Predicted Mean Vote of Subway Car Environment Based on Machine Learning

The thermal comfort of passengers in the carriage cannot be ignored.Thus,this research aims to establish a prediction model for the thermal comfort of the internal environment of a subway car and find the optimal input combination in establishing the prediction model of the predicted mean vote(PMV)index.Data-driven modeling utilizes data from experiments and questionnaires conducted in Nanjing Metro.Support vector machine(SVM),decision tree(DT),random forest(RF),and logistic regression(LR)were used to build four models.This research aims to select the most appropriate input variables for the predictive model.All possible combinations of 11 input variables were used to determine the most accurate model,with variable selection for each model comprising 102350 iterations.In the PMV prediction,the RF model was the best when using the correlation coefficients square(R2)as the evaluation indicator(R^(2):0.7680,mean squared error(MSE):0.2868).The variables include clothing temperature(CT),convective heat transfer coefficient between the surface of the human body and the environment(CHTC),black bulb temperature(BBT),and thermal resistance of clothes(TROC).The RF model with MSE as the evaluation index also had the highest accuracy(R^(2):0.7676,MSE:0.2836).The variables include clothing surface area coefficient(CSAC),CT,BBT,and air velocity(AV).The results show that the RF model can efficiently predict the PMV of the subway car environment.

Effect of horizontal radiant temperature asymmetry on thermal comfort and environmental parameters in a warm sitting area

Taiwan is a hot and humid place;in addition,the sunlight is strong and sufficient,the naturally ventilated classrooms have large-area windows for better lighting and ventilation in Taiwan.However,subjects sitting close to the large-area windows will encounter the problem of radiant temperature asymmetry,which may cause local thermal discomfort during summer.Hence,this paper is to investigate the influence of horizontal radiant temperature asymmetry on the thermal sensation of subjects and the correlative variation of environmental parameters in a warm sitting area.The evaluation results show that the predicted mean vote(PMV)index can be used to predict the overall thermal sensation of a group of sedentary subjects in a warm environment with horizontal radiant temperature asymmetry;even subjects feel local discomfort on exposed parts of their body.The measured results of environmental parameters indicate that the averaged radiant temperature difference is about 4.6 ℃ from right shoulder to left shoulder;the temperature difference does not only cause correlative variations of other environmental parameters,but also result in thermal discomfort on the right cheeks and forearms of subjects in the warm sitting area.

Energy Efficient Thermal Comfort Control for Residential Building Based on Nonlinear EMPC

For purpose of achieving the desired thermal comfort level and reducing the economic cost of maintaining the thermal comfort of green residential building,an energy efficient thermal comfort control strategy based on economic model predictive control(EMPC)for green residential buildings which adopts household heat metering is presented.Firstly,the nonlinear thermal comfort model of heating room is analyzed and obtained.A practical nonlinear thermal comfort prediction model is obtained by using an approximation method.Then,the economic cost function and optimization problem of energy-saving under the necessary thermal comfort requirements are constructed to realize the optimal economic performance of the dynamic process.The energy efficient thermal comfort MPC(EETCMPC)is designed.Finally,the comparison and analysis between EETCMPC and Double-layer Model Predictive Control(DMPC)is simulated.The simulation results reveal that when the clothing insulation is typical,the energy efficiency of EETCMPC is 8.9%and 11.6%,respectively,in the two simulation scenarios.When the clothing insulation varies with temperature,the energy efficiency of EETCMPC is 7.29%and 9.15%,respectively,and the total energy consumption is reduced by about 1.65%and 14.6%,respectively,compared with the typical clothing insulation.The economic performance is improved in the thermal comfort dynamic process of heating room.

Thermal performance of domed roof in air-conditioned spaces

Due to their thermal performance,domed roofs are one of the passive solutions that affect energy consumption in buildings.The thermal performance of domed roofs has been investigated in many naturally ventilated spaces.However,few studies have discussed their performance in conditioned spaces.Therefore,this study introduces a computational comparison between domed and flat roofs to investigate their impact on thermal comfort inside a conditioned mosque.At an earlier stage,field measurements were carried out inside a Bahraini mosque to acquire its indoor air conditions during the summer period of 2021,in addition to validating the computational model.The findings of this study confirm that,under mechanical cooling conditions,the flat roof offers a lower indoor temperature than the domed roof by 0.4℃and 0.1℃for open and closed doors,respectively.Similarly,the air velocity is lower by approximately 0.01 m/s for both door modes.The overall PMV values of the flat roof are also lower by 0.07 and 0.01,while the PPD values are lower by 0.20,and 0.34 for open and closed doors,respectively.Based on these small differences,it can be concluded that the thermal performance of both roofing systems behaves equally in conditioned spaces.However,the air patterns are substantially different,the overall thermal performance is similar.This similarity drives building designers to rethink the thermal performance of the domed roofs in air-conditioned spaces with such a hot climate,regardless of their aesthetic and acoustical behaviour.

