RESEARCH ON DEPOSITION CHARACTERISTICS OF NaCl CRYSTALS IN THE HEAT TRANSFER PIPELINES OF EXTERNAL HEAT EXCHANGERS OF SALT GRADIENT SOLAR PONDS
This paper takes NaCl solution as an example to study the NaCl deposition characteristics in the external heat exchanger heat transfer pipeline of a salt gradient solar ponds.Under the operating conditions of the salt gradient solar pond,a numerical model bosed on the coupling of turbulent flow-dilute material transfer-fluid heat transfer in pipelines has been constructed,the effects of fluid inlet velocity and inlet temperature of heat transfer pipelines on the deposition rate,erosion rate,and net deposition rate of NaCl crystal are studied by numerical simulation level set method.The research results show that:1)When the fluid inlet velocity is constant,the erosion rate increases with the increase of deposition time,but the deposition rate decreases.2)Under the premist of sufficient fluid running time,when the fluid inlet velocity increases from 0.5 m/s to 1.0 m/s,the time for negative net sedimentation rate decreases from 53 h to 24 h.From this,it can be concluded that the fluid inlet velocity should be increased without affecting the stability of the salt gradient solar pond,in order to reduce NaCl crystal deposition in the heat transfer pipeline.3)The fluid inlet temperature is positively correlated with the rate of NaCl crystal deposition.When the fluid inlet temperature increases from 70℃to 90℃maximum deposition rate increases from 0.98×10-3 kg/(m2·s)to 1.22×10-3 kg/(m2·s).To reduce NaCl crystal deposition inside the heat transfer pipeline,the fluid inlet temperature should be lowered without affecting the heat exchange efficiency of the salt gradient solar pool.
salt gradient solar pondspipeline crystallizationdeposition rateerosion ratenet deposition rate
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