Ind. Eng. Chem. Fundam. 1980, 79, 295-300
295
Thermal Conductivities of Liquid Hydrocarbons and Their Binary Mixtures Kojlro Ogiwara' Department of Industrial Chemistry, Akita Technical College, Akita 0 11, Japan
Yasuhlko Aral Department of Chemical Engineering, Kyushu University, Fukuoka 8 12, Japan
Shoraburo Salto Department of Chemical Engineering, Tohoku University, Sendai 980, Japan
The thermal conductivities of several pure liquid hydrocarbons (n-paraff ins and aromatics) and their binary mixtures were measured by using a relative horizontal parallel-plate method (steady-state type) at temperatures from 20 to 70 O C at atmospheric pressure. A correlation model was proposed to represent the thermal conductivities of liquids and their mixtures on the basis of the hole theory concept and the lattice model of Horrocks and McLaughlin. An empirical parameter was introduced to obtain the displacement of a molecule required to transfer its energy to a neighboring molecule. The reduced values of the LennardJones potential parameters and the empirical parameter, which were needed in the calculations of thermal conductivities, could be correlated by quadratic functions
of Pitzer's acentric factor.
Introduction The thermal conductivities of liquids are important as fundamental data in the engineering calculations of heat transfer rates. Therefore, the thermal conductivities of many substances have been measured by several workers and are compiled by Touloukian et al. (1970). Recently, Makita (1975) has reviewed the data sources and calculation methods of the thermal conductivities. As shown in the literature (Touloukian et al., 1970; Makita, 1975), there are few data for liquid mixtures although a number of thermal conductivity data have been reported for pure liquids. Although various methods are available for the experimental determination of thermal conductivities (Tsederberg, 1965; Tye, 1969), discrepancies among the data reported by different workers are not negligible, because of experimental difficulties. In the present study, by using a relative horizontal parallel-plate method (steady-state type), the thermal conductivities of seven liquid hydrocarbons (n-heptane, n-octane, n-nonane, n-decane, benzene, toluene, and p xylene) and three binary mixtures (n-heptane-n-decane, benzene-n-heptane, and benzene-p-xylene) were measured a t temperatures from 20 to 70 "C a t atmospheric pressure. The thermal conductivity data obtained in this work were compared with the literature values for several pure hydrocarbons. Although several calculation methods for thermal conductivities of liquids and their mixtures have been published by several investigators (Filippov, 1955; Jamieson and Hastings, 1969; Li, 1976; Losenicky, 1968), they are essentially empirical. Semitheoretical approaches based on the molecular model of Horrocks and McLaughlin (1960) have also been reported by Gaitonde et al. (1978) and Saksena and Harminder (1974). However, they are not sufficient for extending the model to mixtures. In the present study, therefore, a correlation model has been 0196-4313/80/1019-0295$01 .OO/O
proposed following the concept of Horrocks and McLaughlin (1960) in conjunction with the hole theory of liquid structure. In the present model, a new empirical parameter is introduced to obtain the displacement of a molecule necessary for transfer of its energy to a neighboring molecule. Experimental Section Experimental Apparatus. The apparatus used in the present work was similar to that of Nukiyama and Yoshizawa (1934). As shown in Figure 1, the present apparatus is of a relative horizontal parallel-plate, steady-state type. A liquid sample, L, was held between the standard glass plates, G, the thermal conductivity of which was calibrated with distilled water. The dimensions of both glass plates were 260 X 260 X 10 mm. Copper-constantan thermocouples (about 0.07 mm in diameter) were provided to measure the temperature gradients across the liquid layer and the standard glass plates. These thermocouples were fastened to both sides of the glass plates with a small quantity of epoxy adhesive and then covered with thin aluminum foil (0.01 mm in thickness and 5 mm in width). Although it is difficult to determine exactly the distances between the thermocouples attached on the two glass plates and to estimate heat loss along the wires, these uncertainties can be properly allowed for by calibration with water. As shown in Figure 1, three thermocouples were used in order to ascertain whether the temperature on each surface of the glass plates was uniform. The electromotive force was measured by a high-precision potentiometer (Shimazu Model PD 20). The distance between the glass plates (Le., the thickness of the liquid sample) was 4.84 mm and the area of the liquid sample was 220 X 220 mm. By circulating water of a constant temperature (controlled within fO.O1 "C)through jackets, J, a temperature gradient was established in the test fluid around the de0 1980 American
Chemical Society
286
Ind. Eng. Chem. Fundam., Vol.
