Trane TRG-TRC012-EN User's Manual
Contents
1. A Y male rotor housing slide valve SE The rotors are meshed and fit with very close tolerances within a housing Only the male rotor is driven by the compressor motor The lobes of the male rotor engage and drive the female rotor causing the 2 parts to counter rotate TRG TRC012 EN period one Components compressor Helical Rotors intake In the operation of the helical rotary compressor refrigerant vapor enters the compressor housing through the intake port The intake port in this example is at the top of the compressor housing compressor Helical Rotors intake port pocket of refrigerant vapor The entering refrigerant vapor is at a low suction pressure and fills the grooves or pockets formed by the lobes of the rotors As the rotors turn they push the pockets of refrigerant toward the discharge end of the compressor TRG TRCO12 EN 5 TRANE period one Components compressor Helical Rotors intake port Viewing the compressor from the side shows that after the pockets of refrigerant travel to the right past the intake port area the vapor still at suction pressure is confined within the pockets by the compressor housing compressor Helical Rotors discharge port meshing point Viewing the compressor from the top shows that rotation of the meshed rotor lobes drives the trapped refrigerant vapor to the right ahead of the meshing point TRG TRC2. Air Conditioning Clinic Helical Rotary Water Chillers One of the Equipment Series TRG TRC012 EN Helical Rotary Water Chillers One of the Equipment Series A publication of The Trane Company Worldwide Applied Systems Group TRANE Preface Helical Rotary Water Chillers A Trane Air Conditioning Clinic The Trane Company believes that it s incumbent on manufacturers to serve the industry by regularly disseminating information gathered through laboratory research testing programs and field experience The Trane Air Conditioning Clinic series is one means of knowledge sharing It s intended to acquaint a nontechnical audience with various fundamental aspects of heating ventilating and air conditioning We ve taken special care to make the clinic as uncommercial and straightforward as possible Illustrations of Trane products only appear in cases where they help convey the message contained in the accompanying text This particular clinic introduces the reader to the concept of helical rotary water chillers 1999 American Standard Inc All rights reserved TRG TRC012 EN Contents Introduction 1 period one Components 3 COMPrESSOT huirpubiiiienonc damsoanieaalsobeneddondasilaner 4 OI Sepat saiisine rA AA rt mena de 8 Cond ns r mn dec anono AEAEE 9 Expansion DeVICE ccccceeeeeeeeceee
3. in the condenser to reject heat to air or water at normally available temperatures High pressure liquid refrigerant flows through the expansion device causing a large pressure drop that reduces the refrigerant pressure to that of the evaporator This pressure reduction causes a small portion of the liquid to boil off or flash cooling the remaining refrigerant to the desired evaporator temperature In this chiller the expansion device used is an electronic expansion valve In addition to maintaining the high and low side pressure difference the electronic expansion valve controls the quantity of liquid refrigerant entering the evaporator to ensure that it will be completely vaporized within the evaporator TRG TRC012 EN 11 TRANE 12 period one Components expansion device Orifice Plates ifi to orifice plates evaporator The orifice plate is another type of expansion device found in helical rotary chillers The column of liquid refrigerant creates a head pressure at its base allowing it to pass through the orifices and undergo a pressure drop equal to the head H before it flashes As the load decreases less refrigerant is moved throughout the chiller causing the level of the liquid column to drop This causes additional flashing at the orifice plate which in turn results in feeding less liquid to the evaporator Liquid Vapor Separator refrigerant vapor CTA to compressor n liquid refriger
4. E Water Cooled Series R Chiller Model RTHC Mechanical Operation RLC EB 16 E Series R CenTraVac Chiller Condensing Water Temperature Control RLC EB 4 H Multiple Chiller System Design And Control CON AM 21 E ARI Standard 550 590 1998 Implications For Chilled Water Plant Design Trane Engineers Newsletter 1999 volume 28 no 1 E ASHRAE Handbook Refrigeration E ASHRAE Handbook Systems and Equipment Visit the ASHRAE Bookstore at www ashrae org For information on additional educational materials available from Trane contact your local Trane sales office request a copy of the Educational Materials price sheet Trane order no EM ADV1 or visit our online bookstore at www trane com bookstore TRG TRCO12 EN 43 S TRANE 44 Quiz Questions for Period 1 1 What components of the helical rotary compressor are used to compress the refrigerant What are the 2 functions of the oil supply system presented in this clinic In a flooded shell and tube evaporator is the refrigerant flowing inside or outside of the tubes Name 2 types of expansion devices commonly found in helical rotary water chillers Questions for Period 2 5 pressure enthalpy Using the pressure enthalpy diagram in Figure 63 identify the following processes of the helical rotary water chiller s refrigeration cycle a to b to c to d to Referring again to Figure 63 after the vapor is remov
5. The refrigerant leaves the evaporator as saturated vapor and flows to the suction end of the compressor where it enters the compartment for the suction gas cooled motor Here the refrigerant flows across and cools the motor then enters the compression chamber The refrigerant vapor is compressed in the compressor to a high pressure and temperature Energy input to the motor and compressor is imparted to the refrigerant as superheat Superheated refrigerant vapor leaves the compressor and enters the condenser Water or air flowing through the condenser absorbs heat from the hot high pressure refrigerant This reduction in the heat content of the refrigerant vapor causes it to desuperheat condense into liquid and further sub cool before leaving the condenser to travel to the expansion device The pressure drop created by the expansion process causes a portion of the liquid refrigerant to evaporate The evaporating refrigerant absorbs heat from the remaining liquid refrigerant The resulting mixture of cold liquid and vapor refrigerant enters the liquid vapor separator Here the vapor is separated from the mixture and routed directly to the suction side of the compressor and the remaining liquid refrigerant enters the evaporator The cool low pressure liquid refrigerant enters the distribution system in the evaporator shell and is distributed over the tubes in the evaporator tube bundle absorbing heat from water that flows
6. VAPOR COMPRESSION CYCLE KN avers 352908 Equipment Certification Standards The Air Conditioning amp Refrigeration Institute ARI establishes rating standards for packaged HVAC equipment ARI also certifies and labels equipment through programs that involve random testing of a manufacturer s equipment to verify published performance The overall objective of ARI Standard 550 590 1998 is to promote consistent rating and testing methods for all types and sizes of water chillers with an accurate representation of actual performance It covers factory designed prefabricated water chillers both air cooled and water cooled using the vapor compression refrigeration cycle TRG TRC012 EN TRG TRCO12 EN TRANE period five Application Considerations equipment certification standards ARI Standard 550 590 a Standard rating conditions Common system conditions for published ratings a Integrated Part Load Value IPLV Part load efficiency rating Based on an average single chiller installation Standard operating conditions The standard rating conditions used for ARI certification represent typical design temperatures and flow rates for which water cooled and air cooled systems are designed They are not suggestions for good design practice for a given system they are simply a common rating point Trends toward improved humidity control and energy efficiency have changed some of the actual conditi
