Using ultrasonic wave reflection to measure solution properties

Abstract

Ultrasonic wave reflection coefficients of aqueous solutions were measured using high-impact polystyrene as a buffer material to provide enhanced sensitivity over metal or ceramic buffer materials. The wave reflection values showed linear reduction when the concentration of chemical species in solution was increased, but a distinct relation between concentration and reflection coefficient was obtained for each solute species tested. However, more unified relationships were observed between reflection coefficient and other solution parameters - solution density, acoustic impedance, and P-wave velocity - that were consistent for all solution species. Based on this behavior an expression to compute solution density solely from reflection coefficient is derived, which can be applied to estimate solution density in solutions of unknown solute species and concentration when other measurements, such as wave velocity, are not possible.

Detection methods of fouling in heat exchangers in the food industry

“…Characteristic acoustic impedance Z was used already to determine solution properties, density changes, and to characterise foodstuff (Bamberger & Greenwood, 2004;Chung, Popovics, & Struble, 2010;Greenwood, 2009;Greenwood, Adamson, & Bond Leonard, 2006). Z was also applied in detection of fouling by Wallhäußer, Hussein, Hussein, Hinrichs, and Becker (2011) where an ultrasonic transducer of 2 MHz in pulse-echo mode in a static setup was used together with echo energy and logarithmic decrement (signal loss) of reconstituted skim milk with different protein concentrations.…”

Review of Ultrasonic Wave Reflection Applied to Early-Age Concrete and Cementitious Materials

“…For field deployment and outdoor applications, steel buffer plates have been used [10,13,34]. Polymeric materials such as acrylic glass (also known as polymethyl methacrylate or PMMA under the brand names Plexiglas or Lucite ) and high-impact polystyrene, which have relatively low acoustic impedance, provide higher sensitivity to small changes in acoustic impedance of cemenitious materials, have been used at early stages of hydration, for measurements before and during setting [15,17,[19][20][21]35,36]. For pulse echo testing configurations, where the same transducer is used to send and detect the signal, the buffer should be thick enough to allow the individual pulse in the signal to be well isolated in time.…”

“…For example, the effects of aqueous solution concentration (i.e. cement pore water chemistry) [35] and material flocculation, which drives early stiffening behavior, and particle settlement have been studied [36]. In the latter study, a HIPS polymer buffer was used to measure small changes in the normal incidence P-wave and S-wave reflection coefficients with two materials: a non-hydrating colloidal alumina suspension whose microstructure was manipulated between dispersed and flocculated states by adjusting the pH, and a coarse silica suspension that readily sedimented.…”

“…TG measurements of cement paste involved measuring the evaporable and non-evaporable water contents in the hydrating cement paste at different ages; the porosity was then calculated using the Powers-Brownyard model w/c=0.45 w/c=0.50 TGA,w/c=0. 35 TGA,w/c=0.45 TGA,w/c=0.50…”

Study of the effect of angle errors in conical ultrasonic sensors

“…These rods are usually solid cylinders of known acoustic properties and are placed between the ultrasonic transducer and the sample under study. They act as a delay line separating the useful signals from the loud noise of excitation pulse generation, allowing more precise measurements [1][2][3], and can be used as a reference material for obtaining acoustic impedance of the sample [4][5][6]. Moreover, the presence of the buffer rod avoids contact of the sample under test with the ultrasonic transducer, which is of great interest in the analysis of high temperature or corrosive samples [7][8][9][10][11][12] and also when testing food products, in order to meet the safety and hygiene requirements of the food and beverage industry [13].…”