Introduction; Machine Description; Basic Absorption Cycle; Double-Effect Reconcentration - Carrier 16JT Series Start Up & Operation Manual

INTRODUCTION

Everyone involved in the start-up, operation, and main-
tenance of the 16JT machine should be thoroughly familiar
with the following instructions and other necessary job data
before initial start-up, and before operating the machine and
its control system or performing machine maintenance. Pro-
cedures are arranged in the sequence required for proper ma-
chine start-up and operation.

MACHINE DESCRIPTION

Basic Absorption Cycle —
uses water as the refrigerant in vessels maintained under a
deep vacuum. The chiller operates on the simple principle
that under low absolute pressure (vacuum), water takes up
heat and vaporizes (boils) at a low temperature. For ex-
ample, at the very deep vacuum of 0.25 in. (6.4 mm) of mer-
cury absolute pressure, water boils at the relatively cool
temperature of only 40 F (4 C). To obtain the energy re-
quired for this boiling, it takes heat from, and therefore chills,
another fluid (usually water). The chilled fluid then can be
used for cooling purposes.
To make the cooling process continuous, the refrigerant
vapor must be removed as it is produced. For this, a solution
of lithium bromide salt in water is used to absorb the water
vapor. Lithium bromide has a high affinity for water, and
will absorb it in large quantities under the right conditions.
The removal of the refrigerant vapor by absorption keeps
the machine pressure low enough for the cooling vaporiza-
tion to continue. However, this process dilutes the solution
and reduces its absorption capacity. Therefore the diluted lithium
bromide solution is pumped to separate vessels where it is
heated to release (boil off) the previously absorbed water.
Relatively cool condensing water from a cooling tower or
other source removes enough heat from this vapor to con-
dense it again into liquid for reuse in the cooling cycle. The
reconcentrated lithium bromide solution is returned to the
original vessel to continue the absorption process.
Double-Effect Reconcentration —
concentrates solution in 2 stages to improve the operating
efficiency. Approximately half of the diluted solution is pumped
to a high-temperature vessel (high stage) where it is heated
directly from high-pressure steam for reconcentration. The
other half of the solution flows to a low-temperature vessel
(low stage) where it is heated for reconcentration by hot wa-
ter vapor released in the high-temperature vessel. The low
stage acts as the condenser for the high stage, so the heat
energy first applied in the high-stage vessel is used again in
The 16JT absorption chiller
The 16JT re-
the low-stage vessel. This cuts the heat input to almost half
of that required for an absorption chiller with a single re-
concentrator.
Machine Construction —
the machine are contained in several vessels (Fig. 1 - 6,
and Table 1).
The large lower shell contains the evaporator and ab-
sorber sections. The evaporator and absorber are positioned
side by side in units 16JT810-880, but the evaporator is
positioned above the absorber in units 16JT080-150,
080L-150L. In the evaporator section, the refrigerant water
vaporizes and cools the chilled water for the air conditioning
or cooling process. In the absorber, vaporized water from
the evaporator is absorbed by lithium bromide solution.
The smaller vessel above the evaporator/absorber assem-
bly is the high-stage generator. Here, approximately half of
the diluted solution from the absorber is heated and recon-
centrated to recover slightly over half of the water previ-
ously absorbed.
The other shell above the evaporator/absorber assembly
contains the low-stage generator and condenser. The other
half of the diluted solution is heated and reconcentrated in
the low-stage generator by high temperature water vapor from
the high-stage generator. The water vapor released from the
solution in this process is condensed to liquid in the con-
denser section.
This chiller also has: two solution heat exchangers and a
steam condensate heat exchanger to improve operating
economy; an external purge system to maintain machine vacuum
by the removal of noncondensables; hermetic pumps to cir-
culate the solution and refrigerant; and various operational,
capacity, and safety devices to provide automatic, reliable
machine performance.
Table 1 — 16JT Description
UNIT ABSORBER/
16JT EVAPORATOR
810-854 Side-by-side
857,865 Side-by-side
873,880 Side-by-side
080-120 Over-and-under
135, 150 Over-and-under
080L-120L Over-and-under
135L,150L Over-and-under
3
The major sections of
PURGE POINTS
SOLUTION
AND
PUMPS
EDUCTORS
1 1
1 2
2 2
2 4
2 or 3 4
2 4
2 or 3 4