Heater Assembly Research Articles

Kinetics of surface reactions of CF3 radicals

The kinetics of reactions of CF3 radicals on various substrate materials has been studied in a gold-coated, stainless-steel, very-low-pressure photolysis (VLPΦ) cell as a function of temperature and radical concentration. The substrate materials were gold, stainless steel, copper, copper oxide, and silica. The CF3 radicals were generated from CF3I by IR-multiphoton decomposition. The reaction products observed with a mass spectrometer included HF, CO, CO2, COF2, SiF4, and C2F6. Rate constants were obtained as a function of temperature. CF3 reacted most rapidly on copper oxide surfaces; the other metal surfaces were less reactive, and the silica surfaces were least reactive. Previous studies from this laboratory that had reported the reaction of CF3 on fused silica are reinterpreted as reactions of CF3 on the stainless-steel heater assembly.

Vacuum outgassing and gas phase thermal conduction of a microgravity physical vapor transport experiment

An experiment to study the effects of microgravity on the deposition of organic thin films using physical vapor transport (PVT) was successfully flown and operated on the Space Shuttle mission 51I. Nine PVT ampoules contained three types of organic solids, buffer gases from He to Xe, and special substrates. The sealed ampoules, heated to 400 °C by concentric heater assemblies, were contained in nine evacuated and sealed UHV quality stainless-steel cells. The outgassing of a cell’s contents and resultant heat loss by gas phase conduction are important parameters for the cell power requirements and ampoule boundary conditions. We report the measurement of the absolute partial pressures of nine residual gases generated within the cells and the radial gas phase heat conductivity in the absence of gravity. H2, CH4, and CO2 were the dominant gases, with total pressures ranging from 0.3 to 2.5 Torr. The heat loss was observed to be pressure dependent, ∼15 W/Torr, and thus an important loss mode.

High-performance coaxial EPR cavity for investigations at elevated temperatures and pressures

A microwave cavity suitable for heating a sample to temperatures above 800 °C within 15 s at gas pressures above 17.5 MPa is reported. The cavity is coaxial and operates in the TE011 mode at frequencies between 9 and 10 GHz. The heating element is constructed of nickel–chromium (i.e., Chromel) wire. It consists of two concentric helices wound in opposite senses (directions) and connected in series so as to minimize the magnetic field generated by the heater current. The heater is potted in magnesium oxide–phosphate ceramic and placed inside of a cylinder made from 50-μm copper foil which provides uniform temperature distribution and shields the heater from the microwave field. This assembly then serves as the heating element and the coaxial conductor of the cavity. The diameter of the coaxial heater assembly is approximately 7 mm. The sample is confined by a cylindrical quartz cuvette which surrounds the coaxial conductor. Sample thicknesses of 0.2 to 1.0 mm can be used. Heating from room temperature to 800 °C requires between 15 and 20 s. Operating pressures up to 17 MPa have been used, although the structural design limit of the brass or beryllium copper walls is greater than 22 MPa. Modulation coils are placed in recessed areas of the cavity walls and covered with a thin layer of copper. Cooling water flows through channels cut into the walls to maintain constant microwave parameters. Q factors of 8000 –12 000 can be obtained depending on the sample.

Thermal hazard evaluation of styrene polymerization by accelerating rate calorimetry

The thermal polymerization of inhibited styrene monomer is investigated by Accelerating Rate Calorimetry (ARC). The time-temperature-pressure data generated by this technique are utilized in evaluating the thermal hazards associated with the industrial processing of styrene monomer. Several examples are given on the interpretation and application of ARC data to environments ranging from lab to plant-scale conditions including discussions concerning the similarities and dissimilarities between the ARC and large-scale equipment. The polymerization of styrene monomer is also used to evaluate the performance of the ARC over a broad temperature range, 80–300°C. The data indicate that removal of the radiant heater assembly yields better agreement between the heat of polymerization of styrene as measured by the ARC and corresponding values from the literature. This effect is believed to be observable only under conditions of low reaction rates for long periods of time such as in the case of styrene monomer.

An automated high precision calorimeter for the temperature range 200 K–400 K. Part II. Design of temperature controllers

The design and construction of precision temperature controllers, capable of tracking the temperature of the samples to within 1 mK for ramp heating rates from 0.05 to 10 K per hour, are discussed. A tutorial section on the evolution of the control loop configuration is first given. This is followed by an outline of the refinements of the basic control loop desirable in the actual implementation of the electronic controller. The novel features of the present system and its performance are then briefly discussed. Finally the inadequacy of the conventional PID controllers for this application, the estimation of the time constants of the physical system needed in the design of the electronic controllers and the pitfalls in using a simple model of the heater plus thermometer assembly with a single pole are also discussed.

A high temperature, ultra high vacuum facility for heavy ion simulation of neutron radiation damage to potential reactor materials

The University of Wisconsin-Madison facility for simulating neutron damage to potential reactor materials is described. Heavy metal ions from a tandem accelerator bombard metal specimens heated as high as 1000°C at pressures below 10 −8 torr. Special feautures of the facility include a radiation heater assembly which allows integration of the beam current, an ultra high vacuum environment which is characterized by partial pressure analysis, use of 15–20 MeV heavy metal ions to induce the damage in the specimens, and direct measurement of the beam composition. This facility is suitable for studying radiation effects in the refractory metals as well as other potential reactor materials.

