Process Controls & DynamicsOur client is a large food processing company, which is outsourcing engineering design. Your company has won the bid to work on the design of the temperature control system around a steam-heated heat exchanger. The client will have a boiler using natural gas to create medium pressure steam (150 psig) available through a header. The resulting condensed steam will naturally return to the boiler through the planned pipe network, which will operate at 120 kPa.
The client uses a central glycol loop throughout the plant to add or take away heat when needed at various different unit operations. The glycol must be maintained at a temperature of 110°C but due to changing heat loads in the plant the glycol temperature varies between 30°C and 85°C. The flow rate of the glycol is maintained constant at 1.1 kg/s.
Design a steam-heated heat exchanger as well as the necessary control system that will suit the need of the client. Your report must include a description and reasoning of the proposed system, schematic of the heat exchanger, piping and instrumentation diagram (P&ID), specifications of the control equipment and estimate of the capital cost.
The necessary calculations (dynamic modeling - including Polymath, MATLAB or Python code, tuning, costing) must be present in the appendix.
(Design of system and open loop model)
- Suggest a minimum of two possible feedback control schemes and give reasons for your final choice. Present a P&ID diagram of your proposed system.
- Design the heat changer using your heat transfer knowledge (this includes its size, material of construction etc.). Include a schematic of the proposed heat exchanger as well as specifications for sensors and control valve.
- Develop an open-loop dynamic model for your proposed system using the software package of your choice. Predict the behavior of the outlet temperature in the event of a step change in the glycol temperature
(Design of system, closed loop model, and costing)
- Develop a closed-loop dynamic model for your proposed system using tuning techniques.
- Evaluate the capital cost of the proposed system.
Assumptions and Clarifications for the Assignment:
You have to find the operating pressure inside the heat exchangerbased on steam pressure (150 psig) and the pressure drop by the control valve.
Assume that the operating Temp of the heat exchanger is the same as the temp of thesaturated steam
(Tsteam = Tsaturation and Toperating = Tsteam)
Assume that the over all heat transfer coefficient (U) is constant (for a typical steam-glycol from literature).
