DOCSLIB.ORG

Effect of Triangular Fins on Critical Heat Flux in Ethanol-Cooled Combustion Chamber

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Effect of Triangular Fins on Critical Heat Flux in Ethanol-Cooled Combustion Chamber Trans. JSASS Aerospace Tech. Japan Vol. 10, No. ists28, pp. Pa_43-Pa_48, 2012 Original Paper Effect of Triangular Fins on Critical Heat Flux in Ethanol-cooled Combustion Chamber 1) 2) 1) 1) 1) 1) By Masao TAKEGOSHI , Ryosuke SUZUKI , Toshihito SAITO , Fumiei ONO , Tetsuo HIRAIWA and Sadatake TOMIOKA 1) Japan Aerospace Exploration Agency, Kakuda, Japan 2) Tohoku University, Sendai, Japan (Received June 27th, 2011) A pressure-fed engine with a regeneratively-cooled combustion chamber is studied in JAXA. Operation chamber pressure is approximately 1 MPa. A proposed propellant combination is liquid oxygen and ethanol. However, it is necessary to understand the critical heat flux when ethanol is used as a coolant for regeneratively-cooled combustion chamber because the saturation pressure of it is 6.3 MPa. In general, it is known that the cooling wall with fins improves the cooling performance. In this study, the effect of triangular fins on critical heat flux of ethanol in ethanol-cooled combustion chamber was investigated. As the result, it was found that the critical heat flux of cooling wall with triangular fins was 23 % higher than that of that without fin in the same velocity condition of the coolant. The critical heat flux increases by the triangular fins on the cooling surface due to the effect of the combination cooling with film boiling and nucleate boiling. Key Words: Ethanol, Critical Heat Flux, Triangular Fin, Regenerative Cooling, Nucleate Boiling Nomenclature Ishimoto discussed to develop a small rocket-powered winged vehicle that will be launched from a platform aircraft and has P : pressure also conducted a concept study of such a flight demonstrator1). Pc : chamber pressure Because the ethanol is nontoxic, liquid at the room 2) Pf : fuel injection pressure temperature, and easy to handle as a fuel , rocket engines Po : oxygen injection pressure using LOX and ethanol seemed to be the most suitable for this q : heat flux reusable experimental vehicle. JAXA has started the r : radius development of technologies necessary to realize the reference 1) A pressure-fed engine with a regeneratively-cooled t : thickness systems . rocket combustion chamber3) was started to study in 2009. TC : thermocouple Operation chamber pressure is approximately 1 MPa. However, Tsat : saturation temperature it is necessary to understand the critical heat flux when it is Twall : wall temperature V : velocity used as a coolant for regeneratively-cooled combustion chamber because the saturation pressure of it is 6.3MPa. ΔT : degree of super heat sat Previous studies4,5) of critical heat flux for fluids at λ : thermal conductivity subcooling conditions have been conducted using electrically Subscripts heated tubes, and they indicated that the cooling performance bulk : bulk of ethanol was not enough for regeneratively-cooled c : surface of cooling side combustion chamber. On the other hand, Niino et al.6) reported CHF : critical heat flux that the critical heat flux was increased by the cooling wall EA : ethanol with triangular fins of water-cooled chamber. h : surface of heated side In this study, the effect of triangular fins on critical heat sub : subcooling flux of ethanol in ethanol-cooled combustion chamber was TC : at the position of thermocouple investigated experimentally. 1. Introduction 2. Experimental Procedure and Experimental Apparatus Experimental research work for the ethanol propulsion 2.1. Test facility and test apparatus system has been performed in JAXA/Space Transportation Figure 1 shows the simplified schematic of the test facility Mission Directorate as study for future reusable launch to measure the critical heat flux of ethanol under sub-cooling vehicle. LOX/ethanol rocket engine is thought to be one of the conditions. Combustion gas generated by gaseous hydrogen promising candidates to realize a next generation’s reusable and gaseous oxygen was used as a heat source. The launch vehicle with low cost and high frequency. Fujii and combustion chamber consisted of three water-cooled Copyright© 2012 by the Japan Society for Aeronautical and Space Sciences and ISTS. All rights reserved. Pa_43 Trans. JSASS Aerospace Tech. Japan Vol. 10, No. ists28 (2012) chambers and an ethanol-cooled