Page 1 PROBLEM 3.1 KNOWN: One-dimensional, plane wall ...

More documents

Recommendations

Info

PROBLEM 3.6 (Cont.)If conduction, radiation, or conduction and radiation are neglected, the corresponding values of h and thepercentage errors are 18.5 W/m 2 ⋅K (27.6%), 16 W/m 2 ⋅K (10.3%), and 20 W/m 2 ⋅K (37.9%).(c) For a fixed value of T s = 27°C, the conduction loss remains at q′′ cond = 8 W/m 2 , which is also thefixed difference between P′′ elec and q′′ conv . Although this difference is not clearly shown in the plot for10 ≤ h ≤ 1000 W/m 2 ⋅K, it is revealed in the subplot for 10 ≤ 100 W/m 2 ⋅K.2000200Power dissipation, P''elec(W/m^2)1600120080040000 200 400 600 800 1000Power dissipation, P''elec(W/m^2)160120804000 20 40 60 80 100Convection coefficient, h(W/m^2.K)Convection coefficient, h(W/m^2.K)No conductionWith conductionNo conductionWith conductionErrors associated with neglecting conduction decrease with increasing h from values which aresignificant for small h (h < 100 W/m 2 ⋅K) to values which are negligible for large h.COMMENTS: In liquids (large h), it is an excellent approximation to neglect conduction and assumethat all of the dissipated power is transferred to the fluid.
PROBLEM 3.7KNOWN: A layer of fatty tissue with fixed inside temperature can experience differentoutside convection conditions.FIND: (a) Ratio of heat loss for different convection conditions, (b) Outer surfacetemperature for different convection conditions, and (c) Temperature of still air whichachieves same cooling as moving air (wind chill effect).SCHEMATIC:ASSUMPTIONS: (1) One-dimensional conduction through a plane wall, (2) Steady-stateconditions, (3) Homogeneous medium with constant properties, (4) No internal heatgeneration (metabolic effects are negligible), (5) Negligible radiation effects.PROPERTIES: Table A-3, Tissue, fat layer: k = 0.2 W/m⋅K.ANALYSIS: The thermal circuit for this situation isHence, the heat rate isTs,1 −T∞Ts,1−T∞q = =.RtotL/kA+1/hATherefore,⎡L 1⎤⎢+q k h⎥′′ calm ⎣ ⎦windy=.q′′ windy ⎡L 1⎤⎢+⎣kh⎥⎦calmApplying a surface energy balance to the outer surface, it also follows thatq′′ cond = q ′′ conv.Continued …..
Page 1 and 2: PROBLEM 3.1KNOWN: One-dimensional,
Page 3 and 4: PROBLEM 3.2 (Cont.)Surface temperat
Page 5 and 6: T∞,i − Ts,i 1hi0.10= = = 0.846,
Page 7 and 8: PROBLEM 3.4 (Cont.)7000Radiant heat
Page 9: PROBLEM 3.6KNOWN: Design and operat
Page 13 and 14: PROBLEM 3.8KNOWN: Dimensions of a t
Page 15 and 16: PROBLEM 3.9KNOWN: Thicknesses of th
Page 17 and 18: PROBLEM 3.11KNOWN: Drying oven wall
Page 19 and 20: PROBLEM 3.13KNOWN: Composite wall o
Page 21 and 22: PROBLEM 3.15KNOWN: Dimensions and m
Page 23 and 24: PROBLEM 3.17KNOWN: Total floor spac
