| 摘要: |
| 热泵热水器中制冷剂与水换热而将其加热至60℃，结垢严重。为抑制污垢，分别在0.5和1.0mmol/lCaCO3溶液中，通过静态反应法使污垢在不锈钢表面生长，分别用称重法和SEM获得不同浸入时间的结垢重量和污垢的微观形貌。结果表明：相同条件时ss304表面比ss316更易结垢且前者易形成文石而后者易形成方解石；Ca2+浓度较高使本体溶液均相成核率和表面异相成核率均增大而产生更多晶核，但单个晶体尺寸减少、结垢重量降低且不影响晶型种类比例；pH升高不仅使本体溶液中均相成核率和表面异相成核率均增加，且均相成核率增加更多，导致结垢量降低，并促进方解石的形成。换热器表面析晶污垢形成的主要机理是难溶盐分子先在溶液内形成污垢颗粒，而后沉积到表面上，而不仅通过在表面的反应和吸附而直接形成。 |
| 关键词: CaCO3析晶污垢 挂片实验 晶体形貌 成核率 |
| DOI： |
| 投稿时间：2012-06-06
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| 基金项目: |
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| Effect of Concentration and pH onFouling Growth on Stainless Steel in Heat Pump Water Heater |
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Sheng Jian, Zhang Hua, Zhao Ping
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| (School of Energy and Power Engineering, University of Shanghai for Science and Technology) |
| Abstract: |
| Water is heated to 60℃ by refrigerant in heat pump water heater, which results serious fouling . Studying the precipitation characteristics are the first step to find anti-fouling technology. CaCO3 is precipitated on stainless steel 304 and 316 coupons from 0.5 and 1.0 mmol/l CaCO3 solution by static reaction. By weighing the coupons before and after experiments the mass of fouling is obtained and the morphology of different grown time coupon surfaces can be got using SEM. The results show that at the same condition there was more fouling on ss304 than ss316 and more aragonite on ss304 and more calcite on ss316. Higher Ca2+ concentration formed more nuclei but the sizes of the nuclei was decreased and less fouling was formed for each nuclei, and the proportion of aragonite and calcite wasn’t changed. Higher pH promoted formation of calcite and both homogeneous and heterogeneous nucleation rate, but the former increased more, so the fouling mass decreased. The main mechanism of fouling formation on heat exchanger surfaces was insoluble salt crystallization to form fouling particles in solution and then precipitate on surface, reaction and adsorption of insoluble salt directly to surface is the secondary mechanism. |
| Key words: CaCO3 crystallization fouling Coupon test Crystal morphology Nucleation rate |
