Philipp Nguyen

Modelling and control of a flash evaporator through ODE system representation in PDEs form

The mass and heat balance in a multi-stage flash evaporator in once-through configuration is modelled with partial differential equations (PDEs) derived from a system of ordinary differential equations (ODEs) that represents a cascade of vacuum tanks. The derived PDE model represents the pressure head, temperature and salinity evolution in the cascade spatially and temporarily as a nonlinear diffusion-advection-reaction process. The process is controlled with relatively simple boundary controls applied on the inlet and outlet ends.

Modelling, optimization and control of a multi-stage flash evaporator by means of motion-planning

Operating a multi-stage flash evaporation plant is usually a task of combining conflicting objectives. In this paper, the emphasis lies on maximizing the total fresh water production while maintaining good efficiency (ratio of produced distillate against total throughput of seawater) of the plant. Based on the evaluation of a cost function combined with motion-planning, an optimal operating point is obtained as a reference liquid level profile throughout the tanks of the plant. The plant has a cascade structure and the entire height profile in all stages is controlled by manipulating the flow rate into the first chamber. Nonlinear and linear control techniques are applied in the form of Feedback linearization, LQR and PI control and the performance is compared based on defined criteria.

Proceedings of the 2015 IEEE Conference on Decision and Control, CDC 2015

Operating a multi-stage flash evaporation plant is usually a task of combining conflicting objectives. In this paper, the emphasis lies on maximizing the total fresh water production while maintaining good efficiency (ratio of produced distillate against total throughput of seawater) of the plant. Based on the evaluation of a cost function combined with motion-planning, an optimal operating point is obtained as a reference liquid level profile throughout the tanks of the plant. The plant has a cascade structure and the entire height profile in all stages is controlled by manipulating the flow rate into the first chamber. Nonlinear and linear control techniques are applied in the form of Feedback linearization, LQR and PI control and the performance is compared based on defined criteria.

Modelling, estimation and control of a Fresh-Water-Cooling system on cruising ships

A Fresh-Water-Cooling circuit is investigated, which is commonly used on ships for recovering the waste-heat from the diesel engine. The excess heat during operation is stored in the coolant, which in turn is used as the primary fluid in a heat exchanger for pre-heating the seawater feed. A dynamic model of the system is derived from first principles and a given scheme of the cooling circuit. A Conditionally-Gaussian-Filter is applied to identify the unknown drifting parameters of the heat exchanger and the outlet temperature. Based on the estimation result of the filter, the outlet temperature is stabilized to a reference value using a nonlinear control law.