0-100℃濕空氣密度計算方式之探討

Density Determination for Moist Air at Temperature Range between 0 and 100℃

10.7005/JOSH.200812.0401

王順志(Shun-Chih Wang)；張振平(Cheng-Ping Chang)

濕空氣密度 ； CIPM-2007方法 ； 現場校正 ； Moist air density ； CIPM-2007 ； On-site calibration

勞工安全衛生研究季刊

16卷4期（2008 / 12 / 01）

401 - 414

繁體中文

勞工作業場所的空氣品質監測工作之中，常有採樣空氣與監測通風設施性能的必要。有些通風與空氣品質監測儀器，例如空氣採樣泵、皮托管、熱線風速計、壓差式風量計等，其性能皆受空氣密度大小的影響，若能快速取得精密的濕空氣密度，則有助於工業衛生專業人員實施現場儀器校正。從平坦乾熱的臺灣西南部平原，一路上升到涼爽多濕的南投高地，濕空氣的物理性質存在差異超過8%的情形十分常見。 爲了方便世界各國的大氣科學研究者採用共同的標準來衡量濕空氣密度，國際度量衡標準局於1981年提出CIPM-81標準計算方法。這個僅適用於氣溫攝氏15到27℃的CIPM-81方法是由一組公式構成，但在過去27年間，不斷有新的科學數據引進修正CIPM-81方法，國際度量衡標準局也順應這些新發現，在相同的氣溫區間內陸續推出CIPM81/91、CIMP-2007等更新版本。由於部分監測位置的空氣可能爲高溫高濕的氣體，爲了方便工業衛生專業人員實施直讀式儀器的的現場校正，本篇蒐集不同學術領域的最新期刊文獻與實驗數據，重新推導補全濕空氣密度的精密評估方法，將適用的溫度範圍擴大到攝氏0-100℃（此氣溫範圍涵蓋大部分空氣監測儀器的工作需求），並與CIPM-2007方法，已知的其他標準濕空氣狀態、已知的最新期刊實驗數據作比對。

Air sampling and performance monitoring for industrial ventilation systems are ordinary procedures to ensure acceptable air quality for workplaces. Since some instruments for air quality monitoring, such as air sampling pumps, Pitot tubes, hot-wire anemometers, and Venturi airflow rate meters, are sensitive to magnitude of air density, a feasible method for determination of moist air density is important to industrial hygienists to perform on-site instrument calibration. Properties of moist air may change dramatically when one travels from hot, dry south-west plain to cool, soggy central highlands on Taiwan Island. More than 8% difference of moist air density is often observed between a coastal city and a highland industrial park. Because of great scientific need of a standard method for accurate and quick determination of moist air density, International Bureau of Weights and Measures (BIPM) proposed CIPM-81 in 1981. The CIPM-81 method, which is for temperature range between 15 and 27ºC only, has been modified by many scientists in past 27 years. In this study, the latest version of standard method for determination of moist air density, CIPM-2007, is revised to achieve highest-possible accuracy and to accommodate a wider temperature range between 0 and 100℃, which is the working temperature range for most of environmental monitoring instruments. With revised method proposed by this study, an industrial hygienist can quickly determine moist air density in a workplace and perform accurate on-site calibration to some direct-reading instruments. Results from this study are compared with CIPM-2007 method, existing standard conditions of atmosphere and other experiment results.

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