Trane TRG-TRC010-EN - Manuals

Preface © 1999 American Standard Inc. All rights reserved TRG-TRC010-EN ii The Trane Company believes that it is incumbent on manufacturers to serve the industry by regularly disseminating information gathered through laboratory research, testing programs, and field experience. The Trane Air Conditi...

TRG-TRC010-EN iii Contents Introduction ........................................................... 1 period one Components .......................................................... 3 Compressor ............................................................ 4 Condenser ..................................

TRG-TRC010-EN 1 notes Introduction 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 to cool the air...

2 TRG-TRC010-EN notes Introduction Water chillers using the vapor-compression refrigeration cycle vary by the type of compressor used. Reciprocating and scroll compressors are typically used in small chillers. Helical-rotary (or screw) compressors are typically used in medium-sized chillers. Centrif...

TRG-TRC010-EN 3 notes period one Components Many of the components of the centrifugal water chiller are similar to those of other chiller types. This particular centrifugal water chiller makes use of a shell-and-tube evaporator where refrigerant absorbs heat from the water flowing through the tubes....

4 TRG-TRC010-EN notes period one Components Compressor The centrifugal compressor uses the principle of dynamic compression , which involves converting energy from one form to another, to increase the pressure and temperature of the refrigerant. It converts kinetic energy to static energy. The core ...

TRG-TRC010-EN 5 period one Components notes The rotation of the impeller causes the refrigerant vapor to accelerate within the impeller passages , increasing its velocity and kinetic energy. The accelerated refrigerant vapor leaves the impeller and enters the diffuser passages . These passages start...

6 TRG-TRC010-EN notes period one Components Again, in the passages of the rotating impeller, the refrigerant vapor accelerates, increasing its velocity and kinetic energy. As the area increases in the diffuser passages, the velocity, and therefore the kinetic energy, of the refrigerant decreases. Th...

TRG-TRC010-EN 7 period one Components notes the accelerated refrigerant vapor leaves the last impeller, it collects in the compressor volute and travels on to the condenser. Condenser The high-pressure refrigerant vapor is discharged from the compressor into a heat exchanger that acts as a condenser...

8 TRG-TRC010-EN notes period one Components Expansion Device An expansion device is used to maintain the pressure difference between the high-pressure (condenser) and low-pressure (evaporator) sides of the refrigeration system, as established by the compressor. This pressure difference allows the ev...

TRG-TRC010-EN 9 period one Components notes As the load decreases, less refrigerant moves through the chiller and the level of the liquid column drops. Now, as the liquid refrigerant passes through the orifice plates, it only undergoes a pressure drop equal to the lower head (H 2 ) before some of it...

TRG-TRC010-EN 11 period one Components notes Again, the final expansion device reduces the pressure and temperature of the refrigerant to evaporator conditions. Evaporator In the flooded shell-and-tube evaporator shown, the low-pressure mixture of liquid refrigerant and refrigerant vapor enters the ...

12 TRG-TRC010-EN notes period one Components Motor A motor is used to rotate the impeller(s). A direct-drive motor is connected directly to the impeller shaft and the impeller rotates at the same speed as the motor. A gear-drive motor transfers its energy to the impeller shaft using a set of gears. ...

TRG-TRC010-EN 13 period one Components notes chiller’s refrigeration system — and uses a coupling to connect the motor and compressor shafts. The heat generated by the hermetic motor is absorbed by liquid refrigerant that flows around, through, and over the motor. The heat must be rejected by the ch...

14 TRG-TRC010-EN notes period one Components performance is a system-wide issue, not just a matter of chiller design and control. A starter links the chiller motor and the electrical distribution system. Its primary function is to connect (start) and disconnect (stop) the chiller from line power — s...

TRG-TRC010-EN 15 notes A pressure–enthalpy ( p - h ) chart illustrates the refrigeration cycle of the centrifugal water chiller. First, let’s review the components of a 2-stage centrifugal chiller in the context of the refrigeration cycle. Refrigerant vapor leaves the evaporator and flows to the com...

16 TRG-TRC010-EN notes period two Refrigeration Cycle The pressure drop created by the second expansion device lowers the pressure and temperature of the refrigerant to evaporator conditions, causing a portion of the liquid refrigerant to evaporate. The resulting mixture of liquid and vapor enters t...

