Unsteady heat transfer properties of spray falling over a horizontal tube in an oily sewage source heat pump

Wave characteristics of the falling liquid film in the development region at high Reynolds numbers

Measurement of fastening force using dry-coupled ultrasonic waves.

This work presents a low insertion loss air-coupled ultrasonic transducer with a parallel laminated piezoelectric structure. The relevant parameters of this structure are theoretically analyzed. For overcoming the enormous acoustic impedance mismatch between the piezoelectric material and air, a 1–3 connectivity piezoelectric composite, and a stack of two low acoustic impedance matching layers are adopted. The experimental results show that the insertion loss of −17.5 dB is obtained under the pitch-catch mode with the length of the air column of 50 mm by selecting a suitable air-coupled ultrasonic transducer combination. The insertion loss improvement is 3.8 dB compared with a monolayer piezoelectric structure with an identical active area.

Low insertion loss air-coupled ultrasonic transducer with parallel laminated piezoelectric structure

Interferometric analysis of flow around a horizontal tube falling film evaporator for MED systems

Falling film thickness measurement using air-coupled ultrasonic transducer

This study aims to investigate the bond quality of aluminum–epoxy–aluminum tri-layer bonds using nonlinear ultrasonics. An experimental methodology was developed in which the tri-layer bonds with different interface qualities were inspected using the fundamental shear horizontal guided wave mode (SH0). An in-house developed magnetostrictive transducer assembly was used to excite the SH0 wave mode in the bonded samples. The harmonic generation of the SH0 wave mode was confirmed using dispersion curves overlaid on short-time Fourier transform (STFT) and frequency–wavenumber plots. The sensitivity of the third harmonics to the interface quality of the bonds was estimated using a relative nonlinearity parameter ([Formula: see text]). In this work, the mean [Formula: see text] for the non-sandblasted bond is found to be 70% more than that of the sandblasted sample, which shows the sensitivity of the third-harmonic generation to the interfacial degradation. The analysis shows that the technique can be implemented for a quick and early inspection of the bonded samples for their bond quality.

Akhil Balachandran

Papers

Falling film thickness measurement using air-coupled ultrasonic transducer

Quality assessment of adhesive joints using third harmonics of fundamental shear horizontal wave mode