An analog simulation technique for distributed flow systems

Simulation of distributed flow systems in chemical engine­ering has been applied more and more during the last decade as computer techniques have developed [l]. The applications have served the purpose of identification of process dynamics and parameter estimation as well as improving process and process control design. Although the conventional analog computer has been expanded with hybrid techniques and digital simulation languages have appeared, none of these has demonstrated superiority in simulating distributed flow systems in general [l]. Conventional analog techniques are expensive, especially when flow forcing and nonlinearities are simulated. Digital methods on the other. hand are time consuming. The purpose of this application note is to describe the hardware for the analog principle proposed by {2, 3]. Using this hardware ffowforcing is readily simulated, which was not feasible earlier[3]. This is an important extension since flow systems are frequently controlled through manipulation of the flow rate. Previously the tech­nique has been applied with constant flows [4, 5]. Results demonstrating the new hardware are presented from simula­tion of a transportation lag and a double-pipe heat exchanger with counter current flows.