Heat Transfer Fluids
`and Systems for Process
`and Energy Applications
`
`JASBIR SINGH
`Badger B.\/
`The Hague, The Netherlands
`
`MARCEL DEKKER, INC.
`
`New York and Basel
`
`

`

`Library of Congress Cataioging in Publication Data
`
`Singh, Jasbir, [date]
`Heat transfer fluids and systems for process and
`energy applications.
`
`(Mechanical engineering‘ ; 36)
`Includes bibliographies and index.
`I. Heat-transfer media.
`2-. Heat engineering.
`1. Title.
`II. Series.
`TJ260.S58
`1985
`ISBN 0-8247-7191-5
`
`62l.402’2
`
`84-23039
`
`COPYRIGI-IT© 1985 by MARCEL DEKKER, INC. ALL RIGHTS RESERVED
`
`Neither this book nor any part may be reproduced or transmitted in
`any form or by any means, electronic or mechanical, including photo-
`copying, microfilming, and recording, or by any information storage
`and retrieval system, without permission in writing from the publisher.
`
`MARCEL DEKKER, INC.
`270 Madison Avenue, New York, New York l00l6
`
`Current printing (last digit):
`10
`9
`8
`7
`6
`5
`4
`3
`2
`1
`
`PRINTED IN THE UNITED STATES OF AMERICA
`
`

`

`Organi
`
`Industr
`many f
`Industr
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`major i
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`will the
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`data re:
`compou
`
`5.2 OV
`
`5.2.1 E
`
`There 2
`thetic fl
`derived
`lured by
`(with sc
`nucleus
`zero to
`be used
`based 0
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`
`These 2
`availabl
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`maxim».
`point a1‘
`film tr:
`Vapor p
`
`5 O
`
`rganic Fluids
`
`5 . 1
`
`INTRODUC TION
`
`While the temperature range covered by water and gases for heat transfer
`theoretically accounts for all higl1—temperature requirements, neither of
`these media is suitable for many industrial applications. The problems
`with water (or steam) are related to the high vapor pressures at elevated
`temperatures and to a lesser extent the associated corrosion which necessi-
`tates extensive water treatment facilities. Gases suffer the drawback of
`very poor heat transfer rates (particularly at moderate or low pressures);
`this rules out their use except in special circumstances such as the nuclear
`industry or as products of combustion. Specially formulated organic fluids
`with reasonable heat transfer characteristics and low vapor pressures,
`sometimes termed hot oils, satisfy a relatively small but very important
`demand in the range 150 to 400°C.
`At temperatures between 200 and 250°C, steam is still used very
`extensively and organic fluids no *rnally only find favor if one of the follow-
`ing conditions prevails:
`
`1. The user does not already possess a steam boiler.
`2. Water contamination of a product must be avoided.
`3 .
`l—ligh—pressure equipment is a problem.
`4. Very precise temperature control is required.
`
`In the range 300 to 400°C organic fluids are almost universally accepted as
`the most suitable, although the choice at the upper end of this range is limited.
`
`170
`
`

`

`Organic Fluids
`
`Industrial applications of organic fluids are so widespread and cover so
`many fields of interest that comprehensive listing becomes impossible.
`Industries include textiles, chemical, petroleum, food, nuclear energy,
`plastics, rubbers, offshore oil and gas platforms, and many more. The
`major factors in selection may be high temperature,
`low pressure, cheaper
`system (than, for example, steam), accurate temperature control, and
`lower operating costs. Not all these items will apply in every case, nor
`will they all be realizable at the same time, but they include the overriding
`reasons for selection.
`The total number of organic fluids commercially .vailable is very
`large and selection can be a lengthy and tedious task. The situation is made
`worse by the often difficult (and very time consuming) task of obtaining the
`data required for evaluation from the Various companies marketing these
`compounds.
`
`5.2 OVERVIEW OF FLUID CHARACTERISTICS
`
`5. 2.1 Summary of Data
`
`There are two basic types of fluids in common use, mineral Oils and syn-
`thetic fluids. The former are marketed by the major oil companies and
`derived from thermal cracking of crude oil. Synthetic fluids are manufac-
`tured by petrochemical and chemical companies and consist primarily
`(with seine exceptions) of components with an aromatic structure as the
`nucleus. These two fluid types compete with each other in the range sub-
`zero to 320°C, above which (up to about 400°C) only certain synthetics may
`he used. Selection between the two categories and within each category is
`based on a careful consideration of a number of parameters,
`the most im-
`portant being:
`
`Maximum operating temperature
`Low-temperature behavior
`Safety aspects
`Fluid cost
`Heat transfer coefficient
`General engineering properties, such as corrosion, vapor pressure,
`pumping costs, etc.
`
`These aspects are summarized in Table 5.1 for all the fluids currently
`applications.
`available and specifically marketed for general heat transfer
`Included in this table are the fluid trade names,
`chemical composition,
`the
`maximum temperature at which the fluid is stam
`e, pour point,
`the flash
`ty,
`the relative
`point and autoignition temperatures as indicators of safe
`l in transfer coefficients under forced convection,
`approximate cost, and
`Va or
`r
`0
`-
`.
`.
`.
`some fluids
`P
`pressure at 2.>0 C. Depending on their chemical nature,
`
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`aither of
`oblems
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`:11 necessi-
`back of
`issurcs);
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`
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`

