Study on Thermal Comfort under Non-uniform Environment with Chest Exposing to the Local Airflow
|School||Shanghai Jiaotong University|
|Course||Refrigeration and Cryogenic Engineering|
|Keywords||task ambient air conditioning non-uniform environment thermalsensation thermal comfort draft|
Task ambient air conditioning has potentials to save energy and improve air qualityand thermal comfort. However, there are many knowledge gap needed to be solved beforeit can be used. Thermal comfort characteristic is one of the important issues which affectthe performance of the task ambient air conditioning. Many questions needs to beanswered, e.g. the optimization of the type, the acceptable range of the ambient airtemperature, the suitable local supply air temperature, velocity et al. Besides, the theoriesand principles built under the uniform environment are not applicable to the task ambientair conditioning environment, which is non-uniform and transient. For example, thePMV-PPD model, which is widely used in mixing ventilation environment, needs to bereevaluated. The evaluation and prediction on draft under the task ambient airconditioning was also an important issue. Therefore, the basic researches on thermalcomfort in task ambient air conditioning are needed.Based on the above questions, the main contents and results of this study include:1. Experimental study on thermal comfort under the non-uniform environment withchest exposing to the local airflow was carried out. Under the ambient temperature of28°C, overall thermal comfort can be improved by local cooling. The range of the local supplyair temperature, velocity and the size of the vent was suggested.2. The correlation between the overall thermal sensation and overall thermal comfortunder non-uniform environment was different from that under uniform environments. Thephenomenon was explained by analyzing the relationship between the local supply airflowparameters, the local thermal sensation and comfort, and overall thermal sensation and comfort. Overall thermal comfort was not only related to overall thermal sensation, but alsorelated to the local thermal sensation, thermal comfort and draft.3. Mean skin temperature calculation method was suggested considering the effect ofthe local airflow and the physiological difference between the different body parts. Basedon this principle,14points method was built to calculate the mean skin temperature undernon-uniform environment with chest exposure to the local airflow.4. The overall thermal sensation was linearly related to the mean skin temperatureunder the steady state under the present research condition. Overall thermal sensation waslinearly related to the mean skin temperature and its change rate. The correlations of theabove relationships were regressed. Besides, correlations between the overall thermalsensation and the skin temperature on the middle of the chest and its change rate wasobtained to predict overall thermal sensation under the non-uniform envieonment withchest exposing to the local airflow.5. A serious of correlations were built to predict the local thermal sensation and thelocal thermal comfort when the overall thermal sensation was nearly thermal neutral. Thecorrelation between the local thermal sensation and the local skin temperature was linear.The correlation between the local thermal comfort and the local thermal sensation wasquadratic. The correlations were obtained to predict the thermal sensation and the thermalcomfort at the middle of the chest, anterior upper arm, anterior forearm and anterior neck,respectively.6. The effect of turbulence intensity on draft was studied by experiments. Turbulenceintensity affects draft because it affects the local skin temperature. Skin temperature canbe considered as a parameter to predict draft rate. Furthermore, the draft rate at the chestwas correlated to the local skin temperature, the local thermal sensation and the localthermal comfort, in order to predict human’s responses to draft when the chest exposed tothe local airflow.7. A model to predict draft rate was built considering exposure time, airflowtemperature, velocity and turbulence intensity. Besides, a correlation between draft voteand draft rate was proposed. The suggested range of the local supply airflow parameters and the correlationspredicting the thermal sensation, comfort and draft can be referenced by the designer ofthe task ambient air conditioning.