E 6 ut - TNO Publications

E 6 ut
¡-JtsLIKATIE NR. 67
þt;ilr-'rt,.:-,',
-
REPORT No. B6 M
u-,;xJ¡riU!'f
.-'i-C-,, t",,1
December 1
¿8 lloy,
çì"
t907
;
NEDERLANDS SCHEEPS-STUDIECENTRUM TNO
NETHERLANDS' SHIP RESEARCH CENTRE TNO
ENGINEERING DEPARTMENT
DROOGBAK IA, AMSTERDAM
*
THEORETICAL EVALUATION OF HEAT TRANSFER IN DRY
CARGO SHIP'S TANKS USING THERMAL OIL
AS A HEAT TRANSFER MEDIUM
(THEORETISCHE EVALUATIE VAN DB WARMTBOVBRDRACHT IN DE TANKS
VAN DROGE-LADINGSCHBPEN BIJ TOEPASSING VAN THERMISCHE OLIE
ALS WARMTETRANSPORTMEDIUM)
by
D. J. VAN DER HEEDEN
Issued
þt tlu Courcil
This report is not to be published
unless verbatim and unabridged
- 0 tr
iNV
RBPORT No. 86 M
December 1966
NtrDERLANDS SCHEEPS.STUDIECE,NTRUM TNO
NBTHERLANDS' SHIP RESEARCH CENTRE TNO
ENGINBERING DBPARTMENT
DROOGBAK 14, AMSTERDAM
*
THEORETICAL EVALUATION OF HEAT TRANSFER IN DRY
CARGO SHIP'S TANKS USII\G THERMAL OIL
AS A HEAT TRAI'{SFER ME.DIUM
(THEORETISCHE BVALUATIE VAN DB WARMTBOVERDRACHT IN DB TANKS
VAN DROGE-LADINGSCHE,PE,N BIJ TOBPASSING VAN THERMISCHE OLIE
ALS WARMTETRANSPORTMEDIUM)
by
D. J. VAN DBR HEEDBN
Central Technical Institute TNO
Issued
þt
the Council
This report is not to be published
unless verbatim and unabridged
VOORWOORD
PREFACE
lVarmtetransport door middel van daartoe geschikte organische vloeistoffen wordt in de industrie met succes toegepast.
De voor toepassing a¿n boord van schepen interessante
voordelen varr deze vloeistoffen t.o.v. stoom, die gewoonlijk
als warmtetransportmiddel wordt toegepast, zijn o.a. de lage
dampspanning bij relatief hoge temperatuur en het ontbreken van corrosieve eigenschappen,
Als nadelen moeten o,a. worden aangemerkt de t.o.v.
stoom geringe specifieke warmtecapaciteit, de kostprijs en de
brandbaarheid van de meeste van deze vloeistoffen.
Omdat de, de warmtetransportcapaciteit bepalende, fysische eigenschappen sterk afwijken van die van stoom, is
het noodzakelijk de ontwerp berekeningsmethode van het
verwarmings-systeem te herzien.
In dit rapport wordt een theoretische methode ontwikkeld
voor de berekening van het, in de dubbele bodem- en in de
dieptanks van een motorvrachtschip, benodigde verwarmend oppervlak.
Hierbij is uitgegaan van de veronderstelling dat de methode hanteerbaar moet zijn voor ontwerpers, die niet vertrouwd zijn met warmteoverdrachtsberekeningen,
Ter illustratie van de werkwijze werd de
Ileat transfer by
means of suitable organic fluids has been
applied succesfully in industry.
The advantages of these fluids with respect to steam for
shipboard application are a.o.: low vapourpressure at relatively high temperatures and no corrosion or erosion of
metallic surfaces.
Disadvantages are the relatively low specific heat capacíty,
the cost price and the inflammability of most of these fluids.
Since the physical properties of organic fluids, that deter-
mine the heat transfer capacity, vary substantially from
those ofsteam, it is necessary to verify the design calculations
of the heating system.
In this report a theoretical method is developed for the
evaluation of the heating surfaces to be installed in double
bottom- and deeptanks of a dry cargo motorship.
It is understood that the method should be suitable for
designers, who are not familiar with heat transfer calculations.
To illustrate the procedure the method is applied to the
heating systems of two sisterships under construction for the
Royal Netherlands Steamship Company.
berekenings-
methode toegepast op het ontwerp van het verwarmingssysteem van twee voor de Kon. Nederlandse Stoomboot Mij.
in aanbouw zijnde zusterschepen.
