Annular Heat Exchanger Research Articles

Metal foam recuperators on micro gas turbines: Multi-objective optimisation of efficiency, power and weight

Small size and high efficiency of micro gas turbines require a higher surface-to-volume ratio of recuperators. Conventional recuperators can achieve a range of 250–3600 m2/m3. Advances in materials and manufacturing, such as metal foams, can increase significantly the exchange surface and improve compactness ranging approximately from 500 to over 10,000 m2/m3, due to their exceptional micro geometry. The main advantage is that the increase of surface area does not impact the cost of the heat exchanger as much as conventional recuperators due to their easy manufacturing. This work addresses the optimisation of the recuperator using multiple objectives satisfying efficiency, power output and weight criteria, offering a holistic approach that takes into account the entire system rather than individual components or channels. A model is developed to represent the performance of a compact heat exchanger in micro gas turbines. The recuperator is an annular heat exchanger with involute profile filled with porous media in a counterflow arrangement on the hot and cold sides. The model allows the evaluation of the effect of the recuperator geometry features on the electrical efficiency, power output and weight savings in a micro gas turbine. Existing models for the global heat transfer coefficient, effective thermal conductivity, surface area and pressure drop of porous media are selected and implemented. The design variables of multi-objective are the pore density, porosity and number of channels, whilst the objectives are the overall electrical efficiency, power output and recuperator weight. The problem is solved using the Non-Dominated Sorting Genetic Algorithm (NSGA-II) to determine an approximation of the Pareto front, whilst the accuracy of the approximation is assessed against the solution obtained by an exhaustive search. The comparison shows that NSGA-II outperforms an exhaustive search by at least 90 % in terms of computational efficiency. These results allow the quantification of the impact of metal foam technology on performance metrics of the recuperator as well as the entire system. This quantitative analysis provides valuable insights into the behaviour of metal foam recuperators in micro gas turbines. An optimal design with 30 % efficiency and 28 kW power output appears in pore densities of approximately 10 and 20 pores per inch (PPI) for the air and gas side respectively, and a porosity of 85 %, which leads to a state-of-the-art recuperator weight of 48 kg. The efficiency improvement over the industry standard is 15 %, with only a 2.5 % reduction in power output.

Enhanced Heat Transfer Mechanisms in a Horizontal Annular Heat Exchanger Utilizing a Central Tubular Heater

Enhanced Heat Transfer Mechanisms in a Horizontal Annular Heat Exchanger Utilizing a Central Tubular Heater

Numerical investigation of thermo-hydraulic performance in an annular heat exchanger with sinusoidal vortex generators

This study investigates thermal performance enhancement by utilizing vortex generators (VGs). VGs come in many designs, and this paper proposes optimizations for the sinusoidal vortex generator (SVG) when used in an annular conduit to improve heat transfer with minimal pressure drop. Two vital parameters of the SVG are analyzed, namely, blockage ratios (BRs) (0.1 and 0.2) and attack angles (α) (0–90°). The investigated fluid regime is turbulent, with the Reynolds number (Re) ranging from 5973 to 11,947. Three rows of SVGs are fitted on the surface of the inner pipe, where constant heat flux is applied, while the outer pipe wall is entirely insulated. The results indicate that the highest Nusselt number is enhanced by 20.4% over the smooth pipe when the case with BR = 0.2 and α = 90° is used at Re = 5973. However, the friction factor increases by 56.5% for the same case. Two types of transverse vortices are identified, where one type has its rotational axis normal to the inner pipe surface, and the other has its rotational axis parallel to the inner pipe surface. Those vortices with the axis perpendicular to the pipe surface merge with the fluid above the SVG to develop longitudinal vortices in different BRs and α. The case with BR = 0.2 and α = 15° yields the greatest average performance evaluation criterion (PEC) compared to other tested cases with a value of 1.054. This study finds that SVGs can contribute to a more efficient annular pipe-based heat transfer system.

Proposing and thermo-economic optimization of an annular-thermoelectric gas heat recovery unit with a novel hybrid fin-pin vane and porous insert

Heat recovery from the cylindrical surface of the exhaust gas pipes is one of the promising applications of annular thermometric generators (ATEG). A pipe-shape based heat exchanger can be attached to the inner surface of the annular-thermoelectric generator to recover the hot exhaust gas in the form of electricity generation. In this paper, a novel grid annular fin-based heat exchanger with porous inserts is proposed which can boost the output power of the ATEG up to 1.45 and 2.12 times compared to the conventional common pipe-based heat exchangers. A comprehensive parametric analysis is carried out to investigate the impact of various geometric and operational parameters such as porous insert height, porous insert angle, porous inserts length, Re number, number of thermocouples, and so on thermal, exergetic, and economic factors. An optimized value of height, length, and angle of the porous insert can maximize the output power of the proposed system. Economic analysis is also provided to identify the corresponding costs of the grid annular fin-based heat exchanger with porous inserts for the heat recovery aim.

