MITLibraries Document Services Room 14-0551 77 Massachusetts Avenue Cambridge, MA 02139 Ph: 617.253.5668 Fax: 617.253.1690 Email: docs@mit.edu http://Iibraries.mit.edu/docs DISCLAIMER OF QUALITY Due to the condition of the original material, there are unavoidable flaws in this reproduction. We have made every effort possible to provide you with the best copy available. If you are dissatisfied with this product and find it unusable, please contact Document Services as soon as possible. Thank you. Some pages in the original document contain pictures, graphics, or text that is illegible. POST CRITICAL HEAT FLUX HEAT TRANSFER IN A VERTICAL TUBE INCLUDING SPACER GRID EFFECTS by EDWARD M. CLUSS, JR. I S.B., Massachusetts Institute of Technology (1977) SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREM4ENTS FOR THE DEGREE OF MASTER OF SCIENCE at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY (June 1978) Signature of Author. . .-. ,aepartnentof Mechan Certified by•. Cerifi Accepted by . . . . . 1 Engineewng, June 2, 1978 A./I .~~~ . . . ~Thesis Supervisor . . . . . . . . Chairman, Department Committee on Graduate Students iiiE ARCHIVES COW ; 7 ?D~I& 1 7A- 2 POST CRITICAL HEAT FLUX HEAT TRANSFER IN A VERTICAL TUBE INCLUDING SPACER GRID EFFECTS by EDWARD M. CLUSS, JR. Submitted to the Department of Mechanical Engineering on June 2, 1978 in partial fulfillment of the requirements for the Degree of Master of Science. ABSTRACT Theoretical and experimental programs were conducted in order to analyze the supplemental heat transfer, induced by a spacer grid, during an upward post critical heat flux flow in a constant wall temperatyre pipe. A flooding rate of 1 in/sec, equivalent to 18, 720 lbm/hrft , was studied at atmospheric conditions, with hot wall temperatures of 1000°F, 1100°F, 1200°F and 1300°F. Heat flux versus length data was obtained and compared with theoretical predictions. A modified two phase Dittus Boelter correlation was employed to obtain the steady-state heat transfer coefficients. Both entrance and steady-state experimental values correlated well with this model. Results indicate that an increase in heat transfer does occur at the spacer and is primarily a combination of two mechanisms: (1) Increased flow velocity (caused by an area reduction at the spacer) which increases vapor convection and droplet heat transfer. (2) Radiation to liquid deposited on the spacer. The first contribution can be modeled as a multiplying factor of the steady-state heat transfer level while the latter is a localized effect occurring only at the spacer. The combination of both effects caused a threefold heat transfer increase or greater at the spacer location for the flows studied. Radiation, which is directly related to the hot wall temperature, becomes the major contribution at higher temperatures. Thesis Supervisor: Title: Peter Griffith Professor of Mechanical Engineering 3 ACKNOWLEDGEMENTS Financial support for this investigation was provided through a research assistantship, funded by the Nuclear Regulatory Commission. Some portions of the test apparatus were designed and built during earlier heat transfer research by Thomas Smith and Paul Robershotte. The latter also provided numerous suggestions germane to the initial stages of this project. Joseph "Tiny" Caloggero and Fred Johnson provided technical advice and assisted in the mechanical construction of the experimental apparatus. Many thanks to Prudence Young, who typed the final and earlier versions of this report, and to Dave Welland for his painstaking proofreading. Helpful comments and friendship were always abundant from the guys in my office, Mohamed Benchaita, Yin "Clem" Cheung, Joseph Gonzalez-Rivas, and Baldeo Singh. They made the Heat Transfer Lab an interesting place to work. Professor Griffith, my advisor, provided me with an abundance of guidance and pertinent advice throughout the duratien of this project; but more importantly, always retained his optimism, sense of humor, and patience when they were needed the most. Last but never forgotten; special thanks go to my parents, who have continually given me their love and support for all of my endeavors. To them I dedicate this, my final effort at M.I.T. 4 To My Mother, Claire B. Cluss And My Father, Edward M. Cluss 5 TABLE OF CONTENTS PAGE TITLE PAGE . . . . . . . . . . . . . . . . . . . . . . . . ... .·.·.·.·.·.·. 1 ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 ACKNOWLEDGEMENTS . ..... TABLE OF CONTENTS LIST OF FIGURES . . . . . . . . . . . . . . . . 3 . . . . . . . . . . . . . . . . .. . . . . . 5 . . . . . . . . . . . . . . . . . . . . . 7 LIST OF TABLES . . . . . . . . . . . . . . ·. ·. ·. ·. ·. ·. ·. .· .· ·. .·· 9 10 NOMENCLATURE . . . . . . . . . . . . . . . . . . . . . . . ... . .......... 14 CHAPTER I: INTRODUCTION . . . . . . . . . . . . . . . . . ... . .......... 1.1 Loss of Coolant Accident ................ . ............ 14 1.2 Spacer Grid Effects .................. 15 1.3 Previous Experimentation . . . . . . . . . . . . . . . . 17 1.4 Objective of This Work . . . . . . . . . . . . . . . . . 19 CHAPTER II: EXPERIMENTAL PROGRAM . . . . . . . . . . . . . . . 20 2.1 APPARATUS . . . . . . . . . . . . . . . . . . . . . . . 2.1.1 2.1.2 2.1.3 2.1.4 Reactor Model . . . . . . . . . . . Test Loop Description . . . . . . . Test Section Components . . . . . . System Monitoring and Control . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 20 21 25 29 2.2 EXPERIMENTAL PROCEDURE . . . . . . . . . . . . . . . . 31 2.3 DATA REDUCTION .................... 33 CHAPTER III: THEORETICAL ANALYSIS . . . . . . . . . . . . . . 3.1 POST CHF HEAT TRANSFER ................ 3.1.1 Forced Convection Heat Transfer to Vapor . .. 3.1.2 Wall to Droplet Heat Transfer . . . . . . . . . 36 36 37 39 6 PAGE 3.2 SPACER GRID EFFECTS . . . . . . . . . . . . . . . . . . 43 3.2.1 Increased Flow Velocity . . . . . . . . . . . . 3.2.2 Wall to Spacer Radiation . . . . . . . . . . 44 46 . . 51 CHAPTER IV: EXPERIMENTAL RESULTS AND COMPARISON TO THEORY 4.1 Experimental Heat Flux Results . . . . . . . . . . . . 51 4.2 Effective Heat Transfer Addition at Spacer . . . .... 57 CONCLUSIONS AND RECOMMENDATIONS . . . . . . . . . . 62 . . . . . . 62 5.2 Recommendations . . . . . . . . . . . . . . . . . . . . 63 CHAPTER V: 5.1 Conclusions . . . . . . . . . . . . . . . 65 REFERENCES ......................... APPENDIX A: TEMPERATURE CONTROLLER . . . . . . . . . . . . . . 67 APPENDIX B: EXPERIMENTAL DATA ................... . 68 APPENDIX C: THEORETICAL ANALYSIS COMPUTER PROGRAM . . . . . . 72 APPENDIX D: THEORETICAL RESULTS . . . . . . . . . . . . . . . 82 APPENDIX E: WATER AND VAPOR PROPERTIES . . . . . . . . . . . . 91 7 LIST OF FIGURES PAGE FIGURE ... .. . . . . 16 . . . . . . 18 1 PRESSURE HISTORY DURING BLOWDOWN . . . 2 TWO PHASE FLOW REGIMES . . . . . . . . 3 SCHEMATIC OF EXPERIMENTAL APPARATUS . . 22 4 ENTIRE APPARATUS . . . . . . . . . . . . . . . . . . . . 23 5 LOWER PORTION OF APPARATUS . . . . . . . . . . . . . . . 23 6 ELECTRIC PREHEATER . . . . . . . . . . . . . . . . . . . 23 7 PIPE CONNECTOR . . . . . . . . . . . . 8 PIPE WITHOUT COPPER BLOCK 9 PIPE WITH COPPER BLOCK . . . . . . . . . . . . . . . . .. . . . . . . . I . . . ... . . . . . . . . . .. . . . . . . . 23 24 24 10 TEST SECTION WIRING . . . . . . . . . . . . . . 