HET NEDERLANDS SCHEEPS-STUDIECENTRUM TNO
THE NETHERLANDS' SHIP RESEARCH CENTRE TNO
CONTENTS
page
I
2
Surnrnary
Introduction
4
5
6
7
o
7
transfer
2.1 Heat emission of ûlled tanks
Calculation of heat
2.2 Heat emission of heating coils .
2.3 Heat emission of heating oil .
a
7
2..4 Ternperatures to be used in the formulae
,A.pplication to double bottorn tanks
Äpplication to deep tanhs
Exarnple of calculation
Future worh
Àcknowledgement
References
7
,
o
9
9
10
10
12
12
lS
14
14
SYMBOLS, DIMENSIONS AND DBNOTATIONS
Non-dirnensional ratios
Re
wD¿
Reynolcl's number
u
3600uyc
Pr Prandtl's numbel
),
Gr
gflLtHr
Grashof's number
-ly'z¿ Nusselt's
(r)
aH
number
(r)
I
Material constants
l
kinematic viscosity
r¡
c
/,
y
B
clynamic viscosity
m2/sec
-
1"''
(2)
kg.sec/m'z
specilìc heat
kcal/kg'C
thermalconductivity
kcal/mh "C
specific weight
kg/-'
coefficient of volumetric expansion
1/"C
Therrnal and caloric factors
¿
t¡
f¿
t,
l7
^,
Å
a
a
temperature
"C
I]aean cargo temperature
OC
mean oil temperature in heating-coil
"C
wall temperature
frlm temperature
OC
temperature pol.ential
OC
overall heat transfer coefficient
heat transfer coefÊcient at surface
heat transfer rate
kcai/m'zh "C
1) For pipes .FI to be replaced by Ð.
2) For viscosities ¡ 100 secs Redwood No. I at
approximately determined from r, (mr/sec)
(visc. in secs Redwood No. I at 100 "F)
"C
kcal/m'?h'C
kcal/h
100 "F, v
-
canbe
0.25.10-6.
Geornetrical factors
L
H
D
F
d
length
height
pipe diameter
m
m
m
area
m2
wall thickness, layer thickness
m
Miscellaneous
C
w
g
mass flow
kg/h
velocity
rn/sec
acceleraLion due {o glavity
m/sec2
C,n,m. constants
Subscripts
b
u:
i:
t¿ :
calculaled for
t¿
(e'g.
qr,)
calcltlated for /.,
(e.s.',1*)
inner side
(r.9.
ou,
F¡,
D¿)
'ruter sirle
(e,g. au,
F*
Du)
THEORETICAL EVALUATION OF HEAT TRANSFER IN DRY CARGO SHIP'S
TANKS USING THE,RMAL OIL AS A HE,AT TRANSFER MEDIUM
by
D. J.
VAN DE,R HEEDEN
Summarlt
A new development with dry cargo motorships is the application of thermal oil
as a heat transfer meclium
in the heating
system.
Therefore the methods of approximate calculation used for steam heating are no longer usable.
Starting lrom the formulae and data known in the literature, this report deals with a method for calculating the lengths
of piping required for double bottom and deep tank heating. Based on the calculation of heat losses from filled tanks, lt is
indicated how heat transfer in and around the pipes should be determined, and how the required length of pipe can be
ascertained.
For double bottom fuel oil tanks, filled with a widely used residual fuel with a viscosity of 3000
100 "F, a number of diagrams are given to facilitate the calculations.
I Introduction
It is a common practice to heat liquids in ship's
tanks by means of heating coils. Most tankers are
equipped for this purpose with heating coils in the
cargo tanks. Dry cargo ships using heavy fuel oil
have heating coils in the double bottom tanks and
often have heated deep tanks for carrying edible
oils and other liquid cargoes.
The heating medium is generally steam. fn most
designs the required heating surface is not calculated precisely, but is determined by rules of thumb
based on experience. A recent development with
dry cargo motorships is the use of an appropriate
oil as heat transfer fluid in the heating system. The
approximate rules customary for steam heating are
no longer usable now, and more precise calculation
of the required heating surface becomes necessary.
By reference to the data available in the litera-
ture, the intention of this report is to provide
a
guide for determining the required heating surface
of pipes using thermal oil as the heating medium.
The emphasis will be on the double bottom tanks,
as the lesidual fuel oil, which motor vessels store in
these tanks, will be of fairly constant composition.
In the case of deep tanks, which rnay carl.y a very
wide variety of cargoes, only the general procedure
for calculation will be set forth. The report has been
drawn up on the assumption that it must be usable
by designers who are not familiar with heat transfer
calculations.
It is intended to verify the calculation method
with measurements on board.
The ultimate object of calculating heat transfer
is
No. I at
to determine the required length of heating pipe
and the velocity to be applied. Both are dírectly
related. The basis of calculation is the quantity of
heat to be transferred. Calculation can thus be
divided into a number of steps:
l.
