Institute of Food Technologists industrial achievement award for 1996, and is a topic on which many review and popular articles ( Frampton, 1988 Sperber, 1992 Sastry, 1994 Rice, 1995 Larkin and Spinak, 1996 Reznick, 1996 Zoltai and Swearingen, 1996 Ruan et al., 2001 Sastry, 2005) have been written. It is a technology which was awarded the U.S. Ohmic heating is a term used to describe direct electrical resistance heating of food products. Liquid cooling requires a sealed circulation of the coolant, therefore a more sophisticated cartridge to accommodate the capillary column. On the other hand, air cooling requires less complex instrumentation, particularly with regard to the capillary cartridge. For CE separations involving high currents, liquid cooling is more efficient than air because liquids have a higher thermal capacity. In gas cooling, air is typically the coolant (followed by nitrogen), while liquids based on perfluorinated compounds are used for liquid cooling. In commercial CE systems, the temperature control of the coolants is commonly performed by a Peltier system. Dissipation of the heat and the temperature control of the capillary is usually conducted using cooling systems based on the forced circulation of gas or liquid around the capillary column. Nevertheless, temperature control is still essential to achieve efficient and reproducible separations in CE. The use of capillary columns of small internal diameter reduces the Joule heating effect. As temperature affects the viscosity of the BGE and the diffusion coefficients of analytes, Joule heating is a source of variation in migration times and band broadening. The portion of the BGE close to the capillary wall dissipates heat faster than that in the central region, producing a gradient of temperature with a parabolic profile in the radial direction of the capillary. The heat dissipation across the capillary occurs in a nonuniform way. Joule heating is inherent to the CE separation process because of the electric current established across the capillary column. Coltro, in Capillary Electromigration Separation Methods, 2018 11.4 Temperature Control
Overall, induction heating methods offer no advantage over joule heating, save the ability to use rectangular, disk or cylindrical specimens, rather than wire, ribbon or foil samples.Ĭyro L.S.
Thermocouples will suscept in the RF heating field and thus temperature measurement and control depends on pyrometry, similarly to the joule heating approach.
Induction heating provides more freedom in the design of samples, but still requires that temperature cycling rate depends on the sample heat capacity and again control and measurement of sample temperatures is difficult. For non-conducting materials or samples of complex shape, a secondary susceptor can be used, but its heat capacity can limit heating and cooling rates that can be achieved. Like joule heating, induction heating is also limited to electrically conducting samples if rapid heating and cooling cycles are to be achieved. HOJDA, in Novel Approaches to Improving High Temperature Corrosion Resistance, 2008 20.2.2 Induction heating