Trane TRG-TRC011-EN manuale d’uso

Air Conditioning Clinic Absor ption W at er Chillers One of the Equipment Ser ies TRG-TR C0 1 1 -EN[...]

Absor ption W at er Chillers One of the Equipment Ser ies A publication of The T rane Compan y— W o rldwide Applied S ystems Group[...]

Pr ef ace © 20 0 0 American Standard Inc. All rights reserved TRG-TRC0 1 1 -EN ii The T rane Compan y believes that it is incumbent on manufacturer s to serve the industry by regularly disseminating information gathered through laboratory researc h, testing programs, and field experience. The T rane Air Conditioning Clinic series is one means of k[...]

TRG-TRC0 1 1 -EN iii Cont ents Introduction ........................................................... 1 period one Absorption Refrigeration Cycle ....................... 3 Absorption System Fluids ........................................ 6 Components of the Absorption Cycle ...................... 8 Equilibrium Chart ..............................[...]

iv TRG-TRC0 04-EN[...]

TRG-TRC0 1 1 -EN 1 notes Intr oduction W ater c hillers 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 in an air conditioning application, or it c[...]

2 TRG-TRC0 1 1 -EN notes Intr oduction W ater c hillers using the vapor -compression refrigeration cycle vary by the type of compressor used. The compressor works to draw in refrigerant vapor and increase its pressure and temperature to create the cooling effect. Reciprocating, scroll, helical-rotary (or screw), or centrifug al compressors are gene[...]

TRG-TRC0 1 1 -EN 3 notes period one Absor ption Refr iger ation Cy cle This period describes the components of the absorption refrigeration cycle. Comparing the absorption refrigeration cycle with the more familiar vapor - compression refrigeration cycle is often an easy w ay to introduce it. Lik e the vapor -compression refrigeration cycle, the ab[...]

4 TRG-TRC0 1 1 -EN notes period one Absor ption Refr iger ation Cy cle In the vapor -compression refrigeration cycle, refrigerant enters the evaporator in the form of a cool, low- pressure mixture of liquid and vapor ( $ ). Heat is transferred from the relatively warm air or w ater to the refrigerant, causing the liquid refrigerant to boil. The res[...]

TRG-TRC0 1 1 -EN 5 period one Absor ption Refr iger ation Cy cle notes There are two fundamental differences between the absorption refrigeration cycle and the vapor -compression refrigeration cycle. The first is that the compressor is replaced by an absorber , pump, and generator . The second is that, in addition to the refrigerant, the absorption[...]

6 TRG-TRC0 1 1 -EN notes period one Absor ption Refr iger ation Cy cle Absorption System Fluids Probably the greater of these dif ferences between the vapor -compression and absorption refrigeration cycles, however , is the types of fluids used. The vapor - compression refrigeration cycle generally uses a halocarbon (suc h as HCFC-123, HCFC-22, HFC[...]

TRG-TRC0 1 1 -EN 7 period one Absor ption Refr iger ation Cy cle notes Additionally , the absorption refrigerant cycle uses a second fluid called an absorbent solution. The absorbent solution is confined to the absorber and generator sections of the cycle, and is used to carry the refrigerant from the low-pressure side (evaporator) to the high-pres[...]

8 TRG-TRC0 1 1 -EN notes period one Absor ption Refr iger ation Cy cle These two fluids, the refrigerant and the absorbent, are mixed inside the c hiller in various concentrations. The term dilute solution refers to a mixture that has a relatively high refrigerant content and low absorbent content. A concentrated solution has a relatively low refri[...]

TRG-TRC0 1 1 -EN 9 period one Absor ption Refr iger ation Cy cle notes The operating conditions used in this section of the clinic are approximate, subject to variation with c hanging load and cooling-water temperature conditions. At a given pressure, the temperature at which a liquid will boil into a vapor is the same temperature at whic h the vap[...]

10 TRG-TRC0 1 1 -EN notes period one Absor ption Refr iger ation Cy cle Starting on the high-pressure side of the cycle, the purpose of the generator is to deliver the refrigerant vapor to the rest of the system. It accomplishes this by separating the water (refrigerant) from the lithium bromide-and-w ater solution. In the generator , a high-temper[...]