24 11 ENVIRONMENT CHAMBER, CONTROLLER CLOCKS, AND VARIACS . . 24 12 . I .26 EXPERIMENTAL SPACER . . . . . . . . . . . . . .... 13 DETAILS OF 1-7/8 INCH COPPER BLOCK 14 MOUNTING OF THERMOCOUPLES . . . . . . . 15 EFFECT OF ENTRANCE CONFIGURATION ON LOCAL STANTON NUMBER 40 16 TEST SECTION INLET CONFIGURATION . . . . . . . . . . . . 41 17 SPACER IDEALIZATION . . . . . . . . . . . . . . . . . . 48 18 VIEW FACTOR, F, FOR DIRECT RADIATION BETWEEN ADJACENT PERPENDICULAR RECTANGLES . . . . . . . . . 49 19 COMPARISON OF DATA AT 1 IN/SEC AND 1000°F TO THEORY . . 52 20 COMPARISON OF DATA AT 1 IN/SEC AND 1100°F TO THEORY . . 53 21 COMPARISON OF DATA AT 1 IN/SEC AND 1200°F TO THEORY . . 54 22 COMPARISON OF DATA AT 1 IN/SEC AND 1300°F TO THEORY . . 55 , . . . . . . . . . . . , . . ,. 28 30 8 PAGE FIGURE 23 THEORETICAL NONDIMENSIONAL HEAT TRANSFER COEFFICIENT . . 58 24 SUPPLEMENTAL HEAT TRANSFER AT SPACER . . . . . . . . . . 59 25 THEORETICAL BREAKDOWN OF HEAT TRANSFER AT SPACER . . . . 61 26 WALL TEMPERATURE CONTROLLER CIRCUIT DIAGRAM . . . . . . 67 9 LIST OF TABLES TABLE PAGE 1 EXPERIMENTAL PROCEDURE . 32 2 SYSTEM PROPERTIES ................. 91 10 NOMENCLATURE SYMBOL DEFINITION A Area Cp Specific Heat E Energy F Geometric View Factor G Mass Flux H, h Enthalpy Hfg K Heat of Vapor m Mass Flow Rate Nu Nusselt Number P Perimeter, Power Pr Prandtl Number q Heat Transfer R Resistance Re Reynold's Number St Stanton Number T Temperature t Time V Velocity, Voltage X Quality Thermal Conductivity 11 Greek Symbols DEFINITION a Void Fraction Radiating Fraction of Wall at At Time Difference S Effectiveness, Emmisivity p Density a Stefan-Boltzman Constant 1J Viscosity 12 SUBSCRIPTS DEFINITION Cu Copper d Droplet DB Dittus-Boelter DS Droplets at Spacer eq Equilibrium exp Experimental f Liquid G Gross g9 Vapor homo Homogeneous in Inlet L Loss out Outlet PRE Preheater RS Radiation at Spacer S Spacer, Saturation sat Saturation SS Stainless Steel t Total v, ap Vapor vs Vapor at Spacer w Wall x Local, Distance 13 SUBSCRIPTS DEFINITION 1 Perpendicular or Deposition 00 Steady-State 14 CHAPTER I: INTRODUCTION Man's ever increasing demand for energy coupled with dwindling fossil fuel supplies has produced a sharp increase in the cost of conventional power production and has necessitated a switch to alternate but still reliable energy sources, Consequently, following the second World War, the nuclear power industry experienced extensive growth, with the hopes of providing a cheaper and cleaner method of power production. Recently, fears coupling nuclear energy with nuclear weapons and anxiety over a large scale reactor accident have drastically reduced the industry's rate of expansion. It has become increasingly more apparent that the design and construction of only the safest and most reliable reactors will be acceptable to the majority of the population. This concern and controversy has demanded that both commercial reactor producers and the Nuclear Regulatory Commission (responsible for the licensing of nuclear reactors) be extremely cautious and only apply the most conservative reactor design schemes when safety and long term reliability is the question. To insure this reactor dependability, emergency systems are built to handle the most extreme types of accidents. One such hypo- thetical crisis is the "loss of coolant accident" or LOCA. 1.1 LOSS OF COOLANT ACCIDENT The hypothetical loss of coolant accident is a problem highly unlikely to occur but is of great interest as a limiting design case. During this accident, a double guillotine break occurs in the main pipes 15 of the primary loop causing a rapid depletion of the reactor coolant and extreme depressurization of the reactor core. Figure 1,obtained from Hsu (1), shows that inapproximately 30 seconds the pressure can drop from 2300 psig to nearly 50 psig. This subcooled depressurization period isknown as the Blowdown stage and has been modeled extensively by Bdrnard (2). As the rate of pressure drop decreases, the remaining flow may experience several flow reversals, and flashing of liquid into vapor occurs. Due to the high void and low coolant flowrate, dryout occurs on the fuel rod surfaces and the critical heat flux condition isreached. Figure 1 also shows that at approximately 10 seconds after the main pipe's rupture, the emergency cooling system (ECCS) is initiated and water ispumped into the reactor core. When the rising pool of water (traveling typically at 1 in/sec) inthe lower plenum reaches the drted out fuel rods, water isboiled and this resulting two phase flow aids in slowly cooling the upper portions of the rods and their structural supports. Eventually the rising pool of water quenches the fuel rods and a quench front propogates upward. 1.2 SPACER GRID EFFECTS An observation made by Bjornard (2)and other investigators is that there are discrete locations ahead of the quench front where a limited amount of rewetting has already occurred. These positions correspond to the orientation of fuel rod structural supports, known as spacer grids. Apparently, due to mechanical constrictions and distur- 16 in w 0 co lGO 0 0 0 N n I-Q A_1-CD v 0~ Cc: w CD Cr 0 o o o 0 0 9a (6!sd) aJnsaJd . >=j _n> ,..'h-= 3Q * LU CN 0 17 bances, a beneficial effect which aids in the cooling process has been encountered. Two results, therefore, seem likely. Spacer grids may cause local fuel rod rewetting shortly before the neighboring region quenches, and secondly, the heat transfer may be enhanced at these discrete locations both before and after quenching occurs. 1.3 PREVIOUS EXPERIMENTATION A great deal of effort and money has been expended to obtain a better understanding of the flow regimes encountered during a LOCA and their corresponding modes of heat transfer. When dryout occurs on the surface of the fuel rods, there is a departure from nucleate boiling. This regime, known as post critical heat flux (or post CHF), is characterized by a violent increase in wall temperature and rapid decrease in the associated heat transfer coefficient. Possible flow re- gimes that are experienced include inverted annular flow film boiling and dispersed flow film boiling. fractions. The latter occurs at higher void These flow regimes are shown in Figure 2 along with the flow situations encountered prior to CHF. Experimental and theoretical research has been carried on at MIT for several years. Smith (3)studied heat transfer and void frac- tion during upflow while Robershotte (4)performed similar heat transfer experimentation and some associated modeling for the downflow situation. An analytical program was developed by Kaufmann (5)to model heat transfer in inverted annular and dispersed flow film boiling during upflow. Bjrnard (2)developed a computer program package which models the entire 18 DISPERSED FLOW FILM BOILING INVERTED ANNULAR FILM BOILING TRANSITION BOILING NUCLEATE BOILING SINGLE PHASE LIQUID NOT TO SCALE FIGURE 2: TWO PHASE FLOW REGIMES 19 blowdown stage. Currently, Singh (6)is studying the flow reversal phenomenon, characteristic of the saturated depressurization period following blowdown, and the thermal hydraulics of gravity - feed reflood is being investigated by Cheung 7). Gonzalez-Rivas (8)recently con- cluded a void fraction and carryover transient analysis. 