Analysis of complete boiling process inside double pipe porous heat exchanger filled with NanoFluids

This study involves an investigation on fully evaporation process inside annular porous heat exchanger using Cu/distilled water nano-fluid. Emphasis has been placed on how the use of Cu/distilled water affected two-stage flux predictions. Two-phase mixture model, based on the considerations of Local Thermal Equilibrium (LTE), has been reformulated to involve the influences of employing nano-fluid instead of only water. To display the actions of employing nano-fluid, the predictions of liquid saturation and temperature, obtained using Cu/distilled water and only water, have been presented and compared for a wide ranges of geometric conditions, operating conditions and properties of porous media. The outcomes displayed that the using Cu particle to water has a large impacts on the heat diffusivity, where the boiling and condensation fronts are considerably moved to downstream and upstream sections, respectively, as compared to the predictions of only water due to rising the axial diffusion. The temperature at the pipe exit is considerably decreased when adding Cu particles to water as compared to the pure water case. The predications of Cu/distilled water show that the nano-fluid volume fraction, geometric parameters, operating parameters and porous structure properties have high actions on the locations of initiation and termination of phase change process. Since the fluid temperature for pure water case is extremely high at the superheated vapour region, the addition of Cu particles to water considerably reduces the fluid temperature in this region and hence, the use of nano-fluid can be considered as a safety factor in the applications that used heat exchangers (boiling processes) due to it improves the mechanism of heat transfer during the boiling process.

The Phenomenon of Flow and Heat Transfer in Annular Heat Exchanger on Plain Tube Condition

Advanced industrial development in technology necessitates using equipment that can effectively and efficiently transfer heat energy. A heat exchanger is the most common device used in industry to transfer heat energy. The Annular Heat Exchanger is one of the heat exchangers used in industry that is simple to manufacture and inexpensive to finance. The annular heat exchanger is commonly found in the food, beverage, chemical process, pharmaceutical, and refrigeration technology industries. This type of heat exchanger is used due to its simple design, easy to manufacture, and low cost. The presence of a heater in a concentric pipe with a straight construction is the general form. Experimentation was carried out in this study. A heater is used to transfer the heat, and there is a cold fluid flow through the annulus. The heater is linked to an AC Voltage Regulator and has five heat settings ranging from 400 W to 600 W. Simultaneously, cold fluid flows in the annulus via a closed system with six flow variations ranging from 2.5 GPM to 5 GPM. A cooling system is used to keep cold fluids at a constant temperature. The purpose of this research is to demonstrate the flow and heat transfer phenomena in an annular heat exchanger. This study obtained the average heat transfer convection coefficient, h, and Nusselt number, Nu. The steady-state conditions for the heat variations of 400 W, 500 W, and 600 W are 2400 s, 3600 s, and 5400 s, respectively. The flow calibration results in this apparatus experiment have an error of 0.05%. At a heat variation of 500 W and Reynolds number 10669, the highest average heat transfer convection coefficient (h) reaches 6703 W/m2K, and the average Nusselt number (Nu) of 314 is obtained. The Reynolds number of critical transition points for heat variations of 400 W, 450 W, 500 W, 550 W, and 600 W are 6986, 7125, 8444, 8616, and 10009, respectively.

Thermo-hydraulic performance investigation of heat pipe used annular heat exchanger with densely longitudinal fins

To enhance the heat transfer capacity of the condenser end in the heat pipe heat exchanger, heat transfer and flow characteristics investigations of three densely longitudinal fin-equipped annular heat exchangers have been carried out by using a combined method of experimental testing and numerical simulation. One of the heat exchangers as a baseline is featured by the long straight fins. The other featured folded fins and arc-shaped fins, in which 40 rows of short fins were arranged just like the blade-lattice. The attained results showed that the short fold fins and arc-shaped fins had Nusselt numbers that were 27% and 35% higher than the long straight fins, and had friction factors that were 1088% and 2209% higher than the long straight fins. It indicates that the dense fin arrangement has a relatively limited influence on the wall temperature and overall heat transfer capacity. However, the friction loss is significantly sensitive to the fin arrangement because of the severe flow drag and flow separation induced by the blade-lattice like fins. The thermo-hydraulic performance evaluation suggests that the three densely longitudinal fins are suitable for different application scenarios with different heat transfer and pressure loss requirements. This work serves as a reference for the heat exchanger design in the heat pipe-based thermal power conversion system.

