[PD] 問﹕講下揀一個水泵有啲乜要考慮？

答﹕

1. Pump Curve from catalogue, pump curve 會顯示個pump既Pressure Head & Flow Rate, 個Pressure Head 去到極限，個Flow Rate就會係零。當然我地都要用條System Curve碰埋去，睇下點Match Design Point

2. 睇下用幾多Power

3. 睇下個Efficiency Curve點optimize

4. 睇下個Net Positive Suction Head NPSH夠唔夠，有分NPSHA & NPSHR (A for Available, R for Requried) 

    NPSHA - 個泵Inlet嗰點既Pressure

    NPSHR - 個泵需要既Pressure，呢個Pressure要係足以被免被Cavitation破壞

    NPSHA > NPSHR + 0.6m

根據ASHRAE Handbook 2016 - HVAC Systems and Equipment Chapter 44 Centrifugal Pumps, NPSHA大唔得過NPSHR的話，就會有cavitation, noise, 為免麻煩做設計時最好大得過；尤其係cooling tower呢類open system更加要注意。

5. 仲有其他換impeller size, 改泵速，用VSD等以致條pump curve 改變可以參考下

鳴謝﹕紅豆

(Source: https://www.youtube.com/watch?v=U8iWNaDuUek)