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Flow Characteristics of the Dynamic “EPA Flux Chamber”

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2011 Louisville, Kentucky, August 7-10, 2011  1111096.(doi:10.13031/2013.38103)
Authors:   Bryan L Woodbury, David B Parker, Roger A Eigenberg, Mindy J Spiehs
Keywords:   break-through curves, flux chamber, greenhouse gas, emissions,

A dynamic flux chamber, commonly referred as the EPA chamber, is one method that has been adapted to investigate spatial gas emission on feedlot surfaces. However, the flow characteristics within the chamber have not been evaluated to determine if it can be effectively used outside of its original design specifications. Understanding the chamber flow characteristics will improve the proper application for determining the spatial distribution of emissions from feedlot surfaces. A series of pulse tracer studies at flow rates of 2.5, 5 and 7.5 L min-1 with and without an internal mixing fan were performed to determine tracer break-through curve (BTC) characteristics. Tracer BTCs indicated ideally mixed conditions in the chamber at the evaluated flow rates. However, deviations in the actual retention times from the calculated retention times were greater at the 2.5 and 5.0 L min-1 flow rate when the mixing fan was not used. It appears the deviation was driven by the tailing of the BTCs. The tailing was not a problem when the flow rate was increased to 7.5 L min-1 or when the mixing fan was used. This tailing is not expected to limit the effectiveness of the chamber for evaluating treatment effects on spatial gas emission from feedlot surfaces, but others have shown that low flow rates inhibit the overall emission rate from flux chambers.

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