chamber. Figure 2(a) shows chamber is 50 mm in diameter. The throat is 26 mm in the schematic of the test chamber. The lengths of water-cooled diameter. chambers were 100 mm and 142 mm for cylinder parts, and Eight co-axial injectors, each with an oxygen post and a 70 mm for the nozzle throat, respectively. The length of the hole in the faceplate, were installed at equal distance around ethanol-cooled cylinder chamber was 20 mm. The combustion the torch igniter. The inner path of the co-axial injector was for gaseous oxygen and outer path was for gaseous hydrogen. Vent The oxygen injector posts and faceplate were made of nickel. Regulated He supply The faceplate had twenty-four cooling fuel injection holes, each being 0.5 mm in diameter. Ethanol Two kinds of cooling passage were used for ethanol-cooled Tank combustion chambers. One is the cooling surface with (supply) triangular fins. Another is the cooling surface with flat surface. Figure 2(b) shows the contour of the cooling passage in detail. Flow meter The height of each fin is 1.5 mm. The coolant flows in the Cooling water P TC direction of the circumference of the chamber. The width of supply the cooling passage is 10 mm in width and 3mm in height. The thickness of the chamber wall was 4 mm. The wall Regulated temperature at the 2 mm from the surface and the bulk GH2 supply P TC Test section temperature of coolant ethanol was measured by thermocouple Torch Igniter at the position of 3/8 rounds away from the inlet. The pressure Combustion Hot gas flow of coolant ethanol was also measured with pressure chamber transducers at the position of 3/8 rounds away from the inlet. P TC 2.2. Procedure and test sequence Regulated In the electrically heated tube tests, the method that the Pc P TC GO2 supply heating power was increased in steps until the heat flux Vent approached a critical heat flux while keeping the flow rate and Cooling water pressure of coolant stable was used. In this study, the flow rate ｊettison Ethanol of ethanol at the critical heat flux was measured by decreasing Tank (return) the pressure of ethanol supply tank while keeping the chamber pressure stable. Fig. 1. Simplified schematic of the test stand for evaluation of the Figure 3 shows a typical test sequence of heating test. A cooling performance. typical test run started by filling the supply tank with Chamber pressure Fuel supply Water-cooled chamber Ethanol Fuel Spark supply plug Oxygen supply Torch igniter Fuel manifold Oxygen supply 100 142 20 41.5 Thermocouple Water-cooled nozzle (a) water-cooled chambers and an ethanol-cooled chamber (b) cooling passage with flat surface and with fins Fig. 2. Schematic of heating apparatus. Pa_44 M. TAKEGOSHI et al.: Effect of Triangular Fins on Critical Heat Flux in Ethanol-cooled Combustion Chamber Fig. 3. Typical test sequence. regulated helium gas. First, the shut-off valve for coolant was minutes after the temperature of hardware was steady. opened 8.0 s prior to ignition. The coolant flow was stabilized During tests, combustion chamber pressure (Pc), fuel at flow rate and back pressure set points prior to firing. A injection pressure (Pf), oxygen injection pressure (Po) and torch spark plug was operated 1.0 s prior to GH2 and GO2 coolant pressure (P) were measured with strain-gage pressure injections into the igniter. Though the oxygen supply to the transducers (PG-U series, KYOWA ELECTRONIC igniter was cut off 1.5 s after the onset of the main injection, INSTRUMENTS CO., LTD.). All pressure transducer was the hydrogen supply to the igniter was continued to cool the calibrated with pressure calibrator (Dead weight tester, PD27 injector faceplate. of Nagano Keiki CO., Ltd) before the tests. A sensor for 5 After stabilization of chamber pressure, the supply valve to MPa was used for Pc pressure measurement and coolant the ethanol tank was closed at 10.0 s. As the pressure of pressure measurement; measurement error was ± 0.01 MPa. A ethanol tank decreased automatically, the flow rate of coolant sensor for 10 MPa was used for Pf and Po pressure was decreased gradually. When the critical heat flux was measurement, measurement error being ± 0.02 MPa. reached, the wall temperature at the thermocouple showed a The test stand had turbine-type flowmeters to measure the sharp increase. The sharp increase in wall temperature flow rates of fuel, oxygen and ethanol directly, their indicated the drastic reduction in heat transfer coefficient of measurement error being ± 1 % in volume flow rate. Pressure the fluid as it transitioned to film boiling. When the wall and temperature within the supply lines close to the temperature exceeded 550 K, heating test was stopped flowmeters were monitored to deduce mass flow rate. The automatically. temperatures of coolants were measured by thermocouples of Heat flux was calculated based on the temperature type E (chromel-constantan thermocouple). The electronic difference between inlet and outlet, the specific heat, flow rate, cold junction compensation of acquisition device of National density of the coolant fluid. Coolant side wall temperature was Instruments Corporation was used for the temperature calculated based on the heat flux, conductivity of wall compensating. material, and wall temperature measured by thermocouple. The temperature of the chamber wall at 2 mm from the The heat flux to the wall was controlled by combustion surface was measured by thermocouples, as shown in Fig. 2. pressure. Combustion pressure was kept at constant during The points measured by thermocouples are indicated as TC.
Load more

Recommended publications
  • Nucleate-Boiling Heat Transfer to Water at Atmospheric Pressure
    Scholars' Mine Masters Theses Student Theses and Dissertations 1966 Nucleate-boiling heat transfer to water at atmospheric pressure H. D. Chevali Follow this and additional works at: https://scholarsmine.mst.edu/masters_theses Part of the Chemical Engineering Commons Department: Recommended Citation Chevali, H. D., "Nucleate-boiling heat transfer to water at atmospheric pressure" (1966). Masters Theses. 2971. https://scholarsmine.mst.edu/masters_theses/2971 This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. NUCLEATE-BOILING HEAT TRANSFER TO WATER AT ATMOSPHERIC PRESSURE BY H. D. CHEV ALI - 1 &J '-I 0 ~~ A THESIS submitted to the faculty of THE UNIVERSITY OF MISSOURI AT ROLLA in partial fulfil lment of the requirements for the Degree of MASTER OF SCIENCE IN CHEMICAL ENGINEERING Roll a, Missouri 1966 Approved by / (Advisor ) ii ABSTRACT The purpose of this investigation was to study the hysteresis effect, the effect of micro-roughness and orientation of the heat-trans­ fer surface, and the effect of infra-red-radiation-treated heat-transfer surfaces on the nucleate-boiling curve. It has been observed that there exists no hysteresis effect for water boiling from a cylindrical copper surface in the nucleate-boiling region over the range studied. The nucleate-boiling curve has been found to be independent of micro-roughness and orientation of the heat­ transfer surface. There was no detectable change in the nucleate-boil­ ing characteristics of the heat-transfer surface when the surface was treated with infra-red radiation.
    [Show full text]
  • Prediction of Critical Heat Flux (CHF) for Vertical Round Tubes with Uniform Heat Flux in Medium Pressure Regime
    Korean J. Chem. Eng., 21(1), 75-80 (2004) Prediction of Critical Heat Flux (CHF) for Vertical Round Tubes with Uniform Heat Flux in Medium Pressure Regime W. Jaewoo Shim† and Joo-Yong Park Department of Chemical Engineering, Dankook University, Seoul 140-714, Korea (Received 2 July 2003 • accepted 8 November 2003) Abstract−The description of critical heat flux (CHF) phenomena under medium pressure (10 bar≤P≤70.81 bar) regime is complex due to the large specific volume of vapor and the effect of buoyancy that are inherent in the con- ditions. In this study, a total of 2,562 data points of CHF in uniformly heated round vertical tube for water were collected from 5 different published sources. The data consisted of the following parameter ranges: 93.7≤G (mass ≤ 2 ≤ ≤ ≤ ≤ ≤ ≤ 2 flux) 18,580 kg/m s, 0.00114 D (diameter) 0.03747 m, 0.008 L (length) 5 m, 0.26 qc (CHF) 9.72 MW/m , and −0.21≤L (exit qualities)≤1.09. A comparative analysis is made on available correlations, and a new correlation is presented. The new CHF correlation is comprised of local variables, namely, “true” mass quality, mass flux, tube diameter, and two parameters as a function of pressure only. This study reveals that by incorporating “true” mass quality in a modified local condition hypothesis, the prediction of CHF under these conditions can be obtained quite accurately, overcoming the difficulties of flow instability and buoyancy effects. The new correlation predicts the CHF data are significantly better than those currently available correlations, with average error 2.5% and rms error 11.5% by the heat balance method.