1,4 OBJECTIVE OF THIS WORK Virtually no prior experimentation and only minor modeling efforts have been conducted that are directly related to spacer grid effects encountered during the reflood period. As a result, both an experimental and analytical program were developed to investigate this problem, Specifically, upflow will be considered with flow parameters typical of those occurring during reflood. The models employed allow one to make reasonable estimations of the added heat transfer effect of spacer grids during a steady-state, upflow, post critical heat flux situation. 20 CHAPTER II: EXPERIMENTAL PROGRAM 2.1 APPARATUS Equipment employed during this investigation was a combination of that used by Smith (3), Robershotte (4), and additions or alterations performed by the current experimenter. Elaborate efforts were made to insure that the apparatus accurately represents the actual physical situation experienced ina reactor core during a LOCA. 2,1.1 Reactor Model The reactor core consists of a bundle of fuel rods and control rods ina spacer grid assemblage which provides structural support. When boiling occurs low in the bundle during reflood the resulting two phase flow moves vertically past the rod bundle. This flow, external to the rods was experimentally modeled as a two phase internal flow in a tube by matching the external flow's hydraulic diameter, mass flux and Reynolds number. At the discrete spacer grid locations, a flow constriction is incurred and droplet interference isencountered. This external flow behavior was also transformed to a corresponding internal model which accounted for the flow area reduction. The entire experimental system was responsible for providing the correct inlet flow conditions to a constant wall temperature section, which included the spacer model. 21 2.1.2 Test Loop Description A schematic of the entire experimental apparatus is shown in Figure 3 and photographs are presented in Figures 4 and 5. At the start of a cycle, water left a reservoir tank and proceeded, via copper tubing, to a 10 gallon per minute capacity centrifugal pump. Due to the pump's over production, most of the liquid was immediately recycled around it through a bypass valve. The water continuing forward passed through a Fulflo SSHP-2416 filter and was then monitored with a float type flowmeter (Tube #FP-1/2-27-6-10/55, Float #GUSVT-40T60). Fine ad- justments of the flow rate were made by valves located at either end of the flowmeter. Water next entered a shell and tube 40 psi steam preheater in order that the liquid subcooling be reduced. A recirculating valve was employed during start up operations in order that thermal time constants be reduced in the main test section. During steady state operation, however, all of the liquid traveled past the recirculating valve and through the four-way valve, advancing towards the electric preheater. The electric preheater, a 3/8 inch 304 stainless steel pipe (.675 inch O.D., .493 inch I.D.) was heated with a direct current generator capable of producing 45 KW of power. Although a fraction of this power output was required, the cables connecting the preheater and generator were water cooled. A photograph of the electric preheater appears in Figure 6. Voltage was measured directly across the electric preheater; whereas current measurements were obtained from the voltage drop across a cali- ') , 0z 9 I F hiac w I-. 4 w I !i hi 4 I- CD a_I a Li I- 0 LiX LLI X '- 0 tL < CC /- LL 13Li '-U hi IC L.L i-) 2 'I I.JAl c. U. C-) I) E IL Li. ,_ CY~ !, cchc 0c 23 Figure 4. Figure 6. Entire Apparatus Electric Preheater Figure 5. Lower Portion of Apparatus Figure 7. Pp onco 24 Figure 8. Figure 10. Pipe Without Copper Block Test Section Wiring Figure 9. Figure 11. Pipe with Copper Block Environment Chamber, Controller Clocks, and Variacs 25 brated NBS shunt resistor located on the generator console. Teflon disks (1/16 inch thick) inserted ina specially produced pipe connector shown in Figure 7, electrically insulated the preheater from the neighboring test loop elements. Constant monitoring of the preheater's power level and temperature were required to guard against pipe burnout and rupturing since this was a constant heat flux mode of heat transfer. The low quality steam produced in the electric preheater then entered the main test section, wall temperature of which was controlled and set at a constant temperature, Heat, added to maintain the fixed wall temperature, was measured and recorded inorder that heat flux versus length data could be obtained. A more complete explanation of the components involved in this process will be presented in the next two sections. Steam, exiting from the main test section, re-entered the copper tubing network and was desuperheated and subcooled ina condenser. Liquid produced inthe condenser, returned to the system reservoir and awaited further recycling. 2.1.3 Test Section Components The test section consisted of a 304 stainless steel pipe with a "spacer" internally welded to it. All instrumentation and related components were located along a 22 inch stretch of the pipe; however, a short entrance length and longer exiting one increased the pipe's overall length to 34 inches. The spacer, shown inFigure 12, was welded at the 11-1/4 inch mark along this 22 inch stretch, inorder that a steady-state flow could be established both before the spacer and downstream of t. Figure 17, in Chapter 3, illustrates the spacer with a 26 J - ! II el a Li Cc -CL en 1- X: Lii 0_ I 00% ii 0 mu _ owk CD Lii §_Lr-m K~~~~~~~~~~~~~~~~~c ' ll 0 z 0 LL 27 portion of the stainless steel pipe wall, Direct contact conduction heating from hot copper blocks supplied the test section with the required heat flux spikes along its length. The copper blocks were made from 4 inch diameter cylindrical copper, which was cut into 120 ° sectors and held tightly against the stainless steel pipe with hose clamps. Copper block heights of 7/8 inch, 1-7/8 inch, and 2-7/8 inch were employed with gaps averaging 1/8 inch between neighboring blocks. Holes were drilled and reamed radially into the blocks, 1 inch apart vertically and separated by 40° cir- cumferentially. Figures 8 and 9 show the stainless steel pipe before and after mounting a copper block. Details of a 1-7/8 inch block are illustrated in Figure 13, Pressed into the radially drilled holes and supplying heat to the copper blocks were 1/4 inch diameter, 1-1/2 inch long, Hotwatt AC resistance cartridge heaters. Each heater was capable of delivering up to 120 watts individually and 198 heaters were uniformly distributed over the 22 inch length, Voltage supplied to the cartridge heaters originated from 10 variable transformers (Variacs), each with a 140 volt/ 10 amp power potential. A total of 10 copper blocks (30 sections) were used such that there was a one to one correspondence between blocks and variacs, This enabled the power delivered to each block to be independently determined and ten individual heat flux spikes established. Since more experimental accuracy isdesired at the spacer, shorter copper blocks were located nearby. Hence, there were two 7/8 inch length blocks used by the spacer and four each of the larger two sizes elsewhere. 