Effect of Ash Particles on Heat Transfer Characteristics of Condensing Heat Exchangers

Ash particles widely exist in flue gas and all kinds of dryer exhaust, which could not be neglected in the process of waste heat recovery from flue gas or exhausted gas. In this paper, for the purposed of recovering waste heat and water, wet air with ash particles was used to simulate flue gas or exhausted gas. Experiments were taken to study heat transfer characteristics for wet air containing ash particles. Heat transfer coefficients against time were obtained. Ash deposition pattern was presented. It was found that when the mainstream contained ash particles, heat transfer coefficients of wet air decreased against time and then reached stable values, presenting an index attenuation law with time. Compared to dry air, the time to reach steady of wet air was longer, the decreasing range of heat transfer coefficients was larger, and the ash deposition was more serious and mainly concentrated in the upper tubes.