Abstract
Drying grass fodder in Europe’s Alpine countries is becoming increasingly important due to positive effects on the fatty acid composition of milk. A proper approach and technology of fodder drying can raise its quality to the level of grass silage. In principle, drying fodder means extracting water from fodder by means of ventilation – the air, the key to the speed of drying. Besides low relative air humidity, its flow rate through the fodder is also important. In the literature, the lower- and upper-bound limits of air flow rates can be found, with a difference of 85 % between the two. The article describes a test, measuring energy consumption and the efficiency of drying at a low air flow, often used in practice, and a high air flow. It was found that a high air flow results in 38 % higher energy consumption per kilogramme of extracted water, compared to a low air flow. The executed test has proved that drying at a higher air flow will not have a proportionally greater effect.
Highlights
Vpliv pretoka zraka na sušenje krme na sušilnih napravah Izvleček: V alpskih državah Evrope sušenje krme s travinja postaja vedno bolj pomembno zaradi ugotovljenih pozitivnih učinkov na maščobno kislinsko sestavo mleka
It was found that a high air flow results in 38 % higher energy consumption per kilogramme of extracted water, compared to a low air flow
The executed test has proved that drying at a higher air flow will not have a proportionally greater effect
Summary
Da v krmi zmanjšamo vsebnost vlage na skladiščno vrednost. Pri gibanju zraka ob površini rastline se voda uparja – izhlapeva do nasičenosti plasti zraka, ki potuje ob rastlini. Relativna vlažnost se meri v procentih, absolutna pa se običajno podaja v g vode na kilogram zraka. Pri temperaturi 20 °C 1 kg zraka. Tabela 1: Absolutna in relativna vlažnost zraka Table 1: Absolute and relative air humidity. Lahko sprejme 14,7 g vode, pri 25 °C pa 20,14 g vode, kar pomeni 37 % več (Sargent, 1980). Pri odvzemu 0,47 g vode na m3 se zrak ohladi za 1°C (Wirleitner, 2011). Sistem vlaženja zraka poteka adiabatno (Rant, 2011). Na sliki 1 je prikazan idealen adiabatni proces (polna črta), medtem ko je s prekinjeno črto prikazan dejanski proces.
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