BOOKCOMP, Inc. — John Wiley & Sons / Page 171 / 2nd Proofs / Heat Transfer Handbook / Bejan SPECIAL FUNCTIONS 171 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 [171], (11) Lines: 706 to 706 ——— 0.1901pt PgVar ——— Normal Page PgEnds: T E X [171], (11) TABLE 3.3 Gamma Function x Γ(x) x Γ(x) x Γ(x) x Γ(x) 1.00 1.00000 1.25 0.90640 1.50 0.88623 1.75 0.91906 1.01 0.99433 1.26 0.90440 1.51 0.88659 1.76 0.92137 1.02 0.98884 1.27 0.90250 1.52 0.88704 1.77 0.92376 1.03 0.98355 1.28 0.90072 1.53 0.88757 1.78 0.92623 1.04 0.97844 1.29 0.89904 1.54 0.88818 1.79 0.92877 1.05 0.97350 1.30 0.89747 1.55 0.88887 1.80 0.93138 1.06 0.96874 1.31 0.89600 1.56 0.88964 1.81 0.93408 1.07 0.96415 1.32 0.89464 1.57 0.89049 1.82 0.93685 1.08 0.95973 1.33 0.89338 1.58 0.89142 1.83 0.93969 1.09 0.95546 1.34 0.89222 1.59 0.89243 1.84 0.94261 1.10 0.95135 1.35 0.89115 1.60 0.89352 1.85 0.94561 1.11 0.94740 1.36 0.89018 1.61 0.89468 1.86 0.94869 1.12 0.94359 1.37 0.88931 1.62 0.89592 1.87 0.95184 1.13 0.93993 1.38 0.88854 1.63 0.89724 1.88 0.95507 1.14 0.93642 1.39 0.88785 1.64 0.89864 1.89 0.95838 1.15 0.93304 1.40 0.88726 1.65 0.90012 1.90 0.96177 1.16 0.92980 1.41 0.88676 1.66 0.90167 1.91 0.96523 1.17 0.92670 1.42 0.88636 1.67 0.90330 1.92 0.96877 1.18 0.92373 1.43 0.88604 1.68 0.90500 1.93 0.97240 1.19 0.92089 1.44 0.88581 1.69 0.90678 1.94 0.97610 1.20 0.91817 1.45 0.88566 1.70 0.90864 1.95 0.97988 1.21 0.91558 1.46 0.88560 1.71 0.91057 1.96 0.98374 1.22 0.91311 1.47 0.88563 1.72 0.91258 1.97 0.98768 1.23 0.91075 1.48 0.88575 1.73 0.91467 1.98 0.99171 1.24 0.90852 1.49 0.88595 1.74 0.91683 1.99 0.99581 2.00 1.00000 TABLE 3.4 Incomplete Gamma Function, Γ(a, x), a = 1.2 x Γ(a, x) 0.00 0.91817 0.10 0.86836 0.20 0.80969 0.30 0.75074 0.40 0.69366 0.50 0.63932 0.60 0.58813 0.70 0.54024 0.80 0.49564 0.90 0.45426 1.00 0.41597 BOOKCOMP, Inc. — John Wiley & Sons / Page 172 / 2nd Proofs / Heat Transfer Handbook / Bejan 172 CONDUCTION HEAT TRANSFER 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 [172], (12) Lines: 706 to 808 ——— 0.82916pt PgVar ——— Normal Page PgEnds: T E X [172], (12) TABLE 3.5 Incomplete Beta Function, B t (0.3, 0.5) xB t (0.3, 0.5) 0.00 0.00000 0.10 0.64802 0.20 0.94107 0.30 1.18676 0.40 1.41584 0.50 1.64284 0.60 1.87920 0.70 2.13875 0.80 2.44563 0.90 2.86367 1.00 4.55444 The incomplete beta function, B t (x,y), is defined by B t (x,y) = t 0 (1 − t) x−1 t y−1 dt (3.27) Values of B t (0.3, 0.5) for the range 0 ≤ t ≤ 1 generated using Maple V, Release 6.0 are given in Table 3.5. 3.3.4 Exponential Integral Function The exponential integral function E 1 (x) or −E i (−x) for a real argument x is defined by E 1 (x) or − E i (−x) = ∞ x e −t t dt (3.28) and has the following properties: E 1 (0) =∞ E 1 (∞) = 0 dE 1 (x) dx =− e −x x (3.29) As indicated by the entries in Table 3.6, the function decreases monotonically from the value E 1 (0) =∞to E 1 (∞) = 0asx is varied from 0 to ∞. 