7. current chiller designs can properly control the chiller in response to varying evaporator flow rates with the following limitations 35 Trane 36 period five Application Considerations 1 The water flow rate through the chiller s evaporator must stay between the minimum and maximum evaporator bundle flow rates as specified by the chiller manufacturer These limits depend on the specific details of the actual evaporator bundle such as the number of tubes number of passes and geometry of the bundle A method for sensing evaporator water flow through each chiller is the only way to make sure the water flow rate stays within these limits 2 The rate which the evaporator water flow rate changes must be kept below a specified level which is dependent on the level of protection desired For example the maximum rate of change in order to maintain chilled water setpoint is more stringent than the maximum rate of change in order to keep the chiller on line There are 3 common levels of protection desired maintaining chilled water setpoint control keeping the chiller on line and protecting the chiller from damage The limits for these different levels of protection should be obtained from the chiller manufacturer Short Evaporator Water Loops chilled water pump evaporator Short Evaporator Water Loops Proper chilled water temperature control requires that the temperature of the chilled water returning to t
8. imbalance that could cause oil loss problems Controlling the refrigerant pressure difference between the evaporator and condenser of an air cooled chiller is accomplished by varying the flow rate of the air flowing through the condenser coils This control is an integral part of the chiller design TRG TRCO12 EN 33 Trane period five Application Considerations condensing temperature control Cooling Tower Bypass diverting valve 65 F 18 C Controlling the refrigerant pressure difference between the evaporator and condenser of a water cooled chiller is accomplished by varying the temperature or flow rate of the water flowing through the condenser The following are 5 common methods used to control condensing temperature 1 Controlling the temperature of the water leaving the cooling tower by cycling or varying the speed of the cooling tower fans 2 Using a cooling tower bypass pipe to mix warmer leaving condenser water with the colder tower water and control the temperature entering the condenser as illustrated in the accompanying slide 3 Modulating a throttling valve to restrict the flow of water through the condenser 4 Using a chiller bypass pipe to vary the flow rate of water through the condenser 5 Employing a variable speed drive on the condenser water pump to vary the water flow rate through the condenser Each of these strategies has its advantages and disadvantages and selection of the appropriat
9. through the tubes This transfer of heat boils the film of liquid refrigerant on the tube surfaces and the resulting vapor is drawn back to the compressor to repeat the cycle 18 TRG TRC012 EN TRANE period two Refrigeration Cycle helical rotary water chillers Refrigerants a HCFC 22 a HFC 134a a HFC 404a a HFC 407c a HFC 410a Manufacturers are continuously improving their designs of helical rotary water chillers New chillers need to be designed around the characteristics of the refrigerant Today there are 5 strong candidates for use with positive displacement helical rotary chillers They are HCFC 22 HFC 134a HFC 404a HFC 407c and HFC 410a TRG TRCO12 EN 19 S TRANE 20 period two Refrigeration Cycle refrigerants Thermodynamic Characteristics DJ efficiency I capacity pressure 160 140 120 100 80 60 40 HCFC 22 HFC 134a HFC 40da HEC 407 HFC 410a Today the most commonly used refrigerant in helical rotary chillers is HCFC 22 Due to the scheduled phaseout of HCFC 22 most helical rotary chillers will be redesigned using HFC refrigerants Many challenges are encountered when redesigning a chiller to use a refrigerant with different thermodynamic characteristics This is due to the different efficiency capacity and operating pressure characteristics of each of the refrigerants Take a
10. 012 EN period one Components compressor Helical Rotors discharge port meshing point Continued rotation of the rotors causes the meshing point to travel toward the discharge end of the compressor driving the trapped refrigerant vapor ahead of it This action progressively reduces the volume of the pockets compressing the refrigerant compressor Helical Rotors meshing point Finally when the pockets of refrigerant reach the discharge port the compressed vapor is released As the rotors continue to rotate the volume of the pockets is further reduced squeezing the remaining refrigerant from the cavities Notice that the refrigerant vapor enters and exits the compressor through ports no valves are used Compressors of this design are called ported compressors TRG TRC012 EN TRANE period one Components Oil Separator refrigerant vapor to condenser refrigerant vapor and oil mixture y oil return to sump Oil Separator The oil leaves the compressor entrained within the discharged refrigerant vapor The oil is recovered from the discharged refrigerant by an oil separator which can have an efficiency of greater than 99 The separator consists of a vertical cylinder surrounding an exit passageway As the refrigerant and oil mixture is discharged into this passageway the oil is forced outward by centrifugal force collects on the walls of the cylinder and drains
11. G TRC012 EN BUSINESS REPLY MAIL FIRST CLASS MAIL PERMIT NO 11 LA CROSSE WI POSTAGE WILL BE PAID BY ADDRESSEE THE TRANE COMPANY Attn Applications Engineering 3600 Pammel Creek Road La Crosse WI 54601 9985 BUSINESS REPLY MAIL FIRST CLASS MAIL PERMIT NO 11 LA CROSSE WI POSTAGE WILL BE PAID BY ADDRESSEE THE TRANE COMPANY Attn Applications Engineering 3600 Pammel Creek Road La Crosse WI 54601 9985 NO POSTAGE NECESSARY IF MAILED IN THE UNITED STATES NO POSTAGE NECESSARY IF MAILED IN THE UNITED STATES Comment Card We want to ensure that our educational materials meet your ever changing resource development needs Please take a moment to comment on the effectiveness of this Air Conditioning Clinic Helical Rotary Water Chillers Level of detail circle one One of the Equipment Series TRG TRC012 EN About me Give the completed card to the presenter or drop it in the mail Thank you Response Card Too basic Just right Too difficult Rate this clinic from 1 Needs Improvement to 10 Excellent Content Booklet usefulness Slides illustrations Presenter s ability Training environment Other comments 1 2 2 2 2 2 S 3 3 3 3 4 5 6 7 8 9 10 4 5 6 7 8 9 10 4 5 6 7 8 9 10 4 5 6 7 8 9 10 4 5 6 7 8 9 10 Type of business Job function Optional name phone address TRANE The Trane Company Worldwide Applie
12. NE period three Compressor Capacity Control Slide Valve Operation high pressure refrigerant vapor to low pressure compressor slide valve housing operator shaft spring piston cylinder The slide valve is operated by a piston and cylinder assembly Extension and retraction of the operator shaft positions the slide valve along the compressor rotors High pressure refrigerant vapor controlled by 2 solenoid valves is fed to or bled from this assembly in order to position the valve To close the slide valve and load the compressor the load valve is opened and the unload valve is closed This allows high pressure refrigerant vapor to enter the cylinder from the discharge of the compressor extending the operator shaft and moving the slide valve so that it covers more of the rotor length Conversely to open the slide valve and unload the compressor the load valve is closed and the unload valve is opened This allows the high pressure refrigerant vapor to bleed out of the cylinder into the low pressure area within the compressor housing A spring helps return the piston retracting the operator shaft and moving the slide valve such that the rotors are more uncovered This reduces the effective length of the rotors which are compressing vapor On shutdown the unload solenoid valve is energized and the spring drives the slide valve to the fully unloaded position This ensures that the compressor a