19, No. 3, 1980
Table I. Smoothed Experimental Values of Thermal Conductivity of Pure Hydrocarbons, h X
lo4,cal/cm s "C
temperature, "C
a
liquid
20
30
40
50
60
70
benzene toluene p-xylene n-heptane n-octane n-nonane n-decane
3.61 3.22 3.14 3.07 3.10 3.21 3.30
3.55 3.17 3.09 3.03 3.06 3.18 3.26
3.49 3.12 3.05 2.99 3.03 3.14 3.22
3.42 3.07 3.00 2.95 3.00 3.10 3.18
3.36a 3.03 2.96 2.91 2.97 3.06 3.14
3.30a 2.98 2.91 2.8Ta 2.94 3.03 3.11
lo4
A X
3.73 3.31 3.23 3.15 3.16 3.29 3.38
B x
max dev, %
lo7
-6.11 -4.71 -4.54 -3.98 -3.17 -3.78 -3.92
0.3 0.3 0.7 0.3 0.9 0.7 0.6
Extrapolated values. key
-
36
I
I
I
'
0 Davis e t a l (1971)
U
z 3 4 -
1
J .
I
t
I
A
Thermocouple
Figure 1. Schematic diagram of the experimental apparatus: A, constant-temperature air bath; C, copper plate; G, standard glass plate; I, insulating material; J, jacket; L, liquid layer; LI, liquid inlet; P, circulating pump; S, silicone rubber; W, constant-temperature water bath.
sired experimental temperature. High-temperature water was circulated through the upper jacket, and heat flux was directed downward in order to minimize heat transfer by convection. A copper plate (310 X 310 X 10 mm), C, was held between each glass plate and the jacket to make the surface temperature of the glass plate uniform. Silicone rubber (1 mm in thickness), S, was interposed between each glass plate and the adjacent copper plate to avoid contact of the plates. In order to eliminate heat loss, the apparatus was covered with insulation material (formed polystyrene) and was placed in an air bath which was controlled a t the experimental temperature. Experimental Procedure. Liquid samples were prepared by boiling to evolve gas and then introduced into the apparatus through the L-shaped glass tube, LI. About 2 h was required to reach a steady thermal state, since water of a constant temperature was circulated. The fluctuation of temperature of each point was observed to be within fO.O1 "C. A t this steady-state condition, the heat flux, q , is represented by = (hO/dO)(tl - t 2 ) = (X/d)(tz - t 3 ) = ( X O / d O ) ( t 3 - t4) (1)
where A,, and do are the thermal conductivity and thickness of the standard glass plate, and X and d are the thermal conductivity and thickness of the liquid layer, respectively. tl through t 4 denote the surface temperature, as shown in Figure 1. From eq 1, the thermal conductivity of a liquid sample can easily be obtained as = XO(d/dO)(tl - t z ) / ( t : !- t 3 ) (2) By making sure that tl - t 2= t3 - t4,it was ascertained that the heat loss from each layer was sufficiently eliminated. In the present work, the temperature gradients were set up when tl - t 2 (or t 3 - t4) = 6.3 "C and t2- t 3 = 1.6 "C. Thermal Conductivity of the Standard Glass Plate. The thermal conductivity of the glass plate used as a standard substance was calibrated with distilled water. Its thermal conductivity has been determined by several investigators (Challoner and Powell, 1957; Le Neindre et al.,
nvesli~tors present study
exptl method PSR P SA
0 ChallonerB Powell (1957)
-
WTA A HorrocksBMcLaughlin (1963) WTA V Rledel (1951a) CSA
Ind. Eng. Chem. Fundam., Vol. 19, No. 3, 1980
r
3'7 3.5
0
3.6
297
exptl value a t 5 0 4 ' C calcd value by e q 2 4 calcd value k,2. 0
b 2 2.9 molefraction 01 n-heptane
x
(-)
Figure 5. Thermal conductivity of n-heptane-n-decane binary mixture.
3.0
38 exptl value at 2 5 I 'C
0
calcd value by e q 2 4 calcd value kl2 .0
Figure 3. Thermal conductivity of pure hydrocarbons. 1 investigators A lpresen! study
method
PSR
2 8
00
02 06 06 08 moletraction of benzene X ( - )
I O
Figure 6. Thermal conductivity of benzene-n-heptane binary mixture. 2820
30
40
t I'C)
50
60
70
38
Figure 4. Comparison of the present work with other investigators for n-decane: method, see Figure 2.
