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Training Session on Refrigeration Training Session on Refrigeration & Air Conditioning& Air Conditioning
Refrigeration & Air Refrigeration & Air ConditioningConditioning
Presentation by
“Mohammad Salim”
M/s Unitech Ltd., Gurgaon.
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Training Agenda: Refrigeration & Training Agenda: Refrigeration & Air ConditioningAir Conditioning
Introduction
Reference Handbooks/Standards
Type of refrigeration
Applied Psychrometric
Heat Load Calculation
Air Duct Design
Pressurization System
Chilled/Condenser Water Piping Design
Compressors
Condensers & Evaporators
Expansion Devices
Cooling Tower
Assessment of refrigeration and AC
Energy efficiency opportunities
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IntroductionIntroduction
How does it work?
High Temperature Reservoir
Low Temperature Reservoir
R Work Input
Heat Absorbed
Heat Rejected
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IntroductionIntroduction
Thermal energy moves from left to right through five loops of heat transfer:
How does it work?
(Bureau of Energy Efficiency, 2004)
1)
Indoor air loop
2)
Chilled water loop
3)
Refrigerant loop
4)
Condenser water loop
5)
Cooling water loop
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IntroductionIntroduction
AC options / combinations:
AC Systems
• Air Conditioning (for comfort / machine)
• Split air conditioners
• VRV System in Group Housing etc.
• Fan coil units in a larger system
• Air handling units in a larger system
• Evaporating Cooling in a larger system
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IntroductionIntroduction
• Small capacity modular units of direct expansion type (50 Tons of Refrigeration)
• Centralized chilled water plants with chilled water as a secondary coolant (50 – 250 TR)
• Brine plants with brines as lower temperature, secondary coolant (>250 TR)
Refrigeration systems for industrial processes
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IntroductionIntroduction
• Bank of units off-site with common
• Chilled water pumps
• Condenser water pumps
• Cooling towers
• More levels of refrigeration/AC, e.g.
• Comfort air conditioning (20-25 oC)
• Chilled water system (8 – 10 oC)
• Brine system (< 0 oC)
Refrigeration at large companies
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Reference Handbooks/Standards
Introduction
Reference Handbooks/Standards
Type of refrigeration
Applied Psychrometric
Heat Load Calculation
Air Duct Design
Pressurization System
Chilled/Condenser Water Piping Design
Compressors
Condensers & Evaporators
Expansion Devices
Cooling Tower
Assessment of refrigeration and AC
Energy efficiency opportunities
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Reference Handbooks/Standards
ASHRAE Handbook of FundamentalsASHRAE Handbook of Refrigeration ASHRAE Handbook of Application ASHRAE Handbook of System & Equipments ASHRAE Standards 62.1 ASHRAE Standards 90.1 ISHRAE Weather Data Carrier Handbook NBC-2005 LEED-2009 NFPA-92A ECBC-2007 Heat and Mass Transfer SMACNA Standard Indian Standards
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Types of RefrigerationTypes of Refrigeration
Introduction
Reference Handbooks/Standards
Types of refrigeration
Applied Psychrometric
Heat Load Calculation
Air Duct Design
Pressurization System
Chilled/Condenser Water Piping Design
Compressors
Condensers & Evaporators
Expansion Devices
Cooling Tower
Assessment of refrigeration and AC
Energy efficiency opportunities
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Types of RefrigerationTypes of Refrigeration
• Vapour Compression Refrigeration (VCR): uses mechanical energy
• Vapour Absorption Refrigeration (VAR): uses thermal energy
Refrigeration systems
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Types of RefrigerationTypes of Refrigeration
Vapour Compression Refrigeration
• Highly compressed fluids tend to get colder when allowed to expand
• If pressure high enough
• Compressed air hotter than source of cooling
• Expanded gas cooler than desired cold temperature
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Types of RefrigerationTypes of Refrigeration
Vapour Compression Refrigeration
Two advantages
• Lot of heat can be removed (lot of thermal energy to change liquid to vapour)
• Heat transfer rate remains high (temperature of working fluid much lower than what is being cooled)
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Types of RefrigerationTypes of Refrigeration
Vapour Compression Refrigeration
Refrigeration cycle
Condenser
Evaporator
High Pressure
Side
Low Pressure
Side
CompressorExpansion Device
1 2
3
4
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Types of RefrigerationTypes of Refrigeration
