1、NASA TECHNICAL NOTE NASA TN D - Cl / EXPERIMENTAL LOCAL HEAT-TRANSFER AND AVERAGE FRICTION DATA FOR HYDROGEN AND HELIUM FLOWING IN A TUBE AT SURFACE TEMPERATURES UP TO 5600 R by Muyndrd F. Tdylor Lewis Resedrch Center Cleveland, Ohio -2280 - NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON,
2、0. C. APRIL 1964 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECH LIBRARY KAFB, NM I lllllllllll11111 lllll lllll lllll1lll11111 Ill1 EXPERIMENTAL LOCAL HEAT-TRANSFER AND AVERAGE FRICTION DATA FOR HYDROGEN AND HELIUM FLOWING IN A TUBE AT SURFACE
3、TEMPERATURES UP TO 5600 R By Maynard F. Taylor Lewis Research Center Cleveland, Ohio NATIONAL AERONAUTICS AND SPACE ADMINISTRATION For sale by the Office of Technical Services, Department of Commerce, Washington, D.C. 20230 - Price $1.00 Provided by IHSNot for ResaleNo reproduction or networking per
4、mitted without license from IHS-,-,-EXPERIMENTAL LOCAL HEAT-TRANSFER AND AVERAGE FRICTION DATA FOR HYDROGEN AND HELIUM FLOWING IN A TUBE AT SURFACE TEMPERA-S UP TO 5600 R by Maynard F. Taylor Lewis Research Center SUMMARY Local values of heat-transfer coefficients and average friction coeffi- cients
5、 were measured experimentally for helium and hydrogen gases flowing through an electrically heated tungsten tube with a length-to-diameter ratio of 77 for the following range of conditions: local surface temperatures up to 5600 R, local Reynolds number from 7600 to 39,500, local ratios of surface to
6、 bulk gas temperature up to 5.6, and heat flux up to 1,700,000 Btu per hour per square foot. A comparison of local heat-transfer coefficients for helium and hydrogen gases is made for several types of wall temperature distributions in order to determine whether data can be correlated by a Dittus-Boe
7、lter type equation. Wall temperature distributions for hydrogen are compared with one for helium with the result that any dissociation of hydrogen at the tube wall for wall temperatures up to 5200 R has less effect on the wall temperature distri- bution than does the ratio of surface to bulk gas tem
8、perature. INTRODUCTION Nuclear reactors, such as those proposed for use in rockets using hydro- gen as a propellant, involve heat transfer with large variations in the thermo- dynamic and transport properties of the gas. dissociation of the fluid or to large differences between surface and bulk gas
9、temperatures or both. The ratio of surface to gas temperature can be as large as 25 at the inlet of a nuclear reactor if the surface temperature is 5000 R and the inlet gas temperature is 200 R. occur in the fluid adjacent to the fueled surface through most of the reactor and will occur in the bulk
10、hydrogen at the reactor outlet. The effect of the large variations in the transport properties on the heat-transfer characteris- These variations can be due to Some degree of dissociation will Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-tics of h
11、ydrogen is very important in the design considerations for nuclear- rocket powered space vehicles. Considerable experimental data showing the effect of surface to fluid tem- perature ratio on the heat-transfer coefficient for air are presented in refer- ence 1. A number of other investigations exten
12、ding over the range of wall tem- perature, pressure, and ratio of surface to bulk temperature that include hel- ium, hydrogen, and nitrogen have been made and are presented in references 2 to 6. The conditions for which data were obtained in references 1 to 6 and in the present investigation are sho
13、wn in table I. The present investigation TABU3 I. - EXPERTMENTAL CONDITIONS FOR REEEXENCES I 6 Present inves ti - - Tub e Length-tc dime t e r ratio 30 to 12C 389 50 and 92 20.9 to 42.6 250 23.2 12 7 77 Maximum surface to bulk gas tem- peraturc ratio 3.5 1.39 3.9 11.09 4 *5 4.52 2.08 5.6 hximur lo c
14、 a1 surf acc temper . xture, OR - 5040 5900 - 2300 4600 1915 5600 daximm iverage surface temper- xture, OR 3050 3900 4533 2240 - - - 4749 Inlet pres sure, lb sq in. ab s Heat - transfer fluid Air Helium Helium Ielium and hydrogen Ielium and hydrogen Ielium and hydrogen Nitrogen Eelium and hydrogen .
