1. Trang chủ
  2. » Kỹ Thuật - Công Nghệ

A HEAT TRANSFER TEXTBOOK - THIRD EDITION Episode 3 Part 2 potx

25 547 0

Đang tải... (xem toàn văn)

Tài liệu hạn chế xem trước, để xem đầy đủ mời bạn chọn Tải xuống

THÔNG TIN TÀI LIỆU

Thông tin cơ bản

Định dạng
Số trang 25
Dung lượng 211 KB

Nội dung

514 Chapter 9: Heat transfer in boiling and other phase-change configurations9.9 Water at 100 atm boils on a nickel heater whose temperature is 6◦ C above Tsat.. 516 Chapter 9: Heat trans

Trang 1

514 Chapter 9: Heat transfer in boiling and other phase-change configurations

9.9 Water at 100 atm boils on a nickel heater whose temperature

is 6◦ C above Tsat Find h and q.

9.10 Water boils on a large flat plate at 1 atm Calculate qmaxif the

plate is operated on the surface of the moon (at16of gearth−normal).What would qmax be in a space vehicle experiencing 10−4 of

gearth −normal?

9.11 Water boils on a 0.002 m diameter horizontal copper wire Plot,

to scale, as much of the boiling curve on log q vs log ∆T

coor-dinates as you can The system is at 1 atm

9.12 Redo Problem 9.11 for a 0.03 m diameter sphere in water at

10 atm

9.13 Verify eqn (9.17)

9.14 Make a sketch of the q vs (T w −Tsat) relation for a pool boiling

process, and invent a graphical method for locating the points

where h is maximum and minimum.

9.15 A 2 mm diameter jet of methanol is directed normal to the

center of a 1.5 cm diameter disk heater at 1 m/s How many

watts can safely be supplied by the heater?

9.16 Saturated water at 1 atm boils on a ½ cm diameter platinum

rod Estimate the temperature of the rod at burnout

9.17 Plot (T w − Tsat) and the quality x as a function of position x

for the conditions in Example9.9 Set x = 0 where x = 0 and

end the plot where the quality reaches 80%

9.18 Plot (T w − Tsat) and the quality x as a function of position in

an 8 cm I.D pipe if 0.3 kg/s of water at 100 ◦C passes through

it and q w = 200, 000 W/m2

9.19 Use dimensional analysis to verify the form of eqn (9.8)

9.20 Compare the peak heat flux calculated from the data given in

Problem 5.6with the appropriate prediction [The prediction

is within 11%.]

Trang 2

Problems 515

9.21 The Kandlikar correlation, eqn (9.50a), can be adapted

sub-cooled flow boiling, with x = 0 (region B in Fig.9.19) Noting

that q w = hfb(T w − Tsat), show that

q w =1058 hloF (Gh fg ) −0.7 (T w − Tsat )1/0.3

in subcooled flow boiling [9.47]

9.22 Verify eqn (9.53) by repeating the analysis following eqn (8.47)

but using the b.c (∂u/∂y) y =δ = τ δ µ in place of (∂u/∂y) y =δ

= 0 Verify the statement involving eqn (9.54)

9.23 A cool-water-carrying pipe 7 cm in outside diameter has an

outside temperature of 40C Saturated steam at 80C flows

across it Plothcondensationover the range of Reynolds numbers

0  Re D  106 Do you get the value at ReD = 0 that you would

anticipate from Chapter8?

9.24 (a) Suppose that you have pits of roughly 0.002 mm

diame-ter in a metallic headiame-ter surface At about what temperature

might you expect water to boil on that surface if the pressure

is 20 atm (b) Measurements have shown that water at

atmo-spheric pressure can be superheated about 200C above its

normal boiling point Roughly how large an embryonic bubble

would be needed to trigger nucleation in water in such a state

9.25 Obtain the dimensionless functional form of the pool boiling

qmax equation and the qmaxequation for flow boiling on

exter-nal surfaces, using dimensioexter-nal aexter-nalysis

9.26 A chemist produces a nondegradable additive that will increase

σ by a factor of ten for water at 1 atm By what factor will the

additive improve qmax during pool boiling on (a) infinite flat

plates and (b) small horizontal cylinders? By what factor will

it improve burnout in the flow of jet on a disk?

9.27 Steam at 1 atm is blown at 26 m/s over a 1 cm O.D cylinder at

90◦ C What is h? Can you suggest any physical process within

the cylinder that could sustain this temperature in this flow?

9.28 The water shown in Fig 9.17 is at 1 atm, and the Nichrome

heater can be approximated as nickel What is T w − Tsat?

Trang 3

516 Chapter 9: Heat transfer in boiling and other phase-change configurations

9.29 For film boiling on horizontal cylinders, eqn (9.6) is modified

9.30 Water at 47C flows through a 13 cm diameter thin-walled tube

at 8 m/s Saturated water vapor, at 1 atm, flows across the tube

at 50 m/s Evaluate Ttube, U , and q.

