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1、EGEE 102 Energy Conservation And Environmental ProtectionHome Heating Basics论文外文翻译 http:/ 论文外文翻译 http:/ EGEE 1022National Average Home Energy CostsEGEE 1023Why do we need Heating?70 FFurnace30 FEGEE 1024Typical Heat losses- Conventional House5% through ceilings16%throughwindows1% throughbasement flo

2、or17% throughframe walls3% through door38% through cracksin walls, windows,and doors20%throughbasementwallsEGEE 1025Heat Transfer Conduction Convection RadiationEGEE 1026ConductionEnergy is conducted down the rod as the vibrations of one molecule are passed to the next, but there is no movement of e

3、nergetic EGEE 1027ConvectionEnergy is carried by the bulk motion of the fluidEGEE 1028RadiationEnergy is carried by electromagnetic waves. No medium is requiredEGEE 1029Degree Days Index of fuel consumption indicating how many degrees the mean temperature fell below 65 degrees for the day Heating de

4、gree days (HDD) are used to estimate the amount of energy required for residential space heating during the cool season. Cooling degree days (CDD) are used to estimate the amount of air conditioning usage during the warm seasonEGEE 10210How do we calculate HDD? HDD = Tbase - Ta if Ta is less than Tb

5、ase HDD = 0 if Ta is greater or equal to Tbase Where: Tbase = temperature base, usually 65 F Ta = average temperature, Ta = (Tmax + Tmin) / 2 EGEE 10211Heating Degree Days Calculate the number of degree days accumulated in one day in which the average outside temperature is 17F.Degree days = 1 day (

6、 65 Tout) = 1 (65-17)= 48 degree days EGEE 10212Heating Degree Days in a Heating Season Calculate the degree days accumulated during a 150-day heating season if the average outside temperature is 17FSolution:Heating Season Degree days = 150 days ( 65 Tout) = 150 (65-17)= 7,200 degree days EGEE 10213

7、Degree Days for the Heating SeasonEGEE 10214EGEE 10215Class workEGEE 10216Significance of HDD Mrs. Young is moving from Anchorage, Alaska (HDD =10,780) to State college, PA (HDD = 6,000). Assuming the cost of energy per million Btu is the same at both places, by what percentage her heating costs wil

8、l change?SolutionHDD in Anchorage, Alaska = 10,780HDD in State College PA = 6,000Difference = 10,780 - 6,000 = 4,780Saving in fuel costs are%3 .44100780,10780, 4EGEE 10217Home Energy Saver /EGEE 10218Home Heating Costs in State College$890$133$227$305$232$106HeatingCooli

9、ngHot waterAppliancesMisc.LightingTotal $1,891Average HouseEnergy EfficientHouseTotal $1,019EGEE 10219Home Heating Costs Related to amount of insulation, material that resists the flow of heat Insulation is rated in terms of thermal resistance, called R-value, which indicates the resistance to heat

10、flow. The higher the R-value, the greater the insulating effectiveness. The R-value of thermal insulation depends on the type of material, its thickness, and density. R-30 better than R-11EGEE 10220Places to Insulate Attic is usually the easiest ad most cost effective place to add insulation Floors

11、above unheated basements should be insulated Heated basements should be insulated around the foundatonEGEE 10221R-values for Building MaterialsEGEE 10222Thickness of various materials for R-2211011018187766CelluloseCelluloseFiberFiberFiberglassFiberglassPine woodPine woodCommonCommonbrickbrickEGEE 1

12、0223R-Value for a Composite Wall1/2 Plasterboard1/2 Plasterboard 0.450.453 1/2 Fiberglass3 1/2 Fiberglass 10.9010.903/4 Plywood3/4 Plywood 0.940.941/2 Wood siding1/2 Wood siding 0.810.81 R RTOTALTOTAL = 13.10 = 13.10 ftft2 2 F hr F hr BTU BTUR R-Value of material-Value of materialEGEE 10224Home Heat

13、ing Energy Heat loss depends on Surface Area (size) Temperature Difference Property of the wall ( R value)Inside65FOutside30FQ (Btus) t (time, h)=A (area) x Temperature Diff (Ti To)1REGEE 10225Heat Loss),tanRe(RWallofthecesisThermaloutsideTinsideTxArea),tanRe(RWallofthecesisThermaloutsideTinsideTxAr

14、eaThotTcoldQtHeat Loss = QtId Q/t is in Btu/hArea in ft2Tin-Tout in FThen the thermal resistance is R-value. The units of R-value arehrBtuFxfto/2EGEE 10226Wall loss rate in BTUs per hour For a 10 ft by 10 ft room with an 8 ft ceiling, with all surfaces insulated to R19 as recommended by the U.S. Dep

