An economizer design and numerical analysis

The heating of boiler feed water together with waste heat and heat exchangers that provide energy recovery are called economizers. In this study, waste heat recovery methods and economizer applications are discussed in detail. Economizer design, theoretical calculations and numerical analysis were made by using the heat of the waste flue gas from the furnace. In the design, the data of the combustion test furnace used in a cable company were used. In the heat transfer from the flue gas to the water, the heat transfer rate is increased by using self-finned serpentines in the economizer design since the heat transfer coefficient on the flue gas side is very low compared to the waterside. The mean logarithmic temperature difference and ε - NTU methods were used in the economizer design calculations. As a result of the calculations, a 6-pass and 5-row economizer with a surface area of 288.24 m^2 and consisting of 120 self-finned serpentines was designed. The efficiency of the heat exchanger used in the economizer was calculated as 0.71. The material used in the pipes and fins was chosen as copper due to its high thermal conductivity coefficient. The water in the 500-liter boiler tank at 20°C was increased to 60°C in 435 seconds with the designed economizer. The combustion test furnace runs for 25 minutes for each cable group. One of the points that make the design unique is that the heat is restored to the system in approximately 7 minutes with the help of an economizer. When the economizer is included in the system, it is seen that the flue gas temperature decreases from 71.2°C to 50°C. Thus, the flue gas will be cooled and thrown into the atmosphere at a lower temperature. The designed and theoretically calculated economizer was analyzed in the ANSYS CFD program with the finite element method. It has been seen that the results of the theoretical calculations and the numerical analysis are in harmony.