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Cavity-enhanced absorption sensor for carbon monoxide in a rapid compression machine
摘要： A sensor based on cavity-enhanced absorption spectroscopy (CEAS) was implemented for the first time in a rapid compression machine (RCM) for carbon monoxide concentration measurements. The sensor consisted of a pulsed quantum cascade laser (QCL) coupled to a low-finesse cavity in the RCM using an off-axis alignment. The QCL was tuned near 4.89 μm to probe the P(23) ro-vibrational line of CO. The pulsed mode operation resulted in rapid frequency down-chirp (6.52 cm ?1 / μs) within the pulse as well as a high time resolution (10 μs). The combination of rapid frequency down-chirp and off-axis cavity alignment enabled a near complete suppression of the cavity coupling noise. A CEAS gain factor of 133 was demonstrated in experiments, resulting in a much lower noise-equivalent detection limit than a single-pass arrangement. The sensor thus presents many opportunities for measuring CO formation at low temperatures and for studying kinetics using dilute reactive environments; one such application is demonstrated in this work using dilute n-heptane/air mixtures in the RCM. The formation of CO during first-stage ignition of n-heptane was measured over 802–899 K at a nominal pressure of 10 bar. These conditions correspond to the NTC region of n-heptane and such results provide useful metrics to test and compare the predictions of low-temperature heat release by different kinetic models.
关键词： n-heptane,Low-temperature heat release,Cavity-enhanced absorption spectroscopy,Rapid compression machine,Carbon monoxide
更新于2025-09-04 15:30:14
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Removal of Hg <sup>0</sup> from Simulated Flue Gas by Ultraviolet Light/Heat/Persulfate Process in an UV-Impinging Stream Reactor
摘要： Removal of Hg0 from simulated flue gas by ultraviolet light (UV)/heat/ammonium persulfate process in an UV-impinging stream reactor was investigated for the first time. Experiments were conducted to evaluate the effects of several parameters and gas composition on Hg0 removal. Mechanism and kinetics of Hg0 removal were also investigated. The results indicated that Hg0 removal efficiency was increased by increasing UV radiation intensity, activation temperature, persulfate concentration, and solution circulation rate; was decreased by increasing solution pH and SO2 concentration; and was not obviously affected by Hg0 and NO concentrations. Hg0 was oxidized by four pathways: (A) oxidized by SO4?(cid:129) and (cid:129)OH that were produced from UV-light activation of S2O82?. In the four pathways, the “A” pathway plays a major role in the removal of Hg0, and the other pathways “B?D” only play a complementary role. When CS2O82? < 0.06 mol/L or UV radiation intensity < 78 μW/cm2, the Hg0 removal process belongs to a moderate speed reaction. Hg0 removal can be enhanced by simultaneously increasing the mass transfer rate and chemical reaction rate. When CS2O82? ≥ 0.06 mol/L and UV radiation intensity ≥ 78 μW/cm2, the Hg0 removal process belongs to a fast reaction. Hg0 removal can be further enhanced by improving mass transfer rate (e.g., increasing gas?liquid contact area and enhancing turbulence in reactor).
关键词： UV-impinging stream reactor,mechanism,kinetics,Hg0 removal,UV/heat/persulfate process
更新于2025-09-04 15:30:14
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The Monte Carlo Ray-Trace Method in Radiation Heat Transfer and Applied Optics || Fundamentals of Ray Tracing
摘要： A ray is defined as the collection of straight-line path segments followed by an energy bundle from its point of emission to its point of absorption. The definition includes the possibility of intermediate reflection, scattering, refraction, and even diffraction events. Ray tracing involves the application of basic mathematics to the process of identifying the intersection of ray segments with surfaces. Most engineering and science students acquire the required mathematical tools long before they enter university. The current chapter provides a review of the mathematical principles governing ray tracing and the related issues of meshing and indexing.
