Experimental Quantification of Local Pressure Loss at a 90° Bend in Low-Pressure Dilute-Phase Pneumatic Conveying of Coarse Particles

Rui Zhu,Chunsheng Luo,Xin Li,Fei Yan

doi:10.1155/2019/6454958

Rui Zhu, Chunsheng Luo + Show 2 more

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https://doi.org/10.1155/2019/6454958

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Abstract

Focusing on the insufficient estimation of the local pressure loss at a 90° horizontal-vertical bend in low-pressure pneumatic conveying of coarse particles, experiments are conducted in a 80 mm inner diameter test bend by using polyethylene particles having an equivalent spherical diameter of 4.00 mm. The influences of the local pressure loss versus the gas flow Reynolds number, the solid-gas ratio, and the bending radius ratio are investigated. Based on the additional pressure theory of Barth, an empirical formula estimating the local pressure loss is obtained using dimensional and nonlinear regression analysis. Summarizing the experiments and literature, the results expound on the local gas flow pressure loss coefficient decreases with increasing Reynolds number, and first decreases and then increases with increasing bending radius ratios from 0.5 to 7. The additional solid flow pressure loss coefficient decreases with the increasing Reynolds number and bending radius ratio in the dilute phase, and linearly increases with increasing solid-gas ratio. Compared with the estimated values with the experimental values, the calculated standard deviation is below 4.11%, indicating that the empirical formula can be used to predict local pressure loss at the bend in the low-pressure dilute-phase pneumatic conveying.

Highlights

To improve the flexibility of the pneumatic conveying system, a bend is usually regarded as an important component in the process route
Cornish and Charity [1] listed all the important parameters of the local pressure loss at a 90° bend for a given pneumatic conveying system and found that the local pressure loss is higher for a short bend curvature radius and linearly increases with the increasing solid-gas ratio
Ghosh and Kalyanaraman [2] studied the local pressure loss in dilute-phase pneumatic conveyance of coarse particles for a horizontal-horizontal bend. e results show that the additional pressure loss coefficient is constant for all conveying velocities and is a linear function of the solid-gas ratio

Summary

Introduction

To improve the flexibility of the pneumatic conveying system, a bend is usually regarded as an important component in the process route. On the basis of Barth’s [7] and Ito’s [12] researches, the semiempirical formula [10] of local additional pressure loss was corrected by the bend exit conditions (e.g., average gas density, velocity, and solid-gas ratio). In this study, based on a low-pressure dilute-phase pneumatic conveying system, the influences of local pressure loss arising from the change of superficial conveying gas velocity, particle mass flow rate, and bending radius ratio are investigated in a horizontal-vertical 90° bend. To provide theoretical support for designing the low-pressure dilute-phase pneumatic conveying systems as conveying the coarse particles, an empirical formula of the local pressure loss is derived using dimensional and nonlinear regression analysis. E particles density ρs 952 kg/m3, and bulk density ρb 563 kg/m3

The Local Pressure Loss

Model of Pressure Loss

Findings

Conclusions