8 Solar Thermal-Powered Adsorption Chiller
141
MC p
cond
= M cool,cond C p,cool + M t,cond N t,cond C p,t,cond
(8.59)
where subscripts cool and cond represent cooling water and condenser, respectively.
During the ad/de-sorption stage, the cooling water from the outlet of Bed 1 enters
the condenser. Hence, the energy balance equation can be written as,
MC p
cond
dT cond
dt
= −M bed
dw
dt
des
h f g,cond + C p,des
T bed,des − T cond
+ ˙
m cool C p,cool
T out,cool − T cond
1 − exp
−
(U A) cond
˙
m cool C p,cool
(8.60)
The water temperature at the outlet of the condenser can be expressed as,
T out,cond = T cond −
T cond − T out,cool
exp
−
(U A) cond
˙
m cool C p,cool
(8.61)
In the mass recovery stage, the condenser is not connected to any bed. Thus, the
temperatures of the condenser and cooling water don’t change at this stage.
During the heat recovery stage, the condenser is isolated from the beds and water
from Bed 1 first flows through Bed 2, before entering the condenser. Thus the energy
balance for this stage can be modeled as,
MC p
cond
dT cond
dt
= ˙
m cool C p,cool
T out,ads − T cond
1 − exp
−
(U A) cond
˙
m cool C p,cool
(8.62)
The water temperature at the outlet of condenser is,
T out,cond = T cond −
T cond − T out,ads
exp
−
(U A) cond
˙
m cool C p,cool
(8.63)
8.5.3.4 Performance Parameters
An adsorption chiller is usually specified by its cooling capacity and coefficient of
performance (COP). The cooling capacity can be defined as the amount of cooling
effect that an adsorption chiller is able to produce. For a chiller having a cycle time
of t cycle , the cooling capacity can be defined by,
Q c =
t cycle
0
˙
m ch C p,ch
T in,ch − T out,ch
dt
t cycle
(8.64)