The rate of heat transfer to the irterior is termed the ,.instantaneous heat gain._IHG, and is given by
q,: IHG = hiQ*,i* t) (
By Eqs. (1s.22) and (15.29),
*= Ul[t",* + Irr. r cos(o10 - t, [email protected],)+],2r..2cos((,)20 _ll,z_%)+...] _ r-] (i5_1,
where
V
(15.31)
The quantity I, in Eq. (15.30) is called the dec,rement factor.The angle <D, is the anguladisplacement or lag between a harmonic of tne sot-air temp^"ritr." anO the same har-monic of the inside-surface rcmperature and heat flux-
&XAMPLE IS.2
Thc liSht{.,)l(n cd
'rrf
rt a .uildinp i;.ri.nlil lh.,ughoul a (lcru d,y rnt July 21 . Its I{)rati(nr N.{l d..s_nr)nh tariruJc. variarion ,,i.-r ,ii ,.,rp",iir.; ,;;;;ili ;;:'J.y io givun irr .l ahtc15.4. Ite roo{ xon$istr of 6 in. of c()nrtete, cr}vered by a t hin iayer of nroling which may henegleclcd in the s()lulir)n. 'l,,e lcrnr.r0turu rlf thc insiie ai, ao,i il,i"ri,l, surr,un<.ling surtaccsir 7ll'F' I)crcrminr'(a) thv rarc ofirear tra tlnis,ii,' lhrough lhc rx)frr) the r(xnrr bekrw.verthe lidl day a,,d (b) the rak .f heat tra,smissiru i't, their,.r:r it lreat-rtorag"
"rlbcts
of lheconclclo tlah Arc neglccted.
ltolatlon:
(l) Sinc!'*e ere uiing thble 15.4tne,havcrrr,,=.1.111g,u7,,.lr'..t.. lty.l.al)lc J4.1./l, = t.(ItBtu/hr - Il? . .F. By Tthte 14.{ tp, p = t4{) l,Jii;. i = r zir j ] ,.u tr,rrr,, . r, . "t,.. = l).21 Btullt'm , ,tr. ]tus, {r = I.r)/(140)(0.21) = 0.Of.r fiirirr, ry riq. frS.Z:1.
It* |I 0.5 , = t).57 Btu/hr . ,lr .
.l
t.ot
i
t.tt
|
.t.rrr
.. __ llte.fixrdametltal anguiar velocity tt, = 2r/?4 = (].26lti rad/hr = t5 deg/hr. llybq, (15.2.t).
,,'=
{,i,1,1,ii., - re6rt
i
aud .,, * V2 o * 2.77 fi r..llrus rr, r. - ().91i Bnd rr?1, = 1.385. Ly Eq. (1j.26).
* - l,ll;?,9,',?,, +, 11,.s:ro11r.r+.s1
, | (.].r))(r.$) _l-
lrii*iriii,, - r llr'r*,:;1r rzrr, , l,',11,J,,i]i,1,,,.557r))(r s20)
* 1.9.19
By Eq. (1.5.27),
4Al Porl V / HeotingF. ond CoolingElood Colculolions in Buildings
IABU 15.5 Conslonls for Eq. (15.30) for Vorlous Flot{oof Construcllons. All lnclude bulll-up rootlng. Nos. l-3 hov€ on olr rpoce
below loyer I ond obove o metol lolh ond ploster ceiling. Nos. 6-8 hove o 0.5 ln. (1.3 cm) gypsum ploster ceillng under loyer B.
Io
No. Descfiplion
U
Btu/ .fr2 .'F
(W/m'z .'C) )tr
or,
deg )t2
o2,
deg
Wnter Summer Wntet Summet Wlntet Summer Wntet 9ummet Wnler Summer
I A: 2 in. (5 cm) cellulor
gloss insulolion
B: 2 in. (5 cm)
concrete
0.137
(0.778)
0.r28
(o.727)
0.506 o.47 66.0 70.0 0.280 o.241 86.6 89.2
2 A: 2 in. (5 cm) cellulol
gloss insuloilon
B: 4 ln. (10 cm)
concl€t6
0.134
(0.76r)
0.125
(0.7r0)
o.279 o-zt 86.2 88.s o.142 0.121 I06.5 108.0
3 A: 4 in. (10 cm)
concrele
B: 2 in. (5 cm) cellulor
gloss insulollon
0.r34
(0.761)
0.125
(0.7r0)
0.566 0.5t 9 68.5 72.2 0.320 o.2 97.3 lm.2
4 Some qs No. I excepl
no oir spoce ond no
ceiling
0.159
(0.e03)
0.150
(0.8s2)
0.788 o.674 44.5 54.1 0.536 0.414 70.3 78.5
5 Some os No. 2 except
no olr spoc€ ond no
celllng
0.t55
(0.880)
0,I rt6 ...