3.3.5 Bessel Functions Bessel functions of the first kind of order n and argument x, denoted by J n (x), and Bessel functions of the second kind of order n and argument x, denoted by Y n (x), are defined, respectively, by the infinite series BOOKCOMP, Inc. — John Wiley & Sons / Page 173 / 2nd Proofs / Heat Transfer Handbook / Bejan SPECIAL FUNCTIONS 173 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 [173], (13) Lines: 808 to 827 ——— 0.58415pt PgVar ——— Normal Page * PgEnds: Eject [173], (13) TABLE 3.6 Exponential Integral Function xE 1 (x) xE 1 (x) 0.00 ∞ 0.80 0.31060 0.01 4.03793 0.90 0.26018 0.02 3.35471 1.00 0.21938 0.03 2.95912 1.10 0.18599 0.04 2.68126 1.20 0.15841 0.05 2.46790 1.30 0.13545 0.06 2.29531 1.40 0.11622 0.07 2.15084 1.50 0.10002 0.08 2.02694 1.60 0.08631 0.09 1.91874 1.70 0.07465 0.10 1.82292 1.80 0.06471 0.15 1.46446 1.90 0.05620 0.20 1.22265 2.00 0.04890 0.30 0.90568 2.20 0.03719 0.40 0.70238 2.40 0.02844 0.50 0.55977 2.60 0.02185 0.60 0.45438 2.80 0.01686 0.70 0.37377 3.00 0.01305 J n (x) = ∞ m=0 (−1) m (x/2) 2m+n m! Γ(m + n + 1) (3.30) and Y n (x) = J n (x) cos nπ − J −n (x) sin nπ (n = 0, 1, 2, ) (3.31a) or Y n (x) = lim m→n J m (x) cos mπ − J −m (x) sin mπ (n = 0, 1, 2, ) (3.31b) Numerous recurrence relationships involving the Bessel functions are available (Andrews, 1992). Some that are relevant in this chapter are J −n (x) = (−1) n J n (x) (3.32) dJ n (x) dx = J n−1 (x) − n x J n (x) = n x J n (x) − J n+1 (x) (3.33) d dx x n J n (x) = x n J n−1 (x) (3.34) d dx x −n J n (x) =−x −n J n+1 (x) (3.35) BOOKCOMP, Inc. — John Wiley & Sons / Page 174 / 2nd Proofs / Heat Transfer Handbook / Bejan 174 CONDUCTION HEAT TRANSFER 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 [174], (14) Lines: 827 to 878 ——— 0.74718pt PgVar ——— Normal Page PgEnds: T E X [174], (14) The relations given by eqs. (3.32)–(3.35) apply to the Bessel functions of the second kind when the J ’s are replaced by Y ’s. Modified Bessel functions of the first kind of order n and argument x, denoted by I n (x), and modified Bessel functions of the second kind of order n and argument x, denoted by K n (x), are defined, respectively, by the infinite series I n (x) = ∞ m=0 (x/2) 2m+n m! Γ(m + n + 1) (3.36) and K n (x) = π 2 sin nπ I −n (x) − I n (x) (n = 0, 1, 2, ) (3.37a) or K n (x) = lim m→n π 2 sin nπ I −m (x) − I m (x) (n = 0, 1, 2, ) (3.37b) I n (x) and K n (x) are real and positive when n>−1 and x>0. A selected few of the numerous recurrence relationships involving the modified Bessel functions are I n (x) = (ι) −n J n (ιx) (3.38) I −n (x) = (ι) n J −n (ιx) (3.39) dI n (x) dx = I n−1 (x) − n x I n (x) = n x I n (x) + I n+1 (x) (3.40) d dx x n I n (x) = x n I n−1 (x) (3.41) d dx x −n I n (x) = x −n I n+1 (x) (3.42) K −n (x) = K n (x) (n = 0, 1, 2, 3, ) (3.43) dK n (x) dx = n x K n (x) − K n+1 (x) =−K n−1 (x) − n x K n (x) (3.44) d dx x n K n (x) =−x n K n−1 (x) (3.45) d dx x −n K n (x) =−x −n K n+1 (x) (3.46) Fairly extensive tables for the Bessel