Troubleshooting refrigeration systems
►
1
The design of industrial refrigeration systems is in theory straightforward. In practice,
poorly tuned or malfunctioning components, fouling especially by oil, inert gas in the
system, misplaced pipe lines, etc., can lead to capacity loss, control problems, frequent
shut downs and other difficult to find and explain phenomena. This is typical for large
custom made plants.
Manufacturers of small standard units such as air conditioning OEMs, can usually iron
out the problems before a chiller line goes into production. An industrial contractor
usually does not have this luxury; the plant has to work immediately.
General rules are hard to give as all systems are different and the troubleshooter has to
be a bit of a detective. Below is an arbitrarily classification of possible malfunctions:
► Mechanical failures such as worn-out pumps, broken valves or compressor slides, i.e. all
types of malfunctioning in machines (by definition, a machine has moving parts).
► Leakages in various components (a special case will be treated below).
► Construction errors such as faulty welds , components not made as conceived, wrong
components, e.g. a solenoid valve closing instead of opening, a far too small valve,
compressor, pipe, etc.
General considerations, I.
◄ ►
2
► Fouling, corrosion and fatigue.
► Electrical, i.e. all parts of the electrical power circuit.
► Control, e.g. outright failures or wrong control algorithms.
► Faulty refrigerant, oil, brine or brine of wrong concentration.
► The above items are usually but not always clear-cut and the source of the trouble can
usually be found and will not be treated here. However, sometimes more difficult to find
troubles arise. The source can be any of the malfunctions above or simply that each
component is faultless but together they do no work.
► The operator of the refrigeration plant has three interfaces to the system: the electrical power
consumption, the condenser and the evaporator. We will deal here with troubleshooting the
two latter, especially plate heat exchangers.
► The condenser pressure is too high, alternatively it increases and finally, the compressor HP
cut out activates.
► The refrigeration system does not give the required capacity at specified conditions. “The
evaporator is too small” is a frequent complaint.
General considerations, II.
◄ ►
3
The pressure is too high but remains stable but sometimes the pressure continues to
increase until the compressor HP cut-out is activated. Below are some frequent causes.
► Fouling on the water side, less frequent on the refrigerant side.
► A condenser which is too small, either by area, heat transfer coefficient or temperature
difference.
► Higher load than foreseen. Double check with evaporator & oil cooler load and compressor
load. Sometimes, the load of a refrigerant cooled oil cooler, which ultimately has to be
removed by the condenser, is forgotten.
► A flooded condenser. A condenser can flood for four reasons: Pressure drop is too high in
one of the parallel connected condensers, a misplaced equalization line, an obstruction at the
exit or a refrigerant overcharge.
► Inerts in the vapour.
► Subcooling in the condenser. To be effective, there has to be a liquid level in the condenser
but then the condensing area is decreased. The most serious consideration is that inerts can
get trapped in the condenser.
► Obstruction of the exit. This usually less of a problem. As the condensate will flash to a pretty
low temperature, the condenser could support a very large pressure drop. The drawback is
that it might flash in the pipes before the expansion valve. Flashing refrigerant should be
discovered by a sight glass, which always should be installed in the liquid line just before the
expansion valve.
Troubleshooting condensers
◄ ►
4
An evaporator that doesn’t give the required capacity is sometimes a complaint from
operators of refrigeration plants. The designer of the evaporator then patiently has to
explain that an evaporator is a passive component, which can only give capacity
presumed there is capacity, i.e. a sufficient refrigerant flow, on the other side. Below are
some effects, which can lower the evaporation temperature, the most frequent claim:
► What happens if the evaporator really is too small? Too small in this respect is that either the
area or the K-value is too small. The evaporator then produces less vapour than the compressor can handle. The pressure falls, which increases the vapour volume, the evaporator
produces more vapour because of the higher MTD, the capacity of compressor decreases
and finally the system stabilizes at a lower evaporation temperature.
► What happens if there is not enough refrigerant entering the evaporator. As before, the flow
is less than the compressor can handle, the temperature decreases and the MTD increases
but this has no effect on the capacity and there is not sufficient refrigerant. The evaporator
has to be in balance and it solves the MTD equation by superheating the vapour, effectively
decreasing the MTD again. This is valid for a DX evaporator. A flooded flow evaporator is
connected to a fairly large refrigerant charge and this can provide sufficient refrigerant to
even out a temporarily refrigerant shortage but if this persists, the charge is consumed and
the same occurs.
