Pump energy and efficiency

Pump energy and efficiency

A：pump energy loss in the three aspects
Pump is a kind of energy conversion machine, the energy conversion process inevitably accompanied by the loss of energy, and a measure of the efficiency is the conversion, how to improve the efficiency of the pump, reduce energy loss?Must be understood within the pump energy loss.Inside the pump energy loss mainly includes the following three aspects:
1, the mechanical loss
Mainly liquid and the external surface of the plate before and after impeller and the pump cavity of the friction loss (also called disc loss).
Disc loss proportion is larger, and even reach 30% of effective power.Disk damage and speed tests showed that the direct ratio three times, and the direct ratio five times of impeller diameter.Therefore, the larger the impeller diameter, the loss is, the greater the disc.Although disc and speed of three times of the direct loss, but under the given head, with the improvement of speed, accordingly to reduce the impeller diameter (can be thought of double pump speed, reduce by half the impeller diameter), loss of disc into five power proportion to drop, so, with the increase of rotational speed, disk loss does not increase, instead of down, this is one of the reasons for the development of high speed pump.
2, volume loss
Part of the liquid by the impeller impeller sealing ring clearance leakage returned to the impeller can not effectively use imported, formation damage.As a result, the clearance between the sealing ring should be as small as possible, but due to machining and assembly, the gap is too small may be forming eccentric wear or jammed, national standards for various types of pump clearance made specific provisions.
3, hydraulic loss
Pump flow section (from import to export) liquid fluid must have a velocity and direction change caused by the loss, the two parts is the hydraulic loss.To reduce this part of the loss, in addition to improve the flow components of finish, try choosing excellent hydraulic model.

B：the pump efficiency formula parsing
What is the efficiency of the pump?The formula?
A: the effective power of the pump and the ratio of the shaft power.Eta = Pe/P pump power usually refers to the input power, the power of the prime mover to the pump shaft, so it is also called shaft power, expressed in P.
Effective power: pump lift and the product of the mass flow rate and the acceleration of gravity.
Pe = QH (W) or Pe = gamma rho g QH / 1000 (KW)
Rho, pump the liquid density (kg/m3)
Gamma: pump liquid severe gamma rho = g (N/m3)
G: gravity acceleration (m/s)
Mass flow Qm = rho Q (t/h or kg/s)