2013 Rocky Mountain ASHRAE Technical Conference

Energy Use in Systems

PRESENTED BY:

Scott Martin, PE, LEED AP BD+C Objectives

• Understand mechanical refrigeration terms

• Describe how heat is transferred and what methods are primarily used in the refrigeration cycle

• Describe the 4 principles of the refrigeration process

• Explain the function of the 4 system components

• Explain properties

Section 1 – Introduction Definition of Refrigeration

re·frig·er·a·tion (n.) Mechanical refrigeration is the process of using a volatile fluid to absorb heat from a lower temperature place, raising the fluid’s pressure and temperature so it can be rejected to a higher temperature place

Section 1 – Introduction Basic Principals

• Heat is a form of energy • First law of : Energy can neither be created or destroyed • Heat flows from a higher temperature to a lower temperature • Heat energy can move by one of three methods of Three Types of Heat Transfer

Conduction – Transfer by contact

Convection – May be natural or forced transfer by density currents and fluid motion

Radiation – Transfer by electromagnetic waves

Mechanical refrigeration uses the first two. Two Forms of Heat Energy

• – Associated with molecular movement – Measured with a thermometer • – Change of state • Latent heat of fusion (solid to liquid) • Latent heat of vaporization (liquid to gas) • Latent heat of sublimation (solid to gas) Sensible Heat of Water 212

132

100 ° F

42 Temperature Temperature 32

0 0 10 100 180 (Btu/lb) Latent Heat Total Heat (Enthalpy) = Sensible Heat + Latent Heat

212°F liquid 212°F gas

Latent heat cannot be measured on a thermometer Change of State Change of State

Latent Heat of Fusion Latent Heat of Vaporization

1 lb ice 32° F

970 Btu/lb 32° F 144 Btu/lb Temperature-Enthalpy Plot

Example: R-718 (water) 1 pound at standard barometric pressure

212 ° F Latent Heat of Latent heat Vaporization of fusion

Temperature Temperature 970 Btu 32 Subcooled Solid

-176 -144 0 180 1150 Enthalpy (Btu/lb) (Sensible + Latent Heat) Superheat

Saturated Vapor Pressure is constant @ 212° F @14.7 psia

Superheated Vapor @ 242° F

212° F Water Superheat t2 – t1 = 30° F Temperature-Enthalpy Plot

242 Saturated Superheated Liquid Vapor

212 ° F Latent Heat of Saturated Vaporization Subcooled Vapor Liquid Condensation Evaporation Temperature Temperature 32 1 Btu/lb 970 Btu/lb 0.45 Btu/lb

-176 -144 0 180 1150 1160 Enthalpy (Btu/lb) NOTE: THERE IS NO TIME ON THIS SCALE Rate of heat transfer Btu is a measure of quantity Btuh is a measure of quantity per unit of time (hour)

288,000 Btu 1 Day

1 “Ton” = 12,000 Btu 1 hour 1 Ton of Ice 12,000 Btuh

200 Btu 1 Min

Latent heat of fusion 144 Btu ∗ 2000 lb = 288,000 Btu Four Laws of System Operation

No Flow 70° 70° Heat only moves from higher temperature to 70° a lower temperature

32° The greater the difference 21270°° the greater the flow

70° Four Laws of System Operation

1. Heat only moves from a Sensible Heat higher temperature to a lower temperature

71° F

70° F

1 Btu / lb Four Laws of System Operation

1. Heat only moves from a Latent Heat higher temperature to a lower temperature Saturated 2. A large amount of energy Vapor 212° F is required to change the Change of state of matter state occurs at a constant temperature

212° F

970 Btu/lb Four Laws of System Operation

1. Heat only moves from a higher temperature to a lower temperature

2. A large amount of energy is required to change the state of matter

3. The temperature and energy required to change state are a function of pressure Pressure Affects the Boiling Point

0 psig 5 psig 50 psig

212° F 227° F 298° F

970 Btu/lb 960 Btu/lb 912 Btu/lb

If we control the pressure, we control the boiling point Measuring Pressure Absolute Pressure Scales Compared psia in. Hg Abs

14.696 psia 29.921 in. Hg (sea level)

12.23 psia 24.9 in. Hg (5000 ft above sea level) PRESSURE PRESSURE

0 psia 0 in. Hg (no atmosphere)

