Presented by
Eugene Silberstein, M.S., CMHE, BEAP
Suffolk County Community College
Cengage Learning
HVAC EXCELLENCE EDUCATORS CONFERENCE
SOUTH POINT HOTEL & CASINO
MARCH 31 – APRIL 2, 2014
If we change the way we
look at things, the things
we look at change
SIX
Chocolate Pudding
1 x 1 x 72 74
2 x 2 x 18
1 x 2 x 36 39
2 x 3 x 12
1 x 3 x 24 28
2 x4x9
1 x 4 x 18 23
2 x6x6
1 x 6 x 12 19
3 x4x6
1 x8x9
3 x3x8
18
22
17
15
14
13
14
Pressure (psia)
LINES
LINESOF
OFCONSTANT
CONSTANTENTHALPY
PRESSURE
P
R
P
E
R
S
E
S
S
HEAT CONTENT DECREASES
U
S
R
U
E
R
D
E
R
R
O
I HEAT CONTENT INCREASESP
S
S
E
S
Btu/lb
Heat Content
Pressure (psia)
SATURATION CURVE
Btu/lb
Btu/lb
Heat Content
THE SATURATION CURVE
• Under the curve, the refrigerant follows the
pressure-temperature relationship
• The left side of the saturation curve
represents 100% liquid
• The right side of the saturation curve
represents 100% vapor
• For non-blended refrigerants, one
pressure corresponds to one temperature
Pressure (psia)
LINES OF CONSTANT TEMPERATURE
Btu/lb
Heat Content
Pressure (psia)
LINES OF CONSTANT VOLUME (ft3/lb)
Btu/lb
Heat Content
Pressure (psia)
LINES OF CONSTANT ENTROPY
Btu/lb
Heat Content
Pressure (psia)
LINES OF CONSTANT QUALITY
Btu/lb
Heat Content
Pressure (psia)
PUT IT ALL TOGETHER…
Btu/lb
Heat Content
Pressure-Enthalpy (p-h) Diagram for R-12 (Simplified)
Pressure
(psia)
160°F
140°F
221
120°F
172
100°F
132
80°F
99
60°F
72
40°F
52
20°F
36
0°F
24
12
20
25 31
35
8
0
Enthalpy in btu/lb (Heat Content)
8 8
2 4
8 8 9 9
6 8 0 2
9 9 9
4 6 8
1 1 1
0 0 0
0 2 4
1 1
0 0
6 8
Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified)
Pressure
(psia)
160°F
140°F
352
120°F
275
100°F
211
80°F
159
60°F
117
40°F
84
20°F
58
0°F
39
15
24 31
40
46
Enthalpy in btu/lb (Heat Content)
1
1
0
1
1
2
1
1
9
1
2
3
Pressure-Enthalpy (p-h) Diagram for R-410A (Simplified)
Pressure
(psia)
160°F
140°F
557
120°F
434
100°F
334
80°F
251
60°F
186
40°F
133
20°F
93
0°F
63
13
28
21
45
37
53
123
133
140
143 148 152
Enthalpy in btu/lb (Heat Content)
REPEATING vs. NON-REPEATING CYCLES
CONDENSER
Liquid
Vapor
High Pressure
High Temperature
High Pressure
High Temperature
METERING DEVICE
COMPRESSOR
Low Pressure
Low Temperature
Low Pressure
Low Temperature
Liquid
Vapor
EVAPORATOR
Subcooled Liquid
Saturated Refrigerant
Superheated Vapor
CONDENSER
METERING DEVICE
COMPRESSOR
EVAPORATOR
Pressure
Subcooled Region
Superheated Region
Saturated Region
Heat Content
Pressure
Heat Content
Pressure (psia)
Btu/lb
Heat Content
Height Above Saturation
Saturation
VAPOR
LIQUID
Saturation
VAPOR
LIQUID
Distance Below Saturation
Pressure (psia)
Btu/lb
Heat Content
PUT IT ALL TOGETHER…
Pressure (psia)
A
E
B
C
Btu/lb
D
Heat Content
PUT IT ALLdischarge
TOGETHER…
E toPressure
A: CONDENSER
(Including
and liquid line)
(psia)
A to B: METERING DEVICE
B to C: EVAPORATOR
C to D: SUCTION LINE
D to E: COMPRESSOR
A
E
B
C
Btu/lb
D
Heat Content
NET REFRIGERATION EFFECT
The portion of the system that provides the desired
cooling or conditioning of the space or products being
treated.
