Browsing Department of Mechanical Engineering & the Built Environment by Subjects
Now showing items 1-4 of 4
Advanced personal comfort system (APCS) for the workplace: A review and case study.The aim of this research is to investigate the application and performance of an advanced personal comfort system, a thermal chair, using Computational Fluid Dynamics (CFD), Building Energy Simulation (BES) and field test analysis. The thermal chair permits individual control over their immediate thermal environment without affecting the thermal environment and comfort of other occupants. A comprehensive review on the existing research on the design and performance of various personalised thermal control systems was carried out. A prototype of a thermal chair was designed for the study and tested in an open plan office during the heating season in Leeds, UK. 45 individuals used the chair in their everyday context of work and a survey questionnaire was applied to record their views of the thermal environment before and after using the chair. The performance of the chair was investigated through CFD simulations (ANSYS Fluent) providing a detailed analysis of the thermal distribution around a thermal chair with a manikin. Furthermore, a model of a three-story office building with thermal chairs were created and simulated in the commercial BES software, IES Virtual Environment. The benchmark model of the building was validated with previous work and good agreement was observed. The results showed that user thermal comfort can be enhanced by improving the local thermal comfort of the occupant. The additional plug-load energy from the thermal chair was significantly less as compared to the heating energy saved by adjusting the heating set point by 2°C during the heating season. Monthly heating energy demand was reduced by 27% on January and 25.4% on February. Furthermore, the results of the field study revealed 20% higher comfort and 35% higher satisfaction level, due to the use of thermal chair.
Computational and field test analysis of thermal comfort performance of user-controlled thermal chair in an open plan officeIn 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.
Neutral thermal sensation or dynamic thermal comfort? Numerical and field test analysis of a thermal chair.Neutral 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.
A user-controlled thermal chair for an open plan workplace: CFD and field studies of thermal comfort performanceThis study aims to improve user comfort and satisfaction regarding the thermal environment in the open plan office, which is a current challenge in the workplace addressed by limited research. The main difficulty in an open plan setting is that changing the room temperature in an area affects all occupants seated nearby. This issue in addition to individual differences in perceiving the thermal environment create a great challenge to satisfy all occupants in the workplace. This study investigates the application of an advanced thermal system, a user-controlled thermal chair, which allows individual control over their immediate thermal environment without affecting the thermal environment and comfort of other occupants. The performance of the chair was further analysed through Computational Fluid Dynamics (CFD) simulations providing a detailed analysis of the thermal distribution around a thermal chair with a sitting manikin. The results indicated that user thermal comfort can be enhanced by improving the local thermal comfort of the occupant. A prototype of an office chair equipped with thermal control over the seat and the back was produced and examined in an open plan office in November in Leeds, UK. Forty-five individuals used the chair in their everyday context of work and a survey questionnaire was applied to record their views of the thermal environment before and after using the chair. The results of the field study revealed 20% higher comfort and 35% higher satisfaction level, due to the use of thermal chair. Thermal measurements showed acceptable thermal conditions according to the ASHRAE Standard 55-2013. Over 86% of the occupants set the temperature settings of the seat and the back of the chair between 29 °C and 39°. 82% of the occupants expressed their satisfaction level as “satisfied” or “very satisfied” regarding the performance of the thermal chair. The thermal chair energy consumption was relatively low (0.03 kW) when compared with that of typical personal heaters, which are about 1–1.5 kW. Further research is recommended to improve the design and application of the thermal chair to improve user overall thermal comfort and also further reduce energy consumption.