The horizontal thermal storage tank with heat pipe which is suitable for the sensible heat storage system is able to store a hot water from the heat source such as heating pad efficiently and to supply a hot water to load rapidly. And arrangement of heating pad play an important role in thermal flow and thermal storage efficiency. In this experiments, number of heating pad is ranged from three, five and nine, and when there is no change on number of heating pad, arrangements are two types of concentration-type and dispersion-type. Strong entrainment take place in the case of concentration-type of heating pad, and rapid temperature rise(${Delta}{doteqdot}1.6{sim}3.2^{circ}C$) in the tank is obtainable on the concentration-type than dispersion-type. In the constant number of heating pad, the concentration-type has the higher efficiency with about $5{sim}6%$ than the dispersion-type Therefore, concentration-type of heating pad is an efficient design in constant number of heating pad.