Texas
W
JOHN
or
reference
material.
Chapter
21
This
placed on
included.
Roy
J.
Dossat
July,
1961
the force
particular
unit-
surface of the
some 50 mi or
the upper limits
atmosphere does not
the
tube
of
mercury
29.921
in.
high
to
a
pressure
of
following
equa-
the
in
either
is to be
the
tube.
If
the
is
nected
mercury
is
that the
pressure
Hg
(1.96
pressure
of
30
in.
Hg.
Fig.
1-5.
Bourdon
calibrated to
decreases. Any change
vessel and the atmos-
to the
1-7.
to the
a
body
can
do
in
passing
from
one
condition
or
pounds
V
is
its
kinetic
energy?
Solution.
Velocity
the
instance,
work
The
the body
its motion,
1-16.
Total
External
Energy.
forms,
is
or
devices. Mechanical chemical energy,
which exist between the
various forms of energy
later.
PROBLEMS
1.
with
water.
If
the
basin
Ans.
68
psf.
Ans. 0.472 psi.
2. If the
exerted on the top-
cylinder bore
is 5
gas
in
wall reads 29.6 in.
in psi.
is
hoisted
to
the
roof
ground,
weighing 3000 lb
is
flowing at
Ans. 800.84 ft-lb
lb
per
physical
states
of
matter.
internal
potential
the
position
motion
the
change
its
shape.
M.
The
energy
and
they
extent and to
They are
one another
 flow.
Although
a
any containing
a body.
A high
thermal
advantage
speaking
countries,
whereas
the
Centigrade
scale
is
water boils
between these two
for
the
Abso-
lute
tempera-
tures
of water,
heat
values
of
materials
in
the
are
is
absorbed
by
cause a change
liquid
phase
of
the
liquid
is
further
increased
a
vaporization.
2-28.
in
solid
becomes.
city
to
about
a
32°
F.
In
general,
energy to
the mole-
required
latent
velocity.
the fusion temperature
1728
Btu
in
melting
state is set up
liquid
rises.
But
here
again,
as
in
at any
will change to
Equation
2-8,
quantity
of
example,
vaporizes
at
4450°
F,
copper
at
4250°
F,
and
lead
3000°
F.
Water,
of
course,
boils
at
212°
F,
and
to
increase
amount
of
energy
work
necessary
to
overcome
these
restraining
forces
is
very
great.
The
quantity
is
known
saturation tem-
the material
the
pressure
is
constant,
done
is
proportional
External
work
is
much
heat
gal
of
water
at
the
=
water
Rearranging
and
apply-
ing
Equation
heat
required
to
bring
it
to
that
condition
from
an
initial
condition
of
saturated
32°
F
That
the internal
nail struck
surfaces rubbing
ft-lb ofmechanical
is
40°
10 gal of
the relatively
that
into
constant
pressure
at random
the
gas
frequently
collide
magnitude of the
pressure exerted depends
velocity
of
course, when
pressure
in
psia?
20
x
5
is
are
If the gas is
the volume
unchanged or
square
pressure of the air
has been shown
an
increase
tempera-
ture
of
a
increased
or
decreased,
either case as
long as the
units are consistent.
0.169 Btu,
the
internal
the
pressure
of
17 ps a
in heat
energy units.
By application
of the
the constant
the increase
mathematical
coordinates,
the
thermodynamic
state
of
and
of
a
process
or
cycle
which
is
of
interest,
the
properties
used
as
in
Fig.
3-4.
Notice
along
the
horizontal
volume
axis
to
chart.
The
inter-
Since the
point
representing
line drawn through
as the
and its
that the
the
volume
to
as
 the
area
is
volume
is
kept
condition
1
to
the
final
It has been stated that no work is done during
a
process
gas
changes.
the volume.
as the gas is
be
absorbed
psfa
(b)
the
work is
equal to
process.
set up
to
condense.
4-4.
Subcooled
Liquid.
(20
psiaX
the
water
will
be
filled
water
vapor
molecules
(Fig.
water.
With
the
throttling
valve
opening
to
the
vessel at
will
be
exactly
falling
back
into
will
212
Saturation
is
vaporized
at
the
fluid
as
work.
In
Equation
4-1,
as
work
is
represented
enthalpy. Furthermore, even though the
external work
lb
a
this amount, only 897.6
storage in the
4-7.
4-19.
Entropy.
transferred
of entropy
the
zero
point
of
32°
F.
Again,
as
specific entropy
heat
of
entropy
pound per
abso-
lute
temperature,
of
refrigera-
or sink or it
temperatures of
feet
for
both
the
H
0.18455
1.169 90.58
0.19004
1.134
1.158
1.242 95.15
140 1.439 98.37 0.20254 1.361
98.32 0.20157 1.291
1.274
104.67
1.435 107.88 0.21592
1.365 107.82 0.21505
1.482 111.17 0.22085 1.411
112.84 0.22329
0.22662
117.99
117.90 0.22967
0.23379 1.601 119.65 0.23289 1.524
119.62 0.23204
0.23526
123.11
0.23675
300
1.762
Fig.
4-10.
Inc.
saturation. This
properties of the vapor at this
condition
can
be
obtained.
4-22.
a
illustrated in Fig.
any
Dalton's
law
of
that
in
any
mechanical
mixture
individual
as
the
dew
point
in the
air is
Solution.
From
It
long
as
the
will increase the pressure
the
point temperature.
amount of water vapor in the
air determines the
the maximum
possible
pressure.
Since
the
maximum
corresponding
to
the
will be
contained
water
vapor
air is
be
readily
computed.
humidity corresponding to
each of the
whereas the values
given in column
column
(3).
5-9.
Relative
Humidity.
saturated air at the
at that
5-8,
if
It has
as
of the
of the
of the air and
simulated
in
still
and one
rapidly in
the air
both the dry
and
being un-
affected by
Hence,
In order
the
water
difference
more
of
the
vaporization
the wick.
When the
temperature of
supply all
of the
tempera-
of heat
tem-
perature,
temperature for
various
temperatures
any vapor
anywhere along
are also
dry bulb,
and left
the total
air and
air
at
95°
F
DB,
Q,
of air
of
air.
Solution.
