چكيده به لاتين
In this research, after examining the types of heat exchangers, as well as studying the paper on simulations in the field of sediment formation in a variety of heat exchangers, the design, construction, and evaluation of the performance of the continuous entrainedbed fluid heat exchangere was performed to enable Investigate the ability of the entrained bed to reduce the amount of sediment formation in the heat exchanger and determine the optimal conditions for the heat exchanger to reduce the amount of sedimentation. In this type of heat exchanger, the fluid flows into a tube that has a bed of the buckshot and make the bed entrained; in this case, the bed moves along with the current. In this project, the NaClWater- solution concentration of in (16 gr NaCl) / (100 gr H2O) in 85 ° C at different speeds are introduced into the heat exchanger. Then the effect of the entrained bed (tested in several volume fractions) on the reduction of sediment formation (which is determined by weighting the heat exchanger after each test) is checked in the heat exchanger. The mechanism of reducing the formation of sediment byusing the entrained bed is such that inserting the momentum and shear stress into the the entrained bed by wall heat exchanger, separate the sediment from the heat exchanger wall; in addition, by increasing the turbulence of the flow It also reduces the amount of sediment formation. The main part of this heat exchanger is a 0.032-meter diameter tube, which is formed as a rectangular cycle and flows from one point as ajet into this heat exchanger, and most of the inlet fluid leaves the heat exchanger after full pass of the path, but The buckshot bed flows with the fluid not removed from the heat exchanger and during this process the buckshot bed flows continuously in the heat exchanger. To experimentally evaluate the performance of this heat exchanger, designing experiments and analyzing laboratory data method of the RSM has been used. In this experiment, three operational parameters affecting the performance of the entrained bed heat exchanger have been investigated: 1. Fluid velocity. 2. Mass fraction of buckshot bed in the heat exchanger. 3. Process time. Finally, an array of 20 experiments with different conditions was proposed. After performing the experiments, the optimum conditions for the heat exchanger were at 0.76 m / s and the volume fraction of the bed was 6%. Under these conditions, the amount of sediments formed in comparison with the state Heat exchanger without entrained bed is reduced by 90.5%. By examining the results of experiments, it was observed that, with increasing fluid velocity and volume fraction, the amount of sedimentation decreased, and as the process time increased, the amount of sedimentation increased (ie, the minimum sedimentation conditions occur at high velocity of the fluid and large volume fraction of the bed and low process time) .We also continued testing for the modeling of the sedimentation process for as long as the system is in deposition equilibrium, and then we compared the modeling parameters of the various experiments and other each examined the effect of variables affecting modeling parameters. p-value of model is 0.0007 and F-value is 9.85.
By reducing the amount of sediments formed, in addition to preventing the reduction of heat exchanger efficiency, the lifespan of the heat exchanger also increases.