functions and modified Bessel functions of orders 1 and 2 and those of fractional order I −1/3 (x), I −2/3 (x), I 1/3 (x), and I 2/3 (x) in the range 0 ≤ x ≤ 5 with a refined interval are given in Kern and Kraus (1972), and polynomial approximations are given by Kraus et al. (2001), culled from the work of Abramowitz and Stegun (1955). Maple V, Release 6.0 can also be used to BOOKCOMP, Inc. — John Wiley & Sons / Page 175 / 2nd Proofs / Heat Transfer Handbook / Bejan SPECIAL FUNCTIONS 175 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 [175], (15) Lines: 878 to 892 ——— 0.714pt PgVar ——— Normal Page PgEnds: T E X [175], (15) generate these tables. Figure 3.2 displays graphs of J 0 (x), J 1 (x), Y 0 (x), and Y 1 (x). These functions exhibit oscillatory behavior with amplitude decaying as x increases. Figure 3.3 provides plots of I 0 (x), I 1 (x), K 0 (x), and K 1 (x) as a function of x and these functions exhibit monotonic behavior. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 Ϫ1.5 Ϫ1.0 Ϫ0.5 0.0 0.5 1.0 1.5 Bessel Function Jx 0 () Yx 0 () Jx 1 () Yx 1 () x Figure 3.2 Graphs of J 0 (x), J 1 (x), Y 0 (x), and Y 1 (x). Figure 3.3 Graphs of I 0 (x), I 1 (x), K 0 (x), and K 1 (x). BOOKCOMP, Inc. — John Wiley & Sons / Page 176 / 2nd Proofs / Heat Transfer Handbook / Bejan 176 CONDUCTION HEAT TRANSFER 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 [176], (16) Lines: 892 to 974 ——— 0.36082pt PgVar ——— Normal Page PgEnds: T E X [176], (16) Thomson functions ber i (x), bei i (x), ker i (x), and kei i (x) arise in obtaining the real and imaginary parts of the modified Bessel functions of imaginary argument. The subscripts i denote the order of the Thomson functions. Note that it is cus- tomary to omit the subscript when dealing with Thomson functions of zero order. Hence ber 0 (x), bei 0 (x), ker 0 (x), and kei 0 (x) are written as ber(x), bei(x), ker(x), and kei(x). The Thomson functions are defined by I 0 (x √ ι) = ber(x) + ι bei(x) (3.47) K 0 (x √ ι) = ker(x) + ι kei(x) (3.48) with ber(0) = 1 bei(0) = 0ker(0) =∞ kei(0) =−∞ (3.49) Expressions for the derivatives of the Thomson functions are d dx [ ber(x) ] = 1 √ 2 [ ber 1 (x) + bei 1 (x) ] (3.50) d dx [ bei(x) ] = 1 √ 2 [ bei 1 (x) − ber 1 (x) ] (3.51) d dx [ ker(x) ] = 1 √ 2 [ ker 1 (x) + kei 1 (x) ] (3.52) d dx [ kei(x) ] = 1 √ 2 [ kei 1 (x) − ker 1 (x) ] (3.53) Table 3.7 gives the values of ber(x), bei(x), ker(x), and kei(x) for 1 ≤ x ≤ 5, and the values of dber(x)/dx, dbei(x)/dx, dker(x)/dx, and dkei(x)/dx are pro- vided for the same range of x values in Table 3.8. Figure 3.4 displays graphs of ber(x), bei(x), ker(x), and kei(x). TABLE 3.7 Functions ber(x), bei(x), ker(x), and kei(x) x ber(x) bei(x) ker(x) kei(x) 1.00 0.98438 0.24957 0.28671 −0.49499 1.50 0.92107 0.55756 0.05293 −0.33140 2.00 0.75173 0.97229 −0.04166 −0.20240 2.50 0.39997 1.45718 −0.06969 −0.11070 3.00 −0.22138 1.93759 −0.06703 −0.05112 3.50 −1.19360 2.28325 −0.05264 −0.01600 