Thermal convection in a uniformly heated fluid between vertical parallel plates

摘要

In methods of continuous‐flow‐deviation electrophoresis, a basic element of the apparatus is a conductive fluid sheet sandwiched between two closely spaced parallel vertical plates which are maintained at a constant temperature while the fluid is uniformly heated by an electric current flowing parallel to the plates. A horizontal temperature gradient is established with a maximum temperature in the midplane of the fluid sheet. The velocity distribution of the resulting thermal convection is calculated in two steps: (1) in the general case for plates whose separation is negligible compared to their lateral dimensions, and (2) for the physical conditions encountered in fluid‐sheet electrophoresis which justify the approximations that the effect of viscosity variations is negligible and that the density is a linear function of temperature. The resulting expression for the velocity distribution is a fourth‐order polynomial inz(distance of a point from the midplane between the plates). The function has three extrema—a positive one at the midplane and two negative ones intermediate between the central plane and the walls.