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ExerciseWater pipe, Pump and
Cooling Tower Selection
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Watercooled VRV Selection: VRV WII - Express
• Cooling Load per floor is 40 kW, Heat load 16.5 kW– 10 HP VRV unit gives >130% connection ratio– 20 HP VRV unit gives 80-110% connection ratio,
Depending on piping length– 30 HP VRV unit gives <66% connection ratio
20 Hp unit is selected
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Learning, our wayCooling unit Selection
• Cooling tower, evaporative cooler or dry cooler?Approach: 8°C, mild climate.
Europe, small scale installation(No large water purification installation needed)
Type: Evaporative fluid coolersBrand Baltimore: Type VXI
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Cooling mode: (VRV express)• Total heating capacity available= 49.5W *4 • Total Power Input at 98% connection ratio = 9.0 kW *4• Total rejected heat = 4 *(49.5+9.0)= 234 kW• Total water flow (= max water flow )= 96 * 2* 4
= 768 l/min = 12.8 l/s • Range= EWC – LWC = rejected heat / (4.186 x water flow)
=177.6 / (4,186 x 12,8)= 4,37°C• EWC= cooling tower entering water temperature= 30 + 4,4 = 34,4°C• LWC= cooling tower leaving water temperature = 30 °C
Approach = LWC – WBT = 30°C – 22°C = 8°C
Calculations Evaporative Cooler Selection:
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Selection Evaporator
Determine the performance factor using the diagramsprovided by Baltimore:
Input: Range = 4.4 Approach = 8°C WBT = 22°C
Output: Pf = 5
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Heating mode:
• Total Heat capacity required= 63 kW *4
• Total Power Input = 6 kW *4• Total injected heat = 4 *(63-6)= 228 kW
Calculations Boiler Capacity:
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Water piping: water flow rates
• Each VRV has as design waterflow– 96 l/min per 10 Hp unit.
• Horizontal piping to indoor units:– 2 x 96 l/min = 192 l/min
• Vertical parts: Different sections A, B, C, D– Secton A: Only 1 20 HP unit: 192 l/min (=3,2l/s)– Section B: 2x 20 HP unit : 384 l/min (=6,4l/s)– Section C: 3x 20 HP unit, 576 l/min (=9,6l/s)– Section D: 1x 10 HP Sub-unit, 96l/min (=1,6l/s)– Section E: 4x 20 HP unit: 768 l/min (=12,8l/s)
• Reverse Return Distriubution
* *
A
B
C
DE
A
C
B
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Piping diameters
Reccomendations:
Pipe diameter (mm)
Velocity range (m/s)
125 2.1~2.7
50 ~ 100 1.2~2.1
Around 25 0.6~1.2
A
B
C
D
E
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Reference Path: Take worse case:3m C+B+C+horizontal: 3m A+B+C+horizontal
Linear Head Loss• Using Friction loss graph:
Opposite effect of joints
Comparable results!
Part: Flow rate (l/s)
Diameter (mm)
Water velocity (m/s)
Length (m)
Pressure loss per meter (Pa/m)=10mH2O/m
Total (mH2O)
A 3.2 50 1,5 2x5
+3
70 0,91
B 6.4 65 1.9 3 70 0,21C 9.6 80 1,5 3 50 0,15
D 1.6 40 0,9 2 x 1 50 0,1E 12.8 100 1.6 12 15 0,18
+3 +0.15
-0.21
* *
A
B
C
D
A
C
B
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Water Pipe Design: Local Head losses
• Local friction losses: For 1 water route:– 3 branches “Straight Trough”- 2 x “Trough Branch” connection on main
line (2 for each 10 HP unit, speed )- 2 x “Trough Branch” Joint on indoor piping- 2x 3 elbow joints on indoor piping
• Straight line friction losses: – 4 x 3 m vertical piping, – 2 x 3 m indoor piping
* *
A
B
C
DE
A
C
B
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* *
A
B
C
DE
A
C
B
Local Head loss: Blue path
T joints “Straight Trough”• E to C
• C to B
• B to A
.
Partial head lossHtLocation:
Number ON
1 water path Equivalent piping length (m)
Pressure loss / m (mmH2O/m)
Pressure loss
(mH2O)
Elbows on A 2*2 + 1 5 * 1.6 70 0.56
Elbows on D 2*1 2 * 1.3 70 0.18
Elbows on E 2 2 * 1,3 70 0.18
T-joints Staight-tru (on main line)
3 1,7+1.7+1.4
70 0.34
T-joints Tru Branch (on main line)
1 5.7 70 0.40
T-joints Tru Branch (on horizontal line)
2 2.8+3.5 70 0.44
T joint “Trough Branch”•A to E
-1
+1
-0. 11
+ 5.7
•B to A•A to C
•E to C•C to B•C to E
vs Red path
+0.02
+0.29 4.2
+ 1.7
Total: +0.20
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Learning, our wayPiping design – pump selection properties
H = Ha + Hf + Ht + Hk
Ht = Linear Head loss = 1.55 mH2OHa = Actual head (m H2O) = 0Ht = Partial friction loss = 2,23 m H2OHk = Internal friction loss = 2,7 mH2O
1 x 1 VRV 10 HP unit, at 96 l/minHk2 = Given, 5 mH2O
Total head loss= 11,48 mH2O at a flow rate of 768 l/min46 m3/hr
+0.14 mH2O
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Learning, our wayWater piping design: Pump Pre-selection
LRC 406