BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI

122 Petru Cârlescu et al
air
malt bed
a
b
air inlet
Fig. 1 – Geometry dryer: a – geometry; b – meshing.
Processing the initial stage to impose conditions and calculation is
performed in software FLUENT. The conditions chosen to study the effects of
temperature and air flow on conditions within a bed of malt are presented in
Table 2.
Table 2
Initial conditions
W – initial moisture
content,of the malt, %
T – initial temperature
of the malt, º C
v – velocity of the
air, m/s
49 21 1
The physical properties of the system investigated
Specific heat of air c a – J/kg º C 1017
Specific heat of liquid water c w – J/kg º C 4187
Specific heat of malt c s - J/kg º C 2008
Density of air ρ a – kg/m 3 1.169
Density of malt ρ s – kg/m 3 639.2
Temperature and humidity content in the input region are introduced as
five order polynomial functions of time. Function of temperature is introduced
in UDF code in Kelvin as follows
−20 5 −16 4 −12 3 −8 2
( ) = 10 −6⋅ 10 + 9⋅ 10 + 5⋅10
f T τ τ τ
+ 0.0012τ
+ 303.22,
τ +
(13)
where: τ – drying time between 0...25200 s.
The UDF is introduced as a function of humidity content X kg vapor/kg
dry air depending on time.
−23 5 −18 4 −14 3 −10 2
( ) 210 10 210 10
f X = ⋅ τ − τ + ⋅ τ − τ +
+ ⋅ +
−7
4 10 τ 0.0101,
(14)