Research On Performance Check Method Of Shell And Tube Fuel Oil Heat Exchanger

In aero-engine,shell-and-tube fuel oil heat exchanger in lubricating oil heat dissipation system is used to reduce the temperature of lubricating oil and transfer heat to fuel.Its thermal performance determines the temperature level of lubricating oil system and affects the efficiency and safety of aero-engine.Therefore,this paper studies the calculation method of performance checking of shell-and-tube fuel oil heat exchanger,and develops a performance checking software.Firstly,according to the structural characteristics of complex shell-and-tube fuel oil heat exchangers,the P-NTU checking calculation method with wide application scope is studied,and the structural characteristics and P-NTU relationship of E-and F-type shell-and-tube fuel oil heat exchangers with multi-tube and multi-shell structures are analyzed.According to the circular,arc and rectangular shell structures of shell-and-tube fuel oil heat exchangers and the structural characteristics of single baffles,a method for calculating the structural parameters for checking problems is proposed in this paper.The calculation methods of convective heat transfer coefficient and pressure drop between shell and tube of shell-and-tube fuel oil heat exchanger are compared and analyzed.When the shell side is single-phase flow,Bell-Delaware method is used to calculate the convective heat transfer coefficient and pressure drop in the shell side,and the accuracy of the algorithm is verified by experimental results.When the shell side is oil-air two-phase flow,the calculation method of convective heat transfer coefficient of two-phase flow is compared and analyzed,and it is found that the split-phase flow model is more applicable to the performance check calculation of the shell-and-tube fuel oil heat exchanger in this paper.The empirical formulas of different convective heat transfer coefficients are selected according to Reynolds number.In addition,for the shell-and-tube fuel oil heat exchanger studied,the traditional pressure drop empirical formula for the flow of fluid through the inlet and outlet of the tube box is revised,and the revised calculation method is given.On the basis of the above calculation methods,a mathematical model for performance checking of shell-and-tube fuel oil heat exchangers is established and developed by using C++ programming.The software mainly includes three single-phase checking calculation modules of circular shell-and-tube fuel oil heat exchangers,arc shell-and-tube fuel oil heat exchangers and rectangular shell-and-tube fuel oil heat exchangers,and three two-phase checking calculation modules,the high efficiency calculation of the performance check of the shell-and-tube fuel oil heat exchanger with complex structure is realized.Finally,the accuracy of the performance checking software of shell-and-tube fuel oil heat exchanger is preliminarily analyzed by using the experimental data in the literature.In addition,the performance test of arc-shaped shell-and-tube fuel oil heat exchanger was carried out on the experimental platform of aeroengine lubricating oil system built by our research group.By comparing and analyzing the experimental results with the results of software verification,the efficiency and accuracy of the verification software were further verified.Using the results of software verification,the convection heat transfer system of shell-and-side single-phase flow and two-phase flow of shell-and-shell-type fuel oil heat exchanger was verified.The numerical characteristics of the shell side convection heat transfer coefficient are studied,and the effects of the gas phase conversion velocity and the liquid phase conversion velocity on the shell side convection heat transfer coefficient are analyzed.