ASHRAE HVAC APPLICATIONS IP CH 13-2015 SHIPS.pdf

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1、13.1CHAPTER 13SHIPSMerchant Ships 13.1Naval Surface Ships 13.3HIS chapter covers air conditioning for oceangoing surfaceTvessels, including naval ships, commercial vessels, fishingboats, luxury liners, pleasure craft, and inland and coastal boats, aswell as oil rigs. Although the general principles

2、of air conditioningfor land installations also apply to marine applications, factors suchas weight, size, fire protection, smoke control, and corrosion resis-tance take on greater importance, and new factors (e.g., tolerance forpitch and roll, shipboard vibration, watertightness) come into play.The

3、importance of shipboard air conditioning depends on a shipsmission. On passenger vessels that focus completely on passengercomfort, such as cruise ships and casino vessels, air conditioning isvital. Aboard commercial vessels (tankers, bulkers, container ships,etc.), air conditioning provides an envi

4、ronment in which personnelcan live and work without heat stress. Shipboard air conditioningalso improves reliability of electronic and other critical equipment,as well as weapons systems aboard naval ships.This chapter discusses merchant ships, which includes passengerand commercial vessels, and nav

5、al surface ships. In general, thedetails of merchant ship air conditioning also apply to warships.However, all ships are governed by their specific ship specifications,and warships are often also governed by military specifications,which ensure air-conditioning system and equipment performancein the

6、 extreme environment of warship duty.1. MERCHANT SHIPSLoad CalculationsThe cooling load estimate considers the following factors discussedin Chapter 18 of the 2013 ASHRAE HandbookFundamentals:Solar radiationHeat transmission through hull, decks, and bulkheadsHeat (latent and sensible) dissipation fr

7、om occupantsHeat gain from lightsHeat (latent and sensible) gain from ventilation airHeat gain from motors or other electrical equipmentHeat gain from piping, machinery, and equipmentThe heating load estimate should include the following:Heat losses through decks and bulkheadsVentilation airInfiltra

8、tion (when specified)In addition, the construction and transient nature of ships presentsome complications, as addressed in the following:SNAME. The Society of Naval Architects and Marine Engineers(SNAME 1980) Technical and Research Bulletin 4-16 can be used asa guide for shipboard load calculations

9、.ISO. The International Organization for Standardizations (ISO)Standard 7547 discusses design conditions and calculations formarine HVAC systems.Outdoor Ambient Temperature and Humidity. The serviceand type of vessel determine the proper outdoor design temperature,which should be based on temperatur

10、es prevalent in a ships area ofoperation. Use Chapter 14 of the 2013 ASHRAE HandbookFunda-mentals to select ambient conditions, with special attention paid tohigh-wet-bulb data; a ships load is often driven by the latent loadassociated with the outdoor air. It is also common for different loca-tions

11、 to be used for cooling and heating criteria. In general, for cool-ing, outdoor design conditions are 95F db and 78F wb; forsemitropical runs, 95F db and 80F wb; and for tropical runs, 95Fdb and 82F wb. For heating, 0F is usually the design temperature,unless the vessel will always operate in warmer

12、 climates. Designtemperatures for seawater are 90F in summer and 28F in winter.Solar Gain. Ships require special consideration for solar gainbecause (1) they do not constantly face in one direction and (2) thereflective properties of water increase solar load on outer boundariesnot directly exposed

13、to sunlight. For compartments with only oneexterior boundary, the temperature difference (outdoor dry-bulb tem-perature indoor dry-bulb temperature) across horizontal surfacesshould be increased by 50F and vertical surfaces by 30F. For com-partments with more than one exterior boundary, the temperat

14、ure dif-ference should be increased by 35F for horizontal surfaces and 20Ffor vertical surfaces. For glass surfaces, the solar cooling load (SCL)is taken to be 160 Btu/hft2for spaces with one exterior boundary and120 Btu/hft2for spaces with more than one exterior boundary.Infiltration. Infiltration

15、through weather doors is generally dis-regarded. However, specifications for merchant ships occasionallyrequire an assumed infiltration load for heating steering gear roomsand the pilothouse.Transmission Between Spaces. For heating loads, heat transmis-sion through boundaries of machinery spaces in

16、either direction is notconsidered. Allowances are not made for heat gain from warmer adja-cent spaces. For cooling loads, the cooling effect of adjacent spaces isnot considered unless temperatures are maintained with refrigerationor air-conditioning equipment.Ventilation Requirements. Ventilation mu

