Thomas J Kelly Sr. Engineering Instructor Carrier Corporation August 20, 2003 1
SESSION OBJECTIVES At the conclusion of this session you should be able to: 1. Describe the basics principles of refrigeration systems operation 2. Understand 10 common refrigeration terms 3. Develop a PH diagram to use as a system analysis tool 4. Use a PH diagram to describe basic system operation in high temperature,medium temperature, low temperature and multi-stage refrigeration systems 5. Identify and place common system elements and components in the refrigeration system and understand their function in system operation 6. Understand basic system layouts associated with commercial store refrigeration 2
COMFORT VS. PROCESS The mechanical refrigeration process is used for two major types of market Comfort Cools and dehumidifies people Process Controls temperature and humidity for things The basic process is the same 3
THE REFRIGERATION MARKET CHAIN Food products depend on refrigeration for processing, storage and delivery - At the point of harvest - Warehousing - Delivery to the market - Market display and sale - Consumer storage 4
REFRIGERATION TERMS PH diagram Superheat Enthalpy Refrigeration Effect Flash Gas What is he talking about? Sub-cooling Vapor Quality High Side / Low Side Latent Heat Sensible Heat Saturated Suction Throttling Range Heat of Compression Expansion Device Heat of Rejection Refrigeration Effect 5
BASIC SYSTEM COMPONENTS Every system has 4 basic components Evaporator Absorbs the heat from the air or load Cold Mixture Air out: 59.7F DB / 57.3F WB 47 F 78 PSI EVAPORATOR Air in: 80F DB / 67F WB Cold Vapor 59 F 78 PSI 6
BASIC SYSTEM COMPONENTS Every system has 4 basic components Evaporator Hot Vapor 220 F 175PSI Compressor Raises the pressure from the evaporator pressure to the condensing temperature Air out: 59.7F DB / 57.3F WB 47 F 78 PSI EVAPORATOR COMPRESSOR Air in: 80F DB / 67F WB Cold Vapor 59 F 78 PSI 7
BASIC SYSTEM COMPONENTS Every system has 4 basic components Evaporator 110 F 175PSI CONDENSER Air out: 95F DB Hot Vapor 220 F 175PSI Compressor Hot Liquid Air in: 95F DB Condenser COMPRESSOR Air out: 59.7F DB / 57.3F WB Rejects the heat from the load and system losses 47 F 78 PSI EVAPORATOR Air in: 80F DB / 67F WB 59 F 78 PSI 8
BASIC SYSTEM COMPONENTS Every system has 4 basic components Evaporator 110 F 175PSI CONDENSER Hot Liquid Air out: 95F DB 220 F 175PSI Compressor METERING DEVICE Air in: 95F DB Condenser Metering device Regulates the flow and decreases the pressure from condensing pressure to evaporator pressure Cold Mixture Air out: 59.7F DB / 57.3F WB 47 F 78 PSI EVAPORATOR COMPRESSOR Air in: 80F DB / 67F WB 59 F 78 PSI 9
BASIC SYSTEM COMPONENTS High Side High Side CONDENSER Compressor discharge to Metering device METERING DEVICE Low Side COMPRESSOR Metering device to Compressor suction EVAPORATOR Low Side 10
4 LAW OF SYSTEM OPERATION 1. Heat only moves from higher temperature to a lower temperature NO FLOW 70º 70º 70º FLOW 32º 212º FLOW 70º 11
4 LAW OF SYSTEM OPERATION 1. Heat only moves from higher temperature to a lower temperature 2. Energy required to change of states of matter is large Sensible Heat 71 º F 70 º F 1 BTU / LB 12
