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Capitolo 5

Il bilancio entropico

&RQVLGHUDQGR RUD O¶LQVLHPH GHOOH GXH PDFFKLQH UDFFKLXVH GDOOD OLQHD WUDWWHJJLDWD LQ )L

-

JXUD E HVVR UDSSUHVHQWD D VXD YROWD XQD PDFFKLQD & OD TXDOH SUHOHYD GDOOD VRUJHQWH D

T

b

OD TXDQWLWj GL FDORUH

|

q

C

,

b

| = |

q

F

,

b

_

e contemporaneamente cede alla sorgente a

T

a

OD TXDQWLWj GL FDORUH

|

q

C

,

a

| = [|

q

F

,

b

| + |

q

M,a

|] – |

q

M,a

|

= |

q

F

,

b

_

3RLFKp OH LQWHUD]LRQL FRQ OH GXH VRUJHQWL UDSSUHVHQWDQR JOL XQLFL HIIHWWL GHOOD PDFFKLQD

FLFOLFD FRPSOHVVLYD H WDOL LQWHUD]LRQL VRQR GL SDUL HQWLWj VL SXz DIIHUPDUH FKH OD YLROD]LRQH

GHOO¶HQXQFLDWR GL .HOYLQ ± 3ODQFN FRPSRUWD OD YLROD]LRQH GHOO¶HQXQFLDWR GL &ODXVLXV

F

M

T

a

T

b

q

F,b

q

F,b

+ q

M,a

q

M,a

F

M

T

a

T

b

q

F,b

q

F,b

q

M,a

q

M,a

q

M,a

P = q

M,a

a)

b)

Figura 5.10

6L VXSSRQJD RUD FKH FRPH LQGLFDWR LQ )LJXUD D VLD OD PDFFKLQD IULJRULIHUD DG RSHUDUH LQ

YLROD]LRQH GHOO¶HQXQFLDWR GL &ODXVLXV FLRq DYHQGR FRPH XQLFR ULVXOWDWR LO SUHOLHYR GL XQ ÀXVVR

termico

q

F

,

b

GDOOD VRUJHQWH D EDVVD WHPSHUDWXUD H OD IRUQLWXUD GL XQ SDUL ÀXVVR WHUPLFR _

q

F

,

a

| = |

q

F

,

b

|

DOOD VRUJHQWH DG DOWD WHPSHUDWXUD 3DVVDQGR DO PRWRUH WHUPLFR VL VXSSRQJD FKH HVVR IXQ]LRQL LQ

DFFRUGR FRQ O¶HQXQFLDWR GL .HOYLQ ± 3ODQFN FLRq FKH SUHOHYL XQ ÀXVVR WHUPLFR

q

M,a

dalla sorgen-

WH DG DOWD WHPSHUDWXUD H OR WUDVIRUPL VROR LQ SDUWH LQ SRWHQ]D PHFFDQLFD

P

, cedendo la rimanente

parte

q

M,b

alla sorgente a bassa temperatura. Con un opportuno dimensionamento del motore si

SXz DOORUD IDU Vu FKH _

q

F

,

b

| = |

q

M,a

_ H LQ WDO PRGR FRQVLGHUDQGR OD PDFFKLQD FLFOLFD FRPSOHVVLYD

UDFFKLXVD GDOOD OLQHD WUDWWHJJLDWD GL )LJXUD E VL YHGH FKH HVVD RSHUD SURGXFHQGR OD SRWHQ]D

P

HG LQWHUDJHQGR VROR FRQ OD VRUJHQWH DG DOWD WHPSHUDWXUD GDWR FKH FRQ TXHOOD D EDVVD WHPSHUD

-

WXUD O¶DVVRUELPHQWR H OD FHVVLRQH GL FDORUH VL HOLGRQR WUD ORUR &Lz FRQ¿JXUD XQD SDOHVH YLROD]LR

-

QH GHOO¶HQXQFLDWR GL .HOYLQ ± 3ODQFN FKH GLVFHQGH GDOOD YLROD]LRQH GHOO¶HQXQFLDWR GL &ODXVLXV

F

M

T

a

T

b

q

F,b

q

F,b

q

M,b

q

M,b

q

M,a

= q

F,b

F

M

T

a

T

b

q

F,b

q

F,b

q

F,b

q

F,b

a)

b)

P

P

Figura 5.11