Pumping depth, optimum

The use of traditional rod and piston pumps continues at many LNAPL recovery locations, particularly at refineries and distribution terminals. These units are usually powered by single-speed electric motors and have adjustable stroke lengths to control the pumping rate. When installed with the intakes set at the optimum pumping depth, they function fairly well. The primary advantage of rod and piston pumps is that the smooth slow stroke rate can pump mixtures of product and water without creating a significant emulsion. 

This equation was derived by assuming a zero pressure gradient in the metering section and by using the Newtonian throughput-pressure relationship, Eq. 7.198. The optimum channel depth in the pump section Hp can be obtained by setting ... 

This results in the following expression for the optimum channel depth in the pump section ... 

The ratio of depth in the pump section to depth in the metering section is often referred to as pump ratio Xp. The optimum pump ratio H according to Eq. 8.83 is only a function of the power law index this is shown in Eig. 8.38. 

The DEER modulation depth is proportional to the fraction of species, whose magnetization is inverted by the pump pulse. This can be increased by a larger excitation bandwidth of the pump pulse and by the selection of the pump frequency at the optimum position in the corresponding EPR spectrum. Thus, for optimal sensitivity, the Gd(iii)-nitroxide DEER is usually set up with the detection frequency at the maximum of the Gd(iii) spectrum and pump frequency at the maximum of the nitr-oxide spectrum. This setting corresponds to a pump-detection frequency... 

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