| As an effective use device of renewable energy,flat plate solar collector is widely used in the transformation and utilization of solar energy.It transfers heat energy through the operating fluid in the collector tube to the heat-exchange equipment through the absorber plate.In this process,the fluid in the tube works for a long time so that Carbonate-based impurities largely accumulate in the tube,which not only reduces the heat transfer efficiency,but also easily leads to corrosion and leakage of the pipeline.In previous studies,the overall calculation method was the main method for carbonate fouling.However,in complex structures and minim channels,the calculation error of this method was large.Therefore,the local fouling method was introduced to calculate the fouling deposition.In this paper,according to the local deposition of calcium carbonate fouling in the flat plate solar collector,the physical parameters of the grid cells near-wall region in the fluid domain are extracted by user defined functions,and the velocity,temperature and calcium carbonate concentration are corrected according to the actual situation,and the deposition in various enhanced tubes is described in detail.Firstly,according to the description in the experimental literature,the simulation value is compared with the experimental value to verify the accuracy of the calculation method of local fouling.Secondly,the physical models of smooth tube and four kinds of enhanced tube are established and simulated.Select the same length of pipe segment to compare the local fouling thermal resistance distribution with the length of pipe segment,and use the local distribution diagram of wall shear force to discuss.At the same time,it shows the advantage of local fouling method in quantitative analysis of fouling thermal resistance distribution in a certain local region of the model.Secondly,after selecting corrugated tube as the type of enhanced tubes with the best scale inhibition fouling effect,the overall value of bellows fouling thermal resistance under different working conditions was calculated.The results show that the overall value of fouling thermal resistance decreases with the increase of inlet velocity,decreases with the increase of wall temperature,and increases with the increase of calcium carbonate solution concentration.Finally,the influence of the height,width and spacing of corrugated tubes on the distribution of local fouling thermal resistance is studied on the premise that other conditions remain unchanged.The results show that the overall thermal resistance of fouling decreases with the increase of the bump height in the range of 0～4 mm.In the range of 6～14 mm,the overall value of fouling thermal resistance increases with the increase of the width of the tube.In the range of12～20 mm,the overall value of fouling thermal resistance increases with the increase of the spacing between the tube. |
