汽車是現代人日常生活中必不可缺少的交通工具，所以如何能讓車輛更安全、舒適、節能及人性化，就變成是車輛工程師努力的目標。由於現在對於車廂內部舒適度之考量，尚未制訂一標準格式，再加上數值模擬時受限於計算時間與電腦配備，所以較少考量到熱輻射模型，而太陽日照方面僅以等熱通量替代，並未考量到日照方位，所以本文將整合以上之參數做進一步的研究。本文將利用商業套裝軟體FLUENT針對此車廂內之熱流場進行初步分析，輻射熱交換的處理是應用P-1模型，而在太陽日照方面則利用高效率之射線追跡法(Ray Tracing)來模擬太陽射線；然後再根據由國際組織所認證(ISO7730)之舒適指標PMV與PPD理論，來撰寫舒適度判定程式，經由上述兩項之整合來提升整體車廂的舒適品質，並期望能建立一套車廂內空調系統開發之流程。結果顯示車廂內具有人體模型之原始方案，在經由熱流場與PMV舒適指標分析後，發現於人體頭部及腳部之不舒適性與車廂內熱流場之缺失，所以根據熱流場模擬結果擬定了三組改善方案。首先將增加主要入風口之風速，以改善在主駕駛腳部速度過低之問題，之後再改變其角度找出一組較合適之入風口風向，最後將搭配除霧入風口，使車廂內部獲得良好的循環以提升舒適品質。結果顯示當風速提升至3m/s時人體頭部PMV值能有效降至舒適範圍內，而主要入風口角度調整至水平向上0°~20°吹送時也解決了人體原先頭部之不舒適性，將除霧入風口之風速提升與溫度降低後，冷氣能順利到達後方並使超過90%的乘客對此環境感到滿意。所以各改善方案皆能有效的解決車廂內人體不舒適之問題，足以證明此整合系統可以有效的應用在未來車廂內空調系統的開發。

Nowadays passenger car is an important part of human activity as a daily transportation tool; therefore, safety, thermal comfort, and energy saving, are the automotive engineer’s tasks in improving the automotive technology. Because of the constraints on calculation time and computer hardware, previous numerical researches are limited and seldom using the radiation model since the evaluating standard for the thermal comfort inside a car cabin is not established yet. Most efforts select the constant heat flux to model the solar radiation while neglecting the solar ray orientation. This study intends to apply the radiation model and solar ray parameter to investigate the flow and thermal fields inside the car cabin. P-1 model and Ray Tracing model are chosen as the radiation and the solar load models to calculate the velocity and temperature fields inside a car cabin via a commercial code (FLUENT). Thereafter, a thermal comfort program is prepared based on the ISO7730 code to calculate the PMV and PPD thermal comfort index. By integrating the above efforts, a systematic procedure for evaluating air conditioner inside a car cabin can be furnished to enhance the thermal comfort quality for a passenger car. To validate this scheme, a passenger car is picked to execute both CFD and experimental investigations. A good agreement between them is found by carefully comparing these two outcomes. The numerical simulation for this car with manikins inside the cabin presents that manikin’s head and feet are not comfortable via PMV index analysis.
Three modified alternatives are set up to fix these defects. At first, the airflow velocity at main inlet is increased to improve low-velocity air stream in driver’s leg. Next, the angle of main inlet was changed to locate a better flow orientation. Finally by combining the flow from defog inlet, a good comfort quality can be achieved. In summary, CFD results show that PMV index at manikin’s head drops to the comfort range when the velocity increased up to 3 m/s. Also, the uncomfortable problem on head portion can be solved for an additional 0°~20° deflection on the air stream from main inlet. With the above three modifications, the cold air can reach the back region of the cabin easily and over 90% of passengers satisfy the thermal comfort. It is demonstrated that this systematic procedure can be utilized for evaluating and improving the thermal comfort index inside the car cabin.

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