Air exchange rate measurements in naturally ventilated dairy buildings using the tracer gas decay method with ⁸⁵Kr, compared to CO₂ mass balance and discharge coefficient methods

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• 作者：Alaa Kiwan ; Werner Berg ; Merike Fiedler ; Christian Ammon ; Manfred Gl?ser ; Hans-Joachim M¨¹ller ; Reiner Brunsch
• 刊名：Biosystems Engineering
• 出版年：2013
• 出版时间：November, 2013
• 年：2013
• 卷：116
• 期：3
• 页码：286-296
• 全文大小：1888 K

文摘

Emission fluxes from naturally ventilated cattle buildings are usually calculated as the product of gas concentrations and the air exchange rate (AER). One key issue is the measurement of the AER throughout such buildings. The aim of this study was to investigate three different methods for AER estimation in naturally ventilated dairy buildings: (1) the concentration decay of the tracer gas Krypton⁸⁵ using two different evaluation procedures, (1a) sum⁸⁵Kr, in which the impulses from all the single ⁸⁵Kr sensors are combined into one cumulative curve and (1b) ave⁸⁵Kr, which averages the AERs obtained from single ⁸⁵Kr sensors; (2) the carbon dioxide mass balance model (CO₂M); and (3) the discharge coefficient method (DCM). These three methods were compared with each other using both our own measurements and results from the literature. The comparison was statistically evaluated using analysis of variance (ANOVA). The effects of the external conditions of wind velocity and temperature and the effect of nearby buildings on the differences between the methods were predicted. The concentration decay of ⁸⁵Kr and the DCM generally produced higher AER values than the CO₂M (mean?¡À?standard error (SE), 22.8?¡À?7.2?h^?1). These differences were determined to be 8.5?¡À?3.1?h^?1 (P?=?0.007) for the sum⁸⁵Kr method and 12.9?¡À?3.1?h^?1 (P?<?0.0001) for the DCM. The concentration decay of ⁸⁵Kr can also be used to estimate higher AER ranges when the difference between the CO₂ concentrations inside and outside the building is below 200?ppmv. The sum⁸⁵Kr method is the recommended procedure for tracer decay analysis for AER estimation.