PSI - Issue 14

S. Narendar et al. / Procedia Structural Integrity 14 (2019) 89–95 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

92 4

3.3. Electric Infrared Heater

The heat input to the test article to simulate heating is given using Electric Infrared Heaters. The dominant mode of heat transfer is through the radiation mode using which rapid heating of the test article can be achieved. The heating panel is an assembly of heater body and IR lamps. The panel body is having a closed cooling duct with a reflector at lamps end and a back cover to hold requisite electrical bus bars for power distribution to IR lamps in delta format. The function of a reflector is to redirect/reflect back the stray IR energy on to the section. The function of cooling is to ensure the temperature of the heating panels is maintained for efficient working. The IR lamp has an overall length of 280 mm and a heated length of 260 mm. It has a linear power density of 250 W/cm and this lamp consumes an electrical power of 6500 W at a rated voltage of 415 V AC, and generates an equivalent radiative power. These IR lamps can generate short wave infrared radiation in the range of 0.5 µm to 2.0 µm wavelength, with the peak power being radiated at a wavelength of 1.2 µm. Both the heating panels are cylindrical in shape. For application of the controlled voltage to the heater cassettes, Thyristor based 3-phase AC power controllers are used. These controllers have a fixed input of 3-phase 415 V AC 50 Hz supply which is converted into variable 3 phase 0-415 V AC 50 Hz supply. The power controllers are capable of giving power outputs in response to a gate voltage of 0-10 V, where 0 V corresponds to no output and 10 V corresponds to full output. The power output varies linearly with the applied gate voltage. The gate keep receives the online voltage feedback from the PID controller to match the desired and achieved temperature profiles based on the set gains. 3.4. Power Controllers

3.5. Control System

To apply a variable heat input to a test article, a control system was used. In the present case, MATLAB ® /Simulink ® software-based controller with National Instruments ® DAQ is used to achieve the closed loop control of temperature.

3.6. Thermocouples

To measure the temperatures at various locations, K-type thermocouples have been used. A K-type thermocouple can be used to measure a temperature within a range of -240°C to 1372°C. 3.7. Data Acquisition and Control System To acquire the temperature data, National Instruments ® make Data Acquisition and Control System (DACS) was used. The DACS was configured to record the data from K-type and R-type thermocouples during the heat flux simulations. A low pass filter of cut-off 2 Hz was used in each channel to remove high frequency noise. The data was recorded at a sampling rate of 10 s/s. The application of controlled temperature in closed loop was done by making use of National Instruments ® acquisition cards interfaced using LabVIEW.