Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Establishment of HP process control and monitoring techniques and manufacture of prototypes

Two standard resistance pressure gauges were manufactured in UNIPRESS: Manganin pressure gauge and semiconductor pressure gauge InSb. Application of these gauges for studies of phase transitions in foods bears new challenges. The pressure gauges should be able for work in water, tolerate non-hydrostatic states induced by phase transitions and not mechanically degrade due to corrosion.

Two InSb pressure gauges were made with dimensions 8x0.7x0.7 mm and electric resistance of 29.6 and 35.6 mΩ. The resistance was measured in function of current from 1mA to 100 mA. The resistance was found to be constant, with accuracy better than 10-3. This means that the current of 100 mA does not heat the gauge.

Consequently, increasing the cross section of the InSb gauge allowed to increase the operating current and the output voltage, and secured higher pressure sensitivity.
Additionally, the behaviour of thermoelectric elements: thermoelectric coolers (TEC) and thermocouple Copper-Constantan as well as of Platinum resistance thermometers at high pressure and at low temperatures was studied.

Design of optimized pressure probes, installation and performance evaluation on existing vessel units and on new HP vessels: the scope of the study was to develop new measuring possibilities and to unify techniques for temperature measurement at Partners laboratories.

In order to equip high-pressure units used by the Project Partners, with multi-thermocouple probes, the following design works were made:
- Design of three-thermocouple probe for Multivessel Apparatus U111 700 MPa: for Partner No 1 (TU Berlin),

- Design of two-thermocouple probe for high pressure vessel Resato A100: for partner No 2 (VTT Helsinki),

- Design of three-thermocouple probe for high pressure cell UNIPRESS HP-LT 700 MPa: for Partner No 3 (IF CSIC Madrid).

Developing of the Microscopic Cell and the DTA Cell in the frame of this project, forced us to undertake works on new types of temperature probes. For this probes we develop new technology of feeds-though.

In UNIPRESS, usually we use soldering for sheathed thermocouples feeds-though or Pyrophilite sealed cone type feeds-though for wire type thermocouple. In the new technology both sheathed and wire type thermocouples are glued-in using epoxy resin. This technology is also suitable for optical fibber feeds-thought.

Two types of high-pressure probes were developed, manufactured and applied in the Microscopic and DTA cells:
- Single and multi-thermocouple probes for connector 1/16”,
- Interchangeable single thermocouple probe for DTA cell plug.

Development of experimental techniques for in-situ HP measurements based on optical and thermal methods: optical methods: manufacture of HPLT microscopic cell: the scope of this work was to develop a miniature, temperature-controlled and pressure-controlled high-pressure cell for in-situ observation of biological materials and ice crystals under optical microscope.

The completely assembled prototype was tested in UNIPRESS at the assumed conditions of pressure and temperature at the stand shown in Figure ‎3.35. After equipping the test stand with inverted microscope (March 2005), the first microscopic observations were done.

Finally, the prototype was installed and set up in TU Berlin (P1). The study of vegetal tissues under the high pressure low temperature microscope permits the visual observation of the tissues directly under pressure and during the different phase transition processes susceptible to occur in the working range of the facility, 0.1 to 700 MPa and -50 to +30°C.

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Sokolowska 29-37
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