JOHNSON CONTROLS
18
FORM 155.32-ICOM1.EN.GB
ISSUE DATE: 10/13/2017
SECTION 2 – PRODUCT DESCRIPTION
LG4
Evaporator
(Upper)
Absorber
(Upper)
Absorber
(Lower)
Evaporator
(Lower)
LD19980_a3
Chilled
Water
In
Cooling
Water
In
Chilled
Water
Out
Refrigerant
Concentrated
LiBr
Dilute (weak)
Solution Out
PLATE TYPE HEAT EXCHANGERS
The dilute (weak) LiBr solution leaving the absorber
section is pumped through various plate type heat ex-
changers (such as the low temperature heat exchanger,
LTG refrigerant condensate heat exchanger,
and high
temperature heat exchanger) before it enters the high
temperature generator and low temperature genera-
tor sections. These plate type heat exchangers provide
cycle efficiency by preheating the dilute solution. Pre-
heating the dilute solution reduces the consumption of
the driving heat source in the high temperature genera-
tor section. The concentrated solution flows out of the
generators and back through the various heat exchang-
ers.
Low Temp.
Heat Exchanger
LD19980_a2
Concentrated
Solution
Out
Dilute
Solution
Out
Dilute
Solution In
Concentrated
Solution In
The relatively high temperature solution streams from
the two generators are used to pre-heat the weak solu-
tion stream leaving the absorber.
PARALLEL FLOW
The unique parallel flow divides the solution between
the low temperature generator and the high tempera-
ture generator sections into two parallel, balanced
paths. The result is a safer and more efficient operation
at a much lower pressure than conventional series-flow
designs. The various solution-to-solution plate type
heat exchangers optimize efficiency by enabling effec-
tive heat transfer between the diluted (weak) and the
concentrated LiBr solutions.
HIGH TEMPERATURE GENERATOR (HTG)
YHAU’s high temperature generator section has the
unique liquid tube design in which the dilute Lithium
Bromide solution coming from the high temperature
heat exchanger is inside the tubes. The products of
combustion (exhaust gas from burning of natural gas)
are on the shell side. The hot refrigerant vapor boiled
off is sent to the low temperature generator. This leaves
behind a strong solution which is returned through the
high temperature heat exchanger.
The liquid tube design is efficient and compact with
lower pressure drop as compared to the conventional
smoke tube type design in which the exhaust gas is
inside the tubes while the Lithium Bromide solution
is on the shell side. Being more efficient, the exhaust
gas leaving temperature is lower than the smoke tube
design.
The liquid tube design also benefits from less volume
of Lithium Bromide solution and hence faster startup
time. It does not require any ceramic refractory com-
pared to the conventional design, therefore improved
reliability.
LOW TEMPERATURE GENERATOR (LTG)
The hot refrigerant vapor from the high temperature
generator heats up the dilute solution coming in from
the low temperature heat exchanger. This vapor then
condenses into hot refrigerant liquid and is sent to the
condenser via the drain heat exchanger. The additional
vapor produced in the LTG by heating up the dilute
solution is sent to the condenser.
The LTG is of a falling film design, ensuring superior
heat transfer and enhanced life by eliminating wear and
tear at the tube supports.