9.31 A 1 cm diameter thin-walled tube carries liquid metal through

saturated water at 1 atm The throughflow of metal is creased until burnout occurs At that point the metal tem-perature is 250◦ C and h inside the tube is 9600 W/m2K What

in-is the wall temperature at burnout?

9.32 At about what velocity of liquid metal flow does burnout occur

in Problem9.31if the metal is mercury?

9.33 Explain, in physical terms, why eqns (9.23) and (9.24), instead

of differing by a factor of two, are almost equal How do these

equations change when H is large?

9.34 A liquid enters the heated section of a pipe at a location z = 0

with a specific enthalpy ˆhin If the wall heat flux is q wand the

pipe diameter is D, show that the enthalpy a distance z = L

Since the quality may be defined as x ≡ (ˆ h − ˆ h f ,sat ) h fg, show

that for constant q w

x = hinˆ − ˆ h f ,sat

h fg + 4q w L

GD

9.35 Consider again the x-ray monochrometer described in Problem

7.44 Suppose now that the mass flow rate of liquid nitrogen

is 0.023 kg/s, that the nitrogen is saturated at 110 K when

it enters the heated section, and that the passage horizontal.Estimate the quality and the wall temperature at end of the

Trang 4

References 517

heated section if F = 4.70 for nitrogen in eqns (9.50) As

before, assume the silicon to conduct well enough that the heat

load is distributed uniformly over the surface of the passage

9.36 Use data from AppendixAand Sect.9.1to calculate the merit

number, M, for the following potential heat-pipe working

flu-ids over the range 200 K to 600 K in 100 K increments: water,

mercury, methanol, ammonia, and HCFC-22 If data are

un-available for a fluid in some range, indicate so What fluids are

best suited for particular temperature ranges?

References

[9.1] S Nukiyama The maximum and minimum values of the heat q

transmitted from metal to boiling water under atmospheric

pres-sure J Jap Soc Mech Eng., 37:367–374, 1934 (transl.: Int J Heat

Mass Transfer, vol 9, 1966, pp 1419–1433).

[9.2] T B Drew and C Mueller Boiling Trans AIChE, 33:449, 1937.

[9.3] International Association for the Properties of Water and Steam

Release on surface tension of ordinary water substance Technical

report, September 1994 Available from the Executive Secretary of

IAPWS or on the internet: http://www.iapws.org/

[9.4] J J Jasper The surface tension of pure liquid compounds J Phys.

Chem Ref Data, 1(4):841–1010, 1972.

[9.5] M Okado and K Watanabe Surface tension correlations for several

fluorocarbon refrigerants Heat Transfer: Japanese Research, 17

(1):35–52, 1988

[9.6] A P Fröba, S Will, and A Leipertz Saturated liquid viscosity and

surface tension of alternative refrigerants Intl J Thermophys., 21

(6):1225–1253, 2000

[9.7] V.G Baidakov and I.I Sulla Surface tension of propane and

isobu-tane at near-critical temperatures Russ J Phys Chem., 59(4):551–

554, 1985

[9.8] P.O Binney, W.-G Dong, and J H Lienhard Use of a cubic equation

to predict surface tension and spinodal limits J Heat Transfer,

108(2):405–410, 1986

Trang 5

518 Chapter 9: Heat transfer in boiling and other phase-change configurations

[9.9] Y Y Hsu On the size range of active nucleation cavities on a

heating surface J Heat Transfer, Trans ASME, Ser C, 84:207–

216, 1962

[9.10] G F Hewitt Boiling In W M Rohsenow, J P Hartnett, and Y I

Cho, editors, Handbook of Heat Transfer, chapter 15 McGraw-Hill,

New York, 3rd edition, 1998

[9.11] K Yamagata, F Hirano, K Nishiwaka, and H Matsuoka Nucleate

boiling of water on the horizontal heating surface Mem Fac Eng.

Kyushu, 15:98, 1955.

[9.12] W M Rohsenow A method of correlating heat transfer data for

surface boiling of liquids Trans ASME, 74:969, 1952.

[9.13] I L Pioro Experimental evaluation of constants for the Rohsenow

pool boiling correlation Int J Heat Mass Transfer, 42:2003–2013,

1999

[9.14] R Bellman and R H Pennington Effects of surface tension and

viscosity on Taylor instability Quart Appl Math., 12:151, 1954.

[9.15] V Sernas Minimum heat flux in film boiling—a three

dimen-sional model In Proc 2nd Can Cong Appl Mech., pages 425–426,

[9.19] J H Lienhard, V K Dhir, and D M Riherd Peak pool boiling

heat-flux measurements on finite horizontal flat plates J Heat

Transfer, Trans ASME, Ser C, 95:477–482, 1973.