A
B
E
C
D
NET REFRIGERATION EFFECT
• The larger the NRE, the greater the heat
transfer rate per pound of refrigerant circulated
• NRE is in the units of btu/lb
• Cooling effect can be increased by increasing
the NRE or by increasing the mass flow rate
• The cooling effect can be decreased by
decreasing the NRE or by decreasing the rate
of refrigerant circulation through the system
NRE Example
• Heat Content at point B = 35 btu/lb
• Heat Content at point C = 85 btu/lb
• NRE = C – B = 85 btu/lb – 35 btu/lb
NRE = 50 btu/lb
• Each pound of refrigerant can therefore
hold 50 btu of heat energy
• How many btu does it take to make 1 ton?
How Many btu = 1 Ton?
• 12,000 btu/hour = 1 Ton = 200 btu/min
• From the previous example, how many
lb/min do we have to move through the
system to get 1 ton?
• 200 btu/min/ton ÷ 50 btu/lb = 4 lb/min
• We must circulate 4 pounds of refrigerant
through the system every minute to obtain
one ton of refrigeration
• Mass Flow Rate Per Ton
NRE and MFR/ton
• The NRE determines the number of btu that a
pound of refrigerant can hold
• The larger the NRE the more btu can be held
by the pound of refrigerant
• As the NRE increases, the MFR/ton decreases
• As the NRE decreases, the MFR/ton increases
• NRE = Heat content at C – Heat content at B
• MFR/ton = 200 ÷ NRE
• Cool, huh?
THE SUCTION LINE
The line that connects the outlet of the evaporator to
the inlet of the compressor. This line is field installed
on split-type air conditioning systems.
A
B
E
C
D
SUCTION LINE
• The suction line should be as short as possible
• The amount of heat introduced to the system
through the suction line should be minimized
• Damaged suction line insulation increases the
amount of heat added to the system and
decreases the system’s operating efficiency
• Never remove suction line insulation without
replacing
• Seal the point where insulation sections meet
A
B
E
CD
D
E
HEAT OF WORK
The quantity, in btu/lb that represents the amount of
heat that is added to the refrigerant during the
compression process.
A
B
E
C
D
HEAT OF WORK (HOW)
• The HOW indicates the amount of heat added
to a pound of refrigerant during compression
• As the pressure of the refrigerant increases, the
heat content of the refrigerant increases as well
• Heat gets concentrated in the compressor
• As HOW increases, efficiency decreases
• As HOW decreases, system efficiency
increases
• HOW = Heat content at E – Heat content at D
HEAT OF COMPRESSION
The quantity, in btu/lb that represents the amount of
heat that is added to the system, outside of the
evaporator
A
B
E
C
D
HEAT OF COMPRESSION (HOC)
• The HOW indicates the amount of heat added
to a pound of refrigerant outside the evaporator
• Comprised of the HOW and the suction line
• As HOC increases, efficiency decreases
• As HOC decreases, system efficiency
increases
• HOW = Heat content at E – Heat content at C
TOTAL HEAT OF REJECTION
The quantity, in btu/lb that represents the amount of
heat that is removed from the system. THOR includes
the discharge line, condenser and liquid line.