17、st meet the require-ments of ASHRAE Standard 62.1-2013, unless otherwise stated inthe ships specification.Heat Transmission Coefficients. The overall heat transmissioncoefficients U for the composite structures common to shipboardconstruction do not lend themselves to theoretical derivation; theyare

18、 usually obtained from full-scale panel tests. SNAME Bulletin4-7 gives a method to determine these coefficients when tested dataare unavailable. ISO Standard 7547 also gives some guidance in thisarea, as well as default values if better information is not available.Indoor Air Temperature and Humidit

19、y. Thermal environmen-tal conditions for human occupancy are given in ASHRAE Standard55-2010.People. Ships normally carry a fixed number of people. The engi-neer must select the location where the ships fixed complement ofpeople creates the greatest heat load, and then not apply the peopleload elsew

20、here. Note that occupants are only counted once whendetermining the chiller or condensing-unit load; however, air coils ineach zone must be capable of removing the heat load associated withthe maximum number of people in the zone.Ventilation in the zone can also be reduced when occupants arenot pres

21、ent. For the ventilation load, occupants are counted once, inthe location where they create the greatest ventilation requirement.The preparation of this chapter is assigned to TC 9.3, Transportation AirConditioning.13.2 2015 ASHRAE HandbookHVAC ApplicationsThe practical way to apply this concept is

22、by measuring CO2levelsin a space and adjusting outdoor air accordingly. Although usingthis principle can reduce required chiller or condensing-unit capac-ity on all ships, it is most significant aboard passenger ships.EquipmentIn general, equipment used for ships is much more rugged thanthat for lan

23、d use. Sections 6 through 10 of ASHRAE Standard 26list HVAC equipment requirements for marine applications. Whenselecting marine duty air-conditioning equipment, consider the fol-lowing:It should function properly under dynamic roll and pitch andstatic trim and heel conditions. This is especially im

24、portant forcompressor oil sumps, oil separators, refrigerant drainage from acondenser and receiver, accumulators, and condensate drainagefrom drain pans.Construction materials should withstand the corrosive effects ofsalt air and seawater. Materials such as stainless steel, nickel-copper, copper-nic

25、kel, bronze alloys, and hot-dipped galvanizedsteel are used extensively.It should be designed for uninterrupted operation during the voy-age and continuous year-round operation. Because ships en routecannot be easily serviced, some standby capacity, spare parts forall essential items, and extra oil

26、and refrigerant charge should becarried.It should have no objectionable noise or vibration, and must meetnoise criteria required by the ships specification.It should occupy minimum space, commensurate with its cost andreliability. Weight should also be minimized.A ship may pass through one or more c

27、omplete cycles of seasonson a single voyage and may experience a change from winter tosummer operation in a matter of hours. Systems should be flexi-ble enough to compensate for climatic changes with minimalattention from the ships crew.The following general items should be considered when select-in

28、g specific air conditioning components:Fans. Fans must be selected for stable performance over their fullrange of operation and should have adequate isolation to preventtransmitting vibration to the deck. Because fan rooms are often adja-cent to or near living quarters, effective sound treatment is

29、essential.Cooling Coils. If more than 30% outdoor air is brought across acooling coil, consider using copper tube, copper fin, epoxy-coatedcoils, or other special treatment. To account for the ships move-ment, drain pans should have two drain connections. Because of sizeconstraints, care must be tak

30、en to prevent moisture carryover. Facevelocity limits (in fpm) for different coil materials and different finspacing are as follows:Off-coil temperatures are another concern. Ships typically havelow ceiling heights and can not tolerate low air-introduction temper-atures. Typically 55F db and 54F wb

31、are used as limiting off-coiltemperatures.Electric Heaters. U.S. Coast Guard (USCG) approved sheathed-element heaters are typically required. The only exception is whenthe electric heaters, approved by a regulatory body such as UL, areincorporated in a packaged unit.Air Diffusers. Care must be taken

32、 with selection of air diffusersbecause of the low ceilings typical of shipboard applications.Air-Conditioning Compressors. Compressors of all types areused for marine applications. Care must be taken when using anonpositive-displacement compressor (such as centrifugal) becauselow-load, high-condens

33、ing temperature is a common off-loadcondition.When high discharge temperatures are a concern, seawater-cooled heads are not normally an option; other methods such as fancooling or liquid injection must be considered for maintainingacceptable discharge temperatures.Typical SystemsAll types of systems

