The parameters of ventilation system in uninsulated cowshed

Abstract

In Baltic states the construction of the uninsulated cowsheds increased. The natural ventilation system is mostly installed. The required area of the opening inversely proportional to the speed of the air movement that forms there. There are many methods for calculation the speed of the air movement in the openings and natural ventilation systems parameters. But the results are when calculation according to the warious methodics. The methodics of calculation of the natural ventilation systems parameters, relating the system parameters with the criterion, characterising pollution of the inside air, and evaluating thermal buoyancy and wind pressure, solar irradiance, conditions to avoid condensation the water vapour on the inner surface of external walls and roof has been developed. The suitability of the methodics was testified under experimentally natural exploitation conditions. An experiment has been carried out in a closed uninsulated cowshed with loose housing system for 200 dairy cows the dimensions of 72x21 m. Clean air flows in through the gaps at the top of longitudinal walls and contaminated air is removed through the gap of the ridge. The distance between air inlets and outlets is 3,0 m. The experimentally value of the air speed in outlets was (1,1±102) m/s (p<0.05) and calculation value-1.0 m/s, when wind speed was-2.4 m/s, and difference between indoor and outdoor air temperatures-2,6º C. When selecting parameters of uninsulated cowshed ventilation system, the calculated value of indoor and outdoor temperature difference is 3º C. Recommendation for ventilation rate per dairy cow in summer 610 m³/h, and in winter-550m³/h.