► A superheated refrigerant is a sure sign that an evaporator is operating below its
possible capacity.
Troubleshooting evaporators, I.
◄ ►
5
► Oil in an ammonia system can foul an evaporator and has to be drained regularly.
► If water is present, oil will form a slurry, which fouls the evaporator.
► Water in ammonia will increase the evaporation temperature for a given pressure, thus
decrease the capacity. By pumping down the system to a low temperature, most of the water
remains as a liquid phase and can be drained from the system
► A separator placed too high. When the two-phase mixture enters the separator it is at the
boiling point. When the refrigerant then descends to the evaporator, the pressure increases and
the refrigerant is now subcooled.
► The K-value in the subcooling section is low.
► The refrigerant is preheated above the nominal evaporation temperatureand the MTD
decreases.
► The return leg is likely to be long and high, giving a high pressure drop and thus a large
temperature difference between evaporator and separator.
► All this contributes to decrease the capacity of the evaporator. This is especially important at
low temperatures. With a liquid column of 10 meters, the subcooling of ammonia is about 3.9 K
for an evaporation temperature of 0 °C. For an evaporation temperature of -40 °C, the
subcooling increases to 17.6 K. That means that the evaporator will probably not work at all,
the pressure at the evaporator is simply to large for the evaporation to take place.
► A far too low liquid level in a flooded flow system might not be able to lift the flow through the
return leg. The result is low circulation and low capacity.
► Demisters, vapour superheaters and filters in the suction line obstruct the refrigerant flow and
increases the difference between the evaporator and suction temperatures.
Troubleshooting evaporators, II.
◄ ►
6
► A too small pipe diameter or a too long pipe, valves, many bends and other obstructions in
the return leg in a flooded system cause the exit pressure drop to increase and the result
might be a large difference between the evaporator and separator pressures. As above, the
effect increases with decreasing temperature.
► The difference between the evaporator and separator pressures is frequently a
subject of contention between the evaporator and the system designer.
► Pumped flow in flooded system allows a designer a lot of options, which he maybe shouldn’t
use, e.g. a too highly placed separator. That means a long subcooling zone and a high
pressure drop in the return leg.
► Sometimes an ejector pump, driven by the flashing refrigerant, is inserted in the
thermosiphon loop in order to improve the circulation. In order to do so, it has to be properly
designed, something which is not always done. An ejector is unfortunately also a good oil
atomizer and the oil can enter the channels and foul the surface.
► Distribution of the refrigerant and of high viscosity brines between parallel channels is a
difficult problem especially for DX evaporator, somewhat less for flooded flow evaporators.
► Both the above problems can be revealed as unequal temperature distribution on the
outside of the evaporator. A thermal camera or the formation of frost on the evaporator is a
good help.
► Frost formation at start up of an evaporator is an excellent way of discovering distribution
problems.
Troubleshooting evaporators, III.
◄ ►
7
► Distribution problem can also happen for water at high temperatures if the flow and thus the
pressure drop is very low, more so in DX than in thermosiphons. Use multiple passes on the
water side to increase the ΔP.
► Maldistribution can also cause freezing as the water cools unevenly, a problem in DX more than
in flooded.
► A TEV before a DX evaporator has to be correctly placed. Unfortunately, a lot of valves give a
well separated two-phase mixture and some evaporators are very sensitive to this. Don’t install
bends after the TEV.
► There are some questionable control algorithms for some electronic EVs. One such, if not
correctly adjusted, increases the superheat when the capacity increases. That means that the
evaporation temperature has to be lower than necessary just to accommodate a too high
superheat.
► The rated capacity for a TEV is usually given for around 11 K. If the evaporator superheat is 5
K, there is no possibility for the valve to give its rated capacity. Choose a larger valve.
Troubleshooting evaporators, IV.
◄ ►
8
Propane condenser
Propane to
Propane tank
trucks
Propane from
tanker
Comments:
Discussion:
Solution:
The
A condenser
further
results
check
ofwas
the
showed
not
propane
designed
that
analysis
ita was
for an
not
are
inert
installed
interesting.
gas condensation.
in aAs
refrigeration
theNo
inert
Even
as content
Problem:The
The
compressors
cut
out
after
very
short
operating
time.
particular
system
small
is
veryquantities
low,
but used
itwas
means
offor
ancondensing,
that
inert
the
gas
propane
increase
after
content
compression,
the
size
is close
of the
ofto
propane
condenser
100
%. vapour
Moreover,
considerably.
fromit awas
tank
It it
information
given
about
the
process
it was
going
to
operate
in.