A
B
E
C
D
TOTAL HEAT OF REJECTION (THOR)
• THOR indicates the total amount of heat
rejected from a system
• Refrigerant (hot gas) desuperheats when it
leaves the compressor (sensible heat transfer)
• Once the refrigerant has cooled down to the
condensing temperature, a change of state
begins to occur (latent heat transfer)
• After condensing, refrigerant subcools
• THOR = Heat content at E – Heat content at A
• THOR = NRE + HOC
SUBCOOLING & FLASH GAS
•
•
•
•
•
Subcooling is a good thing, right?
Flash gas is a good thing, right?
Are flash gas and subcooling related?
How can we tell?
Stay tuned...
HIGH SUBCOOLING....
(Only a slight Exaggeration)
A
B
E
C
D
What happened to the amount of flash gas?
LARGE AMOUNT OF FLASH GAS....
(Only a slight Exaggeration)
A
B
E
C
D
What happened to the subcooling?
SUBCOOLING & FLASH GAS
• Subcooling and flash gas are inversely
related to each other
• As the amount of subcooling increases,
the percentage of flash gas decreases
• As the percentage of flash gas increases,
the amount of subcooling decreases
COMPRESSION RATIO
Determined by dividing the high side pressure (psia)
by the low side pressure (psia)
High-side pressure
Low-side pressure
A
B
E
C
D
COMPRESSION RATIO
• Represents the ratio of the high side pressure
to the low side pressure
• Directly related to the amount of work done by
the compressor to accomplish the compression
process
• The larger the compression ratio, the larger the
HOW and HOC and the lower the system MFR
• The larger the HOW and HOC, the lower the
system efficiency
• Absolute pressures must be used
ABSOLUTE PRESSURE
• Absolute pressure = Gauge pressure + 14.7
• Round off to 15, for ease of calculation
• Example 1
– High side pressure (psig) = 225 psig
– High side pressure (psia) = 225 + 15 = 240 psia
– Low side pressure (psig) = 65 psig
– Low side pressure (psia) = 65 + 15 = 80 psia
– Compression ratio = 240 psia ÷ 80 psia = 3:1
Low Side Pressure in a Vacuum?
• First, convert the low side vacuum pressure in
inches of mercury to psia
• Use the following formula
 (30” Hg – vacuum reading) ÷ 2
• Example
– High side pressure = 245 psig
– High side pressure (psia) = 245 + 15 = 260 psia
– Low side pressure = 4”Hg
– Low side (psia) = (30”hg – 4”Hg) ÷ 2 = 13 psia
– Compression ratio = 260 ÷ 13 = 20:1
Meet Tammy…
90th Floor
2 Lawyers + 1 Tammy = Wasted Time
2nd Floor
Tammy’s 8-Hour Day
•
•
•
•
•
•
•
•
9am – 10 am
10am – 11am
11am – 12 noon
12 noon – 1pm
1 pm – 2pm
2pm – 3 pm
3 pm – 4 pm
4pm – 5 pm
Work on 2nd Floor
Walk up
Work on 90th Floor
Walk down
Lunch
Work on 2nd Floor
Walk up
Work on 90th Floor
Hmmmmmmmmmmmm
• What if the law firm moves its 90th floor
office to the 3rd floor?
• How will this affect Tammy’s productivity?
• Will she do more work? Less?
• What the heck does this have to do with
air conditioning?
• How many licks does it take to get to the
chocolaty center of a Tootsie Pop?
If Tammy’s office moves from
the 90th floor to the 3rd floor, we
get something like this….