Vapour Compression Refrigeration
Refrigeration cycle
Low pressure liquid refrigerant in evaporator absorbs heat and changes to a gas
Condenser
Evaporator
High Pressure
Side
Low Pressure
Side
CompressorExpansion Device
1 2
3
4
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Types of RefrigerationTypes of Refrigeration
Vapour Compression Refrigeration
Refrigeration cycle
The superheated vapour enters the compressor where its pressure is raised
Condenser
Evaporator
High Pressure
Side
Low Pressure
Side
CompressorExpansion Device
1 2
3
4
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Types of RefrigerationTypes of Refrigeration
Vapour Compression Refrigeration
Refrigeration cycle
The high pressure superheated gas is cooled in several stages in the condenser
Condenser
Evaporator
High Pressure
Side
Low Pressure
Side
CompressorExpansion Device
1 2
3
4
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Types of RefrigerationTypes of Refrigeration
Vapour Compression Refrigeration
Refrigeration cycle
Liquid passes through expansion device, which reduces its pressure and controls the flow into the evaporator
Condenser
Evaporator
High Pressure
Side
Low Pressure
Side
CompressorExpansion Device
1 2
3
4
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Types of RefrigerationTypes of Refrigeration
Vapour Compression Refrigeration
Type of refrigerant
• Refrigerant determined by the required cooling temperature
• Chlorinated fluorocarbons (CFCs) or freons: R-11, R-12, R-21, R-22 and R-502
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Types of RefrigerationTypes of Refrigeration
Vapour Compression Refrigeration
Choice of compressor, design of condenser, evaporator determined by
• Refrigerant
• Required cooling
• Load
• Ease of maintenance
• Physical space requirements
• Availability of utilities (water, power)
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Types of RefrigerationTypes of Refrigeration
Vapour Absorption Refrigeration
Condenser Generator
Evaporator
AbsorberCold Side
Hot Side
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Types of RefrigerationTypes of Refrigeration
Vapour Absorption Refrigeration
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Types of RefrigerationTypes of Refrigeration
Vapour Absorption Refrigeration
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Vapour Absorption Refrigeration
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Types of RefrigerationTypes of Refrigeration
Refrigerant-absorbent combinations for VARS
The desirable properties of refrigerant-absorbent mixtures for VARS are: i The refrigerant should exhibit high solubility with solution in the absorber. This is to say that it should exhibit negative deviation from Raoult’s law at absorber.
ii. There should be large difference in the boiling points of refrigerant and absorbent (greater than 200oC), so that only refrigerant is boiled-off in the generator. This
ensures that only pure refrigerant circulates through refrigerant circuit (condenser-expansion valve-evaporator) leading to isothermal heat transfer in evaporator and condenser.
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Types of RefrigerationTypes of Refrigeration
iii. It should exhibit small heat of mixing so that a high COP can be achieved. However, this requirement contradicts the first requirement. Hence, in practice a trade-off is required between solubility and heat of mixing.
iv. The refrigerant-absorbent mixture should have high thermal conductivity and low viscosity for high performance.
v. It should not undergo crystallization or solidification inside the system.
vi. The mixture should be safe, chemically stable, non-corrosive, inexpensive and should be available easily.
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Types of RefrigerationTypes of Refrigeration
The most commonly used refrigerant-absorbent pairs in commercial systems are: 1. Water-Lithium Bromide (H2O-LiBr) system for above 0oC applications such as air conditioning. Here water is the refrigerant and lithium bromide is the absorbent. 2. Ammonia-Water (NH3-H2O) system for refrigeration applications with ammonia as refrigerant and water as absorbent. Of late efforts are being made to develop other refrigerant-absorbent systems using both natural and synthetic refrigerants to overcome some of the limitations of (H2O-LiBr) and (NH3-H2 O) systems. Currently, large water-lithium bromide (H2O-LiBr) systems are extensively used in air conditioning applications, where as large ammonia-water (NH3-H2O) systems are used in refrigeration applications, while small ammonia-water systems with a third inert gas are used in a pumpless form in small domestic refrigerators (triple fluid vapour absorption systems).