`178
`
`Heat Transfer Fluids and Systems
`
`are suitable only for liquicl—phase applications (indicated by an L under the
`name) while others may also be used in the vapor phase (indicated by an
`Ltxi-‘V under the ‘trade name. The siggnlficance of the temperature limitations
`is discussed in Section 5. 5.2,
`the safety parameters in Section 5.9, and
`heat transfer aspects in Section 5.4. The cost information is intended as
`a guide only and applies in Europe, except for fluids available only in the
`Uni ted States. The cost will Vary according to location, quantity required,
`and of course inflation. However,
`the relative costs should be fairly stable;
`this is indeed the main reason for their inclusion.
`Detailed physical property data for all fluids are given in Appendix 2
`and the salient features of each fluid are discussed in the following sections.
`
`.3. 2.. Z 26. 5 Diphe-nyl—73. 5'1 Dipheuyl Oxide (DP—DPO)
`
`This is probably the best known heat transfer fluid, which is manufactured
`by a number of different companies and sold under a Variety of trade names,
`including Dowtherm A, Santotherm VP—l, and Thermex. The mixture of
`26. 5?}, and 73. 5'1», by weight of diphenyl and diphenyl oxide, respectively,
`abbreviated DP—DPO,
`is the eutectic composition, which freezes at 12°C
`and boils at 2-57.J.°C. The vapor pressure curves of diphenyl and diphenyl
`oxide are so similar that the mixture maybe considered as a single com-
`pound oi’ molecular weight. 166. 0 [1].
`This fluid may be used as liquid or vapor, up to a bulk temperature
`of about 400°C.
`It has a high heat transfer coefficient among; organic fluids,
`although still much below water. There is a great deal of design and oper-
`ating experience with the fluid, extending‘ back over 50 years.
`There are a number of drawbacks in using DP—DPO which must be
`carefully considered. At a cost of about $2. 5 per kilogram,
`it is more than
`twice as expensive as mineral oils, although average for synthetic fluids.
`The relatively high (l2°C) freezing point adds further to the cost of units,
`as this usually necessitates heat tracing. The DP—DPO vapors are quite
`unpleasant and uncomtbrtable to the eyes and skin, as well as being ex-
`tremely toxic. This feature is to some extent accentuated by the fact that
`the fluid is quite volatile, so that any large spillage pose a considerable
`ha:/.ard.
`In hot climates, vapors are liberated in sufficient quantity even at
`atmospheric teirperature to pose a toxic hazard. While good engineeriiig;
`practice normally ensures that the fluid presents no hazard, these aspects
`still have to be coiisidered.
`
`5.2.3 Breox HTF 14 [2]
`
`This is a trade name of B.P. Chemicals and represents apolyalliylene gly-
`col.
`It is basically produced only for the European market.
`
`Organic
`
`Th
`below t
`number
`ganic s
`or petr
`its upp:
`such as
`of deco
`Hence v
`Pr
`fully uz
`organii
`of 55°C
`hot oil
`The so
`ed by 1‘
`
`5.2.4
`
`This 1‘:
`a trad:
`marke
`
`3.2.5
`
`Biiner
`ducecl
`Ml; C}
`500 [6
`C [8l;
`are ax
`
`monly
`and l):
`A
`The 0
`with l
`ponen
`excha
`can k
`
`

