|Brown Brandl, Tami|
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2011
Publication Date: 4/20/2011
Citation: Brown Brandl, T.M., Nienaber, J.A., Eigenberg, R.A. 2011. Temperature and humidity control in indirect calorimeter chambers. Transactions of the ASABE. 54(2):685-692.
Interpretive Summary: Indirect calorimetry is used to measure the heat and moisture production of livestock. The facility described in this paper is a modification of an original system built in the late 1970's. The paper describes a new set of animal chambers, pens, and air conditioning equipment to maintain desired temperatures and humidities. The humidity is controlled by cooling the air to the point of condensation and the condensed water is collected. The air is then heated to the desired temperature by electrical resistance heaters. Both temperature and humidity controllers are capable of operating with a constant or cyclic pattern over a 24-hr period. A stainless steel penning system was designed to collect all feces, urine, and waste water. Drinking water was delivered with a common nipple waterer within a cup to limit waste. The feeder was mounted on a load cell to allow constant monitoring of feed consumption. Pens were on wheels to give easy access to all areas of the pen for animal transport and pen cleaning. The entire calorimetry system was tested for accuracy by burning alcohol. The oxygen and carbon dioxide exchange during burning is similar to the exchange caused by an animal, and we know the exchange volumes by measuring the weight of alcohol burned. These tests verified that our system was accurate.
Technical Abstract: A three-chamber, indirect calorimeter has been a part of the Environmental Laboratory at the U.S. Meat Animal Research Center (MARC) for over 25 yr. Corrosion of the animal chambers and unreliable temperature control forced either major repairs or complete replacement. There is a strong demand for heat production measurements; therefore, a new four-chamber calorimetry system was designed and constructed. The chambers are both temperature and humidity controlled, with air handling units contained within each animal chamber to reduce air leak potential. Both temperature and humidity controllers are capable of cyclic and constant temperature patterns within a nominal range (10 to 40°C), and humidity control between 20 to 100% relative humidity. The objective of this paper is to describe the design of the chambers, heating and cooling systems, controllers with sensors, and the animal penning system. A total of 264 calorimetry runs were conducted to verify temperature and humidity control with the four calorimeter chambers. These measurements were used to test the environmental controls (dry-bulb and dew-point temperatures). A total of 14 heat production verification runs were completed on the four calorimeters to verify the indirect calorimetry system and ensure that the chambers are air tight. Environmental control on the four calorimeters was very good, small changes to the protocol could improve the overall performance of the system. The heat production verification runs showed an O2 error of less than 1.5%, and a CO2 error less than 1.0%, thus ensuring that the system is air tight and functioning correctly as an indirect calorimeter.