0
Table 11. Thermal Conductivity and Density of n-Heptane-n-Decane Binary Mixtures
Z x io4. n-heptane mole fraction 0.00 0.25 0.50 0.75 1.00
cd/cm s ' C 25.5 50.4 "C "C 3.25 3.18 3.23 3.16 3.19 3.11 3.16 3.06 3.04 2.94
k,2=-0 059
*
25.5
benzene mole fraction
0.00 0.20 0.40 0.60 0.80 1.00
32
50.4
"C
"C
0.7269 0.7165 0.7059 0.6935 0.6789
0.7078 0.6971 0.6860 0.6729 0.6576
Table 111. Thermal Conductivity and Density of Benzene-n-Heptane Binary Mixtures
104, cal/cm s " C 25.1 45.1
3
'0
F, g/mL
rx
exptl value at 25 1'C
28
00
25.1
45.1
"C
"C
"C
"C
3.05 3.07 3.12 3.17 3.35 3.57
2.98 3.00 3.05 3.08 3.26 3.45
0.6795 0.7024 0.7314 0.7677 0.8133 0.8739
0.6620 0.6852 0.7135 0.7485 0.7932 0.8526
In Figure 4, comparisons between the present data and the literature values are illustrated for n-decane as an example. As seen in this figure, the present data agree with the recommended values reported by Touloukian et al. (1970) within the experimental accuracy. However, the data of Briggs (1957) and Mallan et al. (1972) deviate from the present work by about 4%. For other normal paraffins (C7-C9), similar deviations were found. The values of thermal conductivities for three binary mixtures are presented in Tables 11-IV and in Figures 5-7. The densities of the mixtures were measured by use of a pycnometer and the results are shown in Tables 11-IV, because the density data were required in the proposed model for correlating the thermal conductivities of the mixture.
I O (
6
)
Figure 7. Thermal conductivity of benzene-p-xylene binary mixture. Table IV. Thermal Conductivity and Density of Benzene-p-Xylene Binary Mixtures
T, x
P", g/mL
02 0 4 06 08 malefraction of benzene X
benzene mole fraction
0.00 0.20 0.40 0.60 0.80 1.00
io4,
cal/cm s " C 25.1 45.1
P", g/mL 25.1
45.1
"C
"C
"C
"C
3.12 3.13 3.16 3.21 3.31 3.57
3.00 3.01 3.03 3.11 3.21 3.45
0.8571 0.8582 0.8604 0.8634 0.8675 0.8739
0.8397 0.8403 0.8419 0.8442 0.8474 0.8526
Correlation of Thermal Conductivities of Liquids a n d Their Binary Mixtures The study of Horrocks and McLaughlin (1960), based on a lattice structure for the liquid, shows that the thermal conductivity of a liquid is caused mainly by the vibrations of molecules. There is also the convective contribution of molecules to the thermal conductivity, but it is found to be usually less than 1% of the total value. Thus, the calculation of Horrocks and McLaughlin (1960) for liquid argon a t its normal boiling point shows = 9.28 X lo3 and = 54 erg cm-' s-l deg-'. They proposed the following equation to predict the thermal conductivity of liquids X
N
= 2nv1C,/NA
(5)
where C, is the constant-volume heat capacity, v is the
298
Ind. Eng. Chem. Fundarn., Vol. 19, No. 3, 1980 26 1 : benzene
3 : n-pentane
" 1 4
Figure 8. Correlation between constant-volume heat capacity of liquids and number of atoms.