Heat transfer and eccentric effect investigation on heat pipe used annular heat exchangers with densely longitudinal fins

Within the annular heat pipe heat exchangers, heat transfer capacity and assembly eccentricity are two crucial issues for the overall thermal performance (such as heat transfer capacity, flow friction, and temperature distribution). This study aimed to investigate: 1) the heat transfer and fluid flow characteristics of two annular heat exchangers for the purpose of configuration optimization; and 2) the influence of an assembly clearance and the resulting eccentricity on heat transfer characteristic and temperature distribution. Two types of densely longitudinal fins with different heights were designed to enhance heat transfer. Three eccentricities were compared under uniform heat flux and uniform temperature conditions, and two mediums of air and helium were considered to fill the assembly clearance. The results indicated that due to the larger heat transfer area, the average heat transfer coefficient and friction factor produced by the high fins equipped annular heat exchanger were about 20% and 28% higher than the ones with short fins within Re = 2000–15000. The thermal resistance of the clearance varied with the assembly eccentricity. The larger the eccentricity, the smaller the average thermal resistance. Significant temperature gradients appeared in assembly clearance under uniform heat flux conditions. Under uniform temperature conditions, the temperature gradients are outstanding in the annular heat exchanger. A filling medium with greater thermal conductivity is suggested since it can effectively improve the circumferential temperature nonuniformity. This study provides a design guideline as well as heat transfer performance optimization for the heat pipe heat exchangers.

Analytical study on core flow in a novel scheme of cascade heat exchanger intensified with open foam partially filled in an annulus

Due to the importance of energy-saving and efficiency in the industry, a novel scheme for waste heat recovery was utilized in the cascade refrigeration cycle. This system is composed of a cascade heat exchanger combined with a recuperator intensified with open foam. The exhaust air from the heat exchanger is used for the air handling unit. Also, core flow in an annular channel is proposed as an innovation to enhance heat transfer. An analytical study was performed to evaluate the impact of metal foam properties on the performance of the partially filled annular heat exchanger with asymmetric isothermal boundary conditions. The energy equations were decoupled by normalizing, linear combination, and the variable change method. Then by forming the Bessel differential equations, temperature solutions were achieved in terms of the modified Bessel functions of the first and second kinds. In the energy and momentum equations of the porous region, the local thermal non-equilibrium (LTNE) and the Darcy-Brinkman models were used, respectively. The analytical solutions of velocity, pressure drop, mass flow ratio, temperature, and Nusselt numbers were obtained. A hydraulically critical point exists at the nondimensional interfacial radius of 2.86 for Da=10−4. It revealed that the Darcy number and the thermal conductivity ratio are two crucial parameters for improving performance. Based on the Performance evaluation criterion (PEC) definition, the optimal porosity value of 0.91 was determined. Also, a design triangle in the range of metal foams was proposed to select the local Nusselt and Biot numbers. At a particular Biot number, the PEC value increases 3.76 times in the design range of metal foams. Results demonstrated that the core flow in an annular heat exchanger leads to high performance, several times greater than non-core flow.

Thermoelectric Performance Evaluation and Optimization in a Concentric Annular Thermoelectric Generator under Different Cooling Methods

To ensure effective heat recovery of thermoelectric generators, a cooling system is necessary to maintain the working temperature difference of the thermoelectric couples, which decreases continuously due to thermal diffusion. In order to evaluate and improve the thermoelectric performance of a concentric annular thermoelectric generator under various cooling methods, a comprehensive numerical model of the thermo-fluid-electric multi-physics field for an annular thermoelectric generator with a concentric annular heat exchanger was developed using the finite-element method. The effects of four cooling methods and different exhaust parameters on the thermoelectric performance were investigated. The results show that, in comparison to the cocurrent cooling pattern, the countercurrent cooling pattern effectively reduces temperature distribution non-uniformity and hence increases the maximum output power; however, it requires more thermoelectric semiconductor materials. Furthermore, when using the cocurrent air-cooling method, high exhaust temperatures may result in lower output power; high exhaust mass flow rates result in high exhaust resistance and reduce system net power. The maximum net power output Pnet = 432.42 W was obtained using the countercurrent water-cooling, corresponding to an optimal thermoelectric semiconductor volume of 9.06 × 10−4 m3; when compared to cocurrent water-cooling, the maximum net power increased by 8.9%, but the optimal thermoelectric semiconductor volume increased by 21.4%.

