Investigation on Heat and Mass Transfer in a Evaporator of a Capillary-Pumped Loop with the Lattice Boltzmann Method: Pore Scale Simulation |
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Authors: | Yimin Xuan Kai Zhao Qiang Li |
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Institution: | (1) School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074, People’s Republic of China;(2) Department of Mechanical Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8561, Japan; |
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Abstract: | A two-dimensional transient numerical model based on the lattice Boltzmann method (LBM) for the global evaporator of a capillary-pumped
loop (CPL) is proposed to describe heat and mass transfer with evaporation in the porous wick, heat conduction in the cover
plate, and heat transfer in the vapor groove. To indicate the stochastic phase distribution characteristics of most porous
wick, the quartet structure generation set (QSGS) is introduced for generating more realistic microstructures of porous media.
By using the present lattice Boltzmann algorithm along with the porous structure, the heat and mass transfer of an evaporator
on pore scale can be predicted without resorting to any empirical parameters determined case by case. The energy equations
for entire evaporator are solved as a conjugate problem, which are solved by means of a spatially varying relaxation time
in the lattice Boltzmann model and the liquid flow is driven via the interfacial mass flux. A convective boundary condition
considering the latent heat during the evaporation on the interface is introduced into the lattice Boltzmann model based on
the nonequilibrium extrapolation rule. Especially, the bounce-back rule and the equilibrium rule of the LBM are, respectively,
introduced to deal with the momentum boundary conditions inside the porous wick and on the evaporation interface in order
to ensure the stability and the efficiency of the LBM model. Numerical results corresponding to different working conditions
and different working fluids are presented, which provide guidance for the evaporator design of a CPL system. |
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