(a)
From
of
removed
per
liii
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8
S
of
1000
perature of
is
cooled
to
75°
is cooled
guishes
one
from
the
other.
6-2.
sensible,
said
refrigeratingeffectisto
be
or
Water temperature rises
the temperature
the space.
at
32°
drain
The
solid
refrigerants
most
frequently
employed
6-4) the heat
entering the refrigerated
with the
from
air
continues.
The
walls
and
stored
product
to
un-
restricted
pan must
applica-
lowered to
offrequently
replenishing
Insulation
Heat
leaking
through
insulation
perature
refrigerating system.
by regulating
vapor
vapor
vent
that the
pump.
space to
pressure
Fig.
6-7.
16-3.
6-9.
Maintaining
a
Constant
evaporator
6-8.
The
action
that the
is
the
evaporator
to
and
stop
the
which tend
latent
heat
from
the
air
normal temperatures.
the temperature
air or
water used
compressor
shown
in
Fig.
6-10
serves
point such that
since mechani-
the
refrigerated
the
high-pressure,
parts
is
the
low
the
it gives up
condenser fan.
heat to the cooler
the new
recirculated.
is
in
contact
with
the
compressor
cylinder
is
slightly between
resulting from the flow.
differential between the refrigerant
the
during
(Section 3-12). Therefore,
pressure.
The
discharge
vapor
is
hot-gas
line
and
through
whereupon the further removal of
heat from
means that
the
compressor
rate
of
vaporization
of
started, the
vapor pumped
the throttling
point where
denser
will
air
an
amount
effect of
its
vaporizing temperature in
the evaporator the
perature
corre-
sponding
to
from the
condensation is
up heat to
is
In any case,
approaching
the
the same as
liquid
transferred from the refrigerant to the control.
Therefore,
a
portion
of
con-
trol,
and
the
heat
evaporator temperature.
duces
no
liquid
(24
at the
the system
5 lb/min,
produced.
When
the
vaporizing
temperature
is
per
minute
(10
x
1.351).
In
must be
vaporized each
of
the
refrigerant
the
in
the
chart
and
the
vapor
in
the
the
saturated
liquid
is vapor.
liquid
curve
any
The
pressure
of
enthalpy.
In
the
constant
temperature
The
curved,
nearly
the chart,
properties
of
significance
of constant
about
chart in
ing temperature
is increased
to
120°
therefore
the
difference
in
the
compressed per
increases to
6.25
5.6
occurs
when
the
of compression per
the theoretical
temperature
condenser per
ing
heat
in
Section
7-7
minute per ton
that
Q
3
also
increases.
For
the
two
temperature, whereas the amount
a
the iso-
the
evaporator.
are the
various
0°
suction
the super-
cycle
is
greater
than
5.H5
-4.88
~^M~
X
10
and
medium,
a
special
capacity
series
with
the
liquid
being
subcooled
ture of the cycle
is
quantity
external
to
the
system.
8-8.
a
liquid-suction
the
best
possible
cycle
the
the
the
this point.
Despite the
 
The
liquid
line
and
the
whereas
preservation
Today's
in
outlying
areas.
sub-
sequent
storage
of hours, days,
products, particularly fruit
and vegetables, are
certain
available
the
year
round.
any know-
to
supplement
the
preservation.
For
instance,
(dried) fruit, milk, eggs, fish, meat,
potatoes, etc.,
sausage, toname only a
and often
products which
such
methods
quantities
to handle
a
distinctive
and
delicious
food
preser-
vation.
it
case
will
regardless
of
the
of
a
number
of
cells
which
are
positioned
single
mold
plant
is
capable
of
fruit
is
supply of food,
tion and complete
enzymes.
Rancidity
are less
products depends in
by
placing
which prevent
practical.
of
the
product.
9-17.
product is
at
Short-term
or
ex-
but
seldom
for
more
the
product
chillingperiod.
9-24.
rapidly once the
away the vapor
in
refrigerated
be taken
aluminum
foil,
glaze.
Too,
since
the
than 1
room. In
commercial fixtures.
gaining
becoming
cream,
dairy
design
ing
individual
products
Fig.
35 F
below
35 F
to
8
40F
-15
to
-20
F
Engineers.)
foot.
room
and
freezer
areas.
which follow deals
ordinarily include
the
con-
to melt
to
melt
be detrimental
determined directly in Btu per
hour.
10-3.
is
load is divided into four separate loads,
viz:
(1)
the
wall
to
is
cases,
usually
the
infiltration
load.
The
introduction
purposes. The term
the
an
Since
are
little, if any, leakage of air
around
level. The term product as used here is taken
to
reduced by
as
welding
electrodes,
masses
of
concrete,
plastic,
rubber,
The
importance
temperature
enters
the
below
the
usually
temperature. When such
temperature
and
other words, it provides
ating effect produced
ment resulting from product
the
though
there
case
the
product
equip-
coolers
where
cooled
to
the
continuous
and
is
usually
a
liquid
ment since there
the
product
a
these are
that human
a
tions where
the
conditioned
space,
such
as
wall
heat will
the
air
Btu per hour and
the wall and
to prevent as
storage walls should
be good thermal
U
the
with the temperature
of heat passing
the tem-
will
pass
through
a
wall
10
ft
clay
tile
with
4
in.
the
resist-
sides
the
resistances
so large
with relation
sufficiently
outside design
to be stored
is to be kept in
storage. recommended
walls located inside
perature. The outdoor
variations in the
clearance between
the top
the
is
treated
as
an
wall.
The
same
ably
less
surface
is
temperature
heat
gain
through
the difference
southwest
south and
tile
6
in.
corkboard
0.S
cement
ness of the
example,
The
space
heat
gain
introduced
purposes. When
space
in
a
the
inside
and
outside
hr by the
its
freezing
than
24
by
the
desired
chilled
to
a
high
chilling
insufficient capacity to carry the
load
during
The
products
are
will
show
that
load.
Equation
10-7
is
load
calculation
can
usage.
Normal
corkboard insula-
of
10 ft
56°
holding
storage.
13.5
ft)
is
calculation,
The
for
the
box
blast
carrying
the
poultry
a specific
tile
insulated
with
8
in.
of
corkboard.
and covered
is
=
353 indi-
normal. The
covered
with
outside
design
conditions
(anteroom)
are
50°
100°
apples are in
the storage
cooler at
is
control (Fig.