13. able evaporator water flow Short evaporator water loops Equipment certification standards This section is by no means the entire list of considerations but is representative of some of the key issues condenser types Air Cooled or Water Cooled Air Cooled or Water Cooled Condensing Although this is not a new consideration the question of which condenser type to apply continues to receive attention A major advantage of air cooled chillers TRG TRC012 EN 31 Trane 32 period five Application Considerations is the elimination of the cooling tower This eliminates the concerns and maintenance requirements associated with water treatment makeup water availability and quality tower mechanical maintenance freeze protection and chiller condenser tube cleaning This reduced maintenance requirement is particularly attractive since it can substantially reduce operating costs Another advantage of an air cooled chiller is its delivery as a packaged system Reduced design time simplified installation higher reliability and single source responsibility are all factors that make the factory packaging of the condenser compressor and evaporator a major benefit A water cooled chiller has the additional requirement of condenser water piping pump cooling tower and controls Air cooled chillers are often selected in buildings with a requirement for year round cooling that cannot be met with an air side economizer Ai
14. ant to evaporator from expansion device Liquid Vapor Separator The mixture of liquid and vapor refrigerant that leaves the expansion device enters a liquid vapor separator Here the liquid refrigerant settles to the bottom of the chamber and the vapor is drawn off the top and routed directly to the suction side of the compressor The remaining liquid refrigerant is then routed to the evaporator TRG TRC012 EN TRG TRC012 EN TRANE period one Components By removing the vapor portion of the mixture before it gets to the evaporator the separator enhances the effectiveness of the evaporation process Flooded Evaporator refrigerant vapor lt ia chilled water supply a liquid i refrigerant 4 A E tube bundle chilled water return g IE N liquid level sensor Evaporator In the flooded shell and tube evaporator cool low pressure liquid refrigerant enters the distribution system inside the shell and is distributed uniformly over the tubes absorbing heat from relatively warm water that flows through the tubes This transfer of heat boils the film of liquid refrigerant on the tube surfaces and the resulting vapor is drawn back to the compressor The cooled water can now be used in a variety of comfort or process applications A sensor can monitor the level of liquid refrigerant in this type of evaporator and the electronic expansion valve can be used to carefully meter the liquid refr
15. ater Chillers period one Components Many of the components of the helical rotary water chiller are similar to those of other chiller types components of a Helical Rotary Water Chiller oil supply motor system N oil separator 4 EN liquid vapor F separator control panel starter evaporator This particular helical rotary water chiller makes use of a shell and tube evaporator where refrigerant evaporates inside the shell and water flows inside tubes The compressor is a twin rotor helical rotary compressor It uses a suction gas cooled motor to operate the compressor Another shell and tube heat exchanger is used for the condenser where refrigerant is condensed inside the shell and water flows inside tubes Refrigerant is metered through the system using an electronic expansion valve A liquid vapor separator can be used to enhance the effectiveness of the refrigeration cycle An oil supply system provides near oil free refrigerant to the shells to maximize heat transfer performance while providing lubrication and rotor sealing to the helical rotary compressor A control panel is also provided on the chiller and a starter connects the chiller motor to the electrical distribution system TRANE period one Components compressor Helical Rotors Compressor The helical rotary chiller uses 2 screw like rotors to perform the compression process compressor Helical Rotors female rotor p
16. closer look at each of these issues by examining the effects of using different refrigerants in the same helical rotary chiller designed for use with HCFC 22 E Efficiency In order to meet today s high standards of energy efficiency chillers using refrigerants with a lower thermal efficiency such as HFC 404a and HFC 410a will require larger heat exchangers and more efficient compressors These changes add to the product cost and increase the physical size of the chiller E Capacity HFC 134a has a lower capacity compared to HCFC 22 which means more refrigerant needs to be pumped through the chiller to achieve the same capacity This can be accomplished by using a larger compressor or increasing the speed of the compressor Both tend to increase product cost and design complexity On the other hand HFC 410a has a higher capacity compared to HCFC 22 which means less refrigerant needs to be pumped through the chiller to achieve the same capacity The advantage is that smaller less expensive compressors can be used E Operating Pressure A refrigerant that operates at a higher pressure requires heat exchangers and pressure vessels to be designed for the higher pressure This adds cost Conversely higher pressure refrigerants have a greater density As density increases the required amount of refrigerant decreases meaning that smaller or slower speed compressors can be used Lower pressure refrigerants such as HFC 134a will require
17. d Systems Group 3600 Pammel Creek Road La Crosse WI 54601 7599 www trane com An American Standard Company We offer a variety of HVAC related educational materials and technical references as well as software tools that simplify system design analysis and equipment selection To receive information about any of these items just complete this postage paid card and drop it in the mail Education materials Air Conditioning Clinic series Software tools Equipment selection Periodicals Engineers Newsletter Other Engineered Systems Clinic series rane Air Conditioning Manual rane Systems Manual System design amp analysis Name Title Business type About me Phone fax E mail address Company Address Thank you for your interest TRANE The Trane Company Worldwide Applied Systems Group 3600 Pammel Creek Road La Crosse WI 54601 7599 www trane com An American Standard Company T RANE Literature Order Number TRG TRC012 EN File Number E AV FND TRG TRC012 899 EN The Trane Company 15 Worldwide Applied Systems Group Supersedes aa 3600 Pammel Creek Road Stocking Location Inland La Crosse La Crosse WI 54601 7599 www trane com An American Standard Company Since The Trane Company has a policy of continuous product improvement it reserves the right to change design and specifications without notic
18. e