18 TRG-TRC010-EN notes period two Refrigeration Cycle The change in enthalpy from C to A that occurs during the refrigeration cycle is called the refrigeration effect . This is the amount of heat that each pound [kg] of liquid refrigerant will absorb when it evaporates. The benefit of the economizer...

TRG-TRC010-EN 19 period two Refrigeration Cycle notes Refrigerants When selecting which refrigerant to use in a centrifugal water chiller, the manufacturer considers efficiency, operating pressures, compatibility with materials, heat transfer properties, stability, toxicity, flammability, cost, avai...

TRG-TRC010-EN 23 period three Compressor Capacity Control notes In a multistage centrifugal compressor , the operating characteristics of each impeller are modulated by the impeller’s own set of inlet vanes. This example shows 2 impellers in series. These impellers share the task of compressing the ...

24 TRG-TRC010-EN notes period three Compressor Capacity Control refrigerant. Recall that kinetic energy is converted to static energy, or static pressure. The radial velocity (V r ) for a given compressor is directly proportional ( ∝ ) to the flow rate of refrigerant vapor through the compressor. Th...

TRG-TRC010-EN 25 period three Compressor Capacity Control notes Consider a given-diameter compressor impeller that rotates at a constant speed. As the load on the chiller decreases, the inlet vanes partially close and the flow rate of refrigerant through the compressor drops. Radial velocity (V r ) ...

26 TRG-TRC010-EN notes period three Compressor Capacity Control As the load and the corresponding refrigerant flow rate continue to fall, the radial velocity (force) drops, too. At some point, the radial force becomes smaller than the generated static pressure, letting the pressurized refrigerant va...

TRG-TRC010-EN 27 period three Compressor Capacity Control notes conditions that cause the compressor to surge. Any operating point that falls to the right of this line is satisfactory for stable operation. To balance the load on the chiller, the compressor must pump a certain quantity of refrigerant...

TRG-TRC010-EN 29 period three Compressor Capacity Control notes An adjustable-frequency drive (AFD) , or variable-speed drive, is another device used to vary the capacity of a centrifugal compressor. AFDs are widely used with fans and pumps, and with the advancement of microprocessor-based controls ...

30 TRG-TRC010-EN notes period four Maintenance Considerations This period discusses general maintenance requirements of centrifugal water chillers. Although some of the information applies specifically to the design presented in this clinic, requirements for other centrifugal chiller designs are als...

TRG-TRC010-EN 31 period four Maintenance Considerations notes Guideline 3, “ Reducing Emission of Halogenated Refrigerants in Refrigeration and Air Conditioning Equipment and Systems ,” is one of several advisory documents published by the American Society of Heating, Refrigerating and Air-Condition...

32 TRG-TRC010-EN notes period four Maintenance Considerations The compressor/motor assembly in direct-drive, hermetic compressor designs requires little periodic maintenance. The hermetic motor eliminates the need for external shaft seals associated with open motors. (These seals are a prime source ...

TRG-TRC010-EN 33 period four Maintenance Considerations notes Some centrifugal compressor designs do require periodic maintenance of mechanical system components. This includes oil and refrigerant filter changes, oil strainer changes, and a compressor inspection. Open-motor compressor designs requir...

34 TRG-TRC010-EN notes period four Maintenance Considerations Scale deposits are best removed by chemical means. During this process, the water-cooled condenser is commonly isolated from the rest of the cooling-tower-water circuit by valves, while a pump circulates cleaning solution through the cond...

TRG-TRC010-EN 35 period four Maintenance Considerations notes Regularly logging oil and refrigerant charges, and examining the trends of this data, can help identify potential problems before they occur. An oil analysis is a key preventive maintenance measure and should be conducted at least annuall...

36 TRG-TRC010-EN notes period five Application Considerations Several considerations must be addressed when applying centrifugal water chillers, including: ■ Condensing temperature control ■ Constant or variable evaporator-water flow ■ Short evaporator-water loops ■ Heat recovery ■ Free cooling ■ Eq...