frequency of molecular vibration, n is the number of molecules per unit area, NA is Avogadro's number, and 1 is the distance between crystal lattice planes normal to the energy gradient. By using eq 5 , Saksena and Harminder (1974) calculated the thermal conductivities of liquid mixtures. In their studies, the constant-volume heat capacity per molecule was taken as 312 where 12 is Boltzmann's constant. However, this is hardly to be expected for polyatomic molecules. In the present study, therefore, C, values of liquids were correlated with the number of atoms involved in a molecule. Further, the value of v of a molecule in its liquid state was evaluated based on the hole theory. By using these estimates of C, and v, the thermal conductivities of liquids were correlated and the results were compared with the experimental values. Working Equation Based on t h e Hole Theory. When the face-centered cubic lattice is assumed for the liquid structure, the value of 1 is replaced by 2'I2a/2 where a is the distance between a molecule and its nearest neighbor. Further, the following expression is derived by assuming the presence of holes
n = (Vo/V)/a2 (6) where Vo denotes solid molar volume and V is liquid molar volume. Therefore, the working equation for correlating thermal conductivities can be derived from eq 5 . = fi(Vo/V)C,V/aNA
(7)
where U
= 21/6(v~/N~)1'3
(8)
Constant-Volume Heat Capacity C, of Liquids. The constant-volume heat capacity C, of liquid is contributed by several terms representing translation, vibration, and rotation. Furthermore, there is a contribution from the change of structure when the liquid is heated at constant volume. It is hard to predict correctly the value of C, for liquids, as shown by Moelwyn-Hughes (19611, because it is difficult to calculate the four contributions mentioned above. Therefore, the following empirical equation for C, is proposed here C,/R = 3.02 0.622N + 0.00803IV? (12 IN I26) (9) where N denotes the number of atoms contained in a molecule. Equation 9 can reproduce the experimental values of C, within an average error of 2.1 70,as shown in Figure 8. The values of C, used in developing eq 9 were determined by the relation
+
The experimental values of C , ( a P / a V V ,and (aV/dT)p at 25 "C were taken from the Piterature (Shinoda, 1966). Although eq 9 was obtained for 25 "C, it was used at the
temperatures in the present study because the change of C, in a narrow temperature range is not significant. Frequency, Y. Although anharmonicity is essential from the mechanistic point of view for a finite thermal conductivity, the frequencies of the anharmonic and harmonic oscillators will not be appreciably different for small vibrations of molecules (Horrocks and McLaughlin, 1960). According to Lennard-Jones and Devonshire, under this condition, the potential energy of the cell may be written in terms of the displacement r from equilibrium as (Hirschfelder et al., 1967)
For small vibrations the relation between the potential energy and the restoring force constant is given by
E(r) = E(0) + $V
(12)
where f = 4a2v2m.From eq 11and 12 the frequency of the central molecule in the cell can be derived as
where m is the mass of a molecule and
i(y) = (1 + 12y + 25.2p
+ 12y3 + y 4 ) ( 1 - y)-'o m(y) = (1 + y ) ( l - Y ) - ~- 1
- 1 (14) (15)
and Y = (r/a)'
(16)
u* = u / u 3 = V0/c3NA
(17)
u =a3/G
(18)
In the above derivation, the face-centered cubic lattice and harmonic oscillation of a central molecule are assumed. In the present study, the presence of holes in liquid is assumed so that the distance between molecules, a, is constant and the number of nearest neighbors changes as 2
= 12(VO/v)
(19)
where Vo denotes the solid molar volume at 0 K, which was replaced by that at the melting point. The displacement of a molecule necessary for transfer of its energy to another molecule is usually accepted as r = a / 2 . However, a / 2 may be too large because the dimension of the molecule is not negligible in comparison with r. The diameter of molecule necessary for energy transfer was assumed to be proportional to the collision diameter. Therefore, the expression for r becomes r = ( a - cu)/2 (20) where c is a new proportionality constant. Correlation of Thermal Conductivities for Pure Liquids. By using eq 7 , 9 , and 13, the thermal conductivity of a liquid can be calculated. However, the Lennard-Jones potential parameters t , u, and the constant c in eq 20 remain unknown. Therefore the values of E , u, and c were determined to give the best fit with the experimental thermal conductivity. In the present calculation, liquid molar volumes were estimated from Francis' equation (Francis, 1959) and Vowas evaluated by the approximation of Sagara et al. (1975): Vo = 0.89Vm,where V , is the liquid molar volume at the melting point.
Ind. Eng. Chem. Fundam., Vol. 19, No. 3, 1980 299
The value of 9 in eq 26 is obtained from eq 16 by introducing the expressions
Table V. Values of Potential Parameters and Proportionality Constant liquid elk, K (I, A benzene 108.0 4.760 toluene 142.3 4.630 p-xylene 199.0 4.626 n-heptane 201.3 4.582 n-octane 257.3 4.624 n-nonane 335.4 4.646 n-decane 388.6 4.779
C
f = (E - C x i c p i I ( / 2
0.641 0.503 0.346 0.296 0.233 0.187 0.181
(27)
1
ii = 2 1 / 6 ( 6 0 / ~ A ) 1 / 3
(28)
where
Vo = cix i v o i
(29)
In order to evaluate u'* and 2, the following averaging rules are adopted.
