78

REVIEW OF BELLUZZO

Doc.

6

Review

of

G. BELLUZZO,

"Principles

of

Graphic Thermodynamics"

("Principi

di termodinamica grafica," Il

Nuovo

Cimento

8

(1904):

196-222, 241-263)

[Beiblätter

zu

den

Annalen

der

Physik

29

(1905):

235]

This article,

which

is

obviously meant

for

engineers,

is

divided

into

four sections, the first

of

which

treats

graphically

the

changes

of

state

of

arbitrary fluids.

Thus,

the familiar areal construction of

the

work

performed

(L)

by

the

body,

of

the

energy

increase

(AE),

and of

the heat absorbed

(G)

are

given

in the

pv-plane

in

§3,

while in

§4

and

§5

the increase of

entropy

for

an

arbitrary

change

of state

is

presented

as an area

with

G

and

T

(the

absolute

temperature), and

with

G

and

1/T,

respectively,

as

coordinates.

This is followed

by

the

theory

of cyclic

processes

and

the definition of

reversibility

and

irreversibility

of

the

processes.

A

process

is considered

to

be

reversible

or

irreversible, respectively,

depending

on

whether the

pressure

exerted

on

the fluid

during

the

process

does

or

does not equal

the

inner

pressure

of

the fluid; this stipulation,

which,

by

the

way,

is

irrelevant

for

what

follows,

does not

make

sense,

because

then the

principle

of the equality

of

action

and

reaction

would

not be

satisfied

in

any

irreversible

process.

The

second

section

of

the article contains the

application

of the

theory

to

ideal

gases;

examined

are

the

changes

of state at

constant volume,

constant

pressure,

and constant

temperature,

as

well

as

the

adiabatic

and

polytropic

change

of state.

The

last section deals with

the

efflux

of

gases through pipes;

the

hypothesis

of

Saint-Venant

and Wantzel

is

replaced

by

(already

known)

theoretical considerations.

The

third

and

fourth

sections of the article contain

the

theory

of

the saturated

and

the

superheated

water

vapor,

which

are

treated

in

a

corresponding

way,

with

special

consideration

given

to

the

theory

of the efflux

of water

vapor through

pipes

and to

the

theory

of

improving

the

efficiency of steam

engines

by

superheating.

For

the

equation

of state

for

water

vapor,

p(v+const.)

=

const.

T

is used,

following

Battelli

and

Tumlirz.

[1]

[2]