Temperature Control Loop Trainer Model TCL-1 is intended to study, how temperature in a heat exchanger can be controlled. Heat lost by a hot body is equal to heat gained by a cold body. This principle is used in this trainer. This instrument is used in instrumentation, electronics, and chemical engineering laboratories. In process industries, heat is transferred by radiation, by the mixing of hot and cold fluids, or, most frequently, by conduction through the walls of heat exchanger. A shell-and-tube heat exchanger is used in this instrument. The characteristic feature of this device is that the capacities on one or both sides are distributed along the length of the exchanger. The exit temperature of one fluid can be controlled by changing the temperature of the other fluid along the surface of the inner tubes. This is achieved by changing the rate of flow of cold-water inlet, so that the outlet temperature of the hot water is under control. There are several other considerations for control, but they are beyond the scope of this trainer. The heart of this trainer is a heat exchanger. This heat exchanger uses water as medium of transporting heat from hot water to cold water. Water is selected as a media, because water has finite specific constants (sp.gr = 1, boiling point @ 100? C, freezing point @ 0? C, 1cc weighs 1gm), and cannot be compressed like air. For these reasons, water provides stable operating conditions. Controlling hot water outlet temperature or cold water outlet temperature is accomplished in this instrument. The hot water in this heat exchanger flows through 14 numbers of seamless pipes, which are arranged in parallel, and passes on to the other side. All these seamless tubes are enclosed in a concentric outer shell, through which cold water flows. The construction is such that hot water and cold water do not come in contact. Heat is transmitted from hot water to cold water, by conduction, through these pipes. It is possible to measure the inlet and outlet of these hot and cold water. The controller can be activated to change the flow rate of cold water, by measuring hot water outlet temperature. The change in flow rate of cold water changes the outlet temperature of either cold water outlet or hot water outlet.
The Trainer contains:
Hot water boiler, to heat cold water coming from an over head tank (40Lt) placed above the instrument. Control valve to change the flow rate of cold water, by controlling I-P converter centrifugal pump to pump cold water from a built-in 60Lt sump. Rotometer to observe the flow rate of cold water, Four thermocouples measures hot and cold-water temperatures at inlet and outlet ports. A meter indicates the temperature on a panel meter by switch selection, Two solid state relays are used to switch ON 6 KW heaters. The hot water bath has necessary electronics to detect presence of water upto a minimum level before switching ON is provided as a protection measure. to an ON-OFF status of these heaters are indicated. Hand valves are placed at strategic points along the plumbing lines, All the above, assembled on a caster wheel based stand of 6' X 2' X 6'. Interface electronics, DC power supply, control software. IBM compatible computer. Dedicated interface card for the interface electronics, which occupies in one slot of the motherboard. Using this Trainer, we can perform the following experiments. 1.Execute program to scan inlet and outlet temperatures of cold water and hot water of the heat exchanger. Verify the same with the panel meter.
2. Run a program, to tabulate a relationship, between a digital to analog converter (DAC) and the 4-20mA current generated. This current can be monitored on digital indicator. Tabulate this relation DAC number (0-FF) Vs current output (4-20mA). Plot a graph
3. Study a program to change the stem position of control valve, under software control. The stem of the control valve changes its position from one extreme position to the other (usually 0 to 10-15mm) under air pressure. For 3PSI, the stem is in initial position, i.e., and 0mm. For 15PSI, the stem changes its position to the other end. This up/down movement causes, valve to open and close. This action changes the water flow through the pipeline. The water flow can be changed in the range of 3 to 10 Liters/min (LPM). This demonstrates how to change water flow pattern by software. Tabulate the input pressure (3-15 PSI) VS stem position (0 - 10mm). Plot a graph
4. Run PID control program for various bands. Many more experiments can be conducted in the above equipment, as every input and output element is accessible by software. You can formulate an experimental scheme to suit your syllabi needs. SOFTWARE:
In order to assist in conducting the experiment, several WINDOW based features are provided. They screens shown below are for setting the parameters and analysis.
