A theoretical analysis and an experimental study on the efficiency of water jet pumps, where water is used for both the primary and secondary flows, are presented in this paper. The theoretical efficiency equations for such jet pumps were first derived based on one-dimensional formulation, and the theoretical maximum ideal efficiency of 100% was obtained. An experimental rig was designed and constructed to conduct the experimental study in which a commercial water jet pump was used. The effects of different area ratios of nozzle to mixing throat as well as different nozzle cross sections, which include square and triangular nozzles, on the jet pump performance were then investigated. The best nozzle cross section for the jet pump was found to be circular, and for high efficiency, the area ratio was found to be around 0.30.

Efficiency of Jet Pumps

Despite its widespread use in agricultural systems, the Venturi-type ejector presents lower efficiency than that obtained by conventional jet pumps. In this study, low-cost ejectors built from PVC T-junctions, with geometry similar to that of the conventional jet pumps, were developed and evaluated experimentally. The tests were carried out on ejectors with nominal diameters of 25 and 32 mm with area ratios of 0.25, 0.35, and 0.53. For each diameter, a Venturi-type ejector with an area ratio of 0.35 was also employed. The ejectors developed in this research presented efficiency between double and triple of that of the Venturi type, with a maximum of 30.5% being reached with the ejector of 25 mm and area ratio of 0.35. The head-loss coefficients for each component of the ejectors were evaluated by fitting a one-dimensional model. The results showed that the low-cost ejectors developed here presented an operation comparable to that of conventional jet pumps and had a better benefit/cost ratio than the Venturi-type ejectors.

http://www.sciencemadness.org/talk/files.php?pid=26719&aid=337

Performance of Low-Cost Ejectors

Experimental observations for the performance of a jet pump are presented with two different suction configurations and designs. The experimental rig was constructed in such a way it can be used with up feed (negative suction head) or down feed (positive suction head). During experimental programme water is used in both motive and pumped sides. The effect of nozzle-to-throat spacing to nozzle diameter ratio “X”, on the jet pump performance was also tested, with different flow rates and motive pressures, in both cases (up feed and down feed). It was found that the best efficiency for the jet pump is attained with the up feeding configuration.

http://www.wseas.us/e-library/conferences/2006elounda2/papers/538-122.pdf

Effect of design and operational parameters on jet pump performance.

Effect of Reynolds number and slot guidance on passive infrared suppression device

A numerical study has been carried out on a new design of ejector diffuser (infrared suppression device). New design conceptualizes exploiting the shape of the slot openings. A circular arc is provided to guide the entrained fluid at the slot openings. Performance of guided-slot ejector diffuser (GED) has been compared with conventional (non-guided-slot) ejector diffuser (NGED) in terms of local and cumulative mass entrainment ratios, temperature distribution and static pressure recovery. Three slot-area variations are also studied, namely (i) increasing slot-area ranging 1 ≤ A0 ≤ 2.02, ( 0 A is area of 1 st slot) (ii) constant slot-area A0 = 1 and (iii) decreasing slot-area ranging 0.49 ≤ A0 ≤ 1. Simulations have been carried out at fixed Reynolds number Re = 1.3  10. It is observed that GED has 3.5% higher cumulative mass entrainment ratio than NGED. GED forms cold annulus region below ejector diffuser wall from 1 slot onwards which results in wall temperatures being close to ambient temperature (300 K). Higher mass entrainment rate and lower wall temperatures make GED a better infrared suppression device but static pressure recovery is better in NGED (Cp = 0.79) compared to GED (Cp = 0.43). Slot-area study reveals that the performance of increasing slot-area for GED and NGED is superior then constant and decreasing slot-area configurations. The cumulative mass entrainment is 20% higher while static pressure recovery is 45% more for the increasing slot-area GED when compared to the decreasing slot-area GED.

https://jafmonline.net/JournalArchive/download?file_ID=49434&issue_ID=1001

Effect of Slot-Guidance and Slot-Area on Air Entrainment in a Conical Ejector Diffuser for Infrared Suppression

The theoretical maximum ideal pumping efficiency of a water jet pump is 50% at a flow ratio of unity. Pump performance can be predicted theoretically. With a pump designed with theoretically obtained optimum dimensions, a maximum efficiency of 39.8% was achieved. Efficiencies on the order of 42% could be obtained by selecting proper materials to reduce friction losses to a minimum. If a jet pump with fixed nozzle is constructed for maximum efficiency, the area ratio should be between 0.33 to 0.543; for adjustable nozzle pumps, the area ratio should be about 0.205, and the pump should be operated at a nozzle distance of one to two nozzle diameters.

Theory and Performance of Water Jet Pump

A theoretical equation for estimating the mixing loss coefficient is given for mixing of two concentric jets. The equation has been experimentally verified with water as the working fluid. In the experiments, two outer nozzles of semicone angles of 12○ and 24○ were used for different velocity ratios varying from 0.00824 to 0.792. For an area ratio of 0.228 and main nozzle semicone angle of 12○ four nozzle distances of 2.4 cm, 3.4 cm, 4.4 cm, and 7.9 cm were tested. The mixing loss constant reduces with increase in velocity ratio to unity, beyond which it increases with increase in velocity ratio for a given area ratio and angle. The mixing loss constant increases with nozzle angle when all other parameters are constant. For a particular mixing configuration the mixing efficiency increases with nozzle distance and reaches an optimum value; with further increase of nozzle distance it decreases. An optimum efficiency for mixing of the order of 98% was obtained at a velocity ratio of 0.642 for a nozzle semicone angle of 24○ at a nozzle distance of 7.9 cm.

Y. R. Reddy

Papers

Theory and Performance of Water Jet Pump

Mixing of Two Concentric Jets