关键词： Monte Carlo Method,Radiation Heat Transfer,Applied Optics,Mathematical Principles,Ray Tracing
更新于2025-09-04 15:30:14
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The Monte Carlo Ray-Trace Method in Radiation Heat Transfer and Applied Optics || Extension of the MCRT Method to Non-Diffuse, Non-Gray Enclosures
摘要： The assumption of diffuse emission and diffuse-specular reflection in gray enclosures is adequate for many applications encountered in engineering practice. This is especially true in the conceptual and preliminary design stages. However, final design and performance studies often require the use of bidirectional surface optical models restricted to a specified wavelength interval. In this chapter we develop the concept of the band-averaged spectral radiation distribution factor, which is the most general tool available for treating radiant exchange among surfaces, but first we learn through extended examples how to compose and use models to simulate the optical behavior of non-diffuse surfaces.
关键词： Monte Carlo Ray-Trace Method,Non-Gray Enclosures,Radiation Heat Transfer,Applied Optics,Bidirectional Spectral Surfaces,Non-Diffuse
更新于2025-09-04 15:30:14
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The Monte Carlo Ray-Trace Method in Radiation Heat Transfer and Applied Optics || The MCRT Method for Participating Media
摘要： The MCRT Method for Participating Media So far we have only considered energy interactions between rays and surfaces. Two possible outcomes – absorption and reflection – have been identified, and corresponding models have been formulated and used to describe radiation heat transfer among surfaces. When a ray incident to a surface is neither absorbed nor reflected, it is said to be transmitted. Thermal radiation passing through lenses, filters, and the earth’s atmosphere are familiar examples of transmission. This chapter deals with emission, absorption, refraction, and scattering of thermal radiation within a medium through which it is propagating. Such media are said to be “participating.”
关键词： Emission,Thermal Radiation,Refraction,Radiation Heat Transfer,Transmission,Absorption,Reflection,MCRT Method,Scattering,Participating Media
更新于2025-09-04 15:30:14
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Investigation and Performance analysis of Solar Milk Pasteurisation system
摘要： The main aim of this research work is to test and evaluate the performance of solar milk pasteurisation system. To evaluate the performance of solar milk pasteurisation system, a solar hot water system, concentric tube type heat exchanger, the cooling tank has used. To test the solar milk pasteurisation system, three different mass flow rate of hot water like 2 litres/minute, 3 litres/minute and 5 litres/minute and cold milk 0.5 litres/minute, 0.7 litres/minute and 1.0 litre/minute have been used. After the pasteurisation, the obtained milk from the concentric tube type heat exchanger has been tested in the laboratory and achieved satisfactory results. From the series of experiments, it has been found that the hot water flow rate of 5 litres/minute and milk flow rate of 0.5 litres/minute found the optimum for the pasteurisation system.
关键词： concentric tube heat exchanger,Solar Pasteurization,Flat plate collector,Pasteurisation,Milk
更新于2025-09-04 15:30:14
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[Lecture Notes in Mechanical Engineering] Numerical Heat Transfer and Fluid Flow (Select Proceedings of NHTFF 2018) || Combined Influence of Radiation Absorption and Hall Current on MHD Free Convective Heat and Mass Transfer Flow Past a Stretching Sheet
摘要： The present article investigates the combined in?uence of thermal radi- ation, radiation absorption, Soret and Dufour effect, and non-uniform heat source on the steady convective heat and mass transfer ?ow of a viscous incompressible ?uid past a stretching sheet. The non-linear equations governing the ?ow, heat and mass transfer have been solved by using a Runge–Kutta ?fth-order together with shooting technique. The in?uence of Sr/Du, A1, B1 on all ?ow characteristics has been analysed.
