Question 2.97: Reconsider Problem 2.96. Using EES (or other) software, inve......

Thermodynamics An Engineering Approach Solutions Manual [1477844]

Reconsider Problem 2.96. Using EES (or other) software, investigate the effect of glass thickness on heat loss for the specified glass surface temperatures. Let the glass thickness vary from 0.2 to 2 cm. Plot the heat loss versus the glass thickness, and discuss the results.

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EES Reconsider Prob. 2.96. Using EES (or other) software, investigate the effect of glass thickness on heat loss for the specified glass surface temperatures. Let the glass thickness vary from 0.2 cm to 2 cm. Plot the heat loss versus the glass thickness, and discuss the results.

Analysis The problem is solved using EES, and the solution is given below.

FUNCTION klookup(material$)
    If material$='Glass' then klookup:=0.78
    If material$='Brick' then klookup:=0.72
    If material$='Fiber Glass' then klookup:=0.043
    If material$='Air' then klookup:=0.026
    If material$='Wood(oak)' then klookup:=0.17
END

L=2″[m]”
W=2″[m]”
{material$=’Glass’
T_in=10″[C]”
T_out=3″[C]”
k=0.78″[W/m-C]”
t=5″[hr]”
thickness=0.5″[cm]”}
k=klookup(material$)”[W/m-K]”
A=L*W”[m^2]”
Q_dot_loss=A*k*(T_in-T_out)/(thickness*convert(cm,m))”[W]”
Q_loss_total=Q_dot_loss*t*convert(hr,s)*convert(J,kJ)”[kJ]”

2-97

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$\mathrm{ Q_{loss,total} }$ [kJ]	Thickness [cm]
196560	0.2
98280	0.4
65520	0.6
49140	0.8
39312	1
32760	1.2
28080	1.4
24570	1.6
21840	1.8
19656	2

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