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5. SIMULATION AND RESULTS
eliminated by choosing ”manual” in the control panel of the EES model.
Instead, inlet temperatures and temperature differences of the condenser
and absorber are given explicit. The basic parameter configuration is
though the same as for the standard single cycle with cooling tower in
order to make it easier to compare.
The four temperatures of the desorber, condenser, evaporator and
absorber will be varied one at the time and presented in four separate
figures. These temperatures correspond to point 1, 2, 4 and 5 in figure
5.1. They temperatures will be shown in upper x-axis of the graphs.
A temperature change with reference to the standard parameter
configuration for each of the four temperatures is introduced and shown
on the lower x-axis on four graphs. As far as possible the four
temperatures will be varied 10 ◦ C up and down.
COP ABS (equation 1.1, page 8) is the most important indicator of how
the stand alone cycle performs. In each figure COP ABS , the pressures
(high and low) and the concentrations of the strong and weak LiBr
solution will be plotted (w ss and w ws ).
5.1.1 Changing the desorber temperature
The desorber temperature is equivalent to the temperature at which heat
is supplied to the absorption cycle 1 . Changing the desorber temperature
does not affect the high or the low pressure, see figure 5.2A.
On the other hand, the concentration of the strong solution (strong in
LiBr) flowing from the absorber to the desorber (see figure 5.1) is affected
by T DES . Since the high pressure is constant and the temperature of
the desorber is changed, it implies that the concentration of the strong
solution must change as well in order to keep the solution and vapor in
equilibrium (saturated liquid).
When the desorber temperature drops, w ss decreases as well, see
figure 5.2A. If the temperature decreases 10 ◦ C (corresponding to a
desorber temperature of 70 ◦ C) w ss becomes almost equal to w ws .
This means that the pumping factor (mass flow of LiBr solution in
the absorber-desorber cycle relative to the flow of generated refrigerant)
1 To avoid change in the amount of heat supplied, ˙Q HE AT,DES is given explicit for this
particular simulation. T min,W GHE X 2,w,i is set free.
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