15、 Types of heat - transfer coef f i- .cients measured Average Local an( averagt Local an( averagt Local Local Aver age Local Local I gation was intended (1) to extend the range of surface to bulk temperature ratio at high surface temperatures and (2) to determine the effect of dissociation at the sur
16、face on the wall temperature distribution. The experiment was performed by flowing helium and hydrogen through an electrically heated tube. A ratio of local surface to bulk temperature of 5.6 and wall temperatures as high as 2 Provided by IHSNot for ResaleNo reproduction or networking permitted with
17、out license from IHS-,-,-56000 R were attained at inlet pressures varying from 40 to 100 pounds per square inch absolute. EXPERlMENTAL APPARATUS Arrangement A schematic diagram of the arrangement of the test apparatus used in this Either helium or hydrogen from a pressur- investigation is shown in f
18、igure 1. Molybdenum radiation shield ,- Molybdenum radiation /-($in. diam.) 12 0 Tungsten radiation shield (I in. diam.) Section A-A I the middle and outer shields were made of 0.010-inch-thick molyb- denum 1- and 1- inches in diameter, respectively. Boron nitride spacers were used to hold the shiel
19、ds in position. The mixing tanks and the test-section assembly were housed in a vacuum-tight steel containment tank evacuated to about 25 microns of mercury during test runs. apparatus with the containment tank removed. 1 1 4 2 Figure 2 shows the experimental 3 Provided by IHSNot for ResaleNo reprod
20、uction or networking permitted without license from IHS-,-,-Electric power was supplied to the test section through water-cooled cop- per tubing from a 208-volt 60-cycle supply line through a 100-kilovolt-ampere transformer controlled by a saturable core reactor. The saturable core reactor permitted
21、 voltage regulation from approximately 3 to 25 volts. mean-square electronic voltmeter was used directly to read the potential across the test section. Current was read on an ammeter used with an 800 to 1 step down current transformer and checked with a calibrated shunt. A true root- Test Sections T
22、he test section used in this investigation was made of tungsten. Since a tungsten tube was not available commercially, .it was necessary to fabricate it by disintegrating a hole in a tungsten rod. 0.116f0.002-inch inside diameter with a 15- to 20-microinch root mean square finish or better and was c
23、oncentric with the outside diameter to within a total indicator reading of 0.006 inch. The outside diameter of the tube was then ground to obtain a wall thickness of 0.0625f0.002 inch with a surface finish of 32 microinch root mean square or better. The tungsten tube was joined to water-cooled flang
24、es made of nickel and oxygen-free high conductivity copper with a furnace braze of 82 percent gold and 18 percent nickel at about 1830 F; this temperature is well below the recrystallization temperature of tungsten. The test section was cycled between about 1000 and 5000O R approximately 20 times in
25、 the course of the experiment, which totaled about 25 hours of opera- tion at temperatures of 4000 R or higher, and it did not fail. tion had an entrance length of 14 diameters before the heated section. symbols are defined in appendix A. ) The hole was lapped to The test sec- (All Instrument at ion
26、 The outside wall temperatures near the entrance and the exit of the test se et ion were measured with 2 4-gage platinum- plat inum- 13- percent - rhodium the rmo- couples spot-welded along the length as shown in figure 3. The temperature of Station 1 Pressure drop length, 91- Boron nitride spacer 7
27、 x Thermocouples o Voltage taps Figure 3. - Schematic diagram of test-section assembly showing thermocouple, voltage tap, and pressure tap locations. (Ail dimensions in inches.) 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-most of the test secti
28、on was measured with a small-target disappearing- filament, optical pyrometer. More information on the technique of temperature measurement used in this investigation can be found in appendix B. The temperature of the gas was measured at the entrance and the exit of the t e st se ct ion with platinu
29、m- platinum- rhodium thermocouple s located down- stream of the baffles in the two mixing tanks. The radiation shields were also instrumented with platinum-platinum- rhodium thermocouples as shown in figure 3. Static pressure taps were located in the entrance and the exit flanges of the test section
30、 and were read on 0- to 100-pounds-per-square-inch pressure gages having a full-scale accuracy of 1/2 percent. Seven tantalum voltage taps were spot-welded along the test sec- tion to measure voltage drop as a function of distance fromthe entrance; how- ever? only the voltage taps located at the ent
31、rance and the exit remained on the test section when it was heated. This arrangement permitted measurement only of the total voltage drop across the test section. METHOD OF CALCULATION Hydrogen Properties The variation of the transport and thermodynamic properties important in .36 .32 .28 + x .=- .2