关键词： Stretching sheet,Hall current,Cross diffusion,Non-uniform heat source/sink
更新于2025-09-04 15:30:14
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Tuning the Surface Plasmon Resonance of Lanthanum Hexaboride to Absorb Solar Heat: A Review
摘要： While traditional noble metal (Ag, Au, and Cu) nanoparticles are well known for their plasmonic properties, they typically only absorb in the ultraviolet and visible regions. The study of metal hexaborides, lanthanum hexaboride (LaB6) in particular, expands the available absorbance range of these metals well into the near-infrared. As a result, LaB6 has become a material of interest for its energy and heat absorption properties, most notably to those trying to absorb solar heat. Given the growing popularity of LaB6, this review focuses on the advances made in the past decade with respect to controlling the plasmonic properties of LaB6 nanoparticles. This review discusses the fundamental structure of LaB6 and explains how decreasing the nanoparticle size changes the atomic vibrations on the surface and thus the plasmonic absorbance band. We explain how doping LaB6 nanoparticles with lanthanide metals (Y, Sm, and Eu) red-shifts the absorbance band and describe research focusing on the correlation between size dependent and morphological effects on the surface plasmon resonance. This work also describes successes that have been made in dispersing LaB6 nanoparticles for various optical applications, highlighting the most difficult challenges encountered in this field of study.
关键词： heat absorption,nanoparticles,plasmon,LaB6,lanthanum hexaboride
更新于2025-09-04 15:30:14
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High‐Temperature Phase Change Material (PCM) Selection for Concentrating Solar Power Tower Applications
摘要： With current concerns about the environmental impact of greenhouse gas emissions, reducing our reliance on fossil fuels has become an ever-growing necessity. A thermal energy storage system that utilizes phase change materials (PCMs) in the form of molten salts, coupled with a concentrating solar power tower plant, is proposed as an effective means of achieving highly efficient and cost competitive power generation on par with traditional fossil fuel–based power. In this study, a set of five selection criteria are applied to a wide range of salt mixtures to determine the best candidates for use as PCMs. The selection criteria include the salt mixture’s melting temperature, latent heat, thermal conductivity, material safety, and cost. A shortlist of 20 salt candidates is made, and differential scanning calorimetry experiments are performed on them to verify the thermal properties of these candidates. A final list of eight salts is then selected as the best PCMs for use in a working temperature range between 500 and 800 °C.
关键词： salt selection,solar thermal power,thermal energy storage,latent heat,molten salts
更新于2025-09-04 15:30:14
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Regenerated fiber Bragg grating sensing system for ultrasonic detection in a 900 °C environment
摘要： Heat-resistant composites, such as ceramic matrix composites (CMCs) and heat-resistant carbon fiber reinforced plastics (CFRPs), are expected to be used for aircraft engine parts. The development of reliable heat-resistant composite materials requires the use of nondestructive test (NDT) techniques for evaluating the progression of damage during material testing at elevated temperatures. Furthermore, structural health monitoring (SHM) technologies that operate under harsh environments are expected to be realized for monitoring heat-resistant composite structures. To provide potential solutions for the establishment of such technologies, this research developed a heat-resistant ultrasonic sensor based on a regenerated fiber-optic Bragg grating (RFBG). First, we fabricated an RFBG by annealing a normal FBG sensor. Because the RFBG exhibits high heat resistance at temperatures of 1000 °C, the sensor achieved stable ultrasonic detection at an elevated temperature. In addition, we attempted to use a π-phase-shifted FBG (PSFBG) as the seed grating to construct an ultrasonic sensor with enhanced performance. As a result, the R(PS)FBG sensor possessed a very short effective gauge length and achieved a broad frequency response to ultrasonic waves with frequencies greater than 1.5 MHz. The broadband detectability enables the R(PS)FBG sensor to acquire an accurate response to ultrasonic waves. Hence, we believe the regenerated Bragg grating-based ultrasonic sensors can contribute to establishing an effective nondestructive evaluation method for composite materials, thereby enabling a structural health monitoring system for a composite-made structure operating under extreme high-temperature environments.
关键词： structural health monitoring (SHM),ultrasonic detection,nondestructive test (NDT),regenerated fiber-optic Bragg grating (RFBG),high-temperature environment,Heat-resistant composites
更新于2025-09-04 15:30:14