11-1). The
vapor accumulating
off
and requires a
with
the
vaporiring
refrigerant
inside.
With
the
finned
evaporator,
themselves
are
surrounding
tubes.
Atthough
accumulation
on
(ML
of cither
for
bulb
cpnireU
control.
the
various
shapes
to wear or get
between
two
edges (Fig. It
solution
or
evacuated
so
that
the
tubing inside. Those containing
the ceiling
or walls
ation system
capacity thui stored in
plates is controlled by
mounting
in
holding
The
plates
the
refrigerant
(Fig.
11-9)
or
they
may
be
conditions
are
encountered
holdover
the
the
tube.
in part on the
for
(two
and other installation* where the coil Optra ICi
it
temperatures
high
accumulates
On
the
coil
surface
may
have
as
in
general,
surfaces
I
to
air-cooling
applica-
maintained
above
34'
F.
rate at
or by
to the tube
in
creases.
lence
increases
with
coefficients
of
instance where
evaporator is limited
other hand,
in liquid-cooling
applications, since
liquid is
the
occurs, the use
rator
capacity
in
refrigerant
where the
metic mean temperature
in air
remains constant.
When this
is not
die case,
evaporator.
the
coil
thin film
Evaporator Capacity.
of
Except
in
evaporator,
evaporator at a
air results in uneven temperatures
and  dead
the
have
twice
the
surface
through
the
evaporator
is
the
minimum
through
the
circuit
per
is
100
circuit
evaporator
splitting
allowable
it would
not
unduly
affected.
Another
method
of
reducing
Another disadvantage
the
tubes
row)
than
across
is much greater than
through the
portion
effectively as the upper portion because wetting
of the internal tube surface will not
be as great
erant
percentage of
It is for
temperature of the
11-19
Refrigerant
in
Refrigerant
distributor
For
the
rating tables published
ever,
are known.
for
product
cooling
applications
ten
to
the stored product
with
11-1,
the
time
of
manufacture)
varies
directly with the temperature of
the air entering
temperature
of
the
air
when determining
by excessive
be
given
special
consideration.
Cut
be
af-
fected
by
high
velocities
and
the
rate
air
velocities
and
minimum
location of
of
air
the
to permit the
such
a
over
the
cooler.
Since
1-24,
the
Hf.
11-24.
Tvpkal
baflla
amngamaflt
for
natunl
conractlon
end
I.
in,
combina-
can
be
readily
applied
to
vection
Evaporators,
Basic
capacity
ratings
instances,
where
it
will
per inch of
rators, the ratings given are per square foot
of
of
the
plate
arc
of
evaporators
Enamels J M.
cool?
type
of
the
rating
(able,
cooler
#PK-I6
with
two
fin*
in.
(166
The
type, the
more than 12 in.
the
evapo-
-
shown
in
Fig
11-27.
Model
coolers.
Typical
ExampJ*
Example
10-16,
To
assure
ft x 16 ft) indicates that four to six evapo-
rators (two or three banks installed end-to-
end
over
that
plate
Three banks
adequate
Since the banks are
be deter-
mined by
bank.
cient
of
connections
desired
plate-stand assembly
Solution.
Inspection
of
Tabte
R-4
will
show
that
the
ratings
of
the
necessary to
at
a
IV
I
TD of
the
evaporator
having
a
capacity
design TD
Model
#1-72%*-%.
which
is
approximately
selecting
Sq
ft
per day,
instance is
of
plate)
plates have a total
(outside
surface)
at
the
given
TD,
of
I
J
in.
966
x
Z.3
circulation.
shown
reduced (Chapter
total
cooling
capacity
of
latent
cooling
the
unit
u.H)lcr
should
be
over
a
unit
eool*r d*ligni
directly
(Counety
Dunham-Bush,
Inc.)
cients, they are
certain point,
the fan motor resulting from the
increase
it)
cooler capacity
it
to
decrease,
load and must be
time,
ftg. IIO
Double-pipe
Spray-type
shell-and-tube
«nd AJr-CondltJoiUnt
shown
in
refrigerant circuit
designs of
double-
 
foaled
at
the
top
of
in
a
trough
at
the chilled
is open
chilling of
is
very
without
the
danger
occasional
Flf-
or si
a baffle arrangement. As
to circulate
at
the
other
cod.
in
Section
1
liquid-chilling
application
where
sanitation
is
1 1-37),
the
chiller
of
the
toads, tl is used primarily for the
chilling
of
water
disadvantages
event
the
to chill the
extent
adaptable
to
application.
For
the
mosi
widely
used
type.
and held
flooded,
the
shell .
the
level
of
the
number
Tube
dkmclem
lube
lengths
designed
for
use
with
refrigerant an
usually equipped
with copper
fumed
on
the
refrigerant
drillers
are
tonnage
instal-
lations
instal-
lations.
Il-M.
event
on
tube
huiidlcs.
ry
function
of
the
efficiency
of
the
liquid
the
amount
4-FHs
JOtiHh
a-ataa
2
Circuits
draws chilled liquid from
the storage tank at
tributor
flown
through
the
lubes.
paratively
thin
conven-
the liquid
the
chiller
from
where
it
upon the
manufacturer
for
the cooler outlet of
circulation
of
writer
heads
the
chiller.
chiller load in
drop
through
the
water column.
(inset). (Courtesy
zontally to
to
ducts
communicating
with
such
industrial
process
cooling
product.
The
latter
when
ammonia
is
calcium
process cooling
installations where
the temperatures
or through a water
dehumidified. In
nozzles
or
basin
to the basin
product
application where
tained is
below the
Brine
perature of
tration is increased
lowest.
A
solution
or
less than that which
is required for a
required
for
reached.
The
further
removal
of
calcium
chloride
brine.
tration in
chloride
brine
at
various
thermal
properties
of
both
satisfactory
of the
increases
as
the
salt
11-36.
Antifreeze
Solutions.
antifreeze
glycol, Methanol
in
solution
with
11-5.
noncorrosive.
air in a
11-46
and
11-47.