32、4 m i? .- u .2J !z U A c c - m o .16 c 0 U .- c e - .12 P) - P -.i 3Ooo - 3 l nperaturi, T, 61 (a) Mole fraction of atomic hydrogen (refs. 8 and 9). Figure 4. - Variation of hydrogen properties with tem- perature at 1 atmosphere. calcdatibns of heat-transfer and fric- tion coefficients is shown in f
33、igure 4 as a function of temperature for a pressure of 1 atmosphere (data from refs. 7 to 12). The effect of pressure on the properties of hydrogen was not taken into considera- tion since the pressure was near 1 atmo- sphere at points in the test section where the temperature was high enough for th
34、e pressure effect on dissociation to be appreciable. Figure 4(a) shows the mole fraction of atomic hydrogen x1 present at any temperature and was taken from references 8 and 9. The thermal conduc- tivity k and the absolute viscosity p from references 8 to 12 for equilibrium dissociating hydrogen is
35、shown in figures 4(b) and (e). Chemically frozen thermal conductivity, which does not include the chemical reaction term, was taken from reference 9 and is also shown in figure 4(b). The experimental thermal conduc- tivity data shown in figure 4(b) are from reference 7 and are the only data at high
36、temperatures available at present. The values of thermal conductivity used in this investigation are represented by the 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-solid line that was calculated by use of the viscosity and thermal conductivity
37、of hydrogen atoms and molecules from table I11 of reference 11 and the heat of 4.5 4.0 0, - Used in this investigation (refs. 11 and 12) 5 3.5 = 3.0 _- L r - z 2 2.5 s M .- g 2.0 0 3 U V s 1.5 1.0 I- .5 n - E 0) r (b) Thermal conductivity. 30 EB - Used in this investhation H (refs. 8 and 9) - +ti 50
38、0 loo0 1500 2000 2500 UNW) 3500 4000 4500 5 (d) Specific heat at constant pressure. oze 50C mt Used in I this I I investhation I I I I (refs. 11 and 12) - Ref. 10 - .12 - Ref. 9 .lo .08 .p 5 .06 s g .04 r c .- U VI 5 .02 0 .8 (c) Absolute viscosity 6ooo 500 1000 1500 2000 2500 3000 3500 4000 4500 50
39、00 5500 6ooo Temperature, T, OR (e) Ratio of specific heats. Figure 4. - Concluded. Variation of hydrogen properties with temperature at 1 atmosphere. dissociation from table XXX of reference 12. The values of specific heat for equilibrium dissociating hydrogen at constant pressure cp shown in figur
40、e 4(d) were taken from references 8 and 9 and are in complete agreement. The chemically frozen specific heat, which does not include the chemical reaction term, was taken from reference 9. The ratio of specific heats y is taken from references 8 and 9 and is shown in figure 4(e). very good agreement
41、 at temperatures below 3700 R, a range that more than covers the bulk gas temperatures in this investigation. was taken to be 766.4 foot-pound per pound mass OR. The two references are in The gas constant R Helium Properties The transport properties, thermal conductivity k and absolute viscosity for
42、 helium used in calculations of this investigation are shown in figure 5 p 6 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-/ 0 I2 - - - - - - - L - - -4 -40 36 32 c ._ E 3. b -28 5 -24 c 5- v) OI c -20 2 - 0 x 5 c .- -16 5 .- v1 a -E 12 8 m a / 1m3
43、 c / I! Thermal cor II Absolute vis IIIII k ictivity Reference 0 7 11 0 CI 5 / I C / 0 0 / / I .05 , / 0 500 Temperature, T, OR Figure 5. - Variation of thermal conductivity and absolute viscosity of helium with temperature. o Ref. 13 Ref. 14 ated I 11 OR Extra _ Y 4 -0 58i 501 E 54 I 500 d 0 / / 1
44、1 Figure 6. - Variation of thermal conductivity and electrical resistivity of tungsten with temperature. 7 I - . . . . . . - .- . . . . . . . . Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-as a function of temperature. reference 11 are shown along
45、 with experimental points from reference 7. The lack of agreement between experiment and theory even for a monatomic gas indi- cates the great need for more experimental measurements of thermal conductivity of gases at high temperatures. The specific heat at constant pressure c P was taken to be con
46、stant at 1.248 Btu/(lb)(OR), the ratio of specific heats y to be 1.667, and the gas constant The theoretical values taken from table I11 of R to be 386 foot-pounds per pound mass OR. , / Physical Properties of Tungsten and Molybdenum Figure 6 shows both the thermal conductivity k and the electrical
47、resis- tivity pe of tungsten plotted as a function of temperature. The experimental thermal conductivity data for the temperature range of 2000 to 3f33Oo R were taken from reference 13 and extrapolated, as shown by the dashed line, to cover the range of this investigation. references 13 and 14, whic
48、h are in agreement to within 3 percent. reference 14 and is shown in figure 7 as a function of temperature. The spec- tral emissivity at a wavelength of 0.650 micron was taken from reference 15 and is also shown in figure 7. sivity is given in appendix B. The electrical resistivity was taken from The normal total emissivity of both tungsten and molybdenum was taken from A discussion of the use of the spectral emis- -_ IJ / / 0 Temperature, T, OR I f x) Figure 7. - Variation of emissivity of tungsten and molybdenum with temperature. 8 Provided by IHSNot for ResaleNo reproducti