Consequently
farm
had
calibrated
when
replaced
for
adesigned
tanker
butane.
with
unloaded
Analyzing
propane.
a concentration
larger
Whenin
condenser.
the
tank to
fills
100
up,%vapour
with anleaves.
uncalibrated
wasto
it be
was
asaaconsiderably
normal
condenser
aclose
refrigeration
system.
An
inspection at
However,
analyzer
could
whengive
the
storage
large particular
errors.
tank It
unloads,
is– not
possible
it has
tobeget
charged
a reading
withcloser
nitrogen
thantoa couple
the site showed
nothing
except
the to
compressor
cut-out.
An analysis
of the of
keep
percent
thepoints.100
pressure
above
% propane
atmospheric,
means
no
otherwise
inerts,
99
air%
might
means
leak
1%
in andtoan
that
explosion
increases the
propane
content was
made
with
a butane
analyzer
and
recalculated
propane.
could occur.size
condenser
Theconsiderably.
propane recovery
It would
system
have thus
beenhas
better
to be
to designed
have a nitrogen
not foranalyzer
pure
as
propane
the
difference
but forisalarge
propane-nitrogen
between 0 and
mixture.
1 %.
Fig. 1. Inert gas in a propane vapour.
◄ ►
9
Discussion:
inspection
of
Problem: Ammonia
Solution:
TheAncondenser
is easy
could
tothe
vent.
system
showed
nothing
particular.
operate
A
vent was
for only
placed
one
onofthe
theLR
two
and
The
condenser
be wellof
compressors.
the
vapour
was seemed
fed into atobucket
drained
to Ifthe
LR.isIt air
hadinrecently
ice water.
there
ammonia,
been opened, inspected and found
itOnce
bubbles,
the
pure ammonia
started,
the
doesn’t
presclean.
No second
physical
obstruction
was
sure
bubble.
and cut
out the
foundincreased
in the adjacent
pipes.
compressors.
However,
a reading
of the inlet
After
half an
hour bubbling,
the
water
and the
exit condensate
manometer
calmed
down and
temperature showed practically the
became
steady after four more
same temperature.
hours venting. It was then possible
The
cause the
could
be with
either
of two
to
operate
plant
both
the or
possibilities, a flooded condenser
compressors.
inerts in the vapour, but it is difficult
to determine which.
Comments: An undampened
The
compressor
manometers
gave
manometer
is a valuable
tool for
a
hint.checks,
There were
three with difficult
inerts
especially
undampened manometers of the
to
ventdesign,
halocarbons.
same
oil, suction and
discharge. The oil was rock steady,
the suction vibrated a little, while the
discharge needle was almost
impossible to see.
A vibrating discharge manometer
hints of inerts.
Fig. 2. Compressor cut-out.
◄ ►
10
Discussion:
The
condenser
and
its
Problem:
Solution: The
The
capacity
separator
ofwas
neither
lowered
theexit
to
theboth
LR the
– nor
normally
a critical
point
evaporator
and
evaporator
the condenser
and condenser
was –
were correctly made. Venting was
sufficient
problemsfrom
indisappeared
this
flooded
possible
the
LR butevaporator
no inerts were
system.
Both
had
recently
been opened,
present.
inspected
Comments:
andPlacement
cleaned. of the expan-sion
However,
the
separator
placed can
very
valve and LR above thewas
condenser
high
up, some ten
meters
and
the evaThe condenser
shown
here,
exhibited
be
done
but
the
risk
for
malfunc-tioning
poration
temperature
was well
below zero
large capacity
and pressure
oscillations
increases
- especially
ventingwith
will the
be
Celcius.
This
led to
problems
and occasionally
compressor
cut-outs.
evaporator,
difficult - and
see
troubleshooting
also Figure 10.
will be more
complicated.
The
expansion valve was placed close to
the separator and connected to the LR by
is thus
not pipe.
recommended,
for
aIt fairly
large
The heightneither
difference
to
the condenser
meant
that there was a
flooded
nor for DX
evaporators.
very large danger of vapour flashing in
the vertical pipe.
When the valve closes, the condensate
then flows back into the receiver – the
large pipe makes it easy - and from this it
floods the condenser. The system
ammonia filling was pretty high, which
compounded this problem.
Fig. 3. A too high placed expansion valve.