19. e condensing temperature control scheme depends on the specific application The water flow rate through the chiller s condenser must stay between the minimum and maximum condenser bundle flow rates as specified by the chiller manufacturer 34 TRG TRCO12 EN TRG TRCO12 EN TRANE period five Application Considerations evaporator water flow Constant or Variable Flow chilled water pump evaporator mn variable speed drive Constant or Variable Evaporator Water Flow In previous designs chillers were required to maintain a constant flow rate of water through the evaporator This requirement has changed due to advances in chiller controls Increased sensing and control capabilities now allow chiller manufacturers to design controls that monitor and respond faster to fluctuating conditions While the chiller may be able to handle variable water flow through the evaporator the specific application of a chilled water system may not warrant variable flow As always each application should be analyzed to determine if variable evaporator water flow is warranted variable evaporator water flow Limitations A Maintain minimum and maximum water flow rates through the chiller evaporator A Rate at which evaporator water flow changes must be kept below the corresponding limit to Maintain the chilled water set point control Keep the chiller on line Protect the chiller from damage The controls on many
20. ed in the liquid vapor separator to which point in the refrigeration cycle does it travel TRG TRC012 EN TRG TRC012 EN S TRANE Quiz Questions for Period 3 7 At full load is the slide valve fully closed or fully open 8 Explain how the slide valve varies the refrigerant flow rate through the helical rotary compressor Questions for Period 4 9 What document recommends the data points to be logged daily for each chiller 10 List 3 advantages to performing a regular oil analysis on a helical rotary water chiller Questions for Period 5 11 List 3 common methods of controlling condensing pressure in a water cooled chiller 12 What are the 2 primary limitations with varying the flow rate of water through the chiller evaporator 45 S TRANE Answers 9 Male and female screw rotors Bearing lubrication and cooling and rotor oil injection Outside of the tubes Electronic expansion valve and orifice plate a compression b condensation desuperheat condense subcool c expansion d evaporation Point 1 the suction inlet of the compressor Fully closed At part load the opening created by the slide valve movement allows refrigerant vapor to bypass from the rotor pockets back to the suction side of the compressor This reduces the volume of vapor available for the compression process It also reduces the amount of rotor length available for compression ASHRAE Guideline 3 10 Helps reduce main
21. eeeeeeteeeeeeeesaes 11 Liquid Vapor Separator ccceeceeeeeeeesseeeeeeeeeeeeeeeeees 12 Evaporator carri erent aiee Riis e 13 Controls and Starter cccccceeecesseeseeeeeeeeeeeeseeeeeeenees 15 period two Refrigeration Cycle 16 period three Compressor Capacity Control 21 period four Maintenance Considerations 25 period five Application Considerations 31 Air Cooled or Water Cooled Condensing 31 Condensing Temperature Control 33 Constant or Variable Evaporator Water Flow 35 Short Evaporator Water LOOPS ccccccceeeeeeeeeeeeee 36 Equipment Certification Standards 38 period six Review 40 QuiZ ini uieteniee neo 44 Answers ne rm nest 46 OSS nana nn 47 TRG TRCO12 EN iii S TRANE TRG TRC012 EN TRG TRC012 EN Introduction Chilled Water System Water chillers are used in a variety of air conditioning and process cooling applications They are used to make cold water that can be transported throughout a facility using pumps and pipes This cold water can be passed through the tubes of coils in order to cool the air in an air conditioning application or it can provide cooling for a manufacturing or industrial process Systems that employ water chillers are commonl
22. es every 3 years Clean condenser coils as needed air cooled Optimum performance of heat transfer components depends on keeping the heat transfer surfaces free from scale and sludge Even a very thin deposit of scale can substantially reduce heat transfer capacity Owners of water cooled chillers should engage the services of a qualified water treatment specialist to TRG TRCO12 EN TRG TRC012 EN TRANE period four Maintenance Considerations determine the level of water treatment required to remove contaminants from the cooling tower water Scale deposits are best removed by chemical means The water cooled condenser is commonly isolated from the rest of the cooling tower water circuit by valves and a pump circulates cleaning solution through the condenser tubes Sludge is removed mechanically This involves removing the water boxes from the condenser and loosening the deposits with a stiff bristled brush The loosened material is then flushed from the tubes with clear water As part of this procedure the strainers on both the chilled water and cooling tower water circuits should be cleaned every year Every 3 years or more frequently for process or critical applications it is recommended that a qualified service organization perform non destructive tube inspections on both the evaporator and condenser tubes The eddy current tube test is a common method Rarely problems may arise that cause refrigerant or water
23. f Halogenated Refrigerants in Refrigeration and Air Conditioning Equipment and Systems that includes a recommended list of data points to be logged daily for each water chiller compressor The mechanical device used by the chiller to increase the pressure and temperature of the refrigerant vapor condenser The region of the chiller where refrigerant vapor is converted to liquid as it rejects heat to water or air control panel The microprocessor based panel that monitor the chiller s operation protects it from damage provides the operator with data and diagnostic messages and permits interfacing with a building automation system direct expansion DX shell and tube evaporator A type of evaporator where refrigerant flows through the tubes and water fills the surrounding shell electronic expansion valve A type of expansion device that uses an electronically actuated valve to sense and control the flow rate of liquid refrigerant to the evaporator enthalpy The property of a refrigerant indicating its total heat content both sensible and latent evaporator The region of the chiller where the system chilled water is continuously cooled by flashing the refrigerant to vapor as it picks up heat from the returning chilled water expansion device The component of the chiller used to reduce the pressure and temperature of the refrigerant flooded shell and tube evaporator A type of evaporator where water flows through the tubes and
24. g slide valve was explained The slide valve is one method by which a helical rotary compressor s capacity is controlled TRG TRC012 EN 41 TRANE 42 period six Review Review Period 4 A Maintenance considerations Operating log Mechanical components Heat transfer surfaces Fluid analysis In Period 4 the general maintenance requirements of a helical rotary water chiller were discussed including Recommended data to be logged daily Required and recommended maintenance of the mechanical components Required and recommended maintenance of the heat transfer surfaces Recommended analysis of the oil and refrigerant Review Period 5 A Application considerations Air cooled or water cooled Condensing temperature control Constant or variable evaporator water flow Short evaporator water loops Equipment certification standards In Period 5 several considerations in the application of helical rotary water chillers were presented These included air cooled or water cooled condensing condensing temperature control constant or variable evaporator water flow short evaporator water loops and equipment certification standards TRG TRC012 EN period six Review S FRAME An American Standard Company For more information refer to the following references E Trane product catalogs for helical rotary water chiller products Trane literature order numbers RLC DS 1 RLC DS 2 RLC DS 4 and RLC DS 6
