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Air Conditioning Clinic Helical-Rotary W ater Chillers One of the Equipment Series TRG-TRC012-EN.
Helical-Rotary W ater Chillers One of the Equipment Series A publication of The T rane Company— W orldwide Applied Systems Group.
Preface © 1999 American Standard Inc. All rights reserved TRG-TRC012-EN ii The T rane 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.
TRG-TRC012-EN iii Contents Introduction ............................................................ 1 period one Components ........................................................... 3 Compressor .....................................................
iv TRG-TRC012-EN.
TRG-TRC012-EN 1 notes Introduction W ater 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.
2 TRG-TRC012-EN notes Introduction W ater 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.
TRG-TRC012-EN 3 notes period one Components Many of the components of the helical-rotary water chiller are similar to those of other chiller types. 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.
4 TRG-TRC012-EN notes period one Components Compressor The helical-rotary chiller uses 2 screw-like rotors to perform the compression process. The rotors are meshed and fit, with very close tolerances, within a housing. Only the male rotor is driven by the compressor motor .
TRG-TRC012-EN 5 period one Components notes In the operation of the helical-rotary compressor , refrigerant vapor enters the compressor housing through the intake port .
6 TRG-TRC012-EN notes period one Components 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.
TRG-TRC012-EN 7 period one Components notes 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.
8 TRG-TRC012-EN notes period one Components 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%.
TRG-TRC012-EN 9 period one Components notes 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.
10 TRG-TRC012-EN notes 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 surfaces, resulting in a uniform heat transfer rate within the tube bundle.
TRG-TRC012-EN 11 period one Components notes 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 .
12 TRG-TRC012-EN notes period one Components 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.
TRG-TRC012-EN 13 period one Components notes By removing the vapor portion of the mixture before it gets to the evaporator the separator enhances the effectiveness of the evaporation process.
14 TRG-TRC012-EN notes period one Components 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.
TRG-TRC012-EN 15 period one Components notes 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 controls monitor the chiller’ s operation and prevent the chiller from operating outside of its limits.
16 TRG-TRC012-EN notes A pressure-enthalpy (p- h ) chart illustrates the refrigeration cycle of the helical- rotary water chiller . But first, lets review the components of the helical-rotary chiller’ s refrigeration cycle.
TRG-TRC012-EN 17 period two Refrigeration Cycle notes 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 .
18 TRG-TRC012-EN notes period two Refrigeration Cycle The theoretical vapor -compression refrigeration cycle for a helical-rotary water chiller can be plotted on a pressure-enthalpy chart.
TRG-TRC012-EN 19 period two Refrigeration Cycle notes Manufacturers are continuously improving their designs of helical-rotary water chillers. New chillers need to be designed around the characteristics of the refrigerant. T oday there are 5 strong candidates for use with positive- displacement, helical-rotary chillers.
20 TRG-TRC012-EN notes period two Refrigeration Cycle T oday 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.
TRG-TRC012-EN 21 notes 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 .
22 TRG-TRC012-EN notes period three Compressor Capacity Control At full load, the slide valve is closed. The compressor pumps its maximum volume of refrigerant, discharging it through both the radial and axial ports. At part load, the slide valve modulates toward the open position.
TRG-TRC012-EN 23 period three Compressor Capacity Control notes As the slide valve continues to open, further unloading the compressor , its radial discharge port eventually travels past the opening in the compressor housing.
24 TRG-TRC012-EN notes period three Compressor Capacity Control 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.
TRG-TRC012-EN 25 notes 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.
26 TRG-TRC012-EN notes period four Maintenance Considerations 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 .
TRG-TRC012-EN 27 period four Maintenance Considerations notes 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.
28 TRG-TRC012-EN notes period four Maintenance Considerations 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.
TRG-TRC012-EN 29 period four Maintenance Considerations notes determine the level of water treatment required to remove contaminants from the cooling tower water .
30 TRG-TRC012-EN notes period four Maintenance Considerations Refrigerant analysis measures contamination levels and determines suitability for continued use.
TRG-TRC012-EN 31 notes period five Application Considerations There are several considerations to address when applying helical-rotary water chillers, including: ■ Air -cooled or water-cooled conden.
32 TRG-TRC012-EN notes 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.
TRG-TRC012-EN 33 period five Application Considerations notes 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.
34 TRG-TRC012-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 .
TRG-TRC012-EN 35 period five Application Considerations notes Constant or V ariable 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.