`

`Organic Fluids
`
`179
`
`The upper temperature limit of 260°C is quite low, but for applications
`below this value, it represents one of the safest fluids. The fluid has a
`number of unusual properties which may be used to advantage.
`It is an or-
`ganic solvent and will therefore dissolve any waxes, resins, plasticizers,
`or petroleum sludge that may be in the system.
`If it is heated much above
`its upper limit (say above 315°C), it decomposes to form lighter compounds
`such as ketones, esters, and aldehydes rather than carbonizinu. The rate
`of decomposition is normally quite low, so the light ends are easily vented.
`Hence on both these accounts, fouling of equipment is not likely.
`Problems can arise with this fluid if its behavior with water is not
`
`fully understood. At ambient temperatures, water will dissolve in the
`organic and there is no problem. However, at temperatures much in excess
`of 55°C, the water forms a separate phase.
`If the water layer reaches the
`hot oil circuit,
`it will immediately boil, and this can be a serious problem.
`The source for water entry is normally the expansion tank; if this is blanket-
`ed by nitrogen,
`the problem is eliminated.
`
`5.2.4 UCON 500 [3]
`
`It is
`This is identical to Breox HTF 14, being also a polyalkylene ,e,'lycol.
`a trade name of Union Carbide and is distributed principally for the U. S.
`market.
`
`5. 2. 5 Mineral Oil Fluids
`
`Mineral oils are petroleum—based, liquid-phase heat transfer fluids pro—
`duced by the oil companies. The fluids included in this are Caloria HT 43
`[4]; Chevron heat transfer oil 1, 32, and 46 [5]; Essotherm (or llumbletherm)
`500 [G]; Mobiltherm Light, 594, 600, and 605 [7]; Shell Thermia Oil B and
`C [S]; Texaco Texatherm 46 and 320 [9]; Transcal LT and N [10]. These
`are among the cheapest fluids (typically $1.25 per kilogram) and are com-
`monly (although by no means extensively) found on refinery- related processes
`and by weight account for about 8077; of the organic fluids used in industry [11].
`Mineral oils undergo deterioration by oxidation and thermal cracking.
`The oxidation produces insoluble compounds which settle out and interfere
`with heat transfer and increase viscosity. Overheating produces light com-=
`ponents which lower the flash point, and carbon deposits which foul heat
`exchanger tubes. The presence of oxidation inhibitors and proper design
`can keep these problems in check.
`
`

`

`180
`
`Heat Transfer Fl..LlLlS and Systems
`
`5. 2. 6 Diphyl Fluids ‘[12,:
`
`Bayer oflers iwo fluids for it‘ —teniperata.re applications, Dlphyl, which
`is DP—DPO, and Diphyl DT,
`21 iiiixtilre of di111eL11_vl—dipl1enyl oxides. The
`latter 430515 the same as DP-—DPO, has a lower vapor pressure, and may
`be used up to 330°C.
`
`2. 7 Dowilierni Fluids [13]
`
`The Dow Chemical COlI1})E1l1_‘," produces four syiiiiielic fluids wiiicli can cover
`=;.;:plicaiiL)i1s from helov: aimospheric temperaiure. up to about 400°C. The
`iiigliest l-3"1pe1".llLU.’E- range is covered by Dow‘-;l1e:
`A, Clieniically idoiiiical
`5 <iiphenyl—’73.:
`diplieiiyl oxide mixture (_DP—Dl7’O). Dowtlicurm
`which 1: 2, little more expensive, can be used up to about 370°C, Lil which
`:31 its Vapor p1'essu,1*e is only ‘ulmut
`hen‘.
`lt has ihe furiher acivaiitage
`of :1 low pour point.
`It does have a Very sirilii
`N; 0(‘z0r ex 11 ai low <*.m1ce:i—
`i1‘ai'io11s, and is quite toxin. For iemperati res L13 l'O 313°C, D0v.’ihe1‘m L-F
`rn;j; be ‘LlSt3(,l.
`'l‘his costs almosi $5 per lcllogi‘
`:11,
`lJ‘J.t may be used clomi to
`—:3L‘-“C and has 21 very low Vapul“ p1'essLL1'e. For ie111pei‘a.iL11“es clown to —70°C,
`Doxxilzel-m J lllav be L3.SSLl.
`Its upper temperatL11*e limit is 300°C and ii nmy
`be used as 9. liquid or a Vapor above 1S‘r°C.
`as the fifth Dow fluid.
`In the United States Dowtherm HT is 111Rl‘l{€'L€(l
`This is essenizially identical to Saziiotimrin 66 {'l‘hcrminol 66), being also a
`hyd1‘og'enai<:=d ici‘pi1Q1J.y1 .
`
`(% iloiherm l“lu:'ds [14]
`
`six in ihe hlgh—telziperaiure range,
`Gi'_o1.he“ 11 :1 ids, of xahlcli ihere
`are :1 .a.l1ufaciu1'e('1 by Rhone—Poule1lc. The DP—DPO mix‘u_u‘e is sold as Gilo—
`tiierzii DO (excepi in the United States, where it is not mariiciczd at preseiit).
`The l1igl1—‘Le11igeraiu1"o flutis are Gilothoriii TH (inaximum film tem-
`peraiure 37;‘“C) 5.11;} Giloti
`1 ALL‘ (n1a:»;imu111 film temperature 3é()‘C},
`The low pour poini,
`lov: V-spor pressiire, and reasonably high flash polni
`3§soc:iai:ed w:'i'h these ‘=_.\v0 i‘lL1i;ls makes them the most popular among the
`(§il«::—‘».l:ei*m wmge [13]. The reinaining fluids, going‘ down to Gilothe
`. D12
`-“ii: 5. 111inimLI.111 ie111peratL1_1"e of -70/‘C and maxiiiium of 2003C, aLiequ.atel§.'
`.over the 1ovce1"—iempe1‘2.1L1re demaml. As virtually all these fluids are
`‘ aseci on benzene derivatives, c:z1'ef:.l aiic 1‘.lO1l to toxicity is paramouiiix
`
`5. 2. 9 Z\l9_1*loiher11i Fmicis I16‘,
`
`and l\lai’loi'i1e1*m L.
`Chemische \‘-.911: lllils nianuiaciures Alarloiliergii
`These fluids liaixe mi upper limit of al)O‘.11,
`:fi3()”(? and hoih may he piiiiiped at
`
`

