Work flow: From a powder or bulk solid to the optimal hopper
The image demonstrates the procedure:
- Measurement of flow properties (yield loci, wall friction, time consolidation) with a ring shear tester
- Evaluation of the test results automatically by RST-CONTROL 95, the software for controlling our ring shear testers
- CAHD allows the interactive adjustment of the measured values, e.g., to gain more safety, and calculates the required hopper wall inclination and outlet dimensions. For this purpose, Jenike's diagrams were recalculated in smaller steps according to the theory in Jenike's Bulletins 108 & 123.
- Finally, the user can apply the calculated data to the design of a silo.
MotivationThe original application of shear testers is silo design for flow based on Jenike’s fundamental contribution around 1960 (e.g., Bulletin 123).
Jenike's equations can only be solved numerically. Jenike therefore provided design charts. This was a big step forward, because from then on many thousands of silos were successfully designed based on Jenike's approach.
The application of design charts can be time-consuming (often iteration is required; variation of hopper geometry or parameters such as wall friction increases the effort). Therefore, there is a demand for software solutions. Such exist, mostly very simple, based on approximate equations and programmed for spreadsheets. This can work, but often the problem is the lack of detailed documentation, which makes it difficult to pass the software on to successors.
CAHD: Interactive program that overcomes the above limitations
Properties of CAHD - Computer-aided hopper design:
- CAHD is based on Jenike's original equations solved numerically; optional application of other approaches/modifications.
- Consideration of stress dependence of flow properties (wall friction angle, effective friction angle, bulk density ...)
- CAHD is Interactive (e.g., user-controlled curve fitting; selection of "average" or "maximum" wall friction angles)
- Solutions for the entire range of flow property data (e.g. hopper inclination angle for mass flow as a function of local hopper diameter)
- Transparent evaluation: Critical points (intersections) are
shown on diagrams
- Documentation (pdf) of each design: Flow properties, applied theories, safeties, user adjustments, silo design results in tables and diagrams.
System requirements: PC running Microsoft Windows 7/8/10*, USB-Port for Dongle, recommended screen resolution min. 1024x768.
*) Microsoft Windows 7, Windows 8, Windows 10 and Microsoft EXCEL are registered trademarks of Microsoft Corp., U.S.A.
Technical modifications and errors excepted.