TRG-TRC0 1 1 -EN 11 period one Absor ption Refr iger ation Cy cle notes Inside the condenser , cooling water flows through tubes and the hot refrigerant vapor fills the surrounding space. As heat transfers from the refrigerant vapor to the water , refrigerant condenses on the tube surfaces. The condensed liquid refrigerant collects in the bottom of[...]

12 TRG-TRC0 1 1 -EN notes period one Absor ption Refr iger ation Cy cle As the high-pressure liquid refrigerant flows through the expansion device, it causes a pressure drop that reduces the refrigerant pressure to that of the evaporator . This pressure reduction causes a small portion of the liquid refrigerant to boil off , or “ flash, ” cooli[...]

TRG-TRC0 1 1 -EN 13 period one Absor ption Refr iger ation Cy cle notes Inside the absorber , the refrigerant vapor is absorbed by the lithium bromide solution. As the refrigerant vapor is absorbed, it condenses from a vapor to a liquid, releasing the heat it acquired in the evaporator . This heat, along with the heat generated during the process o[...]

14 TRG-TRC0 1 1 -EN notes period one Absor ption Refr iger ation Cy cle As the lithium bromide solution absorbs the refrigerant, it becomes diluted and has less ability to absorb water vapor . T o complete the cycle and sustain operation, the absorbent solution must be reconcentrated. Consequently , the generator pump continuously returns the dilut[...]

TRG-TRC0 1 1 -EN 15 period one Absor ption Refr iger ation Cy cle notes Equilibrium Chart The performance of the absorption refrigeration cycle can be analyzed using a special c hart called an Equilibrium Chart for Aqueous Lithium Bromide Sol u ti o ns . This c har t plots the vapor pressure (ver tical axis) versus the temperature (horizontal axis)[...]

16 TRG-TRC0 1 1 -EN notes period one Absor ption Refr iger ation Cy cle A diagram of a typical absorption refrigeration cycle can be superimposed on this equilibrium c hart to demonstrate the function of eac h component in the system. Realiz e that the equilibrium c hart can only be used for those por tions of the cycle where the lithium bromide so[...]

TRG-TRC0 1 1 -EN 17 period one Absor ption Refr iger ation Cy cle notes Starting at the absorber , the dilute lithium bromide solution leaves the absorber ( $ ) at 1 05 ° F [40.6 º C] and 59% concentration. This solution passes through the heat exc hanger , where it is preheated to 175 ° F [79.4 ° C] ( % ). (Notice that there is no c hange in c[...]

18 TRG-TRC0 1 1 -EN notes Lithium bromide-and-water absorption c hillers are classified by the firing method — that is, how the primary generator is heated and whether it has a single- or a multiple-effect generator . Indirect-fired c hillers are heated with steam or a hot liquid (suc h as water) that is typically supplied by an on-site boiler or[...]

TRG-TRC0 1 1 -EN 19 period t w o Absor ption Chiller T ypes notes Single-Ef fect Chiller The single-ef fect absorption w ater c hiller uses a cycle similar to the one presented in Pe riod One. It includes a single generator , condenser , evaporator , absorber , heat exc hanger , and pumps. These c hiller s are typically operated on low-pressure ste[...]

20 TRG-TRC0 1 1 -EN notes period t w o Absor ption Chiller T ypes Let us review P eriod One briefly . In the generator , dilute solution absorbs heat from the steam or hot water , causing the refrigerant to boil and separate from the absorbent solution. As the refrigerant boils away , the absorbent solution becomes concentrated and returns to the a[...]

TRG-TRC0 1 1 -EN 21 period t w o Absor ption Chiller T ypes notes Double-Ef fect Chiller The double-effect absorption c hiller includes the same basic components as the single-effect c hiller; however , it also includes an additional generator , heat exc hanger , and pump. The high-temperature generator can use steam or hot water (indirect-fired) a[...]