[9.20] J H Lienhard and V K Dhir Hydrodynamic prediction of peak

pool-boiling heat fluxes from finite bodies J Heat Transfer, Trans.

ASME, Ser C, 95:152–158, 1973.

Trang 6

References 519

[9.21] S S Kutateladze On the transition to film boiling under natural

convection Kotloturbostroenie, (3):10, 1948.

[9.22] K H Sun and J H Lienhard The peak pool boiling heat flux on

horizontal cylinders Int J Heat Mass Transfer, 13:1425–1439,

[9.25] P Sadasivan and J H Lienhard Sensible heat correction in laminar

film boiling and condensation J Heat Transfer, Trans ASME, 109:

545–547, 1987

[9.26] V K Dhir and J H Lienhard Laminar film condensation on plane

and axi-symmetric bodies in non-uniform gravity J Heat Transfer,

Trans ASME, Ser C, 93(1):97–100, 1971.

[9.27] P Pitschmann and U Grigull Filmverdampfung an waagerechten

zylindern Wärme- und Stoffübertragung, 3:75–84, 1970.

[9.28] J E Leonard, K H Sun, and G E Dix Low flow film boiling heat

transfer on vertical surfaces: Part II: Empirical formulations and

application to BWR-LOCA analysis In Proc ASME-AIChE Natl Heat

Transfer Conf St Louis, August 1976.

[9.29] J W Westwater and B P Breen Effect of diameter of horizontal

tubes on film boiling heat transfer Chem Eng Progr., 58:67–72,

1962

[9.30] P J Berenson Transition boiling heat transfer from a horizontal

surface M.I.T Heat Transfer Lab Tech Rep 17, 1960

[9.31] J H Lienhard and P T Y Wong The dominant unstable

wave-length and minimum heat flux during film boiling on a horizontal

cylinder J Heat Transfer, Trans ASME, Ser C, 86:220–226, 1964.

[9.32] L C Witte and J H Lienhard On the existence of two transition

boiling curves Int J Heat Mass Transfer, 25:771–779, 1982.

[9.33] J H Lienhard and L C Witte An historical review of the

hydrody-namic theory of boiling Revs in Chem Engr., 3(3):187–280, 1985.

Trang 7

520 Chapter 9: Heat transfer in boiling and other phase-change configurations

[9.34] J R Ramilison and J H Lienhard Transition boiling heat transfer

and the film transition region J Heat Transfer, 109, 1987.

[9.35] J M Ramilison, P Sadasivan, and J H Lienhard Surface factors

influencing burnout on flat heaters J Heat Transfer, 114(1):287–

290, 1992

[9.36] A E Bergles and W M Rohsenow The determination of

forced-convection surface-boiling heat transfer J Heat Transfer, Trans.

ASME, Series C, 86(3):365–372, 1964.

[9.37] E J Davis and G H Anderson The incipience of nucleate boiling

in forced convection flow AIChE J., 12:774–780, 1966.

[9.38] K Kheyrandish and J H Lienhard Mechanisms of burnout in urated and subcooled flow boiling over a horizontal cylinder In

sat-Proc ASME–AIChE Nat Heat Transfer Conf Denver, Aug 4–7 1985.

[9.39] A Sharan and J H Lienhard On predicting burnout in the jet-disk

configuration J Heat Transfer, 107:398–401, 1985.

[9.40] A L Bromley, N R LeRoy, and J A Robbers Heat transfer in

forced convection film boiling Ind Eng Chem., 45(12):2639–2646,

1953

[9.41] L C Witte Film boiling from a sphere Ind Eng Chem

Funda-mentals, 7(3):517–518, 1968.

[9.42] L C Witte External flow film boiling In S G Kandlikar, M Shoji,

and V K Dhir, editors, Handbook of Phase Change: Boiling and Condensation, chapter 13, pages 311–330 Taylor & Francis,

Philadelphia, 1999

[9.43] J G Collier and J R Thome Convective Boiling and Condensation.

Oxford University Press, Oxford, 3rd edition, 1994

[9.44] J C Chen A correlation for boiling heat transfer to saturatedfluids in convective flow ASME Prepr 63-HT-34, 5th ASME-AIChEHeat Transfer Conf Boston, August 1963

[9.45] S G Kandlikar A general correlation for saturated two-phase flow

boiling heat transfer inside horizontal and vertical tubes J Heat

Transfer, 112(1):219–228, 1990.

Trang 8

References 521

[9.46] D Steiner and J Taborek Flow boiling heat transfer in vertical

tubes correlated by an asymptotic model Heat Transfer Engr., 13

(2):43–69, 1992

[9.47] S G Kandlikar and H Nariai Flow boiling in circular tubes In S G

Kandlikar, M Shoji, and V K Dhir, editors, Handbook of Phase

Change: Boiling and Condensation, chapter 15, pages 367–402.

