Study On Technique Of Airflow Field Measurement Near Heated Surfaces Based On Infrared Thermal Image

With the improvement of living standard,people are demanding higher level of indoor comfort,especially the thermal comfort in winter.The airflow field near heated surfaces of building heating terminal units has an influence on thermal environment and occupants’ thermal comfort.Because of the complicity of building environment and system form,and the limitation of measurement technologies,the researches on the characteristics and mechanism of airflow field near the heating terminal units are insufficient.The point-wise measurement technologies are intrusive to airflow field significantly,and the traditional globe-wise measurement technologies such as PIV are not capable to predict full-scale room airflow field yet.In order to solve the problems mentioned above,considering the relationship between temperature distribution of heated surface and its adjacent airflow,the principle and technique of flow velocimetry near heated surfaces based on infrared thermal image tracking is proposed in this paper.To have a further analysis of the application of this new technology,the research was carried out as follows:(1)According to the characteristics of heated surfaces and the relevant theory,the method of airflow field measurement near heated surfaces of building terminal units based on infrared thermal image tracking was preliminarily established.(2)The experiment setup was designed and built based on the theory referred before.Then the experimental method was proposed and preliminary basic experiments were carried out.(3)By comparing the results of PIV and hot wire anemometer,the applicability and feasibility of the theory of the infrared thermal image tracking was analyzed.By combining the theoretical analysis and experiments,the research was carried out on the content mentioned above.This study got the followings conclusions:The mechanism and the influencing factor of energy transfer of the heated surface was discussed by analyzing the theory and influencing factor of the thermal image tracking and establishing the energy equation of the heated surface.Analogy to the principle and process of PIV,the method of airflow field measurement near heated surfaces of building terminal units based on infrared thermal image tracking was established preliminarily,which comes out to be feasible in theory.Through the validation of the basic model comparison experiment,the method of airflow field measurement near heated surfaces of building terminal units based on infrared thermal image tracking comes out to be suitable for the measurement of the near wall airflow field under the condition of natural convection.On the contrary,the outcomes under the condition of forced convection with high velocity or small surface temperature difference needs a further examination.In order to capture the turbulent characteristics of airflow field,a huge amount of instantaneous vector field need to be processed by this method.Compared to PIV,in this method,the only instrument is thermal image camera.The method has the advantages of few instruments,simple operation,and not need for trial and error.This is another innovation of the rapidly developing infrared thermal measurement theories and related technologies in the field flow field visualization.In the later study,the reprocessing process will be perfected,which would improve the measurement efficiency of the method of airflow field measurement near heated surfaces of building terminal units based on infrared thermal image tracking.