Fouling Research Of River Water Source Heat Pump Heat Exchanger

River water-source heat pump is a renewable energy technology. As the influenceof water quality, fouling may be produced in river water-source heat pump heatexchanger. And it will cause many problems such as increasing energy consumption,reducing of cooling and heating effects and shorten the service life. So the foulingresearch of river water-source heat pump has positive significance to the application andpromotion of water-source heat pump technology. In the study main factors of causingriver water source heat pump heat exchanger fouling is analysis. According to theinfluence of heat exchanger fouling growth, the water quality is judged. The effect ofwater quality index on fouling growth is analysis by experiment. And the correspondingconclusion is obtained.Yangtze River and Jialing River water quality characteristics in Chongqing isanalysis from four respects of sediment concentration, turbidity, grain size of sedimentand other indexes. Seasonal change of sediment concentration and turbidity in the tworivers is obviously. And both of sediment concentrations are not satisfied therequirement of water source heat pump system. At the respect of sediment grain size,river sediment grain size is very small, it is mainly the clay of the fine particles. Smallsediment particles are found the key factors of effecting river water-source heat pumpfouling growth by analysis. Sediment concentration, turbidity and grain size of sedimentreflect the sediment particles in the river.50group water samples of different sedimentconcentration and particle size are making up, according to packets the different particlesize of samples, Fitting curve equations of the relationship between turbidity, sedimentconcentration and the sediment particle size are obtained. The results show that:established forecast turbidity sediment method by taking the median particle diameterd50as particle mean diameter can more accurately reflect three relations of the turbidity,sediment concentration and sediment grain size.Evaluation criteria of5water quality indicators （PH, iron ions, sedimentconcentration, turbidity, conductivity）which have impact on river water-source heatpump heat exchanger fouling are analysis. On this basis, in terms of making river water-source heat pump heat exchanger fouling, water quality of Yangtze River at differentmoment is analysis by fuzzy comprehensive evaluation. The result showed that: interms of the water quality, as the water source of water source heat pump, Yangtze River water quality is not up to standard requirements and need water treatment beforeentering the unit. In flood season, as the sediment concentration and turbidity inparticular large, is not conducive to direct system and easy to cause fouling of heatexchangers. From the influence degree of the river water each index and relatedresearch and national standards each index caused by heat exchanger fouling indexcritical value in two aspects definition of comprehensive water quality parameters forthe fouling potential （WSP）, according to the existing data analysis formula.Build the water source heat pump system experiment platform, the experimentalconfiguration of3kinds of different grain size of sediment sources, median diameter ofd50were5.01μm,10.98μm and22.90μm. Through the experimental results, the watermedian diameter of d50were5.01μm,10.98μm and22.90μm corresponding to the heatexchanger fouling induction period were17h,24h and32h. And the correspondingstability value of fouling thermal resistance are1.4×104（m²k）/w、1.3×10^-4（m²·k）/w and9×10⁵（m²k）/w.So water sediment particle size on induction period of foulingthermal resistance is proportional to, and the stable value inversely proportional to.When the particle size is smaller, induction period is shorter, fouling thermal resistancestable value is greater. So sediment grain size is smaller, so that the heat exchanger tubefouling is more easily formed.The experimental results respectively compare with fouling prediction model, riverwater experiment and specification manual. And compare the experimental system cleanand dirt situation, and compare experimental water sediment grain size and the currentsituation of water treatment. The results show that: when the heat exchanger tube watermedian particle size d50=5.01μm, d50=10.98μm, d50=22.9μ m, After fouling slow growthperiod, fouling resistance variation with time match with dirt progressive growthcharacteristics which is proposed by Zubair and Sheikh. Either the river raw waterexperiment or water distribution experiment, it shows that the growth of fouling isconsistent with progressive growth characteristics, and there is induction period.Comparing with the recommended value of TEMA,"Heat exchanger design handbook"and the industrial circulating cooling water treatment design specifications and otherrequirements, it is less than the river minimum fouling coefficient. In contrast to theexperimental heat pipe fouling and cleaning status, found by calculating heat transfercoefficient and system efficiency decreased by20.3%. The current water treatment ongrain size of sediment removal degree already satisfy the need of practical engineering,and should take more methods for reducing river sediment. This study deepened the river water source heat pump heat exchanger foulingresearch and make reference for engineering application and related standard.