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Technology in Architecture

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1 Technology in Architecture
Lecture 11 Mechanical System Space Requirements Mechanical System Exchange Loops HVAC Systems

2 Mechanical Room Sizing

3 Mechanical Room Contains primary equipment (boiler, chiller, etc.)
Usually adjacent to other service areas (loading docks, electrical substation, transformer vault, etc.) Generally away from public entry Include space for service/maintenance M: p. 444, F.12.12

4 Mechanical Room Sizing
Generally sized based on total floor area in building served M: p.435, F.12.7

5 Mechanical Room Sizing
Size mechanical room space Application Square Footage M: p.435, F.12.7

6 Mechanical Room Sizing
Sizing Example 150,000 SF Department Store Mechanical Room: 3,200 sf M: p. 435, F.12.7

7 Fan Room Sizing

8 Fan Rooms Contain secondary equipment (air handlers, heat exchanger, etc.) Usually adjacent to or within area served Include space for service/maintenance M: p. 479, F.12.49

9 University of Michigan Hospital,
Fan Rooms Require connection/ access to fresh air Require means of discharging return air/ exhaust air Minimum 25’ distance of fresh air inlet away from contaminant source University of Michigan Hospital, Ann Arbor, MI

10 Fan Room Sizing Generally sized based on total floor area of the thermal zone in building served M: p. 436, F.12.8

11 Fan Room Sizing Size fan room Application Square Footage
M: p. 436, F.12.8

12 Fan Room Sizing Sizing Example 150,000 SF Department Store
Supply/Return Mains: 120 sf for each Fan Room: 5,200 sf Fresh Air Inlet: 500 sf Exhaust Air Outlet: 400 sf M: p. 436, F.12.8

13 Fresh Air Inlets Avoid contamination sources (25’ minimum)
Loading docks Smoking areas Cooling Towers Exhaust air outlets Plumbing vents Others…

14 Mechanical System Exchange Loops

15 Mechanical System Exchange Loops
Heat is removed/ added via heat exchange loops. M: p. 439, F.12.9

16 Mechanical System Exchange Loops
Cooling Mode M: p. 439, F.12.9

17 Mechanical System Exchange Loops
Heating Mode M: p. 439, F.12.9

18 Cooling Tower

19 Cooling Tower Divided into a series of cells for redundancy/ serviceability Significant structural load: Rooftop vs At-grade Potential air contamination Locate based on prevailing wind direction M: p.465, F

20 University of Michigan Hospital,
Cooling Tower Service access needed for water treatment/debris removal Biocides can cause etching on glass and other surfaces Minimum 25’ distance away fresh air inlet or fenestration University of Michigan Hospital, Ann Arbor, MI

21 Cooling Tower Sizing Sizing Example 150,000 SF Department Store
Cooling Tower: 560 sf M: p.435, F.12.7

22 HVAC Systems

23 System Types All-Air Air-Water All-Water Unitary Refrigerant System

24 Selection Criteria Control capability and flexibility required
Environmental requirements Cost of construction Energy consumption System effficiency

25 All-Air Systems Heating/cooling media delivered via air only
Advantages: Humidification & Heat recovery Complex zoning Close humidity & temperature control (exc. VAV) Can use outside air for economizer cycle Disadvantages: Special care for maintenance access Supplemental perimeter radiation may be needed Higher volume of space needed

26 All-Air Systems Single zone Terminal reheat Multizone Dual duct
Variable air volume (VAV)

27 Single Zone One thermostat controls several rooms in a single thermal zone Applications requiring air filtration and humidity control Uneven comfort for multiple rooms

28 Terminal Reheat One thermostat controls one room as a single thermal zone with a reheat coil control discharge air temperature Poor energy efficiency

29 Multizone One thermostat controls discharge dampers to adjust air temperature to each room Small buildings with limited distances for duct runs Simultaneous heating and cooling

30 Dual Duct One thermostat controls mixing box for each room
Applications requiring precise control of temperature and humidity Energy inefficient High maintenance Expensive to build

31 Variable Air Volume One thermostat controls VAV valve for each room and reduces airflow under lower load Applications where loads vary significantly (offices, schools) Poor humidity control Subcooling

32 Chilled Beams Source: article.php?L=5&C=463&P=4

33 Chilled Beams Source: article.php?L=5&C=463&P=4

34 Chilled Beams Integration of geothermal and VAV

35 Distribution Paths Air may be distributed from the ceiling or the floor

36 Distribution Paths—Ceiling
Conventional distribution is from the ceiling Air discharge: 55ºF Velocity is fpm M: p.544 F

37 Distribution Paths—Floor
Also known as displacement cooling Air discharge: 60+ºF Velocity is slower than ceiling discharge Higher ceilings M: p. 559, F M: p. 394, F.10.12

38 Air-Water Systems Heating/cooling media delivered via air and water
Advantages: Flexible placement Centralized humidity and filtration Space heating Disadvantages: Condensation Noise Induction Fan Coil Unit M: p. 396, F.10.13

