Feasibility of a Dual Cooling System for Dairy Cows in Arizona

Abstract

For many decades, systems that combine forced convection with evaporative cooling have been widely used to control temperature within greenhouses located in hot and arid regions. Evaporative cooling systems have also been proven to increase the productivity of dairy cows in arid and semi-arid regions. To enhance the capability of this kind of microclimate control operation and depending on the availability of the low-temperature groundwater source, we propose the addition of a cooling unit, placed in the bedding area where cows typically lie down. We hypothesize that direct conduction through such a mat could serve as an efficient and energy-saving cooling mechanism. To test this hypothesis, we use conjugate heat transfer analyses to examine the feasibility of dual cooling strategies. We base our test conditions on climate data typical of Arizonas summer season. As our primary purpose, we seek to determine the efficacy of using a conduction cooling system to alleviate heat stress in cows. We test systems under various ambient air conditions because differences in air temperature directly affect the proportion of cooling that can be attributed to conduction. For example, under cool air conditions (18C), conduction contributes 20 % of the cooling effect, whereas under hot air conditions (38C) the contribution increases to nearly 90%. In addition to varying air temperature, we evaluate different bedding thicknesses and heat exchanger locations. Direct contact between the cows hide and the cooling mat only contributes to cooling significantly under hot air (38 C) conditions.