UChicago CMSC 23320 - The Best Commit Messages of 2024
The rate of heat transfer to the irterior is termed the ,.inst.docx
1. The rate of heat transfer to the irterior is termed the
,.instantaneous heat gain._IHG, and is given by
q,: IHG = hiQ*,i* t) (
By Eqs. (1s.22) and (15.29),
*= Ul[t",* + Irr. r cos(o10 - t,
[email protected],)+],2r..2cos((,)20 _ll,z_%)+...] _ r-] (i5_1,
where
V
(15.31)
The quantity I, in Eq. (15.30) is called the dec,rement
factor.The angle <D, is the anguladisplacement or lag between a
harmonic of tne sot-air temp^"ritr." anO the same har-monic of
the inside-surface rcmperature and heat flux-
&XAMPLE IS.2
Thc liSht{.,)l(n cd
'rrf
rt a .uildinp i;.ri.nlil lh.,ughoul a (lcru d,y rnt July 21 . Its
I{)rati(nr N.{l d..s_nr)nh tariruJc. variarion ,,i.-r ,ii ,.,rp",iir.;
,;;;;ili ;;:'J.y io givun irr .l ahtc15.4. Ite roo{ xon$istr of 6 in. of
c()nrtete, cr}vered by a t hin iayer of nroling which may
henegleclcd in the s()lulir)n. 'l,,e lcrnr.r0turu rlf thc insiie ai,
ao,i il,i"ri,l, surr,un<.ling surtaccsir 7ll'F' I)crcrminr'(a) thv rarc
ofirear tra tlnis,ii,' lhrough lhc rx)frr) the r(xnrr bekrw.verthe
lidl day a,,d (b) the rak .f heat tra,smissiru i't, their,.r:r it lreat-
rtorag"
5. no oir spoce ond no
ceiling
0.159
(0.e03)
0.150
(0.8s2)
0.788 o.674 44.5 54.1 0.536 0.414 70.3 78.5
5 Some os No. 2 except
no olr spoc€ ond no
celllng
0.t55
(0.880)
0,I rt6
(0.829)
0.5I8 0.405 70.8 74.4 o.246 o.213 97.3 1e2.2
6 A 4 in. (10 cm)
exponded polystyrene
insulolion
B: 4 in, (10 cm)
conc16l€
0.0653
(0.37r)
0.0637
(0.362)
0.444 0.348 76.2 82.7 o.2aa 0.0t 8 t 01.8 105.8
6. 7 A: 4 ln. (10 cm) cellulor
gloss insulotion
B: 4 in. (I0 cm)
concreta
o.o773
(0.rl:}9)
0.0838
(0.476)
o.444 0.345 89.5 93.8 o.222 0.17l 127.3 127.5
I A: 8 in. (20 cm)
corkboord
B: 4 in. ( 10 cm)
concrele
0,032r
(0.r 82)
o.fi)17
(0.r 80)
0.t64 0.125 20,,..3 21 1.0 0.035 0.026 297.5 301.9
Table B.2 contains monthly and annual degree-day
information for seven cities in
the United States. The rnit, on tt'" O"giee-dafoata in.ttre
table are "'F'days'" The
;;";Hy ;;";;;;.utdoor-ar temperaiur? is utso ptovioed' Data are
7. listed for five values
of zero-load temperature: ,,. ",'oo,
el tttt" traditional. vatue)' and 70'F Note that the
annual number of degree days in"reaiessignificantly-
with an increase in zero-load tem''
perature for each locadon' Addi;ttt;il;;;"d"y data. are published
in reference [2]'
Erbs et al. [3] presented a metnoJi" "tti-it"
tf'e monthly and annual number of degree
davs based on monthty rn"un-u*Ui""t-i"lnperature data'
This method is useful in loca-
tions where degree-day data are unavailable'
The main use ot tn" O"gt"elJiy tetf'oO f to estimate the amount
of
fuel that will
be required to provide space hea ni{or a building' The amount
of energy required"E''
;;:;;i;:;;put.'tt'' ru"r 'li'itt,nent'
tr,'iv dividing it bv the average heating-
system efficiency and by the fuel heating value:
The average heating-system efficiency, 1*' is defined I. th: r?tio
of the thermal output
