Thermosyphons performance

Q

(8)

AT

Ztotal

Подпись: Q Подпись: AT Ztotal Подпись: (8)

The closed two-phase thermosyphon is an effective heat transfer device. The working principle can be easily explained as obtaining heat from the evaporator section by means of the evaporating mechanism and then releasing the heat out of the condenser section by means of the condensing phenomena. Because the latent heat of vaporization of the working fluid is relatively high, a large amount of heat can be transported through the thermosyphon.

where AT is the effective temperature difference between the heat source and the heat sink

(9)

Подпись:AT = Tso — Tsi — ATh

ATh = ‘ p

(Tp — Tv)x F

(10)

Подпись: (10)

Where Tso is the heat source temperature,(oC), Tsi is the heat sink temperature,(oC) and the mean temperature difference due to hydrostatic head, ATh is given by

Where the saturation temperature at the bottom of the pool, Tp is given by

(

dTs ^

Le x F x

p v

V

dH J

and

dT

s = Tsg

P_ _

P v

(11)

dH L

(12)

Tv — Tsi +

^ Z7 + Z8 + Z9 (t _ T )

so si

Z(

total

(13)

For the vapor temperature of the working fluid, Tv is determined from

Where Ztotal is the overall thermal resistance of the thermosyphons, it can be represented by the idealized network of thermal resistances Z1 to Z10 as shown in Figure 4.

Z1

M+MV

Подпись:

Z9

Подпись:

Z10

Подпись:

Z4

Подпись:

Z5

Подпись:

AV

Подпись:z1,z9 Convection z2,z8 Convection z3,z7 Internal resistance

of boiling & condensing z5 Pressure drop

z10 Thermal conduction

resistance axially z4,z6 Vapor-Liquid internal

Z3f

t Z3p ► Z2

Condensate

AV

Z10

Z1

Z9

Подпись: Z3f Подпись: Z9

Z6

Fig 4.Thermal resistance and their locations.