Room Temperature Chamber Research Articles

Numerical Investigation on Heat Transfer Characteristics in Electronic Cavity of Downhole Measurement-While-Drilling System

Abstract In recent years, the number of deep wells and ultra-deep wells is increasing gradually, and the bottom hole temperature of many wells reaches more than 200 °C, which puts forward higher requirement for the downhole measurement-while-drilling system. In this paper, a new active cooling method is proposed to protect electronic components in the electronic cavity from high temperature. The circuit board is cooled by direct contact with the cold end of a custom split-Stirling refrigerator. According to the different heat loads, the electronic components can operate in the proper temperature range by adjusting the piston motion frequency and inflation pressure. At the same time, the electronic cavity is filled with thermal insulation material to induce heat leakage from the environment. The thermal resistance of solid insulation material, argon, and vacuum is studied, and the required effective cooling power is determined. When the thermal insulation material is vacuum, which is the best resistance medium when compared with solid insulation material and argon according to the research results, the effects of the structure size of circuit board and electronic cavity, material property and operational environment on the required effective cooling power and maximum temperature on the room temperature chamber wall of the split-Stirling refrigerator are discussed.

Effect of oxygen concentration on combustion behavior of single coal pellets from three different ranks in a concentrating photothermal reactor

Comparative combustion studies were performed in a concentrating photothermal platform (room temperature chamber type experimental bench with less volumetric reactions) on coal pellets (>6mm) from three different ranks: bituminous coal, sub-bituminous coal, and lignite. The combustion of single coal pellet in 21 ~ 50% oxygen concentration was observed with IR pyrometry and high-speed cinematography to obtain temperature–time–size histories. Based on the combined mass measurement and gaseous product analysis, a comprehensive understanding of the effects of oxygen concentration on single coal pellet combustion behaviours was developed. Distinctive three-stage processes were proposed with characteristical temperature and cinematography variations. No obvious flame duration was detected in 21% or 30% O2 while transient but luminous flames were clearly observed in 40% and 50% O2 and formed notable temperature peaks in the second stage during combustion of all the three ranks coal pellets. Volume and density both changed non-linearly during combustion and such processes were accelerated with the increase of oxygen concentration. High concentrations of CO and CH4 were detected due to the suppression of volumetric reactions. CO accounted for about 9.3% of the gaseous products and consistently exhibited two peaks with the first peak independent from oxygen concentration. Three-stage combustion process was further validated by CO2/CO ratio and the effective reaction orders of oxygen concentration were 1.91 (bituminous coal), 1.81 (sub-bituminous coal) and 1.26 (lignite).

Combustion behavior of large size coal over a wide range of heating rates in a concentrating photothermal reactor

Combustion behaviors of large size coal pellets were studied in a novel room temperature chamber type concentrating photothermal apparatus. 4 heating rates of 4.0 °C/s, 15.1 °C/s, 52.4 °C/s and 69.4 °C/s were realized by adjusting the voltage-up rates of the heating lamps. The temperature, image, gas emission, and mass loss were synchronously detected and the reliabilities of data were strictly verified. Coal pellets presented “heterogeneous” ignition mechanism at slow (4.0 °C/s) heating rate, “joint homo-heterogeneous” at moderate (15.1 °C/s) heating rate, and “homogeneous” at sub-fast (52.4 °C/s) and fast (69.4 °C/s) heating rates. High concentrations of CO and CH4 were evident at all heating rates. The increase of heating rate accelerated all gas generation rates and leaded to the gas yield reduction of CO but rising of CO2. Kinetics studies of the reactions around the maximum mass loss rate were carried out ultimately. 1-dimensional diffusion mechanism model (D1) showed best correlation coefficients with the reactions at slow, moderate and sub-fast heating rates and the apparent activation energies slightly decreased from 84.45 and 66.18 to 62.28 kJ/mol. The fitting curve of reactions at fast heating rate was two-stage-style and correlated best to the 3-dimensional diffusion mechanism model based on Jander equation (D3) with activation energies of 33.74 and 11.54 kJ/mol.

An overhanging carbon nanotube/parylene core–shell nanoprobe electrode

A nanoprobe electrode based on electrically conductive carbon nanotube (CNT) as the core structure and biocompatible parylene-C as the insulating shell has been demonstrated. The prototype nanoprobe has been fabricated based on a local synthesis and assembly process using micromachined structures to synthesize suspended and both mechanically and electrically connected CNTs in a room temperature chamber. A 1.7-mm-long, overhanging silicon probe has been designed as the carrier for the CNT nanoprobe with typical length of a few micrometers. A conformal deposition of biocompatible parylene-C has been applied as the insulating layer and a local heating process at the distal end has been conducted to break and expose the CNT-tip section to open up the CNT core for possible electrical measurements. Experimental characterizations have shown good electrical interface between the base of the CNT and the growth-side microstructure, while the exposed CNT/parylene tip makes it attractive for applications in nano-scale electrical probing. These core–shell nanoprobe electrodes could find potential biomedical applications in intracellular electrical measurements.