from the heating system divideo ufihi'n#ting nutu" ot the fuel
or energy input averaged
8. ;;; ;; fi-#;6J or trr" unurvtit' not iottiftu"r t*naces this efficiencv
is
less than the
steadv-state value. cycting at parii;uJ'Jt'""t tl'" u*ount of heat
delivered to the build-
"fi:ffi;; ffi;iil: fl"'"' A-sHRAr 1r1 gi'"t equatio-ns to estimate
rl,l for various
types of heating systems that "t" "
i"""ilo"'dt"-ersizing of the heating-system capacity
and the amount of heat losr out the ductwork' The
heatilg-system average efficiency can
be estimated from
E"
'P
"tnH
CF ny
: 0.7791 + 0.1983RLC - 0'0711(RLCF
(17.e)
(17.10)
(17.11)
r7.r2)
240,*".0".,r,(DD),., (17.13)
9. (/,, a*,en - L, u""t . h, Il
rL, CFpt
l.h: T+;;
where q". is the steady-state or rated heating-system
efficiency without cycling' CF'1 is a
funcrion of the type of heating tyti"* "J
pi"ii rclad efficiency' and o' is the fraction of
heat loss from ducs. For exampte, the vatui for CFr,
for a natural-gas furnace with inter-
mittent ignition is given as
where
RCL:
aod Oo*ou, is the rated output of the heating
equipment' For fossil-fuel furnaces CF'1 is
alwavs less than 1.0. For electrlc furnu""t ""i
hiui"tt the value is equal to 1'0'*-"'i;rot;;;;q..-tri.zl,
trilsi' '"d-iri'sr'
we can obtain an expression.ror the
amount of tuel used to provide tp'il f'""tirrg that dep^ends on
the design
heat-loss'and
temDerature conditions, ttre numtei of deg.J" duy. riferenced
to the correct zero-load
10. #Hffi;.ffi;;;;;.;;;il;"v"'^ "fti'l'*v' and the hearins
varue of the ruel:
24(UA)"ff (DD)..,
F: :
'P 1l,tH
Pof V / Heotlng- ond Coolinqlood Colculotions in Buildings$2
Qou,p*
15.2 suMMER DES',o't' co'{D',r'o'{s
The maximum heat gain
ever likely to be achieved in a
given building depends'on the out-
doorweatherffiiiil^t''r'"i"ati"""tp"t*u"'iu"iit..tiaitytttltt''uodthlus
aeeof
thespaceltd;#;;ili;u'"ait""t"amo"oiiinir'upt"rl2'Spaceoccupancva
nd
"tr,".
int"*"ri-"L.-"*'oi."r"*o in a later
seci'in in ,r,ir'"rtup,"t' fue will
focus on the
ffi #;;hffi fl"::uffi i}:;#;x*:::nil#'ilJ'#il:*:il:::
radiation is oflen treated
as clear-sky radlau^or
11. lationlevelsro,."r},i,ry"ooaidonsaregiveninChapter13.
Table r5.l lists some summer design
,..pJi"'"r"t i.r selected cilies around the
*o'ra' rn"t" it'i""i*Lt u'" ^"ut"'"d 't "i;;;
;t"ther weather slations The data
in raule rs'i rtaie been slatisticallv
*"rv'"[Jotl' ti-y"* p"rioo for which hourlv
weather data exist' --
c'r""i'"ii"'i""' the desisn drY-burb t'.TIffi.H ;,#ffi:itt;;;:1ff
t:t?*:H:
bv*"T:-T;"#y.:$ff ';:llt:'"lH'l[ff Hi;;;i'"u'io";rhedrY-butbtem-
mean coincident w"t-oiT''::-ti":"",.:;: i"Ll"'"r"o tt
"xceeded
I percent' 2'5 percenl'
*r+:x*}5;3;u;0#15,ffi I'-i'm*'ffi*i#:+ern HemisPJ
from Canad
fABtE t5.t Summe] Deslgn Climotic
Conditions
Col. 2
Design Dry'
Bulb/Meon
coincldent Wet8ulb
TemPeotwe <"F)
Col. 4
19. east' and w;st vertical surfaces' six or more harmon-
ics maY be needed'
cerre.aty]i".iooic heat transfer through a sunlit vertical wall is
small compared to
hear ffansfer rr,i|rgi-.
