ABSTRACT
Experiments are carried out to investigate the recovery of energy and exergy from
packed bed thermal storage systems. Measurements of the time dependent temperatures at
different axial and radial positions as well as the axial pressure distribution are performed
inside two cylindrical packed beds with 0.15 and 0.25 m inside diameters, respectively.
Rock grains of two irregular sizes ranging between 15 to 20 mm and between 30 to 35 mm,
respectively, are packed inside the beds at different aspect ratios ranging from 1.0 to 4.5.
The temporal recovered energy, exergy, system recovery and overall (charging/recovery) 1st
and the 2nd law efficiencies are calculated utilizing the present measurements in addition to
the charging data which are previously published by the author. The influence of air mass
flow rate, bed initial temperature, bed diameter, bed aspect ratio, and packing grains size on
the system storage and recovery characteristics are investigated. The present results for
system overall charging/recovery 1st and the 2nd law efficiencies are correlated as functions
of the different operating and design parameters