28 4' __ IA r _ r rl-A 0a ['7/8" L 0 L a 0 COPPER r STAINLESS PIPE STEEL - ---- FIGURE 13: DETAILS OF 1-7/8 INCH COPPER BLOCK 29 This assortment, including gaps, accounted for the 22 inch total length. Surrounding the block assemblage and blanket of asbestos insulation was an aluminum environment chamber with pyrex windows. This box was filled with nitrogen and served to reduce oxidation of the copper blocks. 2.1.4System Monitoring and Control Instrumentation was primarily concerned with monitoring and establishing a constant wall temperature in the test section. Temperature readings were obtained using chromel-alumel thermocouples throughout the entire assemblage. At the test section, a total of 30 thermocouples were employed, 3 each at 10 different axial positions. The locations were chosen such that each thermocouple corresponded to one of the 30 copper block pieces. Grooves were cut into the stainless inorder to recess the thermocouples inside of the pipe wall, as shown in Figure 14, and insulation was packed on top to insure accurate readings. All 30 thermocouples were monitored and of these, 10 also served as the initial link inthe closed loop constant wall temperature controller. Ten temperature controller circuits (one per block) each compared a different block's thermocouple output to a reference voltage which was set to correspond to the desired wall temperature. A comparator turned a power relay on ifthe temperature measured was 10°F below the reference point and turned the power relay off if the temperature measured was 10O°F above it. The power relay performed two tasks. One, itdetermined whether current could flow through a Variac and hence if power would be delivered to the block, and two, it turned a sweep hand cr -j 0_ C) t3 C-, C w I- .0 0 CE CD 6-4 I-- 2i U- 31 clock on and off which measured the duration of power flow. A circuit diagram of this controller, originally designed by Robershotte (4), is presented inAppendix, A, Figure 26. Photographs of the electrical connections between the test section and terminal blocks; and the environment chamber, controller clocks, and Variacs are shown in Figures 10 and 11. Due to the comparitor's hysterisis and the Variac's voltage setting, a duty cycle resulted which required a 20 minute total run time for proper averaging. Since the voltage level of a Variac was kept constant during any given run, the total energy transferred to a block is simply: E = PAt (2.1) where P isthe constant power delivered to the cartridge heaters when the variac ison and At isthe time recorded on the clock. The gross heat flux then for a 20 minute run is: (q/A) G = E/At(20) (2.2) where At isthe inside area of the tube. 2.2 EXPERIMENTAL PROCEDURE A standard procedure was followed for each individual run executed with the apparatus. A cursory description of the steps involved will be presented here and a tabular form may be consulted in Table 1. Initially, a desired wall temperature was chosen and the corresponding controller reference voltage set. Estimates of the test section 32 TABLE 1 EXPERIMENTAL PROCEDURE I. Initial Preparation 1) Choose desired wall temperature and set corresponding controller reference voltage 2) Estimate test section power requirements and set Variac voltage level 3) Calculate required amount of preheating 4) Reset clocks II. Start Up Operations 1) Open condenser and cooler water valves 2) Bleed nitrogen into environment chamber 3) Open recirculation and steam valves 4) Turn pump and test section power on 5) Check thermocouples and flowrate 6) When test section obtains desired temperature, close recirculating valve and turn electric preheater on. III. Steady-State and Shutdown Procedure 1) Turn clocks on 2) Monitor and record flow rate, preheater power level, and temperatures 3) Shut down system and turn off clocks after 20 minutes 4) Record elapsed time on clocks, Variac voltages, cartridge resistances, etc. 33 power requirements were made and Variacs turned to the proper voltage levels. Also calculations pertinent to the flow's quality (and hence Reynolds Number) were made inorder to determine the required amount of preheating. During start up operations, the generator cable coolant and condenser water were allowed to flow and nitrogen was bled into the environment chamber. Next the recirculation valve and steam valve were opened; and the pump and test section power turned on, The flow rate was established while the thermocouples were being monitored. Once the test section obtained its desired temperature, the recirculating valve was closed and the electric preheater turned on. After the entire system reached steady-state, the clocks were turned on the the run was begun. During the following 20 minutes, the flowrate, preheater power level, and temperatures were monitored and adjusted accordingly. When the run was completed, the time elapsed on each clock was recorded; and resistance measurements of the cartridge heaters conducted, testing for burnouts, Also the flowrate, wall temperature, variac settings, preheater power level and observations were noted for data reduction and further analysis. 2.3 DATA REDUCTION The total average power to each block isequal to the rate of energy dissipation in the cartridge heaters. The total resistance of n parallel heaters ina given block isRt, where: n 1 = Rt : li =1 Ri (2.3) 34 The gross heat transfer rate, then, isdependent on this resistance, a Variac's voltage setting, and the ratio of time on to the total run time. G= trun V2 ) ( ton F {T ) (3.412) trun ~~~~~~~(2.4) (2.4) where 3.412 isa conversion factor from Watts to Btu/hr. Not all of this gross energy transfer directly heats the test section. Some energy is lost to the environment and thermal capacitance effects may occur in the stainless steel pipe or copper blocks. qG = qnet + qL + [(lnCp) SS + (Cp) ]dT Cu (2.5) Due to the cyclis nature of the heating process and steady state conditions; however, t I =0~~~ ~dT (2.6) This reduces Equation 2.5 to: qnet qG- qL (2.7) Heat losses to the environment were measured before each run and deducted from the calculated gross heat transfer, yielding the net heat transferred to the test section. Knowing qnet' an experimental heat transfer coefficient could be obtained with A = At. 35 hexp = (q/A)net. T - T wall - sat (2.8) )( Itis also necessary to know the entering equilibrium quality and hence, also the entering enthalpy to the test section. Since the fluid temperature entering the preheater, Ten t, was known, the amount of superheat enthalpy was calculated from an energy balance at the electric preheater Hin = (Tin - Tsat) qPRE (2.9) m The difference intemperature between Tin and Ta t in Equation 2.9 represents the amount of enthalpy required to eliminate the subcooled liquid. The equilibrium quality entering the test section is then, (X ) eq in = H. (2.10) in Hfg The inlet equilibrium quality can not be calculated for subsequent blocks using (itl) Xeq (i+l) = qnet (i) +Xeq (2.11) (I)(Hfg) which isan energy balance performed on each test section increment. 36 CHAPTER II I: THEORETICAL ANALYSIS 3.1 POST CHF HEAT TRANSFER During an analysis dealing with a two phase flow, proper iden- tification must be made of the equivalent single phase properties. In this investigation, an effective equilibrium vapor Reynolds Number is applied which incorporates the mass flux, quality, and void fraction: Re = GD Xeq (3.1) a v The vapor flow isconsidered turbulent when Rev > 3000. Inthe dis- persed flow region, a isapproximately equal to 1.0, indicating that the void fraction may be neglected when testing for turbulence. Thus, turbulent flow occurs when GD X eq > 3000 (3.2) v The total heat flux inthis situation is the result of two contributions. (q/A) = (q/A)v + (q/A)d (3.3) The first term, (q/A)v, represents wall to vapor forced convection heat transfer; while (q/A) d is the wall to droplet mode of heat transfer. 