Remote control of heating system

Czech CONTROL OF HEATING SYSTEM ©Jan Kostohryz (Result of MSc Thesis supervised by Tomas Vyhlidal Ph.D.) CAK MSc Thesis (in czech)

Laboratory Heating System Laboratory heating system is developed for demonstrating and testing the control and identification algorithm of a system with time delays. Time delays in the system a) represent transportation delays in the pipe lines b) help to model distribution of the parameters of the key subsystems. Laboratory heating system consists of two independent heating circuits. Left circuit interacts with the right circuit (and opposite) through the heat exchanger. Each heating circuit consists of: pump,mixing valve(s),pipe lines,cooler,heater. Let us first describe in detail the left circuit. The circulation of the medium in the circuit is forced by the Pump which is controlled manually by determining its pipe-lift. The flow through the pump is measured by a flow-meter. The heat source is an accumulation-type Heater. Notice that the inlet and the outlet water temperatures are measured as T_LHi and T_LHo , respectively. Even though the performance of the heater can be controlled by the signal U_LH, due to relatively large capacity of the heater, the control actions are slow. Therefore, it is better to control the water temperate which goes to the exchanger, and which is measured as T_LEi, by a mixing Valve, which is controlled by the signal U_LV1. In fact this signal, via a servo of the valve, controls the position of the valve seat determining the mixing ratio of the hot water from the heater and cooled water from the cooler. The temperature of the water leaving the exchanger in the left circuit is measured as T_LEo. The second mixing Valve in the left circuit, which is controlled by the signal U_LV2, allows us to divide the water stream into two branches. One of the braches goes to the exchanger and the other accomplishes a bypass of the exchanger. The flow through the bypass branch pipe is measured by a flow-rate-meter. In this way, by the signal U_LV2 we can control the amount of the heat transferred between the circuits. Consequently, the temperature of the water leaving the mixing valve and forced towards the Cooler is also determined by the mixing ratio in the valve given by U_LV2. The temperatures in the inlet and outlet of the Cooler are measured as T_LCi and T_LCo, respectively. The cooling performance is controlled by signal U_LC. The water which leaves the cooler is forced by the pump towards the Heater. The circulation of the medium in the right circuit is forced by the Pump which is controlled manually by determining its pipe-lif. The flow through the pump is measured by a flow-rate-meter. The heat source is a flow-type Heater. Its inlet and the outlet water temperatures are measured as T_RHi and T_RHo, respectively. Unlike the dynamics of the Heater in the left circuit, the dynamics of this Heater is relatively fast and, therefore, the heater can serve well as an actuator controlling the water temperature entering the exchanger, which is measured as T_REi. Alternatively as an actuator by which this temperature can be controlled can serve the mixing Valve. In this valve, the hot water from the heater is mixed with cooled water from the Cooler R in a ratio determined by the position of the valve seat controlled via a servo by signal U_RV. This mixing valve determines the flow passing through the heater. The temperature of the water leaving the exchanger in the right circuit is measured as T_REo. The water is then forced towards the Cooler. Its inlet and outlet water temperatures are measured as T_RCi and T_RCo, respectively. The cooling performance is controlled by signal U_RC. The water which leaves the cooler is forced by the pump towards the Heater. To sum up, in the system, twelve temperatures are measured by thermometers PT1000. The output signal from the thermometers processed by PC in program MATLAB and Real Time Toolbox. Picture 1 Diagram of the Laboratory Heating System Picture 2 Laboratory Heating System