Evaluation And Research On Thermal Comfort Of Positive Pressure Cab Of Loader

With the continuous development of economy,wheel loaders have been widely used in construction machinery,and people’s requirements for thermal comfort of cab have become higher and higher.Due to the narrow space and complex internal structure of the cab,the indoor air distribution is often irregular.The air temperature and speed directly affect people’s thermal comfort.Therefore,in order to improve the thermal comfort of the cab,the air temperature,flow rate,freshness and positive pressure in the cab are adjusted to the most comfortable range of the human body,so as to reduce the driver’s fatigue and further improve the operation efficiency.Based on the basic theory of CFD,this paper studies the flow field in the cab of loader by using the method of test and numerical simulation,and analyzes the influence of different air supply parameters on the thermal environment of the cab.Firstly,the three-dimensional software is used to establish the loader cab model,set the boundary conditions for numerical solution,and verify the accuracy and reliability of the model through simulation test.Then based on the built cab model,the temperature field,velocity field and pressure field under the heating condition of the cab are calculated.By selecting the typical cross-sectional cloud map,the influence of the flow field change on the cab thermal environment and indoor positive pressure is analyzed.The thermal comfort of the cab is evaluated by using PMV-PPD,blowing sensation and air age index,which can realize the visual processing of the cab thermal environment.Finally,based on the condition that the loader cab maintains positive pressure,select reasonable air supply parameters,analyze the internal flow field and thermal comfort under the condition of air conditioning and refrigeration,and study the influence of indoor air distribution on drivers and passengers.The results show that under the heating condition,the air supply speed is in the range of7.5～8.5 m/s,the PMV value of human body surface is about-0.6～+0.8,the maximum PPD is16%,and the indoor positive pressure is maintained at 51.5 Pa.in this environment,the human body is thermally comfortable;Under the refrigeration condition,the PMV value of human body surface is between +0.2 and +1.2,and the PPD value ranges from 21% to 24%,while the average PMV value of human body surface is about +0.78 and the average PPD value is about 22.5%.Human thermal comfort is in a comfortable and acceptable range.