收稿日期：2023-01-16基金项目：吉林省教育厅科技项目（JJKH20220100KJ ）、东北电力大学青年博士科研助推计划（BSZT02202102）资助作者简介：王彦红（1983），男，博士，副教授。
引用格式：王彦红，李浩然，李洪伟.U 型再生冷却通道内超临界航空煤油换热特性数值模拟[J].航空发动机，2023，49（4）：16-25.WANG Yanhong ，LI Ha⁃oran ，LI Hongwei.Heat transfer of supercritical aviation kerosene in a u-shaped regenerative cooling channel[J].Aeroengine ，2023，49（4）：16-25.U 型再生冷却通道内超临界航空煤油换热特性数值模拟王彦红，李浩然，李洪伟（东北电力大学能源与动力工程学院，吉林吉林132012）摘要：为了解决航空发动机的高温热防护问题，通过RNG k-ε湍流模型开展了U 型再生冷却通道内超临界压力RP-3航空煤油换热特性数值研究。
探究了进口参数、固壁热导率、壁面粗糙度对换热的影响机制。
基于流场和温度场揭示了换热特征和换热机理，通过离心力参数讨论了其作用机制，阐述了二次流对换热的影响，提出了换热关联式，其预测偏差处于±20%以内。
结果表明：上游水平通道和下游水平通道受非对称加热作用产生弱二次流，弯通道受离心力作用产生强二次流，高温区近壁流体吸热能力降低造成传热恶化，最高壁温约为935K ；离心力促使热流产生显著的周向迁移。
在高进口温度下传热恶化起始位置提前到弯通道，加剧了离心力作用，使热流迁移增强。
提高固壁热导率和壁面粗糙度，换热均增强，对离心力影响可忽略。
关键词：U 型通道；再生冷却；超临界航空煤油；换热特性；热流迁移；高温热防护；航空发动机中图分类号：V231.1文献标识码：Adoi ：10.13477/ki.aeroengine.2023.04.003Numerical Simulation on Heat Transfer Characteristics of Supercritical Aviation Kerosene in a U-shapedRegenerative Cooling ChannelWANG Yan-hong ，LI Hao-ran ，LI Hong-wei（School of Energy and Power Engineering ，Northeast Electric Power University ，Jilin Jilin 132012，China ）Abstract ：In order to solve the problem of high-temperature thermal protection of aeroengine ，numerical research on heat transfer characteristics of supercritical-pressure RP-3aviation kerosene in a U-shaped regenerative cooling channel was conducted based on the RNG k-εturbulence model.Effect mechanisms of the inlet parameters ，solid wall thermal conductivity ，and wall roughness on heat trans⁃fer were investigated.Based on the flow field and temperature field distributions ，the characteristics and mechanisms of heat transfer were revealed.The centrifugal force effect was discussed through the centrifugal force parameters.The influence of secondary flow on heat trans⁃fer was described ，and the heat transfer correlation was proposed ，with prediction deviations within ±20%.The results show that the up⁃stream horizontal section and the down-stream horizontal section generate weak secondary flow due to the asymmetric heating ，the bendsection generates strong secondary flow due to the centrifugal force ，and the heat transfer deterioration is caused by the reduced heat ab⁃sorption capacity of near-wall fluid in the high-temperature region ，and the maximum wall temperature is approximately 935K.The cen⁃trifugal force leads to a significant circumferential migration of heat flux.The starting position of heat transfer deterioration is advanced to the bend section at the high inlet temperature condition ，the centrifugal-force effect is aggravated and the heat flux migration is enhanced.With the increase of solid thermal conductivity and wall roughness ，the heat transfer is enhanced and the effect on centrifugal force can be ignored.Key words ：U-shaped channel ；regenerative cooling ；supercritical aviation kerosene ；heat transfer characteristics ；heat flux migra⁃tion ；high-temperature thermal protection ；aeroengine第49卷第4期2023年8月Vol.49No.4Aug.2023航空发动机Aeroengine0引言再生冷却是解决超声速发动机热端部件冷却问题的重要技术，其通过碳氢燃料流经燃烧室固壁内的微通道吸收机体极端热量[1]。
Heat exchangers1.Classification:(a). According to flow arrangement(1). Parallel flow (co-current flow)(2). Counter flow (counter-current flow)(3). Cross flow(b). According to type of construction(1). Finned (mainly for gas/liquid systems), un-finned(2). Shell and tube (probably most commonly used), very flexible,relatively cheap, used athigh pressure(3). Plate heat exchangers (when cleaning is important, foodindustry, milk processing),only at low pressure(4). Spiral heat exchangers(5). Compact heat exchangersTypes of heat exchangers(1). Concentric tube heat exchanger(a)Parallel flow, (b) counter-flow. This kind of heat exchanger has low heat transfer rateand thus very limited applications.(2). Shell and tube heat exchangers-very common in liquid-liquid systems, also as condensers.One shell pass and one tube pass (cross-counterflow)One shell pass and two tube passesTwo shell passes and four tube passesCross flow heat exchangers:(a) (b)(a)Finned with both fluids unmixed, (b) un-finned with one fluid mixed and the other unmixed Compact heat exchanger(a) Fin-tube (flat tubes, continuous plate fins), (b) Fin-tube (circulartubes, continuous plate fins), (c) Fin-tube (circular tubes, circular fins),(d) plate-fin (single pass), (e) plate-fin (single pas).Large specific surface area > 700 m2 /m3 but laminar flow because ofsmall size of channels (low heat transfer coefficients).Overall heat transfer coefficient:Where:R f′′-fouling factor (additional thermal resistance)R w-thermal resistance in the wall separating hot and cold fluid (corresponding