Numerical studies for effect of geometrical parameters on water jet pump performance via entropy generation analysis

Muhammad Penta Helios,Wanchai Asvapoositkul

doi:10.15282/15.3.2021.10.0654

Abstract

This paper presented an implementation of entropy generation analysis in the main flow field of a water jet pump via the CFD method. This study aimed to identify the inefficient location of energy conversion and to analyse entropy generation sources in each region of the water jet pump. The 2D-axisymmetric model and realisable k-ε (RKE) turbulence model at steady-state conditions were performed to validate jet pump performance and to assess the entropy generation. Likewise, the effects of the projection ratio and throat-aspect ratio as independent parameters were investigated. As a result, the throat is the most inefficient part due to the high total entropy generation rate, following by diffuser part. Also, the entropy generation rate was assessed dominant than viscous dissipation due to the turbulent dissipation, which was caused by a turbulent shear stress layer of mixing the streams. In conclusion, the projection ratio influenced the growth of the shear stress layer as well as the entropy generation. Further, the throat-aspect ratio affected the distribution of entropy generation in the throat section. An appropriate combination of both parameters has an impact on the jet pump performance improvements reducing the entropy generation rate in the future.

Highlights

IntroductionA water jet pump is a kind of subsonic ejector type, of which liquid is used as both motive (driving) and secondary (driven) flow
A water jet pump is a kind of subsonic ejector type, of which liquid is used as both motive and secondary flow
The water jet pump geometry is similar to Figure 1 with L∗t = 7, and L∗x = 1

Summary

Introduction

A water jet pump is a kind of subsonic ejector type, of which liquid is used as both motive (driving) and secondary (driven) flow. It utilises the force of a high-pressure fluid stream to boost the pressure. The main features of the jet pump are simplicity, reliability, durability, relatively low cost, and absence of moving parts. It has relatively low efficiency caused by irreversibilities, e.g., friction, jet flow, fluid stream mixing, recirculation, and pressure recovery[1, 2]. The system consists of the inlet for primary (motive fluid), inlet for secondary fluid, suction chamber, converging section (mixing chamber), throat, diverging section (diffuser), and discharge pipe (see Figure1)

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Results

Conclusion