This is how the PID process screen looks like. It is necessary to enter the process parameters like Setpoint variable (SP), Proportional gain (Kp), Integral gain (Ki), Derivative gain (Kd), Sampling time in mS. This screen is displayed in response to the running of PID control program with the above parameter settings.
Upon saving this logged trend it is possible to make post analysis of the above controller. The following icons, represent various features available as post analysis options. Specifications: a) Control Valve:
Fluid : Water.
Body form : Globe-2-Way.
Size body/port/CV : 1/2"- 1/4" - 2.0 USGpm.
End Conn./Rating : Flanged RF - ANSI -150#.
Body material : CCS.
Trim form / Material : Contoured / SS304.
Flow chart/Direction : Linear / Under.
Actuator type : Diaphragm.
Control Signal : 0.2 - 1.0 Kg/cm2.
Valve action : Air to open.
Total stem travel : 18mm. b) Hand Operated Valves:
Quantity : 2 nos.
Size :1/2".
Coating : Nickel.
Type : Close open close. c) Gate Valve:
Quantity : 5Nos
Size : 1/2".
Service : Water. d) Heat Exchanger:
Construction : Shell-tube.
Service : Water.
Shell : 3".
Length : 30".
Tubes : 14 Nos. seam less.
Connections : 1/2" for inlet and outlet plumbing.
Drain : 4Nos gate valves. e) Electro-Pneumatic Converter:
Input : 4-20mA.
Output : 3-15 PSI.
Input Resistance : 90 Ohms.
Characteristics : Linear to input current.
Air supply :1.4Kg/cm2.
Consumption : 30 L/Hr typical.
Pressure : 1.4 bar.
Connection : 1/4" NPT.
Mounting :Wall. f) Air Filter Regulator:
Service media : Air.
Indicator : Pr gauges.
Max input : 10Kg/cm2.
Hose connection : 1/4" BSP. g) Solenoid:
Service : Water.
Coil Voltage : 220 VAC.
Service connection :1/2". h) Current Meters:
Digital : 0-20mA FSD. i) Rotometer:
Service : Water.
Connection : 1/2".
Range : 0 to 10.5 LPM.
Metering tube : Borosilicate.
Float : SS 304.
Needle : Provided, integral. j) Water Pump:
Voltage : 220V AC.
Lift : 2000 Lt./Hr at 20Meters high.
Service : Water.
Connection : 3/4" upstream.
1/2" reduced for downstream. k) Water Tank:
Sump : 1No.
Overhead : 1No.
Capacity : 100 Lt. Each.
Material : Toughened plastic. What you must provide the following facilities at your cost, at the time of installation:
You have to provide compressed air @ 5kg/cm2 from your in-house compressor.
Constant water line to be provided by you for filling the water tank and discharge pipelines must be provided to drain the water from the tank after the completion of the experiment.
You must provide an IBM Computer or Compatible system. It must have at least one vacant ISA slot on the motherboard, to enable the ADD-ON card to be inserted, which will communicate with the trainer. The minimum configuration of the system must be any Intel make standard CPU, 32MB RAM, one 1.44?FDD, HDD with any capacity, CD ROM drive, and a color monitor.
You must provide the necessary electrical fittings at 230V AC single phase, and accessories, observing all the safety standard features, like circuit breakers, safety switches and fuses etc, so that the operator will work under safe environment. Proper electrical grounding (earth) must be provided to the instrument setup as a whole.
This requires 10 Sq.ft floor space for conducting experiments by the students or trainee.
Good electrical connection, with proper earthing is required.
Mobility: Mounted on robust caster wheels
Dimensions : 6' X 2' X 6' (L, B, H)
Specifications are subject to change without notice. Changes in specifications may be effected even after receiving confirmed purchase ORDER. |
