Estudo experimental de transferência de calor em leito fluidizado com resistência elétrica imersa

Abstract

Fluidization is a process in which an agglomerate of particles takes on characteristics of a fluid, due to its direct interaction with an ascending gas or liquid. When applying a heat source inside the system, it is observed that the suspended bed becomes an efficient means to transfer thermal energy, presenting very small temperature gradients as a result of the intense movement of the particles. This process has gained ground in several industrial segments, as in the case of drying and roasting of grains, as well as in the energy recovery of heated particles, among others. The present work aims to study the suspensionsurface heat transfer using an electrical resistance immersed inside a bubbling fluidized bed composed of glass spheres or quartz sand. The results in the steady state showed a variation of the heat transfer coefficient between 225 W/(m²K) to 379 W/(m²K) for quartz sand particles and 261 W/(m²K) to 396 W/(m²K) for the glass spheres. In addition, the presence of higher coefficients was verified for the particles of smaller diameters, in addition to optimal fluidization velocities close to 3.00 for quartz sand 𝑑𝑝 = 0,196 mm and glass spheres 𝑑𝑝 = 0,447. Finally, it should be noted that the immersed resistance method makes it possible to determine, with good approximation, the value of the heat transfer coefficient in a bubbling fluidized bed with a leaner experimental setup.