Simulation study on combustion system of tankless gas water heater

This paper simulates the combustion system of a regular tankless gas water heater under different static pressure conditions. The simulation results are in accordance with the test results. It proves that the used physical and mathematical models are reasonable. The results show that the flame height and the excess air ratios depend on the system pressure drop but not on the absolute pressure at the combustion chamber. The pressure drop and the amount of combustion air have an inverse relationship with CO generation, and they also impact on the temperature and velocity fields. To reduce CO emission, a stronger fan is needed to provide extra pressure head to ensure that enough combustion air is introduced into the system. This study provides a useful research tool to develop products through computational fluid dynamic analysis and laboratory testing.