0 psig = 14.696 psia MERCURY Refrigerant Boiling Points

Water 212° F

HFC-134a -15° F

HCFC-22 -41° F

-40° F HFC-410A -62° F Four Laws of System Operation

1. Heat only moves from a higher temperature to a lower temperature

2. A large amount of energy is required to change the state of matter

3. The temperature and energy required to change state are a function of pressure

4. Fluid flow only occurs if a pressure difference exists Pressure Difference Creates Flow

Flow may be caused by: • Static pressure difference • Pressure difference • Mechanical work Static Suction

Pressure

Vapor Four Laws of System Operation

1. Heat only moves from a higher temperature to a lower temperature 2. A large amount of energy is required to change the state of matter 3. The temperature and energy required to change state are a function of pressure 4. Fluid flow only occurs if a pressure difference exists

The Mechanical Refrigeration Cycle Four Components Are Required

3. Heat rejecting section

4. Pressure/ flow control 2. Vapor valve pump

1. Heat absorbing section An Open Cycle

Refrigerant Under Pressure

14.7 psia

R410a -60.8°F The Closed Cycle

Metering Device

Evaporator

Condenser 2-Pressure Zone

Typical conditions 120° F / 431.6 psia at peak load for: 120° F / 274.7 psia HCFC-22 Condenser HFC-410A (Rejects Heat)

Hot Gas Line Compressor High Side

Metering Low Side Device

Evaporator (Absorbs Heat) Suction Line

45° F / 90.8 psia 45° F / 144.5 psia Pressure-Enthalpy Diagram Refrigeration Cycle

Saturated Condensing Pc

LIFT PRESSURE Saturated Suction Ps

RE

ENTHALPY The Evaporator Absorbs Heat

60° F Liquid and Vapor

All Vapor 80° F Basic System Components Every system has four basic components

Evaporator Absorbs the heat from the space or the load Mostly liquid refrigerant boils () in the tubes as the heat load is absorbed, Air out: 59.7° F db / 57.3° F wb changing to vapor often Cold with some superheat Mixture 55° F 45° F 90.8 psia 90.8 psia SET Cold Evaporator Vapor Air in: 80° F db / 67° F wb Pressure-Enthalpy Diagram Refrigeration Cycle

Saturated Condensing Pc

LIFT PRESSURE Saturated Suction Ps

RE

ENTHALPY Basic System Components

Hot Vapor Every system has four 120° F basic components 274.7 psia SDT Evaporator Compressor Compressor Raises the pressure from the evaporator SST pressure to the condensing temperature and creates a pressure differential to Air out: 59.7° F db / 57.3° F wb cause refrigerant flow

55° F 45° F 90.8 psia 90.8 psia SET Cold Evaporator Vapor Air in: 80° F db / 67° F wb Pressure-Enthalpy Diagram Refrigeration Cycle

Saturated Condensing Pc Tc

HEAD

TEMP LIFT PRESSURE Saturated Suction Ps Ts

RE COMP

ENTHALPY Compressor Suction

Suction Line

HCFC-22 90.8 psia & 45° F SST Causes flow by 90.8 psia & 55° F actual creating a low HFC -410A pressure area 144.5 psia & 45° F SST 144.5 psia & 55° F actual

Actual is the temperature with superheat Compressor Discharge

Hot Gas Line Suction Line

HCFC-22 HCFC-22 274.7 psia & 120° F SDT 90.8 psia & 45° F SST 274.7 psia & 170° F actual 90.8 psia & 55° F actual HFC-410A HFC -410A 431.6 psia & 120° F SDT 144.5 psia & 45° F SST 431.6 psia & 170° F actual 144.5 psia & 55° F actual

High Side Low Side Compresses the vapor to raise the pressure and temperature above the condensing temperature Basic System Components Condenser Air out: 115° F db Every system has four 108° F 120° F basic components 274.7 psia 274.7 psia SCT SDT Evaporator Air in: 95° F Compressor Compressor SST Condenser Air out: 59.7° F db / 57.3° F wb Rejects the heat from the load and system losses Highly superheated refrigerant 55° F condenses in the tubes as heat load is 45° F 90.8 psia 90.8 psia SET rejected and changes back to a liquid and is subcooled Evaporator Air in: 80° F db / 67° F wb Pressure-Enthalpy Diagram Refrigeration Cycle Condenser

