PMV-PPD Model Research Articles

Parametric analysis of chiller plant energy consumption in a tropical climate

The approach that could reduce the energy consumption of water-cooled chillers in office buildings was investigated through experimental and simulation methods. The chiller was modelled in TRNSYS and validated using physical measurements from an operational water-cooled water chiller and fan coil system. The validated model was used to analyse the energy consumption of the water chiller-fan coil system under a high chilled water temperature setpoint (CWTS) in a representative commercial office building. Subsequently, indoor thermal comfort was evaluated using the PMV-PPD model. Finally, the design of experiment (DOE) was employed using a statistical two-level non-randomized factorial design in Minitab to study the effects of high CWTS, number of rows, and tube diameter on the heat and mass transfer performance of the fan coil unit. The results showed that the CWTS can be increased by various degrees from 10 up to 18 °C for energy efficiency for a commercial office building in the tropics. This increase in CWTS would result in a daily energy saving potential of about 5% of the chiller as compared to the existing operational settings without any extra cost. Conversely, the daily energy consumption by the fan coil would increase by about 5.5% by this increment in the CWTS. It was determined that the chiller system can provide comfort even when the CWTS is increased to 14 °C. The DOE analysis showed that under the condition of high CWTS (14 °C), energy consumption that is less than the current energy consumption may be expected from the fan coil system when the number of rows increased from 3 to 6 and the tube diameter increased from 7 to 9 mm.

Assessment of Thermal Comfort in an Electric Bus Based on Machine Learning Classification

In electric buses, heating, ventilation and air conditioning are responsible for up to 50% of the energy consumption. It is therefore necessary to identify improved thermal settings to minimize the energy consumption, while guaranteeing good thermal comfort. Hence, an accurate prediction of the passengers’ thermal sensation (TS) is needed. One of the most widely used models for TS prediction is the PMV-PPD model, which has been shown to provide reliable results in uniform, steady-state climatic conditions. Since these are not present in an urban bus, the accuracy of the PMV-PPD model diminishes. Additionally, some of the parameters needed are difficult to obtain (i.e., clothing insulation). This paper presents seven different machine learning models (ML) for the prediction of TS using three different sets of parameters. The first set comprises five parameters similar to the PMV-PPD model, the second uses only two, and the third uses all parameters available. To obtain the necessary data, climatic measurements in an electric bus in Berlin, Germany, were made. These measurements were performed in summer for ambient temperatures between 14.7 °C and 32.0 °C. Person-related information as well as the thermal comfort assessment were obtained via surveys. Despite the relatively small data set, four of our seven ML models performed well with a median accuracy between 70.3% and 69.4%. This could also be observed when using only two parameters. Hence, the efforts to gain experimental data can be reduced significantly. For the PMV-PPD model, a median shift of +1 was observed for mild and warm TS. The median accuracy rises from 48.8% without shift to 68.8% with shift.

Research on Prediction and Regulation of Thermal Dissatisfaction Rate Based on Personalized Differences

Thermal discomfort body language has been shown to be a psychological representation of personnel’s particular thermal comfort. Individual thermal comfort differences are ignored in public building settings with random personnel flow. To solve this issue, we suggested a Bayesian group thermal dissatisfaction rate prediction model based on thermal discomfort body language expression and subsequently implemented intelligent indoor temperature and humidity control. The PMV-PPD model was utilized to represent the group’s overall thermal comfort and to create a prior distribution of thermal dissatisfaction rate. To acquire the dynamic distribution of temperature discomfort body language, data on thermal discomfort body language expression were collected in a real-world office setting experiment. Based on Bayesian theory, we used personalized thermal discomfort body language expressions to modify the group’s universal thermal comfort and realized the assessment of the thermal dissatisfaction rate by combining commonality and personalization. Finally, a deep reinforcement learning system was employed to achieve intelligent indoor temperature and humidity control. The results show that when commonality and personalized thermal comfort differences are combined, real-time prediction of thermal dissatisfaction rate has high prediction accuracy and good model performance, and the prediction model provides a reference basis for reasonable indoor temperature and humidity settings.