9 T NbTi Cryogen Free HTS Test Stand

A 9 T conduction cooled superconducting magnet with 50 mm room temperature chamber is developed and tested. The system design allows to fill the chamber with liquid nitrogen. The system is based on a commercial two-stage 4 K Gifford-McMahon cryocooler with cooling power of 1.5 W at 4.2 K. The cool down time of the magnet from room temperature to 3.5 K is 18 hours. A pair of coated conductor based current leads is employed to reduce heat leak to the magnet. The main purpose of the magnet is critical current measurements for HTS wires. Using the magnetic system the angular dependence for short sample of coated conductor (SCS4050 from Superpower) and critical current of a small layer wound coil made of the same conductor were measured at 77 K in external magnetic field up to 4 T. The n-values for short sample are also presented. The measured critical current of the HTS coil in external magnetic field is up to 1.5 times lower than calculated one.

Temperatura e enriquecimento ambiental sobre o bem-estar de coelhos em crescimento

O efeito da temperatura e o efeito do enriquecimento do piso de gaiola sobre o bem-estar de coelhos em crescimento foram avaliados. Quarenta e oito coelhos do grupo genético Botucatu, desmamados aos 35 dias de idade, foram alojados em Câmara Climática, quatro por gaiola (1,00 x 0,60 x 0,40m), em 12 gaiolas que tinham (ou não) metade do piso coberto com cama de palha. As gaiolas foram instaladas metade em sala com temperatura ambiente e metade em sala resfriada. Os animais tiveram livre acesso à ração balanceada e à água nos dois tipos de piso. Para se avaliar o bem-estar, foram realizadas cinco observações de 24 horas cada, uma por semana, sendo registradas as freqüências dos comportamentos: lúdico, estereotipado, exploratório, cuidados corporais e interação e comparadas entre gaiolas enriquecidas ou não nas duas salas. A média de temperatura e a média de umidade relativa do ar foram: 23,6°C e 78,7% na sala natural e 20,6°C e 71,0% na sala resfriada. O comportamento lúdico foi mais freqüente nas gaiolas enriquecidas (7,6 vs 4,3% sala natural e 7,8 vs 3,8% sala resfriada, P<0,01) e as estereotipias foram mais freqüentes nas gaiolas sem enriquecimento (4,4 vs. 2,7% sala natural e 2,1 vs 1,1% sala resfriada, P>0,01). Coelhos mantidos em temperatura natural preferiram a grade à cama de palha (77,9 vs. 22,1%, P>0,01), enquanto na sala resfriada eles não mostraram preferência em relação ao piso (45,9 vs 54,1%, P=0,41). Em sala resfriada, o enriquecimento com palha favoreceu o bem-estar animal.

Plasmon-Assisted Local Temperature Control to Pattern Individual Semiconductor Nanowires and Carbon Nanotubes

We demonstrate a new versatile strategy to rapidly heat and cool subdiffraction-limited volumes of material with a focused light beam. The local temperature rise is obtained by exploiting the unique optical properties of metallic nanostructures that facilitate efficient light-to-heat conversion through the excitation of surface plasmons (collective electron oscillations). By locally heating nanoscale metallic catalysts, growth of semiconductor nanowires and carbon nanotubes can be initiated and controlled at arbitrarily prespecified locations and down to the single nanostructure level in a room-temperature chamber. This local heating strategy can be orders of magnitude (>10(5)) more energy efficient than conventional chemical vapor deposition (CVD) tools in which an entire chamber/substrate is heated. For these reasons, it has great potential for use in process- and energy-efficient assembly of nanowires into complementary metal-oxide-semiconductor (CMOS) compatible device architectures. In general, the high degree of spatial and temporal control over nanoscale thermal environments afforded by this method inspires new pathways for manipulating a range of important thermally stimulated processes and the development of novel photothermal devices.

Local synthesis of silicon nanowires and carbon nanotubes on microbridges

Resistive heating of microline resistors was used to activate vapor-deposition synthesis of silicon nanowires and carbon nanotubes in a room-temperature chamber. The process is compatible with on-chip microelectronics and eliminates the necessity of postsynthesis assembly of nanostructures to form more complicated devices. The process is localized, selective, and scalable. The synthesized nanowire dimensions are 30–80 nm in diameter and up to 10 μm in length, while nanotubes 10–50 nm in diameter and up to 5 μm in length have been demonstrated. Growth rates of up to 1 μm/min for silicon nanowires and up to 0.25 μm/min for carbon nanotubes were observed. This method facilitates the integration of nanotechnology with larger-scale systems.