Experiment And Theory Of Film Condensation Heat Transfer On Horizontal Tube Bundle

Surface condensers with vapor condense on horizontal tube bundle, such asshell and tube condenser, are widely used in energy power field, petrochemicalindustry, refrigeration and air conditioning field, desalination field, etc. thecondensation heat transfer coefficient(CHTC) on horizontal tube bundle(HTB) isthe critical infrastructure issues for the design and development of these devices.Solving this problem effectively could help to further develop relevant enhancedheat transfer technology, to research and develop high efficiency surfacecondenser independently and to improve the efficiency level of relevant systemssignificantly. However, the high complexity, high cost of experiments anddifficult to control experimental error made the development of condensationtheory for HTB quit slowly for a long time, leading to new problem solvinghighly depends on the experiment. In China, the research related to it has juststarted, and the foundation of both experimental and theoretical of it is scanty.Therefore, to promote the development of condensation heat transfer onhorizontal tubes on both experimental and theoretical aspects, this thesis studythe condensation heat transfer(CHT) on HTB systematically. The following listedthe main activities and contributions:Firstly, to solve problem of CHT on HTB high-precisely, this thesis proposestwo new test methods of CHT,1) Homology method which could obtaininundation effect of horizontal tube bundle high-precisely,2) Small-cyclecalibration method which could obtain CHTC on HTB high-precisely. Andfurther put forward system error control method for the test of CHTC andinundation effect. Based on requirements of the new test methods and errorcontrol strategy, the author proposed a schema of testing system for CHT on HTB.After a series of activities, including design, implementation, commissioning andtesting, the author built a systematically testing platform for CHT on horizontaltubes. Then the impact of all the factors brought to CHT on HTB, includingworking medium, operating condition, tubes, tube bundles, non-condens-ablegas, etc., and assessed the system performance comprehensively was studiedexperimentally. This provides the necessary data support for further theoreticalresearches. All of which is significant important to the acquisition andaccumulation of high-quality experimental data which is needed by the theoreticdevelopment of condensation heat transfer on horizontal tube bundles.Secondly, in order to solve (or describe) the problem of CHT on singlehorizontal tube from theoretical level, based on Nusselt’ laminar film CHT theory, this essay raises standard forms of models which describe CHT on single tubeissue of several kinds of horizontal two-dimensional finned tube, also this essayproposes a semi-empirical model for condensation heat transfer of horizontaltwo-dimensional fin tube. In order to describe enhanced CHT issues on a singlehorizontal tube, based on the construction and solving of extreme problem oflaminar CHT, this essay presents the definition of self-similar enhanced factormodel and builds this model afterward. Then based on the model, the authordiscussed the mechanism of enhanced CHT of finned tubes. The proposeddefinition and model of self-similar enhanced factor laid a foundation forresearchers to understand the essence of the phenomenon of enhanced heattransfer and get instruction to do the design and development of enhanced heattransfer surface.Thirdly, in order to solve or describe the issue of CHT on HTB from thetheoretical level, this essay brings a systematic modeling method and two models:smooth tube bundles model and two-dimensional finned tube bundlesmodel(effect of surface tension is ignored). Four breakthroughs are achieved:1)proposed the classification and definition of condensate liquid in the horizontaltube bundle, clarified the definition of the tube row effect and inundation effectbased on the classification of condensate.2) studied the different impact causedby three types of condensate (namely condensed condensate, falling condensateand action condensate) to the CHT on horizontal tubes, and by combining withthe theoretical analysis the author introduces the description methods of theimpact of each kind of condensate in CHT.3) proposed standardized processingapproach to the condensation flow pattern, and put forward method for thedescription of the heat transfer issues arose from different flow pattern.4)introduced "crowding out" concept to describe the effect of condensatefluctuations on tube surface caused by migration condensate on CHTC. Based onthe test result and theoretical analysis, the author defined the description modelof the effect that the "crowding out" having on CHTC. The established smoothtube bundles model for CHTC, which takes into account of the coverage ofcomprehensive factors and sticks to the consistency of model with testing result,is significantly superior to conventional bundle model. The systematicalmodeling method of CHT on horizontal tubes and the two-dimensional finnedtube bundle model, which based on the smooth tube bundle modeling, laid afoundation for further improving the model of two-dimensional fin tube bundleand three-dimensional fin tube bundle.At last, in order to breakthrough the enhanced heat transfer problem thatCHTC on HTB is facing technically, this essay proposes control method andtechnical measures of inundation effect, add in diversion ducts to eliminate the inundation effect. Experiments proved the effectiveness of the control method,explored the failure model and influence of the technique measures, researchedthe influence on the structure and thermal design of bundles and analyzed thebenefit of the technique measures on a case study. The test shows that the CHTCon HTB could be highly improved and the consumption of tubes could besignificantly reduced by applying this technique properly. Otherwise, improperlyuse of this method could deteriorate the CHTC on HTB.The work listed in this paper is solving problems of CHT on HTB from bothexperimental and theoretical aspects. Meanwhile, the approach introduced forenhancing condensation heat transfer of HTB from technique aspect has set up anew model for others to reference. All of these contributions have significantscientific value to the improvement of theory for CHT on HTB, and havesignificant society and economic values to improve the energy efficiency of HTBequipment in many fields.