Lab tests and models
All the training courses comprise lab tests. In the training course B as well as the training course automotive A/C-systems, the participants work with suction devices, manometer bridges, vacuum pumps as well as typical tools and refrigerants. In the practical training, the participants assemble a small refrigeration unit, do the electrical connections and put it into operation within one week. The following lab models provide a brief overview.
Fig 1.
Lab model with glass evaporator
Lab model to visualize the processes in the refrigerant cycle
This model which is equipped with a glass evaporator is used for the basic training courses in order to explain the components and visualize the processes in the refrigerant cycle.
Two manometers and four temperature measuring points help to monitor pressure and temperature changes in the system.
The speeds of the fans at the evaporator and the condenser can be adjusted in order to simulate load changes at the heat exchangers.
The unit is filled with the refrigerant R600a (isobutane).
Fig 2.
Lab model for the capacity control
Lab model for the capacity control
The unit shown above is used for tests for the refrigerating capacity control in “training course C” as well as the training course “basics of a/c units in trains“.
The refrigerating capacity can be reduced via a switching of the pairs of poles of the drive motor, frequency conversion of the supply voltage, a hot gas bypass and a throttle valve in the suction line.
In doing so, the function and the efficiency of the different methods are compared.
Training course C explains the handling of a zeotropic refrigerant mixture on the basis of the refrigerant R407C.
Fig 3.
R744 refrigeration unit for lab tests
R744 refrigeration unit for training purposes
The unit shown is used in the R744 training courses in order to demonstrate the function and the operational behavior of such a unit.
The operational data are recorded via a measurement data acquisition system and visualized on the display.
The refrigerating capacity can be measured at different heat loads, pressures, temperatures, air quantities and compressor speeds.
Fig 4.
Compound refrigeration system with three cooling
points and three compressors
Compound refrigeration system with three cooling points
This model is used in the courses “refrigeration technology C” and “electrotechnology with regard to compound refrigeration units“. It consists of three semi-hermetic compressors, three cooling points and an electronic oil control system.
The lab tests deal with the technical installation of the refrigeration unit and test the function of the compound controller and the cold storage controller with thermostatic, pulse width modulated and stepping motor controlled expansion valve.
Fig 5.
Lab model: expansion valves
Test bench for expansion valves
The refrigerant cycle of this unit is equipped with six different expansion valves connected in parallel.
The function and the control behavior of three different capillary tubes - one automatic, one thermostatic and one pulse width modulated valve – can be tested at changing operating conditions.
The process can be observed in a liquid receiver by means of a glass component.
