Bioprocess heat transfer

Heat transfer (heat transmission) is an important unit operation in chemical and bioprocess plants. In general, heat is transferred by one of the three mechanisms, namely, conduction, convection, and radiation, or by their combinations. However, we need not consider radiation in bioprocess plants, which usually operate at relatively low temperatures. The heating and cooling of solids rarely become problematic in bioprocess plants. 

The viscosity of a bioprocess liquid is an important factor, affecting mass transfer, heat transfer, and power consumption. It is affected by the concentrations and types of microorganisms, substrates, products, and solids present in the liquid, and can vary during a fermentation or separation process. Unfortunately, on-line viscosity measurements are difficult, especially when significant amounts of air bubbles and suspended solids are present, and thus viscosity probes are not in widespread use. Sensors that have been applied for viscosity determination (usually in laboratory studies) are often various types of rotational viscosimeters [42]. 

To evaluate the parameter for heat transfer (the heat transfer coefficient, [kJ/m h °C]), one can begin with Equ. 3.69, which refers to an exothermic bioprocess neglecting the last four terms one obtains Equ. 3.71... 

If you look closely at this equation and Fourier s law of heat transfer, they look very similar. This similarity is not casual because Pick s observations, based on mass transfer, gave similar results to those observed for heat transfer. This similarity among heat, mass, and momentum transfer are very relevant for chemical and bioprocess engineering and makes it possible to group them into the so-called discipline of transport phenomena. 

As you will see, most of the quantitative problems in the following sections are concern ideal gases and just a glimpse of material balance. The next chapter is devoted entirely to material balance. Here, the introductory parts on thermodynamics, heat transfer, and mass transfer were included to acquaint you with the chemical and bioprocess engineering world conceptually, but not quantitatively. 

Sideman S, Pinczewski W (1975) Turbulent Heat and Mass Transfer at Interfaces Transport Models and Mechanisms. In Gutfinger C (ed) Topics in Transport Phenomena bioprocesses, mathematical treatment, mechanisms. Hemisphere, Washington... 

Figure 2.3. The macroscopic principle applied to bioprocessing expressed with pseudohomogeneous observable process variables in the liquid phase (L) biomass X, substrates S-, oxygen 0, products Pj, carbon dioxide C, and volumetric heat Hy. Pseudohomogeneity is checked by considering a series of mass transfer steps L film at the gas phase-L interface (1), L bulk (2), L film at the L-Solid phase (S) interface (3), cell wall and membranes (4), resp. S-phase cell mass with cytoplasm.

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