2.
determination of the heat emission of the filled
tank,
heat emission of the heating pipe to the tank
contents,
3.
heat emission of the heating oil to the heating
pipe.
The quantity of heat invoh'ed in these steps remains the same and is determined for the first step.
The second and third steps gir,'e the required length
of pipe and the velocity.
Heat transfer between two media separated by
a wall can be defined with the formule Q :
F.k. L t. F rrray be either given (tank walls) or required (pipe surface); A I is usually assumed for a
specific case and revised afterwards if necessary,
leaving determination of k as the main item. If ,t
is not known from measurements or from the literature, it can be calculated from the equation:
,-l
1òlII
cxit)r^
If a¿ and au are comparatively low and ,1 is high,
which is usually the case when two viscous liquids
are separated by a metal wall, the thermal resistance of the wall can be disregarded and the equation is simplified to:
K: ll
2 Calculation of heat transfer
secs Reclwood
I
-+at
u.q
If
one of the ø's is very high in comparison with the
other, the smaller ø practically controlls heat trans-
fer and the formula becomes k - u¿ or k - au.
The main remaining item in calculation is thus
determination of the heat transfèr coefficients.
The heat transfer coefficient ø can best be found
from the equations with non dimensional factors as
mentioned in the literature and evolved by various
authors. In the problem in question we are concerned with free flow (owing to differences in temperature) along walls and pipes and with induced
flow in pipes. In both cases, moreover, a distinction
has to be made between laminar and turbulent
flow. Convective heat transfer for a free flow can
be formulated with:
Nu : C.(.Gr. Pr)"
in which C and n rnay vary from
case
to
case.
For convective heat transfer at turbulent flow
in pipes, the general formula is:
Nu
:
C. Ren. Prm
often with adjustment factors for viscosity and the
diameter/length radio. For laminar flow in pipes
the equation is more complicated. In general the
heat transfer coefficients for laminar flow are low
compared with those for turbulent flow. Therefore
laminar flow in heating coils should be avoided.
Heat engineering literature gives many formulae which are of varying value for the problem under investigation. Those not familiar with this literature are advised to use the V.D.I. Wärmeatlas [11. This not only gives a review of existing
formulae, with a clear indication of their applicability, but also gives practically every formula in the
form of a graph, which may make the calculations
less time consuming. More time consuming than
the calculations with the formulae themselves is
often the determination of the dimensionless factors. The Wärmeatlas includes graphs for these factors. In order to calculate the factors it is necessary
to have the material constants of the various media,
such as viscosity, specific heat, thermal conductivity, etc., preferably for the greatest possible temperature range. It is very important to have reliable
values for the material constants, as these are the
basis of all heat transfer calculations.
It will be clear that it takes time to find material
constants at various temperatures, to calculate factors from these, likewise for a sequence of temperatures, and to apply these in the relative formulae.
If calculations for a specific liquid, which is kept
at a specific temperature, have to be made frequently, it is worthwhile to prepare a graph, from
which ø can be determined directly.
2.1 Heat emission oJ flled tanks
In general the tanks under investigatìon
have ver-
tical and horizontal walls. Exceptions are the sloping walls of deep tanks and settling tanks and the
bilge in the bottom tanks.
Up to an angle of 45 ", however, the formulae
for a vertical wall still apply. For bottom tanks, it
is convenient to suppose the rrertical wall being
extended to the bottorn.
For a vertical wall and for a free laminar flow,
the formula Nu - C (Gr.Pr)" reads:
Nu
:
uH
A
-
0.652
and for a free turbulent flow:
aH
Nu:-::0.129
1
(Gr'Pr)'i"
(2)
it is necessary, to ascertain whether the
flow is laminar or turbulent and for this purpose to
calculate Gr. Pr.
For Gr. Pr < 108 to lOe formula (l) is used and
lor Gr.Pr > 108 to lOe formula (2) is used.
In the range Gr. Pr : 108- lOe both formulae
may be used; as a rule the results will differ by
only a very low percentage. As Gr contains the
factor 11s, o with turbulent flow is independent of
the height of the wall, while with laminar flow it
decreases as the height increases.
The material constants occurring in the dimensionless factors have to be taken at the film temperature t¡, calculated lrom:
Therefore
t¡:
ttïtu,
The above formulae should be applied to water
side vertical walls. For these walls a,, will be in the
order of 10,000 kcalimzh oC and, because of the
then negligible thermal resistance, the wall temperature will be practically the same as the water
temperature. The thermal resistance of wall and
paint coating may be neglected for design purposes
and therefore e¿, calculated from formula (1) or
(2), is decisive for the
't-value. In an earlier investigation [2] it was found that the thermal resistance
of the paint coating is not entirely negligible.