i
2 = 12(V0/D
n.1
The molar volume of the mixture
(31)
6 can be obtained from
6 = (CMixi)/P
(32)
1
0.1
where p is the density of the mixture and is available from Tables 11-IV. The value of in eq 26 can be obtained by
-
0.2
0.3
0.5
0.4
UJ
In the present calculation, cij is given by the following equation
(-1
Figure 9. Correlation of potential parameters: B, benzene; T, toluene; X, p-xylene; H, n-heptane; 0, n-octane; N, n-nonane; D, ndecane.
where k i j is the characteristic parameter between i and j molecules. The average constant-volume heat capacity is approximated by
The best-fitted values o f t , u, and c for several hydrocarbons are listed in Table V. The thermal conductivities calculated from these values are shown by solid lines in Figure 3. Further, the reduced potential parameters and c could be correlated with Pitzer's acentric factor (Reid et al., 1977) as shown in Figure 9. They are well expressed by the following quadratic equations within an average error of 1.7% for c / k T c , 2.5% for a3NA/Vc,and 0.8% for c, respectively.
c, = CX$",i i
- €-
- 0.0535 + 0.20750
+2.024~~
kTC
(21)
-~ -N -A0.569 - 1 . 9 8 5 ~+ 2.1400'
(22) VC c = 1.615 .- 5 . 8 5 8 ~+ 5 . 9 7 4 ~ ~ (23) Correlation of Thermal Conductivities for Liquid Mixtures. Extending the above treatment to liquid mixture, eq 7 becomes
X = &i(60/D?g/ii~A
(24) where V0, 6, i j , and E are average values for a liquid mixture with given composition. On the basis of the concept of a two-fluid model, is given by the following equation
e,,
ij
where
=
CXiU((i) i
(25)
(35)
Results calculated from eq 24 with the above-mentioned approximations are shown in Figures 5-7. The dotted lines show the calculation with k..= 0. It is shown that the calculated values are poor ;Ken kij is allowed to be zero. However, these discrepancies can effectively be removed by introducing kij as shown in Figures 5-7. The values of kij seem to depend on temperature. Conclusions The thermal conductivities of liquid hydrocarbons and their mixtures were measured by use of a relative horizontal parallel-plate method at temperatures from 20 to 70 " C at atmospheric pressure. The data are presented for pure paraffins and aromatics (n-heptane, n-octane, n-nonane, n-decane, benzene, toluene, and p-xylene) and for binary mixtures (n-heptane-n-decane, benzene-nheptane, and benzene-p-xylene). It is found that the new data for paraffins agree with the recommended values reported by Touloukian et al. within the experimental accuracy. To represent the thermal conductivity of liquid, a correlation model has been proposed on the basis of the hole theory of liquid structure in conjunction with the lattice model of Horrocks and McLaughlin. In the present study, a new empirical parameter is introduced to determine the molecular displacement required to transfer a molecule's energy. The values of the Lennard-Jones potential parameters used in the calculation of thermal conductivities can be correlated with Pitzer's acentric factor w. The proposed model is successfully extended to hydrocarbon mixtures by use of the two-fluid model. The thermal
300
Ind. Eng. Chem. Fundam. 1980, 19, 300-309
conductivities of binary mixtures can be correlated with the present model by introducing the characteristic parameter.
Nomenclature a = distance between a molecule and its nearest neighbor A , B = coefficients in eq 4 c = proportionality constant in eq 20 C = constant-pressure heat capacity = constant-volume heat capacity d = thickness of liquid sample do = thickness of standard glass plate E = potential energy of the cell k = Boltzmann's constant k , = characteristic parameter between i and j molecules 1 = distance between crystal lattice planes normal to the temperature gradient m = mass of a molecule M = molecular weight n = number of molecules per unit area N = number of atoms contained in a molecule N A = Avogadro's number P = pressure q = heat flux R = gas constant r = displacement of a molecule from its equilibrium position in a crystal lattice t = temperature T = absolute temperature u = a3/(2)'I2 defined by eq 18 V = liquid molar volume Vo = solid molar volume V , = liquid molar volume at melting point n = mole fraction defined by eq 16 y= z = coordination number Greek Letters t, u = potential parameters in Lennard-Jones potential function h = thermal conductivity of liquid sample ho = thermal conductivity of standard glass plate v = frequency p = density w = Pitzer's acentric factor
