ASHRAE HVAC APPLICATIONS SI CH 6-2015 HOTELS MOTELS AND DORMITORIES.pdf

1、6.1CHAPTER 6HOTELS, MOTELS, AND DORMITORIESLoad Characteristics. 6.1Design Concepts and Criteria. 6.1Systems 6.1Hotels and Motels . 6.3Dormitories . 6.8Multiple-Use Complexes . 6.8OTELS, motels, and dormitories may be single-room orHmultiroom, long- or short-term dwelling (or residence) units;they m

2、ay be stacked sideways and/or vertically. Information in thefirst three sections of the chapter applies generally; the last three sec-tions are devoted to the individual types of facilities. High energycosts and consequent environmental damage require that these typeof facilities be energy efficient

3、 and sustainable. Occupants needassurance that they can afford the fuel bills and that their lifestyle isnot damaging to the planet. This chapter provides advice on sustain-able practices to achieve these aims.1. LOAD CHARACTERISTICS Ideally, each room served by an HVAC unit should be able to bevent

4、ilated, cooled, heated, or dehumidified independently of anyother room. If not, air conditioning for each room will be compro-mised, and personal comfort will not be possible.Typically, the space is not occupied at all times. For adequate flex-ibility, each units ventilation and cooling should be ab

5、le to be shutoff (except when humidity control is required), and its heating tobe shut off or turned down. This can be achieved by occupantdetection, use of door key fobs, or simple-to-use manual controlssuch as thermostatic radiator valves (TRVs) on radiators.Concentrations of lighting and occupanc

6、y are variable, rangingfrom low for those who work during the day to high and continu-ous for family homes and residential elderly accommodation;activity is generally sedentary or light.Kitchens have the potential for high appliance loads and odor andsteam generation, and have large exhaust requirem

7、ents, with con-trol from low to high, to boost air extraction to suit cooking.Rooms generally have an exterior exposure with good daylightlevels and a view to green features; however, kitchens, toilets, anddressing rooms are normally internal and require extract ventila-tion. The building as a whole

8、 usually has multiple exposures, asmay many individual dwelling units. Design must optimize pas-sive solar gains while avoiding overheating and glare.Toilet, washing, and bathing facilities are almost always incor-porated in the dwelling units, and the modern trend is to provideen-suite bathrooms in

9、 every bedroom. Exhaust air is usually incor-porated in each toilet and bathroom area.The building has a relatively high hot-water demand, generally forperiods of an hour or two, several times a day. This demand canvary from a fairly moderate and consistent daily load profile in asenior citizens bui

10、lding to sharp, unusually high peaks at about6:00 PM in dormitories. Chapter 50 includes details on servicewater heating.Load characteristics of rooms, dwelling units, and buildings canbe well defined with little need to anticipate future changes todesign loads, other than adding a service such as c

11、ooling that maynot have been incorporated originally.The prevalence of shifting, transient interior loads and exteriorexposures with glass results in high diversity factors; the longhours of use result in fairly high load factors.2. DESIGN CONCEPTS AND CRITERIAWide load swings and diversity within a

12、nd between roomsrequire a flexible system design for 24 h comfort. Besides openingwindows, the only way to provide flexible temperature control ishaving individual room components under individual room controlthat can cool, heat, and ventilate independently of equipment inother rooms.In some climate

13、s, summer humidity becomes objectionable be-cause of the low internal sensible loads that result when cooling ison/off controlled. Modulated cooling and/or reheat may be requiredto achieve comfort. Reheat should be avoided unless some sort ofheat recovery is involved.Dehumidification can be achieved

14、 by lowering cooling coil tem-peratures and reducing airflow or by using desiccant dehumidifiers.Some people have a noise threshold low enough that certain typesof equipment disturb their sleep. Higher noise levels may be accept-able in areas where there is little need for air conditioning. Medium-a

15、nd better-quality equipment is available with noise criteria (NC) 35levels at 3 to 4 m in medium to soft rooms and little sound changewhen the compressor cycles.Perimeter fan coils are usually quieter than unitary systems, butunitary systems provide more redundancy in case of failure.3. SYSTEMSEnerg

16、y-Efficient SystemsThere is increased impetus to select energy-efficient systems fordwellings to limit potential climate impact, conserve fossil fuelreserves, and avoid fuel poverty. In Europe, the Energy PerformanceDirective sets out a strategy for each European country to achievetargets toward thi

