Control of Heat Exchanger with Variable Heat Transfer Surface Area

Abstract

The work deals with the development of a control system for heat exchangers with variable surface area of heat transfer, used, in particular, for heat pumps intended primarily for heat supply systems using the high-quality law of regulation of the heat supply mode (with a constant flow rate of the heat carrier). The aim of the work is to develop a scheme for the control of a heat exchanger with a variable surface area of heat exchange in which main dis-turbances will be compensated: i.e. the temperature of the heat carrier, heat carrier’s flowrates, and changes in the thermophysical parameters of the heat carriers. This goal has been achieved using a custom PID controller in the contour of control of the drive of the mov-ing heat-insulating insert. To solve this problem, we obtained the equations of the statics of the heat exchanger with regard to the adjustable insert, the dynamic model of the heat ex-changer taking into account this insert. The novelty of the work is control laws of an adjusta-ble heat-conducting insert between the primary and secondary coolants of the heat exchanger, which allow compensating the main disturbances, which influence the heat exchanger. A method has been developed for solving differential-integral equations of heat exchanger stat-ics with an insert (HEI), which allowed analytically expressing the ratio of average integral heat carrier temperatures in a heat exchanger depending on the heat exchanger length, which allows building a control system for a heat exchanger with a variable heat exchange surface area.

Keywords

• heat exchanger
• a
• variable heat transfer surface