Total Radiation Pyrometer Research Articles

Errors of non-contact temperature measurement

In recent years, there is a trend of improving the performance and efficiency of all existing measuring instruments due to a leap in technology. Almost every industry uses a variety of technologies that apply temperature control. Temperature of a heated body can be estimated by measuring the parameters of its thermal radiation, which are electromagnetic waves of different lengths. Temperature measurement is necessary for comfortable automatic control and management of production processes. The use of non-contact means makes it possible to measure the temperature of, firstly, moving objects, secondly, objects in inaccessible places, thirdly, to avoid damage to the measuring instruments when controlling large temperatures. High speed, the possibility of measuring temperature without disconnecting the object from the technological process, ensuring personnel safety, temperature measurement up to 3000 °C – these are the advantages of non-contact temperature measurement method. To obtain reliable values when measuring thermophysical quantities it is necessary to know the processes occurring in interaction of the measuring device or sensor with the object of measurement. These processes affect the magnitude of the measurement error, that is, magnitude of the result deviation from the true value of the measured parameter. This paper describes the errors of non-contact temperature measurement of pyrometers, namely total radiation pyrometer, partial radiation pyrometer, spectral ratio pyrometer, as well as shows the results of comparative calculations between them. Expressions for the evaluation of methodical errors of total radiation, partial radiation and spectral ratio pyrometers are given, as well as the results of comparative calculations of errors are shown.

Investigating Temperature Distribution of Two Different Types of Blackbody Sources Using Infrared Pyrometry Techniques

A comparison between two different types of thermal radiation sources maintaining near blackbody conditions has been carried out in the range from 50 to 500 °C. An infrared total radiation pyrometer was used as a transfer standard to measure the temperature of blackbodies. A thorough study of temperature distribution has been carried out for the large surface source in order to characterize the best location over the surface blackbody for temperature determination precisely of the order of better than 0.1 °C. The expanded uncertainty in the estimation of temperature of the radiating source in the above range of measurement was evaluated to be within ±0.24 °C at 50 °C and ±0.88 °C at 500 °C. The blackbody temperature sources found to be suitable for calibration of infrared total radiation pyrometers and thermal imaging devices in the operational range as mentioned above for laboratory use or other industrial and medical applications.

Principles and methods of temperature measurement

The Concept of Temperature. The Thermodynamic Temperature Scale. Entropy, Temperature, and Statistical Mechanics. The International Practical Temperature Scale. General Characteristics of Temperature Measuring Devices and Treatment of Data. Liquid--in--Glass Thermometers. Sealed Liquid or Gas Sensing Instruments and Bimetallic Sensors. Electrical Resistance Temperature Measurement Using Metallic Sensors. Thermistors and Semiconductors for Temperature Measurement. Thermoelectric Temperature Measurement. Theory of Radiant Heat Transfer as a Basis for Temperature Measurement by Radiant Techniques. The Disappearing Filament Optical Pyrometer. Photoelectric Optical Pyrometers (Automatic and Infrared). Total Radiation Pyrometers. Novel Methods of Temperature Measurement. Pyrometric Cones. Calibration Methods. Installation Effects. Dynamic Response of Sensors. Temperature Instrumentation and Control.

Flame data from a large residual fuel oil-fired burner

Data have been collected from the flame of a full size steam atomised burner operating with a residual fuel oil throughput of 6,100 kg h−1 (13,500 lb h−1). The results reported here are the first to be obtained for a steam atomised oil burner of this throughput. The flame measurements were carried out in the Babcock & Wilcox large burner test facility, which is essentially a water cooled box approximately 22 m long and 3.6 m square internally. Flame temperatures were measured with optical and suction pyrometers and part of the gas sample was analysed for O2, CO and CO2. Flame radiation measurements were made with a wide angled (2π steradians) ellipsoidal radiometer and a narrow angled total radiation pyrometer, located at the chamber ports. The latter instrument was also built into a water cooled probe and traversed through the flame. Gas velocities were measured with a fully water cooled double-headed pitot tube. For total heat fluxes a conductivity type heat flow meter was used. Three flame conditions, ‘a’, ‘b’ and ‘c’, were examined, having respectively 0.5% excess O2, 1.5% excess O2 and again 0.5% excess O2 but with vitiated air at the burner inlet. The directly measured data have been compared for the three flames and the results show, for example, that a maximum flame temperature of 1725°C±20°C occurs in flames ‘a’ and ‘b’ but that the vitiated flame has a maximum temperature of only 1680°C±20°C. The maximum emissivity of 0.95±0.05 occurs in flame ‘b’ although the largest local absorption coefficient of 2.4 m−1±0.70 m−1 was observed in flame ‘a’. Some comparisons have also been made with previous results from other burners. A computerised mathematical model with a diffusion approximation followed by a Monte Carlo simulation of the radiant heat transfer has been used to determine the heat release distribution in the flame. It is concluded that the volumetric heat release () decays exponentially with downstream distance (x) from the burner and can be represented by an equation of the form: Q˙=PλDexp⁡(−xλD) where P and D are the thermal power and diameter respectively of the burner and λ is 1.3.

Experiment on metrological certification of a type of low-temperature total radiation pyrometer

Experiment on metrological certification of a type of low-temperature total radiation pyrometer

Heavy-fuel flame radiation in gas turbine combustors—exploratory results

With lower costs and greater availability, heavy fuel oil appears as an attractive alternative to the conventional gas oil used in industrial gas turbines. However, higher levels of radiation and smoke are expected, and this note reports on some preliminary tests made with a combustion chamber burning fuels of different carbon content, ranging from kerosine to a 25% blend of residual fuel oil in gas oil, at a chamber pressure of 10 atm ∗ ∗ 1 atm = 101.3 kPa. . The combustion rig was equipped with a total-radiation pyrometer and black-body furnace capable of measurement at different axial stations along the spray-stabilized flame. The presence of the residual fuel oil in the gas oil was found to promote significant increases in the mean levels of radiation, emissivity and smoke density, with a modest increase in liner temperature.

