Calculate the rate of steady heat transfer from a 8 m-by-10 m roof of a building during a cold winter day. The roof temperature can be assumed to be constant at 12°C. The air temperature outside the building is -5°C. The sky temperature is -17°C. The solar irradiation at the location is 500 W/m². The convection coefficient can be assumed to be 8 W/m².°c. The emissivity of the roof is 0.75, and solar absorptivity is D.4. Neglect any conduction via the walls to the ground. 2173 W
Calculate the rate of steady heat transfer from a 8 m-by-10 m roof of a building during a cold winter day. The roof temperature can be assumed to be constant at 12°C. The air temperature outside the building is -5°C. The sky temperature is -17°C. The solar irradiation at the location is 500 W/m². The convection coefficient can be assumed to be 8 W/m².°c. The emissivity of the roof is 0.75, and solar absorptivity is D.4. Neglect any conduction via the walls to the ground. 2173 W
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
Problem 1.1MA
Related questions
Question
show work please. no previos attempts

Transcribed Image Text:Table 4
Properties of saturated water
Temp.
T, °C
0.01
5
10
15
20
25
Enthalpy Specific
of
Heat
Density
p, kg/m³
Thermal
Conductivity
k, W/m.K
Vaporization Cp, J/kg.K
hfg, kJ/kg
Liquid Vapor
Liquid Vapor
7.384
9.593
12.35
15.76
19.94
25.03
31.19
38.58
47.39
57.83
70.14
84.55
Liquid Vapor
Liquid
0.6113 999.8 0.0048 2501 4217 1854 0.561 0.0171 1.792 x 10-3
0.8721 999.9 0.0068 2490 4205 1857 0.571 0.0173 1.519 x 10-3
1.2276 999.7 0.0094 2478 4194 1862 0.580 0.0176 1.307 x 10-3
1.7051 999.1 0.0128 2466 4185 1863 0.589 0.0179 1.138 x 10-3
2.339 998.0 0.0173 2454 4182 1867 0.598 0.0182 1.002 × 10-³
3.169 997.0 0.0231 2442 4180 1870 0.607 0.0186 0.891 x 10-3
4.246 996.0 0.0304 2431 4178 1875 0.615 0.0189 0.798 x 10-3
5.628 994.0 0.0397 2419 4178 1880 0.623 0.0192 0.720 x 10-3
992.1 0.0512 2407 4179 1885 0.631 0.0196 0.653 x 10-3
990.1 0.0655 2395 4180 1892 0.637 0.0200 0.596 x 10-3
988.1 0.0831 2383 4181 1900 0.644 0.0204 0.547 x 10-3
985.2 0.1045 2371 4183 1908 0.649 0.0208 0.504 x 10-3
983.3 0.1304 2359 4185 1916 0.654 0.0212 0.467 x 10-3
980.4 0.1614 2346 4187 1926 0.659 0.0216 0.433 x 10-3
977.5 0.1983 2334 4190 1936
0.663 0.0221 0.404 x 10-3
974.7 0.2421 2321 4193 1948 0.667 0.0225 0.378 x 10-
971.8 0.2935 2309 4197 1962 0.670 0.0230 0.355 x 10-3
968.1 0.3536 2296 4201 1977 0.673 0.0235 0.333 x 10-3
965.3 0.4235 2283 4206 1993 0.675 0.0240 0.315 × 10-3
961.5 0.5045 2270 4212 2010 0.677 0.0246 0.297 x 10-3
957.9 0.5978 2257
0.679 0.0251 0.282 x 10-3
0.682 0.0262 0.255 × 10-3
2203
0.683 0.0275 0.232 x 10-3
2174 4263 2177 0.684 0.0288 0.213 x 10-3
2145 4286 2244 0.683 0.0301 0.197 x 10-3
2114 4311 2314 0.682 0.0316 0.183 x 10-3
2083 4340 2420 0.680 0.0331 0.170 x 10-3
2050 4370 2490 0.677 0.0347 0.160 x 10-3
2015 4410 2590 0.673 0.0364 0.150 x 10-3
1979 4460 2710 0.669 0.0382 0.142 x 10-3
1941
2840 0.663 0.0401 0.134 x 10-3
1859 4610 3110 0.650 0.0442 0.122 x 10-3
1767 4760 3520 0.632 0.0487 0.111 x 10-3
1663 4970 4070 0.609 0.0540 0.102 x 10-3
1544 5280 4835 0.581 0.0605 0.094 x 10-3
1405 5750 5980 0.548 0.0695 0.086 x 10-3
1239 6540 7900 0.509 0.0836 0.078 x 10-3
1028 8240 11,870 0.469 0.110 0.070 x 10-3
720 14,690 25,800 0.427 0.178 0.060 x 10-3
0
0.043 x 10-3
101.33
4217
2029
143.27
950.6 0.8263
2230
4229
2071
198.53
943.4 1.121
4244
2120
270.1
934.6 1.496
361.3
921.7 1.965
475.8
916.6 2.546
907.4 3.256
617.8
791.7
1,002.1
897.7 4.119
887.3 5.153
876.4 6.388
1,254.4
1,553.8
4500
864.3 7.852
840.3 11.60
813.7 16.73
783.7 23.69
750.8 33.15
713.8 46.15
667.1 64.57
610.5 92.62
528.3 144.0
317.0 317.0
Saturation
Pressure
Psat, kPa
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
110
120
130
140
150
160
170
180
190
200
220
2,318
240
3,344
260
4,688
280
6,412
300 8,581
320 11,274
340 14,586
360 18,651
374.14 22,090
Dynamic Viscosity
μ, kg/m.s
Vapor
0.922 x 10-5
0.934 x 10-5
0.946 x 10-5
0.959 x 10-5
0.973 x 10-5
0.987 x 10-5
1.001 x 10-5
1.016 × 10-5
1.031 x 10-5
1.046 x 10-5
1.062 x 10-5
1.077 x 10-5
1.093 x 10-5
1.110 x 10-5
1.126 x 10-5
1.142 x 10-5
1.159 x 10-5
1.176 x 10-5
1.193 x 10-5
1.210 x 10-5
1.227 x 10-5
1.261 x 10-5
1.296 x 10-5
1.330 x 10-5
1.365 x 10-5
1.399 x 10-5
1.434 x 10-5
1.468 x 10-5
1.502 x 10-5
1.537 x 10-5
1.571 x 10-5
1.641 x 10-5
1.712 x 10-5
1.788 x 10-5
1.870 x 10-5
1.965 x 10-5
2.084 x 10-5
2.255 x 10-5
2.571 x 10-5
4.313 x 10-5
Prandtl
Number
Pr
Liquid Vapor
13.5
11.2 1.00
9.45 1.00
8.09 1.00
7.01 1.00
6.14 1.00
5.42 1.00
4.83 1.00
4.32 1.00
3.91 1.00
3.55 1.00
3.25 1.00
2.99 1.00
2.75 1.00
2.55
1.00
1.00
2.38
2.22
1.00
1.00
1.00
1.01
2.08
1.96
1.85 1.00
1.75 1.00
1.58 1.00
1.44 1.00
1.33
1.24 1.02
1.16 1.02
1.09 1.05
1.03 1.05
0.983 1.07
0.947 1.09
0.910 1.11
0.865 1.15
0.836 1.24
0.832 1.35
0.854 1.49
0.902 1.69
1.00 1.97
1.23 2.43
2.06 3.73
Volume
Expansion
Coefficient
B, 1/K
Liquid
1.00 -0.068 × 10-3
0.015 x 10-3
0.733 x 10-3
0.138 x 10-3
0.195 X 10-3
0.247 x 10-3
0.294 x 10-3
0.337 X 10-3
0.377 x 10-3
0.415 x 10-3
0.451 x 10-3
0.484 x 10-3
0.517 x 10-3
0.548 x 10-3
0.578 x 10-3
0.607 x 10-3
0.653 x 10-3
0.670 x 10-3
0.702 x 10-3
0.716 x 10-3
0.750 x 10-3
0.798 x 10-3
0.858 x 10-3
0.913 x 10-3
0.970 x 10-3
1.025 x 10-3
1.145 x 10-3
1.178 x 10-3
1.210 x 10-3
1.280 x 10-3
1.350 x 10-3
1.520 x 10-3
1.720 x 10-3
2.000 x 10-3
2.380 x 10-3
2.950 x 10-3
=
Note 1: Kinematic viscosity v and thermal diffusivity a can be calculated from their definitions, v = μ/p and a = k/pcp v/Pr. The temperatures 0.01°C, 100°C, and
374.14°C are the triple-, boiling-, and critical-point temperatures of water, respectively. The properties listed above (except the vapor density) can be used at any
pressure with negligible error except at temperatures near the critical-point value.
Note 2: The unit kJ/kg-°C for specific heat is equivalent to kJ/kg.K. and the unit W/m.°C for thermal conductivity is equivalent to W/m.K.