Of the total thermal resistance, ø¿ however has
the greater effect and the resistance of the paint
coating is of minor importance. Neglecting it in
design calculation may be regarded as a safety
factor. If the vertical wall is bordered by stationary
air (the inside walls) uuwill be low on the air side
and will largely determine the É-value. For air,
&6 cã.r1 likewise be calculated with formula (1) or
(2) or cletermined with the diagrams for air in the
Wärmeatlas; the rcsult will generally be 3 to 4
kcal/m2h "C. For design purposes, surfaces bordered by air can thus often be calculated with an
assumed À-value.
He at transfer formulae for
finite horizontal walls
2.2 Heat emission oJ lteatinp coils
The calculation of heat emission of the heating
coils is comparatively simple, N'fost heating pipes
in tanks will be horizontal. For free laminar flow
in horizontal pipes applies:
assuming frcc flow towards the ends are mentioned
llu:
in referencc [3]. As the horizontal walls of a tank
are bordcrcd by vertical n'alls, impeding free flow,
the leng-th r,r'ould in theory have to be regarded
as infinite, and since the longitudinal dimension
appears in the denominator of these formulae, this
means that heat transfcr by convection will be nil.
Of course heat transfer occurs by conduction. Experimental investigation has shown that on the
tank bottom, under the heatins coils, a layer of cold
oil exists in which heat transfer takes place almost
solelv by conduction [2]. The ,t-r'alue is thcn found
from Å in which ð is assumed to be about 3/4
^lð,
of the distance betwecn bottom and heating pipe.
As a, is high, the bottom temperature can be assumed to be equal to the seawater temperature. At
the top (tank deck) heat transfer to the air occurs.
Therefore uu will generally be the deciding factor
ancl we may take au. : 3.5 to 4.5 kcal/mzh 'C.
The k-r'alues so found must be corrected to allow
for the additional area and extra heat conduction
of be ams and other structural parts. This correction
depends on many factors and exact calculations
arc hardiy possible, an estimate thus has to be
made. The percentage increase will har,'e to Jte
greater the lower the ,t-value is and tlte more beams
there are ; the greatest increase will have to be included for the bottom whcre there are many beams.
In a previous investigation [2] these factors were
calculated and adjusted to the results of heat flux
measurements and heat balances.
Some of the values so f'ound wcre:
Bottom,
bordered by seawater: incr. 75on
Tank deck, bordered by atmosphere : ,, 1 5 ? o
Vertical wall, bordered by seawater:
,, 25o, o
IL1
Oo
Vertical wall, bordered by air:
'O
,t
The foregoing will make it clear that calculation
of heat emission by tank walls is beset with a numltcr of uncertainties, which compel estimates and
assnmptions to be made. This contrasts with heat
transfer in and around pipes, on which extensir.e
literature exists. There is thus a constant need for
practical measurements of heat emission by tank
lvalls and it is fortunate that the inr.estigations
rnentioned [2], made during a tanker,s trial trip,
Iulnished information which forms a basis for at
least calculating heat emission of double bottom
tanks. This will be gone into further in Section 3.
u I)",
0.40(Cr.Pr)',
,-
(3)
A
and for frec turbulent flow:
l\,ltt
u
.-
D",
0.129 (Gr. Pr¡'
)"
(4)
"
The material constants in the factors are taken at
the wall tempcrature, except for p, which is taken
at the mean oil temperature /¿.
The temperatures and pipe diameters occuring
in tanks will usually be in the laminar range and
formula (3) will thus be used. For Gr.Pr > lOe to
100, formula (4) is used.
For vertical pipes, formulae (l) and (2) for a
vertical wall can be used, thc height instead of the
diameter then being incorporated in the factors.
For laminar flow a correction has to be applied.
This correction, which depends on the heightcliameter ratio, is shown graphically in the Wärmeatlas l1].
On the whole the heat transfer of a vertical pipe
is higher than of a corresponding horizontal pipe.
As thc heat transfer of an inclined pipe rapidly falls
to thc value of a horizontal pipe, it is recommended
to use the horizontal pipe formulae.
2.3 Heat emission oJ heating oil
In this case the formulae for induced flow must
applied. For Re
<
be
2,320 the formula for laminar
flor¡¡ reads:
Nu-
rx
I),
:
)'
0.0668
3.6s
+
I
+0.04s
,0 r+
(!1)
\1
(s)
lnt
All material constants (except UrD) Io be taken
at
the mean liquid temperature /¿.