6
Subscripts and Superscripts c = critical value i , j = component i and j * = reduced value - = mixture property Literature Cited Briggs, D. K. H., Ind. Eng. Chem., 49, 416 (1957). Challoner, A. R., Powell, R. W., Roc. R. Soc. London, Ser. A, 238, 90 (1957). Davis, P. S., Theeuwes, F., Bearman, R. J., Gordon, R. P., J. Chem. Pbys., 55. 4776 11971). FiliDDov. L. P.: Vestn. Mosk. Univ., IO, No. 8, Ser. Fiz. Mat. Estest. Nauk, '5, 67 (1955). Francis, A. W., Cbem. Eng. Sci., 10, 37 (1959). Gaitonde, U.N., Deshpande, D. D.. Sukhatme, S. P.,Ind. Eng. Chem. Fundsm., 17. 321 (1978). - -, Hirschfelder, J. 0.Curtiss, C. F., Bird, R. B., "Molecular Theory of Gases and Liquids", p 295, Wiley, New York, N.Y., 1967. Horrocks, J. K., McLaughlin, E., Trans. Faraday Soc., 58, 206 (1960). Horrocks, J. K., McLaughlin, E., Proc. R. SOC. London, Ser. A. 273, 259 (1963). Jamieson, D. T., Hastings, E. H., "Proc. 6th Int. Conf. on Thermal Conductivity", C. Y. Ho and R. E. Taylor, Ed., p 631, Plenum Press, New York, N.Y., 1969. Le Neindre, B., Bury, P., Tufeu, R., Vodar, B., J. Chem. Eng. Data, 21, 265 (1976). Li, C. C., AIChE J., 22, 927 (1976). Losenicky, Z., J. Phys. Chem., 72, 4306 (1966). Makita, T., "Nendo to Netsudendoritsu (Viscosity and Thermal Conductivity)", (in Japanese), Baifukan, Tokyo, 1975. Mallan, G. M., Michaeliin, M. S., Lockhart, F. J., J. Chem. Eng. Data, 17, 412 (1972). McLaughlin, E., Chem. Rev., 84, 369 (1964). Moelwyn-Hughes, E. A., "Physical Chemistry", 2nd ed,Pergamon Press, 1961. Nukiyama, S., Yoshizawa, Y., J. Jpn. SOC. Mech. Eng., 37, 347 (1934). Powell, R. W., Jollife, B. W., Tye, R . P., Langton, A. E., Bull. Int. RefrEg. Annexe, 1966-2, 79 (1966). Reid, R. C., Prausnitz, J. M., Sherwocd, T. K., "The Properties of Gases and Liquids", 3rd ed, McGraw-Hill, New York, N.Y., 1977. Riedel, L., Chem. Ing. Tech., 23, 321 (1951a). Riedel, L., Chem. Ing. Tech., 23, 465 (1951b). Sagara, H., Arai, Y., Salto, S., J. Chem. Eng. Jpn., 8, 93 (1975). Sakiadis, B. C., Coates, J., AIChE J., 1, 275 (1955). Saksena, M. P., Harminder, Ind. Eng. Chem. Fundam., 13, 245 (1974). Shinoda, K., "Yceki to Yokaido (Solution and Solubility)", (in Japanese), Maruzen, Tokyo, 1966. Touloukian, Y. S., Liley, P. E., Saxena, S. C., "Thermophysical Properties of Matter", Vol. 3, IFI/Plenum, New York, N.Y., 1970. Tsederbera. N. V.. "Thermal Conductivitv of Gases and Liauids". M.I.T. Press. CambrGge, Mass., 1965. Tye. R. P., Ed., "Thermal Conductivity", Voi. 2, Academlc Press, New York, N.Y., 1969. Ziebland, H., Int. J . Heat Mass Transfer, 2, 273 (1961). \
Receiued for review July 5 , 1979 Accepted May 12, 1980
Fault Tree Analysis of a Proposed Ethylene Vaporization Unit Ulrlch Hauptmanns Department o f Chemical Engineering, University of Oviedo, Oviedo, Spain
The major fault mechanisms in a proposed ethylene vaporization unit are identified and represented in the form of fault trees. A comparison of component failure data from different sources provides a set of input information for their quantitative evaluation, which leads to proposals for modifications of the original design allowing a safer and more economic operation of the plant.
Introduction Accidents in chemical plants cause economic losses and, especially if explosives or toxical substances are involved, constitute a hazard to human life. Therefore a systematic approach to plant safety already in the design stage is required (Lawlay, 1974). Some of the techniques available
and their possible applications in the chemical industry are discussed by Powers and Tompkins (1974) and Menzies and Strong (1979). In this paper the safety of a proposed ethylene vaporization unit is assessed applying the most widely used of the quantitative methods, the fault tree analysis (IEEE,
0 196-4313/80/10 19-0300$01.00/0 0 1980 American Chemical Society