Reciprocating
Figure
1
2-2
is
a
time-pressure
suction
space acts
of the
the
203
of the
hot
gas
stroke. This part
the
be found by multi-
liquid
at
refrigerant
per
minute
conditions
is
known,
the
vapor
filling
the
cylinder
is
reasons,
the
actual
condi-
tions
which
is
drawn
capacity.
Solution
efficiency of the compressor, are the
following:
vapor
left
in
the
clearance
space
part
of
vapor before the suction valves
can
open
and
that
the
at the bottom of
is easily explained,
and
is
liquid is
liquid
is no
during
the
suction
regardless
of
clearance.
12-1
suction
pressure
experience a
valves
discharge
such
a
increased,
the
volumetric
efficiency
of area
of
come
the
spring
tension
suction vapor
experiences a
pressor
is
always
a
in
from
the
less than
if the
vapor filling
the
valves
be
actual
condensing
pressure.
The
vapor
left
expand from
been
is
reduced.
Unlike
volumetric
efficiency,
wiredrawing
is
and
the vapor through the valves
is
valves,
the
pumped
by
facturing
processes,
there
is
design valves that
head
of
compression stroke,
cylinder will flow
capacity
of
evaporator,
Weight of refrigerant
suction
the
compressor
accounts
for
for it. As
is
brought
about
by
effect of each
capacity
which
can
be
is more
the actual
for this
condensing
efficiency
of
by the
com-
capacity can
depends
reduces
compressor so
displaced
by
the
fore, even though the
per
reduction
Increasing th
temperature
ratio
and the
actual compressor
is
5.38
the
theoretical
refrigerating
capacity,
which
must
be
drive
temperature
Since
the
saving
horsepower required
by the
compressor in-
temperature
is
107%/
30°
not true,
50*
coincident with
power per ton.
condensing
temperature
of
12-10
of one
ture is
raised from
com-
pressor
is
1.52
x
1.76
=2.68hp
4.6
4.5
4-4
4.3
-S
pression cycle
from the
vapor
that
the
refrigerant
gas.
Notice
the process. In
the work done
piston by
accurate measure
referred
(Fhp),
so
that
(12-11)
Thp
(12-12)
Bhp
An
parison.
Pressures
P
1
Notice that at
vapor tends to
return to P
of
weight of
The
deviation
of
the
indicate
of the
and
dis-
is
being
admitted
to
compression
During
compression
stroke,
during
cylinder
walls.
12-24.
Isothermal
the work
for
the
refrigeration
cycle.
air
surrounding
the
compressor
having
heating is
reduced and
the vapor
has the
the formation
liquid are
computations
vaporized during the
is
not
of
time
and
since
is
the compressor
displaces
a
greater
volume
assumption
volumetric
efficiency
will
be
lower
because
cylinder heating
of modern
effect to a
or
a
low
suction
the amount
the refrigerating capacity
heating.
12-32.
Compressor
compressor
selection.
and rating
that both the
specify that
enter the
for
of
40°
F,
the
vapor entering
obtain the
given in Table R-10D correct the ratings to
a
listed.
tem-
and
ratings.
The
the
case.
be
under conditions
unusual
cases,
no
appreciable
usually
liquid
is
subcooled
subcooling.
in
the
preceding
To
select
a
compressor
for
a
of
the
oftheavailablecondensing
medium.
Methodsof
medium. Since
deter-
fan
selection
suction
temperature
and
on
the
entering
and
leaving
water
tempera-
air-cooled
given in
locate the desired
having a
compressor, Model #5F20, which has
a
capacity
of
34,000
Btu/hr
at
1450
rpm.
Example
12-13.
saturated
discharge
of 9340
system.
system
design
conditions.
system
design
conditions
perform satisfactorily.
pressor
unit, which
ever, to assure
proper system balance,
on
the
condensing unit capacity,
13-2.
the
preceding
paragraphs.
2.
the refrig-
fixed limits. Assuming that the design TD is
selected
is
humidity is
to be
also
problem
produce
satisfactory
In
the
event
that
keeping with
instance, since the problem
design conditions,
logical corrective
already
system
system capacity and thereby bringing it more
into line with
the calculated load.
 starve
the
velocity over
also
city
most
cases,
increasing
is
evident
also
that
some
provided. Other-
maximum,
excessive and the level
a
float
is
arranged
to
tank rises
falls to
on
a
capacity
maximum cooling load.
temperature of the space
or product can be
even under
the
case
of
to
permit
(the 24-hr
ment.
Stationary
contact
Bellows
Fig.
13-4.
Schematic
a
refrigerated
mecha-
tube
increases
the
which
or bulb
has
type
remain above
cut-in
temperature
of
the off cycles are
too
ice.
actuated
by
and
the
which actuates
the
thermostat
is
the
pressure
compressor,
points
pressure
When
the
certain,
predetermined
pressure,
and cut-in
the
suction
saturation temperature
evaporator, changes in
evaporator temperature in the same way that
the
remote-bulb
thermostat
saturation
pressures
thermostat employed in the
con-
trol
thermostat, the cut-in
evaporator
increases
to
the
line,
of
the
com-
pressor
cycle the compressor off when the pressure in
the
evaporator
make
an
nltowuiicc
for
the
temperature*
is too small
in no way
of
velocity
the
com-
pressor
cycles
cycles
temperature
control
for
applications
requiring
a considerable
between the
unit.
On
control is
located at
high-
pressure
control
unit,
employs both
pump-dawn
cycle,
perature
is
the
system
refrigerant
flow
is
low
breaks the
perature
of
immediately to
Chapter IS.
on
space temperature is high, I he
evaporator
TD
the
design
evapo-
Because of the higher evaporator
capacity,
the
suction
temperature
Hence,
the
average
design
conditions
requirements
of
the
lower
than
the
system
and capacity being highest
is
running
cycle
when
the
space
temperature
Is
lowest.
load cannot be
good
load. This is
sufficient capacity
periods
lendency
for
to
the
load.
In
the
preceding
sections.
the relative length
periods
when
be short, whereas
will
capacity
to
handle
the
maximum
load,
when
the
changes
substantial,
be
considerably
oversized
system
is
will
will
be
too
short
where
the
Frequently,
several
satisfaction of the latent load
will
the
temperature
necessary
hulb
temperature.
capacity
of
capacity
ihe
total
teijr
Ksrmind
the capacity
refrigerant
quantity
 depth
control
always
changes
of
the
evaporator
some in-
balance.
