## Dissertations from ProQuest

#### Title

Forced convection heat transfer in microen-capsulated phase-change material slurries

1989

Article

#### Degree Name

Doctor of Philosophy (Ph.D.)

#### Department

Mechanical Engineering

#### First Committee Member

Subrata Sengupta, Committee Chair

#### Abstract

The heat transfer characteristics of microencapsulated phase change material slurry flow in circular ducts and parallel plates has been investigated. The formulation of the energy equation includes the heat source which represents the heat generation (or absorption) due to phase change in the suspended particles (i.e., the microcapsules). It also takes into consideration the thermal diffusivity enhancement created by the motion of the fluid around the particles. The effective thermal conductivity of the bulk fluid is expressed in terms of the particle concentration and the particle Peclet number. The heat source function in the energy equation was derived from a solution for the freezing or melting in a sphere. The governing parameters which can be identified from the formulated equations are the particle concentration; the bulk "Stefan number"; the duct/particle radius ratio; the particle/fluid thermal conductivity ratio; and the modified Peclet number, $\rm Pe\sb{f}(R\sb{p}/R\sb{d})\sp2$. The effects of these parameters on the heat transfer characteristics were studied numerically for constant wall temperature and constant wall heat flux boundary conditions in the parameter ranges typical to low temperature applications (i.e., for materials with melting temperature below 100$\sp\circ$C). It was found that the most dominant parameters are the concentration and the "Stefan number". The effects of the radius ratio and $\rm Pe\sb{f}(R\sb{p}/R\sb{d})\sp2$ are relatively weak. The effects of the conductivity ratio are very small and may be dropped from the parameter set in the ranges of parameters considered. The results show that the Nusselt number in the slurry flow is about 1.5 to 3 times that of the pure fluid and the wall to fluid temperature difference is increased about 1.5 to 2.5 times.

#### Keywords

Engineering, Mechanical