Analysis And Control Method Of Corrosion Of Heat Exchanger In Surface Water Source Heat Pump

China is in a period of rapid economic development, energy demand and consumption is increasing year by year. As an effective means of recovery and utilization of low-grade heat energy, surface water source heat pump can provide heating and cooling service for summer and winter. There is a significant environmental, social and economic benefit. Several rivers flows through Chongqing, the main rivers are the Yangtze River and Jialing River. Making use of river water as water source, the corrosion, wear and clogging of the heat exchanger heat pump units which are caused by water quality are needed to be done, because of reducing heat transfer efficiency. Secondly, sediment of water will precipitate and adhere to form a scale layer while flowing. Copper is widely used for its electrical and thermal conductivities in heat exchangers. But it exhibits corrosion by ion coordination in the water with oxygen and corrosive ions. Thus, passivation action was used to inhibit corrosion of copper is a very cost-effective approach.Based on the analysis of composition of fouling layer in heat exchanger and water quality, corrosive factors was studied using red copper for the object in the condition of water quality. Added copper sulfate, hydroxyl ammonium sulfate and ionic liquids to the conventional corrosion inhibitor of BTA,to form the passive film on the surface of copper. Then the characteristics of the layer were studied.Solutions presented in this thesis can be summarized as follows:1. After monitored and analyzed pH, chloride, sulfate, calcium and magnesium ions, ammonia, and ferrous iron content the river water quality about two years. The river water quality was found that, the average content of pH 7⁸,chloride ion is less than20 mg/L,sulfate ion is less than 100 mg/L,ferrous ion is less than 0.5 mg/L,ammonia-N is less than 3 mg/L,electrical conductivity is less than 0.5μs/cm. In addition to calcium and magnesium hardness had exceeded the total allowable value sometimes; the other indexes could reach the quality requirements of water source heat pump in each section and every month relative stably.2. Analyzed phase of fouling layer on the heat exchanger by XRD showed that the main ingredient was silicate, calcium, and magnesium. The sediment is easily deposited on the copper while water circulated in exchanger. To avoid this, it should be pay attention to location of fetching water and sediment removal in the operation. 3. Electrochemical tests showed that the pH value in water, corrosive ions, water temperature had an impact on the corrosion rate of copper without passive film. The corrosion potential of copper electrode shifted negatively and corrosion current density increased in acidic (pH6.5) and high temperature (40℃). Water quality of each section did not differ significantly throughout the corrosion of the electrodes.4. Electrochemical analysis of the performance of passive film investigated, BTA in the synergistic effect of copper sulfate and hydroxyl ammonium sulfate could form a passive film completely on the surface of copper electrode. The corrosion potential shifted more positive and corrosion current density reduced, it effectively slowed down the corrosion rate. Adding ionic liquids ([Bmim] BF₄) made the stability of mixture poorly and reflected on inhibition not obvious effective.