One
vary
the
speed
wide range by governor control of
the
com-
pressor
driver.
When
windings in the motor,
if*
JrttereoAnectad
w
tint
the
compressor
of the pressure control, the
solenoid
valve
is
art
used
to
unload
the
requirements of
the compressor
the
same
proportions.
Another
trolling
compressor
capacity
which
it
employed
pressors
cycle
off
in
sequence
as
to provide
Chapter
20.
be
streams.
In
con-
densers
may
added
until
repairs
the point
as the
water. Although
the condenser.
Example 14-1,
the total condenser load
or decrease
condenser
(sqft)
U
on
the
surface
area
of
of
condenser, the
capacity of
more,
viz:
(T
a
enced in
through the condenser
in
cfm
121,500
1.08
x
25
4500
cfm
densing medium flowing through
the
lower
(3)
the
temperature
a
a
small
rate. However, it should be recognized
that the
beyond
a
certain
power require-
the dimensions of
the chassis. Because
is installed
Because
of
on the
reduces
the
unit which
capacity.
14-7.
ship
between
the
the
condenser is
scribes the minimum air velocity that
will pro-
duceturbulentflow anda
condenser and results
in an unnecessary
or
blower
Fig.
14-3.
Remote
the condenser
The actual
minute
per
ton
usually
flow
rate.
Since heat transfer
tate
the
circuits through the
and
high
temperature
rise.
The
water
\y
\y
overcharge the system
denser will tend to cover too much of the
con-
installations up to approximately 10 tons
capacity,
Shelt-and-coil
water coils.
cylindrical
of
Construc-
tion
is
the
flooded-
densing water
Water
circulates
sheets and the end-piates, the
end-plates
being
the
passes the water makes
may be as few
For
any
given
of forty tubes, if
per
pass
is
twenty,
whereas
the number
It is
will
as
for
a
city the transfer coefficient will be higher for the
four-pass
condenser
and
given heat
circulate the water will be greater. Hence, for a
waste-
capacities
*
to mean that four-pass condensers are
undesirable
in,,
whereas
diameters of
condenser
six
cleaning
of
installations. The
to
the tubes and a drain at the bottom to carry the
water away. Bach tube is equipped at the top
with
a
refrigerant
the condenser
denser at
The height
are
from the
tures
of
102°
and
105^
F,
20
and
10
water
rise
exceed E fps which is 5.75 gpm per tube
for
It is necessary to
able.
to
be
to
Fig.
2,
Table
R-I4.
The
factor
obtained
obtain corrected tons.
and
may be obtained by reference
to Fig.
liminary selection
step 4 and
for
maximum weight
capacity
is
from
the
total
weight
of
=
= 92.4°
F
75°
Btu per hour
a
the
water
heat to
evaporates is
drawn from
air
will
possible to
of
the
wet
bulb
temperatures)
is
called
the
 range
of
the
tower.
Naturally,
to
denser water
approxi-
mated
by
or
forces
(blows)
14-13.
sprayed down
a
and
Too, since
ciency.
Spray
eliminators
must
Fig.
14-13
and
is
a
rating
tons
(compressor
capacity)
the
tower
(gpm)
2.
Design
peratures
(tower
cooling
Model
rate over
tower.
As
shown
in
172.6
gpm
temperature will
Therefore,
in
be
economically
by installing
by-pass,
a
that it
erate
condenser
and
tower
quantity of
removed
ment cannot be changed
by-pass will
may
Solution. From
gpm/ton and on
vation device
and is,
employed
in
and
returns
From
by
action
to
the
outside
some
cases,
are used. The
Stream
to
prevent
entrained
water
from
being
carried
14-17.
Although
rated
given
up
heat or latent heat
(moisture) in the discharge
effectiveness
bulb temperature of the entering air.
The lower
manufacturer and depends to
a large extent on
Generally,
practical
matter,
the
au
(ornate
bleed-off.
(Courtesy/
Refrigeration
Engln-
surface
thoroughly
approximately
15
lb
(2
(15,000/1000).
by
hour per
water used.
gal per hour per
are
through the desuperheating coils
receiver
for
these
conditions.
14-18).
The
to changes in
open
pressure decreases, the valve
the
usually be
considerably higher
When the compressor cycles off, the
water
through ihc condenser until the pressure
in
the
condenser
the
compressor
remains
the desired shut-off
range
Since
at the condenser location. Too,
the shut-off
enough
so
that
trol large enough to assure its proper operation.
The capacity of water regu Sating valves
varies
pressure
Water regulating valves are
In order
installed
piping
Table
R-18.
Solution
2. Closing point of
lower
denser
vary
temperature.
With
as to
city
is
less of the force
the static pressure
foot, if the pressure
(4.33
+ 14.696).
However,
established:
To
convert
velocity
head
WATER AND BRINE
static
and
velocity
to the
only the
this direc-
tion, the
head
of
and velocity
head
of
divided
between
velocity
of
inversely
with
cross-sectional
area
of
the
conduit.
per
second
A
B of
is
converted
to
increaser
into
units and are
connected together by
on
the
pump of
liquid handled
A charac-
is
asig m bl
selected from the manu-
of the static head and the
friction head.
tween the  free
lifted by
sys-
feet
feet
between
the
free
water
the
water
in
IngsrsoH-Rind
Company.)
apacity
in-
{CourtMy
the pumping head.
separately in
system,
in
computing
the
pumping
circuit,
as
in
the
entirely
use
circuit
having
greatest
head.
Gpm
(Courtesy
Ingersoll-Rand
Company.)
Converting
Example 15-3.
pump
power required by
the pump increases
15-11.
further
be
used.
Standard
weight
denser water
lated through
size
from
2
11.1ft),
a
from 3 to 4 in.
reduces the
9.4
ft
of
water
column
(11.1
of the available pump,
should be
water
column,
of
the
systems
the
friction
loss
the
65-ft
head,
the
permissible
other hand, for
pumping
of equipment
of water
at maximum loading—
period
of
offheat,
*
trade
name
pro-
prietary
or
extensively
material
normally
used
system.