Taylor & Francis, Philadelphia, 1999

[9.48] V E Schrock and L M Grossman Forced convection boiling in

tubes Nucl Sci Engr., 12:474–481, 1962.

[9.49] M M Shah Chart correlation for saturated boiling heat transfer:

equations and further study ASHRAE Trans., 88:182–196, 1982.

[9.50] A E Gungor and R S H Winterton Simplified general correlation

for flow boiling heat transfer inside horizontal and vertical tubes

Chem Engr Res Des., 65:148–156, 1987.

[9.51] S G Kandlikar, S T Tian, J Yu, and S Koyama Further assessment

of pool and flow boiling heat transfer with binary mixtures In

G P Celata, P Di Marco, and R K Shah, editors, Two-Phase Flow

Modeling and Experimentation Edizioni ETS, Pisa, 1999.

[9.52] Y Taitel and A E Dukler A model for predicting flow regime

tran-sitions in horizontal and near horizontal gas-liquid flows AIChE

J., 22(1):47–55, 1976.

[9.53] A E Dukler and Y Taitel Flow pattern transitions in gas–liquid

systems measurement and modelling In J M Delhaye, N Zuber,

and G F Hewitt, editors, Advances in Multi-Phase Flow, volume II.

Hemisphere/McGraw-Hill, New York, 1985

[9.54] G F Hewitt Burnout In G Hetsroni, editor, Handbook of

Multi-phase Systems, chapter 6, pages 66–141 McGraw-Hill, New York,

1982

[9.55] Y Katto A generalized correlation of critical heat flux for

the forced convection boiling in vertical uniformly heated round

tubes Int J Heat Mass Transfer, 21:1527–1542, 1978.

[9.56] Y Katto and H Ohne An improved version of the generalized

correlation of critical heat flux for convective boiling in uniformly

Trang 9

522 Chapter 9: Heat transfer in boiling and other phase-change configurations

heated vertical tubes Int J Heat Mass Transfer, 27(9):1641–1648,

1984

[9.57] P B Whalley Boiling, Condensation, and Gas-Liquid Flow Oxford

University Press, Oxford, 1987

[9.58] B Chexal, J Horowitz, G McCarthy, M Merilo, J.-P Sursock, J rison, C Peterson, J Shatford, D Hughes, M Ghiaasiaan, V.K Dhir,

Har-W Kastner, and Har-W Köhler Two-phase pressure drop technologyfor design and analysis Tech Rept 113189, Electric Power Re-search Institute, Palo Alto, CA, August 1999

[9.59] I G Shekriladze and V I Gomelauri Theoretical study of laminar

film condensation of flowing vapour Int J Heat Mass Transfer,

9:581–591, 1966

[9.60] P J Marto Condensation In W M Rohsenow, J P Hartnett, and

Y I Cho, editors, Handbook of Heat Transfer, chapter 14

McGraw-Hill, New York, 3rd edition, 1998

[9.61] J Rose, Y Utaka, and I Tanasawa Dropwise condensation In S G

Kandlikar, M Shoji, and V K Dhir, editors, Handbook of Phase

Change: Boiling and Condensation, chapter 20 Taylor & Francis,

Philadelphia, 1999

[9.62] D W Woodruff and J W Westwater Steam condensation on

elec-troplated gold: effect of plating thickness Int J Heat Mass

Trans-fer, 22:629–632, 1979.

[9.63] P D Dunn and D A Reay Heat Pipes Pergamon Press Ltd., Oxford,

UK, 4th edition, 1994

Trang 10

Part IV

Thermal Radiation Heat Transfer

523

Trang 12

10 Radiative heat transfer

The sun that shines from Heaven shines but warm, And, lo, I lie between that sun and thee:

The heat I have from thence doth little harm, Thine eye darts forth the fire that burneth me:

And were I not immortal, life were done Between this heavenly and earthly sun.

Venus and Adonis, Wm Shakespeare, 1593

Chapter 1 described the elementary mechanisms of heat radiation

Be-fore we proceed, you should reflect upon what you remember about the

following key ideas from Chapter1:

• Electromagnetic wave spectrum • The Stefan-Boltzmann law

• Heat radiation & infrared radiation • Wien’s law & Planck’s law

• Transmittance, τ • Transfer factor, F1–2

• e(T ) and e λ (T ) for black bodies

The additional concept of a radiation heat transfer coefficient was

devel-oped in Section2.3 We presume that all these concepts are understood

The heat exchange problem

Figure10.1shows two arbitrary surfaces radiating energy to one another

The net heat exchange, Qnet, from the hotter surface (1) to the cooler

525

Ngày đăng: 07/08/2014, 10:20

TỪ KHÓA LIÊN QUAN

w