Mehmet Yasar Gundogdu

A Modification on Ergun's Correlation for Use in Cylindrical Packed Beds With Non-spherical Particles

An experimental study was conducted to determine the pressure drop characteristics of cylindrical packed beds through which turbulent pipe flow was passing. This study was planned to clarify the applicability of the well-known Ergun correlation proposed for beds composed with spherical particles on beds with non-spherical particles. The experimental packed beds were constructed by using two different irregular-shaped and one spherical-shaped packing materials for understanding the effects of particle shape or sphericity, particle size, bed porosity, and bed length to diameter ratio on the pressure drop. The beds were constructed by using zeolite, chickpea and glass bead materials to cover the particle sphericity range of 0.55 ≤ Φ ≤ 1.00. Systematic experiments and the data analysis procedure showed that the well-known Ergun correlation can be applied to all of the experimental beds composed with non-spherical and/or spherical particles with a maximum deviation of ±20%. This deviation can, however, be decreased to a negligible level of ±4% if some simple modifications, including the use of particle Reynolds number, Rep, a new form of particle friction factor, f*p, and some adopted empirical constants in the well-known Ergun correlation, are used.

Discharge Characteristics of Polydisperse Powders through Conical Hoppers. Part 1: Predictions for Fine, Granular, Free Flowing Powders

Discharge characteristics of fine polydisperse granular powders of equal-solid density and near-spherical particle shape through a conical hopper were investigated by measuring solid discharge rates of powders. Effects of orifice size of hopper and size distribution of powders on discharge rate were determined by means of experiments conducted for six different sizes of hopper orifice and three different powder types under gravity flow conditions. A new effective mean diameter characterizing polydisperse powders is first introduced and determined from the particle size versus weight fraction distribution of a powder as the size corresponding to 50% cumulative weight fraction. This effective mean diameter was efficiently used in two modified forms of the Beverloo equation to predict discharge rates of polydisperse powders through hopper orifices.

An interactive data acquisition and control system coupled on a pulsatile pipe flow test rig

A test rig to be used for time-dependent static pressure and velocity distribution measurements in a pulsatile pipe flow with laminar, transitional and turbulent regimes was initially designed and constructed. An interactive data acquisition and control system including data storage acquisition, and processing of the measured data together with interactive control of corresponding test rig components was designed and operated on the constructed test rig. A high speed computer aided processing of time-dependent pulsatile flow measurements was thus achieved sensitively by means of this interactive system. The systematic experiments on velocity and frictional loss of pulsatile pipe flow could be carried out easily on the test rig in a short time period. The operation principles and advantages of the system are discussed here in sufficient detail.

Discharge Regimes of Polydisperse Powders through Conical Hoppers under Positive Flow Conditions

Discharge characteristics of polydisperse powders through a conical hopper were experimentally investigated by observing the solids discharge regimes under different positive pressure differences (i.e., ΔP > 0) and also measuring the corresponding solids discharge rates. The observations and measurements were systematically conducted at least four diameters of hopper orifice (2.5 mm ≤ Do ≤ 30.0 mm) under five positive ΔP values (0 Pa ≤ ΔP ≤ 1405 Pa) for the test powders: river sand, zeolite, fertilizer, and sawdust. Effects of positive ΔP on both discharge regime and solids discharge rate are first predicted for different orifice diameters and test powders in this study. One of the novel results on the discharge regime is that increase of positive ΔP value up to a critical value conserves or successively stabilizes the discharge regime observed when ΔP = 0 (i.e., for gravity flow condition) through the same hopper. However, the additional increase of positive ΔP over this critical value destabilizes the discharge regime, as in conformity with the effect of increase in negative ΔP cited in the literature.