4.00 −2.56342 2.29269 −0.03618 0.00220 4.50 −4.29909 1.68602 −0.02200 0.00972 5.00 −6.23008 0.11603 −0.01151 0.01119 BOOKCOMP, Inc. — John Wiley & Sons / Page 177 / 2nd Proofs / Heat Transfer Handbook / Bejan SPECIAL FUNCTIONS 177 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 [177], (17) Lines: 974 to 1000 ——— 0.45917pt PgVar ——— Normal Page PgEnds: T E X [177], (17) TABLE 3.8 Functions d ber(x)/dx, d bei(x)/dx, d ker(x), dx, and d kei(x)/dx xdber(x)/dx d bei(x)/dx d ker(x)/dx d kei(x)/dx 1.00 −0.06245 0.49740 −0.69460 0.35237 1.50 −0.21001 0.73025 −0.29418 0.29561 2.00 −0.49307 0.91701 −0.10660 0.21981 2.50 −0.94358 0.99827 −0.01693 0.14890 3.00 −1.56985 0.88048 0.02148 0.09204 3.50 −2.33606 0.43530 0.03299 0.05098 4.00 −3.13465 −0.49114 0.03148 0.02391 4.50 −3.75368 −2.05263 0.02481 0.00772 5.00 −3.84534 −4.35414 0.01719 −0.00082 Figure 3.4 Thomson functions. 3.3.6 Legendre Functions The Legendre function, also known as the Legendre polynomial P n (x), and the asso- ciated Legendre function of the first kind P m n (x), are defined by P n (x) = 1 2 n n! d n dx n (x 2 − 1) n (3.54) P m n (x) = (1 − x 2 ) m/2 d m dx m [ P n (x) ] (3.55) The Legendre function Q n (x) and the associated Legendre function of the second kind, Q m n (x), are defined by Q n (x) = (−1) n/2 · 2 n [ (n/2)! ] 2 n! × x − (n − 1)(n + 2) 3! x 3 + (n − 1)(n − 3)(n + 2)(n + 4) 5! x 5 −··· (n = even, |x| < 1) (3.56) BOOKCOMP, Inc. — John Wiley & Sons / Page 178 / 2nd Proofs / Heat Transfer Handbook / Bejan 178 CONDUCTION HEAT TRANSFER 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 [178], (18) Lines: 1000 to 1068 ——— -4.87883pt PgVar ——— Normal Page PgEnds: T E X [178], (18) Q n (x) = (−1) (n+1)/2 · 2 n−1 ( [ (n − 1)/2 ] ! ) 2 1 · 3 · 5 ···n × 1 − n(n + 1) 2! x 2 − n(n − 2)(n + 1)(n + 3) 4! x 4 −··· (n = odd, |x| < 1) (3.57) Q m n (x) = (1 − x 2 ) m/2 d m dx m [ Q n (x) ] (3.58) Several relationships involving P n (x), Q n (x), P m n (x), and Q m n (x) are useful in heat conduction analysis. They are P n (−x) = (−1) n P n (x) (3.59) P n+1 (x) = 2n + 1 n + 1 xP n (x) − n n + 1 P n−1 (x) (3.60) d dx P n+1 (x) − d dx P n−1 (x) = 2(n + 1)P n (x) (3.61) Q n (x =±1) =∞ (3.62) P m n (x) = 0 (m>n) (3.63) Q m n (x =±1) =∞ (3.64) The numerical values of the Legendre functions and their graphs can be generated with Maple V, Release 6.0. Table 3.9 lists the values of P 0 (x) through P 4 (x) for the range −1 ≤ x ≤ 1, and a plot of these functions appears in Fig. 3.5. 3.4 STEADY ONE-DIMENSIONAL CONDUCTION In this section we consider one-dimensional steady conduction in a plane wall, a hollow cylinder, and a hollow sphere. The objective is to develop expressions for the temperature distribution and the rate of heat transfer. The concept of thermal resistance is utilized to extend the analysis to composite systems with convection occurring at the boundaries. Topics such as contact conductance, critical thickness of insulation, and the effect of uniform internal heat generation are also discussed. 