A simple heater attachment to precession camera for high temperature diffraction studies up to 1000°C

A simple heating attachment suitable for taking x-ray precession photographs at high temperatures is described. It consists of a platinum wire-wound heater, split at the middle for sample insertion and x-ray irradiation. The heater is mounted on a quartzsupport and is independant of both the goniometer head and collimator. This makes crystal mounting and alignment at high temperature as easy as at room temperature and precession photographs up to precession angle\(\bar \mu = 30^ \circ \)=30° can be taken without any interference from the heater assembly, up to 1000°C.

Effects of Core Spray Cooling at Stationary State after Loss of Coolant Accident

In order to determine the conditions under which core spray cooling can be effective after loss of coolant accident, spray cooling experiments have been conducted on a heater assembly at low heat f...

Some Effects of Pressure on Forward and Reverse Combustion

Abstract Experiments have been performed in a linear near-adiabatic system for the purpose of extending data on reverse and forward combustion from atmospheric pressure to 1,000 psig.Results obtained from reverse combustion appear to conform qualitatively with the existing description of the process when reaction kinetics are suitably modified to account for the increase in pressure, z. e., increasing the pressure decreases the peak temperature and increases the combustion zone velocity.Forward combustion appears to be a fuel dominated process wherein peak temperature and combustion zone velocity are not very sensitive to changes in pressure. The moderate effects of pressure that do exist at low flux virtually disappear at high flux providing all oxygen is consumed. With this provision, increasing the pressure decreases the frontal velocity and increases the peak temperature.Results are shown graphically which demonstrate the effects of pressure on peak temperature, rate of advance, oil recovery, air/oil ratio, carbon oxides produced and temperature distributions. Introduction Numerous field tests of oil recovery using the technique of underground combustion are now in progress. Operating pressures used are always substantially in excess of atmospheric pressure. Nevertheless, the literature contains no laboratory data pertaining to the effects of pressure except for those of Martin, Alexander and Dew. Unfortunately, these data appear to reflect heat losses which may have obscured some of the effects of increased pressure.The underground combustion processes are exceedingly complex, and general concepts relating to them have necessarily been described in relatively simple terms. Particularly with regard to forward combustion, the interaction between multiphase fluid flow, heat transport and various rate mechanisms is so involved that to date a rigorous treatment is not available.In this paper a linear near-adiabatic system is described which was found capable of operating at pressures up to 1,000 psig and temperatures of at least 1,100 F. Using this equipment, experiments on both forward and reverse combustion were accomplished at elevated pressures and the data presented as a function of air flux or temperature.It will be assumed that the reader is familiar with the papers of Wilson, Wygal, Reed, Gergins and Henderson on forward combustion and that of Reed, Reed and Tracht on reverse combustion, so that it is not necessary to repeat the details of the two processes. EQUIPMENT AND PROCEDURE It was decided to study the effects of pressure over the interval 0–1,000 psig using a near-adiabatic system. Since satisfactory operation of such a system requires very thin tubing walls, it proved necessary to insert the entire combustion tube and heater assembly into a high pressure jacket in such a way that the internal tube pressure could be counterbalanced by pressurizing the annulus. This meant that the numerous heater and thermocouple wires had to pass through gas-tight seals that required considerable effort to maintain effective.An unexpected difficulty arose in connection with the nature of the annulus pressuring gas. It turned out that the composition of this gas critically affected the functioning of the adiabatic control system.Operation of the equipment at elevated pressures was not particularly difficult. The problems that did arise were a direct consequence of the large numbers of connections and seals involved. EQUIPMENT The equipment consisted of the combustion tube which fitted within the pressure jacket. SPEJ P. 127^

Automatic Zone Refiner for Organic Compounds

A simple mechanism has been developed to carry out reciprocating motion in zone refining; this motion pattern provides, in effect, an infinitely long heater. The ingot is raised slowly into a battery of heaters, and is then cyclically moved quickly downward and slowly upward through one interzone distance. The unit includes a programmer that discontinues the refining after one to 100 passes. An easily fabricated heater assembly, suitable for use between 50 and 350°C, is also described.

Increased System Worth Through Reliability Design Review

It is the purpose of this paper to present the results, conclusions and recommendations of the analysis of electronic equipment to provide the optimum system worth, with regard to reliability and performance. Additional parameters set up in the three mathematical regimes are minimum weight, minimum geometric space envelope, schedule time delays, and cost trade-offs. This paper further proposes a methodical engineered system which attaches numerical quantities and mathematical relationships which may be measured and compared to parameters determining electronic equipment system worth. Value engineering concepts are thus generalized for electronic equipment to include many significant, parameters for optimum system worth -- with probability of success and performance replacing cost reductions as the prime yardstick for analytical trade-off comparisons. Forcing function inputs include transportation and handling loads, gunfire, takeoff, landing, flight maneuvers and catapult dynamic loads. These are mathematically treated as random vibrations, random shock, sustained acceleration, steady-state sinusoidal vibrations at resonance, sweep-cycle sinusoidal vibrations, and sudden impulse shock. The electronic equipment is analyzed under all probable conditions of the true environment plus the requisite conditions of the governing military specifications. Critical deflections, rotations, stresses and deformations are determined at all key substations of each dynamic subsystem of the electronic equipment. Each electronic tube is subdivided into the significant subsystems: 1. Cantilevered gun and assembly 2. Cantilevered heater and button assembly 3. Ceramic rods and helix 4. Outer envelope 5. Collector end 6.