17、s objective; in the United Kingdom, for example,all new dwellings should be zero-carbon by 2016, which means asliding scale from the current allowable values to zero between 2011to 2016. Other countries have similar schemes. In North America,ASHRAE Standard 90.1 is setting progressive reductions als

18、o aimedzero net energy.Where natural gas is available, gas-fired condensing boilers areused, with modulating controls linked to load monitoring such as anoutdoor temperature detector.Heating and cooling applications generally include water-sourceand air-source heat pumps. In areas with ample solar r

19、adiation,water-source heat pumps may be solar assisted, and/or solar thermalcollectors can be used. Energy-efficient equipment generally has thelowest operating cost and should be kept simple, an important factorwhere skilled operating personnel are unlikely to be available. MostThe preparation of t

20、his chapter is assigned to TC 9.8, Large Building Air-Conditioning Applications.6.2 2015 ASHRAE HandbookHVAC Applications (SI)systems allow individual operation and thermostatic control. Thetypical system allows individual metering so that most, if not all, ofthe cooling and heating costs can be met

21、ered directly to the occu-pant (McClelland 1983). Existing buildings can be retrofitted withheat flow meters and timers on fan motors for individual metering,and there is a drive toward provision of better real-time energy useto allow occupants to make changes that reduce their costs at theright tim

22、e.The water-loop heat pump has a lower operating cost than air-cooled unitary equipment and allows a degree of heat recoverybecause the condenser water loop acts to balance energy use whenpossible. The lower installed cost encourages its use in mid- andhigh-rise buildings where individual dwelling u

23、nits have floor areasof 75 m2or larger. Some systems incorporate sprinkler piping as thewater loop.The system has a central plant consisting of circulating pumps,heat rejection when there is surplus heat capacity in the building,and supplementary gas-fired boiler heat input when there is an over-all

24、 deficit of heat. The water-loop heat pump is predominantlydecentralized; individual metering allows most of the operating costto be paid by the occupant. Its life should be longer than for otherunitary systems because most of the mechanical equipment is in thebuilding and not exposed to outdoor con

25、ditions. Also, load on therefrigeration circuit is not as severe because water temperature iscontrolled for optimum operation. Operating costs are low becauseof the systems inherent energy conservation. Excess heat may bestored during the day for the following night, and heat may be trans-ferred fro

26、m one part of the building to another.Although heating is required in many areas during cool weather,cooling could be needed in rooms having high solar loads. Thisshould be avoided by effective solar shading design. On a mild day,surplus heat throughout the building is frequently transferred intothe

27、 hot-water loop by water-cooled condensers on cooling cycle, sothat water temperature rises. The heat remains stored in the waterand can be extracted at night; a water heater is therefore avoided.This heat storage is improved by the presence of a greater mass ofwater in the pipe loop; some systems i

28、nclude a storage tank for thisreason, or water tank with phase-change material (PCM) thermalstorage. Because the system is designed to operate during the heat-ing season with water supplied at a temperature as low as 15C, thewater-loop heat pump lends itself to solar assist; relatively highsolar col

29、lector efficiencies result from the low water temperature.The installed cost of the water-loop heat pump is higher in verysmall buildings. In severe cold climates with prolonged heating sea-sons, even where natural gas or fossil fuels are available at reason-able cost, the operating cost advantages

30、of this system may diminishunless heat can be recovered from some another source, such assolar collectors, geothermal, or internal heat from a commercialarea served by the same system.Energy-Neutral SystemsTo qualify as energy-neutral, a system must have controls thatprevent simultaneous operation o

31、f the cooling and heating cycles.Some examples are (1) packaged terminal air conditioners (PTACs)(through-the-wall units), (2) window units or radiant ceiling panelsfor cooling combined with finned or baseboard radiation for heat-ing, (3) unitary air conditioners with an integrated heating system,(4

32、) fan coils with remote condensing units, and (5) variable-air-volume (VAV) systems with either perimeter radiant panel heatingor baseboard heating. For unitary equipment, control may be as sim-ple as a heat/cool switch. For other types, dead-band thermostaticcontrol may be required.PTACs are freque

33、ntly installed to serve one or two rooms inbuildings with mostly small, individual units. In a common two-room arrangement, a supply plenum diverts some of the conditionedair serving one room into the second, usually smaller, room.Multiple PTAC units allow additional zoning in dwellings withmore roo