15、artment of Energy, with inside temperature 68F and outside temperature 28F: hrBtuhBTUFxftFFxfttQRateHeatloss/674/1928683200202EGEE 10227Calculation per Day Heat loss per day = (674 BTU/hr)(24 hr) = 16,168 BTU Note that this is just through the wall The loss through the floor and ceiling is a separat

16、e calculation, and usually involves different R-values EGEE 10228Calculate loss per degree day If the conditions of case II prevailed all day, you would require 40 degree-days of heating, and therefore require 40 degree-days x 404 BTU/degree day = 16168 BTU to keep the inside temperature constant. T

17、his is the loss per day with a one degree difference between inside and outside temperature.EGEE 10229Heat Loss for Entire Heating Season. The typical heating requirement for a Pittsburgh heating season, September to May, is 5960 degree-days (a long-term average).Heat loss = Q/t = 404 Btu/degree day

18、 x 5960 degree days= 2.4 MM BtusThe typical number of degree-days of heating or cooling for a given geographical location can usually be obtained from the weather service. EGEE 10230Numerical ExampleEGEE 10231Heat loss Calculation dayhdaysreeAnnualofNumberARQtotal/24deg1EGEE 10232Problem A wall is m

19、ade up of four elements, as follows ” wood siding ” plywood sheathing 3 in of fibber glass ” of sheet rock How many Btus per hour per sq.ft. will be lost through the wall when the outside temperature is 50F colder than inside?EGEE 10233Economics of Adding Insulation Years to Payback = C(i) x R(1) x

20、R(2) x E- C(e) x R(2) - R(1) x HDD x 24C(i) = Cost of insulation in $/square feetC(e) = Cost of energy, expressed in $/BtuE = Efficiency of the heating systemR(1) = Initial R-value of sectionR(2) = Final R-value of sectionR(2) - R(1) = R-value of additional insulation being consideredHDD = Heating d

21、egree days/year24 = Multiplier used to convert heating degree days to heating hours (24 hours/day).EGEE 10234Pay Back Period Calculation Suppose that you want to know how many years it will take to recover the cost of installing additional insulation in your attic. You are planning to increase the l

22、evel of insulation from R-19 (6 inch fiberglass batts with moisture barrier on the warm side) to R-30 by adding R-11 (3.5 inch unfaced fiberglass batts). You have a gas furnace with an AFUE of 0.88. You also pay $0.70/therm for natural gas. GivenC(i) = $0.18/square foot; C(e) = ($0.70/therm)/(100,00

23、0 Btu/therm) = $0.000007/Btu; E = 0.88; R(1) = 19; R(2) = 30; R(2) - R(1) = 11; HDD = 7000EGEE 10235Household Heating FuelEGEE 10236Average Heating Value of Common FuelsFuel TypeNo. of Btu/Unit (Kilocalories/Unit)Kerosene (No. 1 Fuel Oil)135,000/gallon (8,988/liter)No. 2 Fuel Oil140,000/gallon (9,32

24、0/liter)Electricity3,412/kWh (859/kWh)Natural Gas1,028,000/thousand cubic feet (7,336/cubic meter)Propane91,333/gallon (6,081/liter)Bituminous Coal23,000,000/ton (6,400,000/tonne)Anthracite Coal24,800,000/ton (5,670,000/tonne)Hardwood (20% moisture)*24,000,000/cord (1,687,500/cubic meter)Pine (20% m

25、oisture)*18,000,000/cord (1,265,625/cubic meter)Pellets (for pellet stoves; premium)16,500,000/ton (4,584,200/tonne)EGEE 10237Fuel Type - Heating EquipmentEfficiency (%)Coal (bituminous)Central heating, hand-fired45Central heating, stoker-fired60Water heating, pot stove (50 gal.227.3 liter)14.5OilHi

26、gh efficiency central heating89Typical central heating78Water heater (50 gal.2227.3 liter)59.5GasHigh efficiency central heating92Typical central heating82Room heater, unvented91Room heater, vented78Water heater (50 gal.227.3 liter)62ElectricityCentral heating, resistance97Central heating, heat pump

27、200+Ground source heat pump300+Water heaters (50 gal.227.3 liter)97Wood & PelletsFranklin stoves30.0 - 40.0Stoves with circulating fans40.0 - 70.0Catalytic stoves65.0 - 75.0Pellet stoves85.0 - 95.0Typical Heating Furnace EfficienciesEGEE 10238Comparing the Fuel CostsEfficiencyunitoffuelMMBtuueHe

28、atingValofFuelperUnitCostCostEnergy)/(EGEE 10239Fuel Costs Electric resistance heat cost =$0.082 (price per kWh) / 0.003413 x 0.97 (efficiency) = $24.77 per million Btu. Natural gas (in central heating system) cost =$6.60 (per thousand cubic feet) / 1.0 x 0.80 (efficiency) = $8.25 per million Btu. O