    [Show full text]
  • Experimental Study on Critical Heat Flux Behavior in Single Fuel Pin with and Without Wire Spacer
    EXPERIMENTAL STUDY ON CRITICAL HEAT FLUX BEHAVIOR IN SINGLE FUEL PIN WITH AND WITHOUT WIRE SPACER Dan Tri LE*, Noriaki IN ABA** and Minoru TAKAHASHI** *Department of Nuclear Engineering, Tokyo Institute of Technology Nl-18, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8550, Japan [email protected]. ac .j p **Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology Nl-18, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8550, Japan inaba@2phase .nr.titech. ac.j p [email protected] Abstract: Light water reactor could have fast neutron spectrum with high conversion ratio nearly equal unity by using tight lattice fuel assembly with wire spacer. Besides, the critical heat flux (CHF) data base for grid spacer has a great quantity of studies but it is not in case of wire type. In order to investigate coolability in tight lattice core in boiling water reactor (BWR), an experiment of critical heat flux (CHF) was conducted using single pin flow channels with a heater pin with and without wire. We determined the critical heat flux for this system by varying the inlet temperature from 333 to 373 K and mass fluxes from 200 to 700 kg/m1 2s and the pressure was atmospheric pressure. The result show the CHF data in two-phase flow condition base on inlet and outlet condition in both case of heater pin with and without wire. The CHF values were higher with wire than without wire due to the effect of wire and spiral flow. Keywords: Critical Heat Flux, Tight Lattice, Two-phase Flow, Wire Spacer.
    [Show full text]
  • Critical Heat Flux
    International Journal of Heat and Mass Transfer 43 (2000) 2573±2604 www.elsevier.com/locate/ijhmt Critical heat ¯ux (CHF) for water ¯ow in tubesÐI. Compilation and assessment of world CHF data David D. Hall, Issam Mudawar* Boiling and Two-Phase Flow Laboratory, School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA Received 29 September 1998; received in revised form 24 May 1999 Abstract The nuclear and conventional power industries have spent enormous resources during the past ®fty years investigating the critical heat ¯ux (CHF) phenomenon for a multitude of pool and ¯ow boiling con®gurations. Experimental CHF data form the basis for the development of correlations and mechanistic models and comparison with them is the sole criterion for a reliable assessment of a correlation or model. However, experimental CHF data are rarely published, remaining in the archives of the authors or in obscure technical reports of an organization. The Purdue University-Boiling and Two-Phase Flow Laboratory (PU-BTPFL) CHF database for water ¯ow in a uniformly heated tube was compiled from the world literature dating back to 1949 and represents the largest CHF database ever assembled with 32,544 data points from over 100 sources. The superiority of this database was proven via a detailed examination of previous databases. A point-by-point assessment of the PU-BTPFL CHF database revealed that 7% of the data were unacceptable mainly because these data were unreliable according to the original authors of the data, unknowingly duplicated, or in violation of an energy balance. Parametric ranges of the 30,398 acceptable CHF data were diameters from 0.25 to 44.7 mm, length-to-diameter ratios from 1.7 to 2484, mass velocities from 10 to 134,000 kg m2 s1, pressures from 0.7 to 218 bars, inlet subcoolings from 0 to 3478C, inlet qualities from 3.00 to 0.00, outlet subcoolings from 0 to 3058C, outlet qualities from 2.25 to 1.00, and critical heat ¯uxes from 0.05 Â 106 to 276 Â 106 Wm2.