Tammy’s 8-Hour Day
•
•
•
•
•
•
•
•
•
•
•
•
•
•
9:00 am – 10:00 am
10:00 am – 10:05 am
10:05 am – 11:05 noon
11:05 am – 11:10 am
11:10 am – 12:10 pm
12:10 pm – 1:10 pm
1:10 pm – 1:15 pm
1:15 pm – 2:15 pm
2:15 pm – 2:20 pm
2:20 pm – 3:20 pm
3:20 pm – 3:25 pm
3:25 pm – 4:25 pm
4:25 pm – 4:30 pm
4:30 pm – 5:00 pm
Work on 2nd Floor
Walk up to 3rd Floor
Work on 3rd Floor
Walk down to 2nd Floor
Work on 2nd Floor
Lunch
Walk up to 3rd Floor
Work on 3rd Floor
Walk down to 2nd Floor
Work on 2nd Floor
Walk up to 3rd Floor
Work on 3rd Floor
Walk down to 2nd Floor
Work on 2nd Floor
Office Comparison
• 2nd Floor  90th Floor
– 4 hours of work
– 3 hours of walking up
and down the stairs
– 1 hour lunch
– Day ends on the 90th
Floor
• 2nd Floor  3rd Floor
– 6 ½ hours of work
– 30 minutes of walking
up and down the stairs
– 1 hour lunch
– Day ends on the 2nd
Floor
Which is better?
COMPRESSION RATIO
• Lower compression ratios  higher
system efficiency
• Higher compression ratios  lower
system efficiency
• The closer the head pressure is to the
suction pressure, the higher the system
efficiency, all other things being equal and
operational
Causes of High Compression Ratio
(High Side Issues)
•
•
•
•
•
•
Dirty or blocked condenser coil
Recirculating air through the condenser coil
Defective condenser fan motor
Defective condenser fan motor blade
Defective wiring at the condenser fan motor
Defective motor starting components
(capacitor) at the condenser fan motor
Causes of High Compression Ratio
(Low Side Issues)
•
•
•
•
•
•
•
•
•
Dirty or blocked evaporator coil
Dirty air filter
Defective evaporator fan motor
Dirty blower wheel (squirrel cage)
Defective wiring at the evaporator fan motor
Closed supply registers
Blocked return grill
Loose duct liner
Belt/pulley issues
THEORETICAL HORSEPOWER PER
TON
• Determines how much compressor horsepower
is required to obtain 1 ton of cooling
• The ft-lb is a unit of work
• The ft-lb/min is a unit of power
• 33,000 ft-lb/min = 1 Horsepower
• The conversion factor between work and heat is
778 ft-lb/btu
• 33,000 ft-lb/min/hp ÷ 778 ft-lb/btu =
42.42 btu/min/hp
THEORETICAL HORSEPOWER PER
TON
• THp/ton = (MFR/ton x HOW) ÷ 42.42
• For example, if we had a system that had an
NRE of 50 and a HOW of 10, the THp/ton
would be:
THp/ton = (200/NRE) x HOW ÷ 42.42
THp/ton = (200/50) x 10 ÷ 42.42
THp/ton = 4 x 10 ÷ 42.42
THp/ton = 40 ÷ 42.42
THp/ton = 0.94
THp/ton Example
• If we had a 20-Hp reciprocating compressor
and the THp/ton calculation yielded a result of
2 hp/ton, what would the expected cooling
capability of the system be?
What Affects the THp/ton Number?
• The Net Refrigeration Effect (NRE)
• The Heat of Work (HOW)
What Affects the NRE and HOW?
•
•
•
•
•
•
Suction pressure
Discharge pressure
Compression Ratio
Airflow through the coils
Blowers and fans
And so on, and so on, and so on, and so on….
Get the Picture?