As the heat transfer for laminar flow, especially
in long pipes such as applied in double bottom
tanks, is fairly low, the laminar range should be
ar.'oided. Regarding turbulent flow, it should be
noticed that most of the formulae mentioned in the
literature give excessively high l'alues in the range
between laminar- and turbulent flow. They can
only be used for Reynolds numbers greater than
I
10,000. As there is a big chance of just
being within this range, a formula should be chosen
which applies frorn Re : 2,320. A very useful one
8,000
to
is:
(l1r1s1-/eo11s1)
the velocity ¿o of the heating oil is chosen, the
e,'n{t* (?)'''} (,fl)''- ,u, Ifmassflow,
G, carr be calculated. The outlet temper-
Material constants (except for q*) again to be taken
at ta.
2.+
heat being transferred, is supplied by cooling of the
heating oil.:
Q : G'c
ct Dn
Nu_j: A
:0.116
oil that is to be expected, however, no major error
average between inlet- and
is
taken lor hr. Since all the
temperature
outlet
will be made if the
Temþeratures to lte used
in theJormulae
There are some difficulties in choosing the proper
temperatures to be used in the formulae' In calculating the heat emission of tanks, the temperature of the contents will be taken, depending on the
requirements, among others, regarding pumpabilalso chosen, for
The seawater temperature
instance as -4'C.
The temperature of the walls bordered by seawater
can be assumed to be equal to the seawater temperature. This means k - u¿. For other walls, the
temperature diflerence between tank contents and
adjacent hold and an assumed fr-value can be taken
in most cases.
As regards heat emission by the heating coils,
the temperature of the contents is again given, but
the wall temperature of the piping is not known.
The same applies to heat transfer in the piping:
the inlet temperature of the heating oil is known
or chosen, the wall temperature is not known'
As the thermal resistance of the pipe wall is neg-
ligible, the wall temperature will be the same in
both cases.
Q : ou F" (t*-tù : ct¿ F¿ (tu-t,u)
The value at which t*will adjust itself thus depends
on the ratio between ø¿ and au. The value of au
itself depends greatly on l¿¿, since tlllIargely influences free convection around the pipe. In most cases
a¿ will be greater. Thus /, will be closer to the temperature ofthe heating oil than to that ofthe cargo'
Therefore, ú, should be estimated first and, after
calculation of ø¿ and ø,r, it should be revised if
necessary and the calculation repeated'
For the mean temperature f¿ of the heating oil,
it is not possible to take the inlet temperature because this temperature decreases as the oil flows
through the pipe. Properly speaking it is necessary
to integrate along the length of the pipe since ø is
not proportional to the temperature. With the comparatively slight fall in temperature of the heating
ature and hence the mean temperature tb carl
easily be calculated as well. With ¿a and the assumed temperature of the tank contents, the mean
wall temperature /, is determined as already described.
3 Application to double bottorn tanks
In motorships the double bottom
tanks
will gener-
ally be used for storing residual fuel. The viscosity
of customary residual fuel will be between 2,500
and 3,500 secs Redwood No. I at 100 'F. The
purnpability of this fuel requires a temperature of
approximately 35 oC. For this common case it is
worthwhile to compile from the formulae a couple
of graphs in order to facilitate design calculations.
In the investigation of reference l2], the cargo
consisted of fuel oil with a viscosity of 3,000 secs
Redwood No. I at 100 'F, which was kept at an
avalrage temperature of 55 'C.
Although this oil corresponds closely to that carried
in double bottom tanks, the measured heat transfer
coefficients cannot be used, because the oil temperature was higher than we have assumed for
double bottom tanks and ø increases as viscosity
decreases. This will apply mainly to cases in which
¿¿ is decisive for the À-value, i.e. for the side shell
bordered by seawater. For walls bordered by air,
ø,, is decisive and the higher oil temperature will
have had little effect on the ,t-value. Some ,t-values
then measured (without correction for beams) are
given in Table I.
Table I
k-values
for oil, 3,000 secs Redwood No. I at
Heat-flow
Surface
From
Vertical wall
Vertical wall
Vertical wall
Bottom
Tank deck
100
oC.
average temperature: 55
oi
oi
oi
oi
oi /Ai'
To
Seawater
Atmosphere
Bmpty tank
k
kcal/m'zh'C
12.0
.t.J
Seawater
3.5
I .35
Atmosphere
4.0
Obviously calculation is only useful for vertical
walls not bordered by air. The measured value of
ll
oC
was lower than would result fiom
formula (2). Thus this fb¡rmula clearly is on the
12.0 kcal/m2h
For the other surfaces heat transfer to the
the ,t-value. The heat transfer at the
determines
air
bottom occurs only by conduction into a stationary
safe side.
layer ofoil.