◄ ►
11
A
B1
C
B2
B3
h
h
Discussion:
ΔPwas
is higher
in the
than
in the
S&THEs.
Obviously,
the ΔP
Problem: This
Solution:
TheThe
collector
PHE
pipe
replacing
was
lowered
a PHE
corroded
and S&THEs,
the
liquid
column
equal to
isthe
now
two
created
others,
in from
the
point
A to
C have
to be
same regardless if the path is A -B1(2)-C or A - B3 - C.
vertical
pipe
outside
thethe
PHE.
However,
PHE
didn’t give the
the capacity.
subcooled
At the exitthe
of the
condensers,
pressure A
is substantially
lower in B3 than
in B1 &condensate
B2. The
indicated
a
flooded
condenser.
condensate lines form a communicating system with a lower pressure in one leg, B3.
That causes a higher liquid column – h - to form in this leg.
Unfortunately in this case, the condensate pipes connect just below the exits, the higher
liquid column in B3 builds up in the plate channels, floods these and the effective area is
decreased.
Fig. 4. Parallel connected condensers.
◄ ►
12
Discussion:
Problem:
Solution:
The
system
was equipped
The
plate condenser
didn’t with
give athe
Reconnection
of
the
equalization
“surge”
LR.
rated
A substantially
line tocapacity.
immediately
before the PHE
The
condensate
doesn’t
pass a
subcooled
drained thecondensate
condenser. indicated
through,
it is just in communication
flooded condenser.
to
take up load variations. To
Comments:
facilitate
this, it is
to case
the
The difference
to connected
the previous
condenser
inlet
via
an
equalization
Misplaced
equalization
lines
and
is
that
here
there
is
only
onethis
line. Vapour moves through
in
poorly
conceived
LRs
are
aconcommon
condenser,
parallel.
& and out
ofnot
themany
LR
asin
the
densateofmoves
in andtroubles.
out.
source
condenser
The vapour entering the condenser
inlet from the LR should then recondense. As the pressure is higher
at the condenser inlet than at the
exit, it is necessary with a liquid
column to compensate for this ΔP.
The total ΔP in two parallel legs
should be equal.
In this case, the equalization line
was connected upstream a desuperheater with a fairly large ΔP
and the resulting liquid column
became high and flooded the
condenser.
Fig. 5. A misplaced equalization line.
◄ ►
13
Underside
of pipe
Ambient
temperature
Equalization line
To bulb
The
result
was
that baffling
that
attempt
madeexpansion
to
pictures
fromMoreover,
the back side,
Problem:
A
check
ofThe
the valve
installation
showed
was
that
aan
pretty
there
normal
waswas
a leakage
direct
in take
the packing
evaporator
box.
equipped
the
with
where
the bulb
and the equalization
line
connection
thesmall
exit pipe
could
be
seen.
a standard
equalization
thermostatic
connection
expansion
at the suction
valve
gas
with
pipeexternal
was to
very
equalization,
– high
but
ΔP.
it simply
Thus:
didn’t
produce
any
cooling at
The
start
up showed
theall.
sequence
At first
was orange,
i.e. ambient
- HP
condensate
leaks
through
thebelow.
packing
box everything
into the equalization
chamber.
temperature. Then:
Discussion: A check with a thermal camera showed some interesting results. The first
-- Exit
Theofdiaphragm
is pressed
down and
the valve
closes.
EQ line.
The
connection
turning
blue.
pictures
were
taken
from
the frontwas
sideslowly
only as
the back
side was difficult to reach.
-- Below
No more refrigerant
leaves
the
normal
exit. part of the pipe below the connection
connection.
A little
later,
thetemperature”
bottom
The exit EQ
pipe,
above marked
“Ambient
was just that, i.e. no cooling was
turned
-discovered.
Liquid blue.
condensate flows through the EQ line to the connection, expands and cools.
-Astonishingly
Further
downenough,
the pipe.
blue
colour
slowly
spread
downwards.
Liquid cold
refrigerant
theThe
drops
pipe
down
marked
to “Cold
the
pipe
pipe
bottom
underside“
and cools
several
this.meters after the
TEV, became blue on the picture somewhat after the start, indicating a low temperature.
Solution: The TEV was exchanged and everything worked.
The part just behind the PHE could not be seen. The equalization line was ambient
temperature. A thermal camera is an extremely useful tool when troubleshooting.
Comments:
Fig. 6. A broken expansion valve.
