EFI AND EFFC OF FIN:EFFI OF FIN=actual heat transfr by fin(QFIN)

max het that would be tran if whole sur of the finis mainted at the base temp(Qmax)

;

for a fin which is infinetly long=√¿¿¿=√ k ACS

hPl2=1

ml

for a fin which is insulated at the tip=√Phk ACS (t o−ta ) tanh (ml )

h Pl ( to−t a )=tanh (ml)

ml ,where ml=√ hP

k ACS

.l=

√ h(2b+2 y)k b y

.l;

ml=√ 2hbk by

.l=√ 2hky

.l=√ 2hkyl

.l3 /2=√ 2hk AP

.l3 /2 were y.l= AP profile area of fin.thus fin effi is a fin of ml or

√ 2hk AP

.l3 /2 ;lc=l+y2

;eff fin =tanh ¿¿ ;Q=√ Phk ACS (t o−t a ) tanh ¿

het flow becomes Q=effi fin.√h p lC (t o−t a ); EFFECTIVENESS OF FIN: Q with fin

Q without fin=√Phk ACS (t o−ta )

h ACS (t o−t a )=

√ PKh ACS

; P

ACS=2(b+ y )

b . y=2y

;effictiv fin =√ 2kh y

rel btw effective and effi

efificy fin=√Phk ACS (t o−ta ) tanh (ml )

hPl (t o− ta ) ;;effect fin =√¿¿¿;

ε efctieffi

=pl

ACS;effective=eff.

PLACS

=EFF FIN.SUR AREAOF THE FIN

CROSS SECTION AREA OFTHE FIN

appli:1 economiser for steam power plant,2.convectors for steam and hot water v heating systems 3.radiators of automobiles4.air cooled engine cylinder heds 5.cooli8ng cooils and condensor coils in refrigerators and ac.6.small capacity compressors 7.electric motor bodies 8.trans formers and electronic equipments. ASSUMPTION RECTANGULAR:1.stedy state heat conduction 2. No heat gen within the fin 3.uni het transfer co effi(h) over the entire sur of fin 4.homogenous and isotro[pic fin materials 5.negli contact thermal resi 6.het cond 1D 7.neglibile radiation