PMV-PPD Model Research Articles

Thermal comfort expectations and adaptive behavioural characteristics of primary and secondary school students

This study aims to better understand thermal comfort perception and related behavioural characteristics of school children. Statistical analyses were performed on the thermal comfort survey database consisting of 4866 responses collected from primary- and secondary school classrooms in Australia across two summer seasons. The students generally preferred ‘cooler-than-neutral’ sensations, with the preferred temperature being estimated to be 2–3 K below the neutrality predicted for adults under the same thermal environmental exposures. The students' 80% acceptability zone empirically derived from group mean thermal sensations, was significantly wider than the band of ±0.85 thermal sensation votes assumed in the PMV-PPD model. The school children indicated air-conditioning as their favoured thermoregulatory method, among many other adaptive options including windows, fans, blinds or clothing adjustments. The results indicated that those students already placed in air-conditioning classrooms were more likely to prefer air-conditioning for the maintenance of their comfort, compared to those accommodated in classrooms without air-conditioning.

A Study on the Thermal Comfort under Non-uniform Thermal Environment

It aims to study the effect of the thermal non-uniformity on human’s thermal responses, and illustrate the other potential impact factors to the overall thermal comfort besides overall thermal sensation in non-uniform thermal environment. Totally 9 non-uniform thermal envi-ronment conditions with locally supplied airflow were created. Subjects’ thermal sensation as well as thermal comfort on the whole body and the body parts were surveyed under the steady state. Thermal comfort was dispersed with a fixed thermal sensation. In most cases, percentages of dissatisfied (PD) were higher than the predicted percentages of dissatisfied (PPD) by PMV-PPD model with the same thermal sensation. The deviation between PD and PPD increased with thermal non-uniformity level. It also increased along with the decrease of the local thermal comfort level, which is induced from the rising of the thermal non-unifomity level of the environment. PD was deduced to be derived from the local thermal comfort besides whole body’ thermal sensation.

Experimental and numerical investigations of the energy efficiency of conventional air conditioning systems in cooling mode and comfort assurance in office buildings

This paper provides a comparative study of the energy efficiency of a conventional ventilating and air conditioning (VAC) system with three configurations. This system was used to cool an experimental room in an office building in more control scenarios realised by adopting different cooled water temperatures and chiller cooling systems. In this purpose, an air–water mist cooled system for an air-cooled chiller is proposed. Depending on the components, the analysed VAC system has the following configurations: (1) air handling unit (AHU) and fan-coil units (FCUs); (2) air handling unit (AHU); and (3) heat recovery unit (HRU) and fan-coil units (FCUs). The electricity consumption weight of the equipment of each VAC system, the total energy consumption and the influence of control parameters on this consumption are analysed. The results of the experiments indicate that the optimal efficiency VAC system in office buildings includes an AHU and FCUs with an air–water mist cooled chiller and a cooled water temperature of 8°C. For this system, a mathematical model is developed to minimise the electricity consumption by optimal control, where the consumption depends only on non-controlled parameters (solar radiation intensity and outdoor air temperature). This model is verified with actual measurements to confirm its accuracy, and a good agreement between the prediction and measurement is achieved. Additionally, the assessment of thermal comfort in the experimental office is performed based on the PMV-PPD model using the ASHRAE Thermal Comfort programme. The obtained results demonstrate that the AHU&FCUs system assures an increase in thermal comfort. Finally, a TRNSYS simulation model of energy consumption and PMV-PPD indices for the AHU&FCUs system is developed and experimentally validated.

An adaptive thermal comfort model for hot humid South-East Asia

The present paper presents a full procedure to develop an adaptive comfort model for South-East Asia. Meta-analysis on large number of observations from field surveys which were conducted in this region was employed. Standardization and bias control of the database were fully reported. Statistical tests of significance and weighted regression method applied in the analyses strengthened the reliability of the findings. This paper found a great influence of ‘Griffiths constant’ on the establishment of adaptive comfort equation and proposed an appropriate value. The adaptive comfort model generated is applicable to naturally ventilated building under hot and humid conditions of South-East Asia. The mean neutral comfort temperature (operative temperature, effective temperature, standard effective temperature) in naturally ventilated and air-conditioned building was compared and the differences have been discussed. The similar neutral standard effective temperature in both naturally ventilated and air-conditioned building proposes a new idea to implement SET* into building simulation tools to assess thermal comfort without the attention of building classification.Through the analysis, the effectiveness of behavioral adaptive actions on occupant's thermal perception has been argued. The extended PMV-PPD model for hot humid conditions was examined and its applicability was recommended. Other comfort-related issues, the differences and similarities between various adaptive comfort models were also addressed.