34、 may be considered for each marine applica-tion. The systems are the same as in land applications; the differenceis the relative weighting of their advantages and disadvantages formarine use. This section does not review all the systems used aboardships, but rather some of the more common ones.Direc

35、t refrigerant cooling systems are often used for small,single-zone applications. Aboard ships, places like control roomsand pilot houses lend themselves to a direct refrigerant system. Forlarger spaces, air distribution is of more concern; direct refrigerantcooling is thus less likely to be the opti

36、mum solution.Two-pipe and four-pipe fan coil systems are often used forlarge systems. The water piping used in these systems takes up onlya fraction of the space used by an all-air ducted system. The disad-vantage is fan noise in the space being cooled. In addition, limitedhumidity control and fresh

37、-air requirements often need to beaddressed separately.Many types of all-air systems are used aboard ships. Space, cost,noise, and complexity are among the leading parameters whencomparing different all-air systems. Using high-velocity air distri-bution for an all-air system offers many advantages;

38、unitary (factory-assembled) central air-handling equipment and prefabricatedpiping, clamps, and fittings facilitate installation for both new con-struction and conversions. Substantial space-saving is possiblecompared to conventional low-velocity sheet metal ducts. Mainte-nance is also reduced. Nois

39、e is the one major drawback of a high-velocity system, which often leads to selection of a low-velocitysystem.Terminal reheat air conditioning (described in Chapter 4 of the2012 ASHRAE HandbookHVAC Systems and Equipment) is com-monly used because of its simplicity and good zone control charac-terist

40、ics. However, as systems become larger, this systems energyinefficiency becomes a significant drawback.Dual-duct systems (also described in Chapter 4 of the 2012ASHRAE HandbookHVAC Systems and Equipment) have the fol-lowing advantages:All conditioning equipment is centrally located, simplifyingmaint

41、enance and operationCan heat and cool adjacent spaces simultaneously without cyclechangeover and with minimum automatic controlsBecause only air is distributed from fan rooms, no water or steampiping, electrical equipment, or wiring are in conditioned spacesThe major drawback is the inability to fin

42、ely control temperatureand humidity. This disadvantage is enough to preclude using thesesystems in many passenger vessel applications.Aboard ships, constant-volume systems are most common.Their advantages include simplicity (for maintenance, operation,and repair) and low cost. However, for large pas

43、senger vessels, theenergy efficiency and the tight control of zone temperature makevariable-volume/temperature systems very attractive.Air Distribution MethodsGood air distribution in staterooms and public spaces is difficultto achieve because of low ceiling heights and compact spacearrangements. De

44、sign should consider room dimensions, ceilingheight, volume of air handled, air temperature difference betweensupply and room air, location of berths, and allowable noise. ForFins per Inch (fpi) Aluminum Fins Copper or Coated Fins8550 5011 550 42514 550 375Ships 13.3major installations, mock-up test

45、s are often used to establish exact-ing performance criteria.Air usually returns from individual small spaces either by a sight-tight louver mounted in the door or by an undercut in the door lead-ing to the passageway. An undercut door can only be used with airquantities of 75 cfm or less. Louvers a

46、re usually sized for face veloc-ity of 400 fpm based on free area.Ductwork on merchant ships is generally constructed of steel.Ducts, other than those requiring heavier construction because ofsusceptibility to damage or corrosion, are usually made with rivetedseams sealed with hot solder or fire-res

47、istant duct sealer, weldedseams, or hooked seams and laps. They are made of hot-dipped, gal-vanized, copper-bearing sheet steel, suitably stiffened externally.The minimum thickness of material is determined by the diameterof round ducts or by the largest dimension of rectangular ducts, aslisted in T

48、able 1.The increased use of high-velocity, high-pressure systems hasresulted in greater use of prefabricated round pipe and fittings,including spiral-formed sheet metal ducts. It is important that field-fabricated ducts and fittings be airtight. Using factory-fabricatedfittings, clamps, and joints e

49、ffectively minimizes air leakage forthese high-pressure ducts.In addition to the space advantage, small ductwork saves weight,another important consideration for this application.ControlThe conditioning load, even on a single voyage, varies over awide range in a short period. Not only must the refrigeration plantmeet these load variations, but the controls must readily adjust thesystem to sudden climatic changes. Accordingly, it is general prac-tice to equip the plant with automatic controls.Regulatory AgenciesMerchant vessels that operate under the U.S. flag