37 3.1.1 Forced Convection Heat Transfer to Vapor Dittus-Boelter (9)correlated data for a forced convec- tion single phase flow ina pipe and established an empirical equation for a heat transfer coefficient. Inthis two phase study, the single phase Reynolds Number used by Dittus-Boelter is replaced by the effective Reynolds Number in Equation 3.1 yielding: .8 hDB = (.023) D Kv (Re)v .4 (Pr) v (3.4) Since thermal equilibrium is not insured, this heat addition can either increase the quality or superheat the existing vapor. If no superheat- ing occurs (typical of higher mass velocities), and equilibrium model may be employed, (q/A)v = hDB (Twall - Tsat) Vapor properties are evaluated at the saturation temperature. (3.5) During lower mass velocities, however, a model which assumes only superheating ismore accurate. Inthis case, vapor properties are calculated at the actual vapor temperature. (q/A)v = hDB (Twall - Tva p ) (3.6) Equation 3.5 is known as the "Equilibrium Model" or "Dougall-Rohsenow Limit", while Equation 3.6 is called the "Fixed Vapor Fraction Model" or 38 "Fixed Gx Model". The present investigation utilizes the latter model, since flows with mass velocities typically encountered during reflood ina reactor have been modeled more successfully with this formulation (4). This decision, however, is not of great consequence, since use of the equilibrium model would only slightly alter the primary results being sought. The vapor temperature is found by performing a control volume heat balance on a test section increment. Heat entering the vapor is simply, qv = x ) Cp (Tout Tin) (3.7) The mean value of the inlet and outlet temperatures is the vapor temperature; Tvap = () Tin + Tout) (3.8) This scheme, which calculates Tvap, isan iterative one, since the vapor properties used to evaluate Equation 3.4 for the heat transfer coefficient are dependent on this temperature. It is necessary to first estimate the vapor temperature, then evaluate the vapor properties, calculate the heat transfer coefficient, and apply Equation 3.6. Next, an energy balance isconducted with Equations 3.7 and 3.8 yielding an updated approximation for the actual vapor temperature. Only a few iterations are required with this method and convergence is quickly obtained. 39 The method of evaluating the wall to vapor heat transfer assumes a fully-developed flow. Since a development length will be ex- perienced, entrance effects must be accounted for. Figure 15, reproduced from ESDU (1968) (10), gives plots of three entrance effects based on different entrance configurations, This figure shows the ratio of the local Stanton Number to the fully developed value, where Stx = Nu RePr = h D (3.9) k-0ePr The actual heat transfer coefficient compared to its fully-developed value is proportional to the corresponding Nusselt numbers, and hence, also to the Stanton quantities. hx h = NUx Rii = Stx St (3.10) - Apparatus utilized in this research (see Chapter II)used an electrically insulating pipe coupler, which behaves like an orifice to the flow. A short calming distance of four inches is then encountered followed by a jump in temperature at the heated section, as illustrated in Figure 16. Although none of the entrance configurations exactly match this situation, cases 2 and 3 provide a range in which the anticipated entrance effects should lie. 3.1.2 Wall to Droplet Heat Transfer The second and less pronounced mode of heat transfer in tin An 0 CX Or 0 z -J U C, J C- 0 0 p- X I-Q LL 0 CD LU LU U0 FU LLJ LL LU FJ u LL I- LU - LU _ 4: Olor cn (1) _ 41 i w L IU) L 0 14 L 0z C I-L3. C Cl) w0. (..) C,) 4 L c I-LU w -mj z wi w .J C( !-ILAJ C,) (./3 I- C,-) F- LI I- t~O LU U- n U 42 Equation 3.3 is the wall to droplet heat transfer term, (q/A)d. An elusive quantity to obtain despite recently intensified research programs, this contribution is due to droplet evaporization upon entering the vapor boundary layer. A single droplet analysis was performed by Ganic (11), resulting in an expression for the wall to droplet heat flux term; (q/A)d = (l-a) pf Hfg V1 e (3.11) where a is the void fraction, pf, the liquid density, Hfg, the heat of vaporization, V the perpendicular or deposition velocity, and the effectiveness or percentage of drop evaporization. , Due to the single droplet model, this expression has a high void requirement. If the void were to significantly decrease, droplets colliding with other droplets would begin reducing the actual droplet and wall interaction. Hence, the major restriction placed on Equation 3.11 is that it not be applied when voids are less than 98%. A second limitation is that there be enough vapor to ensure a turbulent dispersed flow. To fully understand Equation 3.11, each term must be individually defined. The most common definition employed for the void fraction during upflow is the homogeneous model, where the liquid velocity is assumed equal to the vapor velocity due to the interfacial drag force. ahomo Cthomo p= 1 +(X Pf + l (193,12) 3P 43 Liquid density and heat of vaporization are determined by the system's temperature and pressure, The deposition velocity was determined to be a function of vapor velocity and vapor Reynolds Number by Liu (12). -.125 V1 = .0289) Vv (Re)v (3.13) Effectiveness, , perhaps the most difficult value to pinpoint, was investigated extensively by Kendall (13). Although lengthy empirical expressions were obtained, a constant value assigned to the effectiveness still seems adequate. : .004 (3.14) Considering Equation 3.11 once more, we see that the strongest influence on the wall to droplet heat flux is the void fraction. Hence, within the correlation's limitations, the wall to droplet heat transfer contribution will substantially increase inmagnitude, as the liquid fraction rises or the void fraction is lowered. 3.2 SPACER GRID EFFECTS Numerous causes of increases in total heat transfer at a spacer grid seem likely. Effective area reductions which constrict the flow, increase the flow velocity for a short distance and create an entrance effect at the spacer. This would tend to increase both the wall to vapor convection and wall to droplet conduction. Droplets inpacting the spacer form a saturated liquid boundary layer, which may desuperheat 44 the vapor, provide some fin cooling, splash drops onto the hot pipe wall downstream, and furnish the hot wall with an available radiation sink. The desuperheating effect isminor since vapor superheating isminimal. Droplet splashing and fin effects cannot be measured and quantified in this investigation but are not considered as major modes of heat transfer, The remaining mechanisms mentioned include increased velocity vapor convection, increased velocity droplet conduction, and wall to spacer radiation. (q/A)s = (q/A)v s + (q/A)D S + (q/A)R S (3.15) These individual contributions will now be examined ingreater detail. 