Heat Transfer Coefficients of Moving Particle Beds from Flow-Dependent Particle Bed Thermal Conductivity and Near-Wall Resistance
arxiv(2024)
Abstract
Determination of heat transfer coefficients for flowing packed particle beds
is essential to the design of particle heat exchangers, and other thermal
processes. While such dense granular flows fall into the well-known plug-flow
regime, the discrete nature of granular materials alters the thermal transport
processes in both the near-wall and bulk regions of flowing particle beds from
their stationary counterparts. As a result, heat transfer correlations based on
the stationary particle bed thermal conductivity could be inadequate for
flowing particles in a heat exchanger. Earlier works have achieved reasonable
agreement with experiments by treating granular media as a plug-flow continuum
with a near-wall thermal resistance in series. However, the properties of the
continuum were often obtained from measurements on stationary beds owing to the
difficulty of flowing bed measurements. In this work, it was found that the
properties of a stationary bed are highly sensitive to the method of particle
packing and there is a decrease in the particle bed thermal conductivity and
increase in the near-wall thermal resistance, measured as an effective air gap
thickness, on the onset of particle flow. These variations in the
thermophysical properties of stationary and flowing particle beds can lead to
errors in heat transfer coefficient calculations. Therefore, the heat transfer
coefficients for granular flows were calculated using experimentally determined
flowing particle bed thermal conductivity and near-wall air gap for ceramic
particles -CARBOCP40/100(275 um), HSP40/70(404um) and HSP16/30(956um); at
velocities of 5-15mms-1; and temperatures of 300-650C. The thermal conductivity
and air gap values for CP40/100 and HSP40/70 were further used to calculate
heat transfer coefficients across different particle bed temperatures and
velocities for different parallel-plate heat exchanger dimensions.
MoreTranslated text
AI Read Science
Must-Reading Tree
Example
![](https://originalfileserver.aminer.cn/sys/aminer/pubs/mrt_preview.jpeg)
Generate MRT to find the research sequence of this paper
Chat Paper
Summary is being generated by the instructions you defined