`

`
`
`and Systems
`
`Or_<_-;anic Fluids
`
`181
`
`.\lar1otl1ern1 L ca11 he used in the liquid or vapor
`subzero temperatures.
`phase above 290°C. They are slightly Cheaper than DP—DPO.
`
`5.2.10 Santotherm (Therminol) Fluids [17]
`
`Monsanto offers six fluids under the trade name of Santotherm in Europe
`and Therminol in the United States. The DP—DPO mixture is sold as Santo-
`therm VP-1 (Therminol VP—1 in the United States).
`Apart from Santotherm VP—1,
`the high—temperature fluid in this group
`is Santotherm 88, which has a i11aximum hulk temperature of 400°C.
`Its
`major drawback is tl1at it cannot be pumped below 145°C and so in this
`respect resembles molten salts. The most popular fluid is Santotherm 66,
`with its high bulk temperature limit (345°C) combined with very good low-
`temperature properties and low vapor pressure. Monsanto have carried
`out some tests with various mixtures of Santotherm 66 and Santotherm VP—1
`and can provide properties of mixtures. This combines the advantages of
`both fluids (low pour point and vapor pressure of Santotherm 66 and the
`higher stability of VP—1) to produce a fluid with intermediate properties
`(see Appendix 2). The low- to 111ediu111—temperature range, from 220 to
`315°C, with pumping teniperatures down to —-50°C or less,
`is covered by
`Santotzherm 44, 55, and 60.
`
`5.2.11 Syltherni 800 [18]
`
`Syltherm 800, a trade na111e of Dow Corning previously known as Q21162, is
`a modified polymer of dimethyl siloxane.
`It can he used from -40°C up to
`400°C without the need for heat tracing, which makes it unique.
`It has a low
`vapor pressure a.nd is neither very toxic nor unpleasant to handle.
`The structure of the siloxane polymer is indicated in Fig. 5.1. Over-
`heating of the fluid results in the rearrangement. of the Si-O bonds, generat—
`ing polysiloxane and lower molecular weight by—products which can be Vented.
`Thus, under normal circumstances, overheating will not produce carbonace-
`ous deposits, so the efficiency of heat transfer is not impaired. Problems
`can arise from contamination by any one of a variety of compounds, such as
`
`CH3 CH3 CH3
`CH3 CH3
`1
`i/\i/xi
`i/Ox‘/0
`CH3—Si
`Si
`— — — — — -——Si
`Si
`S|i—CH3
`I
`i
`3
`1
`CH3 CH3
`CH3 CH3 CH3
`
`FIGURE 5.1 Dimethyl polysiloxane molecule (Syltherm 800).
`
`
`
`hyl, which
`ides. The
`, and may
`
`;-h can cover
`()()”C. The
`illy identical
`Dowtherni
`
`0°C, at which
`er advantage
`ow concen-
`)'\\'fl1e1‘l1l LIP
`ised Clown to
`
`o‘-9.11 to —7()‘C,
`I and it may
`
`Dow fluid.
`deing also a
`
`‘e rznige,
`sold as Gilc-
`
`:i at present).
`film tem-
`
`‘e 340°C),
`ash point
`5111011; the
`othe1‘m D12
`
`ad.e<;uately
`aids are
`.r amount.
`
`erm L.
`: pumped at
`
`LAM Exh1013-pg. 14
`
`