16-3.
concentration
Table 16-7).
those
classified
from
284
to be
of occupancy,
even
a
highly
toxic
toxic
refrigerants
is
somewhat
infants and
leak on
control
and/or
will
prevent
Since free
water exists
in the
system only
when the
amount of
will
produce
corrosion.
is
necessarily
below
the freezing point of
In ammonia
water in
occur in systems
quality lubricating oils
with
the
refrigerant.
composition,
charge
line.
This
suction
lines.
Copper
plating
of
various
compressor
parts
is
often
generate
heat,
of
copper
plating
has
not
been
copper
plating
systems,
into
conditions
normally
found
slightly
so)
under
conditions
compressor
and
other
system
components,
resistance
the
viscosity
of
the
oil
principal reason
adhere
to
and
of
the
condenser
and
the evaporator is
pressor and not allowed to
circulate with the
the system.
through
made
with
points
from these
crankcase.
This
auto-
matically.
When
refrigerant
velocity
will
oil and
methods
of the oil
in
such
cases
is
flow control
in
oil
crankcase to
oil
in the
should be
line
oil
separators
be inadequate
removing
oil
from
the
refrigerant
vapor,
they
the
limited to those
of the
discussed in more
the system
the
general rule,
ones,
usually
with
the
of
sion.
The
presence
should also be installed in the system.
The necessity
and for
indicates the presence of
system
vapors
in other
present
that the
ditions is
power
dioxide cannot
pheric
pressure
nor
fore below this
critical
temperature
of
CO
a
(87.8°
F),
relatively
low
condensing
an anesthetic
to
which
it
between 8.1
in
favor
of
the
safer
aluminum,
compounds
nonferrous
systems
is
simplified
oil
compressor
taken
solution
which
chloride
vapor
may
has
a
gas
volume
of
the
vapor
handled
per
ton
mable. Because of
A halide
be used
conditions
are
However,
it
the relatively
tate the use
may be used for
compared
to
In
fact,
commonly
used
refrigerants.
A
13 is
 
compression
ratios
are
likely
the
Although miscible with oil
The
exact
When flooded evaporators
applica-
tions.
over Refrigerant-12 is the
Hence,
Too,
evaporator
tem-
temperatures and
ment per ton is somewhat high
(
required
per
ton
industrial
centrifugal
com-
pressors
composed
in
various
proportions
of
the
two
elements
hydro-
gen
and
basic
is
occurring
condenser.
17-2.
unresponsive to
on
the
system
is
relatively
use
expansion
valve
by flooding
face in response to
pressure is
maintained, regardless
characteristics of
until
viously
evaporator for
pressor cycles
is not removed
evaporator pressure will be
(a)
a
that
evaporator be
is
sion
designed
compressor off
load
critical
point.
Obviously,
since
portion
capacity
system
at
a
time
when
evaporator
pressure
is
temperature
consider-
able
35 40
45 50
efficiency under heavy
operating
temperature
of
the
compressor
of
the
compressor,
condenser in
order to
maintain the
its ready
expansion
constant
degree
of
case
of
the
evaporator,
suction
valve
can
Pressure
charged
mechanical
cartridge
vapor lo cool
before the valve
those
of
gas-charged
expansion
Is
refrigerant.
is
always
so that at
liquid
will
have
vaporised
and
the
bulb
charge
of
the
bulb, the
the case of
also
pressure
CP
2
of 25 psig
have very little
In this
time
changes in the
limiting valves.
Since the
the maximum
operating pressure
of the
to the
power head
coldest
point
and
tive because of the
bulb (Fig. 17-14).
that many refrigeration systems are subject
to
occasional
 pull-down
under
normal
compressor
power to carry
particular installation.
load
load
to
limit
motor,
thereby
reason
the pressure-temperature relationship of
12 is shown
Fig.
17-15.
The
mixture
leaving
the
valve
losses.
position.
tubes connecting the distributor
gas from the
in
Fig.
17-20.
bulb.
the distributor as
bulb
should
be
entire length
of the
out of die
air
problem.
Since
a
trapped
or
from the evaporator so that oil and
liquid
will
section of
no
installed
to
line
superheats
are
be
influenced
by
line from
evaporator
is
saturation temperature of the
piping.
(Courtesy
range.
For
External
tributors
are
employed,
to
compensate
for
passing
In any system, with
system. On
systems without
drop
and
either case.
loss is in the
feeder tubes
or to
or
type
pressure drop through
the evaporator is
expansion
valve
system design
60
50%
or
more
fed
portions
system
fall
so
floatchamber
drops,
17-40.
A
typical
application
of
a
low
pressure
float
pilot
is
shown
admit
more
energized and
main valve port.
that
closed).
defrosting
suction
desired minimum.
modulates toward the open position so that at
full load the regulator is in the
full open
or temperature
section.
operated liquid control
evaporator
pressure
suction
compressor driver
was selected.
gas
defrosting
or
reverse
pressures.
Like
evaporator
pressure
as
sixteen.
or W pattern.
being located
As
However, a
the factors
 
the
spaces, the
or  flaps
to cover
bolt
through
piston
is
illustrated
in
Fig.
18-10.
18-*.
Valve
Location.
As
previously
de-
scribed,
through the
at this point.
only the tension of the coil springs in order to
allow ibc ends of the reed (o
move
as
the
reed
loaded
beam
also
act.';
protect
the
compressor
valves
are
designed
sufficient clearance to pass a slug of liquid of
any bind.
tion.)
open.
(b)
Pon
the
available
valve
area.
the
rpm
and
For example, a compressor ha ving a 4 in. stroke
and rotating at
piston velocity
will have
of
*
an
exceeding
allowable
piston
velocities
depends
permissible
[pax
that the
is
further
will be greater
the
individual
compressor.
Although
than that of
and a short
discharge valves are both located in the head,
a
order
to
limited somewhat
means
need
compressor
valves
vapor
stroke
in
order
ment
per
cylinder.
Cylinder
approximately
industrial
types,
18-12.
constructed
bearing-
journals
general rule,
the crankshaft
lo
the
babbit.
The
eccentric-type
shaft,
compressors.
The
connecting rod completely
face.
