The testing device for the adiabatic temperature change was designed and built in the Laboratory for Refrigeration and District Energy (LAHDE). The device generally comprises two main components, the thermostatic chamber and, within it, the electromagnet assembly. The purpose of the thermostatic chamber is to control the temperature and thus make measurements possible over a relatively wide temperature range. The thermostatic chamber (610×530×330 mm³) is made out of a thick (d=105 mm) expanded polystyrene (EPS) to achieve sufficient insulation from the ambient. The temperature inside the chamber is managed by a thermoelectric cooling/heating system, which comprises a 102 W Peltier module (Adaptive^® APH-241-10-08-E), an inner heat exchanger (Al fins with a fan) and an ambient heat exchanger (Al plates with 8 heat-pipes and a fan).

The heart of the experimental device is the electromagnet assembly, which is placed inside the thermostatic chamber. Inside the magnet’s gap a sample holder is placed. The holder is made of Bakelite because of its good mechanical (solid structure of the holder) and relatively good thermal properties (insulation of the sample). A sample with a maximum volume of 5×5×4 mm can be placed inside the holder. The adiabatic temperature change of the sample is measured directly by the Type-K thermocouple, which is positioned inside the sample (thermocouple is surrounded by MCM) with a small amount of thermal grease to increase the thermal contact conductance from the sample to the thermocouple. A very thin thermocouple (d=0.08 mm) was chosen, due to its fast response and to decrease the thermal influence on the sample (low thermal mass – fast heat diffusion).

• Thermostatic chamber insulation: EPS, 610×530×330 mm³, d=105 mm
• Peltier module: Adaptive^® APH-241-10-08-E, =102 W, ΔT_max=67 K
• Ambient heat exchanger: Al plates, 8 × heat pipes, fan (12 V DC)
• Inner heat exchanger: Al fins, fan (12 V DC)
• Electromagnetic assembly: Iskra Magneti d.d., Ferro-magnetic core CU90A, 2×480 turns Cu coils
• Data acquisition: NI-CDAQ-9174
  • NI 9214 (thermocouple)
  • NI 9207 (analog input)
  • NI 9263 (analog output)
• Thermocouple on sample: Type-K, d=0.08 mm