MASS FLOW RATE OF THE SYSTEM
• The amount of refrigerant that flows past any
given point in the system every minute
• Not to be confused with MFR/ton
• MFR/system is the actual refrigerant flow,
while MFR/ton is the flow per ton
• MFR/system can be found by multiplying the
MFR/ton by the number of tons of system
capacity, or
MFR/system = (42.42 x Compressor HP) ÷
HOW
COOL STUFF
• As the HOW increases, the MFR/system
decreases, and vice versa
• As the Compression Ratio increases, the
HOW increases
• As head pressure increases, or as suction
pressure decreases, the Compression
Ratio increases
• As the MFR/system decreases, the
capacity of the evaporator, condenser and
compressor all decrease
• Let’s take a closer look…
EVAPORATOR CAPACITY
• A function of the MFR/system and the NRE
• The MFR/system is in lb/min, the NRE is in
btu/lb and the capacity of the evaporator is in
btu/hour
Evaporator Capacity = MFR/system x NRE x 60
Btu
Hour
Lb
Min
Btu
Lb
60 Min
Hour
EVAPORATOR CAPACITY
• If the NRE or the MFR/system decreases,
the evaporator capacity also decreases
• The “60” is a conversion factor from
btu/min to btu/hour, given that there are 60
minutes in an hour
• Divide the evaporator capacity in btu/hour
by 12,000 to obtain the evaporator
capacity in tons
CONDENSER CAPACITY
• A function of the MFR/system and the THOR
• The MFR/system is in lb/min, the THOR is in
btu/lb and the capacity of the condenser is in
btu/hour
Condenser Capacity = MFR/system x THOR x 60
Btu
Hour
Lb
Min
Btu
Lb
60 Min
Hour
COMPRESSOR CAPACITY
• A function of the MFR/system and the
Specific volume of the refrigerant at the inlet
of the compressor
• Calculated in cubic feet per minute, ft3/min
Compresser Capacity = MFR/system x Specific Volume
ft3
Lb
ft3
Min
Min
Lb
COEFFICIENT OF
PERFORMANCE (COP)
• The ratio of the NRE compared to the HOC
• If the HOC remains constant, any increases
in NRE will increase the COP
• If the NRE remains constant, any decrease
in HOC will increase the COP
• The COP is a contributing factor to the EER
of an air conditioning system
• COP is a unitless value
COP EXAMPLE
•
•
•
•
•
•
•
Heat content at point B = 35 btu/lb
Heat content at point C = 104 btu/lb
Heat content at point E = 127 btu/lb
NRE = 104 btu/lb – 35 btu/lb = 69 btu/lb
HOC = 127 btu/lb – 104 btu/lb = 23 btu/lb
COP = 69 btu/lb ÷ 23 btu/lb = 3
Notice that the “3” has no units
ENERGY EFFICIENCY RATIO
(EER)
• A ratio of the amount of btus transferred to the
amount of power used
• In the units of btu/watt
• The conversion between btus and watts is
3.413
• One watt of power generates 3.413 btu
• For example, if a system required 50,000 btu of
heat, 14,650 watts of electric heat (14.65 kw)
can be used
ENERGY EFFICIENCY RATIO
(EER), Cont’d.
• The efficiency rating of an air conditioning
system is the COP
• For each btu/lb introduced to the system in the
suction line and the compressor, a number of
btus equal to the NRE are absorbed into the
system via the evaporator
• To convert the COP to energy usage, we
multiply the COP by 3.413
EER EXAMPLE
•
•
•
•
•
•
The NRE of a system is 70 btu/lb
The HOC of the same system is 20 btu/lb
The COP is 70 btu/lb ÷ 20 btu/lb = 3.5
The EER = COP x 3.413
EER = 3.5 x 3.413
EER = 11.95
SEASONAL EER (SEER)
• Takes the entire conditioning system into
account
• Varies depending on the geographic
location of the equipment
• Ranges from 10% t0 30% higher than EER
• So, if the EER is 10, the SEER will range
from 11 to 13
From the P-H Chart, We Can Find
•
•
•
•
•
•
•
Compression Ratio
NRE
HOC
HOW
THOR
COP
MFR/ton
•
•
•
•
•
•
•
THp/ton
MFR/system
Evaporator Capacity
Condenser Capacity
Compressor Capacity
EER of the System
SEER
Okay, Okay, Okay… How do I plot one of these things?