Design and testing of energy-efficient heat exchangers for Newtonian and non-Newtonian fluids – A review

Heat transfer enhancement, pumping power and weight minimization in enhanced heat exchangers has long been achieved by deploying tubes with internal surface modifications like microgrooves, ribs, fins, knurls, and dimples with and without tube inserts. This article presents a very extensive review of experimental and computational studies on heat transfer enhancement, which covers convectional and unconventional working fluids under different fluid flow conditions. Compound augmentation with tube surface modifications and inserts has yielded enhancements in the overall heat transfer coefficient of over 116% in the fully developed turbulent flow regime. Exotic fluids like nano-coolants deployed in spiral grooved mircofin tubes yielded 196% enhancement in tube side heat transfer rate for concentrations as low as 0.5% by volume, while the thermal efficiency index measuring the overall enhancement in relation to the pumping power was 75%. However, reviews that address the combined effect of unconventional fluids, surface modifications and tube inserts on the overall thermo-hydraulic performance of annular heat exchangers seem to be limited. Further, nano-coolants aren’t frequently used in the process industry. The goal of this study is to document and evaluate the impact of cost-effective and energy-saving passive enhancement techniques such as tube surface modifications, tube inserts, and annular enhancement techniques on annular heat exchangers used in the process industries with Newtonian and non-Newtonian fluids. This review should be useful to engineers, academics and medical professionals working with non-Newtonian fluids and enhanced heat exchangers.

Annular thermoelectric generator performance optimization analysis based on concentric annular heat exchanger

In order to increase the energy conversion efficiency of thermoelectric generators for automobile systems where the heat sources are commonly cylindrical, a novel concentric annular thermoelectric generator (CATEG) consisting of annular thermocouples and a concentric annular heat exchanger is proposed. A numerical model of the CATEG is first established using a finite-element method, based on which the thermoelectric performances of the proposed CATEG and the conventional annular thermoelectric generator (ATEG) with a cylindrical heat exchanger are compared. The relationship between the size of the heat exchanger, heat transfer characteristics, and heat flow resistances are comprehensively studied. Furthermore, to balance the relationship between heat transmission and fluid flow resistances, and to extract the maximum net power, the optimal design of the concentric annular exchanger is obtained and analyzed. Simulation results show that the optimized ratio of the inner and outer diameters of the heat exchanger is 0.94, and the new ATEG with the proposed concentric annular heat exchanger can significantly increase the total heat transfer coefficient as well as the pressure drop, leading to a maximum net power of 65% higher than the conventional ATEG.

Study of Thermal Behavior of a Horizontal Two Fins Annular Tube Heat Exchanger with Melting Phase Change Material: Fins Orientation Effects

This paper investigates the effect of fins orientations of a horizontal two fins annular tube heat exchanger on enhancing the heat transfer during the melting process of n-eicosane, as phase change material (PCM) used in thermal storage systems. Based on the enthalpy-porosity method, two-dimensional model is performed and solved by Ansys Fluent. The impact of the fins orientation on melting rate, thermal conduction and natural convection, as the angle of the system varied from 0º (vertical fins) to 90º (horizontal fins) are discussed. Numerical predictions are validated by comparison with experimental data and numerical results reported in the literature. Good agreements are achieved. The results show that at initial time of the melting process, the conduction heat transfer is dominant. During the melting process, the heat transfer in the horizontal fins is more effective while the upper half of PCM melts and less effective as the lower half of PCM melts because fin arrangement resists natural convection occurs. However, the effectiveness of heat transfer and convection in the vertical fins is almost constant during the entire melting process. From comparison, better heat transfer performance is achieved with vertical fins system; complete melting was reduced 250% compared to horizontal fins case.