◄ ►
14
Oil drain.
A. Ejector inlet (NH3 in a SWPHE)
B. Pipe-in-pipe inlet (R134a in a CB).
Solution: Both
Problem:
Discussion:
Injection
were
flooded
redesigned
offlow
theevaporators
flashing
as normal
refrigerant
above
thermosiphons.
had
in the
injection
circulation
of flashing
loop can
refrigerant
improve
in the
loop in order
circulation
if atoproperly
increasedesigned
the circulation.
ejector None
pumpof
is them
used.gave the intended capacity.
A. The pipe was made slightly upwards inclining and with an oil drain at the lowest point.
A. The
The
ejector
low capacity
in A waswas
a home
at least
made
partly
design
due toofoilquestionable
fouling on thefunctionality.
ammonia side.
When A was
B.
A
soluble
oil
does
not
need
an
oil
drain.
dismounted, it turned out that there was a lot of oil in the evaporator, not astonishingly as
B.
This CBishad
stability
problems and and occasionally reversed flow.
an ejector
a good
atomizer.
A
closer inspection
of B design
showedcan
thatimprove
there was
flow of
drop
Comments:
An ejector
the back
operation
butrefrigerant
a correct through
design isthe
difficult
leg
back to the separator. The pipe-in-pipe design had no ejector function at all. It was
to make.
easier for the vapour to pass back through the drop leg than through the evaporator.
Figure 7. Flooded flow evaporators with ejector. ◄ ► 15
To unit coolers
Return from SWPHE
To SWPHE
►
Broken
parts,
forgotten
tools,
► Mechanical.
At the installation,
there
were
probably
bothorShortly
►
►after
ItAisliquid
not installation
unconceivable
line, passing
to imagine
a hot
a area
unit or
Vertical
Problem:
the
of athrough
Solution:
metal
pieces
can
get trapped
not lines
liquid lines
at
the roof
top and but
vapour
cooler
exposed
closing
to the
and
sun,
thecan
resulting
be sufficiently
liquid column
separator
new
PHE in
evaporator
– a flooded,
forced
flow
The cause
of bangs
the noise
found
until
unmovable
and cause the noise. system
the cold storage.
inheated
thewas
vertical
fornot
refrigerant
feeder
pipe
to vaporize
line flow when
down the
or
– loud
and
noises
were
heard
year
later, when refrigerant
the
openedthe
flowsystem
stops.towas
Restarting
evaporate,
with
flow
ensuing
will cause
noise,
a
ina the
system.
Moreover,
seevalve
the figure
above; there
were
a
► An
expansion
is sometimes,
especially
for maintenance. Asee
broken
valve
vapour
movehad
with high speed along
Slideplug
3. tostem
number
floodedpreceded
flow unit coolers
connected
The
source
of
noises
in
metal
piping
can
be
in
DX systems,
by a solenoid
valve.
moved to the first upwards
after the
the pipe. bend
The vapour
can easily pass a
in pumpdown
parallel to the
liquid evaporator.
These
difficult
to
find
but
as
the
evaporator
was
the
If
is made,
the pipe after
the
sole►
However,
the
noise
had
metallic
pumps. The liquid
velocity
then a definite
valve
but the was
subsequent
liquid column
units
coolers
installedofatliquid
least
tennew
meter
only
item
was
the prime
suspect.
noid valve
willwere
be emptied
refrigerant.
By
using
a at
time
insufficient
to itlift
itquality.
further,
it damages
stayed
thehonoured
can’t,
i.e.
and
noise. method –
higher the
thansolenoid
the PHE.
It is opens,
difficult,a to
say swirled
the
When
valve
liquid
coputting
ear
to thelarge
pipe at various locabend,
and an
made
The
evaporatoraround
was
installed
in
a noise.
very
►
If
the
pressure
is
suddenly
e.g.
least, with
to operate
parallel
units
in general
andthe
lumn
increasing
speed
moves
towards
tions, it was possible to find increased,
the place with
commercial cold storage.
a hot
gas defrosting,
canatcause
a
different
types
at different
heights can
be from
TEV,
which
easily
can be damaged
apart
the
strongest
noise. It itwas
the upwards
(previous)
low
pressure
vapour to implode.
close
to impossible.
the
minor
problem of noise. InstallDiscussion:
the solenoidLoud, bend
sharp
noise
from
an itemcirculation
after
the
ammonia
pumps.
is the same
phenomena as cavitation.
just before the TEV.
with no moving partsThis
is unlikely
but then,
where does the noise originate?
