Delta M Corporation

The United States of America As Represented by the United States

Reginald W McCulloch

Omar Garcia

Chester S Morgan, Jr

Ralph E Dial

David L Clark

Wilber K Finnell

O Burl Cavin

An apparatus is provided for determining the mass flow rate of a fluid using thermal means. The apparatus utilizes resistance temperature detectors having substantially linear temperature dependencies to determine the mass flow rate of a fluid. The apparatus maintains a constant ratio between resistances of the first and second resistance temperature detectors, the amount of current necessary to maintain the constant ratio corresponding to the mass flow rate of the fluid. The apparatus includes a microprocessor wherein an algorithm relating the current and mass flow rate including thermophysical properties of the fluid, sensor thermal resistance, and probe stem loss information provides the fluid mass flow rate based upon calibration information. Operation in alternate fluids without the need for recalibration is possible utilizing calibration constants obtained in the primary fluid and substitution of thermophysical properties and stem loss characteristics of each fluid in which operation is desired.

Flow sensing device

Differential outputs produced by twin thermoresistive sensors are used to determine the level and flow of a medium. Separate constant current sources supply power to each sensor so that one constant current source supplies sufficient current to cause significant self-heating of the sensor (hot sensor) and the other constant current source supplies relatively little current with insignificant self-heating of its corresponding sensor (cold sensor). Resistive changes in the sensors produced by level and flow changes of the medium produce measurable voltage changes, thereby providing a convenient parameter by which to determine level or flow. Level or flow is determined by dividing the difference in the voltages across the hot and cold sensors by the voltage across the cold sensor.

Differential twin sensor system

A thermoresistive sensor system compensates for ambient temperature of a medium. First and second side-by-side sensors are mounted in the medium, each having a resistance that varies with temperature change in the medium. A thermal compensation control circuit supplies current to the first sensor such that the cube of its current times its resistance (I.sub.1.sup.3 .times.R.sub.1) is constant. The control circuit supplies current to the second sensor at a multiple of the current through the first sensor. A signal based upon the voltages across each sensor is produced as a temperature compensated output. In this manner, the system automatically compensates for temperature changes in the medium which would otherwise degrade the accuracy of the output.

Thermoresistive sensor system

A constant power thermal property sensor compensates for changes in the temperature of the medium into which the sensor is disposed. The sensor has two side-by-side probes mounted in the medium with resistances that vary with temperature. A constant power source produces a current through the first probe and a current source applies a current to the second probe at a fixed ratio of the current in the first probe. The voltages across the probes are monitored and compared, and a signal is produced which is divided by current through the first probe. The resulting signal is representative of the heat transfer between the probes and the medium. The signal does not appreciably vary with changes in the temperature of the medium, and the medium may be a liquid, a gas, a liquid flow, a gas flow, or a combination of media. In this construction, two principal applications for the sensor are liquid level detectors and flow monitors.

Constant power thermal sensor

A probe for measuring heat includes an elongate rod fitted within a sheath, and a plurality of annular recesses are formed on the surface of the rod in a spaced-apart relationship to form annular chambers that are resistant to heat flow. A longitudinal bore extends axially into the rod and within the cylinders defined by the annular chambers, and an integrated heater and thermocouple pack is dimensioned to fit within the bore. In construction, the integrated pack includes a plurality of wires disposed in electrical insulation within a sheath and a heater cable. These wires include one common wire and a plurality of thermocouple wires. The common wire is constructed of one type of conductive material while the thermocouple wires are each constructed of two types of materials so that at least one thermocouple junction is formed therein. All of the wires extend the length of the integrated pack and are connected together at their ends. The thermocouple wires are constructed to form thermocouple junctions proximate to each annular chamber for producing electromotive forces corresponding to the temperature of the rod within the annular chambers relative to outside the chambers. In the preferred embodiment, each thermocouple wire forms two thermocouple junctions, one junction being disposed within an annular chamber and the second junction being disposed outside of, but proximate to, the same annular chamber. In one embodiment two thermocouple wires are configured to double the sensitivity of the probe in one region.

Probe with integrated heater and thermocouple pack

The present invention is directed to an electric cartridge-type heater for use as a simulator for a nuclear fuel pin in reactor studies. The heater comprises an elongated cylindrical housing containing a longitudinally extending helically wound heating element with the heating element radially inwardly separated from the housing. Crushed cold-pressed preforms of boron nitride electrically insulate the heating element from the housing while providing good thermal conductivity. Crushed cold-pressed preforms of magnesia or a magnesia-15 percent boron nitride mixture are disposed in the cavity of the helical heating element. The coefficient of thermal expansion of the magnesia or the magnesia-boron nitride mixture is higher than that of the boron nitride disposed about the heating element for urging the boron nitride radially outwardly against the housing during elevated temperatures to assure adequate thermal contact between the housing and the boron nitride.

Electric heater for nuclear fuel rod simulators

High temperature BN-insulated heaters for use as fuel pin simulators in reactor thermal hydraulic test facility studies comprise a cylindrical housing and a concentric heating element disposed within the housing and spaced apart from the housing to define an annular region therebetween. The annular region contains BN for providing electrical resistance and thermal conductivity between the housing and the heating element. The fabrication method of this invention comprises the steps of cold pressing BN powder at a pressure of 20 to 80,000 psig and a dwell time of at least 0.1-3 seconds to provide hollow cylindrical preforms of suitable dimensions for insertion into the annular region, the BN powder having a tap density of about 0.6-1.1 g/cm.sup.3 and an orientation ratio of at least about 100/3.5. The preforms are inserted into the annular region and crushed in place.

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Caryville, TN, United States of America

Reginald W McCulloch