Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Building Environment and Energy Engineering | en_US |
| dc.contributor.advisor | Chen, Qingyan (BEEE) | en_US |
| dc.contributor.advisor | You, Ruoyu (BEEE) | en_US |
| dc.creator | Bhuvad, Sushant Suresh | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/14272 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Identify sustainable and accessible cooling strategies to keep individuals cool during extreme heat events | en_US |
| dcterms.abstract | New temperature highs were recorded throughout 2024 as a record-breaking and deadly heat wave swept across the Americas, Africa, Europe, and Asia. These extreme heat waves have a direct negative impact on human health, causing exhaustion, heatstroke, and even fatalities. The simplest cooling solution against these heat events is air conditioning. However, it is energy-intensive and not universally available, especially for vulnerable people. Furthermore, the increased use of air conditioning creates a vicious cycle, as it contributes to global warming in the long term. Therefore, there is an urgent need to identify sustainable, affordable, and widely accessible cooling strategies to protect individuals from extreme heat events. | en_US |
| dcterms.abstract | Various sustainable and accessible cooling methods, such as electric fans, cold water ingestion, foot immersion, leg immersion, and self-dousing, can help mitigate the adverse impacts of extreme heat. Among these strategies, electric fans are a widely adopted method. However, existing heat wave guidelines have often discouraged fan use. However, recent research suggests that guidelines may have overlooked the evaporative cooling potential of fans. Nonetheless, previous investigations have primarily examined the physiological responses associated with table fans. However, the air movement produced by both table fans and ceiling fans may influence the occupants' physiological and perceptual responses differently. Hence, our first study focused on evaluating the effectiveness of no-fan, table-fan, and ceiling-fan scenarios during heat waves through an experimental approach. We conducted 2-hour controlled human trials in a climate chamber set to typical heatwave conditions (air temperature 41°C and relative humidity 35%), involving 16 healthy young adults. We found that both fan types delayed thermoregulatory and cardiovascular strain relative to the no-fan scenario. Notably, table fans delivered better physiological relief compared to ceiling fans, implying that table fans are preferable during heat waves. Furthermore, we examined varying airflow rates for table fans and found that higher fan speeds further reduced physiological strain and better overall comfort under the tested conditions. | en_US |
| dcterms.abstract | Although laboratory trials provide valuable insights into the effectiveness of fans during heat waves, they cannot represent how prolonged extreme heat affects the human body, given participant safety and ethical constraints. Therefore, to better inform public health decisions, we further evaluated the effectiveness and thresholds of electric fans across various physical activity levels for young adults during prolonged extreme heat events using a thermoregulation model. First, we modified the thermoregulation model by updating the hydration, sweating, and vasodilation processes. Further, moderate hyperthermia onset charts are presented across various fan speeds and activity levels to assess fan performance. Under moderate environmental conditions (40°C and 50% RH), fan use effectively delayed hyperthermia onset, particularly at lower physical activity levels (PAR)- 1.2 and higher fan speeds. In these scenarios, increased sweat evaporation due to higher fan speeds outweighed sensible heat gain, thus reducing overall heat stress. However, under extreme conditions—such as temperatures exceeding 46 °C and relative humidity above 60% —the benefits of fans diminished significantly, accelerating the onset of hyperthermia. In such environments, higher fan speeds worsened conditions as increased air movement amplified sensible heat gain from the environment, outweighing the evaporative cooling benefits. For instance, at 50 °C and 40% RH, increasing fan speed from 0.8 m/s to 3.0 m/s reduced the hyperthermia onset time further, demonstrating the detrimental effect of high fan speeds under these extreme conditions. Results showed that fans are beneficial up to 42 °C and 10−20% RH at light activity (1.2 PAR) but become trivial or detrimental at higher temperatures and humidity, particularly under elevated activity. Overall, our findings suggest that fans effectively reduce thermal strain in moderate heat and humidity but may prove less helpful—or even harmful—in extreme scenarios, especially at elevated activity levels and fan speeds. Hence, we recommend that future health guidelines clearly define thresholds for temperature, humidity, fan speed, and physical activity when advising fan use during heat waves. | en_US |
| dcterms.abstract | Electric fan use can become detrimental and may rapidly increase core body temperature in extreme heat environments. Therefore, we investigated alternate sustainable water-based cooling strategies, including foot immersion, leg immersion, and self-dousing, using a further modification of the thermoregulatory model. The model systematically examined the effects of foot immersion and leg immersion at different water temperatures over a 30-minute immersion session with a 15-minute time break. For dousing, the area of water application was varied to optimize the cooling approach and minimize thermo-physiological strain in hot environments. Our results indicated that leg immersion provided a significant core temperature reduction, lowering it by approximately 0.3−0.7 °C compared to no cooling approach. Foot immersion and self-dousing offered moderate cooling, with the effectiveness of dousing dependent on the body surface area exposed. The maximum temperature reduction achieved by foot immersion compared to no cooling was around 0.3 °C. In hot and humid climates, self-dousing was less effective due to reduced evaporation rates. These findings emphasize that water immersion and self-dousing can serve as valuable cooling strategies. In particular, leg immersion emerges as a simple, sustainable, and highly promising method for mitigating severe heat stress. | en_US |
| dcterms.extent | xxiii, 164 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2025 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.accessRights | open access | en_US |
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