Predicted Mean Vote Index Research Articles

Thermal Comfort Assessment: A Case Study at Malaysian Automotive Industry

Problem statement: Thermal comfort has a great influence on the productivity and satisfaction of indoor building occupants. The exposure to excessive heat during work may cause discomfort and contributed to low productivity among workers. Malaysia known with its hot and humid weather where in most of the survey study published indicated that workers in Malaysia automotive industries had exposed to excessive temperature while working. The study investigated the thermal comfort level experienced by workers at Malaysian automotive industry. Approach: The study had been conducted at one automotive parts assembly factory in Malaysia. The human subjects for the study constitute operators at tire receiving section of the factory. The environment examined was the relative humidity (%), WBGT, air temperature and radiant temperature (°C) of the surrounding workstation area. The environmental factors were measured using Babuc apparatus, which is capable to measure simultaneously those mentioned environmental factors. The time series data of fluctuating level of factors were plotted to identify the significant changes of factors. Then thermal comfort of the workers was assessed by using ASHRAE thermal sensation scale by using Predicted Mean Vote (PMV). Further Predicted Percentage Dissatisfied (PPD) was used to estimate the thermal comfort satisfaction of the occupant. Finally the PPD versus PMV were plotted to present the thermal comfort scenario of workers involved in related workstation. Results: The trend of relative humidity curve from the graph also indicated the increasing level of discomfort. The radiant temperature observed seems consistent during the study while there was decreasing of WBGT start from afternoon due to the rain. The study revealed that the PPD value of 54% of the workers population at the workstation are likely to be satisfied with thermal comfort at this station while the PMV index from ASHRAE indicated the value 1.07-1.41. Conclusion: The empirical study from the PPD and PMV index indicated that workers working at this were influenced by the heat. The less of PPD value from 80% of the population satisfied with the thermal comfort showed the environment factors that were not good for worker while the PMV index showed the area of work is slightly warm.

Modelling and simulation of an infant’s whole body plethysmograph

In this paper, we describe a computational model dedicated to building an apnoea monitoring system for newborn babies. The proposed model is based on whole body plethysmography, which involves non-invasive measurement of lung ventilation indirectly from the pressure deflections generated when a subject breathes inside a chamber of fixed volume (Bert in C R Soc Biol Paris 20:22-23, 1868). The computational model simulates thermal and environmental flow conditions occurring in the neonate chamber, especially steady state flow with heat transfer and carbon dioxide (CO2) transport during the exhalation phase. This permits the variance of all critical parameters and the analysis of their effects on the distributions of interest. The main objective is to study thermal and air quality comfort conditions under which infants can be monitored for long-term periods. The method deploys computational fluid dynamics techniques and parametric modelling which, by allowing input parameters to be modulated, represent a more efficient and flexible analytical tool than previous experimental techniques. Simulation data reveal that the largest flow rates occur in areas near the openings with slight formation of air recirculation zones; temperature distribution shows signs of stratification, with higher temperatures than the supplied air, CO2 distribution presents acceptable air quality level and predicted mean vote index affords a relatively acceptable thermal comfort level. This analytical approach can be considered as innovative, and can find a new application in clinical infant apnoea monitoring in a way that allows determination of the optimal location for placing a sensor to detect respiration activity without any contact with the infant's body, and without any risk, in contrast to available whole body plethysmography techniques previously tested in infants (Fleming et al. in J Appl Physiol 55:1924-1931, 1983).

Neural computing thermal comfort index for HVAC systems

The primary purpose of a heating, ventilating and air conditioning (HVAC) system within a building is to make occupants comfortable. Without real time determination of human thermal comfort, it is not feasible for the HVAC system to yield controlled conditions of the air for human comfort all the time. This paper presents a practical approach to determine human thermal comfort quantitatively via neural computing. The neural network model allows real time determination of the thermal comfort index, where it is not practical to compute the conventional predicted mean vote (PMV) index itself in real time. The feed forward neural network model is proposed as an explicit function of the relation of the PMV index to accessible variables, i.e. the air temperature, wet bulb temperature, globe temperature, air velocity, clothing insulation and human activity. An experiment in an air conditioned office room was done to demonstrate the effectiveness of the proposed methodology. The results show good agreement between the thermal comfort index calculated from the neural network model in real time and those calculated from the conventional PMV model.

The control of indoor thermal comfort conditions: introducing a fuzzy adaptive controller

The control and the monitoring of indoor thermal conditions represents a pre-eminent task with the aim of ensuring suitable working and living spaces to people. Especially in industrialised countries, in fact, several rules and standards have been recently released in order of providing technicians with suitable design tools and effective indexes and parameters for the checking of the indoor microclimate. Among them, predicted mean vote (PMV) index is often adopted for assessing the thermal comfort conditions of thermal moderate environments. Unfortunately, the PMV index is characterised by non-linear features, that could determine some difficulties when monitoring and controlling HVAC equipment. In order of overcoming these problems, a fuzzy control for HVAC system is here described. It represents a new simple approach, focused on the application of an adaptive fuzzy controller that avoids the modelling of indoor and outdoor environments. After a brief description of the method, some simulation results are presented. A simplified application, referring to a room belonging to an university building, is finally reported.

Thermal bioclimatic conditions and patterns of behaviour in an urban park in Göteborg, Sweden.

