Chromel-alumel

The Type N thermocouple (Table 11.60) is similar to Type K but it has been designed to minimize some of the instabilities in the conventional Chromel-Alumel combination. Changes in the alloy content have improved the order/disorder h ansformations occurring at 500°C and a higher silicon content of the positive element improves the oxidation resistance at elevated temperatures. 

Chromel Chromel / Alumel Chromel-alumel Chromel-constantan... 

Temperature measurements ranging from 760 to 1760°C are made usiag iron—constantan or chromel—alumel thermocouples and optical or surface pyrometers. Temperature measuriag devices are placed ia multiple locations and protected to allow replacement without iaciaerator shutdown (see... 

Compressor inlet. Unit is eonstrueted of Chromel-Alumel (niekel alloy) and eharaeterized by an exposed junetion eonsisting of a bare wire with eeramie insulation. One unit is required here. 

Turbine exhaust. Thermocouple is constructed of Chromel-Alumel with an exposed junction. Nine to 12 units are required at this stage. 

Figure 1. Schematic Diagram of the off-axis radiant heated reactor. A. cell body B. linear/rotary motion feedthrough C. transport rod D. projector bulb E. reflector F. insulated stainless steel enclosure G. air cooling port H. gas inlet I. gas outlet/pumping port J. chromel/alumel thermocouple K. high vacuum gate valve L, sample mount.

Figure 1 shows a schematic (elevation) of the Plastofrost apparatus as modified for the present study. The two main components are the heater and the coking attachment. The heater consists of a nickel-plated copper slab in which four 300 watt cartridge heaters are enclosed. A chromel/alumel thermocouple insulated with ceramic tubing placed 5 mm beneath the top surface of the slab measures the temperature (see Fig. 1). The bead of the TC is at the centre of the slab. Figure 2 is a photograph of the assembled apparatus.

A chromel-alumel thermocouple is used to monitor the temperature of the ceramic boat and also acts as a sensor for the furnace temperature controller. A constant flow of clean, dry N2 gas is maintained through the quartz tube. The metal vapor is carried out of the furnace with N2 and condensed to form a polydisperse aerosol. The primary aerosol is diluted by mixing with a filtered dry air stream. The diluted aerosol is then routed to the chamber as required and the excess aerosol is vented out through a glass fiber filter. 

Measurement of Volatile Matter Release Rates. Volatile matter release rates from anthracite were determined by using the apparatus shown diagram-matically in Figure 1. The power input to the 1-kw., 20-volt Hoskins tube furnace and transformer was controlled by means of a Leeds Northrup durationadjusting type program controller which permitted linear heating rates up to 20°C. per min. to be selected with varying soak times and temperatures. A maximum temperature of 1000°C. was used since this was the maximum temperature at which the furnace could be operated continuously. The temperature of the furnace was measured by a chromel-alumel thermocouple inside a... 

The catalyst was placed in the reactor and held by two small plugs of quartz wool. Prior to the reactions, the catalysts were heated in a helium stream (60 ml/min) at 450°C for 30 min and then heated in an ammonia stream at the reaction temperature for 30 min. The reaction temperature was measured by a chromel-alumel thermocouple placed adjacent to the catalytic zone of the reactor. For each pulse, 5 p of the reactant (chlorobenzene or benzaldehyde) were injected by a microsyringe. 

The temperature of a gas oil product flowing through a pipe is monitored using a chromel/alumel thermocouple. The measurement junction is inserted into the pipe and the reference junction is placed in the plant control room where the temperature is 20°C. The emf at the thermocouple junction is found to be 6.2 mV by means of a potentiometer connected into the thermocouple circuit adjacent to the reference junction. Find the measured temperature of the gas oil. 

The nickel single crystal(MARZ grade 99.995%, supplied by MRC) was metallographically polished down to 1 pm diamond paste, then chemically polished as described by Graham and Cohen (15). Transmission x-ray diffraction measurements confirmed the (100) direction of. the face to 0,0.5°. The specimen, of area o>2 cm2, was spot-welded to a nickel rod fastened to the specimen manipulator. It could be heated by electron bombardment or radiativity and cooled to vloO K through the nickel rod and a LN -cooled copper braid. A control unit held the crystal temperature (via a chromel-alumel thermocouple spot-welded to the back of the crystal) constant to within 1 K. 

Test Measurements. A 20-gage Chromel-Alumel thermocouple was welded to the center of the exterior surface of each test panel and three were freely suspended 5 feet above the surface of the oil in separate sections within the structure. Temperature measurements were recorded by the two General Electric potentiometer recorders, connected by means of rotary selector switches. As the switches were rotated,... 

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