22 TRG-TRC0 1 1 -EN notes period t w o Absor ption Chiller T ypes In the high-temperature generator , very high temperature steam or hot water flows through tubes that are immersed in an absorbent solution that is at an intermediate concentration. The solution absorbs heat from the warmer steam or water , causing the refrigerant to boil and separat[...]

TRG-TRC0 1 1 -EN 23 period t w o Absor ption Chiller T ypes notes Next, the refrigerant travels through the condenser , expansion device, evaporator and absorber in a manner similar to refrigerant travel in the single- effect absorption c hiller . The low - temperature generator pump returns the dilute absorbent solution to the low-temperature gene[...]

24 TRG-TRC0 1 1 -EN notes period t w o Absor ption Chiller T ypes to the absorber reduces the flow rate of cooling water required through the absorber . The c hiller shown in Figure 27 is steam-fired and includes an additional heat exc hanger . This condensate heat ex c h anger transfers heat from the hot condensed steam, leaving the high-temperatu[...]

TRG-TRC0 1 1 -EN 25 period t w o Absor ption Chiller T ypes notes In the series flow cycle, the dilute solution from the absorber is pumped entirely to the high-temperature generator . As the refrigerant boils away and migrates to the low-temperature generator , the absorbent solution becomes concentrated. The resulting intermediate solution then f[...]

26 TRG-TRC0 1 1 -EN notes period t w o Absor ption Chiller T ypes In the parallel flow cycle, the dilute solution from the absorber is split between the low-temperature and high-temperature generators. Both streams of dilute solution are concentrated in the generators and mix together again before returning to the absorber . The parallel flow cycle[...]

TRG-TRC0 1 1 -EN 27 period t w o Absor ption Chiller T ypes notes Direct-Fired Chiller The indirect-fired absorption c hiller s discussed previously use steam or a hot liquid (suc h as water) as the energy source. In contrast, the high-temperature generator of a direct-fired absorption c hiller uses the heat released by the combustion of a fossil f[...]

28 TRG-TRC0 1 1-EN notes period t w o Absor ption Chiller T ypes separate from the absorbent solution. As the refrigerant boils away , the solution becomes concentrated and returns to the absorber . The hot refrigerant vapor produced in the high-temperature generator migrates to the low -temperature generator where it flows through the tubes that a[...]

TRG-TRC0 1 1-EN 29 period t w o Absor ption Chiller T ypes notes The high-temperature generator pump draws a portion of the intermediate solution from the low-temperature generator and delivers it to the high- temperature generator to be reconcentrated. This cooler intermediate solution passes through the high-temperature heat exc h a ng e r to be [...]

30 TRG-TRC0 1 1-EN notes period t w o Absor ption Chiller T ypes Chiller/Heater One of the benefits of a direct-fired absorption c hiller is that it can be used to provide both cooling and heating. These c hillers, therefore, can be installed in systems to supplement, or even replace, primary heating or domestic hot water equipment. This can free u[...]

TRG-TRC0 1 1-EN 31 period t w o Absor ption Chiller T ypes notes Eac h of these operating modes serves a different load requirement. n In cooling only mode, the absorption c hiller operates exactly like the standard c hiller offering. Its function is to make cold water . n In heating only mode, the only function of the c h iller is to make hot wate[...]

32 TRG-TRC0 1 1-EN notes period t w o Absor ption Chiller T ypes An alternate method is to use the evaporator as a condenser in the heating mode. In this example c hiller , by switc hing the cooling/heating c hangeover valve the c hiller switc hes to heating mode, and hot water can be delivered using the same piping system that was used to supply c[...]

TRG-TRC0 1 1-EN 33 period t w o Absor ption Chiller T ypes notes While they are presently not available, higher -effect absorption c hillers are being studied for commercial use due their potential for higher COPs. T ypical COPs for these triple-effect cycles are 1 .4 to 1 .5. Implementation of these cycles into commercial water c hillers, however [...]

34 TRG-TRC0 1 1-EN notes period three Capacity Contr ol The primary objective of the chiller capacity control system is to reliably maintain the temperature of the c hilled water leaving the evaporator . The control system monitors the temperature of the leaving c hilled water , compares it to the setpoint, and adjusts the amount of solution suppli[...]

