Preliminary Design of a Fuel Element With Divergent Hot Gas Channel In Particle Bed Reactor for Nuclear Thermal Propulsion

Abstract The nuclear thermal propulsion (NTP) system can shorten the travel time in deep space exploration and reduce the initial mass of the launch vehicle due to its superior characteristics including high specific impulse and large thrust. Particle bed reactor (PBR) is one of the most appropriate reactor concepts to equip the NTP systems. To make the best use of PBR, the thermal-hydraulic design of the fuel element should be carefully considered and a flow-power matching technology should be developed. In this paper, a novel design employing a divergent hot gas channel is proposed to achieve a uniform flow distribution with lower maximum temperature and pressure drop. Through the analysis of the 1D modified momentum equation in the inlet plenum and hot gas channel, the model of pressure drop is established. Then, the differential equation of the ideal cross-section of the hot gas channel is derived. At last, the flow and heat transfer process in the fuel element with divergent hot gas channel is simulated by using computational fluid dynamics (CFD) code, and the reduction of pressure drop and temperature verifies the theoretical model. This study shows that the proposed design of the divergent hot gas channel can provide a new idea for thermal-hydraulic optimization of the PBR fuel element.

Download Full-text

Analysis of the Flow Distribution in a Particle Bed Reactor for Nuclear Thermal Propulsion

Energies ◽

10.3390/en12193590 ◽

2019 ◽

Vol 12 (19) ◽

pp. 3590 ◽

Cited By ~ 2

Author(s):

Ji ◽

Liu ◽

Sun ◽

Shi

Keyword(s):

Hot Spot ◽

Flow Distribution ◽

Pressure Profile ◽

Gas Channel ◽

The Core ◽

Hydraulic Design ◽

Distribution Process ◽

Pros And Cons ◽

Particle Bed ◽

Chemical Propulsion

Nuclear thermal propulsion (NTP) is regarded as the preferred option for the upcoming crewed interstellar exploration due to its excellent performance compared to the current most advanced chemical propulsion systems. Over the past several decades, many novel concepts have been proposed, among which the particle bed reactor (PBR) is the most efficient, compact, and lightweight method. Its unique features, such as the extremely high power density and the radial flow path of coolant in the fuel region, introduce many challengeable issues to the thermal hydraulic design of PBR, with the flow distribution being representative. In this work, the flow distribution process within the core is analyzed based on the understanding of the axial pressure profile in a dummy PBR. A “flow shift” phenomenon leading to the hot spot in the core is introduced first, and three methods, i.e., decreasing the pressure drop within the hot gas channel, increasing the flow resistance on the cold frit or hot frit, and changing the flow pattern from “Z” to “U”, are proposed to reduce the “flow shift” and the consequent temperature mal-distribution. The pros and cons of using cold frit or hot frit to distribute the coolant are also discussed. Finally, by using three numerical examples, these analyses are demonstrated. The findings here may provide technical support for PBR design.

Download Full-text

Method for Computing Flow Distribution and Pressure Drop in Multichambered Baghouses

JAPCA ◽

10.1080/08940630.1988.10466351 ◽

1988 ◽

Vol 38 (1) ◽

pp. 39-45

Author(s):

Duane H. Pontius ◽

Wallace B. Smith

Keyword(s):

Pressure Drop ◽

Flow Distribution

Download Full-text

Pressure drop axial distribution uniformity of the particle bed in the radial bed

Korean Journal of Chemical Engineering ◽

10.1007/s11814-021-0818-0 ◽

2021 ◽

Author(s):

Tianhang Wu ◽

Dewu Wang ◽

Ruojin Wang ◽

Bin Zhao ◽

Meng Tang ◽

...

