Numerical investigation on the improvement of the thermal efficiency of a household gas water heater and verification of its results with the experimental results

In this research for the aim of optimizing of the gas consumption, increasing of the thermal efficiency of a household gas water heater has been investigated numerically. The optimal design and configuration of the baffles in the middle tube of the gas water heater prevents the quick exit of the exhaust gases and consequently increases the retention time of the hot gases inside the middle tube and reduces wasting of their thermal energy. The combustion process in the gas water heater is a chain process and completing of this process occurs along its path in the middle tube. Therefore for obtaining the maximum thermal efficiency, the numerical analysis of the combustion process and designing and configuration of the baffles inside the middle tube have been carried out and conducted simultaneously. The Ansys Fluent CFD code has been employed for the computational simulation of the combustion of the gas, the heat transfer from the contents of the middle tube into the water tank and distribution of velocity of the exhaust gases along their path inside the middle tube and around the baffles. Computational simulation of the problem under investigation has been carried out by considering different geometries and configurations of the baffles along the path of the heat gases. Numerical results show that the mass fraction of the methane gas and the carbon dioxide in the exhaust gases is negligible and consequently all of the methane gas has been consumed. The numerical results have been verified by the experimental results.