4 LAW OF SYSTEM OPERATION 1. Heat only moves from higher temperature to a lower temperature 2. Energy required to change of states of matter is large Latent Heat SATURATED VAPOR 212ºF 212 º F 970 BTU / LB 13
4 LAW OF SYSTEM OPERATION 1. Heat only moves from higher temperature to a lower temperature 2. Energy required to change of states of matter is large 3. The temperature and energy required to change state are a function of pressure 190º F 9 PSIA 5 PSI 230º F 14
4 LAW OF SYSTEM OPERATION 1. Heat only moves from higher temperature to a lower temperature 2. Energy required to change of states of matter is large 3. The temperature and energy required to change state are a function of pressure 4. Fluid flow only occurs if a pressure difference exists 5 PSI 0 PSI 15
TEMPERATURE ENTHALPY PLOT R 718 ( Water) as an example TEMPERATURE ºF 256 212 32 Enthalpy is the total heat content Enthalpy = Sensible + Latent 0 Enthalpy(Btu/lb) 16
TEMPERATURE ENTHALPY PLOT R 718 ( Water) as an example 1 pound at standard barometric pressure TEMPERATURE ºF 212 32 0 ICE 16 Latent heat of Fusion 144 Btu/lb 160 LIQUID Sub-cooled Solid Enthalpy(Btu/lb) 17
TEMPERATURE ENTHALPY PLOT R 718 ( Water) as an example 1 pound at standard barometric pressure 256 Superheated Vapor VAPOR TEMPERATURE ºF 212 32 0 Sub-cooled Liquid ICE 16 160 LIQUID Enthalpy(Btu/lb) Latent heat of Vaporization Condensation 1 Btu/lb 970 Btu/lb 0.45 Btu/lb 340 1310 1320 18
TEMPERATURE ENTHALPY PLOT R 718 ( Water) as an example 1 pound at standard barometric pressure 256 Superheated Vapor VAPOR TEMPERATURE ºF 212 32 0 Sub-cooled Liquid ICE 16 160 LIQUID 100% Saturated Liquid 1 Btu/lb 970 Btu/lb 0.45 Btu/lb Enthalpy(Btu/lb) 100% Saturated Liquid 340 1310 1320 19
P H DIAGRAM Plots enthalpy vs. pressure P10 P9 Critical Point P8 PRESSURE PSIA P7 P6 P5 P4 P3 P2 Saturated Liquid Saturated Vapor P1 Enthalpy(Btu/lb) 20
P H DIAGRAM Take note the lines become closer at higher pressure less latent capacity P10 P9 Critical Point 422 PRESSURE PSIA P7 P6 P5 P4 14.7 775 Btu/lb P2 P1 Saturated Liquid 970 Btu/lb Saturated Vapor Enthalpy(Btu/lb) 21
P H DIAGRAM Vapor Quality is percentage of the mixture P10 P9 P8 Sub-cooled Liquid Critical Point PRESSURE PSIA P7 P6 P5 P4 P3 20 40 60 80 Superheated Vapor P2 P1 Vapor Quality Enthalpy(Btu/lb) 22
P H DIAGRAM Refrigerant Blends P10 P9 P8 Sub-cooled Liquid Critical Point PRESSURE PSIA P7 P6 P5 P4 P3 Bubble Point Blends Dew Point Superheated Vapor P2 P1 Vapor Quality Enthalpy(Btu/lb) 23
P H DIAGRAM Temperature Lines P10 PRESSURE PSIA 422 14.7 212 ºF 450 ºF TEMPERATURE P1 Enthalpy(Btu/lb) 24
P H DIAGRAM Entropy Lines PRESSURE PSIA P10 422 14.7 ENTROPY 451 Btu/ºR 450 Btu/ºR P1 Enthalpy(Btu/lb) 25
P H DIAGRAM Specific Volume Lines P10 PRESSURE PSIA 422 14.7 SPECIFIC VOLUME 1.1 ft 3 /lb 26.8 ft 3 /lb P1 Enthalpy(Btu/lb) 26
P H DIAGRAM Time to test your skill SATURATED LIQUID SATURATED VAPOR SUBCOOLED LIQUID SATURATED MIXTURE SUPERHEATED VAPOR 27
PH DIAGRAM FOR R-22 TEMPERATURE ENTROPY 300 225 147 125 105 70 PRESSURE PSIA 91 57 38 20-30 20 0 45 SPECIFIC VOLUME R-22-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 28
