Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Building Environment and Energy Engineering | en_US |
| dc.contributor.advisor | Niu, Jianlei (BEEE) | en_US |
| dc.creator | Kumar, Dharmasastha | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/13611 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Performance assessment of cover shield-assisted radiant cooling system for outdoor urban environment | en_US |
| dcterms.abstract | Extreme heat is a growing global threat that requires urgent action to care for vulnerable populations in outdoor environments and protect workers. The year 2023 was considered one of the hottest on record in many cities around the world, but 2024 has proven to be even more scorching, indicating an increasing trend in heat waves across the globe. The more vulnerable groups affected by these heatwaves include bus commuters, daily labourers working outdoors, road workers and the homeless. Deadly heat stress and heat strokes are experienced as dire consequences of the heat waves sweeping through communities. With temperatures rising, there is a critical need to implement measures that shield these at-risk populations from the dangers of extreme heat. | en_US |
| dcterms.abstract | Localised outdoor cooling hubs have the potential to address this problem and can protect the public in the outdoors from heat waves. In the current situation of record-breaking temperatures every year, i.e., for instance, crossing 52°C in China, and India, the common passive cooling strategies such as shading, fan cooling, green roofs and blue-green infrastructure, are questionable to protect people from extreme heat. The evaporative cooling, mist cooling, and air conditioning have been utilized in the outdoors in some cities, but they are ineffective and energy-intensive, especially in hot and humid climates. | en_US |
| dcterms.abstract | The cover shield-assisted radiant cooling system is one of the alternative potential cooling solutions for outdoor cooling applications. It can treat the radiant load directly and reduce convective heat loss to the surroundings. An infrared-transparent cover shield, such as a low-density polyethylene (LDPE) membrane is used to cover the radiant panel. The cover shield allows infrared radiation from the surroundings but reduces convective heat transfer to the ambient. | en_US |
| dcterms.abstract | This technology has been proven to be effective in semi-outdoor environments. However, outdoor cooling using this technology has yet to be investigated. In this research, the localised cooling hub integrated with the cover shield-assisted radiant cooling system is investigated using Computational Fluid Dynamics (CFD) modelling. It aims to investigate the thermal and comfort performance of the proposed localised cooling hub for the urban outdoor environment. | en_US |
| dcterms.abstract | A three-dimensional, steady-state CFD model of the proposed cooling system has been developed for an outdoor urban environment. The thermal performance of the localised outdoor cooling hub system is investigated for an open space in the hot and humid climate of Hong Kong. The heat transfer characteristics of the proposed cooling system are analyzed for various cover shield materials under realistic ambient conditions of the summertime in Hong Kong. It was found that the sky-window selective membrane outperforms other materials. However, this membrane is still in the development stage. In situations where there is no direct solar exposure, a non-selective membrane can be preferred over a mid-infrared selective membrane, as the non-selective membrane can provide the same cooling performance in the absence of direct solar radiation. | en_US |
| dcterms.abstract | In order to overcome the limitations of the existing outdoor comfort models, a methodology to couple the CFD simulation with the human body thermoregulation system has been developed. The skin temperature obtained from the coupling method is used to determine the human thermal sensation in the outdoor environment using the updated CBE comfort model. The thermal sensation obtained from this method has been compared with the thermal comfort survey conducted in the experimental facility of a localised outdoor cooling hub employed with membrane assisted radiant cooling system. | en_US |
| dcterms.abstract | The thermal and comfort performance has been investigated for the street canyons of Hong Kong, in terms of the heat extraction rate of the cooling system and thermal sensation experienced by the occupants. The obtained thermal sensation has been compared with the thermal sensation experienced by the people standing in the shaded spot without any cooling. The results are more promising that the proposed cooling system performs well in the typical summer weather of Hong Kong. | en_US |
| dcterms.abstract | The present research has identified that the proposed radiant cooling system is a suitable solution for outdoor applications. However, the current structure design of the system requires optimization to improve the heat exchange between the cooling panel and the human body, as well as to reduce the impact of solar radiation. Optimizing the system design will not only enhance its energy efficiency but also provide better comfort for users. Future work should focus on integrating the proposed cooling system with low-grade energy sources, such as waste heat or renewable energy, to develop a more sustainable and livable cooling solution for outdoor urban environments. | en_US |
| dcterms.abstract | By addressing the design limitations and exploring the integration of low-grade energy sources, the proposed radiant cooling system has the potential to become a more comprehensive and effective solution for mitigating the challenges of extreme heat in outdoor spaces. | en_US |
| dcterms.extent | xxvii, 189 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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