    [Show full text]
  • Heat and Mass Transfer: Fundamentals and Applications 5Th Edition Download Free
    HEAT AND MASS TRANSFER: FUNDAMENTALS AND APPLICATIONS 5TH EDITION DOWNLOAD FREE Yunus A Cengel | 9780077654764 | | | | | ISBN 13: 9780073398181 Noting that the heat transfer area in this case is A 2rL and the thermal conductivity is constant, the one-dimensional transient heat conduction equation in a cylinder becomes 1 r r. The density of the cylinder is and the specific heat is c. The topic of critical heat flux is covered in Chap ter 10 Boiling and Condensation. Taking the positive direction of x to be from the inner surface to the outer surface, the correct Heat and Mass Transfer: Fundamentals and Applications 5th edition for the convection boundary condition is a k dT 0 dx Heat and Mass Transfer: Fundamentals and Applications 5th edition k b k h T 0 T dT 0 dx Answer a k 1 1 T hT 1 1 dT L dx 2 d k dT L dx T L T h 2 2 Heat and Mass Transfer: Fundamentals and Applications 5th edition h T 2 1 e None of them 2 dT 0 h T1 0 T 1 dx Consider steady one-dimensional heat conduction through a plane wall, a cylindrical shell, and a spherical shell of uniform Heat and Mass Transfer: Fundamentals and Applications 5th edition with constant thermophysical properties and no thermal energy generation. I have taken their services earlier for textbook solutions which helped me to score well. Properties The Heat and Mass Transfer: Fundamentals and Applications 5th edition surface has an absorptivity of 0. The total rate of heat transfer from the black ball is a W.
    [Show full text]
  • Thermal Hydraulics of Water Cooled Divertors
    GA–A23476 THERMAL HYDRAULICS OF WATER COOLED DIVERTORS by C.B. BAXI OCTOBER 2000 DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. GA–A23476 THERMAL HYDRAULICS OF WATER COOLED DIVERTORS by C.B. BAXI This is a preprint of a paper presented at the 21st Symposium on Fusion Technology, September 11–15, 2000 in Madrid, Spain and to be published in Fusion Design and Engineering. Work supported by General Atomics IR&D Funds GA PROJECT 4437 OCTOBER 2000 C.B. BAXI THERMAL HYDRAULICS OF WATER COOLED DIVERTORS ABSTRACT Divertors of several new machines, such as JT-60SU, FIRE, SST-1, ITER-RC and KSTAR, are water-cooled. This paper examines critical thermal hydraulic issues associated with design of such divertors. The flow direction of coolant in the divertor can be either toroidal or poloidal. A quantitative evaluation shows that the poloidal flow direction is preferred, because the flow rate and pumping power are about an order of magnitude smaller compared to the toroidal flow direction.
    [Show full text]
  • UC Berkeley UC Berkeley Electronic Theses and Dissertations
    UC Berkeley UC Berkeley Electronic Theses and Dissertations Title Design and Transient Analysis of Passive Safety Cooling Systems for Advanced Nuclear Reactors Permalink https://escholarship.org/uc/item/0g2353c7 Author Galvez, Cristhian Publication Date 2011 Peer reviewed|Thesis/dissertation eScholarship.org Powered by the California Digital Library University of California Design and Transient Analysis of Passive Safety Cooling Systems for Advanced Nuclear Reactors By Cristhian Galvez A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Engineering – Nuclear Engineering in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Per F. Peterson, Chair Professor Van P. Carey Professor Ehud Greenspan Professor Brian D. Wirth Spring 2011 ABSTRACT Design and Transient Analysis of Passive Safety Cooling Systems for Advanced Nuclear Reactors Cristhian Galvez Doctor of Philosophy in Engineering - Nuclear Engineering University of California, Berkeley Professor Per F. Peterson, Chair The Pebble Bed Advanced High Temperature Reactor (PB-AHTR) is a pebble fueled, liquid salt cooled, high temperature nuclear reactor design that can be used for electricity generation or other applications requiring the availability of heat at elevated temperatures. A stage in the design evolution of this plant requires the analysis of the plant during a variety of potential transients to understand the primary and safety cooling system response. This study focuses on the performance of the passive safety cooling system with a dual purpose, to assess the capacity to maintain the core at safe temperatures and to assist the design process of this system to achieve this objective. The analysis requires the use of complex computational tools for simulation and verification using analytical solutions and comparisons with experimental data.