Keyword(s):

Pressure Drop ◽

Axial Distribution ◽

Distribution Uniformity ◽

Particle Bed

Download Full-text

Study on Temperature Distribution of Pebble-Bed HTR Fuel Element by Using Boundary Element Method

Volume 6B: Materials and Fabrication ◽

10.1115/pvp2013-97454 ◽

2013 ◽

Author(s):

Haitao Wang ◽

Xin Wang

Keyword(s):

Fuel Element ◽

Boundary Element ◽

Large Scale ◽

Maximum Temperature ◽

Element Formulation ◽

Desktop Computer ◽

Pebble Bed ◽

Graphite Matrix ◽

Fuel Particles ◽

Fuel Elements

Spherical fuel elements with a diameter of 60mm are basic units of the nuclear fuel for the pebble-bed high temperature gas-cooled reactor (HTR). Each fuel element is treated as a graphite matrix containing around 10,000 randomly distributed fuel particles. The essential safety concept of the pebble-bed HTR is based on the objective that maximum temperature of the fuel particles does not exceed the design value. In this paper, a microstructure-based boundary element model is proposed for the large-scale thermal analysis of a spherical fuel element. This model presents detailed structural information of a large number of coated fuel particles dispersed in a spherical graphite matrix in order that temperature distributions at the level of fuel particles can be evaluated. The model is meshed with boundary elements in conjunction with the fast multipole method (FMM) in order that such large-scale computation is performed only in a personal desktop computer. Taking advantage of the fact that fuel particles are of the same shape, a similar sub-domain approach is used to establish the temperature translation mechanism between various layers of each fuel particle and to simplify the associated boundary element formulation. The numerical results demonstrate large-scale capacity of the proposed method for the multi-level temperature evaluation of the pebble-bed HTR fuel elements.

Download Full-text

Research on Influence of Different Simulation Methods of Bypass Flow in Thermal Hydraulic Analysis on Temperature Distribution in HTR-10

Science and Technology of Nuclear Installations ◽

10.1155/2020/4754589 ◽

2020 ◽

Vol 2020 ◽

pp. 1-8

Author(s):

Shiyan Sun ◽

Youjie Zhang ◽

Yanhua Zheng

Keyword(s):

Temperature Distribution ◽

Reactor Core ◽

Flow Distribution ◽

Maximum Temperature ◽

Flow Ratio ◽

Hydraulic Analysis ◽

Bypass Flow ◽

Pebble Bed ◽

The Core ◽

Thermal Hydraulic Analysis

In pebble-bed high temperature gas-cooled reactor, gaps widely exist between graphite blocks and carbon bricks in the reactor core vessel. The bypass helium flowing through the gaps affects the flow distribution of the core and weakens the effective cooling of the core by helium, which in turn affects the temperature distribution and the safety features of the reactor. In this paper, the thermal hydraulic analysis models of HTR-10 with bypass flow channels simulated at different positions are designed based on the flow distribution scheme of the original core models and combined with the actual position of the core bypass flow. The results show that the bypass coolant flowing through the reflectors enhances the heat transfer of the nearby components efficiently. The temperature of the side reflectors and the carbon bricks is much lower with more side bypass coolant. The temperature distribution of the central region in the pebble bed is affected by the bypass flow positions slightly, while that of the peripheral area is affected significantly. The maximum temperature of the helium, the surface, and center of the fuel elements rises as the bypass flow ratio becomes larger, while the temperature difference between them almost keeps constant. When the flow ratio of each part keeps constant, the maximum temperature almost does not change with different bypass flow positions.

Download Full-text

Two Efficient Methods for Gas Distributive Network Calculation

10.20944/preprints201808.0277.v1 ◽

2018 ◽

Author(s):

Dejan Brkić

Keyword(s):

Pressure Drop ◽

Thermodynamic Properties ◽

Gas Flow ◽

Flow Distribution ◽

Gas Pipeline ◽

Gas Flow Rate ◽

Closed Loops ◽

Loop Method ◽

Hardy Cross ◽

Flow Through

Today, two very efficient methods for calculation of flow distribution per branches of a looped gas pipeline are available. Most common is improved Hardy Cross method, while the second one is so-called unified node-loop method. For gas pipeline, gas flow rate through a pipe can be determined using Colebrook equation modified by AGA (American Gas Association) for calculation of friction factor accompanied with Darcy-Weisbach equation for pressure drop and second approach is using Renouard equation adopted for gas pipeline calculation. For the development of Renouard equation for gas pipelines some additional thermodynamic properties are involved in comparisons with Colebrook and Darcy-Weisbach model. These differences will be explained. Both equations, the Colebrook’s (accompanied with Darcy-Weisbach scheme) and Renouard’s will be used for calculation of flow through the pipes of one gas pipeline with eight closed loops which are formed by pipes. Consequently four different cases will be examined because the network is calculated using improved Hardy Cross method and unified node-loop method. Some remarks on optimization in this area of engineering also will be mentioned.

