Measurement Techniques, Vol. 39. No. 5, 1996

THERMAL CAPACITY OF AQUEOUS AEROZINE SOLUTIONS AS A F U N C T I O N O F T E M P E R A T U R E

AND PRESSURE

M. M. Safarov, M. A. Zaripova, and F. S. Radzhabov

UDC 536.2.088

The results are given of an experimental study of the thermal capacity of aqueous aerozine solutions in the temperature range 313-450 K, and pressure range 0.101-49.1 MPa. Generalized equations are obtained for calculating the thermal capacities of these solutions.

Aerozine has found wide application in various branches of industry: in the production of porophores and polymers, for corrosion protection, as a fuel for jet-propulsion motors in rockets, in electrochemical generators, etc. The dissolving of aerozine in water is an exothermic process [1]. It mixes with water in any proportions. The compound with 50% (mol) of hydrazine in 50% (mol) water has been named aerozine-50. An experimental unit has been developed for measuring the thermal capacity of the solutions, in the temperature range 293-473 K, by a monotonic heating method. The device contains a measuring unit, graph plotter, Dewar flask with melting ice, high pressure clamped vessel, type MP-2500 loaded piston manometer and electromeasuring instruments [2, 3]. For verifying the correctness of the experiments, control measurements were carried out with toluol, n-hexane and kerosene. The specific thermal capacity of control specimens at atmospheric pressure was measured in the temperature range 273-373 K. The results of the control thermal capacity measurement.~ of the listed materials agreed within 2% with the literature data. The overall relative error of the experimental data at confidence level 0.95 did not exceed 3.0% [2]. In the experimental unit described, the first measurements have ben made of the specific thermal capacity of aqueous aerozine solutions in the temperature range 313-450 K, and pressure range 0.101-49.1 MPa. The measurements were made along isobars with pressure steps of 4.9-9.8 MPa. The variation of specific thermal capacity of the aqueous aerozine solutions as a function of temperature at atmospheric pressure is shown in Fig. 1 and in Tables 1-4. From Fig. 1 and these tables, the thermal capacity of the solutions studied is increased with rise in temperature and concentration. The thermal capacity of the solutions studied is increased with temperature rise over the whole pressure range. With increase in pressure, cp is reduced. As the density of the solutions studied is increased with a pressure rise, and is decreased by a temperature rise, the specific thermal capacity is increased with a temperature rise, and decreased by a pressure rise. On raising the temperature, the pressure influence on the specific thermal capacity of the aqueous aerozine solution is increased. For example, if the pressure rise to 49.0 MPa at temperature 293 K increases the thermal capacity of the aqueous aerozine solution (70% aerozine + 30% H20) by 2.2%, at temperature 473 K, this variation is 5.8%. The specific thermal capacity of the solutions studied increases linearly with increase in the water concentration. We suppose that the structure of water is of special significance in studying the properties of water and of aqueous solutions which are associated with transport phenomena. This is because the structure determines the conditions of transnational movement of the liquid. Water is a strongly associated liquid, and has a comparatively high boiling point, which points to the presence of appreciable intermolecular forces in the liquid state, which hamper the transition to the gaseous phase. The specific thermal capacity is an additive function of the mass contributions of the constituent components in the specimens. On this basis, the specific thermal capacity was calculated from the equation cp= ~~"l ci,,i,

Translated from Izmeritel'naya Tekhnika, No. 5, pp. 46-48, May, 1996. 540

0543-1972/96/3905-0540515.00

~

Plenum Publishing Corporation

(I)

TABLE I Isobaric thermalcapacityCp.T"J/(kg.K)of aqueousaerozinr solutions

T. K O,lOl

293 303 .'113 323 333 353 363 373

,3O48 3065 3084 31QI

3t2,0

t

,.9,

I

fr;.,

30'23 304~} ')055 ,3070 3083

(90~ aerozine+ 10% H20) a! pressurep, m MPa I 117 I I.q6 1 24.7 t

3021 "~,(136 3O,5"I

:',;l 16 30.'m :~4,4

3071

3117 3130

3077 3091 ~I~ 3164

31"~

3 h37

~9,.0

Cpr

300,5

3010 .W3i24 3(337 3049 3061 3C#4 34)87 31(k2 311117

3099

3115 3128

0

0

/

~,

I

,9.,, ~07

~,

0

I

4',.0!

:1002 ,~02G

3{',Lg 3055 3067 30~q LtO94 3108

,

Jl(kg.k).