An Assessment of the Overall Comfort Sensation in Workplaces

The scope of the research described in this paper is to develop, evaluate and propose a newempirical index, the so-called Index of Workplace Comfort (IWC), which quantifies the overallcomfort sensation of a user in an office building. The proposed Index of Workplace Comfort is calculated on the basis of both environmental and psychological properly weighted sensation votes of workplace occupants. The weight of 13 variables in the equation of IWC is determined through ordered probit regression in a dataset, using a background questionnaire completed by 238individuals working in 11 office buildings. The evaluation of the proposed index consisted of the implementation of the IWC model in a building (52 cases) and the comparison with data collected from thermal comfort measurements based on ISO 7730 (159 cases) and thermal sensation votes of the occupants (321 cases). The findings show, with statistical significance, that the IWC describes the overall comfort conditions better than the PMV-PPD model used in ISO 7730 andsupports the position that psychological variables affect the overall comfort sensation of individuals in a workplace.

Effect of balconies on thermal comfort in wind-induced, naturally ventilated low-rise buildings

The presence of the parapet and floor of a balcony is expected to have a range of effects on a building’s environmental behaviour, in terms of aspects, such as natural ventilation, thermal comfort, pollutant transportation and shading and daylighting. The authors have previously reported that the presence of a balcony can significantly increase the air flow rate of most rooms in a naturally ventilated building. In this study, the CFD technique and Fanger and Toftum’s extended PMV—PPD model are combined to investigate numerically the effect of a balcony on thermal comfort for naturally ventilated buildings in tropical-humid regions. The results show that although a balcony reduces the indoor average velocity for most rooms, and in turn increases the PMVnv value in both the seated and standing positions, it does not change the indoor thermal comfort level. However, the presence of a balcony improves comfort by increasing the uniformity of indoor air distribution. PMVnv is also shown to be less sensitive to velocity than PMV, allowing for a wider thermal comfort range for naturally ventilated buildings. Practical application: This study will help designers and engineers who are considering the use of a balcony at the design stage to have a better understanding of its effect on thermal comfort in naturally ventilated buildings.

Building envelope regulations on thermal comfort in glass facade buildings and energy-saving potential for PMV-based comfort control

This paper presents an investigation of the effect of building envelope regulation on thermal comfort and on the energy-saving potential for PMV-based comfort control in glass facade buildings. Occurrences and severity of overheating, based on the PMV-PPD model contained in ISO 7730, were used for the thermal comfort assessment. Parametric study simulations for an actual building with a large glass facade were carried out to predict the changes in thermal comfort levels in a space due to different glazing types, depths of overhang and glazing areas, which are the key parameters of the building envelope regulation index, named ENVLOAD, in Taiwan. The result demonstrates that the ENVLOAD has significant effect on thermal comfort. Additionally, comparative simulations between PMV-based comfort control and conventional thermostatic control were performed to investigate the changes in the energy-saving potential of a thermal comfort-controlled space due to changes of its ENVLOAD. The results demonstrate that the energy-saving potential in a PMV-based controlled space increases with low ENVLOAD conditions.

Influence of the ventilation system on thermal comfort of the chilled panel system in heating mode

In heating mode, fresh air is still essential for a chilled panel system in order to ensure the indoor air quality. In this paper, a chilled ceiling panel system was designed and built in a typical office room. The thermal environment and thermal comfort in the room were fully measured and evaluated by using the Fanger's PMV–PPD model and the standard of ISO 7730 respectively, when room was heated in two modes, one of which is the chilled panel heating mode and the other of which is the combined heating mode of chilled panel and supply air. The research results indicate that in the combined mode, ceiling ventilation improves the general thermal comfort and reduces the risk of local discomfort. Under the condition of same general thermal comfort, the heating supply upper limit of chilled panel can be increased by 12.3% because of air mixing effect caused by introduction of air ventilation.

Additive model for thermal comfort generated by matrix experiment using orthogonal array

In addition to ensuring the thermal comfort of occupants, monitoring and controlling indoor thermal environments can reduce the energy consumed by air conditioning systems. This study develops an additive model for predicting thermal comfort with rapid and simple arithmetic calculations. The advantage of the additive model is its comprehensibility to administrators of air conditioning systems, who are unfamiliar with the PMV–PPD model but want to adjust an indoor environment to save energy without generating complaints of discomfort from occupants. In order to generate the additive model, a laboratory chamber experiment based on matrix experiment using orthogonal array, was performed. By applying the analysis of variance on observed thermal sensation votes and percentage of dissatisfaction, the factor effects of environmental variables that account for the additive model were determined. Additionally, the applicability of the PMV–PPD model in hot and humid climates is discussed in this study, based on experimental results.