"
.*rit flat roof of th; same area. Thus. usually it is more impor-
tant to have *""'"'" .J"i' temperature information for a horizontal
surface than
for
vertical surfaces'
Followinj the same procedures described here' James C' Dunn-
developed
a
computef p."d;"";;;;;;i"J oirrnur sol-air remDerature variations
for horizontal
and vertica suiice. i-
"r"",
a^y.
"t
vrinneapolis for six different times of year [2]' Table
r5.s sfrows tris reluttfi. u fr"tirootuf surface. Constants in Eq.
(15.13) ar-e shgwn throush
t*otu,rno-
"t'Co"tuntsforthewinterdesigndayweredeterminedforclearDecem
-
20. ber-
Februarydayswhoseminimumlemperatureswereapproximately_20
"F.(_29"C).
constants for ;;.r--", a.G" a"y weie determined for clear June-
August days
whose
maximum temperatures were ipproximately 95 "F (35 "C)'
15.1 PEP'ODIC HEAT OA//N fiHPOUGH WALIS AND ROOFS
Heattransferthroughwallsandroofscanbetreatedasdiurnalforpurpo
sesofdesigncal-
culations. There-firJirr" ."r-* ,"-perature becomes the external
thermal boundary
con-
dition and the-indoor temperaturi becomes the indoor
thermal boundary condition.
rn"re tounoury'JorrJitions'u." coupled to the solid material
through
the external and
i,t"rrur .onu""iiu-t"-tiai"tiue turt'ce fitm coefficients' Thus the
problem becomes one in
which the .otlo t'^t convective coefficients on both sides with
the
fluid temperatures
changing in u ai"rnJrn*"t' The most important assumptions to be
made
on the solid
21. wall or roof ari':*(f i.i"-J rr""i,ransfer is'by conduction only (or
pseudoconduction
if
natural convedio; and infrared radiation are present in
air cavities or in porous insula-
tion), (2) co,,tiil"sisionc"s between layers o1 material are
neglected'
and (3) air infil-
tration/exfiltrationthroughthewallorroofconstructionisnegligible.
t|El
ctloP 15 / lnstonloneous H6ot Goin
IABIE A.3E Thelmodynomlc Propedies of R-22 ot Sqturotion
(Engllsh Units)
Ttp
Liquin
De^tity
h,n41,
Sp- YoL
fi"b,
Entvlpy, Datun
-&"F, Batllbn
Entropy, DalM
27. l5.t
rr.8
I
I rr.rI r?-9I rr-e
I rr.rI 20.OI uo.r
I z:EI ;i.i
1,,,
| 24.E
I zc.t
I ttz
I l.t-z
I uc.r
I ro-o
I ro-cI rr-e
4.9
5.4
5.8
6.3
6.9
7.1
7.9
8.5
9,0
9.5
93.77
93.31
92.85
9234
91.91
9!.,13
90.95
90.17
160. MAE 4175 El Final Exam
6-8 PM on April 29,2013
(Textbook and psychrometric chart only)
Student Name
Problem I (20 points)
Find values of humidity ratio, enthalpy, ffid specific volume for
saturated air at 14.696 psia
pressure for temperatwe of 75F from a psychrometric chart and
calculate the same values using
perfect gas relation and Table A.1
Problem 2 Q0 points)
Determine solar incidence angle for a south-facing vertical
161. surface at 1500 hr local solar time on
June 21, 40 degree North latitude.
Problem 3a (20 points)
Calculate the overall thermal resistance and average U factor
using the parallel-path method and
the isothermal-plane method for the 7 5/8 in. thick insulated
concrete block wall. The two-core
block has an u*r*g" web thickness of 1 in. and a face shell
thickness of 1
L/o in. Overall block
dimensions are I Sig by 7 5/8 by 15 5/8 in. Measured thermal
resistances of ll2 lblft3 concrete
and,T lb/ft3 expanded perlite insulation are 0.1 and
2.9h.frZ.F/Btu per inch, respectively.
