Question
(a) A vertical building external envelope of 5mtimes 5m is made of opaque wall. The surface absorptance alpha of the wall is 0.473 . The
(a) A vertical building external envelope of
5m\\\\times 5m
is made of opaque wall. The surface absorptance
\\\\alpha
of the wall is 0.473 . The wall thickness is
100mm
, and its thermal conductivity is
0.06(W)/(m*K)
. Indoor air temperature is maintained at
23\\\\deg C
. The indoor air convective heat transfer coefficient,
h_(i)
, is at
3.64(W)/(m^(2)*K)
and the outdoor air convective heat transfer coefficient is related to outdoor air velocity,
v
, as follows:\
h_(o)=10+3.272v,[(W)/(m^(2)*K)]
\ At
2pm
on
21July
, the outdoor air temperature is
33.3\\\\deg C
, the outdoor air velocity,
v
, is
2.5(m)/(s)
and the incoming total surface irradiance,
I_(t)
, is
436.7(W)/(m^(2))
.\ Determine the percentage reduction in total heat input at the external surface of the envelope, if an additional layer of
30mm
thick is added to the external side of the wall, at the above time and date. Assume that the surface absorptance of the wall after adding the layer is only
50%
of its original value of 0.473 , and that the thermal conductivity of the additional layer,
K^(')
, is 0.025
(W)/(m*K)
. All other parameters remain unchanged after adding the layer.\ (15 marks)
Step by Step Solution
There are 3 Steps involved in it
Step: 1
Get Instant Access to Expert-Tailored Solutions
See step-by-step solutions with expert insights and AI powered tools for academic success
Step: 2
Step: 3
Ace Your Homework with AI
Get the answers you need in no time with our AI-driven, step-by-step assistance
Get Started