An R-22 A/C System…
•
•
•
•
•
•
Condenser saturation temperature 120°F
Condenser outlet temperature 100°F
Evaporator saturation temperature 40°F
Evaporator outlet temperature 50°F
Compressor inlet temperature 60°F
Compressor Horsepower: 4 hp
Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified)
Pressure
(psia)
180°F
160°F
140°F
352
0.7
120°F
275
100°F
211
80°F
159
60°F
117
40°F
84
20°F
58
0°F
39
-20°F
25
-40°F
3 4 4 5
2 0 6 3
Enthalpy in btu/lb (Heat Content)
1 1 1 1 1
1 1 1 2 2
0 2 7 1 5
Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified)
Pressure
(psia)
180°F
160°F
140°F
352
0.7
120°F
275
100°F
211
80°F
159
60°F
117
40°F
84
20°F
58
0°F
39
-20°F
25
-40°F
3 4 4 5
2 0 6 3
Enthalpy in btu/lb (Heat Content)
1 1 1 1 1
1 1 1 2 2
0 2 7 1 5
Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified)
Pressure
(psia)
180°F
160°F
352
275
140°F
A
100°F
211
80°F
159
60°F
117
40°F
84
58
0.7
120°F
B
20°F
C
0°F
39
-20°F
25
-40°F
3 4 4 5
2 0 6 3
Enthalpy in btu/lb (Heat Content)
1 1 1 1 1
1 1 1 2 2
0 2 7 1 5
Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified)
Pressure
(psia)
180°F
160°F
352
275
140°F
A
100°F
211
80°F
159
60°F
117
40°F
84
58
0.7
120°F
B
20°F
C
D
0°F
39
-20°F
25
-40°F
3 4 4 5
2 0 6 3
Enthalpy in btu/lb (Heat Content)
1 1 1 1 1
1 1 1 2 2
0 2 7 1 5
Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified)
Pressure
(psia)
180°F
160°F
352
275
140°F
A
100°F
211
80°F
159
60°F
117
40°F
84
58
0.7
120°F
B
20°F
C
D
0°F
39
-20°F
25
-40°F
3 4 4 5
2 0 6 3
Enthalpy in btu/lb (Heat Content)
1 1 1 1 1
1 1 1 2 2
0 2 7 1 5
Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified)
Pressure
(psia)
180°F
160°F
352
275
140°F
A
100°F
211
80°F
159
60°F
117
40°F
84
58
E
120°F
B
20°F
C
D
0°F
39
-20°F
25
-40°F
3 4 4 5
2 0 6 3
Enthalpy in btu/lb (Heat Content)
1 1 1 1 1
1 1 1 2 2
0 2 7 1 5
0.7
Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified)
Pressure
(psia)
180°F
160°F
352
275
140°F
A
0.7
100°F
211
80°F
159
60°F
117
40°F
84
58
E
120°F
B
20°F
C
D
0°F
39
High: 275 psia
-20°F
25
-40°F
Low: 84 psia
“A”: 40 btu/lb
“B”: 40 btu/lb
“C”: 110 btu/lb
“D”: 112 btu/lb
3 4 4 5
2 0 6 3
Enthalpy in btu/lb (Heat Content)
1 1 1 1 1
1 1 1 2 2
0 2 7 1 5
“E”: 125 btu/lb
High: 275 psia
COMPRESSION RATIO
Low: 84 psia
“A”: 40 btu/lb
HIGH SIDE PRESSURE (psia)
“B”: 40 btu/lb
LOW SIDE PRESSURE (psia)
“C”: 110 btu/lb
“D”: 112 btu/lb
“E”: 125 btu/lb
COMPRESSION RATIO = 275 psia ÷ 84 psia = 3.27:1
High: 275 psia
HEAT OF WORK
Low: 84 psia
“A”: 40 btu/lb
HEAT CONTENT AT “E” – HEAT CONTENT AT “D”
“B”: 40 btu/lb