Connecting
aluminum, forged
are
the
rod-
Bronze,
aluminum,
case-hardened.
into
the
crankcase
crankshaft passes
cylindrical
part
of
the
bored
to
an
inside
of
packing
rings,
placed
the stuffing box
between the shaft
to swell
the rings
seep
around
duty
auto-
crankcase
pressures.
vacuum when
must be
Although
there
are
a
seal nose which
sealing
(2)
18-14.
Compressor
Lubricating
Oils.
The
of
be
function
continuously
and
effectively
without
under-
remains in these units throughout the life
of
the
and resist
of
to
the
amount
of
service,
a
from a
temperature
at
or  pour, when tested
because
for
low
tem-
oil
tends
to
evaporator
efficiency.
returned
to
any oil if
to a
at which the wax begins to
precipitate
from
the
Jf the
cloud point of the oil is too high, wax will
precipitate from the oil in
the evaporator
the result that the system will
become
Inopera-
tive,
oil is
mixture of
oil
and
affects
of
10%
exceeds
10%
Because floe point
when mixed with an oil
soluble it
at
of the resistance
to cause an electric
immersed
in
that tbc oil is
ally
important
in
oils
strength may contribute to
lubri-
measure of the  body of the oil
or of the
compressor,
and preventing wear. In order to provide
adequate lubrication for
maintained within
too low, the oil wilt not have
sufficient body
lubrication
sive wearing
of the
between
in
pistons
when the
friction will be excessive and ihc
power con-
Furthermore,
in
oil
will be inadequate.
having
100°
F
TemparatUfa F
operating
temperature
range
available. When
13-13
guide.
18-19.
size
general
even in
vertical, enclosed
compressors up
Above
this
compressor,
compressor crankcasc acts as an oil sump and
is filled
even
140
connecting rod
bearings.
by
gravity
down
into
the
the
wrist-pin
bearings.
connecting
times called flooded lubrication, employs
slinger rings, discs, screws,
level
is allowed to
channels to the various rubbing surfaces (Fig.
6-14). This method is particularly suitable for
small,
violent
splashing
of
In
and connecting rods to the various rubbing
 
a
sump
located
of
pumps
are
automatically
reversible,
the
direc-
critical
or crankcase
bearings.
Although
In
cation system is entirely
In
the
first
place,
in
the
and
cause
foaming
that the
amount of
ASKE
system employing
an oil
miscible refrigerant,
contact
the
most
part
the
refrigerant,
(2)
the
that
the
two
is
100
20 psi, the
maximum percentage of
mixture in
as
42%.
that during
on
Refrigerant-
1
2
system
the
crankcase
cools
to
a
temperature
of
BO
F-
liquid
At
refrig-
-refrigerant
mixture
a
few
short time will cause
considerate
foaming
and
the
crank-
refrigerants,
impingement
before
60
Flf.
I6-)S.
Temperature-pTeMure
linn.
case
for this
the refrigerant
returns
to
the
come on
crankcase
warm
during
oil
cannot be
turned off
is
before the compressor
cycles off. The
used to
serve
as
supports
cylinder
on
opposite
suction
and
and
side and between
the
roller
travels
which
in
a
housing
pressure vapor is
check of
eliminate
back-feeding
and
placed in
prevent
the
high
rolor shaft is
oil film at this point. Directly Opposite this
point
cylinder
wall
is
shaft.
The
slots
as
they
follow
the
of
the
loaded to obtain a more positive
seal
the
cylinder
wall.
The
through ports
This
type
the
use
of
pressor
cycles
off.
displacement machines, because of their rotary
motion
pression losses resulting from blow-by around
the compressing element, back leakage through
valves, cylinder heating, clearance,
rotary compressors
of the
as booster
been utilized
I(>11.
Centrifugal Compressors-
The centri-
of impeller wheels
enclosed
in
a
cast
(Fig.
The
number
of
impeller
large
the
blades
or
vanes
gal
fan
or
along
of
the
centrifugal
high
velocity
vapor and direct the
a dis-
through the discharge line to
the condenser.
the
vana-type rotary
compressor. (Courtesy
imparted
to
exerted
impeller
wheels
lower
both the
head
developed
y%
N
V
per
Ib'cu ft
refrigerant
of
given
density,
impeller
blades,
being proportional to
with
increase
necessary pressure increase, in which case com-
pression of the vapor
vapor passes from
Assuming equal vapor
pressure
increases
fluid
the
speed
pression
ratios,
fully in
refrigerants
employed
with
centrifugal
capacity is
frames
small
requirements, and other characteristics
application.
80%
as
well
over
30%
losses
in
a
centrifugal
and fluid friction.
without
an
of one
wheel to
the inlet
of the
vapor
mum loss of energy. When diffuser vanes
are
13-25,
seals
rotor
and
the
con-
stationary
partitions
(Fig.
1
S-26),
the next
quantity of
the pockets. The leakage through the labyrinth
seal
shaft sealing strips and the
compressor
housing
charge
side
of
the
impeller
wheels
develop an axial thrust toward the
suction inlet
 
shaft
lubri-
oil.
The
from
the inboard
perature during
lubrication
a
there arecertain
50 40
30 20
Per
cent
speed
corresponding
of
to
reach
its
reduced
until
a
capacity
balance
is
obtained
between
in
capacity
shown
 
reciprocating
compressor
is
approximately
pro-
(2)
to changes
the centrifugal compressor, and the
resulting
since very
temperatures, the
refrig-
18-33.
Except
to the
evaporator temperature
is
to
are suitable
a
expensive than
to
corrosion.
welded,
brazed,
screw
connections.
should be
for
refrigeration
duty.
the
suction
mini-
mum
the
riser must
and
back
to
the
compressor.
The
risers
pipe sizes
pipe
in
square
at a
in
a
2°
F
drop
psi,
whereas
for
in the
by
balance
is
46.8
x
144
6.81
increasing the
will
be
46.8
balance of the suction
balance of
down should
an
area
of
low
sufficient to
entering the
overfeeding
liquid
19-4),
since
all
level
of
into
the
19-10
and
19-11.
19-9.
Discharge
Piping.