TRG-TRC0 1 1-EN 35 period three Capacity Contr ol notes other words, the combination of solution temperature and concentration determines the temperature at whic h the refrigerant will boil (vaporize). V arying the temperature at whic h the refrigerant boils in the evaporator c hanges the capacity of the absorption water c hiller . So, in order to [...]

36 TRG-TRC0 1 1-EN notes period three Capacity Contr ol In more modern absorption c hiller designs, adjustable-frequenc y driv es (AFD) , also known as variable-speed drives, are used to vary the speed of the generator pump motor , thus reducing the flow of solution to the generator . AFDs have the added benefit of saving pump energy at par t-load [...]

TRG-TRC0 1 1-EN 37 period three Capacity Contr ol notes out of the condition called crystallization — a solidification of the bromide salt. Crystallization will be discussed next. In the past, absorption water c hiller s would vary the heat input to the generator as the primary means of maintaining the desired leaving-c hilled-water temperature. [...]

38 TRG-TRC0 1 1-EN notes period three Capacity Contr ol By plotting the single-ef fect absorption refrigeration cycle on the equilibrium c hart, it is apparent that crystallization is most likely to occur in the heat exc hanger . At this par ticular condition, the 65% concentrated solution ( ' ) is cooled to 135 ° F [57 .2 ° C] ( ( ) as it p[...]

TRG-TRC0 1 1-EN 39 period three Capacity Contr ol notes As discussed, the point at whic h crystallization occur s is determined by the temperature and concentration of the concentrated solution inside the heat exc hanger . There are generally three possible causes of crystallization in an absorption water c hiller: n Air and other noncondensables l[...]

40 TRG-TRC0 1 1-EN notes period three Capacity Contr ol its way into the c hiller through any available path. As explained earlier , the pressure and temperature inside the evaporator are determined by the concentration and temperature of the solution in the absorber . If air leaks into the c hiller , however , the evaporator pressure increases bec[...]

TRG-TRC0 1 1-EN 41 period three Capacity Contr ol notes operate over a wide cooling-w ater temperature range, allowing the cooling- water temperature to vary with the load and ambient conditions without the risk of crystallization. For optimum control of leaving-c hilled-water temperature, however , it is still generally recommended to design the s[...]

42 TRG-TRC0 1 1-EN notes period three Capacity Contr ol As a second line of defense, most absorption water c hillers include devices that allow the c hiller to recover in the event that crystallization does occur . Some of these devices simply sense impending crystallization, put the c hiller through a dilution cycle, and shut the c hiller down. Ot[...]

TRG-TRC0 1 1-EN 43 period three Capacity Contr ol notes Special consideration must be given to controlling the chiller at very low load conditions combined with low cooling water temperatures. Under these conditions, the c hiller reac hes equilibrium with a very low solution concentration in the absorber . There is a possibility that the c hiller m[...]

44 TRG-TRC0 1 1-EN notes period three Capacity Contr ol Pur g e Sys t e m As presented earlier , the accumulation of air and other noncondensable gases undermines the efficiency and reliability of the absorption c hiller . Since absorption c hiller s operate below atmospheric pressure, regular operation of a purge system is required to remove, or ?[...]

TRG-TRC0 1 1-EN 45 period three Capacity Contr ol notes This example purge system consists of a purge tank, a small refrigeration system, a pump-out system, and controls. The purge ’ s refrigeration system includes: a small compressor , an air -cooled condensing coil, an expansion valve, and an evaporator coil located inside of the purge tank. Wh[...]

46 TRG-TRC0 1 1-EN notes period f our Maint enance Considerations T oday , af ter an absorption c hiller is installed and put into operation, it functions without a full-time attendant. In most cases, the c hiller starts and stops on a sc hedule controlled by a building automation system or a simple time cloc k. W ater c hillers are designed for ma[...]

TRG-TRC0 1 1-EN 47 period f our Maint enance Considerations notes condenser inlet and outlet temperatures; and purge operation. Logs are a valuable tool for determining the onset of system problems. This data may be obtained either manually or in conjunction with a building automation system. The c hiller controller should be capable of providing t[...]

