active chilled beams in healthcare -...
TRANSCRIPT
Learning Objectives
• Technology overview• Code review and applicable space types• Understanding operational and maintenance implications• Economics• Best practice design and selection guidelines
• A chilled beam is a sensible only cooling device that uses chilled water to remove heat from the space • Decouple ventilation and sensible cooling loads
• Active vs Passive• Induction ratios • 2 pipe vs 4 pipe
Chilled Beam Basics
Patient Room – Chilled Beam
Patient Room ‐ Induction Unit
Patient Room – VAV Design
• Why decouple the ventilation and cooling loads?• Density
• Water: 62.4 lb/ft3
• Air: 0.065 lb/ft3
• Water has 960 times the mass per unit volume• Specific heat
• Water: 1 btu/lb‐F• Air: 0.24 btu/lb‐F• Water has 4.16 times the thermal energy
• Combined water can transport 4000 times as much energy per unit volume• 1” pipe has an equivalent heat transfer capacity to a 18” x 18” duct
Why?
Codes and Standards
Applicable Space Types
Applicable space types
Chilled Beams – 2 pipe vs 4 pipe
User and Operator ExperienceCase Study: HCAHPS Scores
Load Calc ‐ Sensible
VAV75F: 425cfm; 12.4ach72F: 500cfm; 14.5ach70F: 565cfm; 16.4ach
LoadsInternal• Lighting: 0.7 W/SF = 550 btuh• Equipment: 2 W/SF = 1570 btuh• Occupant: 3 @ 250 btuh/ea = 750 btuhSolar• South exposure: 4930 btuh
Total Sensible Load: 7800 btuh
Chilled Beam75F: 175cfm; 5 ach72F: 200cfm; 5.8 ach70F: 220cfm; 6.5 ach
Typical reduction in total HVAC energy of 20‐40%
Typical Med/Surg Patient Room
Floor Plan Comparison – First Cost
33% less ductwork
Traditional VAV Chilled Beam
Primary Air Calc
Typical Med/Surg Patient Room225SF
cfm = q / [0.57(abs h_space – abs_h_SA)]
Space temp: 75F/50%RH; 81.3 gr/lb; DP = 55FSupply air: 55/53; 70.4 gr/lb DP = 51.8FLatent load: q= (3) Occupants @ 200 btuh/ea = 600 btuh
abs_h_space = 81.3 gr/lbAbs_h_SA = 70.4 gr/lb
cfm = 600 / [.57 (81.3 – 70.4)] = 100 cfm
Min code: 2ach = 75cfm
Min primary air req’d = 100cfm
Sample Chilled Beam Selection
Condensation and ControlsLab Testing ‐Condensation
• 100% OA units• Enthalpy wheel• Runaround loop
AHU Design
• Process chilled water loop design• Airside balancing options • Facilities training• Control valve location• Elevation derate
Additional Design Considerations
SummaryTakeaways• Function: Decouple ventilation &
sensible cooling loads• Design: Removal of return air system