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Top1. Introduction
The history of using solar energy in Algeria backs to 1954 with the solar furnace built by the French for ceramic fabrication purpose. The insulation time over the quasi totality of the national territory exceeds 2000h annually and may reach 3900h (high plains and Sahara). The daily obtained energy on a horizontal surface of 1m2 is of 5kWh over the major part of the national territory, or about 1700 kWh/m2/year for the North and 2263 kWh/m2 /year for the South of the country (Stambouli, 2011).There are many good methods and sources used to store warm thermal energy. These include solar heaters, solar ponds, geothermal storage methods, and many others. The advantage of warm thermal energy storage is that usually, the warm thermal energy storage is obtained from an abundant and ecologically friendly source, such as the sun. As a result, heat storage is usually very cost friendly and good for the environment (Rao, 2010).
Water heating using domestic solar water heaters is the most feasible, economical and popular means of solar energy utilization in many countries in the world. Consequently, the world market for their utilization has expanded significantly in recent years. A solar domestic heating water system consists of solar collector, thermal reservoir, auxiliary heater, heat exchanger, and a series of junction tubes which connect solar collector into storage tank (Dehghan, 2011; Hossain, 2011). The majority of the domestic solar water heater systems use flat plate collectors, which are connected to vertical or horizontal storage tanks (Huang, 2010; Bhutta, 2012).
Heat storage tank is a key part of a domestic solar water heater which stores thermal energy in the form of hot water during the day-time and delivers it on demand (Thulasi, 2011). Mantle heat exchangers, which are also known as annular or jacket heat exchangers, are a low cost alternative for collector loop heat exchangers (Too, 2009). The schematic layout of a thermosyphon solar water heater tank developed by UDES is shown in Figure 1.
Figure 1. Schematic layout of a thermosyphon solar water heater tank with a mantle exchanger
Application of simulation software based on various mathematical methods (FEM, FDTD, etc.) for modeling of various physical processes for research and education purposes has grown rapidly in recent years. Although researcher is able to solve various problems analytically or using various approximations, when the problem becomes too complex, he needs to use numerical calculations to obtain a solution. COMSOL Multiphysics is finite element based unifying multiphysical simulation environment. The COMSOL Multiphysics simulation environment facilitates all steps in the modeling process-defining the geometry, specifying the physics, meshing, solving and then post-processing the results. Model set up is quick, thanks to a number of predefined modeling interfaces for applications ranging from fluid flow and heat transfer to structural mechanics and electromagnetic analyses (Togni, 2008; Kristinof, 2010).