IEA Solar Heating and Cooling Programm - NachhaltigWirtschaften.at

IEA SHC Task 38 Solar Air Conditioning and Refrigeration Subtask C2-A, November 9, 2009
The glass cover exchanges heat by convection with the outside air and by radiation with the
sky and the absorber. The absorber receives solar radiation and heats the fluid inside the
tube. The vapour rising from the heat pipe enters the condenser and releases energy to the
circulating storage fluid, then exits the condenser as a saturated liquid. The heat pipe liquid is
heated to saturation before the evaporation process begins.
The governing equations for each component (characterized by heat capacity C and
temperature T):
Glass cover:
M
g
C
g
dT
dt
g
4 4
4 4
= ε σS
( T − T ) + ε σS
( T − T ) + S h ( T − T )
(16)
g
g
sky
g
p
p
p
g
g
g
a
g
Absorber:
M
p
C
p
dT
dt
p
4 4
= ε σS
( T − T ) + GταS
+ S h ( T − T )
(17)
p
p
g
p
p
H
H
sat
p
Vapour flow rate:
m L = S h T − T )
(18)
v
H
H
(
p sat
Condenser:
M
c
C
dT
) = m L + S h ( T − T )
(19)
dt
c
c
(
v v c c f c
Storage fluid:
m
∂T
f
(
∂t
∂T
f
1C
f
+ u ) = Schc
( Tc
− T
f
∂z
)
(20)
Storage tank
In order to take into account thermal stratification in the storage tank, it is divided into n
nodes [14]. The following equations apply to the first node, the last node (n=12) and the ith
current node:
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