Chilled Water Distribution Design Considerations in Super Tall Buildings. Dusan Mrdalj, Associate, ChapmanBDSP

Transcription

1 Chilled Water Distribution Design Considerations in Super Tall Buildings Dusan Mrdalj, Associate, ChapmanBDSP

2 Dusan Mrdalj Bio - MSc Mechanical Engineering - Associate in ChapmanBDSP - 20 years of Professional Experience - 12 Years in the UAE - Involved with design of iconic supertall buildings (WTC AD, OT Dubai )

3 SUPERTALL BUILDINGS AC DESIGN CONSTRAINTS - Building Height vs System Pressure Limitations - Comfort Conditions - Plantroom Space & Access

4 BUILDING HEIGHT

5 HYDROSTATIC PRESSURE IN WATER COLUMN where p = ρ g h p = pressure in liquid (N/m 2, Pa, lb f /ft 2, psf) ρ = density of liquid (kg/m 3, lb/ft 3 ) g = acceleration of gravity (9.81 m/s 2, ft/s 2 ) h = height of fluid column (m, ft)

6 COMFORT CONDITIONS - Temperature - Air Distribution - Stack Effect

7 PLANTROOM SPACE & ACCESS

8 COOLING ENERGY GENERATION Chillers Types (Condensers) Air Cooled Water Cooled

9 CHILLED WATER PRESSURE BREAK CONCEPT Plate Heat Exchanger p3 p2 p1

10 CHILLED WATER TEMP. AT TOB Counter flow Co-current flow Plate HEX Δt 1 C

11 TYPCIAL FCU SELECTION SHEETS

12 FCU CAPACITY VS CHW SUPPLY TEMPERATURE FCU COOLING CAPACITY IN RELATION TO CHW SUPPLY TEMPERATURE FCU Total Capacity (kw) FCU Sensible Capacity (kw) FCU Latent Capacity (kw) Assumed Conditions Standard FCU size 12 at medium speed CHW Delta T: 7 C On-coil DB/WB: 22.5/17 C FCU LATENT CAPACITY IN RELATION TO CHW SUPPLY TEMPERATURE FCU Latent Capacity (kw)

13 FCU CAPACITY VS CHW SUPPLY TEMPERATURE FCU COOLING CAPACITY IN RELATION TO CHW SUPPLY TEMPERATURE FCU Total Capacity (kw) FCU Sensible Capacity (kw) FCU Latent Capacity (kw) Assumed Conditions District Cooling FCU size 12 at medium speed CHW Delta T: 9 C On-coil DB/WB: 22.5/17 C FCU LATENT CAPACITY IN RELATION TO CHW SUPPLY TEMPERATURE FCU Latent Capacity (kw)

14 FCU CAPACITY VS CHW SUPPLY TEMPERATURE FCU COOLING CAPACITY IN RELATION TO CHW SUPPLY TEMPERATURE FCU Total Capacity (kw) FCU Sensible Capacity (kw) FCU Latent Capacity (kw) Assumed Conditions District Cooling FCU size 12 at medium speed CHW Delta T: 9 C On-coil DB/WB: 25/18.7 C FCU LATENT CAPACITY IN RELATION TO CHW SUPPLY TEMPERATURE FCU Latent Capacity (kw)

15 DISTRIBUTION PIPEWORK HEAT GAINS

16 HOW TO RESOLVE 1. CHILLERS AT HIGH ELEVATION 2. LOW TEMPERATURE CHILLERS AT BASE 3. HYBRID SOLUTION

17 CHILLERS AT HIGH ELEVATION PROS CHW generation closer to demand - less distribution losses CHW temperature not affected by pressure breaks Lower temperature CHW easily achieved No requirement for low temperature/glycol chillers Less space for primary services CONS Large plantroom required in premium space up in the building Pressure breaks required in condenser water circuit Special access arrangements for chillers installation & replacement More power needed to be transmitted up the building Noise and vibration issues more severe

18 CHILLERS AT BUILDING BASE PROS Removes need for large plantroom up in the building and associated access Less power up the building required Noise and vibration less of an issue No pressure breaks in condensing circuit required CONS CHW generation farther from demand - more distribution losses Pressure breaks required in CHW circuit Chillers required to operate at low temperature/glycol chillers More space for primary services

19 HYBRID SOLUTIONS Small chillers installed up in the building Designed as a back-up to deal only with critical cooling load (FLS or Server rooms) Can be used to achieve desired CHW supply temperature in case of high fluctuation in cooling load Smaller units in modular arrangement recommended

20 DISTRICT COOLING UTILIZATION

21 STANDARD CHILLERS EFFICIENCY - Air Cooled Chillers - Water Cooled Chillers with Cooling Towers - Water Cooled Chillers with District Cooling - Water Cooled Chillers with Glycol

22 CHILLERS EFFICIENCY SELECTION OPTIONS Option 1 Option 2 Option 3 Option 4 Type: Air Cooled Type: Water Cooled Type: Water Cooled Type: Water Cooled Capacity: 500 TR Capacity: 500 TR Capacity: 500 TR Capacity: 500 TR OA DB: 46 C CW in/out: 35/40 C CW in/out: 12/17 C CW in/out: 12/17 C CHW: 5/14 C CHW: 5/14 C CHW: 5/14 C Glycol: 2/11 C

23 CHILLERS EFFICIENCY SELECTION 1

24 CHILLERS EFFICIENCY SELECTION 2

25 CHILLERS EFFICIENCY SELECTION 3

26 CHILLERS EFFICIENCY SELECTION 4

27 CHILLERS EFFICIENCY COMPARISON Peak Power (kw) Option 1 Option 2 Option 3 Option Option 1 Option 2 Option 3 Option 4

28 CHILLERS EFFICIENCY COMPARISON COP Option 1 Option 2 Option 3 Option Option 1 Option 2 Option 3 Option 4

29 QUESTIONS