URPT-2 equipment for checking total radiation pyrometer telescopes with a sighting index of less than 1/20

URPT-2 equipment for checking total radiation pyrometer telescopes with a sighting index of less than 1/20

Measurement of Flame Temperature and Emittance in Gas Turbine Combustors

The radiation heat load assumes an important role in gas turbine life and performance as firing temperatures and pressures are increased. This first phase of a program for assessing radiant heat loading was mainly concerned with devising measurement techniques. An experimental method for measuring the temperature of luminous flames with a two-color pyrometer and radiant intensity by means of a total radiation pyrometer is described. Emittance data from two combustion liner configurations is included for chamber pressures of from 2 to 7.5 atmospheres over the turbine inlet temperature range of 900 to 1950 deg F.

Automatic compensation of the ambient temperature effect on the thermal emf of total radiation pyrometers

Automatic compensation of the ambient temperature effect on the thermal emf of total radiation pyrometers

Flame spread through randomly packed fuel particles

Reproducible small-scale fires were obtained by burning randomly packed wood shavings (popular) under controlled environmental conditions. The rate of linear fire spread over the uniform slab-like fuel bed was measured for each of the pertinent variables over the following ranges: relative humidity of ambient air:24–59 per centfuel bed voidage:0·838-0·941fuel particle length:1–3 in.fuel loading density:0·153-0·307 lb/ft2A significant increase in the rate of fires spread across the wood shavings was obtained when the relative humidity of the ambient air was decreased, when the fuel particle length was increased, and when the fuel bed voidage was increased. The fuel loading density was found to have no effect on the rate of fire spread over the range investigated.Radiation flux density data obtained from a wide angle view total radiation pyrometer, indicated that the radiation from the burning fuel embers through the fuel bed is significantly greater than that from the overhead flame. Very fine thermocouples inserted into the fuel bed showed that the radiative heating of the unburnt fuel amounts to approximately 40 per cent of the heat required for ignition.

Automated checking of telescopes for total radiation pyrometers and quality tests of photoelectric transducers

Automated checking of telescopes for total radiation pyrometers and quality tests of photoelectric transducers

Application of thermistors to optical pyrometry and temperature control

The theoretical response of a pair of thermistors when used as the sensing elements in a total radiation pyrometer is calculated. The response is shown to be almost linear over a very wide range of temperature. Practical circuits to exploit these properties in a total radiation pryrometer and in a temperature control system based on a radiation pyrometer are given.

Smooth power control for high current furnaces

A method is described whereby the temperature of resistances furnaces operating with currents of 500 to 2000 A can be adjusted continuously and smoothly. The furnace power is supplied from a saturable reactor, the output of which is controlled by a manually operated or motor driven auto-transformer in series with a rectifier. The system described will provide power output voltage supplies which vary as the first, second or third power of time, in response to impulses from a thermocouple or total radiation pyrometer.

On the Measurement of the Temperatures of Unenclosed Objects by Radiation Methods

The functional relationships between apparent temperature and true temperature for the total radiation pyrometer, the optical pyrometer, the two‐color pyrometer, and the two‐temperature pyrometer are developed and discussed. It is shown that it is impossible to measure the temperature of an unenclosed object in the range 2000°–4000°K with accuracy greater than about 10% without prior knowledge of the emissivity. If the emissivity is known within 20%, the temperature can be determined within 1 or 2% by means of an optical pyrometer, particularly if the instrument is operated at the blue end of the spectrum. The accuracy obtainable with the other instruments under equivalent conditions is significantly lower.

Two new total radiation pyrometers

THE MEASUREMENT AND CONTROL of temperature is basic to all industrial processes. Modern automatic machinery exploits the economy achieved by a continuous flow of product, as such machinery requires instrumentation capable of measuring the temperature of moving material in process for efficiency. Total radiation pyrometers are useful for this purpose, and there is a continuing demand from industry for more sensitive, accurate, and versatile instruments.

Two new total radiation pyrometers

The measurement and control of temperature are basic to all industrial processes. Modern automatic machinery exploits the economy achieved by a continuous flow of product. Such machinery requires instrumentation capable of measuring the temperature of moving material in process for maximum efficiency. Total radiation pyrometers are useful for this purpose, and there is a continuing demand from industry for more sensitive, accurate, and versatile instruments. This paper describes two new pyrometers? applicable to a wide variety of industrial and laboratory measurements. They combine good spectral response, high sensitivity, and rapid response, with stability and accuracy adequate for most requirements. These factors are discussed in relation to the design of the pyrometers. The basis for transferring a radiation measurement to a temperature by calibration and some of the limitations involved are also considered.

Calibration Furnaces for Total Radiation Pyrometers

Calibration Furnaces for Total Radiation Pyrometers

Note on the radiation between two coaxial radiating cylinders

The paper discusses the problem of the radiation transfer from an electrically heated inner cylinder to a surrounding coaxial cylinder. Expressions are derived for the total radiation, emitted and reflected, from unit area of each of the cylindrical surfaces between which multiple reflection of radiation occurs. It is then shown how, from these expressions, the relation of the true temperatures to the apparent temperatures of the surfaces (obtained by means of a total-radiation pyrometer or by means of a disappearing-filament optical pyrometer) can be determined.

Some considerations on radiation pyrometers

The effect of varying the distance from the radiating source in total radiation pyrometers of the focussing and non-focussing lens and mirror types is considered theoretically and illustrated by experiments.