An experimental study on the thermal and fouling characteristics in a washable shell and helically coiled heat exchanger by the Wilson plot method

Brazed plate heat exchangers (BPHEX) are broadly used in water source heat pump systems for their large heat transfer capacity. Despite their high heat transfer rate, their high-performance rate tends to decrease sharply, due to fouling and they cannot be cleaned. So the thermal and fouling resistances of washable Shell and helically coiled tube heat exchangers (SCHEX) are designed and experimentally investigated in this study. Heat exchangers with two different tube types are studied and compared with a brazed plate heat exchanger. The overall thermal resistance coefficient of the heat exchangers as determined by using Wilson plots is 38% lower than that of the brazed plate heat exchanger at a Reynolds number of 2460. Fouling test results revealed that regular maintenance and physical cleaning can be used to maintain the thermal resistance of fouling of the washable heat exchanger at a level equal to or less than that of the brazed plate heat exchanger.

     

Single‐Component‐Based White Light Photoluminescence Emission via Selective Photooxidation in an Organic–Polymer Hybrid System

White light‐emitting phenothiazine‐poly(dimethylsiloxane) ( PTZ–PDMS ) composites are formed by a photooxidation reaction. The oxidized PTZ species, i.e., PTZ cation radicals and dication species, are created by electron transfer from the PTZ molecules to PDMS under UV irradiation. In situ UV–vis and electron spin resonance (ESR) spectroscopies are carried out after UV exposure of PTZ–PDMS , and the results provide evidence for the spontaneous ionization of PTZ . The spectral changes indicate the formation of PTZ^?+ (radical cation) and PTZ²⁺ (dication) within the PDMS matrix. Moreover, a combination of PTZ , PTZ^{? +}, and PTZ²⁺ , together with the PDMS matrix, show an unexpected emission of white light with Commission Internationale de L'Eclairage coordinates of 0.34 and 0.32, which are close to those of pure white light. These findings potentially offer a new route and strategy for the development of flexible white light‐emitting materials.     

Phase-change characteristics of nitrogen-doped Ge2Sb2Te5 films during annealing process

The microstructures and electrical properties of nitrogen-doped Ge₂Sb₂Te₅ thermally annealed in an N₂ atmosphere were investigated. The 5.4% nitrogen-doped Ge₂Sb₂Te₅ thin films showed discontinuous changes in resistance with annealing temperature, and corresponding changes in crystal structure. The phase transitions went through three states, amorphous??cubic??hexagonal, after annealing at 200 and 375???C. No chemical compositional change occurred after 400???C annealing. But the 20.1% nitrogen-doped Ge₂Sb₂Te₅ thin films showed continuous changes in microstructure and resistance. According to XRD and TEM analyses, the hexagonal-type Ge?CSb?CTe phase should be directly crystallized from the amorphous phase. Also, the SIMS and XPS spectra indicate that the oxygen in-diffusion and Sb and Te out-diffusion should have occurred simultaneously.     

Traffic Sign Recognition in Harsh Environment Using Attention Based Convolutional Pooling Neural Network

Neural Processing Letters - Convolutional neural networks (CNNs) have achieved significant progress in computer vision systems, helping to efficiently obtain feature information by sliding filters...     

Antioxidant activities of pepsin hydrolysates of water‐ and salt‐soluble protein extracted from pork hams

The objective of this study was to evaluate the antioxidant activities of pepsin‐digested water‐soluble protein (WSP) and salt‐soluble protein (SSP) extracted from pork ham. WSP and SSP were hydrolysed by pepsin for 2–10 h with 2‐h increments. The protein hydrolysates by pepsin were analysed by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis, and reducing power of the hydrolysates was measured. In addition, antioxidant activity of the hydrolysates was determined using linoleic acid emulsion system. Protein bands with molecular weight higher than 7 kDa in WSP and SSP were completely hydrolysed by pepsin after 2 h of digestion time. WSP hydrolysates (WSPH) and SSP hydrolysates (SSPH) had higher ferric reducing power than controls (WSP and SSP without pepsin digestion). Reducing powers of WSPH were higher than those of SSPH, regardless of digestion time. The oxidative activity of linoleic acid was predominantly inhibited by the addition of WSPH and SSPH, especially 0.5% protein hydrolysate. These results indicate that several functional peptides of pork protein digested by pepsin might have antioxidant activity, and thus they may be used as an antioxidant agent in muscle food system.     

A lightweight design approach for an EMU carbody using a material selection method and size optimization

This study proposes a weight reduction design approach for urban transit carbody using a material selection method and size optimization. First, the material selection method, which uses specific stiffness and strength indices to predict the weight reduction rate, is set up when the materials of the under-frame and roof structure are substituted. The CFRP was chosen as the best weight reduction material in terms of the material selection method but was not appropriate for application to an urban transit carbody as a thin panel because of out-of-plane deformation. Therefore, we applied CFRP-AL honeycomb sandwich composites to the under-frame and roof structures, and the size optimization method was subsequently applied to derive a lightweight composite hybrid carbody design. Finally, the proposed approach was applied to an urban transit carbody, i.e., a Korean electrical multiple units carbody made of aluminum extrusion profiles. The weight of the optimized composite hybrid carbody design was 29.0% lighter than that of the original K-EMU. The resulting composite hybrid carbody design satisfied the design guidelines of the Performance test standard for K-EMU according to the corresponding FE simulations.

     

Operational deformations in long-span bridges

Long-span bridges deform quasi-statically and dynamically under a range of operational conditions including wind, traffic and thermal loads, in varying patterns, at different timescales and with different amplitudes. While external loads and internal forces can only rarely be measured, there are well-developed technologies for measuring deformations and their time and space derivatives. Performance data can be checked against design limits and used for validating conceptual and numerical models which can in turn be used to estimate the external loads and internal forces. Changes in performance patterns and load–response relationships can also be used directly as a diagnostic tool, but excessive deformations themselves are also a concern in terms of serviceability. This paper describes application of a range of measurement technologies, focusing on response to extreme loads, for suspension bridges over the River Tamar (with 335 m main span) and Humber (with 1410 m man span). The effects of vehicular, thermal and wind loads on these very different structures are compared, showing that apart from rare extreme traffic and wind loads, temporal and spatial temperature variations dominate quasi-static response. Observations of deformation data and sensor performance for the two bridges are used to highlight limitations and redundancies in the instrumentation.