Investigating the effects of climate on thermal adaptation: A comparative field study in naturally ventilated university classrooms

In educational buildings, adaptive strategies can be adopted for the achievement of thermal comfort and reduction of energy consumption. Since climate can largely affect thermal comfort, there is a need for understanding its role in the definition of different adaptive capacities, thermal neutrality, comfort, and preference.To this end, 17 naturally ventilated university classrooms from 10 different buildings located in two sub-climates of Italy (Mediterranean climate) and France (Continental climate) were analysed. In total, 1377 questionnaires associated with environmental parameters were collected. The same educational stage (i.e. university classrooms) and operation mode (i.e. naturally ventilated during the heating period) were investigated to remove possible biases related to their influence on thermal comfort perception.Field studies show that despite French students performing less adaptive actions, their neutral temperature (TN) was 3.1 °C lower than the Italian ones (TN,ITALY = 23.6 °C and TN,FRANCE = 20.5 °C) and this difference was statistically significant.Adaptation as a function of the sub-climate was evident from the comparison with the PMV-PPD model. Neutral temperatures calculated with PMV were higher than those obtained from TSV, and the difference increased for the French colder climate.Practically, students’ adaptation to colder environments can be deployed to ensure comfort while reducing the heating demand.

The role of design parameters on the performance of diffuse ceiling ventilation systems – thermal comfort analyses for indoor environment

ABSTRACT Thermal comfort conditions profoundly affect the occupants’ health and productivity. A diffuse ceiling ventilation system is an air distribution system in which the air is supplied to the occupied zone with relatively a low velocity through the perforated panels installed in the ceiling. The current study evaluated the impact of diffuse ceiling design parameters, i.e. diffuse panel configurations and heat load distributions, on the thermal comfort condition of the occupants. In this regard, the computational fluid dynamics technique was used to evaluate thermal comfort conditions in a waiting room, meeting room and office. The central and dispersal configuration of active diffuse panels was considered. The PMV-PPD model was applied to evaluate the overall occupants’ comfort, while the draft rate was considered to assess local thermal comfort. The model validation was performed by comparing the collected laboratory measurement data. Overall, the results indicated that the central active diffuse panel configuration had a better thermal comfort than the dispersed one. The evaluation of dispersed configuration in realist scenarios, including office and waiting room, had the highest dissatisfaction, with a PPD value of 9%. Local thermal comfort assessment revealed that dispersed configuration had the highest draft rate of 14% in the office.

A structural wall incorporating biosourced earth for summer thermal comfort improvement: Hygrothermal characterization and building simulation using calibrated PMV-PPD model

The drive to design modern low-environmental impact buildings with high-energy efficiency has led to an increase in unfired earth masonry studies reflecting the rising trend of earth used in passive buildings. This paper deals with the efficacy of incorporating biosourced earth in the building envelope. Firstly, the development and the hygro-thermo-mechanical characterization of earth blocks biosourced with local agro-aggregates (Alfa fibers and sawdust) were conducted. An aggregate-to-earth replacement ratio of 8 wt% was adopted. Mechanical tests show that earth blocks alone have a compressive strength of about 1.7 MPa. The hygrothermal tests reveal that biosourced blocks exhibit excellent hygrothermal properties, especially specimens with short Alfa fibers. A twofold decrease in the thermal conductivity value and a significant increase of the time lag and sorption capacities were achieved. The moisture buffering tests show that Alfa fibers improve the buffering capacity of earth from 1.9 to 2.3 g/(m2.%RH), leading the blocks to be classified as “Excellent” humidity regulators. Following the laboratory tests, and to overcome the low mechanical strength of earth, a double hollow brick wall integrating biosourced earth was studied. Building-scale benefits during summer were identified using a validated PMV-PPD model, implemented in EnergyPlus, based on real-time monitoring of an existing building. The findings show that the proposed wall increases thermal comfort by regulating indoor temperature and humidity, reducing 24.6% in dissatisfied occupants compared to typical walls. It is concluded that the use of earth presents a sustainable practice for constructing eco-efficient buildings with enhanced occupant satisfaction in hot regions.

