Evaluation And Analysis Of Thermal Environment In Vehicle And Research On Passenger Thermal Comfort Experiment

With the development of the city and the improvement of living standards,people spend more and more time in the vehicles,so the passengers' thermal comfort is getting more and more attention.Because the comfortable thermal environment in the vehicle not only allows the driver to reduce the pressure,but also avoids fogging to ensure a good line of sight,which helps to drive safely.In addition,improving passenger comfort contributes to energy conservation and emission reduction,so it is necessary to develop a comprehensive experimental method to quantitatively measure passenger thermal comfort.After reviewing the domestic and international literature on the thermal environment of the car and the thermal comfort of the occupants,the current situation and shortcomings of the current evaluation methods are summarized and analyzed.It is found that most of the evaluation methods currently used are too complicated and expensive,so it is necessary to use an evaluation method that is easy to operate and relatively inexpensive.As a thermal comfort evaluation index widely used in buildings,PMV-PPD has been included in international standards since the 1980 s,and its evaluation system is very mature and widely used in buildings around the world.Since the environment inside the vehicle is very different from the environment inside the building,the PMV-PPD cannot be directly applied to the thermal comfort assessment of the interior environment and needs to be verified and corrected.Firstly,the target vehicle was subjected to rapid summer cooling experiment in the wind tunnel laboratory,and the performance of the vehicle air conditioner was investigated by using two indexes of characteristic temperature and cooling rate.Then,through the measured environmental parameters of the vehicle,the characteristics of the thermal environment inside the vehicle are analyzed.It is found that the temperature field and the flow field in the vehicle are unevenly distributed.In the warming phase,a large vertical temperature difference will appear in the vehicle,and during the cooling process,the air temperature in the front and rear rows will have a deviation of about 4 °C,and the wind speed in the front and rear rows will also have a gap of about 0.8 m/s.Then,using the summer steady-state experiments conducted in the outdoor and wind tunnels,it is found that there is still a certain temperature gradient in the vehicle through the measurement of the thermal environment inside the vehicle.The local thermal comfort of the head,hands and feet was analyzed using the local equivalent temperature,and it was found that only the hand was always in a comfortable area.Comparing the average PMV and the PMV calculated by the average equivalent temperature with the overall thermal sensation,it was found that the average PMV can well evaluate the overall thermal sensation.For the PMV at the three measurement points,the PMV of the head measurement point is closest to the average PMV and the correlation is best,so we can correct the PMV of the head measurement point with the overall thermal sensation.Through the comparison of steady-state experimental data,it is found that the predicted value of the PMV model is higher than the actual voting value,indicating that the warmth felt by the passengers is not as serious as the PMV predicted.However,there was no significant difference between the two models in predicting the neutral thermal sensation,and the optimal operating temperature was 27.8 °C.Since the interior environment of the car is more severe than the built environment,the passenger's expectation of the thermal comfort of the vehicle is lower than that of the building,resulting in a PMV forecast that is usually higher than the subjective vote.Therefore,the concept of "expectation factor" is proposed to modify the PMV model to truly reflect the passenger's thermal sensation.It can be concluded from the calculation that the expectation factor of the thermal environment in the vehicle is 0.63,and the limit of the passenger's tolerance to the thermal environment inside the car is +5,so the applicable range of the extended PMV model is(-5,+ 5).Finally,the relationship between the average of thermal sensation voting and environmental parameters was established by using multiple regression fitting method,and the influence of each parameter on thermal sensation was analyzed.Finally,the comfort zone range of operating temperature and air velocity was obtained.In this paper,a preliminary discussion on the evaluation method of the occupant's thermal comfort is carried out.The thermal comfort of the occupants in the vehicle is quantitatively analyzed by examining different indicators under transient and steady-state conditions,thus enriching the thermal comfort of the occupants.Research methods and have strong practical value.