Saturated Condensing Pc

LIFT PRESSURE Saturated Suction Ps

RE COMP

ENTHALPY Example – Air-Cooled

(HCFC-22) (HFC-410A) 95° F Air

R-22 R-410A Actual SCT 120° F Condensing 180° F

Actual Liquid 108° F

Subcooling = ? °F Example – Water-Cooled Condenser LEAVING DIFFERENCE

Hot Gas Line To Tower 95° F

105° F SCT

Liquid Line

100° F Actual From Tower 85° F The Metering Device TXV: Thermostatic Expansion Valve

HCFC-22 HCFC-22 274.7 psia & 120° F SCT 90.8 psia & 45° F SET 274.7 psia & 108° F actual 90.8 psia & 45° F actual Low Side High Side

HFC-410A 431.6 psia & 120° F SCT HFC-410A 431.6 psia & 108° F actual 144.5 psia & 45° F SET TXV: 144.5 psia & 45° F actual - Controls the refrigerant flow rate - Reduces the pressure of the refrigerant gas - Refrigerant gas temperature is reduced Refrigeration Cycle with Subcooling

SUBCOOLING tc Pc

TXV

PRESSURE Vgs Ps ts

RE

hfc ENTHALPY hgs Refrigeration Cycle with Subcooling

SUBCOOLING tc Pc

PRESSURE Vgs Ps ts

Superheat RE

hfc ENTHALPY hgs Compressor Energy

SCT SAT. LIQUID Heat Rejection 97

82

Reduced Lift Pressure

42 Refrigerant Effect SST (Capacity) SAT. VAPOR

Enthalpy Basic System Components Condenser Air out: 115° F db Every system has four 108° F 120° F basic components 274.7 psia 274.7 psia SCT SDT Evaporator Air in: 95° F Compressor Compressor SST Metering Device Condenser Air out: 59.7° F db / 57.3° F wb Metering Device 55° F Regulates the flow and decreases 45° F 90.8 psia the pressure from 90.8 psia SET condensing pressure to evaporator pressure Evaporator Air in: 80° F db / 67° F wb Refrigeration Lines Liquid Line

Evaporator Coil

Condenser Coil Hot Gas Suction Line Line Other System Components In addition to the four basic components, refrigeration systems may have other components that enhance system safety, performance, or reliability: • System protectors • Storage devices • Performance devices • System pressure regulators • Valves and solenoids • Temperature and pressure controls • Oil controls Refrigeration Cycle Accessories System Protectors • Filter-Driers – Normally in the liquid line and sometimes in the suction line • Removes particles,water, acids, solids and sludge

• Sight Glasses – Located in the liquid line • Indicates moisture and is sometimes used to determine charge

• Mufflers – Located in the hot gas line • Reduces gas pulsations Refrigeration Cycle Accessories Storage Devices • Accumulators – In the suction before the compressor – Used on heat pumps and long line applications • Protects against liquid returning to the compressor

• Receivers – In the liquid line after the condenser – Not often used in comfort • Stores refrigerant Refrigeration Cycle Accessories Performance Devices • Desuperheaters – In the hot gas line after the condenser – Used in some systems • Heats water for domestic use • Subcoolers – In the liquid line after the condenser – Uses water to cool the liquid refrigerant • Reduces flash gas and increases efficiency • – Located in the liquid line • Reduces flash gas and increases efficiency Refrigeration Cycle Accessories System Pressure Regulators • Outlet Crankcase Pressure – In the suction line after the condenser – Controls maximum outlet pressure – Used primarily in low- temperature refrigeration • Prevents compressor overload • Inlet Evaporator Pressure – In the suction line – Controls minimum pressure – Used primarily in refrigeration with multiple evaporators • Maintains consistent suction pressure Refrigeration Cycle Accessories System Pressure Regulators • Hot Gas Bypass – Located between the hot gas discharge line and the TXV outlet – Admits a small amount of gas back to the evaporator without going to the condenser • Provides stable low load operation • Head Pressure Control – Located in the liquid line at the condenser outlet – Regulates the condenser capacity by allowing refrigerant to flood the condenser tubes • Provides stable low ambient operation Refrigeration Cycle Accessories

Refrigerant Valves – Many locations – Controls flow – Holds refrigerant for capacity control, off-cycle charge control, and service • Hand • Solenoid Valves • Check Valves • Relief Valves • Special (defrost/heat reclaim) Refrigeration Cycle Accessories

Temperature and Pressure Controls – Many locations in the system – For system control and safety

Oil Controls – Located in the hot gas line – Assures oil return to the – Not often used in comfort AC Heat Pump System A heat pump system has the same four basic components but adds a Reversing Valve and Accumulator Evaporator Compressor Condenser Metering Device (2) Reversing Valve Accumulator Heat Pump System