36 TRG-TRC012-EN notes 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 .
TRG-TRC012-EN 37 period five Application Considerations notes 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.
38 TRG-TRC012-EN notes period five Application Considerations Equipment Certification Standards The Air Conditioning & Refrigeration Institute (ARI) establishes rating standards for packaged HV AC equipment.
TRG-TRC012-EN 39 period five Application Considerations notes 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.
40 TRG-TRC012-EN notes Let’ s review the main concepts that were covered in this clinic on helical-rotary water chillers. In Period 1, the following components of a helical-rotary water chiller were.
TRG-TRC012-EN 41 period six Review notes 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. In Period 3, the operation of the modulating slide valve was explained.
42 TRG-TRC012-EN notes period six Review In Period 4, the general maintenance requirements of a helical-rotary water chiller were discussed, including: ■ Recommended data to be logged daily ■ Requ.
TRG-TRC012-EN 43 period six Review notes For more information, refer to the following references: ■ T rane product catalogs for helical-rotary water chiller products (T rane literature order numbers.
44 TRG-TRC012-EN Questions for Period 1 1 What components of the helical-rotary compressor are used to compress the refrigerant? 2 What are the 2 functions of the oil supply system presented in this c.
TRG-TRC012-EN 45 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 .
46 TRG-TRC012-EN 1 Male and female screw rotors 2 Bearing lubrication and cooling, and rotor oil injection 3 Outside of the tubes 4 Electronic expansion valve and orifice plate 5) a) compression b) co.
TRG-TRC012-EN 47 air -cooled condenser A type of condenser that rejects the heat of the refrigerant to air flowing through it. ARI Air Conditioning & Refrigeration Institute ARI Standard 550/590 A.
48 TRG-TRC012-EN 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 .
NO PO STAG E NEC ES SAR Y IF M AIL ED IN THE UNITED STA TES B USINESS RE PL Y M AIL FIRST -CLASS MAIL LA CROSSE, WI PERMIT NO. 1 1 POST AGE W ILL BE P AID BY ADDRESSEE THE TRANE COMP ANY Attn: Applica.
Comment Card We want to ensure that our educational materials mee t y our ever -changing resourc e d evelopmen t nee ds. Please take a mome nt to com ment on the effectiveness of this Air Conditioning Clinic. Give the completed card to the presen t e r or drop i t in the m ail.
The T rane Company Worldwide Applied Systems Group 3600 Pammel Creek Road La Crosse, WI 54601-7599 www . trane.com An American Standard Company Literature Order Number TRG-TRC012-EN File Number E/A V-.
Un punto importante, dopo l’acquisto del dispositivo (o anche prima di acquisto) è quello di leggere il manuale. Dobbiamo farlo per diversi motivi semplici:
Se non hai ancora comprato il Trane TRG-TRC012-EN è un buon momento per familiarizzare con i dati di base del prodotto. Prime consultare le pagine iniziali del manuale d’uso, che si trova al di sopra. Dovresti trovare lì i dati tecnici più importanti del Trane TRG-TRC012-EN - in questo modo è possibile verificare se l’apparecchio soddisfa le tue esigenze. Esplorando le pagine segenti del manuali d’uso Trane TRG-TRC012-EN imparerai tutte le caratteristiche del prodotto e le informazioni sul suo funzionamento. Le informazioni sul Trane TRG-TRC012-EN ti aiuteranno sicuramente a prendere una decisione relativa all’acquisto.
In una situazione in cui hai già il Trane TRG-TRC012-EN, ma non hai ancora letto il manuale d’uso, dovresti farlo per le ragioni sopra descritte. Saprai quindi se hai correttamente usato le funzioni disponibili, e se hai commesso errori che possono ridurre la durata di vita del Trane TRG-TRC012-EN.
Tuttavia, uno dei ruoli più importanti per l’utente svolti dal manuale d’uso è quello di aiutare a risolvere i problemi con il Trane TRG-TRC012-EN. Quasi sempre, ci troverai Troubleshooting, cioè i guasti più frequenti e malfunzionamenti del dispositivo Trane TRG-TRC012-EN insieme con le istruzioni su come risolverli. Anche se non si riesci a risolvere il problema, il manuale d’uso ti mostrerà il percorso di ulteriori procedimenti – il contatto con il centro servizio clienti o il servizio più vicino.
