Solar energy has been used widely in many industrial areas. One of the widely used solar energy applications is water heating. Energy storage is much more important where the energy source is intermittent, such as solar energy. While the water exit from the tank to usage, the temperature of the hot water in the tank stars to decrease because of the mixing of the cold water from the main lines and remaining hot water in the tank. In this work, using of the some obstacles has been suggested to supply higher thermal stratification in the tank during the water usage from the tank.

There is some previous analysis about these subjects as; ALIZADEH, has investigated the thermal behavior of a horizontal cylindrical storage tank. He used one dimensional the Turbulent Mixing Model and Displacement Mixing Model in numerical calculations. He has used some models to prevent unsteady behavior of the vertical temperature distributions [1].

AL-NIMR has solved and presented some mathematical models to determine the effect of the different design parameters on the thermal stratification within the tank and the time required by tank to supply water within a specified outlet temperature [2].

MISRA has analyzed the thermal stratification both theoretically and experimentally in hot water storage tank for the thermosyphon effect in solar water heating systems. He has given the analytical expressions to obtain temperature distributions in the tank. He has also given the diagrams depends on the time to present conductive heat transfer between the layers in the storage tank [3].

HELVA ad MOBARAK have investigated the effect of the amount of the hot water using into the temperature distribution in solar water heating storage tank [4].

HARIHARAN and BADRINARAYANA have analyzed the thermal stratifications numerically and experimentally in the hot water storage tank. They have studied the effect of surrounding and operating conditions into the thermal stratifications. They have observed that stratification improves with increasing AT and water flow rates [5].

HAHNE and CHEN have studied numerically about the flow and heat transfer characteristics in a cylindrical hot water store. They have used the storage efficiency to obtain thermal stratification. They have found that the increase of the Richardson and Peclect number has an effect that increases the storage efficiency [6].

Mo and MIYATAKE have carried out the transient numerical analysis for the thermal stratifications in the storage tanks. They have used turbulence model (k-s model). They have presented the effect of exchange cold water with hot water into the thermal stratifications [7].

EAMES and NORTON have investigated the effect of the tank geometry into the thermal stratification for sensible heat storage for low Reynolds number. They have presented the effect of inlet and outlet port locations on store performance [8].

In this study, the effect of the using some different obstacles for obtaining higher thermal stratifications has been analyzed numerically. The different kinds of obstacles are placed in the cylindrical tank to get the best performance for thermal stratifications inside the tank between all investigated cases. The water has been used as fluid.