“C”: 110 btu/lb
“D”: 112 btu/lb
“E”: 125 btu/lb
HEAT OF WORK = 125 btu/lb – 112 btu/lb = 13 btu/lb
High: 275 psia
HEAT OF COMPRESSION
Low: 84 psia
“A”: 40 btu/lb
HEAT CONTENT AT “E” – HEAT CONTENT AT “C”
“B”: 40 btu/lb
“C”: 110 btu/lb
“D”: 112 btu/lb
“E”: 125 btu/lb
HEAT OF COMPRESSION= 125 btu/lb – 110 btu/lb =
15 btu/lb
High: 275 psia
NET REFRIGERATION EFFECT
Low: 84 psia
“A”: 40 btu/lb
HEAT CONTENT AT “C” – HEAT CONTENT AT “B”
“B”: 40 btu/lb
“C”: 110 btu/lb
“D”: 112 btu/lb
“E”: 125 btu/lb
NRE = 110 btu/lb – 40 btu/lb = 70 btu/lb
High: 275 psia
MASS FLOW RATE PER TON
Low: 84 psia
“A”: 40 btu/lb
200 ÷ NRE
“B”: 40 btu/lb
“C”: 110 btu/lb
“D”: 112 btu/lb
“E”: 125 btu/lb
MFR/ton = 200 ÷ NRE =200 ÷ 70 btu/lb = 2.86 lb/min/ton
High: 275 psia
TOTAL HEAT OF REJECTION
Low: 84 psia
“A”: 40 btu/lb
HEAT CONTENT AT “E” – HEAT CONTENT AT “A”
“B”: 40 btu/lb
“C”: 110 btu/lb
“D”: 112 btu/lb
“E”: 125 btu/lb
THOR = 125 btu/lb – 40 btu/lb = 85 btu/lb
High: 275 psia
THEORETICAL HORSEPOWER PER TON
Low: 84 psia
“A”: 40 btu/lb
[MFR/ton x HOW] ÷ 42.42
“B”: 40 btu/lb
“C”: 110 btu/lb
“D”: 112 btu/lb
“E”: 125 btu/lb
THp/ton = 2.86 lb/min/ton x 13 btu/lb ÷ 42.42 = 0.88 Hp/ton
High: 275 psia
COEFFICIENT OF PERFORMANCE
Low: 84 psia
“A”: 40 btu/lb
NRE ÷ HOC
“B”: 40 btu/lb
“C”: 110 btu/lb
“D”: 112 btu/lb
“E”: 125 btu/lb
COP = 70 btu/lb ÷ 15 btu/lb = 4.67
High: 275 psia
MASS FLOW RATE OF THE SYSTEM
Low: 84 psia
“A”: 40 btu/lb
[42.42 x Compressor HP] ÷ HOW
“B”: 40 btu/lb
“C”: 110 btu/lb
“D”: 112 btu/lb
“E”: 125 btu/lb
MFR/system = [42.42 x 4] ÷ 13 btu/lb = 13.05 lb/min
High: 275 psia
CAPACITY OF THE EVAPORATOR
Low: 84 psia
“A”: 40 btu/lb
NRE x MFR/system x 60
“B”: 40 btu/lb
“C”: 110 btu/lb
“D”: 112 btu/lb
“E”: 125 btu/lb
CAP/evap = 70 btu/lb x 13.05 x 60 = 54,810 btu/hour
CAP/evap = 54,810 btu/hour ÷ 12,000 btu/hour/ton = 4.57 tons
High: 275 psia
CAPACITY OF THE CONDENSER
Low: 84 psia
“A”: 40 btu/lb
THOR x MFR/system x 60
“B”: 40 btu/lb
“C”: 110 btu/lb
“D”: 112 btu/lb
“E”: 125 btu/lb
CAP/cond = 85 btu/lb x 13.05 x 60 = 66,555 btu/hour
CAP/cond = 66,555 btu/hour ÷ 12,000 btu/hour/ton = 5.55 tons
High: 275 psia
CAPACITY OF THE COMPRESSOR
Low: 84 psia
MFR/system x Specific Volume
“A”: 40 btu/lb
“B”: 40 btu/lb
“C”: 110 btu/lb
“D”: 112 btu/lb
“E”: 125 btu/lb
CAP/comp = 13.05 x 0.7 = 9.13 ft3/min
High: 275 psia
ENERGY EFFICIENCY RATIO
Low: 84 psia
“A”: 40 btu/lb
COP x 3.413
“B”: 40 btu/lb
“C”: 110 btu/lb
“D”: 112 btu/lb
“E”: 125 btu/lb
EER = 4.67 x 3.413 = 15.94
SEER (low end) = 1.1 x EER = 1.1 x 15.94 = 17.5