Thermal resistanc*r of inside surface film and outside surf,ace
film are 0.68 and 0.L7 h.ftz.FlBtu,
respectively. The fractions of webs and cores to the total cross
section area are 0.192 md 0-808.
EXF*,.IDED FERLITE I'-ISUI.ATION
Problem 4 QA points)
Calculate the instantaneous rate of heat gain using Eq. 15.30,
Btu/hr.ft2, through a sunlit flat-roof
construction similar to No. 5 of Table 15.6 at 3:00PM solar time
162. on an average clear day at
Minneapolis for January. The indoor temperature is assumed to
be 70F.
Problem 5 Q0 points)
Estimate the amount of natural gas (cc$ required to heat a home
located in Atlanta, Georgia, for
one year if &e value for UA is 2000 Btu/hr.F, the internal gain
is 10,000 Btu&r, the thermostat is
set at 70F when the heating system is on, and the steady state
heating system efficiency is 85%.
It is assumed that the winter design temperature at 99o/o is 17F,
Eq. 17.11may be used to
calculate cycling loos, and duct loss fraction is 0.1 .
assignment.pdf
MAE 4175 El Final Exam
6-8 PM on April 29,2013
(Textbook and psychrometric chart only)
Student Name
Problem I (20 points)
Find values of humidity ratio, enthalpy, ffid specific volume for
saturated air at 14.696 psia
pressure for temperatwe of 75F from a psychrometric chart and
calculate the same values using
163. perfect gas relation and Table A.1
Problem 2 Q0 points)
Determine solar incidence angle for a south-facing vertical
surface at 1500 hr local solar time on
June 21, 40 degree North latitude.
Problem 3a (20 points)
Calculate the overall thermal resistance and average U factor
using the parallel-path method and
the isothermal-plane method for the 7 5/8 in. thick insulated
concrete block wall. The two-core
block has an u*r*g" web thickness of 1 in. and a face shell
thickness of 1
L/o in. Overall block
dimensions are I Sig by 7 5/8 by 15 5/8 in. Measured thermal
resistances of ll2 lblft3 concrete
and,T lb/ft3 expanded perlite insulation are 0.1 and
2.9h.frZ.F/Btu per inch, respectively.
Thermal resistanc*r of inside surface film and outside surf,ace
film are 0.68 and 0.L7 h.ftz.FlBtu,
respectively. The fractions of webs and cores to the total cross
section area are 0.192 md 0-808.
EXF*,.IDED FERLITE I'-ISUI.ATION
164. Problem 4 QA points)
Calculate the instantaneous rate of heat gain using Eq. 15.30,
Btu/hr.ft2, through a sunlit flat-roof
construction similar to No. 5 of Table 15.6 at 3:00PM solar time
on an average clear day at
Minneapolis for January. The indoor temperature is assumed to
be 70F.
Problem 5 Q0 points)
Estimate the amount of natural gas (cc$ required to heat a home
located in Atlanta, Georgia, for
one year if &e value for UA is 2000 Btu/hr.F, the internal gain
is 10,000 Btu&r, the thermostat is
set at 70F when the heating system is on, and the steady state
heating system efficiency is 85%.
It is assumed that the winter design temperature at 99o/o is 17F,
Eq. 17.11may be used to
calculate cycling loos, and duct loss fraction is 0.1 .