    [Show full text]
  • A Coupled Wicking and Evaporation Model for Prediction of Pool Boiling Critical Heat Flux on Structured Surfaces H
    Purdue University Purdue e-Pubs CTRC Research Publications Cooling Technologies Research Center 2019 A Coupled Wicking and Evaporation Model for Prediction of Pool Boiling Critical Heat Flux on Structured Surfaces H. Hu Purdue University J. A. Weibel Purdue University, [email protected] S V. Garimella Purdue University, [email protected] Follow this and additional works at: https://docs.lib.purdue.edu/coolingpubs Hu, H.; Weibel, J. A.; and Garimella, S V., "A Coupled Wicking and Evaporation Model for Prediction of Pool Boiling Critical Heat Flux on Structured Surfaces" (2019). CTRC Research Publications. Paper 339. http://dx.doi.org/https://doi.org/10.1016/j.ijheatmasstransfer.2019.03.005 This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for additional information. A Coupled Wicking and Evaporation Model for Prediction of Pool Boiling Critical Heat Flux on Structured Surfaces Han Hu, Justin A. Weibel1, and Suresh V. Garimella1 School of Mechanical Engineering, Cooling Technologies Research Center Purdue University, 585 Purdue Mall, West Lafayette, IN 47907 USA ABSTRACT. Boiling is an effective heat transfer mechanism that is central to a variety of industrial processes including electronic systems, power plants, and nuclear reactors. Micro-/nano- structured surfaces have been demonstrated to significantly enhance the critical heat flux (CHF) during pool boiling, but there is no consensus on how to predict the structure-induced CHF enhancement. In this study, we develop an analytical model that takes into consideration key mechanisms that govern CHF during pool boiling on structured surfaces, namely, capillary wicking and evaporation of the liquid layer underneath the bubble.
    [Show full text]
  • Research Article Application of the Critical Heat Flux Look-Up Table to Large Diameter Tubes
    Hindawi Publishing Corporation Science and Technology of Nuclear Installations Volume 2013, Article ID 868163, 10 pages http://dx.doi.org/10.1155/2013/868163 Research Article Application of the Critical Heat Flux Look-Up Table to Large Diameter Tubes M. El Nakla,1 M. Habib,1 W. Ahmed,1 A. Al-Sarkhi,1 R. Ben Mansour,1 andM.Y.Al-Awwad2 1 Mechanical Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia 2 Consulting Services Department, Saudi Aramco Oil Company, Dhahran 31261, Saudi Arabia Correspondence should be addressed to M. El Nakla; [email protected] Received 13 August 2013; Accepted 10 September 2013 Academic Editor: Atef Mohany Copyright © 2013 M. El Nakla et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The critical heat flux look-up table was applied to a large diameter tube, namely 67 mm inside diameter tube, to predict the occurrence of the phenomenon for both vertical and horizontal uniformly heated tubes. Water was considered as coolant. For the vertical tube, a diameter correction factor was directly applied to the 1995 critical heat flux look-up table. To predict the occurrence of critical heat flux in horizontal tube, an extra correction factor to account for flow stratification was applied. Both derived tables were used to predict the effect of high heat flux and tube blockage on critical heat flux occurrence in boiler tubes. Moreover, the horizontal tube look-up table was used to predict the safety limits of the operation of boiler for 50% allowable heat flux.