Thermal response test analysis of adults and preschoolers under radiant floor heating environment in a hot-summer and cold-winter area

The subjective and objective thermal comfort evaluations of adults and preschoolers in radiant floor heating rooms in a hot-summer and cold-winter area are tested in this article, and the thermal response of the two groups of subjects are analysed using a differential analysis method. The thermal response characteristics of subjects wearing winter clothing with a thermal resistance of 1.02 clo and maintaining a sitting posture were studied at different locations in the office building and different indoor temperatures by combining the characteristics of hot-summer and cold-winter area and the characteristics of office buildings. The results show that when the indoor temperature varies, there was a significant difference in the local skin temperature of the calf of the two groups of subjects (P<0.05). Preschoolers have a more intense overall thermal sensation vote than adults due to the difference in metabolic rate. Different groups of people’s overall thermal sensation vote were linearly correlated. The overall thermal sensation vote of the subjects is linearly related to the indoor operative temperature. The PMV-PPD model is used as the thermal sensation evaluation standard, and there is a considerable difference between the subjective appraisal of preschoolers’ thermal sensations. The PMV-PPD model is not suitable for preschoolers.

Field studies on thermal comfort of passengers in airport terminals and high-speed railway stations in summer

In transportation buildings such as airport terminals and railway stations, the thermal comfort of passengers is associated with the energy consumption of HVAC systems. Previous studies did not reach consistent conclusions on the differences in thermal comfort demands of passengers with different dwell times in waiting halls. In addition, the thermal comfort of passengers in various sessions during the departure and arrival processes, such as security checks and walking, was not addressed. Therefore, we conducted field studies in the waiting halls of ten transportation buildings and 12 simulated experiments of departure and arrival processes in five of these terminals, with 10 subjects in each experiment. A total of 1,576 valid questionnaires were collected from the waiting halls. The results showed that passengers were more adaptable to the indoor thermal environment than the results foreseen by the PMV–PPD model. As the dwell time increased, the adaptability of the passengers to the indoor thermal environment was approximately the same. However, the neutral standard effective temperature (SET) and preferred SET increased with time. The current indoor thermal design parameters of GB 50736 can meet passengers’ thermal comfort during short-distance departure and arrival processes. Under low air velocity conditions (< 0.2 m/s), the 90% acceptable indoor operative temperature (Top) ranged from 21.9 °C to 25.4 °C for the security check and from 23.9 °C to 25.2 °C for the long-distance processes.

Confort térmico en vivienda social multifamiliar de clima cálido en Colombia

El consumo energético residencial en Colombia incrementó 30% en los últimos 7 años debido en parte al gasto destinado a climatización activa de Viviendas de Interés Social (VIS). Investigaciones sobre VIS unifamiliares reportaron sensaciones térmicas “muy calurosas” con el modelo PMV-PPD en clima cálido. El objetivo de esta investigación es complementar el estado del arte evaluando el ambiente térmico de una VIS multifamiliar con dos diferentes modelos de confort: el PMV-PPD y el Adaptativo. La metodología tuvo dos fases: Monitoreo a un ambiente VIS y valoración mediante los dos modelos. Los resultados indicaron insatisfacción térmica por exceso de calor con ambos modelos en horas diurnas muy similares a lo reportado en el estado del arte para tipología unifamiliar. Sin embargo, se encontró un ahorro en energía dedicada a climatización del 35% si se valora con el Modelo Adaptativo. Se evidenció la ausencia de protección solar en vanos y los altos valores de temperatura del aire y media radiante indicaron que el aislamiento térmico de la envolvente vertical de estas edificaciones es insuficiente para brindar confort térmico, se proponen mejoras pasivas para mejorar su habitabilidad e inclusión obligatoria en el Reglamento 0549 para reducir el consumo energético y su impacto ambiental.

Assessment of Thermal Comfort in Operating Rooms Using PMV-PPD Model

Operating rooms (ORs) are the most critical and expensive sector of healthcare facilities. The air conditioning system is designed to provide a well-controlled indoor air quality (IAQ). This design guarantees a perfect infection control and a good thermal comfort of patient and operating staff.This paper aims to analyze and evaluate indoor thermal comfort at different cases to assign the proper inlet air temperature to the OR. The predicted mean vote (PMV) and the predicted percentage dissatisfied (PPD) models in accordance with ISO 7730 were used for this study.Field measurements were first carried out in an OR at Kafr El-Sheikh educational hospital to get the thermal environment parameters. These parameters are required to determine the thermal comfort indices namely (PMV & PPD). Four different cases of supplied air temperature 17.5, 18.5, 19.5 and 20.5oC were studied and compared through 105 measuring points distributed in the operating room. The PMV and PPD indices were computed at each case for three groups of medical staff: surgeons (metabolic rate equal to 120 W/m2), nurses and surgeon's assistants (100 W/m2), anesthetists (70 W/m2).The results revealed that inlet air temperature has a minor effect on the air velocities and airflow patterns inside the OR at the same air change rate. For the current ventilation system, it is difficult to create a very comfortable work conditions for all operating staff at the same time due to their different thermal requirements. It was concluded that a supplied air temperature of 18.5oC provides almost comfortable conditions for all surgical staff.