BASIC SYSTEM ON THE PH DIAGRAM PRESSURE PSIA 300 225 147 91 57 38 20 EXPANSION DEVICE 45 20 0-30 125 105 70 CONDENSER EVAPORATOR COMPRESSOR R-22-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 29
EVAPORATOR TYPES Air cooled Water cooled (cooler) 30
EVAPORATOR PROCESS Two processes 1. Evaporation change the mixture of gas and liquid refrigerant to all vapor 2. Superheating Increase temperature above saturated suction Superheat is required to assure vapor at the compressor But has negative impact on total system efficiency Cold Mixed Phase Saturated Vapor Cold Superheated Vapor Evaporation Superheat 31
EVAPORATOR OPERATION Flash Gas - Vapor quality entering evaporator Refrigeration Effect Total heat absorbed by evaporator 47 F 78 PSI EVAPORATOR Air out: 59.7F DB / 57.3F WB Air in: 80F DB / 67F WB 59 F 78 PSI Cold Mixed Phase 47F - 78PSI Flash Gas Refrigeration Effect Cold Superheated Vapor 59F 78PSI 32
COMPRESSOR TYPES Reciprocating Scroll Screw Rotary Centrifugal 33
COMPRESSOR PROCESS One process 1. Raise the pressure of the superheated gas from saturated suction temperature to a pressure which corresponds to saturated condensing - Decreases the volume Increases the pressure Increases the temperature - The compression process adds considerably more superheat Hot Superheated Vapor Saturated Vapor Compression Cold Superheated Vapor 34
COMPRESSSOR OPERATION Heat of Compression Heat added from the compression process Compression Ratio Discharge pressure / suction pressure EVAPORATOR COMPRESSOR 50 F 55PSI 220 F 175PSI Hot Superheated Vapor 220F 175PSI Compression Ratio Compression Heat of Compression Cold Superheated Vapor 59F 78PSI 35
ROTARY COMPRESSORS Used in : Small AC units Appliances Uses rotating piston and a sliding vane 36
RECIPROCATING COMPRESSORS Used in : AC, Refrigeration & Appliances Uses reciprocating piston and reed valves 37
SCROLL COMPRESSOR Used in : AC, Refrigeration & Appliances Uses a stationary scroll and a rotating scroll and has no valves 38
SCREW COMPRESSOR Used in : AC & Refrigeration Uses a stationary screw and a rotating screw and a slide valve 39
CONDENSER TYPES Air cooled Water cooled 40
CONDENSER PROCESS Three processes 1. De-Superheating Lower temperature to saturated condensing temp. 2. Condensing Condense vapor to liquid 3. Sub-cool the liquid below saturated condensing temperature, sub-cooling: - Is required to assure liquid at the expansion device - Has positive impact on total system efficiency Sub-cooling Condensing Hot Superheated Vapor 220F 175PSI Hot Sub-cooled Liquid 110F 175PSI Saturated Vapor De-superheating 41
CONDENSER OPERATION Heat of Rejection Refrigerant effect plus heat of compression 110 F 175PSI CONDENSER Air out: 95F DB 220 F 175PSI EVAPORATOR Air in: 95F DB COMPRESSOR Heat of Rejection Hot Superheated Vapor Hot Sub-cooled Liquid 42
EXPANSION DEVICES TYPES Fixed Metering TXV Floats 43
EXPANSION DEVICE PROCESS Two processes 1. Create a pressure drop Decreasing the temperature below saturated suction, Flashing part of the liquid into vapor to cool the mixture of vapor and liquid to saturated suction temperature 2. Meter the flow of refrigerant Hot Sub-cooled Liquid 110F 175PSI Expansion Device Cold Mixed Phase 47F 70PSI 44