39 All-Water Systems Heating/cooling media delivered via water only
Advantages: Flexible placement Space heating Disadvantages: Condensation Noise

40 Fan Coil Unit Fan draws air from room across coils Flexible Less space
Low cost Noise Poor ventilation/humidity Maintenance Condensation control Simultaneous heating and cooling M: p. 398, F.10.14

41 Unitary Refrigerant System
Heating/cooling media delivered via local equipment Advantages: Individual room control Independent heating and cooling Single zone affected by malfunction Low initial cost Reliability Disadvantages: Short life Noise Humidity control Air filtration Ventilation Through the wall air-conditioning Heat pumps

42 ARCH-4372/6372 HVAC Distribution & Sizing HVAC Distribution Systems
Diffuser Selection and Layout Ductwork Sizing

43 HVAC Distribution Systems

44 Distribution System Plans Symbols
Positive Pressure (supply) Negative Pressure (return or exhaust)

45 Distribution System Plans Symbols
Arrow indicates air flow direction

46 Distribution System Plans Symbols
Flow patterns 1-way 2-way 3-way 4-way

47 Distribution System Plans Symbols
Thermostat Smoke/Fire Damper T

48 Distribution System Plans Symbols
Double Line Single Line

49 Distribution System Plans Symbols
Section z z 16 x 12 z z 12 x 16

50 Distribution System Plans
Double Line Single Line

51 Distribution System Plans
Double Line Single Line

52 Ceiling Plenum Plans Shows duct path from distribution network to supply diffuser or return register

53 Diffuser Selection and Layout

54 Diffuser Selection Diffuser Selection Criteria Air flow Throw
Noise Criteria (NC) Level Appearance

55 Diffuser Selection Air Flow Throw NC Level

56 Diffuser Selection Throw: Avoid Gaps and overlap
Distance of air movement Avoid Gaps and overlap Obstructions/deflectors Velocity (fpm)

57 Diffuser Layout 1. Use Room Sensible Load (no latent, no ventilation) to determine air flow Qs=1.08 x CFM x ΔT where ΔT=|Tsa-Tra| thus CFM= Qs (1.08 x ΔT)

58 Diffuser Layout 2. Define Supply Air temperatures Heating:
Tsa range is ºF Tra=68ºF Cooling: Tsa range is 45-55ºF Tra=78ºF

59 Diffuser Layout 3. Define ΔT Heating: ΔT=|110-68|=42ºF Cooling:

60 Diffuser Layout 4. Determine Air Flow (CFM) CFMhtg= Qs (1.08 x ΔThtg)
CFMclg= Qs (1.08 x ΔTclg) Larger result determines air flow

61 Diffuser Layout 5. Revise discharge air temperature to match required air flow CFMpeak= Qs (1.08 x |Tsa-Tra|) solve for Tsa

62 Diffuser Layout 6. Select diffuser layout Regular pattern
Uniform coverage Avoid “short circuiting” with exhaust/return registers

63 Diffuser Layout Example
Office space with overhead heating and cooling supply NC level 35 16’ 8’

64 Diffuser Layout Example
Heating Qs= 11,800 Btuh Discharge=110ºF Set point = 68ºF ΔT = 42ºF CFMhtg= Qs (1.08 x ΔT) =11,800/(1.08 x 42)=260 CFM

65 Diffuser Layout Example
Cooling Qs=8,600 Btuh; ΔT= 42ºF CFMclg= Qs (1.08 x ΔT) =8,600/(1.08 x 23)=346 CFMHTG= 260 < CFMclg =346

66 Diffuser Layout Example
Revise Heating Tsa CFMpeak= Qs (1.08 x ΔT) =346=11,800/(1.08 x |Tsa-68|) Tsa=99.6ºF

67 Diffuser Layout Example
Define Pattern 346 Cfm Round up to 0 or 5 cfm cfm cfm cfm cfm

68 Diffuser Layout Example
Define Pattern 346 Cfm Round up to 0 or 5 cfm cfm 2-way cfm 4-way cfm 3-way cfm 2-way 16’ 8’

69 Diffuser Selection NC 35 Air Flow Throw Select 8” Rd 4-way

70 Diffuser Layout Example
Define Pattern 346 Cfm cfm 4-way 4’ 4’ 4’ 4’ 16’ 4’ 4’ 4’ 4’ 8’

71 Return Register Selection
Selection Criteria Air flow Noise Criteria (NC) Level Appearance

72 Return Register Selection
Air Flow NC Level

73 Return Register Layout
Avoid Short circuiting with supply diffusers Locating in visually obtrusive location

74 Return Register Layout
Define Pattern Supply=350 cfm Return cfm 16’ 8’

75 Return Register Selection
Air Flow 350 cfm NC Level 35 Select 10” x 8” 350 cfm NC 27db

76 Return Register Layout
8’ 16’ Define Pattern Supply=350 cfm Return cfm 10” x 8” NC 27db

77


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