29 i;

3038 3050 3060 .'~7,1 :~083 .'~O7

302~ 303U 3050 3O62 3073 .30~7

:299~ ;~tl 2

:g0',"2_ .~3"2 :~4LJ 30,-34 ;~r

.~).77

:

9

3930

g

7

373o

3530

5

3330

--.m

~

4 / I' - " :_- - I

n

31 n

-

3130

313

333

3-';3

3

T, K

Fig. 1. Dependence of the specific thermal capacity of aqueous aerozine solutions on temperature at atmospheric pressure: 1) 90% aerozine + 10% H20; 2) 80% aerozine + 20 H 2 0 % ; 3) 70% aerozine + 30% H20; 4) 60% aerozine + 40% H20; 5) 50% aerozine + 50% H20; 6) 40% aerozine + 60% H20; 7) 30% aerozine + 70% H20; 8) 20% aerozine + 80% H20; 9) 10% aerozine + 90% H20. where c i and rni are the specific thermal capacity and mass contribution of the i-th component; and n is the number of constituent components. The experimental specific thermal capacity values agree sufficiently well with the calculated values. For processing and pooling the experimental data, as a function of temperature at atmospheric pressure, we used the relationship [2] c,/opt= I (T, T 1).

(2)

where cp and cpt are the specific thermal capacities at temperatures T and T l = 293 K. Relation (2) is well fulfilled for aqueous aerozine solutions, i.e.. the experimental data for the specific thermal capacity are well fitted by a straight line, defined by the equation cp=(O.16T /Tt-1-O,84)cpl.

(3)

An analysis of the cpt values for aerozine aqueous solutions showed that they are functions of the water molar fraction: c o t = 12.4nlt.~o-1-2941.

(4)

541

TABLE2 [soOarlc thermal capacity Cp.T, l/(Kg K) of aqueous aerozme solutions (70q~ aerozme + 30% H20) at pressure p. m MPa 9.81 1'I,7 t9.ti '.2'4 7 29.4 ~

T, K

293 1303 31~ 32,3 333 34,3 353 363 373

0.101

4,91

3289 3299 33'14 3329 3344 336O

3285 3296

3,276

3258 32181 3292 3303 3314 3325 3,338 33~ 3363

32@9 3,301 3310 &q~2 ,,3034 3348 3,.302 3,371

33'21 .3,331 3344 3057 3369 33~

3258

3,269

3.262

3280 32910

327',2

3.300 3312 3324 3338 3352

32.9*3

32~3 3316 3329 334,3

39,34

49,01 A2U6 :k227 3,242 325O 326~ 327,1

3234 .].2a40 ,',;,250 32.58 3269 7~811 329,4 3307 332,0

3245 3"2'57 3267 .3:2,76 3286 32~7 3308 3,320 3332

3281 3296 "~308

TABLE 3 Isobaric thermal capacity Cp,T, J/(kg.K) of aqueous aerozme solutions r. K 0,10t

I

3545

293 303 313 3,23 333 343 353 363 373

4.91

[

3.544 3563 3562 3571 ,35,79 3589 3599 36O8 36.16

3551

3.552 3574 360O

9.81

(50% aerozme + 50% H20) at pressure p. m MPa [ 14.7 [ 19.6 [ 24,7 [

353:1 3541 355 I 3659 3667 3677 31587 36~0 3603

.3605 35'14 3523 3531 3539 3550 3561 3576 358,7

3520 3530 364.0 3549 3558 3567 3578 3589 3598

34.ck5 350"5 3514 35Z~ 36.31 3541 35,'53 3565 3578

29.43

[

39.3,1

346fi 347"~ ?,48.; 349.0 3493 3513 352"7 .3640 3553

3588 :HO.8 3 fi,0.~ 3516 .3,524 35,3,4 3544 3556 3567

[

49.01

3446

3457

34.7O 3478 34,88 360~ 3494 352"6 3540

TABLE 4

r. K 0,I01 293 30,3 313 323 333 343 353 363 373

[

4,91

4,057 4054

4(164 4056

4,068 4O63 4073

4069 4ff72 4,074

408O

4~'78 408'I 4(~4 4J088

I

Isobaric thermal capacity Cp,T,J/(kg-K) of aqueous aerozine solutions (10% aerozine + 90% H20) at pressure p, in MPa 9,81 [ 14.7 I 19.6 - I 24.7 } 20.43 4635 4046 406,1

~999 4.003 40'09

432.4 4030 r 4040 4~44

4057 4062 4666 4076 4076

4013

401~ 4~26 4,034 4.947 4,O56

404,9 4~r.56 4062 4066

39~3 399:1 3997 4009. 4007 4014 4@26 4037 404"6

"J:J74 3~1 39$9 3993 400'7 4O25 4O36

I

39,34

49.0i

3~0 3938 3~48 3952 3957 ."H)75 3992 4006 41319

39~5 3915 3928 3934 3!N t 3956 3967 3985 4001

T a k i n g account o f (4), w e obtain for calculating the specific t h e r m a l capacity o f aqueous a e r o z i n e solutions (in J/(kg-K)), as a function t e m p e r a t u r e at a t m o s p h e r i c pressure

cp= (0,16T "T t'q-0,84 ) ( 12,4 nB.o 4-2941 ).