3.4.1 Plane Wall Consider a plane wall of thickness L made of material with a thermal conductivity k, as illustrated in Fig. 3.6. The temperatures at the two faces of the wall are fixed at T s,1 and T s,2 with T s,1 >T s,2 . For steady conditions with no internal heat generation and constant thermal conductivity, the appropriate form of the general heat conduction equation, eq. (3.4), is BOOKCOMP, Inc. — John Wiley & Sons / Page 179 / 2nd Proofs / Heat Transfer Handbook / Bejan STEADY ONE-DIMENSIONAL CONDUCTION 179 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 [179], (19) Lines: 1068 to 1068 ——— 0.01505pt PgVar ——— Normal Page PgEnds: T E X [179], (19) TABLE 3.9 Numerical Values of P n (x) xP 0 (x) P 1 (x) P 2 (x) P 3 (x) P 4 (x) −1.00 1.00000 −1.00000 1.00000 −1.00000 1.00000 −0.80 1.00000 −0.80000 0.46000 −0.08000 −0.23300 −0.60 1.00000 −0.60000 0.04000 0.36000 −0.40800 −0.40 1.00000 −0.40000 −0.26000 0.44000 −0.11300 −0.20 1.00000 −0.20000 −0.44000 0.28000 0.23200 0.00 1.00000 0.00000 −0.50000 0.00000 0.37500 0.20 1.00000 0.20000 −0.44000 −0.28000 0.23200 0.40 1.00000 0.40000 −0.26000 −0.44000 −0.11300 0.60 1.00000 0.60000 0.04000 −0.36000 −0.40800 0.80 1.00000 0.80000 0.46000 0.08000 −0.23300 1.00 1.00000 1.00000 1.00000 1.00000 1.00000 Ϫ1 Ϫ1 Ϫ0.5 Ϫ0.5 0 0.5 0.5 1 1 x Px(2, ) Px(5, ) Px(3, ) Px(1, ) Px(4, ) Figure 3.5 Legendre polynomials. BOOKCOMP, Inc. — John Wiley & Sons / Page 180 / 2nd Proofs / Heat Transfer Handbook / Bejan 180 CONDUCTION HEAT TRANSFER 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 [180], (20) Lines: 1068 to 1105 ——— 0.74109pt PgVar ——— Normal Page PgEnds: T E X [180], (20) Figure 3.6 One-dimensional conduction through a plane wall. d 2 T dx 2 = 0 (3.65) with the boundary conditions expressed as T(x= 0) = T s,1 and T(x = L) = T s,2 (3.66) Integration of eq. (3.65) with subsequent application of the boundary conditions of eq. (3.66) gives the linear temperature distribution T = T s,1 + (T s,2 − T s,1 ) x L (3.67) and application of Fourier’s law gives q = kA(T s,1 − T s,2 ) L (3.68) where A is the wall area normal to the direction of heat transfer. 3.4.2 Hollow Cylinder Figure 3.7 shows a hollow cylinder of inside radius r 1 , outside radius r 2 , length L, and thermal conductivity k. The inside and outside surfaces are maintained at constant temperatures T s,1 and T s,2 , respectively with T s,1 >T s,2 . For steady-state conduction . Wiley & Sons / Page 172 / 2nd Proofs / Heat Transfer Handbook / Bejan 172 CONDUCTION HEAT TRANSFER 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 [172],. Wiley & Sons / Page 174 / 2nd Proofs / Heat Transfer Handbook / Bejan 174 CONDUCTION HEAT TRANSFER 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 [174],. Wiley & Sons / Page 176 / 2nd Proofs / Heat Transfer Handbook / Bejan 176 CONDUCTION HEAT TRANSFER 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 [176],