to conduction) depends on material and geometryηo-overall surface efficiency defined q=ηoℎA(T b−T∞)Typical values of fouling factor:Typical values of overall heat transfer coefficientsEnergy balance (for all types of heat exchangers)Heat load –net change of internal energy in hot and cold fluid:Subscript h – hot fluid, subscript c – cold fluidIf no phase change and specific heat is constant:Energy transfer from hot to cold fluid:In general T h and T c vary along heat transfer surface.In engineering applications the driving force for the heat transfer is expressed in terms of inlet and outlet temperatures and:F- correction factor for non-parallel flowsEnergy balance:This form of energy balance is always used in engineering calculations and designing of heat exchagersCalculations based on log mean temperature differenceParallel flowCounter flowSpecial operating conditionsTemperature distribution depends on thermal capacity of hot Cℎ=mℎ∙c p,ℎ and cold Cℎ=mℎ∙c p,c fluid.During boiling/ condensation of a single component fluid/ vapour the temperature is constant assuming.For equal thermal capacities of both fluid local temperature difference is constant.Multi-pass and cross flow heat exchangersThe flow conditions can be more complex but the equations developedfor parallel flow heat exchangers can still be used but log meantemperature difference has to be modified:Calculate the driving force for counter current flow and multiply bycorrection factor F (depends on inlet and outlet temperatures and flowpattern) taken from the literature/graphs.Correction factor for two shells and four passes heat exchanger.Correction factor for cross flow heat exchanger with both fluids unmixed.Calculations based on effectiveness – NTU (number of transfer units) methodIf all inlet and outlet temperatures are given the Log MeanTemperature Difference method is recommended, but if only inlettemperatures are given (typical design problem) use of LMTD requiresiterative procedure.In such cases effectiveness-NTU method is better.Effectiveness of heat exchanger is defined as the ratio of actual heattransfer rate to the maximum possible heat transfer rate:Heat transfer rate can be easily calculated if ε, T h,i and T c,i are known as the actual heat transfer rate can be calculated from:Specific relations between NTU and ε depend on the type of heatexchanger and are given in the literature:For concentric tube, counterflow heat exchanger:For other types of heat exchangers algebraic relation are more complex and graphs are commonly used.Effectiveness of single pass, cross-flow heat exchanger with both fluidsun-mixed.SummaryA. The nature of the whole process for which heat exchanger is designedfrequently determines its type:a) hygiene/cleanliness is important (food industry) –plate heat exchanger,b) When process is carried out at high pressure – shell and tube,c) When space is limited – compact heat exchanger,d) Cost is also a major factor, shell and tube exchangers are cheap, plateor compact exchangers are expensive.B. If the inlet and outlet temperatures and mass flow rate of fluid (A) andthe inlet temperature of fluid (B) are known LMTD is recommended.1. Calculate heat load from energy balance for fluid (A)2. Assume flow rate and inlet temperature of fluid (B) and calculateoutlet temperature of fluid (B), or assume outlet temperature of fluid (B)(often temperature constrains) and calculate flow rate from energybalance for fluids (A) and (B).3. Draw the temperature distributions and calculate driving force4. Calculate heat transfer coefficients5. Calculate overall heat transfer coefficient (see methodology above)6. Calculate the heat transfer areaC. Alternatively (if not all temperatures are given) effectiveness-NTUmethod can be used.。
Unit 3 Typical Activities of Chemical Engineers化学工程师的例行工作The classical role of the chemical engineer is to take the discoveries made by the chemist in the laboratory and develop them into money--making, commercial-scale chemical processes. The chemist works in test tubes and Parr bombs with very small quantities of reactants and products (e.g., 100 ml), usually running “batch”, constant-temperature experiments. Reactants are placed in a small container in a constant temperature bath. A catalyst is added and the reactions proceed with time. Samples are taken at appropriate intervals to follow the consumption of the reactants and the production of products as time progresses.化学工程师经典的角色是把化学家在实验室里的发现拿来并发展成为能赚钱的、商业规模的化学过程。
化学家用少量的反应物在试管和派式氧弹中反应相应得到少量的生成物，所进行的通常是间歇性的恒温下的实验，反应物放在很小的置于恒温水槽的容器中，加点催化剂，反应继续进行，随时间推移，反应物被消耗，并有生成物产生，产物在合适的间歇时间获得。