48 TRG-TRC0 1 1-EN notes period f our Maint enance Considerations Most purges are fully automatic and generally require less maintenance than previous-generation manually operated purges. Purge-related maintenance procedures are simple. n Weekl y: With the purge unit operating, c hec k the purge tank condensing activity by observing the liquid refr[...]

TRG-TRC0 1 1-EN 49 period f our Maint enance Considerations notes The burner is the heart of a direct-fired absorption c hiller . Cor rect operation is, therefore, necessary for optimum c hiller performance. Daily c hec ks should be made in accordance with the manufacturer ’ s recommendations. Eac h cooling season, the burner ’ s firing rate, b[...]

50 TRG-TRC0 1 1-EN notes period f our Maint enance Considerations The use of better heat-transfer materials will reduce future maintenance costs. The high-temperature generator , for example, contains high-temperature lithium bromide solution that, when exposed to air and other noncondensables, is more corrosive than in other sections of the c hill[...]

TRG-TRC0 1 1-EN 51 period f our Maint enance Considerations notes An absorption c hiller requires a very deep vacuum to operate efficiently . The introduction of air and other noncondensables into the c hiller will adver sely affect the c hiller ’ s performance. In a lithium bromide absorption c hiller , where the absorbent is a salt, corrosion i[...]

52 TRG-TRC0 1 1-EN notes period f our Maint enance Considerations If air leaks into the c hiller , the cor rosion inhibitor is depleted as it reacts with the air and produces hydrogen. T o maintain c hiller efficiency and ensure continued corrosion protection, the lithium bromide solution must be analyz ed periodically to determine if corrosion inh[...]

TRG-TRC0 1 1-EN 53 notes period fiv e Application Consider ations Several considerations must be addressed when applying absorption w a ter c hiller s, including: n Cooling-water temperature limitations n Combination c hiller plants n Special considerations for direct-fired c hiller s n Equipment rating standards While not all-inclusive, this list [...]

54 TRG-TRC0 1 1-EN notes period fiv e Application Consider ations Cooling-Water T emperature Limitations The temperature of the cooling water significantly impacts the operation of an absorption c hiller . As the temperature of the entering-cooling-w ater decreases, c hiller capacity increases. Some absorption c hiller designs can experience operat[...]

TRG-TRC0 1 1-EN 55 period fiv e Application Consider ations notes Combination Chiller Plants Absorption c hiller s possess two operating c haracteristics that can noticeably improve o verall system ef ficiency and reduce system energy costs. First, absorption c hillers use fossil fuels rather than electricity . Operating absorption c hiller s at ti[...]

56 TRG-TRC0 1 1-EN notes period fiv e Application Consider ations The second beneficial operating c haracteristic is that an absorption c hiller works more efficiently and produces more cooling with increased leaving- c hilled-water temperatures. Applications with two c hiller s can be either piped in series or in parallel. Though there are advanta[...]

TRG-TRC0 1 1-EN 57 period fiv e Application Consider ations notes Special Considerations for Direct-Fired Chillers The combustion process that occurs in the burner is k ey to the operation of a direct-fired absorption c hiller . It also introduces several additional considerations when applying this type of c hiller . n Combustion air requirements:[...]

58 TRG-TRC0 1 1-EN notes period fiv e Application Consider ations In general, ASHRAE Standard 1 5-1 994, “ Safety Code for Mec hanical Refrigeration, ” does not apply to absorption w ater c hiller s due to Section 2.3, whic h states: This code does not apply where water is the primary refrigerant. Section 8.1 3.6 of the Standard, however , does[...]

TRG-TRC0 1 1-EN 59 period fiv e Application Consider ations notes a refrigerant vapor detector to monitor refrigerant levels in the mac hinery room. When the detector measures refrigerant levels above those allow able, a building automation system is used to automatically shut down the combustion process. Due to the lower cost, many building owners[...]

