °C step rise or drop in ambient temperature.