Íslenskar landbúnaðarrannsóknir - 01.09.1971, Side 16

14 ÍSLENZKAR LANDBUNAÐARRANNSÓKNIR
SUMMARY
BARN HAY DRYING WITH PREHEATED AIR
Biarni Guðmundsson,
Agricultural Research Institute,
Agricultural Engineering Department, Hvanneyri, Iceland.
In the years 1960—1962 and 1964 four experiments were carried out on com-
paring different methods of hay drying with unheated and prelieated air in
a barn. The aim of these experiments was to study the losses of feeding value
in the hay, of drying and storage and the cost of drying.
Increasing the temperature of the inlet air of 6—10° C, the output of the
drying plant was doubled compared with drying with unheated air. The
results indicate that the rate of loading the hay into tlie barn should be
governed by the moisture content of the hay, especially when using preheated
air. This must be done to prevent recondensation of moisture in the top
layers of the hay.
If the hay contained less than 50 per cent (w.b.) moisture when loadecl into
the barn ancl the weather conditions were favourable, there was a little and
insignificant difference in the losses of feeding value between the two drying
methods. Such being the case the dry matter losses were less than 3 per cent.
If hay with a high moisture content (50—60 per cent w.b.) was loaded into tlie
barn under unfavourable weather conditions, the dry matter losses were 6.5—
7.4 per cent. In that case the quality of the hay after drying and storage was
quite variable, particularly in the cold air plant.
Barn hay drying with preheated air is expensive, but yet it seems to be
economic when the hay loaded into the barn is high in moisture, and wlien
the weather conditions are unfavourable. Tlie results suggest that drying with
preheated air could be done rnore economically by running the lieater only
when the relative humidity of the air is high (> 75 per cent).
Despite the fact that the drying capacity of the inlet air varied frorn one
experiment period to another, practically no differences in the output of the
cold-air plant could be observed. This fact may indicate that the drying rate
is primarily governecl by the heat energy generation in the hay when drying
with unheatecl air.