Neutral thermal sensation or dynamic thermal comfort? Numerical and field test analysis of a thermal chair.
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AbstractNeutral thermal sensation is considered as the measure of thermal comfort in research, as when participants report feeling neutral regarding the thermal environment, they are considered as thermally comfortable. This is taken for granted, and although a few researchers have criticised the matter, still researchers use thermal sensation and the neutral point to assess the thermal conditions in their studies. This study questions the application of thermal neutrality and consequently poses a question on the findings of all the studies that only rely on it. Field studies of thermal comfort were applied in an open plan office in the UK in the winter of 2014. Participants were provided with a thermal chair and before and after using the chair, their views of comfort were recorded, including the ASHRAE seven point scale of thermal sensation, thermal preference, comfort, and satisfaction. The thermal environment was measured and compared against the ASHRAE Standard 55-2013. In addition, numerical modelling was also conducted to investigated the airflow and thermal distribution around the proposed thermal chair with a seated occupant. The results indicated that overall, 72% of the respondents, who did not feel neutral (thermal sensation) before or after using the thermal chair reported to feel comfortable and 65% reported to be satisfied. The results indicated that a neutral thermal sensation does not guarantee thermal comfort of the occupants and that thermal comfort is dynamic and other thermal sensations need to be considered. This study recommends the use of multiple methods (e.g. thermal, preference, decision, comfort, and satisfaction) to assess thermal comfort more accurately. Also, it questions the findings of any research that solely relies on thermal sensation and particularly on the neutral thermal sensation to assess thermal comfort of the occupants. The results also emphasised the importance of the application of numerical modelling in evaluating the thermal performance of the chair.
CitationShahzad, S. et al (2017) 'Neutral thermal sensation or dynamic thermal comfort? Numerical and field test analysis of a thermal chair', Energy Procedia, 142:2189.
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Computational and field test analysis of thermal comfort performance of user-controlled thermal chair in an open plan officeShahzad, Sally; Calautit, John Kaiser; Hughes, Ben; Nasir, Diana S. N. M.; University of Derby; University of Sheffield (Applied Energy, 2016)In this study, a thermal chair prototype was developed that allowed individual control over the temperature settings of the backrest and the seat. Limited research is focused on different methods to provide individual user control over the thermal environment. This is particularly difficult to achieve in an open plan office setting, where changing the temperature in one area directly influences the comfort and satisfaction of other occupants seated nearby. In this study, the application of the thermal chair was analysed using Computational Fluid Dynamics (CFD) and field-test analysis in an open plan office in Leeds, UK during winter. The results of the CFD model indicated an improvement in local thermal comfort of the user,. The CFD analysis provided detailed analysis of the thermal distribution around a siting manikin and was used to design and construct the thermal chair. the results of the field data survey indicated a great improvement in users’ comfort (19%) and satisfaction (35%). This study concludes that local thermal control of the occupant improves their overall thermal comfort. It recommends further work to optimise the design of the thermal chair and also to improve the modelling for better predictions.
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