34、ms. Additional radiation heat is sometimes needed aroundthe perimeter in cold climates.Heat for a PTAC may be supplied either by electric resistanceheaters or by hot-water or steam heating coils. Initial costs are lowerfor a decentralized system using electric resistance heat. Operatingcosts are low

35、er for coils heated by combustion fuels. Despite its rel-atively inefficient refrigeration circuits, a PTACs operating cost isquite reasonable, mostly because of individual thermostatic controlover each machine, which eliminates the use of reheat while pre-venting the space from being overheated or

36、overcooled. Also,because equipment is located in the space being served, little poweris devoted to circulating the room air. Servicing is simple: a defec-tive machine is replaced by a spare chassis and forwarded to a ser-vice organization for repair. Thus, building maintenance can bedone by relative

37、ly unskilled personnel.Noise levels are generally no higher than NC 40, but some unitsare noisier than others. Installations near a seacoast should be spe-cially constructed (usually with stainless steel or special coatings) toavoid accelerated corrosion of aluminum and steel componentscaused by sal

38、t. In high-rise buildings of more than 12 stories, specialcare is required, both in design and construction of outdoor parti-tions and in installation of air conditioners, to avoid operating prob-lems associated with leakage (caused by stack effect) around andthrough the machines.Frequently, the lea

39、st expensive installation is finned or baseboardradiation for heating and window-type room air conditioners forcooling. The window units are often purchased individually by thebuilding occupants. This choice offers a reasonable operating costand is relatively simple to maintain. However, window unit

40、s havethe shortest equipment life, highest operating noise level, and poor-est distribution of conditioned air of any systems discussed in thissection.Fan-coils with remote condensing units are used in smaller build-ings. Fan-coil units are located in closets, and the ductwork distrib-utes air to th

41、e rooms in the dwelling. Condensing units may belocated on roofs, at ground level, or on balconies.Low-capacity residential warm-air furnaces may be used for heat-ing, but with gas- or oil-fired units, combustion products must bevented. In a one- or two-story structure, it is possible to use individ

42、ualchimneys or flue pipes, but a high-rise structure requires a multiple-vent chimney or a manifold vent. Local codes should be consulted.Sealed combustion furnaces draw all combustion air from, anddischarge flue products through a windproof vent to, the outdoors.The unit must be located near an out

43、er wall, and exhaust gases mustbe directed away from windows and intakes. In one- or two-storystructures, outdoor units mounted on the roof or on a pad at groundlevel may also be used. All of these heating units can be obtainedwith cooling coils, either built-in or add-on. Evaporative-type cool-ing

44、units are popular in motels, low-rise apartments, and residencesin mild climates.Desiccant dehumidification should be considered when indepen-dent control of temperature and humidity is required to avoid reheat.Energy-Inefficient SystemsEnergy-inefficient systems allow simultaneous cooling and heat-

45、ing. Examples include two-, three-, and four-pipe fan coil units, ter-minal reheat systems, and induction systems. Some units, such asthe four-pipe fan coil, can be controlled so that they are energy-neutral by ensuring that the two circuits do not simultaneously servethe PTAC. They are primarily us

46、ed for humidity control.Four-pipe systems and two-pipe systems with electric heaters canbe designed for complete temperature and humidity flexibility duringsummer and intermediate season weather, although none provideswinter humidity control. Both systems provide full dehumidificationand cooling wit

47、h chilled water, reserving the other two pipes or anHotels, Motels, and Dormitories 6.3electric coil for space heating or reheat. The equipment and necessarycontrols are expensive, and only the four-pipe system, if equipped withan internal-source heat-recovery design for the warm coil energy, canope

48、rate at low cost. When year-round comfort is essential, four-pipesystems or two-pipe systems with electric heat should be considered.Total Energy SystemsA total energy system is an option for any multiple or large hous-ing facility with large year-round service water heating requirements.Total energ

49、y systems are a form of cogeneration in which all or mostelectrical and thermal energy needs are met by on-site systems asdescribed in Chapter 7 of the 2012 ASHRAE HandbookHVAC Sys-tems and Equipment. A detailed load profile must be analyzed todetermine the merits of using a total energy system. The reliabilityand safety of the heat-recovery system must also be considered.Any of the previously described systems can perform the HVACfunction of a total energy system. The major considerations as theyapply to total energy in choosing an HVAC system are as follows:Optimum use must be made o