EXPANSION DEVICE OPERATION Throttling Range Pressure drop available across the metering device METERING DEVICE CONDENSER 110 F 175PSI 47 F 78 PSI EVAPORATOR COMPRESSOR Hot Hot Sub-cooled Sub-cooled Liquid Liquid 110F 175PSI Expansion Device Throttling Range Cold Mixed Phase 47F 70PSI 45
PH DIAGRAM - SYSTEM INEFFICIENCIES Liquid Line P Condenser Coil P Discharge Line P Evaporator Coil P Suction Line P 46
P H DIAGRAM FOR R-134A REFRIGERANT PRESSURE PSIA 300 225 147 91 57 38 20-30 0 20-30 45 0 70 20 125 105 45 R-22 105 70 R-134 125-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 47
R-22 VS. R-134A REFRIGERANT CYCLE 300 225 147 70 125 125 PRESSURE PSIA 91 57 38 20 45 45 R-22 R-134-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 48
P H DIAGRAM FOR R-404 REFRIGERANT PRESSURE PSIA 300 225 147 91 57 38 20 20 0-30 0-30 125 125 105 105 70 70 45 45 20 R-22 R-404-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 49
R-22 VS. R-404 REFRIGERANT CYCLE PRESSURE PSIA 300 225 147 91 57 38 20 125 125 70 45 R-22 R-404-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 50
THE BASIC REFRIGERATION SYSTEM Basic System LIQUID LINE DRIER MOISTURE LIQUID INDICATOR EXPANSION VALVE CONDENSER RECIEVER EVAPORATOR COMPRESSOR SUCTION ACCUMULATOR Basic Refrigeration System Same system with a few special features 51
PH DIAGRAM - HIGH TEMPERATURE CONDENSER PRESSURE PSIA 400 293 200 140 100 91 60 40 20 10 TXV TR=202 PSI 45 125 THR = 81 BTU/# EVAPORATOR RE = 67 BTU/# COMPRESSOR CR=3.2 R-22-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 52
REFRIGERATION SYSTEM TYPES Self Contained Condensing units Rack systems 53
TYPICAL LARGER MARKET LAYOUT MEAT-DELI AIR COOLED CONDENSER WALK-IN COOLER MEDIUM TEMP RACK LOW TEMP RACK MULTI DECK DELI/DAIRY SINGLE DECK MEAT DISPLAY WALK-IN FREEZER REACH IN FROZEN FOOD FROZEN FOOD 54
TYPICAL SMALLER MARKET LAYOUT AIR COOLED CONDENSER WALK-IN COOLER MEDIUM/LOW TEMP RACK MEAT/DELI MULTI DECK DELI/DAIRY FROZEN FOODS 55
CONVENIENCE STORE LAYOUT LOW MED MED TEMP COND UNIT MULTI DECK DELI/DAIRY MEAT/DELI FROZEN FOODS 56
MEDIUM TEMPERATURE REFRIGERATION Typical Cases 15F to 35F PRODUCE AND DELI LIQUID LINE DRIER MOISTURE LIQUID INDICATOR EXPANSION VALVE CONDENSER RECIEVER EVAPORATOR COMPRESSOR SUCTION ACCUMULATOR 57
PH DIAGRAM - MEDIUM TEMPERATURE CONDENSER 400 293 125 THR = 94 BTU/# PRESSURE PSIA 200 140 100 60 57 40 20 10 TXV TR=236 PSI 20 EVAPORATOR RE = 70 BTU/# COMPRESSOR CR=5.1 R-22-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 58
LOW TEMPERATURE REFRIGERATION Typical Cases -15F to -30F FROZEN FOOD AND ICE CREAM LIQUID LINE DRIER MOISTURE LIQUID INDICATOR EXPANSION VALVE CONDENSER RECIEVER EVAPORATOR COMPRESSOR SUCTION ACCUMULATOR 59
PH DIAGRAM - LOW TEMPERATURE CONDENSER 400 293 125 THR = 96 BTU/# 200 140 100 TXV TR=276 PSI PRESSURE PSIA 60 40 20 17 10-30 EVAPORATOR COMPRESSOR CR=17.2 RE = 63 BTU/# R-22-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 60
REFRIGERATION EVAPORATORS Cases Ice Cream Air SST -25F -35F Produce Air SST +33F 20F Meat Air SST 27F 15F Frozen Food Air SST -15F -25F Dairy Air SST 25F 15F 61
REFRIGERATION EVAPORATORS Unit Coolers Reach in Walk In Blast freezers 62
EVAPORATOR DEFROST Air Defrost Electric Defrost Hot Gas Reverse Cycle Three pipe Drain pan heaters 63
