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0 08 06 04 q r s t 02 where q 0082597

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Unformatted text preview: ange: = () or = ∙ () Alternate Plot of DOE-2 Default Boiler Performance Curve 1.0 0.8 () 0.6 0.4 = () Q + R ∙ + S ∙ T 0.2 where: Q = 0.082597 S = −0.079361 R = 0.996764 0.0 = 0.0 0.2 0.4 0.6 0.8 1.0 Example Calculation: = 0.8 (80%) = 0.562 = Q + R ∙ + S ∙ T = 0.618 using default performance curve (i.e. coefficients A, B, C) 0.562 = = 6. :6: = ( ) 0.618 = × 0.909 = 0.80 × 0.909 boiler efficiency for analyzed hour = 6. ;? (73%) losses , boiler 3863 W , 2812 W _`a` = bca` 2812 W = 3863 W = 6. ;? Alternate Plot of DOE-2 Default Boiler Performance Curve 1.0 0.8 0.6 0.4 0.2 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1.0 0.8 () 0.6 0.4 0.2 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 1.0 () 0.8 0.6 0.4 0.2 0.0 Aside: Compare two methods of displaying performance curves 1.0 0.8 () 0.6 0.4 “flat efficiency curve” (i.e. for a device whose efficiency does vary with part-load) 0.2 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 1.0 () 0.8 0.6 0.4 0.2 0.0 Building Energy Performance – Spring 2012 - Topic 18 Aspects of Building Energy Simulation (Part 3) Utilizing Simulation Analysis for Design Guidance / Decision Making? Misc Electrical $8,193 Space Heating $23,056 Lighting $8,287 Water Heating $12,092 HVAC Fans $7,083 Space Cooling $4,763 Recall from Week 3: Hourly Heating Loads from a Particular Energy Simulation of a Building 500 450 400 350 300 Boiler Load (MBH) 250 200 150 100 Summer heating system shutdown 50 0 1 1001 2001 3001 4001 Hour 5001 6001 7001 8001 Load Duration Curve 500 (From energy simulation results) 450 400 peak load (∼ 390 MBH) 350 300 Boiler Load (MBH) 250 200 150 100 50 0 1 1001 2001 3001 4001 Hour # 5001 6001 7001 8001 Simulation Analysis • Theoretical office building in Toronto, Ontario • 2-storeys; 20,000 ft2 total floor area • Typical insulation, lighting, equipment, number of people, and ventilation rates • HVAC: VAV air-handling, hydronic heating/nat gas boiler Depiction of theoretical 20,000 ft2 office building Recall: O/A Damper “Variable-Air-Volume (VAV) System” Mixed Air Cooling Heating Variable Volume Supply Fan To Other Zones Economizer R/A Damper VAV box VAV box T ZONE 1 R/F heater T ZONE 2 heater From Other Zones Boiler Plant + Heating Loop: flue Boiler Plant heat input to loop heating loop pump fuel flue input Boiler-3 output flue input Boiler-2 output flue input Boiler-1 output heat demand radiators, heating coils, etc. Schematic Depiction of Connection of Heating Loop and “Air-Side” System cooling system Fresh-Air Damper Heat Fresh Air Air-Handling Unit Mixing Cooling Coil Electricity Heating Coil Supply Air Drain VAV Damper VAV Damper Thermal Zone T Thermal Zone T Other Zones Heater Heater Heat Exhaust-Air Exhaust Damper Air Heat Recirculated Air Heat Supply Fan Return Air To Boiler and Pump heating loop Hour-by-hour whole-building energy simulation performed with DOE-2 using “EE4” graphical interface Computer analysis used to estimate peak heating load. Results for example: Calculated Peak Heating Load = 390 MBH Oversizing Factor = ? Capacity of Selected Boiler = ? Note In IP units, “MBH” = thousands of btu/hr. Computer analysis (simulation) is run to estimate hourly loads for an entire year (8760 hours). Partial results for example: 500 450 e.g. Average load during hour # 4 is ≈140 MBH 400 350 Left axis: Hourly load (in MBH) 300 250 200 150 100 50 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Bottom axis: Hour # Estimated Hourly Boiler Loads Boiler Plant 500 450 heat to loop (Load) heating loop 400 350 Load (MBH) 300 250 200 150 100 Assumed Summer shutdown period 50 0 1 1001 2001 3001 4001 Hour 5001 6001 7001 8001 Heating Load Duration Curve: Boiler Plant 500 heating loop heat to loop (Load) 450 400 500 peak 100 hours of highest loads 450 400 350 350 300 Load (MBH) 300 250 250 200 150 200 100 50 150 0 1 11 21 31 41 51 61 71 81 91 101 100 50 0 1 1001 2001 3001 4001 Hour 5001 6001 7001 8001 Say design is to be a single-boiler (i.e. sized to meet peak load + safety factor) capacity of selected boiler including “oversizing factor” (safety-factor) 500 450 400 calculated peak flue 350 Load (MBH) Boiler 1 300 250 output input 200 rated output = 500 MBH 150 rated input = 625 MBH 100 rated efficiency = 80% 50 0 1 1001 2001 3001 4001 Hour 5001 6001 7001 8001 Part-Load Performance of Selected Boiler? 1.0 0.8 0.6 0.4 0.2 0.0 0.0 0.2 0.4 0.6 0.8 1.0 capacity 500 450 400 350 300 Load (MBH) 250 200 150 100 50 0 1 1001 2001 3001 4001 Hour # 5001 6001 7001 8001 Applying the Part-Load Performance Adjustment to the Load Duration Curve… 550 500 450 400 350 MBH 300 250 Note: In this analysis, an adjustment has been made to prevent very short boiler cycling, so there is a “bump” in the curve. 200 150 100 50 0 1 1001 2001 3001 4001 Hour 5001 6001 7001 8001 Load and Fuel Use 550 500 Annual LOAD = area under LOAD curve = 443 MMbtu 450 Annual FUEL = area under FUEL curve = 777 MMbtu 400 Boiler Losses = area between curves = 335 MMbtu 350 MBH Annual Efficiency = 57% 300 250 200 150 100 50 0 1 1001 2001 3001 4001 Hour 5001 6001 7001 8001 Typical Seasonal Efficiencies of Selected Heating System Types Boiler/System Type Typical Seasonal Efficiency Condensing Boilers • Under-floor or warm water system 90% or greater • Standard sized radiators, variable temperature circuit (outdoor air reset) 87% • Standard fixed temperature radiators (supply = 83°C, return = 72°C) 85% Non-Condensing boilers • Modern “high efficiency” non-conde...
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This note was uploaded on 10/04/2012 for the course ME 760 taught by Professor Davidmather during the Spring '12 term at Waterloo.

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