Sizing
of
the
dis-
charge
suction
line
or
state,
contains a 20
line
must
be
maintained
above
the
saturation
the over-all
to
of
liquid
subcooling
will
be
any
individual
Pressure
only
from
Tables
height limitation may
excessive
or
(4)
any
system
or
vapor, are
caused to
The oil then drains
of the
separator, from
where it
to the
compressor crankcase
cooled below
 
through the separator
is the
is rather
located
reasonably
close
to
the
compressor.
separator.
This
separator
and
causes
the
float
to
open
ammonia
systems
to
amount
all
receivers,
evaporators,
permit
a
measured
amount
be adjusted. The
Since Refrigerant-12
point
relatively low, there
liquid refrigerant
through the suction
placed on
centri-
reciprocating type.
of the
the
centrifugal
compressor.
18-25.
Capacity
(2}
suction throttling damper, or
these methods
stant speed
centrifugal
refrigerating
the
centrifugal
compressor,
condensing
Where
the
result*.
suction
and
dis-
charge
piping
approximately
30
pipe
diameters
light glisi.
are open
the
accumulation
of
foreign
material
in
the
most
part
system.
is
dosed .
Under
no
circu
msiances
same lime,
be (rapped in
pressures,
and
valves
in
Fla.
lf-21.
Sidt
outl«
An(ta
tvpa
ihe com-
controls
to the compressor
hi hiis the use of
gate
valves
in
refrigerant
lines,
are used primarily
I ines. Gate vn
order
to
permit
m
Fl|.
It-Jt.
from
ihe
bottom
of
the
receiver.
Mf.
and
charge line
3
Type
piping,
determine:
(a)
suction
pipe
at
surface
has
evaporator,
determined
can be
heat used to melt off
the
a level well
in order
the
the space
is usually
after
which
When several evaporators connected to
the
liquid line of the evaporator being
defrosted.
a
388
vection
evaporators
started
around
midnight
it is usually
(Courtesy
Dunham-Bush,
Inc.)
after
which
the
evaporator
fans
erated space.
2. The
draining of
in the
drain line,
line
rapidly as
drain line
through the drain
not
necessary. Since
not diluted by
started
and
stopped
in the
not
blown
way
the
refrigerant
control.
Some
of
compressor
recirculation,
system
is
completely
defrosted.
Another,
slug
of
liquid
refrigerant
will
return
to
the
com-
pressor
and
the defrost
pressor.
distinguishing
to
re-evaporate
in
the
suction
the evaporator
are
stopped
The
returned
defrost cycle
that con-
the
defrost
Normal
Operation
to
operation
and
defrosting
C,
the
compressor
with
and efficiency
into
expansion
intercooler,
is
with
from
the
condenser
is
subcooled
of the
important in
is
usually
usually
the
discharge
temperature
the
high
stage
compressor.
refrigerants
to
To evaporator
high stages
the
cascade
condenser,
system. On the
in a
considerable reduction
design of the
incurring
excessive
losses
in
not
in
intercooier
transformers
voltages by
minus
10%
of
can be operated
motor
are:
1.
The
is relatively
free of
dust and
moisture, the
motor
may
be
A four-pole, three-phase
When the stator
is energized, three
windings and produce
windings
establish
a
poles
rotating
stator
of the rotor
winding would be
than cutting
would be induced
 magnetic slip
the greater
decreases,
synchronous
of
the
motor.
The
starting
instant
to
the
motor
terminals.
motor
is
the
are
short-circuited.
are designed for
with
the
load.
21-5.
Synchronous
Motors.
which
make
up
starting torque-starting
current characteristics.
the load-carrying
condition
occurring
and
three-phase squirrel
referred
in the
stator of
running windings
split-phase type
a
rotating
rotor to rotate.
available
blowers,
the capacitor
capacitor
in
series
with
can
be
starting
from
Construction of the capacitor start and
run
starting, the
widely used as
capacitor is
starting capacitor.
provide
very
mounted
directly
motor
is
require
a
each stator
field of
j%j
small
fractional
horsepower
units,
the
unit.
starts. Three types
(2)
the
acts
to
remove the
starting winding
Fig.
at
the
instant
of
starting
currents heats the wire
the circuit.
After the
running winding will
of the wire and
motor draws
 M,
removing
21
depends
on
the
motors. It is a magnetic type relay and is
actuated
by
the
change
is
turns of large wire,
the running winding.
as shown in
causes
and
close
the
energized,
the
a
current
armature,
whereupon
opens
the
motor
starts
the voltage
in the
considerably
21-126.
The
contacts
of
 
circuit.
This
to operate
tarily falls
However,
if
the
oil
restarted,
of
flow
through
the
holding
coil
are
energized.
the alloted time,
compressor.
Multiply
1075.2 1076.2
54 0.20642
0.4203 0.01603
1086.3 0.0478
1086.7
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143.0°
95.1
155.0°
96.3
166.5°
97.3
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138.0°
94.3
150.5°
95.5
161.5°
96.6
-20°
135.5°
93.7
147.0°
94.8
157.5°
95.8
-10°
131.6°
93.1
143.0°
94.2
154.0°
95.2
0°
128.5°
92.6
141.0°
93.7
152.0°
94.8
10°
126.5°
92.1
137.5°
93.2
148.5°
94.3
20°
124.0°
91.7
136.0°
92.8
147.2°
93.9
30°
122.0°
91.4
133.5°
92.5
146.0°
93.6
40°
120.0°
91.1
132.5°
92.2
143.5°
93.2
50°
118.0°
90.8
131.0°
92.0
142.0°
92.9
0.040 0.035
Corkboard
foot per degree
Type of
per
cu
get a
Cubic
60
65
0.65
0.85
1.12
0.93
1.93 2.22
ducts
Changes
cuft
per
Edition,
by
24 hr
of
permission of Carrier
0.5
40d
X X
M 047
10a
Sprouts
Loag
IX
Chill
ISO
Chill
Start
2».7
150
tod
Fran
Short
Chill
Start
Chill
Flnlih
35
42
32
35-40
05a
05
OS
05-90
25.2
33.4
22.3
40
to
tOd
From
Carrier
Design
Data.
Reproduced
by
permission
refrigerated
space.
3
For
use
when
motor
Heavy
79
454 490
525 560
S8S8S
SSS2S
S5SS3
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10
8.03
9.08*
68.3
14
58.36 70.3
25.2
1.200
+32.0
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Vol
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5
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table.
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95°
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temf
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