A fluid dynamic gauging device for measuring fouling deposit thickness in opaque liquids at elevated temperature and pressure

Abstract

We report proof-of-concept results for a fluid dynamic gauging (FDG) device for measuring the thickness and strength of soft solid fouling layers immersed in an opaque liquid in situ and in real time at elevated pressures and temperatures. The device reported here is configured to make measurements on the inner rod of an annular flow test section but the concept is generic. Data are presented from tests using mineral oil at temperatures and pressures up to 140 °C and 10 bara, respectively. Problems with the prototype hardware prevented testing up to the design limits of 270 ºC and 30 bara. The practical working range of the gauge, i.e. 0.10 < h/d t < 0.25, proved to be unaffected by the pressure and temperature. h is the nozzle-surface clearance and d t the nozzle throat diameter. At smaller h/d t values the pressure drop across the nozzle is very high and this can serve as an alarm for close approach. The range of discharge coefficient, C d, values obtained is sensitive to flow rate when the Reynolds number at the throat, Re t , falls below 20. A useful range of C d values is obtained when Re t > 40. Computational fluid dynamics (CFD) simulations of the gauging flow in these quasi-static experiments (no bulk liquid flow) gave good agreement with experimental data for the cases tested. The CFD results showed that the low Re t regime is related to creeping flow in the nozzle. CFD calculations of the shear stress being imposed on the surface being gauged gave good agreement with an analytical model for flow between parallel discs, indicating that the latter can be used to estimate the maximum shear stress imposed by the gauging flows measurements.

Integrated Fluid Dynamic Gauge for Measuring the Thickness of Soft Solid Layers Immersed in Opaque, Viscous, and/or Non-Newtonian Liquids in Situ

“…C d in the suction mode is lower than that in ejection, which is attributed to differences in eddy formation beneath the nozzle and inside the nozzle. This has been discussed by Chew et al 7 and Ali et al 5 The profiles obtained for the washing-up liquid in Figure 5c show a weak difference between ejection and suction modes at higher h o /d t (and small C d values), but this is in the region beyond that used for FDG measurements.…”

“…C d in the suction mode is lower than that in ejection, which is attributed to differences in eddy formation beneath the nozzle and inside the nozzle. This has been discussed by Chew et al and Ali et al…”

“…The paper is organized as follows: (i) the development of a FDG nozzle with an induction coil is described and calibration tests determining the accuracy of the device are reported for a number of metal substrates and a coated mild steel plate: (ii) since many liquids of potential interest are viscous, opaque, and/or non-Newtonian, application of the iFDG device is demonstrated for a range of these liquids. Previous studies of viscous and non-Newtonian liquids (viscous , and aqueous solutions of carboxymethylcellulose (CMC)Chew et al) employed fixed pressure drop configurations so these tests confirm the potential for FDG applications. (iii) The experimental results are supported by CFD simulations using the open source tool OpenFOAM, which allows the shear stress imposed by the gauging flow on the layer to be calculated.…”

On-line biofilm strength detection in cross-flow membrane filtration systems

“…The FDG technique can measure (in a destructive mode) local strength properties throughout the different layers of deposits (Chew et al 2004a). The ability of the FDG to be operated at elevated temperature and pressure (Ali et al 2013) has gained some interest for use in membrane filtration scenarios, where permeation is involved (Chew et al 2007, Jones et al 2010, Lewis et al 2016. However, these studies 5 were mainly performed using synthetic organics to simulate constant TMP filtration in food industries.…”