Browsing by Subject "ilmanvaihto"

In Finland it´s important to have properly working ventilation system. Harmful gases and moisture should be removed from cowshed in winter while keeping indoor temperature in acceptable level for animals. In summer the main criterion for ventilation is removing extra heat. Working ventilation improves animal welfare and employee safety at work. The purpose of this research was to find out if it is possible to control the air inlets depending on the temperature difference. The aim was that indoor temperature doesn´t fall below 12 °C or rise over 14 °C. Results were compared with another control system which is adjusting air inlets depending on the rotation speed of exhaust fans. Research was conducted in the cowshed of Viikki Research Farm which has under pressure ventilation system. Measurable quantities were carbon dioxide, moisture and temperatures. Adjusting of air inlets was carried out using programmable logic control. Indoor temperature remained stable in both control systems and content of carbon dioxide fell down. Indoor temperature remained between the target values better with the system operating based on temperature difference. With the other system the indoor temperature fell noticeably below 12 °C even though air inlet vents were closed on another side of cowshed. If both sides of air inlets would have been-used, the indoor temperature would have been even lower. Average temperatures were near 12 °C in both control systems but standard deviation was higher in the original system. The original control system was too effective because indoor temperature was near 9 °C when there was cold outside. With new adjusting system indoor temperature was near 12 °C if both sides of air inlets were used. If outdoor temperature was near 0 °C or higher and only one side of air inlets were use it was impossible to get enough fresh air in the cowshed. Therefore, if indoor temperature is higher than the target temperature then the content of carbon dioxide is also on high level. R e sults of control systems aren´t directly comparable because weather was colder when measurements of original control system were done. Nevertheless it can be assumed that new control system would work also in colder weather.