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System Curves

Pumps ႏွင့္ pumping systems တ့ုိကို the pressure head ႏွင့္ flow rate တုိ့အေပၚတြင္ မူတည္၍ ဒီဇုိင္းဆြဲၾကသည္။

pressure head ႏွင့္ flow rate တုိ့သည္ တစ္ခုကို တစ္ခု အၿပန္အလွန္ အမွီၿပဳေနၾကသည္။

pump မွ တြန္းပိုႏိုင္သည့္ pressure သည္ piping system မွ ခုခံအား (resistances) ကို ေက်ာ္လြန္မွသာ ေရကို လုိအပ္သည့္ေနရာသို့ေရာက္ေအာင္တြန္းပို့နုိင္မည္ၿဖစ္သည္။

piping system ၏ ခုခံအား (resistances) ဆိုသည္မွာ ပိုက္၏ frictional losses မ်ား, valves အတြက္ pressure losses , ႏွင့္ cooling coils အတြက္ pressure drop မ်ား and static head differences in
open systems တုိ့ၿဖစ္သည္။

ပိုက္ system တစ္ခုတြင္းတြင္ ၿဖစ္ေပၚေသာ head lossesႏွင့္ system flow rate တို့၏ ဆက္သြယ္မွဳကို system resistance curve ဟုေခၚသည္။

 

Closed System

 

Open System ဥပမာ

Condenser water (Open System) System တစ္ခု၏ system resistance curve ကို ေအာက္ပါအတိုင္းတည္ေဆာက္ယူနုိင္သည္။

Condenser water ကုိ Cooling Tower မွ စုပ္ယူၿပီး Chillerသုိ့ တြန္းပုိ့ Condenser Pump တစ္လံုး၏ Suction Pressure ကို ပန့္ ရပ္ထားသည့္အခ်ိန္တြင္ 0.4 Bar အၿဖစ္တုိင္းခဲ့သည္။ Suction Pressure (pressuer Gauge) ေနရာမ်ာပင္ ပန့္ေမာင္းေနသည္အခါ 2.5 Bar ၿဖစ္တုိင္း၍ရခဲ့သည္။ Condenser water Rate သည္ Flow Meter မွ 4000 CHM ဟုဖတ္ယူခဲ့သည္။ ထုိ Condenser water (Open System) System ၏ system resistance curve ဆြဲၿပပါ။ Plot လုပ္ပါ။

Answer;

 

Pressure Head သည္ Condenser water Rate ႏွင့္တုိက္ရုိက္အခ်ိဳးက်သည္။

Pressure Head & Square of Condenser water Flow Rate

Pressure Head= C x Square of Condenser water Flow Rate ( C is a constant) ------ (၁)

Delta P = P2 - P1 = 0.4 bar ( ပန့္ ရပ္ထားစဥ္ ) သည္ h2-h1 = 0.4 bar ၿဖစ္သည္။

Delta P = P2 - P1 = 2.5 bar ( ပန့္ေမာင္းေနစဥ္ )

2.5 bar - 0.4 bar = 2.1 bar ၿဖစ္သည္။

Equatioin (1) တြင္ထည့္ေသာ္

2.1 bar = C x 4000( Square of Condenser water Flow Rate)

2.1 = C x (4000X4000)

C = 2.1/(4000X4000) = 0.000000131

ထုိေၾကာင့္ System Resistance Equation မွာ

P = 0.000000131 x Square of Q + 0.4

ထုိ Condenser water Pump ၏ flow rate သည္ 3500CMH (တစ္နာရီလွ်င္ ေရထုထည္ 3500 ကုဗမီတာ) သုိ့ ေလ်ာ့က်ခဲ့လွ်င္ System Pressure မည့္မွ်ၿဖစ္မည္နည္း

P = 0.000000131 x Square of Q + 0.4

P = 0.000000131 x (3500x3500) + 0.4

P = 2.0 bar

Open systems the static pressure difference or independent pressure due to height difference
is added to the system curve. The system curve is parabolic in shape since the pressure losses in the system are proportional to the
square of the flow.

Distribution System ႏွင့္သက္ဆုိင္ေသာ ACMV Lecture မ်ား (2 Lectures)
1 Pumping System Chilled water/ Hot water Distribution Configuration Read
2 Pumping System System Curves Read
   

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