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Types of RefrigerationTypes of Refrigeration
Evaporative Cooling
(Adapted from Munters, 2001)
Cold Air
Hot Air
Sprinkling Water
• Air in contact with water to cool it close to ‘wet bulb temperature’
• Advantage: efficient cooling at low cost
• Disadvantage: air is rich in moisture
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Applied PsychrometricApplied Psychrometric
Introduction
Reference Handbooks/Standards
Type of refrigeration
Applied Psychrometric
Heat Load Calculation
Air Duct Design
Pressurization System
Chilled/Condenser Water Piping Design
Compressors
Condensers & Evaporators
Expansion Devices
Cooling Tower
Assessment of refrigeration and AC
Energy efficiency opportunities
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Heat Load CalculationHeat Load Calculation
Introduction
Reference Handbooks/Standards
Type of refrigeration
Applied Psychrometric
Heat Load Calculation
Air Duct Design
Pressurization System
Chilled/Condenser Water Piping Design
Compressors
Condensers & Evaporators
Expansion Devices
Cooling Tower
Assessment of refrigeration and AC
Energy efficiency opportunities
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Heat Load CalculationHeat Load Calculation
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Air Duct DesignAir Duct Design
Introduction
Reference Handbooks/Standards
Type of refrigeration
Applied Psychrometric
Heat Load Calculation
Air Duct Design
Pressurization System
Chilled/Condenser Water Piping Design
Compressors
Condensers & Evaporators
Expansion Devices
Cooling Tower
Assessment of refrigeration and AC
Energy efficiency opportunities
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Air Duct DesignAir Duct Design
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TABLE 7 – RECOMMENDED MAXIMUM DUCT VELOCITIES FOR LOW VELOCITY SYSTEMS (FPM)
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Methods of Duct Design
1- Equal friction Method
2- Static Regain Method
1-Equal Friction Method
This method of sizing is used for supply, exhaust andreturn air duct systems and employs the same friction lollper foot of length for the entire system. The equal frictionmethod is superior to velocity reduction since it requiresless balancing for symmetrical layouts. If a design has a
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Air Duct DesignAir Duct Design
mixture of short and long runs, the shortest run requires considerable dampering. Such a system is difficult to balance since the equal friction method makes no provision for equalizing pressure drops in branches of for providing the same static pressure behind each air terminal.
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Air Duct DesignAir Duct Design
Example 4 – Equal Friction Method of Designing DuctsGiven:Duct systems for general office (Fig.47).Total air quantity – 5400 cfm18 air terminals – 300 cfm eachOperating pressure forall terminals – 0.15 in. wgRadius elbows, R/D = 1.25Find:1.Initial duct velocity, area, size and friction rate in the duct section from the fan to the first branch.2.Size of remaining duct runs.3. Total equivalent length of duct run with highest resistance.4. Total static pressure required at fan discharge
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Air Duct DesignAir Duct Design
2-Static Regain Method
The basic principle of the static regain method is tosize a duct run so that the increase in static pressure(regain due to reduction in velocity) at each branch or airterminal just offsets the friction loss in the succeedingsection of duct. The static pressure is then the samebefore each terminal and at each branch.The following procedure is used to design a ductsystem by this method: select a starting velocity at the fandischarge from Table 7 and size the initial duct sectionfrom Table 6.
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Air Duct DesignAir Duct Design
The remaining sections of duct are sized from Chart10 (L!Q Ratio) and Chart 11 (Low Velocity Static Regain).Chart 10 is used to determine the L/Q ratio knowing theair quantity (Q) and length (L) between outlets orbranches in the duct section to be sized by static regain.This length (L) is the equivalent length between theoutlets or branches, including elbows, excepttransformations. The effect of the transformation section isaccounted for in “Chart 11 3 Static Regain.” Thisassumes that the transformation section is laid outaccording to the recommendation presented in thischapter.
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Pressurization SystemPressurization System
Introduction
Reference Handbooks/Standards
Type of refrigeration
Applied Psychrometric
Heat Load Calculation
Air Duct Design
Pressurization System
Chilled/Condenser Water Piping Design
Compressors
Condensers & Evaporators
Expansion Devices
Cooling Tower
Assessment of refrigeration and AC
Energy efficiency opportunities
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Pressurization SystemPressurization System
STAIRCASE PRESSURIZATION CALCULATION FOR BASEMENT PART - A BASEMENT TO GROUND FLOOR)
Q1 = Kf A √ Δ P
Q1 = Air Leakage in Cu. M./ Sec.
