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Capitolo 5

Il bilancio entropico

66

GRYH

q

q LO ÀXVVR WHUPLFR

P

OD SRWHQ]D PHFFDQLFD H

m

˙

OD SRUWDWD FKH HYROYH QHO FLFOR 6RP

-

PDQGR PHPEUR D PHPEUR OH

L WHUPLQL UHODWLYL DOOH YDULD]LRQL GL HQHUJLD VL HOLGRQR H

FRPSOHVVLYDPHQWH VL RWWLHQH FKH

™

q

™

P

(5.5)

UHOD]LRQH FKH ULVXOWD GHO WXWWR DQDORJD D TXHOOD DSSHQD YLVWD SHU LO VLVWHPD FKLXVR

/R VWUHWWR OHJDPH HVLVWHQWH WUD OH GXH PRGDOLWj GL UHDOL]]D]LRQH GL XQD WUDVIRUPD]LRQH FL

-

FOLFD PHGLDQWH XQ VLVWHPD FKLXVR H PHGLDQWH XQD VXFFHVVLRQH GL VLVWHPL DSHUWL q UHVR DQFRU

SL HYLGHQWH LPPDJLQDQGR LQ HQWUDPEL L FDVL FKH OH WUDVIRUPD]LRQL VLDQR TXDVL

-s

WDWLFKH H FKH

VLD TXLQGL SRVVLELOH PRQLWRUDUQH OD SUHVVLRQH

p

H LO YROXPH VSHFL¿FR

v

, ottenendo un tracciato

FRPH TXHOOR GL )LJXUD

&RQVLGHUDQGR GDSSULPD LO FDVR GHO VLVWHPD FKLXVR H GHWWD

m

OD VXD PDVVD VL q YLVWR FKH

LQ DVVHQ]D GL DWWULWR ULVXOWD

dL__

m

=

p dv

(5.6)

,QWHJUDQGR VXOO¶LQWHUR FLFOR VL RWWLHQH

™

L

____

m

=

p dv

SHU FXL O¶DUHD UDFFKLXVD GDOOD WUDVIRUPD]LRQH FLFOLFD QHOOH FRRUGLQDWH

p – v

GL )LJXUD UDS

-

SUHVHQWD LO ODYRUR FRPSOHVVLYDPHQWH HVSOHWDWR QHO FLFOR SHU XQLWj GL PDVVD GHO VLVWHPD FKH

FRPSLH OD WUDVIRUPD]LRQH 7DOH ODYRUR ULVXOWD SRVLWLYR R QHJDWLYR D VHFRQGD FKH LO FLFOR YHQJD

SHUFRUVR LQ VHQVR RUDULR H DQWLRUDULR QHO SULPR FDVR VL SDUOHUj GL

ciclo diretto

, nel secondo

di

ciclo inverso

.

p

v

1

2

3

4

5

Figura 5.5

'¶DOWUD SDUWH WUDWWDQGRVL GL XQD WUDVIRUPD]LRQH FLFOLFD YDOH OD

H TXLQGL WDOH DUHD UDS

-

SUHVHQWD DQFKH LO FDORUH FRPSOHVVLYDPHQWH VFDPELDWR VHPSUH SHU XQLWj GL PDVVD

m

del sistema

6H LQYHFH VL FRQVLGHUD LO FLFOR IRUPDWR GD XQD VXFFHVVLRQH GL VLVWHPL FRQ GHÀXVVR DSSOLFDQ

-

GR O¶HTXD]LRQH GL %HUQRXOOL JHQHUDOL]]DWD LQ DVVHQ]D GL DWWULWR VL RWWLHQH FKH

0 =

m

˙

œ

v dp

+

P

GD FXL SHU O¶LQWHUR FLFOR

™ 3

___

m

˙

= –

v dp

(5.9)