Isotherm circulation method

Isobaric-isothermal methods are often also called dynamic methods. One or more fluid streams are pumped continuoirsly into a thermostated equilibriirm cell. The pressure is kept constant during the experiment by controlling an effluent stream, irsually of the vapor phase. One can distinguish between continuorrs-flow methods and semi-flow methods. In continuous-flow methods, both phases flow throrrgh the eqrrihbrirrm cell. They can be used only for systems where the time needed to attain phase equilibrium is sufficiently short. Therefore, such equipment is usually not applied to polymer solutions. In semi-flow methods, only one phase is flowing while the other stays in the equilibrium phase. They are sometimes called gas-saturation methods or pure-gas circulation methods and can be used to measure gas solubilities in liquids and melts or solubilities of liquid or solid substances in supercritical fluids. 

The experimental setup closely resembles that used by Beeck et al. A mixture of C2H4 and H2 is circulated rapidly over the catalyst by a magnetically driven glass turbine of the type described by these authors (circulation rate 1500 liters/hr.). The highly exothermic character of the reaction makes it difficult to perform the experiments isothermally, and only after many fruitless efforts a method was found that appeared reasonably satisfactory. 

Performing a reaction under isothermal conditions is somewhat more complex. It requires two temperature probes, one for the measurement of the reaction mass temperature and a second for the jacket temperature. Depending on the internal reactor temperature, the jacket temperature is adjustable. The simplest method is to use a single heat carrier circuit to act either on the flow rate of cooling water or on the steam valve. With a secondary heat carrier circulation loop, the temperature controller acts directly on the heating and cooling valves by using a conventional... 

The experimental method to measure the main heat transfer data of an arbitrary volume of a liquid charged in an arbitrary container and placed in the atmosphere under isothermal conditions is explained in detail in the present subsection by taking the procedure performed for 400 cm of kerosene charged in a Dewar flask, which is used in the BAM test and is set under conditions of no air circulation in an aluminium box maintained at a Tset-up, in temperature differences of 1.25 K between the Tug and the Tset-up, as an example. 

The most common methods coupled with the three mentioned tests are those also used for evaluating thermal and thermo-oxidative stability, namely measurement of the oxidation induction period by the oxygen uptake test, manometry, DTA, DSC, TG, EGA and EGD in isothermal and nonisothermal (dynamic) conditions oven aging in static or circulating air at 50-150°C, chromatography UV, IR, ESR, NMR spectroscopy, chemiluminescence, viscosimetry, mechanical indices determination, etc. Other criteria refer to discoloration, embrittlement, cracking, loss of elongation, etc. Hydroperoxides concentration can... 

---