29、il (in central heating system) cost =$0.88 (price per gallon) / 0.14 x 0.80 (efficiency) = $7.86 per million Btu. Propane (in central heating system) cost =$0.778 (price per gallon) / 0.0913 x 0.80 (efficiency) = $10.65 per million Btu.EGEE 10240Heating Systems EGEE 10241Heating Systems Some hot wat

30、er systems circulate water through plastic tubing in the floor, called radiant floor heating.EGEE 10242Electric Heating Systems1.Resistance heating systems Converts electric current directly into heat1. usually the most expensive 2. Inefficient way to heat a building 2.Heat pumpsUse electricity to m

31、ove heat rather than to generate it, they can deliver more energy to a home than they consume1. Most heat pumps have a COP of 1.5 to 3.5.2. All air-source heat pumps (those that exchange heat with outdoor air, as opposed to bodies of water or the ground) are rated with a heating season performance f

32、actor (HSPF)EGEE 10243Geothermal Heat Pumps They use the Earth as a heat sink in the summer and a heat source in the winter, and therefore rely on the relative warmth of the earth for their heating and cooling production.Additional reading/erec/factsheets/geo_heatpumps.html#sid

33、ebarEGEE 10244Benefits of a GHP System Low Energy Use Free or Reduced-Cost Hot Water Year-Round Comfort Low Environmental Impact Durability Reduced Vandalism Zone Heating and Cooling Low MaintenanceEGEE 10245Solar Heating and Cooling Most American houses receive enough solar energy on their roof to

34、provide all their heating needs all year! Active Solar Passive SolarEGEE 10246Passive Solar A passive solar system uses no external energy, its key element is good design: House faces south South facing side has maximum window area (double or triple glazed) Roof overhangs to reduce cooling costs The

35、rmal mass inside the house (brick, stones or dark tile)EGEE 10247Passive Solar Deciduous trees on the south side to cool the house in summer, let light in in the winter. Insulating drapes (closed at night and in the summer) Greenhouse addition Indirect gain systems also such as large concrete walls

36、to transfer heat insideEGEE 10248Passive Solar HeatingEGEE 10249Source: Global Science, Energy Resources EnvironmentEGEE 10250D D i i r re ec ct t G Ga ai i n nT Th he er rm m a al l S St to or ra ag ge eW W a al ll lS Su un ns sp pa ac ce eP Pa as ss si i v ve e H H e ea at ti i n ng gP Pa as ss si

37、 i v ve e C Co oo ol l i i n ng gS Sh ha ad di in ng gV V e en nt ti il la at ti io o n nE Ea ar rt th h C Co on nt ta ac ct tEGEE 10251Active Solar Heating Flat plate collectors are usually placed on the roof or ground in the sunlight. The sunny side has a glass or plastic cover. The inside space i

38、s a black absorbing material. Air or water is pumped (hence active) through the space to collect the heat. Fans or pumps deliver the heat to the houseEGEE 10252Active Solar HeatingEGEE 10253Flat Plate Collector Solar Collectors heat fluid and the heated fluid heats the space either directly or indir

39、ectlyEGEE 10254Efficiency of Furnace The combustion efficiency gives you a snapshot in time of how efficient the heating system is while it is operating continuously The annual fuel utilization efficiency (AFUE) tells you how efficient the system is throughout the year, taking into account start-up,

40、 cool-down, and other operating losses that occur in real operating conditions. AFUE is a more accurate measure of efficiency and should be used if possible to compare heating systems.EGEE 10255Efficiencies of Home HeatingU.S. stockU.S. stock1975-1976 building practice1975-1976 building practice(NAH

41、B)(NAHB)LBL standardLBL standard(medium infiltration)(medium infiltration)LBL standardLBL standard(low infiltration)(low infiltration)BrownellBrownellSaskatoonSaskatoonPasquaPasquaSaskatche-Saskatche-wan housewan houseIvanhoeIvanhoeMastinMastinLegerLegerBalcombBalcombPhelpsPhelps1 Btu/ft1 Btu/ft2 2

42、per degree day per degree dayAnnual fuel input forAnnual fuel input forspace heat (10space heat (106 6 Btu/1000 ft Btu/1000 ft2 2) )Btu/ftBtu/ft2 2 per degree day per degree dayDegree days (base 65F)Degree days (base 65F)1101101001009090808070706060505040403030202010100 00 02000200040004000600060008

43、000800010,00010,0009 97 75 53 31 1EGEE 10256Tips (Individual) to Save Energy and Environment Set your thermostat as low as is comfortable in the winter and as high as is comfortable in the summer. Clean or replace filters on furnaces once a month or as needed. Clean warm-air registers, baseboard heaters, and radiators as needed; make sure theyre not blocked by furniture, carpeting, or drapes. Bleed trapped air from hot-water r