An improved dynamic model of MED-TVC system by considering changes in ejector conditions

Most MED transient behavior studies have failed to cover the actual ejector conditions and falling film heat exchanger capacity over a wide range of ejector changes. An unsteady and steady models of an industrial-scale MED with an ejector have been investigated in this study by considering these two issues. In order to solve differential equations, the variable-step, variable-order technique (VSVO) in MATLAB-Simulink is utilized. After validation of the proposed model, the impact of the falling film heat exchanger heat transfer capacity on the MED effects during overload to the system, and the effect of ejector malfunction at pressures lower than the ejector design motive pressure have been investigated. Also, the start-up from ambient conditions to steady-state con-ditions has been modeled. Results show that by the lowest reducing the motive pressure from the ejector design pressure, the thermo-compressor performance is disrupted and the GOR is reduced by 33 %. Also, a 10 % reduction in motive flow rate causes a 5-fold increase in the saltwater height level of primary effect, while a 10 % reduction in pressure of the motive vapor results in a 10-fold increase; which causes flooding and submerges the heat exchanger tubes, which can alter the performance and might cause failure.