燃焼ガスからの潜熱回収熱交換器の高性能化

概要

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The new type of heat exchanger, in which fuel gas flows inside thin tubes and water is shell-side, was proposed to develop the performance and compactness of shell & tube type heat exchanger for latent heat recovery from flue gas. The effects of tube diameter (1.05.0 mm) and heat exchanging length (7100 mm) on the heat transfer characteristics of a single tube were systematically investigated by measuring the gas outlet temperature, the pressure loss of the gas, and the condensation rate for moist air. It was shown that the usage of thinner tubes was remarkably effective to achieve the high performance. That is, the rapid temperature drop near inlet occurred and high heat transfer rate was realized for thinner tubes of 1.0mm and 2.0mm in inner diameter compared with thicker tubes because of small heat capacity flow rate and high heat transfer coefficient. In addition, the increase in the volumetric heat transfer area in thin tube type heat exchanger contributed to the compactness. Furthermore, although the pressure drop increased with decreasing tube diameter, it was possible to keep it within the tolerance level for the heat exchanger of domestic hot water supply for practical use because of shorter length of thin tubes. It was shown that one twentieth of heat exchanging volume was possible to be downsized by changing small tubes of 1.0mm from 5.0mm.