ASHRAE REFRIGERATION SI CH 18-2010 ABSORPTION EQUIPMENT《吸附设备》.pdf
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1、18.1CHAPTER 18ABSORPTION EQUIPMENT Water/Lithium Bromide Absorption Technology 18.1Ammonia/Water Absorption Equipment . 18.7Special Applications and Emerging Products. 18.9Information Sources 18.10HIS chapter surveys and summarizes the types of absorptionTequipment that are currently manufactured an
2、d/or commonlyencountered. The equipment can be broadly categorized by whetherit uses water or ammonia as refrigerant. The primary products in thewater refrigerant category are large commercial chillers, which uselithium bromide (LiBr) as absorbent. There are three primary prod-ucts in the ammonia re
3、frigerant category: (1) domestic refrigerators,(2) residential chillers, and (3) large industrial refrigeration units.This chapter focuses on hardware (i.e., cycle implementation),not on cycle thermodynamics. Cycle thermodynamic descriptionsand calculation procedures, along with a tabulation of the
4、types ofabsorption working pairs and a glossary, are presented in Chapter 2of the 2009 ASHRAE HandbookFundamentals.Absorption units have two major advantages: (1) they are acti-vated by heat, and (2) no mechanical vapor compression isrequired. They also do not use atmosphere-harming halogenatedrefri
5、gerants, and reduce summer electric peak demand. No lubri-cants, which are known to degrade heat and mass transfer, arerequired. The various equipment can be direct-fired by combus-tion of fuel, directly heated by various waste fluids, or heated bysteam or hot water (from either direct combustion or
6、 from hotwaste fluids). Figure 1 illustrates the similarities between absorp-tion and vapor compression systems.With natural gas firing, absorption chilling units level the year-round demand for natural gas. From an energy conservationperspective, the combination of a prime mover plus a waste-heat-p
7、owered absorption unit provides unparalleled overall efficiency.WATER/LITHIUM BROMIDE ABSORPTION TECHNOLOGYComponents and TerminologyAbsorption equipment using water as the refrigerant and lith-ium bromide as the absorbent is classified by the method of heatinput to the primary generator (firing met
8、hod) and whether theabsorption cycle is single- or multiple-effect.Machines using steam or hot liquids as a heat source areindirect-fired, and those using direct combustion of fossil fuels asa heat source are direct-fired. Machines using hot waste gases asa heat source are also classified as indirec
9、t-fired, but are oftenreferred to as heat recovery chillers.Solution recuperative heat exchangers, also referred to aseconomizers, are typically shell-and-tube or plate heat exchangers.They transfer heat between hot and cold absorbent solution streams,thus recycling energy. The material of construct
10、ion is mild steel orstainless steel.Condensate subcooling heat exchangers, a variation of solu-tion heat exchangers, are used on steam-fired, double-effectmachines and on some single-effect, steam-fired machines. Theseheat recovery exchangers use the condensed steam to add heat tothe solution enteri
11、ng the generator.Indirect-fired generators are usually shell-and-tube, with theabsorbent solution either flooded or sprayed outside the tubes, and theheat source (steam or hot fluid) inside the tubes. The absorbent solu-tion boils outside the tubes, and the resulting intermediate- or strong-concentr
12、ation absorbent solution flows from the generator through anoutlet pipe. The refrigerant vapor evolved passes through a vapor/liq-uid separator consisting of baffles, eliminators, and low-velocityregions and then flows to the condenser section. Ferrous materials areused for absorbent containment; co
13、pper, copper-nickel alloys, stain-less steel, or titanium are used for the tube bundle.Direct-fired generators consist of a fire-tube section, a flue-tube section, and a vapor/liquid separation section. The fire tube istypically a double-walled vessel with an inner cavity large enoughto accommodate
14、a radiant or open-flame fuel oil or natural gasburner. Dilute solution flows in the annulus between the inner andouter vessel walls and is heated by contact with the inner vesselwall. The flue tube is typically a tube or plate heat exchanger con-nected directly to the fire tube.Heated solution from
15、the fire-tube section flows on one side ofthe heat exchanger, and flue gases flow on the other side. Hot fluegases further heat the absorbent solution and cause it to boil. Fluegases leave the generator, and the partially concentrated absorbentsolution and refrigerant vapor mixture pass to a vapor/l
16、iquid sepa-rator chamber. This chamber separates the absorbent solution fromthe refrigerant vapor. Materials of construction are mild steel forthe absorbent containment parts and mild steel or stainless steel forthe flue gas heat exchanger.Secondary or second-stage generators are used only in double
17、- ormultistage machines. They are both a generator on the low-pressureside and a condenser on the high-pressure side. They are usually of theshell-and-tube type and operate similarly to indirect-fired generatorsThe preparation of this chapter is assigned to TC 8.3, Absorption and Heat-Operated Machi
18、nes.Fig. 1 Similarities Between Absorption and Vapor Compres-sion SystemsFig. 1 Similarities Between Absorption and Vapor Compression Systems18.2 2010 ASHRAE HandbookRefrigeration (SI)of single-effect machines. The heat source, which is inside the tubes, ishigh-temperature refrigerant vapor from the
19、 primary generator shell.Materials of construction are mild steel for absorbent containment andusually copper-nickel alloys or stainless steel for the tubes. Dropleteliminators are typically stainless steel.Evaporators are heat exchangers, usually shell-and-tube, overwhich liquid refrigerant is drip
20、ped or sprayed and evaporated. Liq-uid to be cooled passes through the inside of the tubes. Evaporatortube bundles are usually copper or a copper-nickel alloy. Refrigerantcontainment parts are mild steel. Mist eliminators and drain pans aretypically stainless steel.Absorbers are tube bundles over wh
21、ich strong absorbent solu-tion is sprayed or dripped in the presence of refrigerant vapor. Therefrigerant vapor is absorbed into the absorbent solution, thusreleasing heat of dilution and heat of condensation. This heat isremoved by cooling water that flows through the tubes. Weak absor-bent solutio
22、n leaves the bottom of the absorber tube bundle. Mate-rials of construction are mild steel for the absorbent containmentparts and copper or copper-nickel alloys for the tube bundle.Condensers are tube bundles located in the refrigerant vaporspace near the generator of a single-effect machine or the
23、second-stage generator of a double-effect machine. The water-cooled tubebundle condenses refrigerant from the generator onto tube surfaces.Materials of construction are mild steel, stainless steel, or othercorrosion-resistant materials for the refrigerant containment partsand copper for the tube bun
24、dle. For special waters, the condensertubes can be copper-nickel, which derates the performance of theunit.High-stage condensers are found only in double-effectmachines. This type of condenser is typically the inside of the tubesof the second-stage generator. Refrigerant vapor from the first-stage g
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