Research On The Heat Exchanges Of Urban Original Sewage By Fouling

Water source heat pump systems is an effective use on renewable energy and low-heat, that also has a significant advantage on technical, economic and energy. But the presence of fouling during the heat exchanges significantly reduces the efficiency of the system. The affect on heat exchanger of water source heat pump by fouling growth on the heat exchanger equipment is the key to understand and solve the problem. In the meantime, research have already started, which focus on studying the impact on the growth characteristics of fouling and the heat exchanger through experiment or measurement basically from a macro perspective without considering on a microscopic perspective.This paper focuses on the problem such as sewage pollution of heat exchanger equipment, the fouling growth characteristics, fouling resistance and thermal conductivity and the effect on the heat exchanger by steady growth of fouling,aiming to provide a basis on prevent and remove the fouling from the microscopic into the fouling to study the effects of dirt on the water heat exchanger.The fouling growth characteristics is the basis of this paper. The paper takes biofilm CA-model as a basic model.According to the tube fouling growth conditions, we corrects the model. The paper calculates the change of parameters during the biofilm growth process using the corrected model, and analyzes the factors that influence the biofilm thickness variation.The thermal conductivity of the biofilm is the content must be studied to learn the fouling resistance growth model. The paper introduces fractal theory and defines Biofilm porosity fractal dimension and constant change. According to the microscopic structure of the biofilm, the paper bulids the biofilm resistance profile model and learns the biofilm thermal conductivity formula by applicating the thermal model approach. The paper analyses the fouling resistance growth model by the study on biofilm growth model and the biofilm thermal conductivity values.The effect of the heat exchanger by the stable fouling layer is also studied in this paper.By comparing the experimental and model, we find the fouling resistance is not the only factor on heat exchanger. The paper demonstrates the biofilm fouling layer can be researched as a rough wall. Further study gives the conclusion that stable biofilm layer play a role in enhancing on the heat exchanger. To describe the enhancing,this paper uses the equivalent thickness as a description object. Thus, the equivalent thickness can also define the effect on the heat exchanger by the fouling growth with the biofilm thickness.In a word, the paper puts forward that combining with the rough wall theory and the biofilm thermal resistance model can analyze the impact on the heat exchanger during the fouling growth process. It may be helped to provide a basis on prevent and remove the fouling.