Fig. I has been compiled from formulae (1) and
(2) for fuel oil with a viscosity of 3,000 secs Redwood No. I at 100 'F with an average temperature
of 35 "C. The conr-ersion from laminar to turbulent
flow occurs at about I m height, which happens
to be about the height of a doul¡le bottom tank.
For a greater height, the flow is certainly turbulent
and ø is thus independent of the height of the wall;
for a smaller height laminar flow should be taken
into account which means a will increase with clecreasing height. The graph gir:es the values for 11
: 0.5 m and H - L0 m. In this case and for this
limited temperature range it appears that ø bears
comparatively little relation to the wall temperature. In calculating heat emission from double
bottom tanks, Fig. I can be used for heat transfer
through a vertical wall bordered by seawater, in
which f,¡ is equal to the seawater temperature, and
also for vertical walls bordered by a tank of unheated oil, whereby tp may be considered to be the
average of the two oil temperatures.
For heat transfer around horizontal pipes, Fig. 2
has been compiled from formula (3). For this oil
and for the pipe diameters used in the tanks, the
flow is always laminar. As expected, ø depends
greatly on tLD, in this case the pipe temperature,
and to a slight extent on the pipe diameter. A
number of pipe diameters are included in the graph;
intermediate dimensions can be interpolated.
For heat transfer in the heating pipe, Fig. 3 was
compiled, based on the heating oil used on board
the m,s. "Mercurius" and m.s. "Neptunus" of the
Royal Netherlands Steamship Company. As this
concerns heat transfer in the pipe, this graph can
also be used for tanks with other contents, e.g.
the deep tanks. The graph is based on formula (6).
The following assumptions har.'e been made.
l.
The adjustment factor for the length of the pipe,
l+(DlL)'1", has been taken as unity, which is
permissible for long pipes as applied in the
double bottom tanks. For short pipes this ad-
justment can, if necessary, be applied to a as
read from the graph.
2. For the correction factor, (r16fr1*)0,'n, a mean
value of 0.95 has been taken. This proved to be
a fair average for the expected pipe wall temperatures,
It will
be seen thaf a is closely dependent on ¿¿ and
to and for certain ranges also on the pipe diameter.
At the lower velocities, where in the graph
curves for
l¿
the
stop, the region of laminar flow begins.
The material constants of the heating oil, important in calculation, are included in Table 2.
Marerial constants
., n.;rf*t"t2l usecl on boaril the m.s.
,rNlercurius" and the m.s. ,rNeptunus".
t
v
c
1
kca].l
kcal/
kg'c
mhoC
0.468
0.
0.
0.
0.
0.
0.
0.
0.
0.
"C
kg/m'
40
50
60
863
857
Bs0
70
844
BO
Õ.1Õ
0.486
0.496
0.s05
90
831
0,5 15
100
120
150
824
0.s25
811
0.543
0.572
791
0.477
4.
10u
kg sec/m
'i.'' 10c
m2/sec
t2
3960
11
2535
45
29
10
10
1645
l9
12 10
l+
09
09
854
10
OB
06
04
677
o
546
348
210
6,5
4.2
,6
The procedure for calculating heat transfer in
a
double bottom tank is as follows. The ,t-values are
determined for the r.'arious surfaces, for instance
with the aid of Fig. 1 and the measured values
given in Table L This determination should be
based on the most unfavourable conditions. As
heat transfer to the surfaces bordered by air is not
particularly great, the most unfa'u'ourable situation
will occur when the adjacent tanks are filled with
unheated oil. A list can now be made of surfaces,
factors for the influence
't-values and adjustment
:
F'k. L I is determined.
From
this
Z
of be ams.
Q
For the heating pipe, a provisional choice will
have to be made as regards the diameter and velocity to be applied. The inlet temperature is known
or is chosen anc{ after calculation of t¿ and a provisional estimate of t*, au and a¡ can be calculated
with the aid of Fig. 2 and Fig. 3 respectively. From
this, t* can be re-determined and the calculation
revised if necessary. As the relationship F"f F¿ is determined with the choice of the pipe, the pipe sur-
face and therefore the pipe length can be ascertu,¿ F¿(tr-t*).
ained from Q - ou F"(t*-tt):
This can be repeated for other pipe diameters and
other velocities, in order to find the most economical solution based on material consumption, pump
capacity, etc.
For the fuel oil settling tanks, the procedure is the
same. For other fuels and temperatures, Figs. I
and 2 do not apply and the formulae will have to
be used. In the dimensionless factors, the material
constants for the appropriate contents and temperature should be used.
Fig. 3 of course continues to be usable.
