Transmissivity and Absorption of Fused Quartz Between 022 μ and 35 μ from Room Temperature to 1500°C

Abstract. Flow tube reactors are widely employed to study gas-phase atmospheric chemistry and secondary organic aerosol (SOA) formation. The development of a new laminar-flow tube reactor, the Caltech Photooxidation Flow Tube (CPOT), intended for the study of gas-phase atmospheric chemistry and SOA formation, is reported here. The present work addresses the reactor design based on fluid dynamical characterization and the fundamental behavior of vapor molecules and particles in the reactor. The design of the inlet to the reactor, based on computational fluid dynamics (CFD) simulations, comprises a static mixer and a conical diffuser to facilitate development of a characteristic laminar flow profile. To assess the extent to which the actual performance adheres to the theoretical CFD model, residence time distribution (RTD) experiments are reported with vapor molecules (O 3 ) and submicrometer ammonium sulfate particles. As confirmed by the CFD prediction, the presence of a slight deviation from strictly isothermal conditions leads to secondary flows in the reactor that produce deviations from the ideal parabolic laminar flow. The characterization experiments, in conjunction with theory, provide a basis for interpretation of atmospheric chemistry and SOA studies to follow. A 1-D photochemical model within an axially dispersed plug flow reactor (AD-PFR) framework is formulated to evaluate the oxidation level in the reactor. The simulation indicates that the OH concentration is uniform along the reactor, and an OH exposure (OH exp ) ranging from ∼ 10 9 to ∼ 10 12 molecules cm −3 s can be achieved from photolysis of H 2 O 2 . A method to calculate OH exp with a consideration for the axial dispersion in the present photochemical system is developed.

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“…Figure 2. Photon fluxes inside the reactor, as well as the transmittance of water and fused quartz (Beder et al, 1971). …”

Section: Temperature Control In the Reaction Sectionmentioning

confidence: 99%

The Caltech Photooxidation Flow Tube reactor: design, fluid dynamics and characterization

et al. 2017

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“…In order to test the potential of the CNP as a method of fabrication of a 2D slab silicon photonic crystal TM polarizer, a hybrid mask mold with both a nanoscale imprinting mold and a micron-scale Cr photomask layer was made. Quartz was chosen as an imprinting mold material, since quartz substrate is known to be transparent over the 200~400 nm range of UV light and very rigid [17]. The multi-scale patterns of the photonic crystal device can be transferred to the silicon-on-insulator (SOI) sample substrate by UV exposure and imprinting, as shown in Figure 3. …”

Section: µMmentioning

confidence: 99%

One-Step Combined-Nanolithography-and-Photolithography for a 2D Photonic Crystal TM Polarizer

et al. 2014

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Photonic crystals have been widely investigated since they have great potential to manipulate the flow of light in an ultra-compact-scale and enable numerous innovative applications. 2D slab photonic crystals for the telecommunication C band at around 1550 nm have multi-scale structures that are typically micron-scale waveguides and deep sub-micron-scale air hole arrays. Several steps of nanolithography and photolithography are usually used for the fabrication of multi-scale photonic crystals. In this work, we report a one-step lithography process to pattern both micron and deep sub-micron features simultaneously for the 2D slab photonic crystal using combined-nanoimprint-andphotolithography. As a demonstrator, a 2D silicon photonic crystal transverse magnetic (TM) polarizer was fabricated, and the operation was successfully demonstrated.

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“…Where appropriate I have obtained copyright permission from the copyright holder to reproduce material in this thesis. 9 Measured open circuit voltages (V oc ), short circuit currents (I sc ), and estimated power output (P max ) at the PV's maximum power point (MPP) using a known fill factor (FF) value of 0.7 [198] 6.10 Transmittance of quartz [190] and silicon (slightly doped, concentration of 10 16 cm −1 ) [197] at elevated temperatures (a) and blackbody spectral emissive power as a function of temperature (b), the dashed lines indicate the wavelength of 3.5 µm where quartz's transmittance is dramatically decreased at elevated temperatures, the external quantum efficiency of GaSb PV cells [198] A.7 A five-cell stencil for the 5th-order WENO reconstruction as described in original article [208] With the rapid development of nano/micro-manufacturing technologies, the miniaturisation of a variety of electronic and mechanical devices for the next generation has been drastically accelerated, for applications such as wireless equipment, micro-sensors and actuators, micro-space vehicles, and small-scale biomedical devices. However, the development of small-scale energy systems for powering those devices has fallen behind, especially when energy density and mass/volume become important criteria of evaluating the performance of the power system [1][2][3][4][5].…”

