Hello, can someone help me please explain why Celsius equals Kelvin in the solution shown in attached image?thank you

Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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Hello, can someone help me please explain why Celsius equals Kelvin in the solution shown in attached image?thank you

Units and Dimensions 25
32.174 lb ft0.453 59 24 kg 0.3048 m
(Ibf)
Ibf s?
X.
Ibf
1
lb
ft
(0.0254)² m²
in
(in?)
2.
in
kg m
= 6894.75
6894.75 N/m?
-
S m
(Table 2.7 gives 6.894 757 × 10' as the value for the conversion factor for
lbf
to pascal.)
in?
EXAMPLE 2.4 In the SI system, thermal conductivity has the unit W/(m K). The thermal
xQ
conductivity of a solid material can be calculated as k =
where Q is the rate of heat
ΑΔΤ
transfer, x is the thickness of solid, A is the area of heat transfer and AT is the temperature
difference across the solid. The following values were obtained experimentally: Q = 10 000 kJ/h,
A = 1 m2, x = 100 mm and AT = 800 K.
%3D
%3D
%3D
(a) Calculate the thermal conductivity of the solid in W/(m K).
(b) Express the thermal conductivity in kcal/(h m °C).
(c) If thermal conductivity of a second material is 0.15 Btu/(h ft °F), which one will make
a better thermal insulator?
Solution
1000 J
10 000 kJ
/(a) The rate of heat transfer, Q=10000 kJ/h =-
kJ
= 2777.78 I/s
3600 s
h
We have:
x = 100 mm = 0.1 m, A = 1 m², AT = 800 K
%3D
Substituting these values in the given equation, we get
xQ_0.1x 2777.78
k =
ΑΔΤ
1x 800
J
0.347
sm K
W
= 0.347
m K
%3D
W
0.347-"= 0.347
m K
J
(b)
sm K
cal
4.1868 J
cal
= 0.347
3 298.557-
°C
hm°C
S
3600 s
x m × K ×
K
Transcribed Image Text:Units and Dimensions 25 32.174 lb ft0.453 59 24 kg 0.3048 m (Ibf) Ibf s? X. Ibf 1 lb ft (0.0254)² m² in (in?) 2. in kg m = 6894.75 6894.75 N/m? - S m (Table 2.7 gives 6.894 757 × 10' as the value for the conversion factor for lbf to pascal.) in? EXAMPLE 2.4 In the SI system, thermal conductivity has the unit W/(m K). The thermal xQ conductivity of a solid material can be calculated as k = where Q is the rate of heat ΑΔΤ transfer, x is the thickness of solid, A is the area of heat transfer and AT is the temperature difference across the solid. The following values were obtained experimentally: Q = 10 000 kJ/h, A = 1 m2, x = 100 mm and AT = 800 K. %3D %3D %3D (a) Calculate the thermal conductivity of the solid in W/(m K). (b) Express the thermal conductivity in kcal/(h m °C). (c) If thermal conductivity of a second material is 0.15 Btu/(h ft °F), which one will make a better thermal insulator? Solution 1000 J 10 000 kJ /(a) The rate of heat transfer, Q=10000 kJ/h =- kJ = 2777.78 I/s 3600 s h We have: x = 100 mm = 0.1 m, A = 1 m², AT = 800 K %3D Substituting these values in the given equation, we get xQ_0.1x 2777.78 k = ΑΔΤ 1x 800 J 0.347 sm K W = 0.347 m K %3D W 0.347-"= 0.347 m K J (b) sm K cal 4.1868 J cal = 0.347 3 298.557- °C hm°C S 3600 s x m × K × K
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