► In a vapour line, e.g. for hot gas defrost, pasThere are
a couple of causes for noise shown
sing through the cold storage, refrigerant
can
onAt
the
next page:
condense when the line is shut off.
restart,
a
SWPHE
highPump
speedstation
liquid plug can damage a valve.
Figure 8. Bangs in a pumped flow evaporator..
◄ ►
16
Problem:
A chiller manufacturer had problems with a
custom made unit. The nominal temperature
program was:
20 % Ethylene glycol +3 →
Propane of
-8 +(5) ←
-3 °C
-8 °C.
The unit was assembled from parts purchased in some four different countries.
At start-up the end temperature was about
10 K instead of the nominal 5 K
Not surprisingly, all component manufacturers claimed that their particular component was faultless and worked well in similar
applications. The technical manager was
helpless.
Discussion:
During a technical seminar, the manager
understood that the valve was not correctly
installed; he remembered that the valve was
possibly installed before a bend.
Solution:
The valve position was changed the same
day and nominal duty was obtained.
Figure 9. An incorrectly installed
thermostatic expansion valve.
◄ ►
17
The final
There
was
measured
a strong
suspicion
was taken
that
six months
the pressure
later at
Problem:
This
large ammonia
thermosiphon
the annual
drop
from the
It turned
exitdidn’t
–out
thethat
evaporation
the
installation
inoverhaul.
a evaporator
chemical
plant
give
the angle
capacity.
valve was far via
temperature,
toothe
small
separator
and was– ex-changed.
the separatorThis
There
wasdecreased
a problem
with hunting.
measure
pressure
–also
to the
compressor
considerably
suction
the difference
connection –
between
the
suction
thepressure
evaporation
- could
and
besuction
very
Discussion:
An
inspection
of the
plant large.
showed a very
temperatures.
Unfortunately,
a
The
refrigeration
remaining
vessel,
difference
as
opposite
was mainly
to
nice installation, everything – including the tightening
due
a
chemical
to the internals
vessel, has
of the
no separator.
man hole. The
Inspection
huntingof
bolts
of
the
PHE
–
properly
insulated
and
clad
by
alsointerior
the
decreased.
was not possible.
aluminium sheets.
The separatorWe
Comments:
was
here
placed
encounter
very high,
threemuch
of thehigher
most
Unfortunately
there were
hardly That
any
instruments
or
frequent
than
the evaporator
problems
inrequired.
a flooded
installation.
increases the
subcooling
zone,
especiallyhad
at as
lowonly
temperatures, sight
glasses,
the separator
►
Oil
drain.
Keep
of the
25
°C, inthe
thisinterior
installation.
instrumentation
the pressure
andseparator
the ammoniaas
level. It
►
The
difference
betweenYou
the evaporation
simple
as
possible.
never
was
really
aTwo
black
box.
Solution:
measures
were
taken atknow
site.andif
►
suction
temperatures.
itfurther
is
built
conceived.
There
was
aas
possibility
to drain
the oil
from
A
inspection
showed
that there
was
no a
►
A separator
placed
too
high.
connection
closer
todrain
the evaporator
than
automatic
oilmuch
drain
and the
point was from
thethe
original
oilrather
drain.
Draining
reveal
quite
aevaporator.
lot of oil in
separator
than
from head
just
before
the
Conclusion:
If
the
large
is
not
necessary,
the
system.
This improved
the
capacity The
somewhat
place
the
separator
as
low
as
possible.
but
not entirely.
Discussion
contractor
revealeddescribed
that the
capacity
ofwith
the the
evaporator
in also
the system
separator
was
full of
baffles,
guide
pipe temin slide
3 improved
the
separator
was
An
try was
made
to when
measure
the vanes,
evaporation
distributors
the
gas,when
protection
sheets
lowered. There
are
cases
thethe
evaporator
perature.
Itfor
had
toflash
be
done
outside
returnand
leg.a
needs
large pressure
drop
butdue
then,
This
is adifficult,
especially
here,
to the
the entire
solid
demister.
thermosiphon
has to be
for this
and not
insulation.
As aloop
reference,
thedesign
separator
temperaonly was
the evaporator.
ture
also measured in the same way. The result confirmed the suspicion that the temperature
difference was very large, i.e. the evaporation
temperature was far above the suction temp.
Figure 10. Lack of capacity in a
low temperature evaporator.
◄
18