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Energy storage is very important for the success of any intermittent energy
source in meeting load demand. It has been noted that the storage system acts as a
buffer medium between the collection system and the application. In the stratified
storage systems, it is possible to store both the hot and cold fluids in a single tank.
The principle is based on the gravity separation of fluids of different density. This
natural process creates a transition zone temperature gradient between cold and hot
water zones, known as thermocline. A two tank system for storing hot and cold
fluids separately may also be used; but, this requires
two tanks for a given volume of water. Several people have experimentally and theoretically analyzed the process
of stratification in different geometries, inlet and outlet locations, different tank
wall materials, different flow rates, etc. The studies are mainly concentrated on
static stratification, charging and discharging cycles.
Lavan and Thomson (1977) conducted experiments in tanks having different L/D ratios. They found that L/D = 3.0 is optimum for better performance. Shyu et al. (1989), Vedamurthy (1989), and Ambaprasad Rao (1992) studied experimentally
the effect of interior lining on the stratification. They concluded that the outside
insulation can enhance the tank wall axial
conduction, which tends to degrade the
stratification. All these studies are mainly concentrated on static stratification, charging and
discharging cycles.
In the present investigation, experiments were carried out on two
tanksone lined inside with rubber and other with fiber glassto study the effect of
thermal conductivity of the lined material with a central inlet system. In addition,
experiments were carried out in static as well as dynamic modes to see the feasibility of
stratification under dynamic conditions. |
