Potencial de redução do estresse térmico em climas quentes e secos com a utilização de sistemas de resfriamento evaporativo do ar.

Abstract

This research has the objective to analyze the thermal stress reduction on dairy cows production using evaporative cooling systems. The Temperature and Humidity Index (THI) was used to analyze the potential of thermal stress reduction on Alentejo/Portugal region characterized by high temperatures and low relative humidity. The hourly climatic data from 2002 to 2004 were used and obtained from Évora Geophysics Center (CGE) database and from the Institute of Agrarian and Mediterranean Science (ICAM). The meteorological station was situated in Herdade da Mitra - Valverde. These data were used to calculate the THI according to NWSCR (1976) equation: THI = 0,72 Tw + 0,72 Tbs + 40,6. It was considered 80% efficiency for the evaporative cooling system, LUCAS et al. (2000). The results showed a great influence of the evaporative cooling system on the number of hours above the thermoneutral zone. The reduction was 100%, 99%, 80% e 39% on the number of annual hours of THI classes emergency, danger, alert with losses and alert, respectively, comparing to environment with no climatization.