60 TRG-TRC0 1 1-EN notes W e will now review the main concepts that were covered in this clinic on absorption water c hillers. P eriod One presented the basic single-ef fect, absorption refrigeration cycle. In the generator , dilute solution absorbs heat from the steam or hot water flowing through the tubes, causing the refrigerant to boil and sepa[...]

TRG-TRC0 1 1-EN 61 period six Review notes and vapor refrigerant then flows into the ev aporator pan, from whic h the ev aporator spra y pump continuously pumps the liquid refrigerant to be sprayed o ver the tubes. As heat transfers from the c hilled wa ter flowing through the tubes to the cooler refrigerant, the refrigerant boils (vaporizes) and t[...]

62 TRG-TRC0 1 1-EN notes period six Review Pe riod Three explained the part-load operation of the absorption c hiller . It described the use of energy valves, burner controls, throt tling and bypass valves, and adjustable-frequency drives as methods for controlling the capacity on the c hiller . V alves and AFDs are used to vary the flow rate of so[...]

TRG-TRC0 1 1-EN 63 period six Review notes P eriod Four described general maintenance requirements for absorption w ater c hiller s, including: n Recommended data for a daily log n Recommended maintenance for mec hanical components, suc h as the solution and refrigerant pumps, purge, and burner n Recommended maintenance for heat-transfer surfaces n[...]

64 TRG-TRC0 1 1-EN notes period six Review For more information, refer to the following references: n T rane product catalogs for absorption water c hiller products (T rane literature order numbers ABS-DS-1, ABS-DS-4, ABS-DS-6, and ABS-PRC0 0 1-EN) n Absorption Chiller System Design Applications Engineering Manual (T rane literature order number SY[...]

TRG-TRC0 1 1-EN 65 Questions f or P eriod 1 1 What are the names of the two working fluids used within the absorption cycle? 2 Identify the components of the absorption refrigeration cycle labeled in Figure 75. 3 What are the two major components on the high-pressure side of the absorption refrigeration cycle? What are the two major components on t[...]

66 TRG-TRC0 1 1-EN Quiz Questions f or P eriod 3 9 Does an increase in solution concentration, assuming a constant solution temperature, result in an increase or decrease in vapor pressure? 10 What is crystallization? 11 What are the most common causes of crystallization in an absorption c hiller and how can these conditions be avoided? Questions f[...]

TRG-TRC0 1 1-EN 67[...]

68 TRG-TRC0 1 1-EN 1 Refrigerant (distilled w ater) and absorbent (lithium bromide) 2 $ generator , % condenser , & expansion device, ' evaporator , ( absorber , ) heat exc hanger 3 Generator and condenser; evaporator and absorber 4 Below atmospheric pressure 5 Condenser and evaporator 6 T o preheat the dilute solution returning to the gen[...]

TRG-TRC0 1 1-EN 69 absorbent A substance used to absorb refrigerant and transport it from the low-pressure to the high-pressure side of the absorption refrigeration cycle. In absorption water c hillers, the absorbent is commonly lithium bromide. absorber A component of the absorption refrigeration system where refrigerant vapor is absorbed by the a[...]

70 TRG-TRC0 1 1-EN Glossary condenser A component of the absorption refrigeration system in whic h refrigerant vapor is conver ted to liquid as it rejects heat to cooling water . cooling wat er W ater obtained from a source (cooling tower , river , pond) to whic h heat is rejected. This water flows through tubes in the absorber and the condenser . [...]

TRG-TRC0 1 1-EN 71 Glossary purg e A device used to remove air and other noncondensable gases that may leak into the low-pressure absorption c hiller . re f rig e ra n t A substance used to absorb and transport heat for the purpose of cooling. In a large absorption water c hiller, the refrigerant is distilled w ater . satur ation t emperat ur e The[...]

The T rane Company W orldwide Applied S ystems Group 3600 Pammel Creek Road La Crosse, WI 5460 1 -7599 www.trane.com An American Standard Company Literature Order Number TRG-TRC0 1 1 -EN File Number E/A V -FN D-TRG-TRC0 1 1-0400-EN Supersedes 2803-1 1-677 Stoc king Location La Crosse Since The T rane Company has a policy of continuous product impro[...]