(5)

F r o m (5), the specific t h e r m a l capacity o f aqueous aerozine solutions c a n be calculated as a f u n c t i o n o f t e m p e r a t u r e at a t m o s p h e r i c pressure. F o r this, it is necessary to k n o w only the value of the w a t e r m o l a r fraction. F o r obtaining a c o m p u t a t i o n a l equation for the t h e r m a l capacity o f a q u e o u s aerozine solutions at h i g h state p a r a m e t e r s , we have p r o c e s s e d the e x p e r i m e n t a l data in the f o r m o f the following functional d e p e n d e n c e [2]:

c~

=!

( o'7" /

\Px:Tt I "

(6)

w h e r e Cp. T is the t h e r m a l capacity o f aqueous aerozine solutions at p r e s s u r e p and t e m p e r a t u r e T; and CptTl is the t h e r m a l capacity at Px = 0.101 M P a and T I = 293 K. T h e practical usefulness o f Eq. (6) for the 70% aerozine + 30% H 2 0 solution is s h o w n in Fig. 2. H e r e , it m a y be seen that the e x p e r i m e n t a l points lie well along the individual isobars. 542

Fp r/Cr,,f k 1.02

z.o]

;L ~.

I .no

~,

0,99

i [

0,98

. ;

;

:

1O0

8~

.=

. . . . .

200

300

400 (p,q'J/(p /T, l

Fig. 2. Dependence on pressure of the relative specific thermal capacity of the solution 70% aerozine + 30% H20. I) 4.9I; 2) 9.81; 3) 14.7; 4) 19.61; 5) 24.7; 6) 29.43; 7) 39.34; 8) 49.01 MPa.

Additional experimental data given in Fig. 2 were processed in the form of the functional dependence [2]

Cm,r , .U

cp,.r, /1

..Ilp/T)I(pt/Tt)It

'

where (cp,rCcp~T~) 1 = 1.0; and [(pl13/(Pl/T])]; is the value of (p/73/(PtTt) at (cp,14Cpr 7t)1" The probability of relation (7) for aqueous aerozine solutions showed that the experimental data lie along a general curve. The equation of the this curve takes the form

ce,l'. 'c ~,.r,

(cp,rlcp,.r,)l

=0,273 { I(P;T,/(P./Tt)I

t(P/T)/(Pt/Tx)}=

}"- --0,694 { [(PlT)I(PtlTt)I I(P/T)/(PdT=)It j +1,42.

(8)

From an analysis of the quantities { [(plT)/(Pt:Tt)I } and Cp=.Ti, it follows that they are functions of the pressure, and of [ (p/T)/(Pt '.TO It molar fractions of aerozine n a and water n112o. These functions are defined by the equations [ (p/T

) / (Pti Tt ) l

I(PT)I(PxlTt)Ip,

P

=0,9?.3 ~

--t-0,51;

[ (p; T ) i (Px 'Tx ) ]~,=264,4--0,9 lnl./,:o , cpt.T = 12,61na.-I.-l185.

(9) (10) (11)

Taking account of (9)-(11), we have, from Eq. (8), for cp, T, in J/(kg-K):

cp.r= ~2,29.10-ap s[ T(O.23p!ps-t-9,51 ) (2~4,4---0,94n~c,o ]-: --2,01.1O- 3 Pl T(O,23p/p,.-1-0 ,51 ) X

(12)

X (264,4--0,94na..o) 1-~ -4-1,42}(12,8In,q-4185). From (12), the thermal capacity of aqueous aerozine solutions in the temperature range 293-550 K, and pressure range 4.91-49.1 MPa can be calculated with an accuracy of 5%.

543

REFERENCES 1.

2. .

544

A. P. Grekov and V. Ya. Veselov, The Physical Chemistry of Hydrazine [in Russian], Naukova Dumka, Kiev (1979). M. M. Safarov, "Thermophysical properties of simple ethers and aqueous hydrazone solutions as a function of temperature and pressure," Dissertation for degree of doctor of technical science, Dushanbe (1993). M. M. Safarov and A. I. Bogdanov, lzmer. Tekh., No. 2, 42 (1995).