People in urban areas frequently use parks for recreation and outdoor activities. Owing to the complexity of the outdoor environment, there have only been a few attempts to understand the effect of the thermal environment on people's use of outdoor spaces. This paper therefore seeks to determine the relationship between the thermal environment, park use and behavioural patterns in an urban area of Sweden. The methods used include structured interviews, unobtrusive observations of the naturally occurring behaviour and simultaneous measurements of thermal comfort variables, i.e., air temperature, air humidity, wind speed and global radiation. The thermal environment is investigated through the mean radiant temperature (Tmrt) and the predicted mean vote (PMV) index. The outcome is compared to the subjective behaviour and thermal sensation of the interviewees. It is found that the thermal environment, access and design are important factors in the use of the park. In order to continue to use the park when the thermal conditions become too cold or too hot for comfort, people improve their comfort conditions by modifying their clothing and by choosing the most supportive thermal opportunities available within the place. The study also shows that psychological aspects such as time of exposure, expectations, experience and perceived control may influence the subjective assessment. Comparison between the thermal sensation of the interviewees and the thermal sensation assessed by the PMV index indicates that steady-state models such as the PMV index may not be appropriate for the assessment of short-term outdoor thermal comfort, mainly because they are unable to analyse transient exposure.

Thermal environment effects on construction workers’ productivity

This paper reports on a research study that focused on predicting the loss of construction workers’ productivity due to thermal environment variations. The paper utilises a statistical polynomial regression analysis to establish a relationship between productivity and the predicted mean vote (PMV) thermal comfort index. In doing so, it builds upon a substantial amount of data reported in the literature regarding construction productivity and thermal environment. A set of equations reflecting the nature of the construction task being performed as well as the thermal environment are proposed to predict the degree of change in workers’ productivity, according to a change in the thermal environment. The paper also reports on an experimental investigation undertaken to validate the developed equations. Validation results indicate that the developed equations can predict productivity with a reasonable level of accuracy. Furthermore, they show that the workers’ productivity decreases as the PMV index moves away from the optimum range for all the observed tasks.

Thermal comfort based fuzzy logic controller

Most heating, ventilation and air conditioning (HVAC) control systems are considered as temperature control problems. In this work, the predicted mean vote (PMV) is used to control the indoor temperature of a space by setting it at a point where the PMV index becomes zero and the predicted percentage of persons dissatisfied (PPD) achieves a maximum threshold of 5%. This is achieved through the use of a fuzzy logic controller that takes into account a range of human comfort criteria in the formulation of the control action that should be applied to the heating system to bring the space to comfort conditions. The resulting controller is free of the set up and tuning problems that hinder conventional HVAC controllers. Simulation results show that the proposed control strategy makes it possible to maximize the indoor thermal comfort and, correspondingly, a reduction in energy use of 20% was obtained for a typical 7-day winter period when compared with conventional control.

The Effect of Diffuser's Location on Thermal Comfort Analysis with Different Air Distribution Strategies

The evaluation of various ventilation strategies for optimal ther mal comfort design in terms of predicted mean vote index was investigated. The major parameter is the inlet/outlet diffuser's locations in the occupied region. The location effects of the inlet and outlet diffusers at the ceiling/walls on thermal com fort were examined every 0 4 meter. Eight different air distribution systems includ ing single inlet-single outlet and single inlet-double outlets arrangements were studied in an indoor environment. Also, an experimental validation was conducted. The comparison results between prediction and test are quite good.

Notes on the Use of the Tables of Standard ISO 7730 for the Evaluation of the PMV Index

Standard ISO 7730, which is also known as European Standard EN-ISO 7730, provides two alternative methods for the evaluation of the predicted mean vote (PMV) index: a calculation program and a set of tables. In order to use the tables, the operative temperature must be calculated beforehand. The impres sion is given from reading the standard that for a relative humidity of 50%, the two methods are equivalent, i.e. provide the same value for PMV, from the same initial values. In this paper, examples are given showing that the two methods are not equivalent. Differences between them are analysed and a proposal made to introduce an amendment in the next revision of the stan dard.

Silicon-based thermal comfort sensing device

Based on a thermal mannequin model, we have designed and fabricated a silicon-based TCS (thermal comfort sensing) devices. The thermal comfort sensor appears to be highly sensitive to air flow and fairly sensitive to radiation, but is quite insensitive to humidity. A PMV (predicted mean vote) indicator has been fabricated using the TCS device and the experimental results in a simulated environment clearly suggest that our sensor can be utilized in air-conditioning systems as a practical means of monitoring PMV indices and of feedback control.

Thermal comfort in passive solar earth integrated rooms

Presented are the two-year temperature and relative humidity measurements in semi-underground rooms in Sendai, Japan, and one year measurements in fully earth integrated rooms in Brhlovce, Slovakia. The monthly mean and daily mean spring and summer data are shown together with Predicted Mean Vote (PMV) indices. Similar data on air temperatures were found as in the previous studies. However, the more complex evaluation of thermal comfort using PMV index helped to determine that fully earth integrated rooms without insulation and proper design of transparent constructions may be cold in spring and even summer in a temperate climate. This finding is different from previous studies, which stated that earth integrated spaces in temperate climates were comfortable on the basis of air temperatures alone. The degree of earth integration, the level of insulation of the earth in contact with construction, and the size of south oriented transparent construction were found to be the key parameters of passive solar earth shelter design and conclusions were drawn regarding their implementation in various climates for optimal control of spring and summer thermal environment.

Notes on the Use of the Tables of Standard ISO 7730 for the Evaluation of the PMV Index

Standard ISO 7730, which is also known as European Standard EN-ISO 7730, provides two alternative methods for the evaluation of the predicted mean vote (PMV) index: a calculation program and a set of tables. In order to use the tables, the operative temperature must be calculated beforehand. The impression is given from reading the standard that for a relative humidity of 50%, the two methods are equivalent, i.e. provide the same value for PMV, from the same initial values. In this paper, examples are given showing that the two methods are not equivalent. Differences between them are analysed and a proposal made to introduce an amendment in the next revision of the standard.