Cooling And Heating Cycle; Cooling Cycle - Hyundai HDFN-80-1400 Operation Instructions Manual

2. Cooling and Heating Cycle

Both cooling and heating operation is available with a single unit of the chillerheater only by
switchingover. The absorption cycle in each operation mode is explained respectively as follows :
2.1 Cooling Cycle (See Fig.2.1 A)
The main shell is divided into two parts, lower shell and upper shell. Since containing the absorber
and evaporator is maintained at a high degree of vacuum of about 6 mmHg abs., the refrigerant
sprayed over the surface of the evaporator tubes boils at the saturation temperature corresponding
to this pressure and is evaporated by taking heat from the chilled water flowing in the evaporator
tubes.
In order to effect the heat exchange, the refrigerant is sprayed on the evaporator tubes by the
refrigerant pump with the special nozzles. The lithium bromide solution in the absorber absorbs the
evaporated refrigerant to be diluted about 59% concentration. The absorption heat generated is
taken out by the cooling water. The solution diluted by absorbing the refrigerant in the absorber is
sent to the low temperature heat exchanger and is carried partially to the low pressure generator
and the rest to the high pressure generator through the high temperature heat exchanger by the
solution pump. The solution in the high pressure generator is heated and boiled by the burning gas
(oil) flowing around the surface of the generator tubes to make the refrigerant in the solution be
evaporated. The evaporated refrigerant flows into the low pressure generator tubes and heats the
solution around the tubes. And the refrigerant vapor condenses and flows into the condenser to be
cooled by the cooling water flowing in the condenser tubes.
As the upper shell containing the condenser and low pressure generator is kept at a high vacuum
of about 60 mmHg abs., the condensed refrigerant is sent to the evaporator by differential pressure
between the upper shell and lower shell and gravity to be sprayed in the evaporator.
While, the diluted solution which is diverged from the outlet of the low temperature heat exchanger
is sprayed on the surface of the low pressure generator tubes and heated to be concentrated. And
the intermediate concentrated solution which is heated and concentrated in the high pressure
generator enters the outlet box of the low pressure generator through the high temperature heat
exchanger and then it is mixed with the concentrated solution and sent to the absorber through the
low temperature heat exchanger to absorb the refrigerant vapor. Thus, one cycle of water and
lithium bromide solution completes.
Further, Fig. 2.2 shows the cooing cycle of the absorption chillerheater on the lithium bromide
solution P.T.X. chart. The following is an explanation on Fig.2.2
Point a : A state of the absorber
Point a~b
Point b~c
Point c, d~e
Point e~f
Point b~g
Point f~g
: A state where the dilute solution going out from the absorber is heated in the
low temperature heat exchanger.
: A state where the dilute solution is heated further in the high temperature heat
exchanger.
: A state where the dilute solution heated in the high pressure generator is
concentrated to be intermediate concentrated solution.
: A state where the intermediate concentrated solution going out from the high
pressure generator is cooled down in the high temperature heat exchanger.
: A state where the dilute solution entering the low pressure generator is heated
and concentrated to be concentrated solution.
: A state where intermediate concentrated solution going out from the high
temperature heat exchanger enters the outlet box of the low pressure
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