Batch cell geometry

Consider the unstirred batch cell geometry shown in Fig. 1 where the general solute mass balance equation of... 

Irrespective of whether an instrument employs fixed cells or batch cells, some design considerations are common to all HSDSC instruments. To measure accurately small powers, it is necessary to ensure good baseline stability throughout the course of an experiment. This is usually achieved by maintaining very accurate control of the calorimetric block temperature and ensuring that the properties of the sample and reference cells, such as geometry, cell volume, local environment, thermal conductivity and conduction pathways, and heating rate, are identical. 

Flexibility and versatility may be important, e.g. the duties of certain reactors may be altered relatively easily, within certain limits by, for example, increasing the rotational speed of a rotating electrode or incorporating an extra number of elements in a filterpress, plate cell geometry. Alternatively, it may be desirable in small batch systems to switch a reactor rapidly from one process to another, with minimal cleaning and downtime. 

Smith et al (1968) looked at mass transfer of a batch dialyser of similar geometry to those of the stirred cells. In summary, mass transfer reduced as stirrer diameter reduced. Mass transfer is lowest at the centre of the impeller. The transition between laminar and turbulent regimes occurred between Re of 20 000 and 30 000. The closer the impeller to the surface, the higher the mass transfer. 

Figure lb describes the proposed geometry of the improved IR cell-reactor. This recycle reactor is to be capable of being operated in either open (flow) or closed (batch) modes of operation. The reactor unit is maintained at the reaction temperature (up to 400°C) and the pump and sampling system are maintained at a constant usually lower temperature (220 C) to ensure maximum... 

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