Measuring and testing – Volume or rate of flow – Thermal type
Patent
1993-08-13
1994-08-23
Goldstein, Herbert
Measuring and testing
Volume or rate of flow
Thermal type
G01F 168
Patent
active
053396880
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a device designed for measuring a gas flow and having a measuring body to be placed in the gas flow, and a heating means for heating the measuring body in relation to the environment. The invention also relates to a method for using the device.
DESCRIPTION OF THE BACKGROUND ART
A typical spray booth line for painting car bodies is divided into a plurality of successive sections which by means of fans are supplied with vertical supply air flows through filter roofs provided in the sections. In those sections where the car bodies are sprayed with paint, exhaust air flows polluted with paint particles and solvents are evacuated by means of fans. In order that polluted air should not spread horizontally from the spray sections to the other sections, it is vital that the horizontal air flows between the sections be directed towards the spray sections. It is also vital that the horizontal air flows be small in relation to the supply and exhaust air flows so as not to create secondary eddies in the spray sections or entail that paint particles are transferred from one car body to another. The horizontal air flows are suitably regulated by such a speed control of the supply air fans that the size and the direction of the horizontal air flows will become as desired. To permit carrying out this control in optimum fashion, the horizontal air flows must be accurately measured.
Thermal flow transducers, i.e. transducers having a measuring body which should be placed in the flow to be measured, and a means for heating the measuring body, and relying in different ways on the fact that the flow cools the heated measuring body, are known in various designs. However, none of the prior-art flow transducers can be considered to comply with the requirements 1-3 which are listed below and which must be placed on a flow transducer to be used in a spray booth line of the type described above. measuring body of the flow transducer may only be heated to a temperature which but insignificantly exceeds the ambient temperature. and other chemicals on the measuring body. zero, especially in the range -2 m/s-+2 m/s.
SUMMARY OF THE INVENTION
The main object of the present invention is to provide a flow transducer meeting these requirements.
This object is achieved by means of a device which is of the type described by way of introduction and which according to the present invention is characterised in that the measuring body is in the form of a cylinder which is symmetrical with respect to a plane of symmetry extending through the axis of the cylinder, that a slot, containing said plane of symmetry, extends axially a certain distance into the cylinder from one end thereof, so as to divide a first portion of the cylinder into two halves which are symmetrical with respect to said slot, that the heating means is provided at a distance from the bottom of the slot in a second portion of the cylinder which is not divided by the slot, that a temperature sensor is provided in said second portion of the cylinder adjacent the bottom of the slot for measuring the temperature to which the measuring body is heated by the heating means, and that a temperature sensor is provided in each of the symmetrical cylinder halves adjacent said one end of the cylinder for measuring the temperature in the respective half.
The measuring body preferably is in the form of a straight circular cylinder.
Another object of the present invention is to provide a suitable method for using this device.
According to the invention, this object is achieved by a method which is characterised by so disposing the measuring body in the gas flow that the slot extends at right angles to the gas flow with one half facing the gas flow and with the other half facing away from the gas flow, heating the measuring body by the heating means to a temperature exceeding the ambient temperature by a predetermined value, measuring the temperature in each of the two symmetrical cylinder halves, and calculating the gas flow on the bas
REFERENCES:
patent: 1996943 (1935-09-01), Wile
patent: 2924972 (1960-02-01), Biermann
patent: 3081628 (1963-03-01), Salera
patent: 3500686 (1970-03-01), Bell, III
patent: 3623364 (1971-01-01), Withrow
patent: 4856329 (1989-08-01), Buck et al.
Gustavsson Lennart
Johansson Anders
ABB Flakt AB
Goldstein Herbert
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