sampleProblem-table-equations.pdf
The rate of heat transfer to the irterior is termed the
,.instantaneous heat gain._IHG, and is given by
q,: IHG = hiQ*,i* t) (
By Eqs. (1s.22) and (15.29),
165. *= Ul[t",* + Irr. r cos(o10 - t,
[email protected],)+],2r..2cos((,)20 _ll,z_%)+...] _ r-] (i5_1,
where
V
(15.31)
The quantity I, in Eq. (15.30) is called the dec,rement
factor.The angle <D, is the anguladisplacement or lag between a
harmonic of tne sot-air temp^"ritr." anO the same har-monic of
the inside-surface rcmperature and heat flux-
&XAMPLE IS.2
Thc liSht{.,)l(n cd
'rrf
rt a .uildinp i;.ri.nlil lh.,ughoul a (lcru d,y rnt July 21 . Its
I{)rati(nr N.{l d..s_nr)nh tariruJc. variarion ,,i.-r ,ii ,.,rp",iir.;
,;;;;ili ;;:'J.y io givun irr .l ahtc15.4. Ite roo{ xon$istr of 6 in. of
c()nrtete, cr}vered by a t hin iayer of nroling which may
henegleclcd in the s()lulir)n. 'l,,e lcrnr.r0turu rlf thc insiie ai,
ao,i il,i"ri,l, surr,un<.ling surtaccsir 7ll'F' I)crcrminr'(a) thv rarc
ofirear tra tlnis,ii,' lhrough lhc rx)frr) the r(xnrr bekrw.verthe
lidl day a,,d (b) the rak .f heat tra,smissiru i't, their,.r:r it lreat-
rtorag"
"rlbcts
of lheconclclo tlah Arc neglccted.
ltolatlon:
(l) Sinc!'*e ere uiing thble 15.4tne,havcrrr,,=.1.111g,u7,,.lr'..t..
lty.l.al)lc J4.1./l, = t.(ItBtu/hr - Il? . .F. By Tthte 14.{ tp, p =
t4{) l,Jii;. i = r zir j ] ,.u tr,rrr,, . r, . "t,.. = l).21 Btullt'm , ,tr.
]tus, {r = I.r)/(140)(0.21) = 0.Of.r fiirirr, ry riq. frS.Z:1.
It* |I 0.5 , = t).57 Btu/hr . ,lr .
166. .l
t.ot
i
t.tt
|
.t.rrr
.. __ llte.fixrdametltal anguiar velocity tt, = 2r/?4 = (].26lti
rad/hr = t5 deg/hr. llybq, (15.2.t).
,,'=
{,i,1,1,ii., - re6rt
i
aud .,, * V2 o * 2.77 fi r..llrus rr, r. - ().91i Bnd rr?1, = 1.385.
Ly Eq. (1j.26).
* - l,ll;?,9,',?,, +, 11,.s:ro11r.r+.s1
, | (.].r))(r.$) _l-
lrii*iriii,, - r llr'r*,:;1r rzrr, , l,',11,J,,i]i,1,,,.557r))(r s20)
* 1.9.19
By Eq. (1.5.27),
4Al Porl V / HeotingF. ond CoolingElood Colculolions in
Buildings
IABU 15.5 Conslonls for Eq. (15.30) for Vorlous Flot{oof
Construcllons. All lnclude bulll-up rootlng. Nos. l-3 hov€ on olr
167. rpoce
below loyer I ond obove o metol lolh ond ploster ceiling. Nos.
6-8 hove o 0.5 ln. (1.3 cm) gypsum ploster ceillng under loyer
B.
Io
No. Descfiplion
U
Btu/ .fr2 .'F
(W/m'z .'C) )tr
or,
deg )t2
o2,
deg
Wnter Summer Wntet Summet Wlntet Summer Wntet 9ummet
Wnler Summer
I A: 2 in. (5 cm) cellulor
gloss insulolion
B: 2 in. (5 cm)
concrete
0.137
(0.778)
0.r28
(o.727)
0.506 o.47 66.0 70.0 0.280 o.241 86.6 89.2
2 A: 2 in. (5 cm) cellulol
169. 5 Some os No. 2 except
no olr spoc€ ond no
celllng
0.t55
(0.880)
0,I rt6
(0.829)
0.5I8 0.405 70.8 74.4 o.246 o.213 97.3 1e2.2
6 A 4 in. (10 cm)
exponded polystyrene
insulolion
B: 4 in, (10 cm)
conc16l€
0.0653
(0.37r)
0.0637
(0.362)
0.444 0.348 76.2 82.7 o.2aa 0.0t 8 t 01.8 105.8
7 A: 4 ln. (10 cm) cellulor
gloss insulotion
B: 4 in. (I0 cm)
concreta
o.o773
(0.rl:}9)
0.0838
170. (0.476)
o.444 0.345 89.5 93.8 o.222 0.17l 127.3 127.5
I A: 8 in. (20 cm)
corkboord
B: 4 in. ( 10 cm)
concrele
0,032r
(0.r 82)
o.fi)17
(0.r 80)
0.t64 0.125 20,,..3 21 1.0 0.035 0.026 297.5 301.9
Table B.2 contains monthly and annual degree-day
information for seven cities in
