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Bubble Couches

A bubble couch is a forced air assistance feature within the interior portion of a spa or pool.

Bubble couches should not be designed on the exterior of the pool. If there must be a bubble couch on the exterior of the pool, a railing will need to be spe  All bubble couches should be designed on the interior to avoid potential trip and fall hazards.

A manifold should be used to balance flow distribution.

  • Basis of Design
    • The air velocity should be between 2,000 to 4,000 FPM
    • A single orifice (outlet, jet, or nozzle) should pass 1.0 CFM.
    • Branch piping should contain and odd number of orifices (9, 11, 13) to make the airflow calculations easier
    • Manifold to branch piping should be symmetric (or paired)
    • The blower output capacity should have a 15% safety margin
    • Orifice Flow Calculation
      • V=CK(P)1/2
      • Q = AV
      • VP= (V/K)2
      • Coefficient C = 0.8, K = 4005 when P is expressed in inches of water
    • Air density = 0.075 lb/cf

Example

The bubble couch will have four branch pairs with 11 orifices per branch. The couch is approximately 300 LF from the mechanical room. Assuming one Hartford loop and a total of six additional elbows will be required.  The orifice size will be assumed to have a 5/16” average opening.

  • Blower Output
    • (1 CFM / nozzle) * (11 nozzles / row) * (8 rows) = 88 CFM
    • (88 CFM) * (1.15 safety factor) = 2 CFM (design point)
  • Size the Pipe
    • Q = VA or A = Q/V = 100 CFM / 4000 FPM
    • Area of 0.025 SF
    • Pipe ID 2.14” (falls between 2” and 2-1/2”)
      • 2” – 1.939” / 2.5” – 2.323”
      • Use the 2.5” (as a minimum)
      • V = 100 CFM / A (0.0294 SF) = 3,400 FPM
  • Obtain Friction Loss from the Chart
    • 2-1/2” diameter at 3,400 FPM = 075 in wc / LF (+/-)
  • Total Friction Loss
    • Len. * F = (300 LF + 10 (6.9) ={369}) * .075 = 27.6 in wc (loss)

 

  • Total Pressure = Pt = Ps+ Pv + Pn + Pf
    • Ps = 12 inches (Ps = 12”) – Static Pressure
    • Pv = (Orifice Velocity / 4005)2 = (1880 / 4005)2 = 0.22 in wc
    • Pn = (Orifice Velocity / (C*K)2 = (1800 / 3204)2 = 2.9 in wc
    • Pf = 27.6 in wc
    • Pt = 12 + 27.6 + 0.22 + 2.9 = 42.7 in wc *1.20 (SF) = 52 in

 

  • Blower Sizing Requirements
    • 101 SCFM with a minimum of 52” water column (output).
    • Blowers may have system induced pressure drops (not accounted for)
      • Discharge: oil separators, filters, or dryers
      • Inlet: mufflers, inlet conditions
  • The pneumatic pipe size from the blower to the bubble couch
    • 2-1/2” SCH 80 pipe.

Bubble couches are not allowed in Illinois.

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