A = Area of Leakage in Sq.M.
Δ P = Pressure Difference in Pascal ( 50 Pa)
Kf = Coefficient 0.839
No. of Floors = Basement to Ground Floor = 2
No. of Doors = 2
Door Size = 1.2 M x 2.1 M
Gap Between door and Frame/Floor = 6 mm at Top and on side
= 15 mm at Bottom
Area of Leakage Between Door & Frame
= 2 x H x gap (side) + 1 x W x gap (Top) + 1 x W x gap (Bottom )
= 2 x 2.1 x 6/1000 + 1 x 1.2 x 6/1000 + 1 x 1.2 x 15/1000
= 0.0252 + 0.0072 + 0.018
= 0.0504 Sq. M.
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Pressurization SystemPressurization System
Area of Leakage in Closed Condition/Door = 0.0504 Sq. M.
Total Leakage Area for 2 No. Doors = 0.0504 x 2
= 0.10 Sq.M.
Q1 = 0.839 x 0.10 x √ 50
= 0.60 Cu. M/Sec.
= 1270 CFM
Leakage of Air Thru 2 No. Open Door ( 1 No. at affected floor + 1 No. at Exit to Building )
Q2 = Area of Doors x Velocity
= 2.1 x 1.2 x2 No. x 1.0 M/sec.
= 5.04 Cu. M./Sec
= 10671 CFM
Total Required Air Quantity = Q1 + Q2
= 1270 + 10671
= 11941 CFM
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LIFT WELL PRESSURIZATION CALCULATION
TOWER T1 (G+13)- 5 Nos.
Q = Kf A √ Δ P
Q = Air Leakage in Cu. M./ Sec.
A = Area of Leakage in Sq.M.
Δ P = Pressure Difference in Pascal ( 50 Pa)
Kf = Coefficient 0.839
No. of Floors = Lower Basement (Part-A) to 13th Floor = 16
No. of Doors = 16
Door Size = 2.1 M x 1.2 M
Area of Leakage Between Lift Door & Wall/ Door = 0.065 Sq. M.
Total Leakage Area for 16 No. Doors = 0.065 x 16
= 1.04 Sq.M.
Q = 0.839 x 1.04 x √ 50
= 6.17 Cu. M/Sec.
= 13063 CFM
Fan Capacity for Two Lift Well = 13063x2
= 26126 CFM
Say = 26500 CFM
1 No. 26500 CFM DIDW Centrifugal Fan Section For Fresh Air Supply
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Chilled/Condenser Water Piping Chilled/Condenser Water Piping DesignDesign
Introduction
Reference Handbooks/Standards
Type of refrigeration
Applied Psychrometric
Heat Load Calculation
Air Duct Design
Pressurization System
Chilled/Condenser Water Piping Design
Compressors
Condensers & Evaporators
Expansion Devices
Cooling Tower
Assessment of refrigeration and AC
Energy efficiency opportunities
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CompressorsCompressors
Introduction
Reference Handbooks/Standards
Type of refrigeration
Applied Psychrometric
Heat Load Calculation
Air Duct Design
Pressurization System
Chilled/Condenser Water Piping Design
Compressors
Condensers & Evaporators
Expansion Devices
Cooling Tower
Assessment of refrigeration and AC
Energy efficiency opportunities
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Condensers & EvaporatorsCondensers & Evaporators
Introduction
Reference Handbooks/Standards
Type of refrigeration
Applied Psychrometric
Heat Load Calculation
Air Duct Design
Pressurization System
Chilled/Condenser Water Piping Design
Compressors
Condensers & Evaporators
Expansion Devices
Cooling Tower
Assessment of refrigeration and AC
Energy efficiency opportunities
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Expansion DevicesExpansion Devices
Introduction
Reference Handbooks/Standards
Type of refrigeration
Applied Psychrometric
Heat Load Calculation
Air Duct Design
Pressurization System
Chilled/Condenser Water Piping Design
Compressors
Condensers & Evaporators
Expansion Devices
Cooling Tower
Assessment of refrigeration and AC
Energy efficiency opportunities
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Expansion DevicesExpansion Devices
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Introduction
Reference Handbooks/Standards
Type of refrigeration
Applied Psychrometric
Heat Load Calculation
Air Duct Design
Pressurization System
Chilled/Condenser Water Piping Design
Compressors
Condensers & Evaporators
Expansion Devices
Cooling Tower
Assessment of Refrigeration and AC
Energy efficiency opportunities
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Introduction
Reference Handbooks/Standards
Type of refrigeration
Applied Psychrometric
Heat Load Calculation
Air Duct Design
Pressurization System
Chilled/Condenser Water Piping Design
Compressors
Condensers & Evaporators
Expansion Devices
Cooling Tower
Assessment of Refrigeration and AC
Energy efficiency opportunities
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• Cooling effect: Tons of Refrigeration
• TR is assessed as:
Assessment of Refrigeration
1 TR = 3024 kCal/hr heat rejected
TR = Q x⋅Cp x⋅ (Ti – To) / 3024
Q = mass flow rate of coolant in kg/hr Cp = is coolant specific heat in kCal /kg deg C Ti = inlet, temperature of coolant to evaporator (chiller) in 0C To = outlet temperature of coolant from evaporator (chiller) in 0C