the United States. The rnit, on tt'" O"giee-dafoata in.ttre
table are "'F'days'" The
;;";Hy ;;";;;;.utdoor-ar temperaiur? is utso ptovioed' Data are
listed for five values
of zero-load temperature: ,,. ",'oo,
el tttt" traditional. vatue)' and 70'F Note that the
annual number of degree days in"reaiessignificantly-
with an increase in zero-load tem''
perature for each locadon' Addi;ttt;il;;;"d"y data. are published
in reference [2]'
171. Erbs et al. [3] presented a metnoJi" "tti-it"
tf'e monthly and annual number of degree
davs based on monthty rn"un-u*Ui""t-i"lnperature data'
This method is useful in loca-
tions where degree-day data are unavailable'
The main use ot tn" O"gt"elJiy tetf'oO f to estimate the amount
of
fuel that will
be required to provide space hea ni{or a building' The amount
of energy required"E''
;;:;;i;:;;put.'tt'' ru"r 'li'itt,nent'
tr,'iv dividing it bv the average heating-
system efficiency and by the fuel heating value:
The average heating-system efficiency, 1*' is defined I. th: r?tio
of the thermal output
from the heating system divideo ufihi'n#ting nutu" ot the fuel
or energy input averaged
;;; ;; fi-#;6J or trr" unurvtit' not iottiftu"r t*naces this efficiencv
is
less than the
steadv-state value. cycting at parii;uJ'Jt'""t tl'" u*ount of heat
delivered to the build-
"fi:ffi;; ffi;iil: fl"'"' A-sHRAr 1r1 gi'"t equatio-ns to estimate
rl,l for various
172. types of heating systems that "t" "
i"""ilo"'dt"-ersizing of the heating-system capacity
and the amount of heat losr out the ductwork' The
heatilg-system average efficiency can
be estimated from
E"
'P
"tnH
CF ny
: 0.7791 + 0.1983RLC - 0'0711(RLCF
(17.e)
(17.10)
(17.11)
r7.r2)
240,*".0".,r,(DD),., (17.13)
(/,, a*,en - L, u""t . h, Il
rL, CFpt
l.h: T+;;
where q". is the steady-state or rated heating-system
efficiency without cycling' CF'1 is a
funcrion of the type of heating tyti"* "J
pi"ii rclad efficiency' and o' is the fraction of
173. heat loss from ducs. For exampte, the vatui for CFr,
for a natural-gas furnace with inter-
mittent ignition is given as
where
RCL:
aod Oo*ou, is the rated output of the heating
equipment' For fossil-fuel furnaces CF'1 is
alwavs less than 1.0. For electrlc furnu""t ""i
hiui"tt the value is equal to 1'0'*-"'i;rot;;;;q..-tri.zl,
trilsi' '"d-iri'sr'
we can obtain an expression.ror the
amount of tuel used to provide tp'il f'""tirrg that dep^ends on
the design
heat-loss'and
temDerature conditions, ttre numtei of deg.J" duy. riferenced
to the correct zero-load
#Hffi;.ffi;;;;;.;;;il;"v"'^ "fti'l'*v' and the hearins
varue of the ruel:
24(UA)"ff (DD)..,
F: :
'P 1l,tH
Pof V / Heotlng- ond Coolinqlood Colculotions in Buildings$2
Qou,p*
174. 15.2 suMMER DES',o't' co'{D',r'o'{s
The maximum heat gain
ever likely to be achieved in a
given building depends'on the out-
doorweatherffiiiil^t''r'"i"ati"""tp"t*u"'iu"iit..tiaitytttltt''uodthlus
aeeof
thespaceltd;#;;ili;u'"ait""t"amo"oiiinir'upt"rl2'Spaceoccupancva
nd
"tr,".
int"*"ri-"L.-"*'oi."r"*o in a later
seci'in in ,r,ir'"rtup,"t' fue will
focus on the
ffi #;;hffi fl"::uffi i}:;#;x*:::nil#'ilJ'#il:*:il:::
radiation is oflen treated
as clear-sky radlau^or
lationlevelsro,."r},i,ry"ooaidonsaregiveninChapter13.
