An experimental study was executed using a small model pond to examine the
erosion phenomenon on the gradient zone of a solar pond. By means of observ
ing the flow pattern of the heat reserve zone, it was made clear that the e
rosion was caused by naturally occurring convection, which is based on the
vertical temperature difference in the heat reserve zone. In other words, t
he ruling factor in erosion is the vertical temperature difference in the h
eat reserve zone. With regards to a real solar pond, a policy was proposed
which suppresses erosion velocity by controlling the pond's operating condi
tions while keeping the temperature gradient of the non-convection zone (NC
Z) as large as possible and making the vertical temperature difference in t
he heat reserve zone small. On analysis, the rational modification was effe
cted by the Grashof number Gr, which is a dimensionless number and shows th
e influence of the flotage on the speed field and the temperature field. As
a result, it was found that the modified dimensionless Grashof number expl
ains the erosion velocity of the gradient zone well. Moreover, the function
of the correlation between the erosion velocity and the modified Grashof n
umber was obtained by regression calculation and could estimate the erosion
condition of the gradient zone quantitatively. (C) 2001 Published by Elsev
ier Science Ltd.