Requirements

During its lifetime tests, the heat exchanger is placed in a chamber in which the temperature of 85°C is maintained. Water with constant temperature of 135°C and pressure of 1,4 atm is blown through the exchanger. The water flow is about 6 l/min., up to 10 l/min. The test lasts about 600 hours.

System description

System measures heating water temperature and air temperature in the chamber and flow of heating liquid. Values ​​are recorded and the exceeding of set limits is monitored – when any is exceeded, the recording is “compressed” and the operator is warned. Temperature of heating fluid is controlled (via a PID controller) as well as ambient temperature control (via a PID controller on a two-state output controlling fan).

Analog and digital signals are measured by the PCL818L multifunction measuring board.

Měřicí deska PCL 818L

This board is equipped with 16 analog input channels, analog output channel, counter (can be used for flow measurement) and 16 bits of digital inputs and outputs (for heating, fan, or horn). The board resolution is 12 bits. Because the digital inputs and outputs are in TTL levels, the level is boosted by the Efc DIN785 board to 120V 1A (outputs) and adjusted by the Efc DIN782 board (inputs). The board is mounted on a DIN TS35 rail.
Temperatures are measured by resistance sensors in the thermowell, type Pt100.

Since the pressure in the heating pipe is generated by air, this pressure is also measured on the air part by the DMP331 sensor. The sensor range is 1.6 bar, output voltage is 0 to 5V, linearity 0.5%, temperature working range up to 60oC.

The flow rate of the heating liquid is measured by a WF50 propeller flowmeter with an optocoupler, giving 1 pulse per 1 liter flowed.
Because the Pt100 temperature sensors do not have a modified electrical output, they are powered and adjusted to 5V standard in 5E-Ptu modules, an equivalent to standard 5B (“cube”) modules that are plugged into a carrier of four type modules Efc 5B4. The rack and modules are placed either on the DIN TS35 rail.

An important part of the testing system is a program that provides:

  • measurement and evaluation of measured data,
  • monitoring of set limits,
  • control of action variables,
  • graphical display of measured values,
  • full automation of tests: at the beginning performs control of the action quantities so that the set measuring conditions (temperature of the heating liquid) are reached,
  • change the time between stored samples in case of exceeding the limit for one of the variables,
  • continuous calculation of measurement statistics and trends,
  • after reaching the set time, the program will automatically stop the measurement,
  • printing a measurement report,
  • archiving measurements,
  • calibration of sensors and automatic conversion of measured values ​​via calibration curve,
  • and others according to your order.

This control and evaluation program is custom made in the TestPoint development environment. More information request here.