3.2.1 Increased Flow Velocity Based on mass continuity, the increased mass flux and flow velocity, due to area reduction at the spacer, can be determined: *= ms s (3.16a) GA = GsA s (3.16b) Gs (3.16c) G(A ) As The mass flux at the spacer isthen related to the upstream and downstream mass flux simply by the area ratio. Also, since the flow density isassumed to remain constant, we have: V = V(A ) s As (3.17) 45 Due to the increased mass flux, decreased flow area, and also a changed hydraulic diameter, the vapor Reynolds Number must be modified at the spacer location. (Re) = G D X (3.18) Pv The hydraulic diameter, D s, is obtained by considering the actual flow area and the wetted perimeter; Ds = 4As P (3.19) These alterations are now substituted into Equations 3.4, 3.6, 3.11 and 3.13, yielding the governing relationships required for determining the vapor convection and droplet conduction heat transfer contributions at a spacer grid. (hDB)s = (.023) K (Re) s Ds .8 .4 (Pr)v (q/A)v s = (hDB)s (Twall Tvap) (3.20a) (3,20b) -.125 (Vl)s = (,0289) V s (Re)s (q/A)Ds = (1-a) Pf Hfg (V1) s (3.21a) (3,21b) 46 3.2.2 Wall to Spacer Radiation Droplets moving with the vapor flow collide with the spacer grid and become entrained on its surface. Newly formed droplets splash off the rear of the spacer as the liquid boundary layer builds up and periodically erupts. At all times, however, the spacer iswetted by the liquid and remains at the saturation temperature. Due to the large magnitude in temperature difference between the fuel rods and spacer grids during the CHF period and the low flooding rates typically encountered inreflood, a very significant portion of the overall heat transfer experienced at the spacer isexpected to be radiation induced. An important step in quantitatively analyzing the radiation contribution is to properly understand the geometry. Reviewing Figure 8 in Chapter II,the configuration presented is simply a thick cross bounded by a circular wall. Only the pipe wall section not incontact with the spacer, Aw , isable to radiate energy. For this gray body radiation, the governing net heat transfer equation developed by Hottel (14) is, qwf Aw 'wf 4 (Tw - Tf4) (3.22) where the subscripts w and f denote wall and liquid respectively, temperatures are measured indegrees Rankine, wf is the gray body effective view factor, and a is the Stefan-Boltzman constant, 0.1713 x 10 8 Btu ft hr R(3.23) 47 Assuming nonrefracting surfaces encompassing a nonabsorbing medium, 11 wf_ ~Ff Where w 1 1 + Af + (-)w- -1) (.4 isthe emissivity of the hot oxidized stainless steel wall, cf is the emissivity of the saturated liquid, and Fwf is the geometric viewfactor from the radiating wall to the spacer. To obtain Ff, Figure 8 is idealized by straightening the curved surface as illustrated inFigure 17. Due to symmetry, only one quarter of this configuration need be considered inorder to evaluate F. The following relation- ships may then be derived. A3F3 FWf = A1 F13 + A2 F23 = F3 wf= U 2(w) F 13 =/ ~~13 w F 12 + F13 = (3.25a) F13 1 1 FWf = V2 (1 - F12 ) (3.25b) (3.25c) (3.25d) The remaining view factor introduced, F12, may be calculated using a chart reprinted from Hottel inRohsenow (15), which gives the view factor for direct radiation between adjacent rectangles in perpendicular planes. This chart isreproduced inFigure 18. Since the radiation heat flux at the spacer must be based on the entire pipe area, the fraction of wall area seen by the spacer of 48 I I 2,L 3, W FIGURE 17: SPACER IDEALIZATION 49 I II I I III SI .I Z1) OD . -~~~ 0 ~ M.~~~~~~~~~~~~~, -- 00 4--'0I. 0~~~~. ~-0 : - ° · ° -- _ Ce:N _ __ ° ° ° oo °w ° - egO°N@O N. - - u) 0 ~ E 0' C~~~~~~~~~~~~~~~~~~~~~~~ L- 0 E-0.I :,U ''~~~~~~~~~~~~~~~~a Ij- o -4 C> ___ o 0 6 'A 6 6 ci U 0 14 6 0 In cl-i 0 N\ c c; *:I 0(30j ) - 6660O 0 - U') 0 0 I- LiiJ S- 50 the total area must be defined. aO Aw (3.26) Substituting this relationship into Equation 3.22 yields an expression for the radiation heat flux experienced at the spacer. 4 4 ~3wf a (Tw4 _ Ts4 ) (q/A)s = (3.27) In this investigation, the following values were appropriate, B = .801 (3.28a) Et .96 (3.28b) = .94 w F12 = 29 F12 (3.28c) Fwf wf = 1.0 (3.28e) = e (3.28d) Substituting into Equation 3.24 yields, T= '^f .92 (3.29) 51 CHAPTER IV: EXPERIMENTAL RESULTS AND COMPARISON TO THEORY 4.1 EXPERIMENTAL HEAT FLUX RESULTS Tests were conducted at a mass flux of 18, 720 lbm/hr-ft 2, which isequivalent to a flooding rate of 1 in/sec. The test section wall temperatures included 1000°F, 1100°F, 1200°F and 1300°F while the system pressure was kept at atmospheric. Numerous attempts were made to obtain data at both higher flooding rates and greater Reynolds Num- ber values (Re v > 5000). Unfortunately, all of these efforts were thwarted by an inlet quench problem. Further comments with regard to this will be made in Chapter V. Heat flux results obtained from the successful runs are plotted along with the corresponding theoretical curves in Figures 19, 20, 21 and 22. Several ortions of these curves first deserve identifica- tion. The shaded region at the start of each plot represents the range of anticipated entrance effects as predicted by cases 2 and 3 in Figure 15. This did indeed compare reasonably well with experimental values. Flat portions of the curves indicate steady-state values which were obtained both upstream and downstream of the spacer. The effect of the spacer itself is clearly recognizable by the sudden combination of step increase and step decrease in the predicted heat flux at the 101/2 inch and 12 inch marks respectively. These figures strongly infer that there isa very noticeable enhancement of heat transfer experienced at the spacer location. 52 0 N LJ > FC F- ==. 0 0o C o <C I - Li. C Z: g L L) C _ L z AS:- CD AL n~~ 0 (0 0 0 0 N (j .~q/n4) :_01 x V/0 0 53 \ LU IC) LL C) o 0 ,CD I-I z r- O CM Z: : ICL. C-, - 0 (Z; J4L/n4lg) 01 x V/) 54 ) of J C. 0I o. 0 () C C Lo z Z Wr- L.) L cn T- ._ LU 0 au_ : LL. 0 (lJ4 U) 0 (+J4ng *0 No £-0 X l - 0_O 55 O N n,' CI ILL C), o0 C) o~Z~~~CY emLU C h < OL LU FF 0 CD Z< z < J 4 tm CD C-M CM r, CD Ii OL cc ((; 4J'/n4l) e-o x V/ 56 Although the experimental data straddles the theoretical model, the magnitude of its scatter isat first alarming. The major cause of this behavior isdue to copper block temperature differences, creating an axial heat transfer not accounted for in the model. More specifically, the test section wall temperature iscontrolled to be at a constant level along its length. Heat flux spikes, however, vary significantly from block to block. This results indifferences incopper block temperatures which act as the driving potentials causing the heat flux spikes. Due to this temperature variance, heat is convected across the 1/8 inch gap from one block to another. This effect is felt most strongly at the spacer where the net heat flux is considerably greater than the fully-developed value. Accordingly, heat is transferred directly to the neighboring cooler blocks. Figures 19 and 20 exemplifying this situation, both indicate a negative net heat transfer immediately downstream of the spacer. What this all indicates is simply that the experimental heat fluxes at the spacer should be decreased enough inorder that the neighboring values be increased to at least the fully-developed value, such that the total energy transferred remains constant. Since the two blocks at the spacer are only one half as thick as the adjacent ones, the high experimental heat flux results obtained at the spacer should be decreased a distance equal to twice the increase inmagnitude of the lower values. The primary inpetus of this investigation is the specific determination of the spacer grid's effect. With this goal inmind, a 57 more detailed analysis of the effect will now be considered. 