25. gerant temperature and pressures A Evaporator approach temperature A Condenser water inlet and A outlet temperatures and re pressures A Condenser water flow A Condenser refrigerant temperature and pressures A Condenser approach temperature Compressor refrigerant suction and discharge temperatures A Refrigerant level A Oil pressures temperature and levels A Addition of refrigerant Addition of oil Vibration levels The American Society of Heating Refrigerating and Air Conditioning Engineers ASHRAE has published Guideline 3 titled Reducing Emission of Halogenated Refrigerants in Refrigeration and Air Conditioning Equipment and Systems This guideline includes a recommended list of data points to be logged daily for each chiller Much of this data may be available through the chiller s control panel Special attention should be given to the following H Review the operating log and trends E Measure the oil pressure drop to determine if the oil filter needs to be replaced E Measure refrigerant superheat and subcooling E Measure both the refrigerant and oil charges TRG TRC012 EN TRANE period four Maintenance Considerations maintenance considerations Mechanical Components A Required maintenance Compressor and motor no maintenance required Controls no maintenance or calibration required A Recommended maintenance Visually inspect overall unit Inspect safety contro
26. he evaporator not change any faster than the chiller controls can respond The volume of water in the evaporator loop acts as a buffer and ensures a slowly changing return water temperature and therefore stable temperature control If there is not a sufficient volume of water in the loop to provide an adequate buffer temperature control can be lost resulting in erratic system operation The chiller manufacturer should be consulted for volume requirements of the evaporator water loop TRG TRC012 EN TRG TRC012 EN TRANE period five Application Considerations Short Evaporator Water Loops tank chilled water um Short water loops may be unavoidable in close coupled or very small applications particularly in systems where the load consists of only a few air handlers or processes To prevent the effect of a short water loop a storage tank or large header pipe can be added to the system to increase the volume of water in the loop and act as a buffer to ensure a slowly changing return water temperature 37 Trane 38 period five Application Considerations equipment certification standards ARI Standard 550 590 A Purpose Establish definitions and testing and rating requirements a Scope Factory designed and prefabricated water chillers Vapor compression refrigeration Air cooled and water cooled condensing STANDARD for WATER CHILLING PACKAGES USING THE
27. ical rotary water chiller Refrigeration Cycle liquid vapor Separator expansion device oil separator condenser But first lets review the components of the helical rotary chiller s refrigeration cycle Refrigerant vapor leaves the evaporator and flows to the compressor where it is compressed to a higher pressure and temperature Oil is removed from refrigerant vapor in the oil separator and the refrigerant travels to the condenser while the oil is recirculated back to the compressor In the condenser the refrigerant vapor rejects heat to water or air and leaves as a sub cooled liquid The pressure drop created by the expansion device causes a portion of the liquid refrigerant to evaporate and the resulting mixture of liquid and vapor refrigerant enters the liquid vapor separator Here the vapor is 16 TRG TRCO12 EN TRANE period two Refrigeration Cycle separated from the mixture and routed directly to the suction side of the compressor and the remaining liquid refrigerant enters the evaporator In the evaporator the liquid refrigerant boils as it absorbs heat from water The resulting vapor is drawn back to the compressor to repeat the cycle Pressure Enthalpy p h Chart subcooled liquid f mixture of liquid and vapor 147 5 psia A 1 A A ETN RE B superheated 1 02 MPa 7 vapor i v 46 4 Btu lb 116 6 Btu lb 256 4 kj kg 419 6 kj kg enthalpy The pressure e
28. ide valve is closed The compressor pumps its maximum volume of refrigerant discharging it through both the radial and axial ports slide valve position Part Load compressor discharge Slide valve to suction open i axial port radial port valve opening At part load the slide valve modulates toward the open position The opening created by the valve movement allows refrigerant vapor to bypass from the rotor pockets back to the suction side of the compressor This reduces the volume of vapor available for the compression process It also reduces the amount of rotor length available for compression In this manner the volume of refrigerant that is pumped by the compressor is varied unloading it to balance the existing chiller load 22 TRG TRC012 EN TRG TRC012 EN TRANE period three Compressor Capacity Control compressor capacity control Unloading compressor discharge slide valve to suction c open radial port valve opening As the slide valve continues to open further unloading the compressor its radial discharge port eventually travels past the opening in the compressor housing Once this occurs all of the refrigerant vapor being pumped by the compressor is discharged through the axial port in the compressor s end plate The compressor discharge ports and slide valve are designed to allow the compressor to operate efficiently over a wide range of conditions 23 S TRA
29. igerant flow to the evaporator s distribution system in order to maintain a relatively low level of refrigerant in the evaporator shell 13 S TRANE 14 period one Components Direct Expansion Evaporator chilled water T supply chilled water y refrigerant vapor liquid refrigerant tube bundle Another type of evaporator found in helical rotary chillers is the direct expansion DX shell and tube evaporator In this type of evaporator the cool low pressure liquid refrigerant flows through the tubes and water fills the surrounding shell As heat is transferred from the water to the refrigerant the refrigerant boils inside the tubes and the resulting vapor is drawn to the compressor Baffles within the shell direct the water in a rising and falling flow path over the tubes that carry the refrigerant The resulting turbulence improves heat transfer Since the tubes of a flooded evaporator contain water they can be mechanically cleaned without removing the refrigerant charge The tubes of a direct expansion evaporator must be chemically cleaned Additionally flooded evaporators are typically more effective but are more costly TRG TRC012 EN TRG TRC012 EN period one Components Controls And Starter Controls and Starter A microprocessor based control panel is provided on the chiller to provide accurate chilled water control as well as monitoring protection and adaptive limit functions These contr
30. igeration circuit is opened recovery of the refrigerant is required Finally the vent piping of all pressure relief valves should be leak tested annually for the presence of refrigerant to detect improperly sealed valves Leaking relief valves should be replaced TRG TRCO12 EN 27 mane 28 period four Maintenance Considerations maintenance considerations Mechanical Components a Other design specific requirements Change oil when oil analysis dictates Replace oil filter periodically Replace filter drier periodically Clean oil strainers annually Check shaft alignment annually Check coupling annually Replace shaft seal every 2 to 4 years Compressor teardown inspection every 5 to 10 years Some helical rotary compressor designs do require periodic maintenance of mechanical system components This includes oil and refrigerant filter changes oil strainer changes and a compressor rotor inspection Open motor compressor designs require shaft alignment coupling inspection bearing lubrication and cleaning of the motor windings rotor ends and fan blades on a quarterly or annual basis In all cases strictly follow the manufacturer s published maintenance requirements and recommendations maintenance considerations Heat Transfer Surfaces a Recommended maintenance Use a qualified water treatment specialist Clean condenser tubes as needed water cooled Clean water side strainers Test tub