Thermal comfort in mixed-mode buildings: A field study in Tianjin, China

Mixed-mode (MM) buildings, integrating a naturally ventilated (NV) mode and an air-conditioned (AC) mode, have gained popularity in recent years. However, there is no consensus among previous studies on how to evaluate the thermal comfort of occupants of MM buildings. This study aims to compare the applicability of the PMV-PPD model and the adaptive model in MM buildings and to verify whether the occupants' thermal perception varies with different operating modes. A field study was conducted in an MM office building in Tianjin, China from March 2019 to January 2020, covering four seasons. Through a statistical analysis of environmental parameters and occupants’ thermal responses, the difference in the thermal perception of occupants was observed between the two modes. The actual neutral Top (24.5 °C) was higher than the prediction calculated by PMV (23.0 °C). When the indoor Top was within the 80% acceptability limit of the adaptive model in ASHRAE Standard 55, over 80% of the occupants found the thermal environment acceptable in both AC-cooling mode and NV mode. The results revealed that the PMV-PPD model was not suitable for MM buildings, and the adaptive model showed better applicability in both AC-cooling mode and NV mode. Compared with the Beijing case in ASHRAE Global Thermal Comfort Database Ⅱ, the occupants in the current study had a higher neutral SET (24.3 °C) and better adaptability to the thermal environment. This study also showed that well-designed MM buildings were potentially applicable in mid-latitude temperate regions with four distinct seasons.

Thermal comfort and physiological responses with standing and treadmill workstations in summer

The study investigates human thermal comfort requirements when using standing and treadmill workstations. Twenty-eight subjects were exposed to four ambient temperatures (20, 23, 26, 29 °C) while conducting four activities (sitting, standing, walking at 1.0 km/h, and walking at 2.0 km/h). Physiological responses, including metabolic rate, skin temperature, and skin wettedness, were measured continuously, while subjective thermal comfort responses were surveyed. Treadmill workstation significantly increased human metabolic levels and reduced the associated environmental neutral temperatures. Using linear regressions, the predicted neutral temperatures are 24.3 °C (sitting), 23.3 (standing), 22.2 (walking 1 km/h), and 21.1 °C (walking 2 km/h), respectively. The 80% acceptable temperature range varied from 20.5 to 28.2 °C for sitting and standing, 20.0–26.9 °C for walking 1 km/h, and 17.6–26 °C for walking 2 km/h. PMV-PPD model was not able to predict human comfort accurately when using standing or treadmill workstations. Based on our findings, a temperature zone ranging from 20.5 to 26 °C is seen to satisfy the summer thermal requirements for over 80% occupants in a space containing a combination of sitting, standing, and treadmill workstations. However, providing personal comfort control would be necessary, given the substantial inter-individual differences.

Subjective and objective assessment of thermal comfort in physiotherapy centers

Physiotherapy centers represent a special environment since different activities are performed by the occupants, i.e., therapists and patients, who might have very different ages, metabolic rates, health status and clothing, as well as perform various types of treatment. In this framework, this study aims to provide an original contribution to the literature with new experimental data of objective and subjective assessment of thermal comfort conditions in these facilities.Thermal comfort in four physiotherapy centers in Northern Italy and Denmark was analyzed during the heating season according to the PMV-PPD model and to a subjective approach, performing long- and short-term measurements of ambient parameters and submitting questionnaires to both therapists and patients, before and after therapies.Patients preferred temperature ranges of 22.5–24.5 °C and 20–22.5 °C, respectively during static and dynamic treatments, while therapists seemed to better adapt to the environment by adjusting their clothing level. Therapists and patients differed only in thermal satisfaction and only in some of the centers. Gender, age, health and clothing were found significant parameters. After therapy, patients’ answers showed variations only for thermal satisfaction in some centers where static therapies are performed, and for thermal sensation in cases of dynamic therapies. Thermal perception was generally closer to neutrality than predicted with the PMV-PPD model.As a whole, if integrated with other similar works, these results can be exploited to support the development of a database for creating guidelines to address the requirements of the two categories of occupants.