4.2 EFFECTIVE HEAT TRANSFER ADDITION AT SPACER A local heat transfer coefficient can be determined similar to the experimental heat transfer coefficient given in Equation 2.8. h = (q/A)x (4.1) (Twall - Tsat) When a flow reaches steady-state, this parameter also obtains a constant value given by h. The ratio hx to h yields a nondimensional heat transfer coefficient magnitude. hx (q/A) (4.2) When Figures 19 through 22 are replotted inthis fashion, they completely coincide except at the spacer. Figure 23 indicates that a three fold increase inthe local heat transfer coefficient isexperienced at this location. This effect iscaused by the radiation mode of heat transfer, which is heavily dependent on temperature and is localized at the spacer. The magnitude of increase inheat transfer caused by the spacer can also be obtained by integrating the heat flux curves. In this process, the valleys mmediately before and after the high spacer heat flux values are accounted for, such that the previously ignored problem of thermal interaction between adjacent blocks isvirtually eliminated. These integrated values are plotted inFigure 24 along 58 CD I-- LU Z L)_ N C##j~C r{,?) LU Ln I- C oD= ,cS LU CD uI- LL ZZi Z 0~4 0 ci cC (z C Ldo U--L t Cq/ It3 a /"4 u~r 59 no 0 - V- . M LL c L) 0o0J .. iJV F cJ LU - 0 I 0 i CC LI LJ CD CL a)~~V I I I (0 I C3j (Jt/n~Ei) _0 x s o0 I 0 60 with a theoretical curve obtained from the model presented inChapter III. Although this model underestimates the experimental findings, the correlation between the two ismuch better than indicated earlier by the heat flux curves. As the wall temperature increases, the model seems to predict a greater percentage of the experimentally determined spacer heat transfer. This trend isdirectly caused by the increasing importance of wall to spacer radiation at higher temperatures, which iseasily accounted for. To make this concept clearer, the total energy transferred at the spacer, based on the theoretical model, is broken down between the three heat transfer modes by percentage and plotted inFigure 25. At lower temperatures, the radiation effect is not much greater than the droplet contribution; however, radiation becomes the primary mode of heat transfer beyond 1400°F. Several reasons for the model's underpredictions seem plausible. A disturbance caused by the flow's constriction at the spacer may induce an entrance effect at the spacer and slightly downstream of it. This, however, would not effect the radiation contribution, and therefore isconsistent with the trend illustrated in Figure 24. A second consideration isthe exceptionally high temperature of copper blocks located at the spacer. Not only is heat transferred axially, but an increased radial heat loss isexperienced which isgreater than that measured during heat loss tests. In summary, we see that there are reasons why the actual heat transfer at the spacer isgreater than what the model predicts but also less than what experimental results may have us believe. 61 0 0 to LU C-) IL: * ClI- LU woU- V) OD..LUJ Cj Z CD~ 0o 0 (0 (%) (%)S * l 0 N 39VLN333 3 39VIN3383d JO 0 LU- 62 CHAPTER V: CONCLUSIONS AND RECOMMENDATIONS 5.1 CONCLUSIONS The goal of this investigation was to determine the extent of spacer induced heat transfer enhancement during a post critical heat flux situation. In this vein both experimental and theoretical programs were designed to quantitatively analyze the magnitude of this effect. Wall temperature was varied in increments of 100 degrees between 1000°F and 1300°F. The mass flux equaled 18,720 lbm/hr-ft 2 , which is equivalent to a 1 in/sec flooding rate, The "Fixed Vapor Fraction Model" predicted entrance and steadystate heat transfer levels consistent with experimental values. Where discrepancies at the spacer due to experimental scatter occurred, an integration scheme was applied which accounted for a heat transfer interaction not included in the theoretical model. Results indicate that for the flows considered, an increase of at least three times the net heat transfered at the spacer may be expected. This supplemental energy from the hot wall at the spacer is primarily due to: (1) Higher vapor velocities which increase the vapor convection and droplet conduction. (2) Wall to saturated liquid (entrained on the spacer) radiation. The first effect is independent of wall temperature and depends simply on the steady-state flow. The magnitude at the spacer will be a constant multiple (with respect to temperature) of the steady-state value. 63 The second effect, radiation, isonly dependent on wall temperature and provides extra heat transfer localized at the spacer. When the wall temperature exceeds 1400°F, the radiation effect dominated in the low Reynolds Number (Re v = 4800), low flooding rate (1in/sec) situation. One final consideration concerns an entrance effect at the spacer. Similar to the initial portion of the test section, a rise in heat transfer may result from unsteady flow behavior. Assuming this to be the case, the theoretical model incorporated in this analysis will underpredict the vapor convection and droplet conduction. The radiation contribution, however, will not be affected since it is independent of the vapor flow. 5.2 RECOMMENDATIONS Several suggestions seem inorder with regard to future spacer grid analysis; inparticular, construction of the experimental apparatus. In this study, thin copper heating blocks were used at the spacer in hopes of obtaining a more sensitive measurement. Since the cartridge heaters were inserted radially, a large block diameter was required. This tended to greatly aggravate the inter-block heat trans- fer problem, which was the primary cause of data scatter. Inthe future, one heating block should be employed at the spacer with a thickness of approximately two inches and all block diameters throughout the test section should be minimized. Inaddition, thermocouples could be mounted on the copper blocks inorder to determine any remaining thermal 64 interaction between blocks and to more accurately account for individual block heat losses to the environment. A second recommendation pertains to the test section inlet. Liquid leaving the electric preheater was able to wet the unheated pipe wall previous to the test section. Upon entering the heated section, the first block received full responsibility of maintaining a vapor blanket on the pipe wall. This tended to be an unstable situation since liquid constantly rewetted the start of the test section, violently pulling the wall tempeature out of the post critical heat flux region before the controller mechanism could have an effect. During downflow studies, the flow can be funneled into the test section, mechanically providing an artificial dry starting length as the flow isexpanding. This cannot be applied to the upflow situation since the gravitational force would tend to form a pool of water between the funnel and test section wall. What isrequired isa totally different approach, one which can insure that the post CHF state of the test section inlet flow ismaintained. 