Bopit Bubphachot

Energy and exergy analysis of a double–pass thermoelectric solar air collector

Analysis of energy and exergy has been performed for a double–pass thermoelectric (TE) solar air collector. The incident solar radiation heats up the absorber plate so that a temperature difference is created between the thermoelectric modules that generate a direct current. Only a small part of the absorbed solar radiation is converted to electricity, while the rest increases the temperature of the absorber plate. The ambient air flows through the heat sink located in the lower channel to gain heat. The heated air then flows to the upper channel where it receives additional heating from the absorber plate. At a temperature difference of 22.8°C, the unit achieved a power output of 2.13 W and the conversion efficiency of 6.17%. The exergy efficiency varies from a minimum of 7.4% to a maximum of 8.4%, respectively.

Stress and Strain Locus of Perforated Plate in Inelastic Deformation—Strain-Controlled Loading Case

Plastic strain of structures having stress concentration is estimated by using the simplified method or the finite element elastic solutions. As the simplified methods used in codes and standards, we can cite Neuber’s formula in the work by American Society of Mechanical Engineers (1995, “Boiler and Pressure Vessel Code,” ASME-Code, Section 3, Division 1, Subsection NH) and by Neuber (1961, “Theory of Stress Concentration for Shear Strained Prismatic Bodies With Arbitrary Nonlinear Stress-Strain Law,” ASME, J. Appl. Mech., 28 , pp.544–550) and elastic follow-up procedure in the work by Japan Society of Mechanical Engineers [2005, “Rules on Design and Construction for Nuclear Power Plants, 2005, Division 2: Fast Breeder Reactor” (in Japanese)]. Also, we will cite stress redistribution locus (SRL) method recently proposed as the other simplified method in the work by Shimakawa [2002, “Creep-Fatigue Life Evaluation Based on Stress Redistribution Locus (SRL) Method,” JPVRC Symposium 2002, JPVRC/EPERC/JPVRC Joint Workshop sponsored by JPVRC, Tokyo, Japan, pp. 87–95] ad by High Pressure Institute of Japan [2005, “Creep-Fatigue Life Evaluation Scheme for Ferritic Component at Elevated Temperature,” HPIS C 107 TR 2005 (in Japanese)]. In the present paper, inelastic finite element analysis of perforated plate, whose stress concentration is about 2.2–2.5, is carried out, and stress and strain locus in inelastic range by the detailed finite element solutions is investigated to compare accuracy of the simplified methods. As strain-controlled loading conditions, monotonic loading, cyclic loading, and cyclic loading having hold time in tension under strain-controlled loading are assumed. The inelastic strain affects significantly life evaluation of fatigue and creep-fatigue failure modes, and the stress and strain locus is discussed from the detailed inelastic finite element solutions.

Optimization and Prediction of Ultimate Tensile Strength in Metal Active Gas Welding

We investigated the effect of welding parameters on ultimate tensile strength of structural steel, ST37-2, welded by Metal Active Gas welding. A fractional factorial design was used for determining the significance of six parameters: wire feed rate, welding voltage, welding speed, travel angle, tip-to-work distance, and shielded gas flow rate. A regression model to predict ultimate tensile strength was developed. Finally, we verified optimization of the process parameters experimentally. We achieved an optimum tensile strength (558 MPa) and wire feed rate, 19 m/min, had the greatest effect, followed by tip-to-work distance, 7 mm, welding speed, 200 mm/min, welding voltage, 30 V, and travel angle, 60°. Shield gas flow rate, 10 L/min, was slightly better but had little effect in the 10–20 L/min range. Tests showed that our regression model was able to predict the ultimate tensile strength within 4%.

Corrosion mechanism in a closed-loop oscillating heat-pipe with check valves (CLOHP/CV)

Purpose – The purpose of this paper was to study the parameters affecting corrosion of the closed-loop oscillating heat-pipe with check valves (CLOHP/CV) in a system in clear that will be basic data to be used in future research. The majority of research focuses on the inner surface corrosion heat-pipe systems. The CLOHP/CV is commonly favored in cooling electronic devices, etc. Despite these common applications, limited reliable experimental research findings are available on the operation of the CLOHP/CV. Because of these reasons, the lack of detailed data, working fluids effect, working temperatures and duration of testing of the CLOHP/CV, this study focuses on determining the actual inner surface corrosion. Design/methodology/approach – Seven types of copper tubes used in the CLOHP/CV set were sectioned to observe their inner surfaces. Seven different specimens with tube corrosion were examined by a visual inspection, scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). T...

Crack Initiation Process for Semicircular Notched Plate in Fatigue Test at Elevated Temperature

Crack initiation and propagation process of fatigue test in semicircular notched plates at elevated temperature were conducted under strain-controlled condition in order to study the crack initiation/propagation/coalescence process and load decrease in structure having stress concentration. Test specimens made of SUS304 stainless steel are tested at 550°C and the geometry of the semicircular notched plate specimens are changed by diameter size of the circular notch in both of single-notched specimens and double-notched specimens. Photographs in all cycles were recorded to investigate crack initiation/propagation/coalescence as a function of number of applied cycle. The typical crack process is predicted by using the simplified method, namely stress redistribution locus method as well as Neubers formula.

Stress and Strain Locus of Perforated Plate in Inelastic Deformation: Strain-Controlled Loading Case

Plastic strain of structures having stress concentration is estimated by using the simplified method or the finite element elastic solutions. As the simplified methods used in codes and standards, we can cite Neuber’s formula and elastic follow-up procedure. Also we will cite stress redistribution locus (abbreviated as SRL) method recently proposed as the other simplified method. In the present paper, inelastic finite element analysis of perforated plate, whose stress concentration is about 2.2∼2.5, is carried out, and stress and strain locus in inelastic range by the detailed finite element solutions is investigated to compare accuracy of the simplified methods. As strain-controlled loading conditions, monotonic loading, cyclic loading and cyclic loading having hold time in tension are assumed. The inelastic strain affects significantly life evaluation of fatigue and creep-fatigue, and the stress and strain locus is discussed from the detailed inelastic finite element solutions.Copyright

Corrosion behavior in heat pipe

The aim of this study was to perform life testing and determine the effect of working fluid on the corrosion of a heat pipe with a sintered wick. The heat pipe was made from a copper tube. The inner heat pipe was filled with 99.97% pure copper powder as a dendritic for the sintering process. The heat pipe had an outer diameter of 6 mm with a length of 200 mm, and distilled water and ethanol were the working fluids. The operating temperature at the evaporator was 125°C. The analysis consisted of using a scanning electron microscope, energy dispersive X-ray spectrometry and atomic absorption spectroscopy. The results of the scanning electron microscope and energy dispersive X-ray spectrometry analysis showed that the corrosion of the heat pipe was uniform. The result of the atomic absorption spectroscopy indicated that the concentration of the copper in the ethanol as the working fluid was greater than in the distilled water as the working fluid, and the highest concentration of copper particles in the ethanol was 22.7499 ppm or 0.0409 mg after testing for 3000 h. The concentration of copper was higher when the length of the life test increased due to corrosion of the heat pipe.