Exergy analysis of two novel all-welded plate air preheaters

摘要

With the stricter requirements for energy saving and emission reduction, air preheaters have always been the focus of scientific research, especially the development of plate air preheaters with high compactness, good heat transfer performance and reduced media flow pressure has a sharp upward trend. At present, there are two kinds of plate type air preheaters on the market, one is popular in the market for welding support points between plates, or the Stubs-inserted Plate Air preheater (SIPA); the other is the Corrugated Plate Air preheater (CPA). In order to evaluate the thermodynamic performance of the two series of air preheaters, this paper analyzes the exergy loss of the CPA and SIPA through experimental research. Experiments were conducted where environmental air was heated by high-temperature flue gas produced from the burning of natural gas. Variations in the effectiveness and dimensionless exergy losses of the air preheaters according to gas flow rates are compared. The temperatures of the inlet air and flue gas were kept constant at 30 degrees C and 300 degrees C, respectively. The Reynolds numbers varied from 2.95 x 10(3) to 5.47 x 10(3) for air and 2.01 x 10(3) to 3.14 x 10(3) for flue gas. The experimental results show that the number of heat transfer units and the effectiveness of the CPA were much higher than those of the SIPA under the same conditions. The maximum and minimum values for the CPA were 0.564 and 0.438, respectively, and were 0.337 and 0.232 for the SIPA. Simultaneously, the exergy losses of both air preheaters increased with increases in gas flow. The CPA had a higher value than the SIPA but smaller dimensionless exergy losses under the same conditions, which indicates that the SIPA had greater irreversibility than the CPA at the same heat transfer rate. In consideration of its thermodynamic characteristics, the heat transfer performance of the CPA is superior to that of the SIPA.