Transcribed Image Text:Calculate the rate of steady heat transfer from a 8 m-by-10 m roof of a building during a cold winter day.
The roof temperature can be assumed to be constant at 12°C. The air temperature outside the building is
-5°C. The sky temperature is -17°C. The solar irradiation at the location is 500 W/m². The convection
coefficient can be assumed to be 8 W/m².°c. The emissivity of the roof is 0.75, and solar absorptivity is
0.4. Neglect any conduction via the walls to the ground. 2173 W
Expert Solution

This question has been solved!
Explore an expertly crafted, step-by-step solution for a thorough understanding of key concepts.
Step by step
Solved in 3 steps with 22 images

Knowledge Booster
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, mechanical-engineering and related others by exploring similar questions and additional content below.Recommended textbooks for you

Elements Of Electromagnetics
Mechanical Engineering
ISBN:
9780190698614
Author:
Sadiku, Matthew N. O.
Publisher:
Oxford University Press

Mechanics of Materials (10th Edition)
Mechanical Engineering
ISBN:
9780134319650
Author:
Russell C. Hibbeler
Publisher:
PEARSON

Thermodynamics: An Engineering Approach
Mechanical Engineering
ISBN:
9781259822674
Author:
Yunus A. Cengel Dr., Michael A. Boles
Publisher:
McGraw-Hill Education

Elements Of Electromagnetics
Mechanical Engineering
ISBN:
9780190698614
Author:
Sadiku, Matthew N. O.
Publisher:
Oxford University Press

Mechanics of Materials (10th Edition)
Mechanical Engineering
ISBN:
9780134319650
Author:
Russell C. Hibbeler
Publisher:
PEARSON

Thermodynamics: An Engineering Approach
Mechanical Engineering
ISBN:
9781259822674
Author:
Yunus A. Cengel Dr., Michael A. Boles
Publisher:
McGraw-Hill Education

Control Systems Engineering
Mechanical Engineering
ISBN:
9781118170519
Author:
Norman S. Nise
Publisher:
WILEY

Mechanics of Materials (MindTap Course List)
Mechanical Engineering
ISBN:
9781337093347
Author:
Barry J. Goodno, James M. Gere
Publisher:
Cengage Learning

Engineering Mechanics: Statics
Mechanical Engineering
ISBN:
9781118807330
Author:
James L. Meriam, L. G. Kraige, J. N. Bolton
Publisher:
WILEY