Residential building performance analysis at near extreme weather conditions in Hong Kong through a thermal-comfort-based strategy

The precise building performance assessment of residential housings in subtropical regions is usually more difficult than that for the commercial premises due to the much more complicated behavior of the occupants with regard to the change in indoor temperature.The conventional use of a fixed schedule for window opening,clothing insulation and cooling equipment operation cannot reflect the real situation when the occupants respond to the change in thermal comfort,thus affecting the appropriateness of the assessment results.To rectify the situation,a new modeling strategy in which the modification of the various operation schedules was based on the calculated thermal comfort(TC),was developed in this study.With this new TC-based strategy,the realistic building performances under different cooling provision scenarios applied to a high-rise residential building under the near extreme weather conditions were investigated and compared.It was found that sole provision of ventilation fans could not meet the zone thermal comfort by over 68%of the time,and air-conditioning was essential.The optimal use of ventilation fans for cooling could only help reduce the total cooling energy demand by less than 12%at best which could only be realistically evaluated by adopting the present strategy.Parametric studies were conducted which revealed that some design factors could offer opportunities for reducing the total cooling energy under the near extreme weather conditions.

A Novel Combined Trombe Wall System for Village Houses in Cold Regions of China

Trombe walls have significant energy-saving features and are therefore of great interest to researchers.However,additional research about the Trombe wall is needed to reduce indoor temperature fluctuations and to improve thermal behavior under different climatic conditions.A new Trombe wall system was proposed which uses Venetian blinds and a basement.The field tests were conducted to compare the thermal performance of four types of rooms:(ⅰ)no Trombe wall(control),(ⅱ)classical Trombe wall(TW),(ⅲ)Trombe wall with Venetian blinds(TW+VB),and(ⅳ)Trombe wall with Venetian blinds and a basement(TW+VB+B).The field measurements were conducted during the winter near Shihezi City in northwest China.The objective of this study was(ⅰ)to evaluate the thermal performance of a novel Trombe wall system under different operation conditions,and(ⅱ)to confirm the optimal angle of Venetian blinds during the heating period.The results demonstrated that the TW+VB+B system effectively reduced indoor temperature fluctuations after sunset.Furthermore,during the daytime,the average air temperatures in the test rooms were 13.6℃higher in the TW+VB+B system than in the control.The average temperature at the air outlet in the TW+VB+B system was 4.9℃higher than that in the TW+VB system during the daytime,and the average predicted mean vote(PMV)of the test room was 1.02 units greater in the TW+VB+B system than in the control.The thermal efficiency remains in the range of 40%-65%when the Venetian blind angle was set at 45°.In conclusion,the experiment results showed that the TW+VB+B system can not only reduce indoor temperature fluctuations but also improve thermal performance in winter.Both the heating energy consumption in buildings and pollutants emission in the environment were lessened through the application of this passive solar energy-saving technology.Therefore,this can provide valuable insights for improving the thermal performance of the novel Trombe Wall system in such village houses.

The effect of Urban Heat Island mitigation strategies on outdoor human thermal comfort in the city of Baghdad

Todays,most Iraqi cities suffer from extremely hot-dry climate for long periods throughout the year.However,most urban patterns that exist inside these cities are not suitable for this harsh conditions and lead to an increase in the value of the Urban Heat Island(UHI)index.Consequently,this will increase outdoor human thermal discomfort as well as energy consumption and air pollution in cities.This study attempts to evaluate the effect of UHI mitigation strategies on outdoor human thermal comfort in three different common types of urban patterns in the biggest and most populated city in Iraq,Baghdad.Three different mitigation strategies are used here-vegetation,cool materials,and urban geometry-to build 18 different scenarios.Three-dimensional numerical software ENVI-met 4.2 is utilised to analyse and assess the studied parameters.The input data for simulations process are based on two meteorological stations in Baghdad:Iraqi Meteorological Organization&Seismology,and Iraqi Agrometeorological Network.All measurements are taken in a pedestrian walkway.The results of different scenarios are compared based on their effect on human thermal comfort.Outdoor thermal comfort is assessed according to Predicted Mean Vote index,as mentioned in ISO 7730 standard.This study provides a better understanding of the role of UHI mitigation strategies on human thermal comfort in the outdoor spaces of Baghdad’s residential neighbourhoods.This can help generate guidelines of urban design and planning practices for better thermal performance in hot and dry cities.