Table r5.l lists some summer design
,..pJi"'"r"t i.r selected cilies around the
*o'ra' rn"t" it'i""i*Lt u'" ^"ut"'"d 't "i;;;
;t"ther weather slations The data
in raule rs'i rtaie been slatisticallv
*"rv'"[Jotl' ti-y"* p"rioo for which hourlv
176. Co[5
Prcvoillng
Wnd
Dieclion5%2.5%
5%CoL I
Locotlon 1%
2.5%
svdney, Auslrolio
Rio de Joneiro, Brozil
Edmonlon, Conoclo
Quebec, Conoclo
Poris, Fronce
Bomboy, lndio
Iokvo, JoPon
Meico CitY, Mexico .
aope Tor'n, Soulh Alnco
Kiev, Ukroine
Moscow, Russio
Slockholm, Sweden
Tunis, Iunisio
o€nver, USA
bs Angeles, USA
Miomi, USA
MinneoPolis, UsA
New York, USA
8el
941
85166
87 172
8el
182. 0.0
-1.8
-1.8
r0.2
canbeprogrammedonasmallcomputerolcalculatorforcalculationth
loughanydesired
number of harmonics'
Example 15'1 shows that sol-air temperatue variation for
a ho zontal surface can
be adequatety re"prlt"'i"i Uv
"
f"*i"r se;es with two harmonics' However' valiation of
," for vertical ""iu""'
diff"rs much more from pure sine-wave behavior than for
a hori-
zontal surface' In ii" "ut"
of
"ottf''
east' and w;st vertical surfaces' six or more harmon-
ics maY be needed'
cerre.aty]i".iooic heat transfer through a sunlit vertical wall is
small compared to
hear ffansfer rr,i|rgi-.
"
.*rit flat roof of th; same area. Thus. usually it is more impor-
183. tant to have *""'"'" .J"i' temperature information for a horizontal
surface than
for
vertical surfaces'
Followinj the same procedures described here' James C' Dunn-
developed
a
computef p."d;"";;;;;;i"J oirrnur sol-air remDerature variations
for horizontal
and vertica suiice. i-
"r"",
a^y.
"t
vrinneapolis for six different times of year [2]' Table
r5.s sfrows tris reluttfi. u fr"tirootuf surface. Constants in Eq.
(15.13) ar-e shgwn throush
t*otu,rno-
"t'Co"tuntsforthewinterdesigndayweredeterminedforclearDecem
-
ber-
Februarydayswhoseminimumlemperatureswereapproximately_20
"F.(_29"C).
constants for ;;.r--", a.G" a"y weie determined for clear June-
August days
whose
maximum temperatures were ipproximately 95 "F (35 "C)'
184. 15.1 PEP'ODIC HEAT OA//N fiHPOUGH WALIS AND ROOFS
Heattransferthroughwallsandroofscanbetreatedasdiurnalforpurpo
sesofdesigncal-
culations. There-firJirr" ."r-* ,"-perature becomes the external
thermal boundary
con-
dition and the-indoor temperaturi becomes the indoor
thermal boundary condition.
rn"re tounoury'JorrJitions'u." coupled to the solid material
through
the external and
i,t"rrur .onu""iiu-t"-tiai"tiue turt'ce fitm coefficients' Thus the
problem becomes one in
which the .otlo t'^t convective coefficients on both sides with
the
fluid temperatures
changing in u ai"rnJrn*"t' The most important assumptions to be
made
on the solid
wall or roof ari':*(f i.i"-J rr""i,ransfer is'by conduction only (or
pseudoconduction
if
natural convedio; and infrared radiation are present in
air cavities or in porous insula-
tion), (2) co,,tiil"sisionc"s between layers o1 material are
neglected'
185. and (3) air infil-
tration/exfiltrationthroughthewallorroofconstructionisnegligible.
t|El
ctloP 15 / lnstonloneous H6ot Goin
IABIE A.3E Thelmodynomlc Propedies of R-22 ot Sqturotion
(Engllsh Units)
Ttp
Liquin
De^tity
h,n41,
Sp- YoL
fi"b,
Entvlpy, Datun
-&"F, Batllbn
Entropy, DalM
-40'F, Rtulhtk .'R
L'4ud
ht
la,id
,100.
,95.
-90.