    [Show full text]
  • I. STEADY STATE CORE THERMQHYDRAULICS 1.1 Fluid Flow in Channels
    NUMERICAL FLUID FLOW AND HEAT TRANSFER 9846764 CALCULATION (HEATHYD CODE)* R. NABBI Research Reactor Division, Research Center Jiilich, Jiilich, Germany Abstract Under normal operating condition, heat transfer from the fuel plate to the coolant occurs by convection phenomena. In case of force convection, the rate of the heat being transferred is proportional to the temperature difference between plate surface and coolant temperature. In most research reactors of MTR type the coolant flow is turbulent that results in an enhancement of the heat transfer. The matter of fluid flow analysis for the reactor core is the determination of flow rate and pressure losses resulting mainly from irreversible process of friction and velocity and height change. Hydraulic calculation is made using iterative method. The results of this calculation are provided for heat transfer analysis by the HEATHYD code. The physical and mathematical model of the heat transfer of HEATHYD includes the equation for thermal conduction and Newton's law of cooling. After completing experimental verification of the HEATHYD model, it was applied to calculate the thermohydraulics of a plate type MTR. It was assumed that the core consists of 48 fuel elements generating a total power of 30 MW. The coolant flow and heat transfer for the hot channel was analyzed. In the hot channel case, the saturation temperature has been partly exceeded by the clad surface temperature with the result of subcooled boiling. In the case of the average channel, the clad temperature does not reach the saturation temperature. The results of calculations show that the safety margin to flow instability represents the limiting parameter regarding safe design and operation.
    [Show full text]
  • Lattice Boltzmann Simulation of Ferrofluids Film Boiling
    processes Article Lattice Boltzmann Simulation of Ferrofluids Film Boiling Mohammad Yaghoub Abdollahzadeh Jamalabadi 1,2 1 Department for Management of Science and Technology Development, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam; [email protected] 2 Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam Received: 17 June 2020; Accepted: 16 July 2020; Published: 22 July 2020 Abstract: In the present investigation, two phase film boiling of ferrofluids under an external field delivered around a two-dimensional square cross-section heater was investigated using the lattice Boltzmann technique. The purpose of this work is to find the effect of magnetic field magnitude and direction on the Nusselt number in single and double heater geometry. The improving thermal efficiency in the horizontal and vertical placement of heaters is also presented. The governing equations of mass conservation, momentum conservation, and energy conservation are solved by using a central-moments-based Lattice Boltzmann scheme. The air pocket generated around heater raised incorporating magnetic effects. The heat transfer through this advancement has been explored quantitatively and abstractly. The results shows that with the development in the volumetric applied force at the bubble-fluid interface, the bubble boundary layer thickness around the square heater lessened which cause the Nusselt number augmented. Through the parameter study it found that the Nusselt number can be essentially extended by altering the course of magnet shafts, and that film rising outwardly of the bubble. The improvement and advancement of vapour phase in various heater arrangement made two column of bubble rises at the same time, which rose above each heater and in the end changed into one column of bubble.
    [Show full text]
  • Investigation of Compressible Fluid Behaviour in a Vent Pipe During Blowdown
    Department of Chemical Engineering Investigation of Compressible Fluid Behaviour in a Vent Pipe during Blowdown Farhan Liyakat Husain Rajiwate This thesis is presented for the Degree of Master of Philosophy (Chemical Engineering) of Curtin University August 2011 Declaration To the best of my knowledge and belief this thesis contains no material previously published by any other person except where due acknowledgment has been made. This thesis contains no material which has been accepted for the award of any other degree or diploma in any university. Signature: …………………………………………. Date: ………………………... Dedications To Mum and Dad “Never regard study as a duty, but as the enviable opportunity to learn to know the liberating influence of beauty in the realm of the spirit for your personal joy and to the profit of the community to which your later work belongs” Albert Einstein I Abstract In the process industry, upset conditions can result in the release of fluids to the atmosphere. Such a release process is known as ‘Blowdown’. Accurate modeling and prediction of the blowdown process is important in determining the consequences of venting operations and the design conditions required for vent and flare systems. The predicted information such as the rate at which the fluids are released, the total quantity of fluids released and the physical state of the fluid is valuable and helps in evaluating the new process designs, process improvements and improves the safety of the existing processes. Blowdown events, amongst other transient processes, are the subject of particular interest to the chemical, oil/gas, and power industries. In the process plants, particularly in the hydrocarbon industry, there are many large vessels and pipelines operating under pressure and containing hydrocarbon mixture.
    [Show full text]