DEFROST DIFFERENTIAL VALVES Defrost with Differential Regulating Valve Liquid line Discharge Line 64
DEFROST DIFFERENTIAL VALVES Defrost with Differential Regulating Valve CONDENSER LIQUID LINE DRIER MOISTURE LIQUID INDICATOR LIQUID DIFFERENTIAL VALVE SOLENOID VALVE SOLENOID VALVE CHECK VALVE EVAPORATOR EXPANSION VALVE RECIEVER DISCHARGE DIFFERENTIAL VALVE EVAPORATOR SOLENOID VALVE COMPRESSOR SUCTION ACCUMULATOR EVAPORATOR PRESSURE REGULATOR 65
Evaporator Pressure Regulators Maintains constant pressure in the evaporator 66
Evaporator Pressure Regulators LIQUID LINE DRIER MOISTURE LIQUID INDICATOR EXPANSION VALVE CONDENSER RECIEVER EVAPORATOR COMPRESSOR EVAPORATOR PRESSURE SUCTION REGULATOR ACCUMULATOR 67
Evaporator Pressure Regulator Multiple Evaporator systems with common suction Maintains stable evaporator pressure to control temperature Common Suction Header 10 F 44 psig Receiver 15 F 20 F 68
PH DIAGRAM MULTIPLE EVAPORATORS 400 293 125 CONDENSER 200 140 100 TXV PRESSURE PSIA 60 57 40 20 17 10 20-30 MEDIUM STAGE LOW STAGE EVAPORATOR COMPRESSOR R-22-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 69
SUCTION ACCUMULATOR Protects the compressor from liquid Separates vapor from liquid Provides for oil return Oil Return Orifice IN Fusible Plug 70
RECIEVERS Provide storage volume for excess refrigerant Pump down storage 71
REFRIGERATION COMPRESSORS Self Contained Condensing Units Rack Systems 72
REFRIGERATION COMPRESSORS Scroll 1 to 15 HP Refrigeration duty differences Vapor Injection Liquid Injection Applications Self contained Condensing units Rack systems 73
REFRIGERATION COMPRESSORS 400 293 125 CONDENSER 200 140 100 TXV PRESSURE PSIA 60 57 40 20 17 10 20-30 GAIN INJECTION LOW STAGE EVAPORATOR COMPRESSOR R-22-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 74
REFRIGERATION COMPRESSORS Reciprocating Hermetic 1 to 5 HP Refrigeration duty differences Applications Self contained Condensing units Rack systems 75
REFRIGERATION COMPRESSORS Reciprocating Semi-Hermetic 3 to 60 HP Refrigeration duty differences Cooling fans Compound cooling Applications Stand alone Condensing units Rack systems 76
REFRIGERATION COMPRESSORS Reciprocating Semi-Hermetic Typical low temperature De-superheating valve 77
COMPOUND COMPRESSORS Single compressor Multiple compressor 78
COMPOUND COOLING 400 293 125 CONDENSER 200 140 100 TXV PRESSURE PSIA 60 57 40 20 17 10 20-30 MEDIUM STAGE LOW STAGE EVAPORATOR COMPRESSOR R-22-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 79
REFRIGERATION COMPRESSORS Screw Compressor 20 to 140 HP Refrigeration duty differences Oil control system Liquid injection Applications Condensing units Rack systems Built up system 80
Crankcase Pressure Regulator Prevents over-pressurization of Two-Stage Compressor crankcase. 400 293 125 CONDENSER 200 140 100 TXV PRESSURE PSIA 60 57 40 20 17 10 20-30 MEDIUM STAGE LOW STAGE EVAPORATOR COMPRESSOR R-22-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 81
Crankcase Pressure Regulator On two-stage compressors systems and Low Temperature - - Compression Ratio > 10:1 Discharge of One Cylinder is De- Superheated and Used as Suction for Another Cylinder to Limit the Heat of Compression. Results: Excessively High Suction Pressures after -Pull-Down or Defrost Cycles, can Cause Motor Overload. 82