A case study on thermal comfort analysis of school building

Numbers of occupants in school buildings are high and due to metabolic rate the thermal comfort get affected highly. Government school buildings do not use cooling system; therefore the results of the research work will be useful to find the natural way to enhance thermal comfort. The aim of study is to conduct a field study in government school buildings located at Raipur (21.2514° N, 81.6296° E), India, to investigate the thermal comfort based on PMV–PPD model and to evaluate the cooling load of school building. A questionnaire survey and field study data is collected for the school building, from the survey response, it is to be concluded that occupants feels slightly cool, warm and cool for the season; monsoon, summer and winter, respectively. Slightly variation in PMV value of experimental data and questionnaire data is reported, due to the thermal adjustment of occupant according to the environment.

Learning occupants’ indoor comfort temperature through a Bayesian inference approach for office buildings in United States

A carefully chosen indoor comfort temperature as the thermostat set-point is the key to optimizing building energy use and occupants’ comfort and well-being. ASHRAE Standard 55 or ISO Standard 7730 uses the PMV-PPD model or the adaptive comfort model that is based on small-sized or outdated sample data, which raises questions on whether and how ranges of occupant thermal comfort temperature should be revised using more recent larger-sized dataset. In this paper, a Bayesian inference approach has been used to derive new occupant comfort temperature ranges for U.S. office buildings using the ASHRAE Global Thermal Comfort Database. Bayesian inference can express uncertainty and incorporate prior knowledge. The comfort temperatures were found to be higher and less variable at cooling mode than at heating mode, and with significant overlapped variation ranges between the two modes. The comfort operative temperature of occupants varies between 21.9 and 25.4 °C for the cooling mode with a median of 23.7 °C, and between 20.5 and 24.9 °C for the heating mode with a median of 22.7 °C. These comfort temperature ranges are similar to the current ASHRAE standard 55 in the heating mode but 2–3 °C lower in the cooling mode. The results of this study could be adopted as more realistic thermostat set-points in building design, operation, control optimization, energy performance analysis, and policymaking.

Estimation of energy savings potential through hydraulic balancing of heating systems in buildings

Hydraulic balancing of heat distribution systems in buildings plays an important role in improving indoor thermal conditions as well as reducing energy consumption for space heating. Building energy models typically do not incorporate thermal comfort while it is essential for hydraulic balancing to do so. This paper proposes a methodology that assesses the impact of hydraulic balancing on the energy savings potential while ensuring thermal comfort of the occupants. The proposed methodology is composed of three parts, i.e. characterization, estimation and scenario analysis. First, we characterize indoor air temperature level of each individual flat in buildings belonging to the same central heating system to examine temperature variation among the flats. Second, thermal comfort under given indoor conditions is predicted by means of the PMV-PPD model (predicted mean vote-predicted percentage of dissatisfied) and the optimal indoor air temperature where most of the occupants feel comfortable is estimated. We calculate potential energy savings assuming that hydraulic balancing ensures ideal conditions where the indoor air temperature stays at the optimal level, thereby maintaining thermal acceptance of at least 94% of the occupants. A scenario analysis covering different types of occupant behavior allows to estimate the energy savings potential under different conditions. We test the applicability of the proposed methodology by applying it to a group of existing buildings in Geneva, Switzerland during the cold season. The case study demonstrates that there is an energy savings potential between 2% and 14%. We also discuss how the simulation results can guide practitioners operating hydraulic balancing programs.

