In this study, we investigate a numerical-modeling method uniquely performing analyses of 50 different metal hydrides to find the optimized thermal effect. This paper presents a metal-hydride thermal energy conversion method, which offers an alternative approach to the traditional vapor-compression heat pump associated with conventional heating, ventilation, and air conditioning (HVAC). The authors have developed an innovative heat pump applicable to non-vapor compression-based systems, which are in compliance with low-temperature heat source requirements for operation. The new heat pump has a high-energy savings potential for both heating and cooling that featured two different metal-hydrides, that are distributed inside parallel channels filled with porous media. Thermal energy conversion is developed as a set of successive thermal waves. The numerical-modeling results present the enhanced thermal effect, which is attained in a synchronous motion of the thermal waves and the heat source (or sink) inside paired porous media channels, which accompanies the phase transition in the succession of unit metal-hydride heat pumps. The results present in a form convenient for the prediction of thermal energy efficiency based on the proposed thermal-conversion method in real devices that were experimentally verified in previous work. The non-vapor technologies will be operational with low energy input, which makes it possible to utilize waste heat or low-level heat often found in the environment such as solar radiation, exhaust gas from a heat engine, or high-temperature fuel cell system. View Full-TextKeywords: metal-hydride; heat pump; porous media; thermal wave; temperature; HVAC; non-vapor compression

This journal paper has been published. (June 2020)

This journal paper has been published. (April 2020)

This journal paper has been published. (Dec 2019)

Abstract

In this study, an automated acoustic scanning system was developed for rapid delamination detection on concrete bridge decks. A new ball-chain impact source was designed by combining the advantages of chain-drag (rapid testing speed) and impact-echo tests (analysis in the frequency domain). Conventional steel link chains and the new ball chains were investigated as acoustic excitation sources. Acoustic signals were processed by short-time Fourier transform (STFT) in the frequency range 0.5–5 kHz. Compared with the conventional chain-drag test, the ball-chain results show better signal-to-noise ratio (S/N), higher sensitivity, and repeatability to delamination identification. The automated scanning system includes excitation sources (ball chains), acoustic sensors (microphones), a geographic positioning system (GPS), data acquisition (oscilloscope), and a signal-processing algorithm. Acoustic scanning results are integrated with positioning data to generate an image of the scanned area in a map view. The system was validated in the field on a concrete bridge deck and was found to show satisfactory accuracy, efficiency, and repeatability.

This journal paper has been published. (Feb 2018)

Chain drag testing is commonly used in current practice for bridge deck evaluation due to its low cost and ease of use. However, this method is subjective, and highly depends on the experience of the operators. Ambient noise caused by traffic affects the test speed and accuracy of results. This paper describes a recent research to develop an automated chain drag acoustic scanning system to detect delaminations in concrete structures, including bridge decks. The system consists of an array of chains, a noncontact MEMS microphone sensor array, multi-channel data acquisition device, positioning system, and signal processing schemes. The multi-channel design improves the spatial coverage and resolution of testing. An algorithm for interpreting acoustic signals from the automated chain drag test is developed. This automated system will enable real time visualization of tested areas. Compared to the conventional manual chain drag test, the automated system provides improved accuracy, spatial resolution, repeatability, and practicality.

This journal paper has been published. (Nov 2017)

We describe an approach that utilizes ultrasonic surface wave backscatter measurements to characterize the volume content of relatively small distributed defects (microcrack networks) in concrete. A simplified weak scattering model is used to demonstrate that the scattered wave field projected in the direction of the surface wave propagation is relatively insensitive to scatterers that are smaller than the propagating wavelength, while the scattered field projected in the opposite direction is more sensitive to sub-wavelength scatterers. Distributed microcracks in the concrete serve as the small scatterers that interact with a propagating surface wave. Data from a finite element simulation were used to demonstrate the viability of the proposed approach, and also to optimize a testing configuration to collect data. Simulations were validated through experimental measurements of ultrasonic backscattered surface waves from test samples of concrete constructed with different concentrations of fiber filler (0.0, 0.3 and 0.6%) to mimic increasing microcrack volume density and then samples with actual cracking induced by controlled thermal cycles. A surface wave was induced in the concrete samples by a 50 kHz ultrasonic source operating 10 mm above the surface at an angle of incidence of 9°. Silicon-based miniature MEMS acoustic sensors located a few millimeters above the concrete surface both behind and in front of the sender were used to detect leaky ultrasonic surface waves emanating from concrete. A normalized backscattered energy parameter was calculated from the signals. Statistically significant differences in the normalized backscattered energy were observed between concrete samples with varying levels of simulated and actual cracking damage volume.

This journal paper has been published. (Mar 2017)

Sang-goo Kang joined the SITL.  Welcome new members. (8/2016)

Matthew, Hashim, Yashondhan, and Kapil joined the SITL. 

​Oreoluwa Adedapo and Theodore Jackson  joined  SITL.