CAPACITY CONTROL Why? Prevent the Compressor from Short Cycling Prevent Compressor from Operating with Too Low Suction Pressures Prevent Evaporating Coil Icing OPTIONS: 1. Multiple Units 2. Single Units with Multiple Compressors. 3. Variable Speed Compressors 4. Compressor Cylinder Unloading 5. Hot Gas Bypass 83
CAPACITY CONTROL 1. Multiple Units 2. Single Units with Multiple Compressors. 3. Variable Speed Compressors 84
CAPACITY CONTROL 4. Compressor Cylinder Unloading 85
HOT GAS BYPASS CONTROL LIQUID LINE DRIER MOISTURE LIQUID INDICATOR EXPANSION VALVE CONDENSER RECIEVER EVAPORATOR COMPRESSOR EVAPORATOR PRESSURE SUCTION REGULATOR ACCUMULATOR 86
Hot Gas Bypass Regulators 87
Hot Gas Bypass Bypasses High Pressure Refrigerant to the System s Low Pressure Side. Regulates to Maintain a Set Minimum Suction Pressure. De-Superheating TXV Bypass to Suction Bypass to Evaporator Inlet 88
BYPASS TO SUCTION WITH SUCTION ACCUMULATOR BYPASS SOLENOID BYPASS REGULATOR LIQUID INJECTION THERMO VALVE LIQUID INJECTION SOLENOID VALVE SUCTION ACCUMULATOR SUCTION UPSTREAM OF ACCUMULATOR 89
BYPASS TO SUCTION WITH SUCTION ACCUMULATOR BYPASS SOLENOID BYPASS REGULATOR LIQUID INJECTION THERMO VALVE LIQUID INJECTION SOLENOID VALVE OUTLET OF ACCUMULATOR UPSTREAM OF ACCUMULATOR SUCTION * IF A BOILOUT ACCUMULATOR IS USED, LOCATE LCL BULB UPSTREAM 90
BYPASS TO SUCTION WITH SUCTION ACCUMULATOR BYPASS SOLENOID BYPASS REGULATOR LIQUID INJECTION THERMO VALVE Constant head pressure is required during periods of bypass. LIQUID INJECTION SOLENOID VALVE SUCTION SUCTION ACCUMULATOR 91
BYPASS TO EVAPORATOR INLET BYPASS TO EVAPORATOR INLET BYPASS SOLENOID DIRECT ACTING BYPASS REGULATOR ADVANTAGES: Provides a False Load Defrost the Coil, A/C Evaporator serves as mixing chamber Minimizes components Excellent Oil Return THERMO VALVE LIQUID LINE SOLENOID VALVE EVAPORATOR COMPRESSOR 92
BYPASS TO EVAPORATOR INLET BYPASS TO EVAPORATOR INLET BYPASS SOLENOID DIRECT ACTING BYPASS REGULATOR With the evaporator BELOW the compressor, bypass to evaporator inlet assures proper oil return at low loads. COMPRESSOR THERMO VALVE LIQUID LINE SOLENOID VALVE EVAPORATOR 93
REFRIGERATION CONDENSERS Air Cooled Water Cooled 94
Head Pressure Control Why? Maintain Liquid Sub-Cooling and Prevent liquid line flash gas. Provide sufficient pressure drop across TXV. Properly operate systems with hot gas defrost, hot gas bypass or heat reclaim systems. How? hvariable Condenser Fan Speed Control hwater regulating valve hcondenser Fan Cycling hvane / Damper Control System hsplit Condenser System h Flooded Head Pressure Control 95
Head Pressure Control Air Cooled Units Fan Cycling HEAD PRESSURE 200 150 Fan on Fan off TIME 96
Head Pressure Control Air Cooled Units Variable Speed Fan Water Cooled Units Water regulating Valve 97
HEAD PRESSURE CONTROL CONSTANT LOAD AT REDUCED CONDENSING TEMPERATURE 400 293 125 CONDENSER 200 140 100 TXV PRESSURE PSIA 60 57 40 20 17 10 20-30 MEDIUM STAGE LOW STAGE EVAPORATOR COMPRESSOR R-22-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 98
