Comparison of Efficiencies of Pipe- and Box-Type Airlift Pumps

Abstract

Air lift pumps, rectangular box design (box type airlift) and circular pipe (pipe type airlift), performance was tested with different diffuser types and different submergence ratios. Three different diffusers: Cone diffuser, Snap cap diffuser and uni-hose diffuser, were used at four submergence ratios: 100%, 90%, 80% and 70% with different air amounts from diffuser (from 100 L/min up to 900 L/min). Polynomial regression equations of the relationship between amount of water flow and air flow in the box type airlift pump under 500 cm2 surface area and 100% submergence are: y = 6E-05x2 + 1.4193x + 270.9 (R² = 0.9656) in Cone diffuser, y = -0.0003x2 + 1.9208x + 284.96 (R² = 0.9879) in Snap cap diffuser, and y = -0.0041x2 + 6.5433x - 346.31 (R² = 0.9981) in uni-hose diffuser. Polynomial regression equations for the pipe type airlift pump under 558 cm2 surface area at 100% submergence are: y = -0.0014x2 + 2.0973x + 68.123 (R² = 0.9621) in Cone diffuser, and y = -0.0005x2 + 1.6769x + 12.922 (R² = 0.9949) in Snap cap diffuser. Uni-hose diffuser showed the highest resistance rate among the diffusers. Average air resistance ratios of Cone diffuser, Snap cap diffuser, and uni-hose diffuser under the condition of actual ranges of air amount outflow from diffusers of 100 to 600 L/min were 30.8%, 21.4%, and 60.5%, respectively. When amount of air from the diffusers, Cone diffuser, Snap cap diffuser and uni-hose diffuser, with the ranges of 100 to 600 L/min the average amount of air injected from those diffusers were 483.3, 431.6, and 828.3 L/min, respectively. Average amount of water flow accomplished by Cone diffuser, Snap cap diffuser, and uni-hose diffuser under the condition of actual air amount from diffusers of 100 to 600 L/min in the box type airlift under 500 cm2 surface area and 100% submergence were 782.7, 897.7, and 1,322.6 L/min, respectively. Average amount of water flow accomplished by Cone diffuser, and Snap cap diffuser under the condition of actual air amount from diffusers ranged 100 to 600 L/min in the pipe type airlift under 558 cm2 surface area and 100% submergence were 593.5 and 519.9 L/min, respectively. Amount of water flow for box type airlift with 500 cm2 surface area was significantly higher than that of pipe type airlift with 558 cm2 surface area (as a three combined pipe airlifts) under 100% and 90% submergence in all diffusers. However, pipe type airlift showed better results than box type at low submergence ratios, 70% and 80% submergence. Box type airlift with uni-hose diffuser showed the highest water flow comparing with other diffusers in box type and in pipe type airlifts. The highest water flow discharges recorded were 2,121.9 and 1,090.6 L/min at 100% and 90% submergence, respectively with uni-hose diffuser in the box type airlift with 600 L/min of air.