31. larger or higher speed compressors in order to achieve the same capacity as a similar chiller using HCFC 22 TRG TRC012 EN TRG TRC012 EN TRANE period three Compressor Capacity Control Helical Rotary Water Chillers period three Compressor Capacity Control The capacity of the helical rotary compressor presented in this clinic is controlled by a slide valve that is an integral part of the compressor housing Other helical rotary compressor designs may use a variety of methods to vary capacity Some of these methods are similar in function to the slide valve presented in this period One major difference is whether the compressor is designed to unload in steps like a reciprocating compressor or if it has variable unloading Slide Valve axial discharge por radial discharge port slide valve The position of the slide valve along the rotors controls the volume of refrigerant vapor being delivered by the compressor by varying the amount of rotor length actually being used for compression Note that the compressor discharge has 2 components First a port within the slide valve provides a radial discharge path Second a port within the end plate of the compressor housing provides an axial discharge path 21 S TRANE period three Compressor Capacity Control slide valve position Full Load compressor discharge slide valve 1 axial port closed radial port At full load the sl
32. leaks These must be repaired immediately For air cooled chillers the condenser coils should be cleaned at least annually in order to maintain proper efficiencies and operating conditions Follow the manufacturer s instructions to avoid damage to the coils maintenance considerations Fluid Analysis a Oil analysis Conduct annual analysis to verify system integrity Measure oil pressure drop to determine if filter needs changing Measure charge A Refrigerant charge Measure charge and trim as necessary Measure superheat and subcooling Probably the most important annual maintenance task required for helical rotary water chillers is an oil analysis It may be conducted more frequently for chillers that run continuously or more often than normal This test performed by a qualified laboratory verifies the integrity of the refrigeration system by testing the moisture acidity and metal concentration levels This analysis can determine where problems exist or could potentially develop By taking oil samples on a regular basis normal operating trends for the compressor and bearing metals can be analyzed As opposed to changing the oil once a year whether it needs it or not regular oil analyses can be used to determine proper oil change intervals as well as predict major problems before they occur 29 mane 30 period four Maintenance Considerations Refrigerant analysis measures contamination levels and deter
33. ls and electrical components Tighten electrical connections Check for leaks Test vent piping Direct drive semi hermetic compressor designs require no periodic maintenance on the compressor motor assembly The compressor contains only 3 main moving parts the male and female rotors and the slide valve The semi hermetic motor eliminates the need for external shaft seals associated with open motors These seals are a prime source of oil and refrigerant leaks It also eliminates annual coupling and seal inspections alignment and shaft seal replacement With the advent of microprocessor based controls the control panel and auxiliary controllers require no recalibration or maintenance Remote mounted electronic sensors send information to the unit controller which can be connected to a building automation system in order to communicate information and allow for system level optimization These systems can notify the operator with an alarm or diagnostic message when a problem occurs Like any mechanical equipment a daily visual inspection of the chiller is recommended to look for oil leaks condensation loosened electrical or control wiring or signs of corrosion Special attention should be given to the safety controls and electrical components It is recommended that a qualified service technician check the chiller annually for leaks In the normal service of any air conditioning system the Unites States EPA mandates that whenever a refr
34. lways starts fully unloaded When both solenoid valves are closed the operator shaft holds the slide valve at its current position 24 TRG TRCO12 EN TRG TRC012 EN TRANE period four Maintenance Considerations Helical Rotary Water Chillers period four Maintenance Considerations This period discusses general maintenance requirements of helical rotary water chillers Although some of the information applies specifically to the design presented in this clinic requirements for other helical rotary chiller designs are also included helical rotary water chillers Maintenance Considerations a Operating log a Mechanical components a Heat transfer surfaces a Fluid analysis Once a helical rotary chiller is installed and put into operation it usually continues to function without a full time attendant In many cases the machine starts and stops on a schedule controlled by the building automation system or a simple time clock The only daily maintenance requirement is to check the operating log Water chillers are designed for maximum reliability with a minimum amount of maintenance Like all large mechanical systems however certain routine maintenance procedures are either required or recommended 25 Trane 26 period four Maintenance Considerations operating log ASHRAE Guideline 3 A Chilled water inlet and outlet A temperatures and pressures A Chilled water flow a Evaporator refri
35. mines suitability for continued use It can also determine the acceptability of recycled refrigerant for reuse Refrigerant analysis helps extend the life of the existing charge and ensures that the chiller is operating at peak efficiency Logging the oil and refrigerant charges and examining the trends of this data can help identify potential problems before they occur maintenance considerations Fluid Analysis a Why perform regular oil analyses Helps reduce maintenance costs Detects problems without compressor disassembly Extends service life of oil charge Reduces environmental problems related to oil disposal Helps maintain compressor efficiency and reliability Helps lower refrigerant emissions M An oil analysis is a key preventive maintenance measure and should be conducted at least annually It will help the compressor last longer while improving chiller efficiency and reducing refrigerant emissions A certified chemical laboratory has years of experience in analyzing oil and refrigerant from all types of compressors Often the chiller manufacturer can provide this service TRG TRC012 EN TRANE period five Application Considerations Helical Rotary Water Chillers period five Application Considerations There are several considerations to address when applying helical rotary water chillers including Air cooled or water cooled condensing Condensing temperature control Constant or vari
36. n single chillers within single chiller systems Remember that the ARI rating is a standardized representation Many chillers do not run at standard rating conditions and few are applied in single chiller installations Performing a comprehensive energy analysis is the best method of comparing the system operating cost difference between 2 chillers 39 TRANE period six Review Helical Rotary Water Chillers period six Review Let s review the main concepts that were covered in this clinic on helical rotary water chillers Review Period 1 oil supply compressor Motor system i AA oil separator EE liquidivapor of separator condenser control panel starter evaporator In Period 1 the following components of a helical rotary water chiller were discussed compressor oil separator oil supply system condenser expansion device liquid vapor separator evaporator starter and controls 40 TRG TRC012 EN period six Review Review Period 2 liquid vapor separator lies Sa evaporator device D In Period 2 the refrigeration cycle of the helical rotary water chiller was examined on a pressure enthalpy chart Also the performance characteristics of the various refrigerants were compared expansion enthalpy Review Period 3 axial discharge port radial discharge port slide valve In Period 3 the operation of the modulatin