CONDENSER HEAD PRESSURE CONTROL CONDENSER TEMPERATURE CONTROL HEAD PRESSURE CONTROL VALVE LIQUID LINE DRIER MOISTURE LIQUID INDICATOR FAN CYCLING CONTROL SOLENOID VALVE EXPANSION VALVE OIL SEPERATOR OIL FILTER CONDENSER COMPRESSOR OIL LEVEL CONTROL OIL PRESSURE SAFETY CONTROL RECIEVER BALL VALVE SUCTION FILTER -DRIER LOW PRESSURE CONTROL SOLENOID VALVE HOT GAS BYPASS REGULATOR HIGH -LOW PRESSURE CONTROL SUCTION ACCUMULATOR EVAPORATOR PRESSURE REGULATOR EVAPORATOR EVAPORATOR TEMPERATURE CONTROL 99
Flooded Condenser Condenser Bypass Receiver Condenser Outlet 100
FLOODED CONDENSER CONTROL 101
METERING DEVICES IN REFRIGERATION Expansion Valves - -Equalizer - Constant pressure valves Hand Valves 102
OPR Manual Adjustment Outlet Pressure regulators Inlet Pressure Regulated Outlet Pressure 103
IPR Manual Adjustment Inlet Pressure Regulators Outlet Pressure Regulated Inlet Pressure 104
DESUPERHEATERS Reduce compressor superheat 400 293 125 CONDENSER 200 140 100 TXV PRESSURE PSIA 60 57 40 20 17 10 20-30 DE-SUPERHEATER LOW STAGE EVAPORATOR COMPRESSOR R-22-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 105
REFRIGERATION SYSTEM VALVES Control Isolation CONDENSER TEMPERATURE CONTROL LIQUID LINE DRIER MOISTURE LIQUID INDICATOR FAN CYCLING CONTROL SOLENOID VALVE EXPANSION VALVE OIL SEPERATOR OIL FILTER CONDENSER COMPRESSOR OIL LEVEL CONTROL OIL PRESSURE SAFETY CONTROL RECIEVER BALL VALVE SUCTION FILTER -DRIER LOW PRESSURE CONTROL SOLENOID VALVE HOT GAS BYPASS REGULATOR HIGH -LOW PRESSURE CONTROL SUCTION ACCUMULATOR EVAPORATOR PRESSURE REGULATOR EVAPORATOR EVAPORATOR TEMPERATURE CONTROL 106
SOLENOIDS VALVES Provide Control Function - On / Off Control - Normally Open / Normally closed Used -Pump down - Circuit isolation -Hot Gas isolation - Defrost Isolation 107
REFRIGERATION VALVES Ball Valves Diaphragm Valves Packed Angle Valves Globe Valves Pressure Relief Valves - Condensers - Pressure Vessels Check Valves 108
REFRIGERATION SYSTEM PROTECTORS Moisture Liquid Indicators Filter Driers CONDENSER TEMPERATURE CONTROL LIQUID LINE DRIER MOISTURE LIQUID INDICATOR FAN CYCLING CONTROL SOLENOID VALVE EXPANSION VALVE OIL SEPERATOR OIL FILTER CONDENSER COMPRESSOR OIL LEVEL CONTROL OIL PRESSURE SAFETY CONTROL RECIEVER SOLENOID VALVE BALL VALVE SUCTION FILTER -DRIER LOW PRESSURE CONTROL SUCTION ACCUMULATOR HOT GAS BYPASS REGULATOR HIGH -LOW PRESSURE CONTROL EVAPORATOR PRESSURE REGULATOR EVAPORATOR EVAPORATOR TEMPERATURE CONTROL 109
SIGHT GLASSES MOISTURE INDICATORS Provide an indication of refrigerant flow & moisture content Provide an indication of system charge Locations : Liquid line - Between liquid line filterdrier outlet & TXV inlet Oil Line - On oil separator or reservoir outlet 110
LIQUID LINE FILTER - DRIER Removes contaminants and chemical reaction products Filter-Driers remove Particles Water Acids Removes Solid and Sludge 111
SUCTION LINE FILTER - DRIER Suction line filter - Driers 112
OIL CONTROL SYSTEMS Oil system controls CONDENSER TEMPERATURE CONTROL LIQUID LINE DRIER MOISTURE LIQUID INDICATOR FAN CYCLING CONTROL SOLENOID VALVE EXPANSION VALVE OIL SEPERATOR OIL FILTER CONDENSER COMPRESSOR OIL LEVEL CONTROL OIL PRESSURE SAFETY CONTROL RECIEVER SOLENOID VALVE BALL VALVE SUCTION FILTER -DRIER LOW PRESSURE CONTROL SUCTION ACCUMULATOR HOT GAS BYPASS REGULATOR HIGH -LOW PRESSURE CONTROL EVAPORATOR PRESSURE REGULATOR EVAPORATOR EVAPORATOR TEMPERATURE CONTROL 113
