New Technique Simulates Fluid Flow on a Computer

Computational fluid dynamics (CFD) is a technique used to simulate fluid flow on a computer. Until recently the computing power required for the complicated mathematics restricted the use of CFD to academic institutions, government agencies and large corporations. The hardware and software advances made in recent years have resulted in CFD now becoming available as an engineering tool suitable for commercial use.

One South African company determined to benefit is Actuators and Controls – designers and manufacturers of the Mitech range of control valves. Specialising in severe service valves, the use of CFD enables the designers for the first time to see what is happening inside the valve in operation. This enables them to verify that cavitation will not occur in liquid applications and that velocity limits are maintained for gasses and vapours. Ultimately the use of CFD will enable the designs to be optimised to give larger capacities in the same size of valve or conversely the use of a smaller valve will be possible for the same flow rate.

To justify the cost of the software, it has been set up in a dedicated division of an independent engineering services consulting company. This division is headed up by Nicholas Sessions – a mechanical engineer from UCT.

The first job to be completed was the verification of the design of the disk stack trim used in England to test a 27MW seawater injection pump – where the 400mm valve had to drop the pressure from 650bar to 10bar (see Figure 1). The results from the CFD simulation agreed to the actual performance measured by the pump company within 10%.

Examples of other work completed is the analysis of the mixing of hot gas (950°C) in a heat exchanger at SASOL (Figure 2) and the flow characteristics of a MITECH Globe Control Valve. (see Figure 3).

The same software can be used to analyse the heat produced by electronic components in an enclosure and design of a cooling system to suit.

For further enquiry, please contact Nicholas Sessions on 083.299.1194.

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