QOVUN BO`LAKLARINI QURITISH UCHUN MEXANIZASIYALASHGAN KAMERALI-ZANJIRLI QURITISH QURILMASINING ZANJIRLI UZATMASINI HISOBLASH

The article deals with the calculation of the drive and chain transmission of the newly created mechanized drying plant for drying melon slices. The essence of the utility model: the machine contains a horizontal tunnel chamber, inside which is mounted a chain conveyor with driving and driven sprockets, load-carrying elements, the IR emitters with reflectors on top of the camera mounted electric air heater, fan, an annular heat exchanger equipped with inlet and outlet nozzles of the drying agent. On the branches of the conveyor chain, lodgments with folding clamps are mounted, on which load-bearing elements are fixed, which are used as wooden poles. The calculation of the drive and chain transmission of the drying plant conveyor was carried out according to the existing method according to the scheme shown in the figure. Thus, the main parameters of the drive and chain transmission parts of the mechanized chamber-chain drying plant for drying melon fruits were determined by calculation

Thermo-Hydraulic Performance Investigation of Heat Pipe Used Annular Heat Exchangers with Densely Longitudinal Fins

Thermo-Hydraulic Performance Investigation of Heat Pipe Used Annular Heat Exchangers with Densely Longitudinal Fins

Boiling heat transfer characteristics of graphene oxide nanoplatelets nano-suspensions of water-perfluorohexane (C6F14) and water-n-pentane

In the present work, the boiling heat transfer coefficient (BHTC) and fluid flow characteristics of graphene oxide nanoplatelets (GONPs) nano-suspensions in an annular heat exchanger (AHEX) were experimentally investigated. The BHTC, pressure drop (PD) and the friction factor (FF) of the heat exchanger was quantified, and effects of various operating conditions including heat flux (HF), flow rate (FR), the temperature of the nano-suspension and the mass concentration (MC) of the GONPs on the HTC and the PD of the system was assessed. Results showed that by increasing the HF, the weight concentration of the GONPs, and the temperature of the working fluid, the BHTC of the system increases. Also, the presence of GONPs can augment the friction forces, viscosity, and, as a result, increase the PD and the FF of the system. For all the experiments, the BHTC of the system was more significant than water. A comparison between water-perfluorohexane and water- n-pentane nano-emulsions revealed that water-n pentane has better thermal performance and lower PD in comparison with perfluorohexane despite the presence of the GONPs within the bulk of the nano-emulsion.

A Numerical Approach to Study the Steady State Heat Transfer Characteristics of an Annular Porous Heat Exchanger

Heat exchangers are one of the most heavily studied devices and extensive work has been performed over the years to increase their effectiveness. The present work investigates the heat transfer characteristics of an APHE (annular porous heat exchanger) in terms of different parameters. A modified design for the APHE is proposed, which resembles a conventional double pipe heat exchanger, with the annular portion of the outer pipe filled with a specific type of porous medium in order to intensify the heat transfer process. Commercial CFD package ANSYS Fluent has been utilized to investigate the performance of the proposed design numerically. Introduction of porous medium induces an increase in pressure loss which is undesirable; hence, a trade-off is present between hydrodynamic and thermodynamic performance. In the present work different inlet parameters have been modified such as different values of porosity (70% to 90%), different inlet velocities of hot fluid (1 m/s to 9 m/s), different inlet velocities of cold fluid (5 mm/s to 25 mm/s), and different inlet temperature of hot fluid (400 K to 480K), and their effects on the outlet parameters have been studied. The change in heat transfer has been presented quantitatively along with other significant parameters such as mass flow rate, pressure drop and hot gas outlet temperature. These results have been compared with the values for conventional heat exchangers in order to establish the effectiveness of APHE.

The Effect of Temperature and Twist Ratio from Twisted Tape Insert to Pumping Power in Concentric Exchange Tools using Nanofluida TiO2 and Oli Termo XT-32