Download Full-text

Airbag deployment: Infrared thermography and evaluation of thermal damage

Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine ◽

10.1177/0954411919832038 ◽

2019 ◽

Vol 233 (4) ◽

pp. 424-431 ◽

Cited By ~ 1

Author(s):

Ehsan Shakouri ◽

Alimohammad Mobini

Keyword(s):

Infrared Thermography ◽

Chemical Reaction ◽

Direct Contact ◽

Thermal Damage ◽

Maximum Temperature ◽

Time Intervals ◽

Hot Gas ◽

Exothermic Chemical Reaction ◽

Zero Moment ◽

Airbag Deployment

The performance of airbag and its deployment are based on a fast exothermic-chemical reaction. The hot gas resulting from the chemical reaction which results in airbag deployment can cause thermal damage and skin burning for the car passenger. The thermal burns due to airbags are of two types: burns due to direct contact with the airbag surface and burns resulting from exposure to the hot gas leaving the deflation vents of the airbag. In this research, for experimental study of the burns resulting from exposure of the skin to airbag, using infrared thermography, the extent of temperature rise of the airbag surface was detected and measured from the zero moment of its inflation. Next, using Henriques equation, the extent of thermal damage caused by airbag deployment and its resulting burn degree was calculated. The results indicated that during the inflation of airbag, the maximum temperature of its surface can be 92 °C ± 2 °C. Furthermore, if the vehicle’s safety system functions within the predicted time intervals, the risk of thermal damage is virtually zero. However, if even a slight delay occurs in detachment of the passenger’s head and face off the airbag, second- and third-degree burns could develop.

Download Full-text

Experimental study of lubricant-derived ash effects on diesel particulate filter performance

International Journal of Engine Research ◽

10.1177/1468087419874577 ◽

2019 ◽

pp. 146808741987457 ◽

Cited By ~ 1

Author(s):

Jun Zhang ◽

Yanfei Li ◽

Victor W Wong ◽

Shijin Shuai ◽

Jinzhu Qi ◽

...

Keyword(s):

Pressure Drop ◽

Diesel Particulate Filter ◽

Particulate Filter ◽

Maximum Temperature ◽

Particle Emissions ◽

Diesel Particulate ◽

Particulate Filters ◽

Filter Performance ◽

Soot Loading ◽

Active Regeneration

Diesel particulate filters are indispensable for diesel engines to meet the increasingly stringent emission regulations. A large amount of ash would accumulate in the diesel particulate filter over time, which would significantly affect the diesel particulate filter performance. In this work, the lubricant-derived ash effects on diesel particulate filter pressure drop, diesel particulate filter filtration performance, diesel particulate filter temperature field during active regeneration, and diesel particulate filter downstream emissions during active regeneration were studied on an engine test bench. The test results show that the ash accumulated in the diesel particulate filter would decrease the diesel particulate filter pressure drop due to the “membrane effect” when the diesel particulate filter ash loading is lower than about 10 g/L, beyond which the diesel particulate filter pressure drop would be increased due to the reduction of diesel particulate filter effective volume. The ash loaded in the diesel particulate filter could significantly improve the diesel particulate filter filtration efficiency because it would fill the pores of diesel particulate filter wall. The diesel particulate filter peak temperature during active regeneration is consistent with the diesel particulate filter initial actual soot loading density prior to regeneration at various diesel particulate filter ash loading levels, while the diesel particulate filter maximum temperature gradient would increase with the diesel particulate filter ash loading increase, whether the diesel particulate filter is regenerated at the same soot loading level or the same diesel particulate filter pressure drop level. The ash accumulation in the diesel particulate filter shows little effects on diesel particulate filter downstream CO, total hydrocarbons, N2O emissions, and NO2/NO x ratio during active regeneration. However, a small amount of SO2 emissions was observed when the diesel particulate filter ash loading is higher than 10 g/L. The ash accumulated in the diesel particulate filter would increase the diesel particulate filter downstream sub-23 nm particle emissions but decrease larger particle emissions during active regeneration.

Download Full-text