Page 25 and 26: PROBLEM 3.18KNOWN: Concrete wall of
Page 27 and 28: (2)(2)(2)Rcdm K/WPROBLEM 3.19 (Cont
Page 29 and 30: and with ′′ ( B B)( c,2 − s,2
Page 31 and 32: PROBLEM 3.22KNOWN: Temperatures and
Page 33 and 34: PROBLEM 3.23 (Cont.)1300Temperature
Page 35 and 36: PROBLEM 3.25KNOWN: Thicknesses and
Page 37 and 38: PROBLEM 3.27KNOWN: Operating condit
Page 39 and 40: PROBLEM 3.28KNOWN: Dimensions, ther
Page 41 and 42: PROBLEM 3.29KNOWN: Conduction in a
Page 43 and 44: PROBLEM 3.31KNOWN: Temperature depe
Page 45 and 46: PROBLEM 3.33KNOWN: Steady-state tem
Page 47 and 48: PROBLEM 3.35KNOWN: Thickness and in
Page 49 and 50: PROBLEM 3.36KNOWN: Temperature and
Page 51 and 52: PROBLEM 3.37KNOWN: Inner and outer
Page 53 and 54: PROBLEM 3.38 (Cont.)2000016000Heat
Page 55 and 56: PROBLEM 3.39 (Cont.)and the heat ga
Page 57 and 58: PROBLEM 3.40 (Cont.)240Outer surfac
Page 59 and 60: PROBLEM 3.42KNOWN: Electric current
Page 61 and 62:
PROBLEM 3.43KNOWN: Diameter of elec
Page 63 and 64:
PROBLEM 3.44 (Cont.)(b) From an ene
Page 65 and 66:
PROBLEM 3.45 (Cont.)The heat extrac
Page 67 and 68:
PROBLEM 3.47KNOWN: Electric current
Page 69 and 70:
PROBLEM 3.48KNOWN: Saturated steam
Page 71 and 72:
PROBLEM 3.49KNOWN: Temperature and
Page 73 and 74:
PROBLEM 3.50 (Cont.)20002Heat loss,
Page 75 and 76:
PROBLEM 3.51KNOWN: Pipe wall temper
Page 77 and 78:
PROBLEM 3.53KNOWN: Surface temperat
Page 79 and 80:
PROBLEM 3.55KNOWN: Diameter of a sp
Page 81 and 82:
PROBLEM 3.56KNOWN: Sphere of radius
Page 83 and 84:
PROBLEM 3.58KNOWN: Dimensions of sp
Page 85 and 86:
PROBLEM 3.60KNOWN: Inner diameter,
Page 87 and 88:
PROBLEM 3.62KNOWN: Dimensions and m
Page 89 and 90:
PROBLEM 3.63 (Cont.)To maintain T 1
Page 91 and 92:
PROBLEM 3.65KNOWN: Thermal conducti
Page 93 and 94:
PROBLEM 3.67KNOWN: Spherical tank o
Page 95 and 96:
PROBLEM 3.69KNOWN: Critical and nor
Page 97 and 98:
PROBLEM 3.70 (Cont.)Similarly, with
Page 99 and 100:
PROBLEM 3.72KNOWN: Plane wall with
Page 101 and 102:
PROBLEM 3.73 (Cont.)qT( − LB) = T
Page 103 and 104:
PROBLEM 3.74 (Cont.)Substituting th
Page 105 and 106:
PROBLEM 3.75KNOWN: Composite wall o
Page 107 and 108:
PROBLEM 3.77KNOWN: Geometry and bou
Page 109 and 110:
PROBLEM 3.78KNOWN: Thermal conducti
Page 111 and 112:
PROBLEM 3.78 (Cont.)qL ⎛1 b ⎞Ts
Page 113 and 114:
and from Eq. (3) with x = L and T(L
Page 115 and 116:
PROBLEM 3.80 (Cont.)Surface energy
Page 117 and 118:
PROBLEM 3.82KNOWN: Distribution of
Page 119 and 120:
PROBLEM 3.84KNOWN: Cylindrical shel
Page 121 and 122:
PROBLEM 3.86KNOWN: Diameter, resist
Page 123 and 124:
PROBLEM 3.87KNOWN: Energy generatio
Page 125 and 126:
PROBLEM 3.88KNOWN: Radii and therma
Page 127 and 128:
PROBLEM 3.88 (Cont.)Clearly, the ab
Page 129 and 130:
PROBLEM 3.89 (Cont.)(b) Using the o
Page 131 and 132:
PROBLEM 3.90KNOWN: Electric current
Page 133 and 134:
PROBLEM 3.91KNOWN: Materials, dimen
Page 135 and 136:
PROBLEM 3.92KNOWN: Long rod experie
Page 137 and 138:
PROBLEM 3.94KNOWN: Radial distribut
Page 139 and 140:
Henceq2 2() = s,i + ( i − )PROBLE
Page 141 and 142:
PROBLEM 3.96 (Cont.)(b) With the co
Page 143 and 144:
PROBLEM 3.97 (Cont.)(b) The sphere
Page 145 and 146:
PROBLEM 3.98KNOWN: Radius, thicknes
Page 147 and 148:
The boundary conditions are:( ) = w
Page 149 and 150:
PROBLEM 3.101KNOWN: Dimensions of a
Page 151 and 152:
PROBLEM 3.102 (Cont.)Substituting f
Page 153 and 154:
PROBLEM 3.103 (Cont.)Hence, the tem
Page 155 and 156:
PROBLEM 3.105KNOWN: Electric power
Page 157 and 158:
PROBLEM 3.107KNOWN: TC wire leads a
Page 159 and 160:
PROBLEM 3.108KNOWN: Rod (D, k, 2L)
Page 161 and 162:
PROBLEM 3.109KNOWN: Long rod in ove
Page 163 and 164:
( ) θ ( )PROBLEM 3.110 (Cont.)1/2
Page 165 and 166:
PROBLEM 3.111 (Cont.)−( ) 1/21/22
Page 167 and 168:
PROBLEM 3.112 (Cont.)The gradient a
Page 169 and 170:
PROBLEM 3.114KNOWN: Dimensions, end
Page 171 and 172:
PROBLEM 3.116KNOWN: Dimensions and
Page 173 and 174:
PROBLEM 3.117 (Cont.)Continued...dT
Page 175 and 176:
PROBLEM 3.119KNOWN: Long, aluminum
Page 177 and 178:
PROBLEM 3.121KNOWN: Thickness, leng
Page 179 and 180:
PROBLEM 3.122KNOWN: Thickness, leng
Page 181 and 182:
PROBLEM 3.123KNOWN: Length, thickne
Page 183 and 184:
Page 185 and 186:
PROBLEM 3.126KNOWN: Pin fin of ther
Page 187 and 188:
PROBLEM 3.128KNOWN: Slender rod of
Page 189 and 190:
PROBLEM 3.130KNOWN: Arrangement of
Page 191 and 192:
PROBLEM 3.131KNOWN: Conditions asso
Page 193 and 194:
PROBLEM 3.132 (Cont.)N t(mm) η f R
Page 195 and 196:
2( ) ( )PROBLEM 3.133 (Cont.)25 0.0
Page 197 and 198:
The fin heat rate is( )( )PROBLEM 3
Page 199 and 200:
PROBLEM 3.135 (CONT.)Heat rate, qt(
Page 201 and 202:
PROBLEM 3.136 (Cont.)With w = 0.25
Page 203 and 204:
where( )( )sinh(mL) + h mk cosh(mL)
Page 205 and 206:
( )PROBLEM 3.138 (Cont.)C1 = 1+ η
Page 207 and 208:
PROBLEM 3.139 (Cont.)Heat generatio
Page 209 and 210:
PROBLEM 3.140 (Cont.)5000Heat rate,
Page 211 and 212:
PROBLEM 3.142KNOWN: Dimensions, bas
Page 213 and 214:
Page 215 and 216:
PROBLEM 3.146KNOWN: Dimensions, bas
Page 217 and 218:
PROBLEM 3.147 (Cont.)5 2 3/2( ) 1/2
Page 219 and 220:
PROBLEM 3.148 (Cont.)Once the heat
Page 221 and 222:
PROBLEM 3.149 (Cont.)R′′ t,c to
Page 223 and 224:
PROBLEM 3.151KNOWN: Internal and ex
Page 225:
PROBLEM 3.152 (Cont.)(c) For the pr
show all

Page 1 PROBLEM 3.1 KNOWN: One-dimensional, plane wall ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?