65 REFERENCES 1. Hsu, Y.Y. and Sullivan, H., "Thermal-Hydraulic Aspects of PWR Safety Research", Thermal and Hydraulic Aspects of Nuclear Reactor Safety, Vol. 1, 1977. 2. Bjrnard, T.A., "Blowdown Heat Transfer in a Pressurized Water Reactor", PH.D. Thesis, Massachusetts Institute of Technology, August 1977. 3. Smith, T.A., "Heat Transfer and Carry Over of Low Pressure Water in a Heated Vertical Tube", Masters Thesis, Massachusetts Institute of Technology, January 1976. 4. Robershotte, P., "Downflow Post Critical Heat Flux Heat Transfer of Low Pressure Water", Masters Thesis, Massachusetts Institute of Technology, July 1977. 5. Kaufman, J.M., "Post Critical Heat Flux Heat Transfer to Water in a Vertical Tube", Masters Thesis, Massachusetts Institute of Technology, September 1976. 6. Singh, B., Current Research at the Mechanical Engineering Heat Transfer Lab, Massachusetts Institute of Technology. 7. Cheung, Y., Current Research at the Mechanical Engineering Heat Transfer Lab, Massachusetts Institute of Technology. 8. Gonzalez-Rivas, J.I., "Carry-Over Predictions from the Upper Plenum of a Pressurized Water Reactor Based on a First Order Void Fraction Analysis", Masters Thesis, Massachusetts Institute of Technology, May 1978. 9. Dittus, F.W. and Boelter, L.M.K., University of California Pub. Eng. 3, 443, 1930. 10, 11. ESDU (1968), "Forced Convective Heat Transfer in Circular Tubes", Part III: Further Data for Turbulent Flow. Item No. 68007, (251-259 Regent St., London WR 7AD). Ganid, E.N. and Rohsenow, W.M., "Post Critical Heat Flux Heat Transfer", MIT Report No. 82672-97, June 1976. 66 12. Liu, B.Y.H. and Ilori, T.A., "Inertial Deposition of Aerosol Particles in Turbulent Pipe Flow". Presented at the ASME Symposium on Flow Studies in Air and Water Pollution. Atlanta Georgia, 20-22 June 1973. 13. Kendall, G., "Heat Transfer to Impacting Drops and Post Critical Heat Flux Dispersed Flow", Ph.D. Thesis, Massachusetts Institute of Technology, March 1977. 14. Hottel, H.C. "Radiation", Chapter IV of Heat Transmission, by W.H. McAdams, McGraw-Hill, 1954. 15. Rohsenow, W.M. and Choi, H.Y., Heat Mass and Momentum Transfer, Prentice-Hall Inc., 1961. 67 APPENDIX A: TEMPERATURE CONTROLLER Z: I--m FI-- I! v-i C.) LU -J -J 0 t I 0 C, LU 0 0 a-m: LU c I I-j 4- CD I--, L N 4- ! s- 68 APPENDIX B EXPERIMENTAL DATA RUN Twa 1I 1 2a 2b 3a 3b 4 1000°F 1100°F 1100°F 1200°F 1200°F 1300°F (Rev)inlet 4300 4800 4950 4850 5000 4725 Flow = 18,720 lbm/hr-ft2, PRESS = 0 psig 69 I C) ,o 4_ I- 4 XH F s O' co~ C\J r- a; r-.l ms cIi£4 I I-- - --I qI r O -- In; L L WA CJ L 00 U) ' . C '~: (%J.& U- co t oo ,-Xz / f- v 4-- il O0 O.-t Cx 4-) I M CD. S - C a tor CD - C00rCD - C cr _ 4 _0 O M 0 -- 0 r. U) a, I C.n CD r>' tn I+_- I r-_ r- - co _ ko Ln Un1-q*'d ) _ I- xws _W r C e C LA n U 4.-- um m ao w cm _ " N M 00 I00 -. M -. CM * *-r-% c*n *tC ON -C *~~~~~~~~~~~~~~~ * .*Q . X.~. 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I_ P. o " o o D C~ oo M mrUI_ n Ln 00o 0 ,Ln) II -J C% .r D LO M 3 _ w -9 W- 0 C C) 3a .- co oo CO00o , # 0 co C> ,_ - PC/i. O L L O ) uL O O LOL zLi~ 0 C', P-4 0 )ij., o_. O) L r_:~ O U) O _~ _c 4U;Q. _ _ C- 71 _ C" Ct, C-M 0 j - -) I - X LLJ S 0 lA m I-I- Cl W N ) N _ 1 Mt c_ C4 Le m- X LUJ m , _0 Oh I m CO CD < _j l _ _ M r-r- W V LO _A C _ 0 r 'V% wC kD _i CD JC _~v _ .- C(/) x V-.) 4-) 44s cr CD co C% 3 I- _~ ~~4-) s m % 0 CWj 4 O 0000 *) *) ) 000000 aea CoN;r -- _-% 4-) Xl W I Z1 I- M S U C9^ O M 4-) r- M) -0 - 1 n to M W) N 0 t N M N t ) C\J r- 4-) %... CT _ ow CD0co 4-) ov O (n I LL _ = LOA0)OeCr t_ N oK gI N _- Ir W t O M Wr- ct -~ ---LO CJ L LA M a LO - D Ir-) rI9O r d o U0 0 C" CD c on a I- 11~~~~~~~~~~~ = II M !- I- AS 3 I-- O c 0 CO I - C LOr- DCN r- 11V- LO r a U- rCL *c 4-)' *c .l .l to *c .d urRd* * r- C; 0 0 43l.. LA II 4-) v4) U- II ICK WLJ4-) :34-) 0 Lu o MCO W cn ,D LAL: WkOUDr-OD ct Rd"' N NtD 1 ,- - 3 - I= A r-. LU 4-) N Cl 44 _ 4u 0 C m 00 D O NOLO D ¢ No 3 v 4.- qI- 0) N i- .-I " o r O I¢ ,.- C- 0 INN ' D I.U) ,- rr--, CD:) cv ,C O LA S 4-) CM v U- - -10 LU CD W .Cm -i J) _ O OOOLALAOOOOO CO O LO O CD O O 0) to to LO r_ CO 4.-J LU CMj.- CC 4 -i O Mt Mr¢ rll~ -_ CD A O L L L oO LO L o o L Qn > 3 co I- 3 If :r3 -J C-o -j LL. D .1 LA. z IC.) i o LO n o u I o o · unC C-lI. or' _" _" _" _ C~ 0C N- o 72 APPENDIX C THEORETICAL ANALYSIS COMPUTER PROGRAM 73 : I=3I _J m - I-LL a' w 4 I.-J b_ ZW. 4 ao O.7 Li x w. a z 74 rv 'p :> -j .J4-i ula. 'hi a; a) W. -4 'P - * 0 U, NI U, -J a : O0 LiUAu 4 u0 " -4 o - Li 00 IIa-z. 4 -J ..4 0 0 U) '- I--0CD. C0 ra,u0Q. IL-/ 0 4Zm Z- O z1-- W 0 0I L) 'U k,n LA P.-UD In -(N CD 000 0I C 0S 0 Sf * S. U Li _ 1 1 I z~~~~~~ 0 L) IU 0. II II .. -J LA. W. Ill'-' Y LZ Ca 1-4 LJ Z 4C a:w I-Li L) ir4 ll.- 0. 0 - II o-. P0 s04I ro 11 N -,. o · ,*SllO 40 11 o Cy ,444 * 0< 0'* Oit II 11 .J : = II . 'I Z II it 0 4c <t t4 u aO:I. ai 0 0LU 0 I-4 0V '- W Ix v C n) 4 7 - * -4 I02z 2 O)W Wi co C zo u 1 C Z Z O 74 _ · - --- I * _-- _ II II I I * * · · · oLn ·o * * N - 1' 1I * . I I S _ S zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz w i i i W WWWw WW -a -_ - - -_ at I I IIi IIU S e N N S 2S i S _ · o - - o o U N ·· · v 4 ^ ' Wi S LJ S S S S S S S S · _o -NP,_ -- II aIIaIII III ,l I,aI II U IIt S ZS · . AR_ 11 II II I I IaI S S S S S JIAWWLLJLLJLJW WW w S 75 2 gg 4 a w V- Li. *LI z a: 0. 'C Ia CX Jr~~~~~& z U.: 4I-L31. t .i o . . ILL WI A .~ nI 'i ('M0 ,.o o a. -J - z I-- Im C 3LA 0 4 IX 0 * :'-4 Z * -40 w o0 a:- - _ L..J *A .J U 11 0 0.4<3 Li Z-- a: o * X - * It ,- 4 a: ,-. MO atI' vwNo -F _N. Fv._ =,. l, a'-'4 , Q 0X 2W S.- I.Z) WO n, i. Z_- o uuu¢(. ,. 9- * r O'¢C o10 ,. Li 0 I0O I- Z 4 -0 om 1I LA .' -t O- oe 0 2 .0 ~.$-· I-.0 :' .0 L& 0 o 0 > O uuu 0. Z J uuu en ca, . 4 Li.- m 74b .*-C . 0' .e-L r*l. 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O 11- IO IA.C X0 Z - 0 a:*U) 3 1- 4 o I- 0 4c n:)O > I-- D &JI-0 . - I.- XX: J~ nL ZZOZ N '- Z II IIt I w Z -4 I-- .- I-- ~ X0. -- o Z-F Z O a -I--I-X Xo c uuu Ouu o 3 W- LUC - 0 0 r- 0 F z 4A w 0 a O a LUW X 82 APPENDIX D THEORETICAL RESULTS RUN Twall 1 2 3 4 1OO0° F 1100°F 1200°F 1300°F (Rev)inlet FLOW = 18,720 lbm/hr-ft2 , PRESS = 0 psig 4400 4950 4940 4725 *0AW C, 83 r 4: C'va. :t P. 0 r ::1 P II * 0 M 0 C 0N C, *L (N t N ( P- 4 V I ' fZ N C\( . C CN N \1ol ' - 0, 0 0 M N 1) J4-0 0 a C. C 0 * i - C 0 * * - (, UrLc-q- M. Z C4 3 43 ' U LI L u . ' .' ("N C\ N (N ' N N (NJ rv (N rNJ c't. - (N C 0. C, '. cv C 4 (N(N C' 0 C. * 0 (N. C. 0 0 (? : ; (', C\ r.. -' H 0~ I:$E- ,P, LI. 4:- 0 CO 2s H PC LI e * r fr-0 r o 1. qI * 0 0 * e 0 0 . ' 0r' 0 oo 0- . - Wr, 1- E- [-~ 4 . 0 * : M :- %C T cc . i c cc 0 0 LO _ M M C - - o O Uo tJ, P", 0 - 0 rQ M 0 rI - r- * r tf- c 0 N e a r' a "O N - N 0 0 0 * r- r- r-> 0* r- L r,I,- c" c 1-I, C c C (N c C"-,q 0. * * M %c , . 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', C C, C L,>0 Li' 0' If a a * * 0 O') C > 7 - 7 - ( ( (4 (CN (N (, (N (N 91 APPENDIX E: WATER AND VAPOR PROPERTIES TABLE 2: SYSTEM PROPERTIES WATER L 60 (CP)L = 1 1bi/ft3 Btu/lbm°F STEAM Pv = .04559 - .00003958 x Tvap Kv = UV= (Cp)V 00747 + 0000551 x Tva p .01747 + .0000551 x Tvap .48 Btu/lbm°F Prv = (CP)V x V Kv Ibm/ft3 Btu/Hr,ft 1bm/hr-ft F