OIL CONTROL SYSTEMS PROTECTS THE COMPRESSORS TO CONTROL PROPER OIL LEVEL SYSTEM -Oil level control -Oil separator -Oil sight glass -Oil line filter -Oil reservoir -Check valve TO CONDENSER OIL LINE FILTER CHECK VALVE OIL RESERVOIR DISCHARGE HEADER SUCTION HEADER OIL SEPARATOR OIL LEVEL CONTROL 114
OIL CONTROL SYSTEMS Low Pressure Oil Management System High Pressure Oil Management System SYSTEM -Oil level control -Oil separator -Oil sight glass -Oil line filter -Oil reservoir -Check valve TO CONDENSER OIL LINE FILTER OIL SEPARATOR TO CONDENSER CHECK VALVE OIL RESERVOIR DISCHARGE HEADER OIL LEVEL CONTROL OIL LINE FILTER DISCHARGE HEADER SUCTION HEADER SUCTION HEADER OIL SEPARATOR RESERVOIR OIL LEVEL CONTROL 115
TEMPERATURE & PRESSURE CONTROLS Temperature Controls Pressure Controls CONDENSER TEMPERATURE CONTROL LIQUID LINE DRIER MOISTURE LIQUID INDICATOR FAN CYCLING CONTROL SOLENOID VALVE EXPANSION VALVE OIL SEPERATOR OIL FILTER CONDENSER COMPRESSOR OIL LEVEL CONTROL OIL PRESSURE SAFETY CONTROL RECIEVER SOLENOID VALVE BALL VALVE SUCTION FILTER -DRIER LOW PRESSURE CONTROL SUCTION ACCUMULATOR HOT GAS BYPASS REGULATOR HIGH -LOW PRESSURE CONTROL EVAPORATOR PRESSURE REGULATOR EVAPORATOR EVAPORATOR TEMPERATURE CONTROL 116
TEMPERATURE CONTROL APPLICATIONS Evaporator temperature sensing Discharge air temperature sensing Product temperature sensing Return air temperature sensing Evaporator coil freeze protection Defrost termination 117
PRESSURE CONTROL APPLICATIONS Low Pressure Controls - Temperature control - Pump down control - High Temperature alarm - Defrost termination - Low pressure limit / alarm - Capacity control High Pressure Controls - High pressure cut-out - High pressure alarm - Condenser head pressure control Oil Pressure Controls - Oil pressure safety 118
ECONOMIZER CYCLE Improving Stage efficiency 400 293 125 CONDENSER 200 140 100 TXV PRESSURE PSIA 60 57 40 20 17 10 20-30 ECONOMIZER LOW STAGE EVAPORATOR COMPRESSOR R-22-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 119
HEAT RECLAIM SYSTEMS Recovery of Condenser heat for space heating HEAT RECLAIM COIL LIQUID LINE DRIER MOISTURE LIQUID INDICATOR LIQUID DIFFERENTIAL VALVE SOLENOID VALVE CONDENSER SOLENOID VALVE CHECK VALVE EVAPORATOR EXPANSION VALVE HEAT RECLAIM VALVE DISCHARGE DIFFERENTIAL VALVE COMPRESSOR RECIEVER SUCTION ACCUMULATOR EVAPORATOR EVAPORATOR PRESSURE REGULATOR SOLENOID VALVE 120
SYSTEM TYPES Direct Refrigerant runs directly to cases Indirect Secondary cooling circuit is used 121
Practice Example PH chart example, Let s look at a refrigeration example and plot a low temperature system 122
SUMMARY The P H Diagram is good tool to use to understand system operation and performance PRESSURE PSIA It can be used for -Design -Understanding new system concepts -Troubleshooting A knowledge of basic refrigeration system principles helps in the evaluation of refrigeration systems R-22-20 0 20 40 60 80 90 100 110 120 130 140 150 Enthalpy(Btu/lb) 123
Thank you Questions? 124