37. nthalpy chart is simply a plot of the saturated properties of a refrigerant It plots refrigerant pressure vertical axis versus enthalpy horizontal axis Enthalpy is a measurement of the heat content both sensible and latent per pound kg of refrigerant For example A represents the heat content of saturated liquid HFC 134a refrigerant at 147 5 psia 1 02 MPa and 104 F 40 C B represents the heat content of saturated vapor HFC 134a refrigerant at the same pressure and temperature The difference in heat content or enthalpy between A and B that is 70 2 Btu pound 163 2 kJ kg is the amount of heat required to transform 1 pound 1 kg of saturated liquid refrigerant to saturated refrigerant vapor at the same pressure and temperature If the heat content of the refrigerant at any pressure falls to the right of the curve the vapor is superheated Similarly if the heat content of the refrigerant falls to the left of the curve the liquid is subcooled Finally when the heat content of the refrigerant falls inside the curve the refrigerant exists as a liquid vapor mixture TRG TRC012 EN 17 TRANE period two Refrigeration Cycle helical rotary water chiller Refrigeration Cycle liquid vapor separator device DA M The theoretical vapor compression refrigeration cycle for a helical rotary water chiller can be plotted on a pressure enthalpy chart expansion keen evaporator enthalpy
38. ols monitor the chiller s operation and prevent the chiller from operating outside of its limits They can compensate for unusual operating conditions while keeping the chiller running by modulating system components rather than simply tripping off due to a safety setting Furthermore when problems do occur diagnostic messages aid in troubleshooting This control system not only provides accurate optimized control and protection for the chiller but permits interfacing with a building automation system for integrated system control In a chilled water system optimal control is a system wide issue not just a chiller issue Because compressor motors create such a large electrical load they cannot be started and stopped using a simple switch or plug A starter provides a linkage between the motor and the electrical distribution system Its primary function is to connect start and disconnect stop the chiller from the line The starter also includes a transformer that provides power to the chiller control panel and components to perform overload protection and current limiting functions Finally the application of a chiller starter also requires considering a means of disconnect and short circuit protection 15 TRANE period two Refrigeration Cycle Helical Rotary Water Chillers period two Refrigeration Cycle A pressure enthalpy p h chart illustrates the refrigeration cycle of the helical rotary water chiller hel
39. ons selected for specific applications ARI s part load efficiency rating system establishes a single blended estimate of stand alone chiller performance The Integrated Part Load Value IPLV calculator predicts chiller efficiency at the ARI standard rating conditions using weighted averages representing a broad range of geographic locations building types and operating hour scenarios both with and without an airside economizer While the weighted averages place greater emphasis on the part load operation of an average single chiller installation they will not by definition represent any particular installation Additionally ARI notes that more than 80 percent of all chillers are installed in multiple chiller plants Chillers in these plants exhibit different unloading characteristics than the IPLV weighted formula indicates Appendix D of the Standard explains this further The IPLV equation was derived to provide a representation of the average part load efficiency for a single chiller only However it is best to use a comprehensive analysis that reflects actual weather data building load characteristics operational hours economizer capabilities and energy drawn by auxiliaries such as pumps and cooling towers when calculating the chiller and system efficiency This becomes increasingly important with multiple chiller systems because individual chillers operating within multiple chiller systems are more heavily loaded tha
40. or top of the compressor rotors inside the housing Its main purpose is to seal the rotor to rotor and rotor to housing clearances This seal provides a barrier between the high and low pressure cavities of the compressor Additionally oil lubricates the male to female rotor drive arrangement water cooled Condenser refrigerant vapor cooling tower gt gt subcooler liquid gt refrigerant tube bundle y water Condenser The high pressure refrigerant vapor now stripped of oil droplets leaves the oil separator and continues on to the condenser In a water cooled condenser water is pumped through the tubes of this shell and tube heat exchanger while refrigerant vapor fills the shell space surrounding the tubes The condenser has a baffle plate that helps distribute the refrigerant evenly within the shell As heat is transferred from hot high pressure refrigerant vapor to the water refrigerant condenses on the tube surfaces The condensed liquid refrigerant then collects in the bottom of the shell where the lower tubes are now submerged resulting in further cooling or subcooling of the refrigerant This arrangement is called an integral subcooler TRANE 10 period one Components Cooling water flows first through the lower tubes of the condenser and then through the upper tubes This produces a nearly constant temperature difference between the downward moving refrigerant and the tube surface
41. r cooled condensers have the ability to operate in below freezing weather without the problems associated with operating the cooling tower in low ambient conditions Cooling towers may require special sequences of operation basin heaters or even an indoor sump for safe operation in freezing weather air cooled or water cooled Comparison air cooled water cooled A Lower maintenance A Greater energy efficiency a Packaged system A Longer equipment life A Better low ambient operation Water cooled chillers are generally more energy efficient The efficiency advantage of a water cooled chiller however is much less when the additional cooling tower and condenser pump energy costs are considered Additionally this efficiency advantage may lessen at part load conditions since the dry bulb temperature tends to drop faster than the wet bulb temperature and the air cooled chiller benefits from greater condenser relief Performing a comprehensive energy analysis is the best method of estimating the system operating cost difference between air cooled and water cooled systems Water cooled chillers typically last longer than air cooled chillers This difference is due to the fact that the air cooled chiller is installed outdoors whereas the water cooled chiller is installed indoors Also using water as the condensing fluid allows the water cooled chiller to operate at lower pressures TRG TRC012 EN TRANE period five Application Conside