Section: Declaration By Authormentioning

confidence: 99%

“…Second, since the silicon wafer is partially transmissive in the PV convertible band (although the transmittance is decreased at elevated temperatures, as shown in Figure 6.10), radiation from the porous foams inside the combustor serves as a secondary mechanism for the TPV power output. [190] and silicon (slightly doped, concentration of 10 16 cm −1 ) [197] at elevated temperatures (a) and blackbody spectral emissive power as a function of temperature (b), the dashed lines indicate the wavelength of 3.5 µm where quartz's transmittance is dramatically decreased at elevated temperatures, the external quantum efficiency of GaSb PV cells [198] is also shown.…”

Section: Tpv Performancementioning

confidence: 99%

“…Quartz, a thermally robust material, was extensively used in past micro/mesoscale combustion studies [38,39,54,63,127,145]. Moreover, quartz is able to provide optical transmission from near-ultraviolet to mid-infrared while filtering the radiation in the far-infrared region [190], and therefore, draws the authors' interests to A novel mesoscale combustion-based thermophotovoltaic (TPV) system use it as a simple band-pass filter to improve the TPV system performance. Li et al [38,39] utilised the visually transparent property of the quartz material to allow the combination of both the visible radiation from high luminosity flames and the near-infrared radiation from the heated emitter inside a quartz-tube combustor to be emitted.…”

Section: Introductionmentioning

confidence: 99%

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Micro/mesoscale combustion based portable power generating system

Kang¹

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Micro/mesoscale combustion-driven power generation is a promising alternative to replace traditional batteries for powering small scale electronics owing to its much higher energy densities. However, the considerable heat losses from the combustor walls due to the dramatically increased surface-tovolume ratio, as well as the short flow residence time at small scales pose a technical challenge in stabilising the flame inside the micro/mesoscale combustor. On the other hand, the significantly enhanced flame-wall thermal coupling at small scales can also lead to some unique flame characteristics.Recently, solid state power conversion of the heat released in the micro/mesoscale combustor such as thermoelectric (TE) and thermophotovoltaic (TPV) has been favoured over traditional power conversion methods such as micro-turbines. This is due to the excessive mechanical and viscous losses that rotating machinery suffers from upon miniaturisation.One of the main aims of this thesis is to perform numerical simulations to investigate the fundamental aspects of micro/mesoscale combustion, such as micro-flame behaviours of propagation and stabilisation, the conditions under which flame dynamics occur and the choices that suppress them. A set of modelling techniques that gives guidelines and practices for performing the time-accurate micro/mesoscale combustion simulations has been developed through investigation. Knowledge on standard and well-accepted numerical methods in literature are collected in a cohesive document. The less well-established modelling choices have been thoroughly evaluated and discussed.Using the developed numerical models, the effects of hydrogen and carbon monoxide addition on premixed methane/air flame dynamics is investigated. Results show that the flame instabilities which exist in pure methane/air flames could be effectively suppressed via a small amount of additives. Deep understanding of the underlying physics and chemistry has been gained. The effects of wall temperature profiles on the simulated micro-flame behaviours are also studied. The role of the combustion heat release and the gas-solid heat transfer in determining the micro-flame propagation speed is identified.Experimental works are also carried out, towards a full system demonstration for micro-power generation. The focus is placed on the "wall thermal engineering" on the improvement of the combustor performance and power output. The thermally-orthotropic pyrolytic graphite for the combustor wall material is explored. Compared to an isotropic material of stainless steel, a widened flame stability limit with pyrolytic graphite is demonstrated. Moreover, a uniform and moderate temperature distribution over the combustor surface is achieved, which is favourable for thermoelectric power conversion applications. Meanwhile, a novel, compact mesoscale thermophotovoltaic power generating system using a combination of porous media combustion and a simple band-pass filtering method is developed. The use of the porous media effectively enh...

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Transmissivity and Absorption of Fused Quartz Between 022 μ and 35 μ from Room Temperature to 1500°C

Cited by 85 publications

References 3 publications

The Caltech Photooxidation Flow Tube reactor: design, fluid dynamics and characterization

The Caltech Photooxidation Flow Tube reactor: design, fluid dynamics and characterization

One-Step Combined-Nanolithography-and-Photolithography for a 2D Photonic Crystal TM Polarizer

Micro/mesoscale combustion based portable power generating system

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