4 Application to deep tanks
temperature below this value. Although in the calculation the average oil temperature in the pipe
is used, it is advisable to determine also in this case
the pipe wall temperature at the inlet side by reference to the inlet temperature of the heating oil and
a calculation of u¿ and au at that location. The requirement of a safe pipe wall temperature will automatically result in a heating coil with ample dimensions, so that, by increasing the inlet temperature,
sufifrcient heating capacity will be provided for ma-
The same considerations and formulae apply for
calculation of heat transfer in deep tanks. A difficulty is the choice of the cargo on which the heat
loss calculation should be based.
Deep tank cargoes comprise not only edible oils
but other liquids as well. It should thus be examined what cargo is the most Lrnfavourable as regards
heat losses and length of pipe required. Low viscosity liquids with high ther:mal conductivity will
lose much heat outwards, but on the other hand will
also harre a good heat transfer with the heating
coils, and for such a liquid therefore, the pipe does
not necessarily need to have the maximum length.
As the required data, especially material constants, are lacking or incomplete for many liquids,
carried in deep tanks, it is not yet possible at this
stage to establish the most unfavourable cargo on
which the calculation should be based.
In deep tanks, it is normal practice to install
heating coils parallel to the sloping tank walls.
Since there is no stagnant layer here, as occurs at
the bottom, the obvious supposition is, that installing the coils in this way will result in increased
heat transfer through the relevant tank wall. No
measurement data are available for this situation
in the literature. Owing to these uncertainties, it
is justifiable to have heating pipes of ample dimensions. For the sloping tank walls, the formulae for
vertical walls can be used. The coils along the
sloping walls are partly horizontal, partly parallel
to the wall. The formulae for purely vertical pipes
will result in too high a 's, therefore it seems better
to apply formulae for horizontal pipes.
For certain types of edible oils, a maximum
heating pipe surface temperature of about 70 to
75 'C is often required in order to prevent decomposition and discoloration. This must be taken into
account in the calculations by keeping the inlet
terials with a higher heat emission but for which
this requirement does not apply.
5 Exarnple of calculation
As mentioned in the foregoing, a heating system
using thermal oil was installed in m.s. "Metcurius"
and m.s. "Neptunus" of the Royal Netherlands
Steamship Company. In this section the calculation of the heating coil in one of the double bottom
tanks viz. side tank No. 3 will be demonstrated.
The following assumptions were made:
Contents: residual fuel, visc. 3,000 secs Redwood No. I at 100 oF, temperature: 35 "C.
Seawater temperature: + "C,
Temperature in the cargo space over the tank:
5'C.
Adjacent tanks contents: unheated oil, temperature: 10 "C.
The transmission calculation is given in Table 3.
The 'L-values were determined as follows: For the
starboard wall, ø can simply be read from Fig. I,
assuming turbulent flow will occur. As the wall
temperature here is the same as the seawater
temperature, ,t equals u¿. For the side walls with
the other tanks it has been assumed that l, is the
average of the two oil temperatures, i.e.
I
tw:
Table
35+
10
:
22.5 "C.
3
Example of transmission calculation
Surface
Side shell
S.B.
Tankwall with
3M
Tankwall with
2 S.B.
Tankwall with
3 S.B.
Tankdeck
Bottom
Dimensions
F
m
mz
19 x 10.5
lB.5 x 1.05
4.5 x 1.05
5.3 x 1.05
lB.5 x 5.1
lB.5 x 5.1
Temperature
of adjacent
space oC
.C
^t
k
kcal/m'?h"C
Adjustment
factor for
bea.ms etc.
k
corrected
Q
F.k. Lt
-kcal/h
3.5
t.25
16.9
25
6.9
1.15
7.9
3,840
10
25
6.9
1.10
7.6
BBO
5.6
10
25
6.9
1.10
7.6
1,060
94.5
94.5
5
30
39
4.0
1.15
4.6
4.8
13,000
20.0
4
39
19.4
10
4
r
.)-l
l 50
I
3,200
t7.700
49,680
l3
From Fig. I it follows that u¿ - 13.8 kcal/mzh "C.
Assuming that this will be the same on the other
side of the wall (owing to the lower oil temperature
a will in fact be slightly lower) , we can calculate:
r - :
k - -_
l1
+ &l1
G,i
From Fig. 3,
Q
0.r20
r)
0.0375
-
48.30
",
:_
F¿
+0.9+
:1
:
ple we find: /r,
IB
,4
:
a¿
F¿
(to-t*)
- approx. 69 'C
and ur,
:
{Q
kcal/m2h "C. We now find F¿ : 31 m2 and Z :
240 n. As øu is low relatil'e to &,¡,, c(¡¡ largely determines the heat transfêr. It can thus be expected
that increasing zø, and hence ø¿, will have comparatively little effect. If, for instance, we take ¿o :
2 m/sec, then G - 7,860 kg/h and toú1et:77.5
'C. In the same way as above, wc can now calculate: tu - approx. 84 'C, a¿ : 456 kcal/m2h 'C,
oC
tLD
- approx. 78.5 and au : 50 kcal/mzh 'C.