42. rations and temperatures that the air cooled chiller Generally air cooled chillers last 15 to 20 years while water cooled chillers last 20 to 25 years To summarize the comparison of air cooled and water cooled helical rotary chillers air cooled chiller advantages include lower maintenance cost a pre packaged system for easier design and installation and better low ambient operation Water cooled chiller advantages include greater energy efficiency at least at design conditions and longer equipment life Condensing Temperature Control cooling tower condenser water condenser pump Condensing Temperature Control All chillers require a minimum pressure difference between the evaporator and condenser to ensure proper management of oil and refrigerant This minimum pressure difference depends on the chiller design and controls The most common method of maintaining this pressure difference at the various load conditions is to control the condensing temperature by varying the temperature or flow rate of water or air flowing through the condenser By controlling the condensing temperature most helical rotary water chillers can start and operate over a wide range of conditions Controlling condensing temperature 1 maintains chiller efficiency 2 maintains the required pressure differential between the evaporator and condenser for controlled flow through the refrigerant metering system and 3 prevents the pressure
43. refrigerant fills the surrounding shell liquid vapor separator The component of the chiller used to remove vapor from the refrigerant mixture after it passes through the expansion device This 47 S TRANE 48 Glossary vapor is directed back to the compressor while the liquid refrigerant travels on to the evaporator oil separator The component of the chiller used to remove oil from the refrigerant vapor after it is discharged from the compressor This oil is directed back to the compressor orifice plate A type of expansion device that uses a fixed plate with holes drilled in it to meter the flow rate of refrigerant to the evaporator ported compressors A type of compressor where the refrigerant vapor enters and exits through ports no valves are used pressure enthalpy diagram A graphical representation of the saturated properties of a refrigerant plotting refrigerant pressure versus enthalpy rotor The part of the helical rotary compressor used to trap and compress the refrigerant vapor The male and female rotors mesh together forming pockets of refrigerant to move through the compressor slide valve The part of the helical rotary compressor used to vary the flow rate of refrigerant vapor through it subcooler The lower portion of the condenser that further cools the saturated liquid refrigerant water cooled condenser A type of condenser that rejects the heat of the refrigerant to water flowing through it TR
44. s resulting in a uniform heat transfer rate within the tube bundle Subcooled liquid refrigerant leaves the condenser subcooler and flows through the liquid line to the expansion device air cooled Condenser propeller fan condenser coil outdoor air 444044 subcooler In a typical air cooled condenser propeller type fans are used to draw outdoor air over a fin tube heat transfer surface The hot high pressure refrigerant vapor flows through the tubes as heat is transferred to the cooler outdoor air The resulting reduction in the heat content of the refrigerant vapor causes it to condense into liquid Within the final few lengths of condenser tubing the condensed liquid refrigerant is subcooled Again subcooled liquid refrigerant leaves the condenser subcooler and flows through the liquid line to the expansion device The differences between water cooled and air cooled chiller applications will be discussed further in Period 5 TRG TRCO12 EN period one Components expansion device Electronic Expansion Valve Expansion Device An expansion device is used to maintain the pressure difference between the high pressure condenser and low pressure evaporator sides of the system as established by the compressor This pressure difference allows the evaporator temperature to be low enough to absorb heat from the water being cooled while also allowing the refrigerant to be at a high enough temperature
45. tenance costs detects problems without compressor disassembly oil charges last longer less environmental problems with disposing of used oil helps maintain the compressor s efficiency and reliability and helps lower refrigerant emissions 11 Cycling or varying the speed of the cooling tower fans using a cooling tower bypass pipe modulating a throttling valve using a chiller bypass pipe or employing a variable speed drive on the condenser water pump 12 The water flow rate through the chiller s evaporator must stay between the 46 minimum and maximum evaporator bundle flow rates as specified by the chiller manufacturer The rate which the evaporator water flow rate changes must be kept below a specified level TRG TRC012 EN TRG TRCO12 EN S TRANE Glossary air cooled condenser A type of condenser that rejects the heat of the refrigerant to air flowing through it ARI Air Conditioning amp Refrigeration Institute ARI Standard 550 590 A publication titled Standard for Water Chilling Packages Using the Vapor Compression Cycle used to promote consistent rating and testing methods for all types and sizes of water chillers It covers factory designed prefabricated water chillers both air cooled and water cooled using the vapor compression refrigeration cycle ASHRAE American Society of Heating Refrigerating and Air Conditioning Engineers ASHRAE Guideline 3 A publication titled Reducing Emission o
46. to the bottom This accumulated oil drains out of the cylinder and collects in the oil sump located near the bottom of the chiller The oil sump is heated to ensure proper lubrication and minimize refrigerant condensation in the sump Oil Supply System oil separator rotor bearings refrigerant Lol vapor to condenser M oil tank LS master sum A 5 solenoid Oil that collects in the oil sump is at condensing pressure during compressor TRG TRC012 EN TRG TRC012 EN TRANE period one Components operation and is therefore constantly moving to lower pressure areas of the chiller In this system oil flows in 2 distinct paths each performing a separate function 1 bearing lubrication and cooling and 2 rotor oil injection Oil leaves the sump and passes through an oil filter and master solenoid valve The master solenoid valve is used to isolate the sump from the low pressure side of the system when the compressor is shut down preventing oil migration The first path is for lubricating and cooling the compressor bearings Oil is routed to the bearings located in the rotor and bearing housing Each housing is vented to the suction side of the compressor so that oil leaving the bearings is routed through the rotors to the oil separator and then back to the oil sump The second path is for lubricating and sealing the compressor rotors Oil is injected along the bottom
47. y called chilled water systems helical rotary There are several types of water chillers that are differentiated by the refrigeration cycle they use or the type of compressor Absorption water chillers make use of the absorption refrigeration cycle and do not have a mechanical compressor involved in the refrigeration cycle Absorption water chillers are the subject of a separate clinic TRANE Introduction Water chillers using the vapor compression refrigeration cycle vary by the type of compressor used Reciprocating and scroll compressors are typically used in smaller chillers Helical rotary or screw compressors are typically used in medium sized chillers Centrifugal compressors are typically used in larger chillers As mentioned earlier this particular clinic discusses helical rotary water chillers Helical Rotary Water Chillers water cooled air cooled Helical rotary water chillers can be either air cooled or water cooled referring to the method of rejecting heat to the atmosphere Both air cooled and water cooled helical rotary chillers are generally available from 70 to 450 tons 200 to 1500 kW The primary focus in Period 1 is on the water cooled chiller although it includes some discussion of air cooled chiller components A comparison of air cooled versus water cooled chiller applications is included in Period 5 TRG TRC012 EN TRG TRC012 EN period one Components Helical Rotary W
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