TRG-TRC010-EN 37 period five Application Considerations notes Condensing Temperature Control To achieve stable compressor unloading over a wide range of conditions, a reduction in condensing pressure (condenser relief) must accompany a reduction in load. The starting point (A) is the full-load opera...

38 TRG-TRC010-EN notes period five Application Considerations 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 ...

TRG-TRC010-EN 39 period five Application Considerations notes Constant or Variable Evaporator Water Flow Previous chiller designs required that a constant flow rate of water be maintained through the evaporator. This requirement has changed due to advances in chiller controls. Increased sensing and ...

40 TRG-TRC010-EN notes period five Application Considerations 1) The water flow rate through the chiller evaporator must stay between the minimum and maximum flow rates for the evaporator bundle, as specified by the chiller manufacturer. These limits depend on the specific design variables of the ac...

42 TRG-TRC010-EN notes period five Application Considerations Heat Recovery Salvaging usable heat from the refrigeration cycle — heat that would normally be rejected to the atmosphere — can significantly reduce the operating costs of many buildings. Heat recovery is most commonly accomplished using ...

TRG-TRC010-EN 43 period five Application Considerations notes Three types of heat-recovery chillers are commonly available: The dual-condenser , or double-bundle , heat-recovery chiller contains a second, full-size condenser that serves a separate hot water loop. It is capable of more heat rejection...

44 TRG-TRC010-EN notes period five Application Considerations Free Cooling Many buildings require some form of year-round cooling to handle interior spaces or other loads. When the outdoor air temperature falls below the indoor dew point temperature, it is possible to use an air-side economizer to s...

TRG-TRC010-EN 45 period five Application Considerations notes This leads to the discussion of a free cooling principle called refrigerant migration . It involves adapting a water chiller so that it functions as a simple heat exchanger. When the available condenser water is cooler than the desired ch...

46 TRG-TRC010-EN notes period five Application Considerations Equipment Certification Standards The Air Conditioning & Refrigeration Institute (ARI) establishes rating standards for packaged HVAC equipment. ARI also certifies and labels equipment through programs that involve random testing of a...

48 TRG-TRC010-EN notes Let’s review the main concepts that were covered in this clinic on centrifugal water chillers. Period 1 introduced the following components of a centrifugal water chiller: compressor, condenser, expansion device, economizer, evaporator, motor, control panel, and starter. Centr...

TRG-TRC010-EN 49 period six Review notes Period 2 described the refrigeration cycle of 2-stage centrifugal water chillers with a pressure-enthalpy chart. The operation of the purge system for low-pressure chillers was also presented. Period 3 further explained the operation of the centrifugal compre...

50 TRG-TRC010-EN notes period six Review Period 4 described the general maintenance requirements of a centrifugal water chiller, including: ■ Recommended data for a daily log ■ Required and recommended maintenance for mechanical components ■ Recommended maintenance for heat transfer surfaces ■ Requi...

TRG-TRC010-EN 51 period six Review notes For more information, refer to the following references: ■ Trane product catalogs for centrifugal water chiller products(Trane literature order numbers CTV-DS-1 and CTV-DS-2) ■ Condensing Water Temperature Control (CTV-EB-84) ■ Multiple Chiller System Design ...

52 TRG-TRC010-EN Questions for Period 1 1) A centrifugal compressor converts ___________ energy to ____________ energy. 2) Does the refrigerant velocity increase in the impeller, diffuser passages, or volute of the compressor? 3) What is the benefit of using an economizer cycle with a multistage cen...

TRG-TRC010-EN 53 Quiz 8) What velocity component is directly proportional to the impeller’s rotational speed times its diameter? 9) What are the 2 most common devices used to vary the capacity of a centrifugal compressor? Questions for Period 4 10) Explain why proper water treatment is important. Qu...

54 TRG-TRC010-EN 1) kinetic energy to static energy 2) impeller 3) By flashing a portion of the refrigerant prior to entering the evaporator, the economizer reduces the compressor power required since the refrigerant vapor generated in the economizer only needs to be compressed by the higher-stage i...

TRG-TRC010-EN 55 adjustable-frequency drive (AFD) A device used to vary the capacity of a centrifugal compressor by varying the speed of the motor that rotates the impeller(s). air-side economizer A method of free cooling that involves using cooler outdoor air for cooling instead of recirculating wa...