Inter-personal factors affecting building occupants’ thermal tolerance at cold outdoor condition during an autumn–winter period

The study was conducted to investigate thermal adaptation and the impact of individual differences on developing thermal tolerance when the outdoor temperature falls below 10°C. The applicability of the predicted mean vote (PMV) model was investigated, too. The concept of occupant’s ‘Temperament’ was evaluated as a psychological-adaptation factor. Two main hypotheses were: (a) people with different temperaments would experience different thermal sensations and (b) the classic PMV- predicted percentage dissatisfied (PPD) model is capable of predicting the neutral sensation in heated buildings under cold outdoor temperatures. There was a direct relationship between individual temperament and clothing level as well as thermal sensation. The occupants who were assessed to have cold temperament tend to wear thicker clothes and were more sensitive to variations in indoor air temperature than others. Females with a cold temperament were more than twice as likely to be affected by indoor air temperature as those with a warm temperament. The PMV-PPD model was able to predict the mean neutral temperature in the heated buildings even when the outdoor temperature fell below 10°C. However, when occupants were able to control high indoor temperature, the percentage of true prediction of actual mean votes by the adaptive thermal heat balance model was more than that by the classic PMV model.

Evaluation of thermal comfort criteria of an active chilled beam system in tropical climate: A comparative study

Air-conditioning systems are employed to provide thermal comfort inside buildings. Therefore, several air-conditioning and mechanical ventilation (ACMV) systems have been tested and applied in different climates. Chilled beam systems are a new addition to it and have been in the application in Europe and North America since last two decades. In the present study, comparative performance of active chilled beam (ACB) system with conventional fan coil unit (FCU) system has been appraised in regards to thermal comfort for the tropical region of Singapore. Experiments were carried out in a simulated office building with approximately 80% glazed area under real environmental conditions. Room air temperature, air velocity, mean radiant temperature (MRT) and relative humidity which are important thermal comfort parameters were measured in perimeter zone inside the cells and assessed. It was perceived that the ACB system was providing acceptable thermal comfort as per the standard of SS 554. General thermal comfort has been assessed based on an index of PMV-PPD model and graphical method. With regard to the local thermal discomfort: indices of air draught, vertical air temperature difference (VATD) and radiant temperature asymmetry have also been evaluated. The entrance of solar radiation through window façade may have a significant impact on the asymmetry of the radiant field and can enhance thermal discomfort of the occupants. Therefore, in the study radiant temperature asymmetry has been calculated extensively. The results show that ACB system yields satisfactory thermal environment as per ISO 7730 standard and sometimes performs even better than conventional FCU system.

A thermal comfort model for the non-uniform thermal environments

This study aims to build models to predict the overall thermal comfort in the non-uniform thermal environments. Nine non-uniform thermal conditions with the locally supplied airflows were created with 24 healthy subjects recruited. Subjects’ thermal sensation as well as thermal comfort on the whole body and the body parts were surveyed. The overall percentage of dissatisfied (PD) was higher than the predicted percentage of dissatisfied (PPD) by the PMV-PPD model when the thermal non-uniformity exceeded a certain level. The deviation between PD and PPD increased along with the local percentage of dissatisfied, which rised with the thermal non-uniformity level. The overall percentages of dissatisfied depended on the local percentage of dissatisfied as well as the overall thermal sensation vote. A PD model was therefore proposed by considering both the overall thermal sensation vote and the local percentage of dissatisfied on the mainly exposed body part. As well, another PD model was developed by averaging the max. and the min. local percentage of dissatisfied. The PD models were verified to be credible, they are capable of predicting the occupants’ percentage of dissatisfied in the non-uniform thermal environment by combining the previous thermal regulation model and the thermal sensation model.

A PMV-PPD model based study of thermal comfort in Low-Income Group house in Chhattisgarh

People tend to maintain symmetry between comfort and economy while choosing essential commodities needed in their life. Families buy a house which may offer comfort condition, but at minimum in term expenses of energy throughout a life. Thus, it is most important to erect a house to provide comfortable condition and moderate the lifetime expenditure by saving energy consumption. Sensation of thermal comfort varies from people to people, even in an identical environment. To minimize the consumption of energy of building, cost of consumed energy and to provide a comfortable house, thermal comfort analysis in indoor environments have attracted many researchers. Fanger’s Predicted Mean Vote (PMV) - Predicted Percentage of Dissatisfied (PPD) model is widely accepted theory for assessment of building indoor thermal conditions. In the present work, thermal comfort of an LIG house in Chhattisgarh region of India has been analyzed based on PMV-PPD method for months representing three different seasons in a year i.e. May, September and December representing summer, post monsoon and winter respectively. Cooling, heating and actual energy load of LIG house has been calculated and reported for the above mentioned months. From analysis it is concluded that inhabitants are comfortable only during the winter.