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Specific Power Consumption (kW/TR)
• Indicator of refrigeration system’s performance
• kW/TR of centralized chilled water system is sum of• Compressor kW/TR
• Chilled water pump kW/TR
• Condenser water pump kW/TR
• Cooling tower fan kW/TR
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Coefficient of Performance (COPCarnot)
• Standard measure of refrigeration efficiency
• Depends on evaporator temperature Te and condensing temperature Tc:
• COP in industry calculated for type of compressor:
COPCarnot = Te / (Tc - Te)
Cooling effect (kW)COP =
Power input to compressor (kW)
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COP increases with rising evaporator temperature
(Te)
COP increases with decreasing condensing
temperature (Tc)
Assessment of Refrigeration and ACAssessment of Refrigeration and AC
Assessment of Refrigeration
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Measure
• Airflow Q (m3/s) at Fan Coil Units (FCU) or Air Handling Units (AHU): anemometer
• Air density ρ (kg/m3)
• Dry bulb and wet bulb temperature: psychrometer
• Enthalpy (kCal/kg) of inlet air (hin) and outlet air (Hout): psychrometric charts
Calculate TR ( )3024
h h ρ Q TR outin −××
=
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Assessment of Air Conditioning
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Indicative TR load profile
• Small office cabins: 0.1 TR/m2
• Medium size office (10 – 30 people occupancy) with central A/C: 0.06 TR/m2
• Large multistoried office complexes with central A/C: 0.04 TR/m2
Assessment of Air Conditioning
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• Accuracy of measurements
• Inlet/outlet temp of chilled and condenser water
• Flow of chilled and condenser water
• Integrated Part Load Value (IPLV)
• kW/TR for 100% load but most equipment operate between 50-75% of full load
• IPLV calculates kW/TR with partial loads
• Four points in cycle: 100%, 75%, 50%, 25%
Considerations for Assessment
Assessment of Refrigeration and ACAssessment of Refrigeration and AC
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Introduction
Reference Handbooks/Standards
Type of refrigeration
Applied Psychrometric
Heat Load Calculation
Air Duct Design
Pressurization System
Chilled/Condenser Water Piping Design
Compressors
Condensers & Evaporators
Expansion Devices
Cooling Tower
Assessment of Refrigeration and AC
Energy Efficiency Opportunities
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
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1. Optimize process heat exchange
2. Maintain heat exchanger surfaces
3. Multi-staging systems
4. Matching capacity to system load
5. Capacity control of compressors
6. Multi-level refrigeration for plant needs
7. Chilled water storage
8. System design features
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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
High compressor safety margins: energy loss
1. Proper sizing heat transfer areas of heat exchangers and evaporators
•Heat transfer coefficient on refrigerant side: 1400 – 2800 Watt/m2K
•Heat transfer area refrigerant side: >0.5 m2/TR
2. Optimum driving force (difference Te and Tc): 1oC raise in Te = 3% power savings
1. Optimize Process Heat Exchange
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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
Evaporator Temperature (0C)
Refrigeration Capacity*(tons)
Specific Power Consumption (kW/TR)
Increase kW/TR (%)
5.0 67.58 0.81 -
0.0 56.07 0.94 16.0
-5.0 45.98 1.08 33.0
-10.0 37.20 1.25 54.0
-20.0 23.12 1.67 106.0
(National Productivity Council)Condenser temperature 40◦C
1. Optimize Process Heat Exchange
Condensing Temperature (0C)
Refrigeration Capacity (tons)
Specific Power Consumption (kW /TR)
Increase kW/TR (%)
26.7 31.5 1.17 -
35.0 21.4 1.27 8.5
40.0 20.0 1.41 20.5
*Reciprocating compressor using R-22 refrigerant. Evaporator temperature.-10◦ C
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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
3. Selection of condensers
• Options: • Air cooled condensers
• Air-cooled with water spray condensers
• Shell & tube condensers with water-cooling
• Water-cooled shell & tube condenser• Lower discharge pressure
• Higher TR
• Lower power consumption
1. Optimize Process Heat Exchange
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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
