UTAR Engineering Student

Cooling Tower Demonstration System Figure 1 : Cooling Tower Demonstration System No Component 1 Orifice 2 Water Distributor 3 Temperature Indicator 4 Make-up tank 5 Heater 6 Inclined Manometer 7 Valves 8 Receiver Tank 9 Blower 10 Temperature Sensor INTRODUCTION AND THEORY: Cooling tower function is used to cool down hot water by removing the heat. The heat of the water is mainly removed by evaporation process. Besides that, water also cooled down by radiation, conduction, convection. However, the effect of cooling is not significant compared to evaporation. Figure  2 : Schematic Diagram of Mass flow for cooling Tower Cooling tower is widely used in industry and it main function is removing excessive unwanted heat from high temperature water. Hea...

Ideal Gas Law Ideal gas law: pV=mRT Where p = pressure             V = volume             m = mass             R = gas constant and       T = temperature When we allow an ideal gas in a container to expand into a larger volume, we get the following relationship:                           Where subscripts 1 denote the initial state  and subscripts 2 denote the final state after the expansion. The Graph of Mass After Mixing, m2 Against Mass Before Mixing, m1 First and foremost, the ideal gas is a type of hypothetical gas which all collisions between atoms or molecules are perfectly elastic and in which there are no intermolecular attractive forces. One can think of it as a set of perfectly hard balls that collide but otherwise do not interact with each oth...

Transient Response of a Position Controller When a step input is given to a position controller, the loop takes time to react to the applied input. Also, depending upon the given system parameters, oscillation can occur at the output during the transient time period. The major cause of the time delay comes from the added inertia of the moving parts. Therefore, the higher the inertia, there will be more delay.  Usually, the system gain is preferred to be high to improve system response time. However, when the gain becomes excessive, it will cause undesired overshoot at the output. Transient response of a system can be easily observed on an oscilloscope when the system is stimulated with a square wave input. Such an arrangement is shown in Figure 4. Figure 4 : System diagram for Transient Respond Experiment The function generator in Figure 4 provides synchronized square-wave and ramp signals. As it is shown in the figure, the ramp signal is used to drive the X-...

Closed Loop Position Controller In a closed loop position controller system, the positional information from an output potentiometer (Po) which is mechanically coupled to a motor is fed back to a control amplifier. Then, the reference position input from the input potentiometer (Pi) is combined with the feedback signal at the input of the amplifier which drives the motor in proportion to the difference between two signals. When the two positions are identical, the output of the amplifier becomes zero. A simplified system diagram of a closed loop position controller which will be used in this experiment is shown in Figure 2. Figure 2 : Close loop position controller There are three amplifiers in Figure 2. The A 1 is an error signal generator, A 2 is an error signal amplifier and A 3 is the driver for the motor M. As Pi is turned away from Po, the difference between two potentiometers voltages become an error signal which appears at the input of A 1 . The error signa...

Closed Loop Control System  Closed loop control system is defined as feedback control system. Closed loop control system is almost identical to open loop control system except it has at least one feedback loop from output to input. Figure 1 : Schematic diagrams of closed loop and open loop             Feedback loop is used to monitor the output and feedback to input. Thus, inaccuracy at output can be corrected and desired output can obtained. Therefore, the output of closed loop control system is more accurate than open loop control system but more expensive and difficult to design. The main advantages of closed loop system are wider bandwidth, output error can be detect, reliable and accurate output. Examples of closed loop system are air conditioner, automatic electric iron, water level controller and servo voltage stabilizer. For air conditioner, fans speed and heats exchange rate of condenser and evapor...

Stabilizing an Unstable Position Controller For a properly designed system, the transient response effect should gradually decay within a few seconds, and the system should reach a steady state operation. However, for an improperly designed system, the transient response can lead into an oscillation which can be sustained over a long period of time. Such a system is unstable and should be corrected for a stable operation. The instability of a system is mainly caused by either a long time constant in the system or an excessive gain in the system. A closed loop speed controller can mitigate oscillation up to certain extent. However, in case a highly stable system is desired with a maximum gain, the system needs more advanced technique than a simple speed control loop. The experiment in this section is limited to a speed controlled stabilization method. The same experiment system as in the previous section is used for this experiment.