The heat exchanger is a device used to heat between two or more fluids. Heat exchangers can use fluid flow or construction. Heat exchangers are widely used in engineering applications. The heat exchanger has long been recognized by industries that relate to heat transmission phenomena. Improve the speed of all types of heat exchangers widely in the industry, in the process of retrieval (heat recovery process), air conditioning, and chemical reactors. Increasing the amount of light flow can be done in several ways, namely: flowing inequality, damaging the boundary layer, changing the fluid flow, and rotating fluid flow (vortex flow). One of the techniques used to increase the heat coefficient of convection is to provide insert material or often called Insert. The research methodology was to determine the effect of the rotational ratio of the insertion bent band on the pumping power of the pipe heat exchanger by using TiO2 nanofluid with a heat transfer oil base fluid (thermo XT32). This research was carried out with experimental methods, as for the tools and research materials in this case: primary fluid of thermo XT32, TiO2 nanoparticles, and an annular channel concentric pipe heat exchanger by inserting a bent band. In and out data (Th, i and Th, o), the temperature of the fluid in and out of the annulus (Tc, i and Tc, o), the outer wall temperature of the inner tube (Tw1, Tw2, Tw3, Tw4), and the water height difference on the manometer. Data collection was carried out with TiO2 particle nano samples with a volume fraction of 0.3% Vol, without a bent band. Insert (plain tube) and rotate the tape with a touch ratio of 3, 6, and 9. The results of the research carried out on the conclusion of the rotational ratio in the band bending the insertion of the pumping power of the heat exchanger. This proved the pumping power increases with decreasing rotational ratio from a bent band, the addition of a twisted tape insert can increase the pumping power when compared to a pipe heat exchanger without concentrically turning the inserted tape (plain tube), this is proven by using a twisted tape insert with a twist ratio of 3. It requires a pumping power of 87.71 W / m2 to be able to drain TiO2 nanofluid, with a volume fraction of 0.3% Vol at a fluid temperature of 60 °C whereas when compared to a heat exchanger without turning the inserted tape (plain tube), it only requires pumping power of 17.73 W / m2. to be able to drain nanofluid in a heat exchanger.

Improved thermal performance of annular fin-shell tube storage system using magnetic fluid

The main contribution of this paper is achieving a significant thermal performance improvement of annular fins-shell-tube heat exchanger energy storage system using magnetic fluid. The fin efficiency is increased by 20% with annular fin-magnetic fluid geometry as compared to without magnetic fluid. This improvement in thermal characteristics of annular fin system can be attributed to the formation of nano-channels in the field directions and effective increase in overall heat transfer coefficient due to the replacement of solid-gas interface with the liquid-gas interface. This replacement leads to improved convective heat transfer rate and overall thermal characteristics, which is the new knowledge contribution for various energy storage systems. In the present work, a simple and novel method for improving the thermal performance of natural convection energy storage system is reported. This novel method can improve the overall performance of the systems with natural convection extended surfaces and makes it suitable for numerous heat transfer applications. A magnetic fluid thin layer association with annular fin geometry has been proposed to improve the shell-tube heat exchangers performance, and an in-house experimental setup is used to study its dimensional and non-dimensional heat transfer characteristics. Kerosene and water-based MF were prepared by chemical co-precipitation method and employed on the top surface of the fin to maximise the heat transfer rate and to increase the effectiveness (ε) of the fin system. This thin layer of MF was maintained on the top surface of the fins using the magnetic ring of small NdFeB magnet of 1 mm thickness and 2.5 mm diameter. It is observed that a significant increase in relative heat transfer rate (∼35%) taking place using a thin MF layer over the top surface of the fin which leads to enhancement in fin performance. Also, the temperature distribution along the length of the fin shows a sharp decrease in temperature near the top surface which corroborates our observations that the magnetic ring over the surface works as a chill block which provides a directional cooling through magnetic nano-channels. These new findings can be valuable in the design of an efficient annular fin-shell tube latent heat exchanger storage system.

Heat transfer characteristic analysis of a novel annular nuclear heat exchanger for propulsion system

In conventional nuclear propulsion systems, reactor with gas-cooled core is bulky and requires extra space to be placed. A new type of nuclear heat exchanger with multi-annular structure is directly put into the combustion chamber to heat compressed air. Nuclear fuel is evenly embedded into the annular wall, which guarantees a steady energy supply to meet the propulsion needs. Because of the strong heat transfer capacity, the reactor is smaller, more compact and flexible.In this paper, a numerical model of propulsion and heat transfer is established for the nuclear jet engine to verify the feasibility of the novel nuclear heat exchanger. To find the optimal structure for cruise and after-burning flight, flow and heat transfer characteristics of the new reactor system are studied by adjusting the annulus numbers in the finite space. The sensitivity of the external control variables to the improvement of propulsion performance is investigated under the new structure. Finally, reactor performance is analyzed by physical-thermal coupling calculation in core.The analysis results show that the multi-annular nuclear heat exchanger has the optimal structure at the intersection point of characteristic parameter normalization. The multi-annular structure with n = 64 has more uniform power distribution, which is selected as the optimal structure for the new system. It can meet the heat transfer and thrust requirements from cruise to after-burning flight. The new system reduces the additional reactor configuration and saves the afterburner space, which is of great importance to the miniaturization and performance improvement of the nuclear propulsion system.