Ball Valve Check Valve TXV

4-Way INDOOR COIL Valve

Compressor Filter Drier

OUTDOOR COIL OUTDOOR

Accumulator TXV

Accurator Cooling Mode Heat Pump System

Ball Valve Check Valve TXV

4-Way INDOOR COIL Valve

Compressor Filter Drier

OUTDOOR COIL OUTDOOR

Accumulator TXV

Accurator Heating Mode Refrigeration Lines Liquid Line

Evaporator Coil

Condenser Coil Hot Gas Suction Line Line Indoor Coil Loading - Tons Per Circuit Refrigerant velocity must be high enough to keep compressor oil entrained with refrigerant vapor.

TXV

Refrigerant paths Minimum tons/circuit: 3/8” tubes = 0.4 tons/circuit 5/8” tubes = 0.6 tons/circuit Indoor Unit – Refrigerant Circuits Single Circuit Distributor Dual Circuit

Solenoid TXV

LIQUID LIQUID LINE LINE

TXV Filter Drier Distributor Tons Per Circuit Example

Model # of coil splits # of circuits/splits # of circuits total 007 1 12 12 008 1 15 15 012 2 9 18 014 2 9 18 016 2 12 24 024 2 13 26 028 2 15 30 034 2 18 36 Standard – Unloaded capacity, 7 tons ACCEPTABLE 7 tons/18 circuits = 0.4 tons/circuit With additional unloading – Unloaded capacity, 3.3 tons TOO LOW! 3.3 tons / 18 circuits = 0.2 tons/circuit

Add capacity control solenoid valve ACCEPTABLE Now 3.3 tons / 9 circuits = 0.4 tons/circuit

Elevation LIQUID LINE – 1-2 ton UNITS LIQUID LINE

MAX Max Allow. Max Allow. ALLOW. UNIT Pressure Temp LIFT Drop Loss (ft) (psi) (°F)

012 65 014 67 016 82 7 2 024 87 NOTE: Data above is for units at 45° F saturated suction and 95° F entering air.

LIQUID LIFT Suction Riser

• Refrigerant velocity in suction riser must be high enough to entrain compressor oil with the refrigerant

• Double suction riser or reduced diameter riser may be required

• Consult manufacturer’s recommendations Refrigerant Piping (6-10 Ton, R-22)

UNIT SIZE

Refer to manufacturer’s recommendations DO NOT bury refrigerant piping underground! Maximum Length of Refrigerant Piping

• Piping length depends on the application

• Heat pumps – 100 linear feet

• Consult manufacturer’s recommendations Long Line Applications LONG LINE = 75 LINEAR FEET OR LONGER

Lift vs. Run

LIFT Long Lines Require: 1.Liquid line solenoid valve(s) 2.Suction line accumulator(s)

Refrigerants What is a Refrigerant

A refrigerant is a fluid that absorbs heat and changes from vapor to liquid phase at reasonable pressures and temperatures as encountered in mechanical refrigeration.

PRESSURE psia

°F Water HCFC-22 HFC-410A HFC-134a CO2 Propane -40 0.00186 15.26 26 7.43 145.77 16.1

0 0.0185 38.73 64 21.62 305.80 38.4

40 0.122 82.28 132 49.70 567.50 78.6

100 0.950 210.70 340 138.80 X 188.6

130 2.225 311.60 500 213.40 X 273.3

212 14.696 *CP *CP 587.20 X X

*Critical Point, pressure psia What Makes a Good Refrigerant Safe • Efficient • Stable • Cost Effective • Compatible 1. Non-toxic and non-flammable 2. Reasonable operating pressures 3. Leakage resistance 4. Large heat of vaporization 5. Relatively low specific volume 6. Low liquid specific heat (reduced flash gas) 7. Easy to detect leaks 8. Compatible with oils (vapor side) 9. High coefficient of heat transfer 10. Easy to handle and cost effective 11. Non-corrosive and chemically stable 12. No Ozone Depletion Potential (ODP) or Global Warming Potential (GWP)

Summary • Discussed mechanical refrigeration terms • Described how heat is transferred and which methods are primarily used in the refrigeration cycle • Described the four principles of the refrigeration process • Explained the function of the four system components • Listed characteristics of a good refrigerant 2013 RM ASHRAE Technical Conference Thank You This completes the presentation.