Experimental Study On Heat Transfer Performance Of Vertical Condenser With Trisection Helical Baffles

Comparing with horizontal condensers, vertical condensers have advantages such as small occupied area, simple structure, convenient in dragging tube bundles out in maintenance etc. However, due to traditional vertical segment baffle condensers have drawbacks of condensate gathering on tube outside under the action of gravity, condensation heat transfer thermal resistance quickly increases along tube surface, resulting in the shell side heat transfer coefficient is much lower than that of horizontal condensers, which limits the application of vertical condensers. Therefore, strengthening the vertical condenser tube outside condensation heat transfer has great value in the power generation industry to promote the application of vertical feed water heaters.Based on the trisection helical baffle heat exchanger, the trisection helical baffle vertical condenser scheme has been put forward by this research group. The scheme aims at the high and low pressure feed water shell and tube heaters to enhance shell side condensation. In the vertical shell, the circumferential overlapped trisection helical baffles are arranged around tubes, which are divided into short segments, the inclined baffle has the "drain" function that the condensate from the tube surface will be continuously scraped. The steam flows through the spiral channel guided by the helical baffles. At the same time, the liquid dam is set on the baffle downstream edges and the drainage gaps are set on the curve edge of baffle, for timely draining the condensate from the tube surface flowing along the inner wall of the shell into the bottom of the heat exchanger. By effective thinning film thickness of the condensate on the heat transfer tube wall, the quantity of the condensate could be increased and heat transfer coefficient improved.In this paper, method integrating numerical simulation and experiment is used to study the heat transfer performance of vertical condenser with trisection helical baffle.Studies are mainly focusing on following aspects:Participated in the erection and commission of the experiment installation of trisection helical baffle condenser. The test system adopts a single pressure closed thermosyphon loop, generating steam from an electric heated evaporator of lower position, the vertical condenser is in higher position, the steam enters into the testing condenser shell and flow from top to bottom along the spiral channel during condensation process, while the cooling water flow along the tube side from bottom to top and carries heat away. The condensate returns to the lower position inlet of electric heated evaporator through a liquid storage tank, which is used for stabling the water level in the evaporator. The heat transfer properties of variable angle double thread helical baffle vertical condensers with and without liquid dams were investigated respectively, and compared with those of a traditional segment baffle condenser. The results verified that the steam in trisection helical baffles condenser flowing with spiral channel along baffle plates can strengthen the fluid scouring the tube wall surface, reduce the film thickness; and the gradually reduced incline angle of baffles can remediate the reduced steam volume flow rate during condensation to prevent the reduction of velocity by decreasing the tubes span accordingly between baffles. The bent baffle plate at downstream edge with a liquid dam and setting drainage gaps on the curve edge of baffle can effectively drain and guide the condensate flowing to the shell wall, and avoid to be entrained into steam, thereby enhance condensation heat transfer of tube buddle in shell side. The experiment results show that the shell side heat transfer performance of variable angle double thread helical baffle condenser with liquid dams and drainage gaps is the best.