由於室內場所普遍使用無外氣引入功能之冷氣來調節溫、濕度，且為節能將門窗緊閉，而忽略室內空氣持續內循環導致空氣品質不良而危害人體健康。有鑑於人們長時間處於室內外換氣不足的空調環境，因此本研究針對使用空氣循環的冷氣場所，探討並提出有效的通風改善方法，以確保室內空氣品質。
本研究選擇一個有開冷氣的狹長型公共場所作為研究對象，在不改變空間原有配置、結構及維持冷氣開啟之出回風循環的狀況下，來探討可行的通風改善方法。本研究使用計算流體力學(CFD)來模擬冷氣運轉下，室內不同人數及各種通風模式(空調直接引入外氣、開門、設置立扇、安裝進排風扇)下之流場及二氧化碳分布，並以二氧化碳濃度作為通風換氣良窳的指標，最後提出可行之維持良好室內空氣品質的通風方法。
結果顯示具有改善狹長型空間且使用內循環空調之室內外換氣效果的通風模式為：(1)空調引進新鮮外氣、(2)開啟大門(自然風速2 m/s)、(3)開啟大門(自然風速2 m/s)且設置立扇、(4)開門或關門設置六組進排風扇。開門進行自然通風雖具有引入外氣促進換氣，但其缺點在於難以掌控外氣風速及換氣量。雖然室內設置立扇可促使空氣流動無停滯感，但並無外氣引入能力，因此仍需配合開門之自然通風(風速2 m/s)才可降低二氧化碳濃度。使用機械通風之進排氣扇的風壓低，導引外氣於整個狹長室內空間的能力有限，建議加裝誘導風機協助將新鮮空氣送至室內各處。
單就技術觀點研究如何改善使用冷氣之狹長型空間的室內空氣品質，以冷氣機直接引進新鮮外氣並均勻分布於整個室內空間，為四種通風模式中最可行有效的通風方法。 Due to frequently using air conditioners without supplying outdoor air function for adjusting temperature and humidity, people often ignore the harm to health that is done by poor indoor air quality without proper air exchange. In order to protect people spending long time indoors from insufficient air exchange rate, this research aims to provide effective ventilation methods to create acceptable indoor air quality in the space with air conditioners.
A long public place was selected as the research object. Without changing the original configuration and construction of the space, many feasible methods of improving ventilation were explored while air conditioners are operating with air circulation. The Computational Fluid Dynamics (CFD) is used to simulate the flow field and the distribution of carbon dioxide in the public space with different number of people; besides, different ventilation modes are applied as follows (1)air conditioners deliver outdoor air; (2)the door is opened; (3)fans are set up; (4)intake/exhaust fans are installed. The concentration of carbon dioxide is used as an indicator of ventilation effectiveness. According to the simulation results from CFD in various ventilation scenarios, feasible ventilation methods are proposed to maintain good indoor air quality in this study.
The result shows that the following ventilation modes are effective in improving indoor and outdoor air exchange in the long public space with air conditioning: (1)outdoor fresh air is sent indoors directly through air conditioners; (2)the door is opened (natural wind speed 2 m/s); (3)the door is opened (natural wind speed = 2 m/s) and fans are set up; (4)six sets of intake/exhaust fans are installed whether the door is opened or not.Opening the door intakes outdoor air, and then promotes air exchange with natural ventilation. Nevertheless, both outdoor wind speeds and air exchange rates are unpredictable factors. Setting up fans can facilitate indoor air flow; however, fans cannot intake outdoor air. Therefore, we should set up fans and simultaneously open the door to reduce the concentration of carbon dioxide. The efficiency of the intake/exhaust fans is limited because they only generate low wind pressure, which fails to fully introduce outdoor air to the whole space. To improve ventilation, induced fans are recommended to be applied in the long space while using intake/exhaust fans.
To improve the indoor air quality in long spaces with air conditioning, we recommend that fresh outdoor air is sent directly through air conditioners and distributed to the whole indoor space uniformly. In conclusion, this is the most feasible and effective ventilation method from technical point of view.
