Measuring and testing – Volume or rate of flow – By counting drops – bubbles – or particles
Patent
1995-01-13
1996-11-19
Chilcot, Richard
Measuring and testing
Volume or rate of flow
By counting drops, bubbles, or particles
73433, 73861, G01L 510
Patent
active
055764991
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention comprises an apparatus and method for measuring a diameter that characterizes the size of particulate material that is caused to flow through the apparatus, or for monitoring changes in the characteristic particle size.
BACKGROUND
Where particulate materials such as powdered or granular materials are processed, stored, packaged or the like, it is often desired to monitor the particle size of the particulates.
It is known that the rate of flow of particulate material through an orifice is determined by a number of factors including the bulk density of the material, the size of the orifice or slot, and the size of the particles. Various mathematical formulae have been put forward to describe the relationship between the parameters that affect flow rate. An equation to describe the flow rate of particles through a circular horizontal orifice in the bottom of a flat bottomed container was published by Beverloo, Leniger, and van de Velde, in the Journal, Chemical Engineering Science, volume 15, 1961. This formula is with a flat bottom, K is a constant found by Beverloo et al to be 0.58 for agricultural seeds and sand grains and similar but which may show some small variation from material to material, which may be determined by experimentation, e is the bulk density of the material; g is acceleration due to gravity; D is the diameter of the orifice; d is the characteristic diameter of the particles; and k.sub.h is a parameter that is related to particle size.
When the bottom of the container is not flat, the flow rate can be described by similar formulae. For example, N P Cheremisinoff and P N Cheremisinoff writing in "The Encyclopedia of Fluid Mechanics", volume 4 in "Solids and Gas-Solids Flows", which is published by Gulf Publishing Company, Houston, Tex., U.S.A., have given a formula for the flow rate through a container with a conical bottom; the formula follows the approach taken earlier by Rose and Tanaka who published their work in Engineer, volume 208, 1959. Rose and Tanaka proposed that the effect of a conical bottom on a container can be accounted for by a correction factor (tan .alpha. tan .theta.).sup.-0.35, where .theta. is the angle of inclination of the hopper wall to the vertical, and .alpha. is the angle of repose of the granular material. N P Cheremisinoff and P N Cheremisinoff stated that the correction factor suggested by Rose and Tanaka can be applied to equation 1 giving a formula for the flow rate m.sub.hc of a granular solid through a circular opening in the bottom of a container with a conical bottom: .theta.).sup.-0.35 ( 2)
It will be appreciated by those skilled in the art that there some restrictions on the use of this formula, such as when the ratio of the diameter of the container to the diameter of the orifice is small for example, and proper care and caution should be taken when the formula is used.
The effect of particle size on flow rate from containers with conical bottoms is similar to the effect on flow rate from containers with flat bottoms.
DISCLOSURE OF INVENTION
The present invention provides apparatus and method which enables a characteristic diameter of a flowing particulate material to be monitored or measured.
In broad terms the invention comprises apparatus for monitoring a characteristic diameter of a flowing particulate material, comprising through which the flowing material or a part thereof passes, measurement outlet, and to the dimensions of the particle size measurement outlet, the bulk density of the material, and the flow rate of the material.
If the particle size measurement outlet size D is known and the flow rate m through the outlet is measured, and the bulk density e of the material is known or is measured, and the factor k.sub.h is known, then the characteristic diameter d of the flowing material can be found using an equation such as equation 1 or 2 above or a variation thereof.
In broad terms in another aspect the invention comprises a method for monitoring a characteristic diameter of a flowing particulate mater
REFERENCES:
patent: 3494217 (1967-10-01), Tanaka et al.
patent: 3545281 (1968-12-01), Johnston
patent: 3640136 (1972-02-01), Notle
patent: 4095473 (1978-06-01), Batchelor et al.
patent: 5309769 (1994-05-01), Yamakita
Beverloo, Leniger and Van de Velde, The flow of Granular Solids Through Orifices, Chemical Engineering Science, 1961, vol.15, pp. 260-269.
Chilcot Richard
Industrial Research Limited
Noori Max H.
Vigil Thomas R.
LandOfFree
Measuring and monitoring the size of particulate material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Measuring and monitoring the size of particulate material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Measuring and monitoring the size of particulate material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-542396