`

`182
`
`Heat Transfer Fluids and Systems
`
`water, air, acids, and bases, which results in high rates of volatile forma-
`tion. Contamination by oxygen or any oxidizing agent can produce volatile
`oxidation products or in extreme cases can cause the polymer to gel. At-
`tempts to keep the heating system airtight will of course trap any light—end
`materials generated and therefore alter the makeup of the fluid. For exam—
`ple,
`the flash point will be lowered. This is avoided by periodic venting of
`the light components.
`
`5. 2. 12 Miscellaneous Fluids
`
`In addition to the main fluids summarized in Table 5. 1, there are a number
`of fluids which exhibit some interesting features and may become more
`widely used. A fluid which was once used as a heat transfer medium but is
`now used only as a solvent for oils, resins, and waxes is Tetralin [19].
`
`This is 1,2,3,4-tetrahydronaphthalene (CLOHH), and may be used as a
`liquid or as vapor (above 207°C).
`It has a freezing point of —3l”C and may
`be used at temperatures up to 310°C.
`It costs approximately twice as much
`as DP—DPO, which may explain why it is no longer used.
`The Kureha Chemical Industry Company of Japan [11] produces three
`heat transfer fluids under the general name KSK—oils, which are alkyl naph-
`thalenes (hence similar to Tetralin) which are stable up to 320°C and have
`pour points ranging from -30 to —50°C. Two of these fluids are usable in
`the vapor phase, KSK—26O above 280°C and KSK-280 above 295°C.
`Fluids currently used for cooling electrical equipment such as trans-
`formers may find wider application in the chemical and petrochemical field.
`An example is Midel 7131 [20], which is a mixture of esters obtained by
`reacting pentaerythritol (a tetra alcohol) with organic acids derived from
`vegetable origin. This fluid is claimed to be virtually nontoxic and has a
`fairly high flash point, very low vapor pressure, and good thermal stability
`up to about 300°C. Another set of fluids presenting a real alternative are
`halogenated hydrocarbons, an example being the Fluirinert liquids marketed
`by the 3M Company [21]. They are colorless, odorless,
`low in toxicity, and
`completely nonflammable. They are generally very dense and have low pour
`points and low viscosity; the major difference between the set of (at present)
`eight substances is their boiling point, which ranges from 56 to 215°C. They
`can be used in the liquid or vapor phase, the fluids most likely to find wider
`appeal being the high—boiling FC—70 or FC—43. There is one major drawback
`with these fluids;
`they are exceptionally expensive. The high—b0iling fluids
`may cost 40 times as much as DP-DPO.
`Another range of fluids, once quite common but now removed from the
`market, are chlorinated hydrocarbons, examples of which are Dowtherm E
`and Arochlor 1248. There have been a number of objections to the possible
`toxic effects of these compounds, but the major driving force for their re-
`moval probably came in the mid—l970s in relation to the possible threat
`
`Organic Fl
`
`posed by tl
`they are c:
`powerful u
`atoms.
`TE
`spheric oz
`eventually
`It shot
`
`relate only
`that contai
`
`are not pre
`cleavage o
`fluorine wi
`
`3.3 FLOW
`
`5.3.1 Lit
`
`The princi
`tions are V
`used in the
`or in some
`transfer in
`number of
`an electric
`diverted tc
`
`ing cooled
`Also c
`
`the expans
`provides s
`the heating
`using liqui
`solved gas
`shown in E
`minimum ,
`tion. Tent
`
`help this ll
`
`A long
`A hi gl‘
`
`All the prc
`ture, irre:
`different ts
`mixed witl
`temperatu:
`
`
`
`
`
`