105-March-2014 BE-RF-PM

Calculations of the heat transfer coefficients for the

TM0

205-March-2014 BE-RF-PM

SAS : Heat Transfer Coefficient due to Convection

SAS 2

3)(

v

LTTgGr as

L

NATURAL-FREE CONVECTION

Whereg = gravitational acceleration m/s²β = coefficient of the volume expansion, ρω-ρ/ρ(Τω-Τ)Ts = temperature of the surface, °CTω= temperature of the fluid sufficiently far from the surface, °CLc = characteristic length of the geometry, m v = kinematic viscosity m²/s

AIR properties k 0.0257 W/mK

ρ 1.205 kg/m3

v 1.5E-05 m2/s

µ 1.8E-05 Cp 1005 J/kgKPr 0.7 T∞ 20 °C

u∞ (Nominal value) 0.7 m/s

nLGrC

k

hLcNu Pr)(

For an horizontal plate the formula above is:

3/1)(15.0 LRaNu

RaGrL Pr

for ]1010[ 117 LRa

FORCED CONVECTION

3/18.0 PrRe037.0 Lk

hLcNu 711 10Re105 Lxwith 60Re6.0 L

For turbulent flow over the entire plate :

L= 2 m

305-March-2014 3BE-RF-PM

2

27/816/9

6/1

Pr)/559.0(1

387.060.0

RaNuD

Pr)(

2

3

v

DTTgRa as

NATURAL-FREE CONVECTION

1210Ra

Whereg = gravitational acceleration m/s²β = coefficient of the volume expansion, ρω-ρ/ρ(Τω-Τ)Ts = temperature of the surface, °CTω= temperature of the fluid sufficiently far from the surface, °CLc = characteristic length of the geometry, m v = kinematic viscosity m²/s

FORCED CONVECTION

AIR properties k 0.0257 W/mK

ρ 1.205 kg/m3

v 1.5E-05 m2/s

µ 1.8E-05 Cp 1005 J/kgKPr 0.7 T∞ 20 °C

u∞ (Nominal value) 0.7 m/s

PETS : Heat Transfer Coefficient due to Convection

3/18.0 PrRe037.0 Lk

hLcNu 711 10Re105 Lxwith 60Re6.0 L

2 x

2 m

405-March-2014 BE-RF-PM

SAS, PETS: Mixed Convection -Values

4

nnnnaturalforced

combinedNuNuNu /1)(

Nu natural Nu forced Nu mixed h

SAS 3.51e2 1.14e2 3.52e2 5.09

PETS 19.3 3.09e2 3.09e2 3.97

505-March-2014 BE-RF-PM

SAS, PETS : Heat transfer coefficient due to Radiation

5

))(( 22surssurs TTTTh

Emissivity ε 1

Stefan-Boltzmann constant σ 5.67E-08 W m-2 K-4

Module surface temperature Ts

30 °C303 K

Surrounding temperature (wall) Tsur

20 40 °C293 313 K

Heat transfer coefficient hr 6.0 6.6 W/(m2K)