SEER (high end) = 1.3 x EER = 1.3 x 15.94 = 20.7
275 psia
84 psia
61 psia
40
110 112
100 111
125
Let’s See What Happened…
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CR = 3.27
HOW = 13
HOC = 15
NRE = 70
MFR/ton = 2.86 lb/min
THp/ton = 0.88
COP = 4.67
MFR/system = 13.05
CAP/evap = 66,555 btu
EER = 15.9
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CR = 4.5
HOW = 14
HOC = 25
NRE = 60
MFR/ton = 3.33 lb/min
THp/ton = 1.1
COP = 2.4
MFR/system = 12.12
CAP/evap = 43,632 btu
EER = 8.19
Properly Operating System
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Heat Content “A” = 40 btu/lb
Heat Content “B” = 40 btu/lb
Heat Content “C” = 109 btu/lb
Heat Content “D” = 111 btu/lb
Heat Content “E” = 125 btu/lb
High side pressure = 267 psig
High side pressure = 282 psia
Low side pressure = 70 psig
Low side pressure = 85 psia
Compressor Hp = 2.5 Hp
Specific Volume = 0.7
A/B
C D
E
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NRE = 69 btu/lb
HOW = 14 btu/lb
HOC = 16 btu/lb
THOR = 85 btu/lb
Comp. Ratio = 3.32
MFR/ton = 2.9 lb/min/ton
THp/ton = 0.96 Hp/ton
COP = 4.3
MFR/system = 7.58 lb/min
CAP/evap = 31,381 btuh
CAP/cond = 38,658 btuh
CAP/comp = 5.3 ft3/min
EER = 14.68
SEER = 16.15 – 19.1
Clogged Cap Tube System
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Heat Content “A” = 39 btu/lb
Heat Content “B” = 39 btu/lb
Heat Content “C” = 112 btu/lb
Heat Content “D” = 118 btu/lb
Heat Content “E” = 134 btu/lb
High side pressure = 226 psig
High side pressure = 241 psia
Low side pressure = 59 psig
Low side pressure = 74 psia
Compressor Hp = 2.5 Hp
Specific Volume = 0.9
A/B
C D
E
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NRE = 73 btu/lb
HOW = 16 btu/lb
HOC = 22 btu/lb
THOR = 95 btu/lb
Comp. Ratio = 3.26
MFR/ton = 2.74 lb/min/ton
THp/ton = 1.03 Hp/ton
COP = 3.3
MFR/system = 6.63 lb/min
CAP/evap = 29,039 btuh
CAP/cond = 37,791 btuh
CAP/comp = 5.97 ft3/min
EER = 11.26
SEER = 12.39 – 14.64
System Okay
System Clogged
Increase/Decrease
NRE
69
73
Increase
HOW
14
16
Increase
HOC
16
22
Increase
THOR
85
95
Increase
Comp. Ratio
3.32
3.26
Decrease
MFR/ton
2.9
2.74
Decrease
THp/ton
0.96
1.03
Increase
COP
4.3
3.3
Decrease
MFR/system
7.58
6.63
Decrease
CAP/evap
31,381 (2.62)
29,039 (2.42)
Decrease
CAP/cond
38,658 (3.22)
37,791 (3.15)
Decrease
CAP/comp
5.3
5.97
Increase
14.68
11.26
Decrease
16.15 – 19.1
12.39 – 14.64
Decrease
EER
SEER
Contact Information...
Eugene Silberstein
Suffolk County Community College
1001 Crooked Hill Road
Brentwood, NY 11717
(631) 851-6897
E-mail: silbere@sunysuffolk.edu