• Poor maintenance = increased power consumption
• Maintain condensers and evaporators• Separation of lubricating oil and refrigerant
• Timely defrosting of coils
• Increased velocity of secondary coolant
• Maintain cooling towers• 0.55◦C reduction in returning water from cooling
tower = 3.0 % reduced power
2. Maintain Heat Exchanger Surfaces
Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
Effect of poor maintenance on compressor power consumption
2. Maintain Heat Exchanger Surfaces
(National Productivity Council)
Condition Te (0C)
Tc (0C)
Refrigeration Capacity* (TR)
Specific Power
Consumption (kW/TR)
Increase kW/TR
(%)
Normal 7.2 40.5 17.0 0.69 -
Dirty condenser 7.2 46.1 15.6 0.84 20.4
Dirty evaporator 1.7 40.5 13.8 0.82 18.3
Dirty condenser and evaporator
1.7 46.1 12.7 0.96 38.7
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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
• Suited for
• Low temp applications with high compression
• Wide temperature range
• Two types for all compressor types
• Compound
• Cascade
3. Multi-Staging Systems
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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
a. Compound
• Two low compression ratios = 1 high
• First stage compressor meets cooling load
• Second stage compressor meets load evaporator and flash gas
• Single refrigerant
b. Cascade
• Preferred for -46 oC to -101oC
• Two systems with different refrigerants
3. Multi-Stage Systems
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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
• Most applications have varying loads
• Consequence of part-load operation • COP increases
• but lower efficiency
• Match refrigeration capacity to load requires knowledge of• Compressor performance
• Variations in ambient conditions
• Cooling load
4. Matching Capacity to Load System
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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
5. Capacity Control of Compressors
• Cylinder unloading, vanes, valves• Reciprocating compressors: step-by-step
through cylinder unloading:
• Centrifugal compressors: continuous modulation through vane control
• Screw compressors: sliding valves
• Speed control• Reciprocating compressors: ensure
lubrication system is not affected
• Centrifugal compressors: >50% of capacity
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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
5. Capacity Control of Compressors
• Temperature monitoring• Reciprocating compressors: return water (if
varying loads), water leaving chiller (constant loads)
• Centrifugal compressors: outgoing water temperature
• Screw compressors: outgoing water temperature
• Part load applications: screw compressors more efficient
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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
Bank of compressors at central plant
• Monitor cooling and chiller load: 1 chiller full load more efficient than 2 chillers at part-load
• Distribution system: individual chillers feed all branch lines; Isolation valves; Valves to isolate sections
• Load individual compressors to full capacity before operating second compressor
• Provide smaller capacity chiller to meet peak demands
6. Multi-Level Refrigeration
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Packaged units (instead of central plant)
• Diverse applications with wide temp range and long distance
• Benefits: economical, flexible and reliable
• Disadvantage: central plants use less power
Flow control
• Reduced flow
• Operation at normal flow with shut-off periods
6. Multi-Level Refrigeration
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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
• Chilled water storage facility with insulation
• Suited only if temp variations are acceptable
• Economical because• Chillers operate during low peak demand
hours: reduced peak demand charges
• Chillers operate at nighttime: reduced tariffs and improved COP
7. Chilled Water Storage
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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
• FRP impellers, film fills, PVC drift eliminators
• Softened water for condensers
• Economic insulation thickness
• Roof coatings and false ceilings
• Energy efficient heat recovery devices
• Variable air volume systems
• Sun film application for heat reflection
• Optimizing lighting loads
8. System Design Features
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