Thence it follows that F¿ : 19.5 m2 and L : 152 rn.
Increasing the inlet temperature has much more
effect. The permissible maximum is 130 "C, the
possible maximum 180 "C (according to owners).
Based on an inlet temperature of 130 "C and w :
I m/sec, the length of pipe recluired is 70 m, if zr
: 2 m/sec, this is reduced to 55 m.
Table 4 gives the data and results of these calculations.
In the vessels concerned, a lotal of 56 m of pipe
was installed in side tank No. 3. With an inlet temperature of90 "C, therefore, a heat supply of50,000
kcal/h cannot be reached. Even if ¿{, were raised so
higlr that tql were practically equal to /¿, in this
case the maximum heat transfer is achieved, no
more than some 27,000 kcal/h can be transferred.
The table shows that a heat transfer of 50,000
kcal/h can be reached when ¿o : 2 m/sec and the
inlet temperature is 130 'C. At an inlet temperature
of 150 "C a velocity of even less than I m/sec suffices
for a pipe length of 56 m.
3.2 kcal/m2h "C.
1.3,600 .10.0+og+r.831
F" (t*-tt) :
ancl, with the aid of Fig. 2) tu) càln easily be chosen
that the calculation tallies. For the above exam-
Other initial assumptions were i w : I m/sec and
the inlet temperature of the heating oil : 90 "C.
This is low because the supply pipe is going through
the cargo space. From ¿r., : I m/sec it follows from
G: w.3,600.F.7 that:
G
ou
so,
The adjustment factors for the beams are estimated in relation to the size of the À--n-alue, the number
of beams in these areas, and the values mentioned
in Section 2.1. Rounded off upwards, the maximum heat emission is thus approximately 50,000
kcal/h and the heating coil must be able to supply
this amount of heat.
The pipe diameters chosen for the above mentioned vessels, i.e. D¿ : +0.9+ mm and Du, :
48.30 mm give:
F
:
it follows that:
50,000 - att I.lB F¿ (t,u-35) : lB5 F¿ (77.5-t*)
There is a direct connection between tr¡ and au
6.9 kcal/mzh "C.
),
oC and
can be re ad at lB5 kcal/mzh
from the formula:
The Å-r'alue for the tankdeck has been taken from
Table 1, that for the bottom is calculated on the
assumption that with a clistance of 5 cm bctween
the coils and the bottom, therc will be a stagnant
Iayer of oil 314.5 : 3.75 cm. From this rve calculate :
k:
a¿
3.930 kg/h
and from
: G.c (/ir1s1-/o.11si)
that: /ontret : 65 "C.
G
For the calculation we can thus take:
90+65
tttal.-
-
2
6 Future work
-77.5"C.
Full scale measurements of temperatures and heat
Table 4
Calculation of pipe length lor 50,000 kcal/h: pipe diameter D,
u
G
m/sec
ks/h
1
2
I
2
I
3930
7860
3820
7640
3740
¡
rnlet
.C
/outlet
"C
90
90
65
130
130
150
106
118
77 .5
r26
tb
.C
tt.3
-
40.94 mm and D¿¿ : 48.30 mm.
s.¿
kcal/m'!h'C
.C
Qú
L
kcal/m'?h'C
m
69
78.5
240
55
48
tru
B4
118
370
103
40
50
69
t24
70s
t14
77
138
430
119
82.5
185
465
152
70
1
14
transfer
in double bottom- and deep tanks, under
normal service conditions, are under investiga-
B
tion.
,
7
1.
V. D, L WÄerrrn-Arr-¡s, Düsseldorf
3.
1954.
D, J. vex ¡¡x- IInno¡.N and In, L, L. Mur-unn: "I:Ieat
tiansfer in cargo tanks of a 50,000 dwt. tanker"'
Report No. 67 S, Netherlands' Ship Research Centre
TNO, March
Acknowledgement
The essential help of and the close cooperation
with the Kon. Nederlandse Stoomboot MÜ N.V.
is fully acknowledged.
References
1965.
W. H. McAo¡tls: ttl{eat Transmission" 3rd Edition,
Chapter 7, New York 1954'
PUBLICATIONS OF THE, NE,THERLANDS SHIP RESEARCH CENTRE,
(FORMERLY THE NETHERLANDS RESBARCH CENTRE TNO FOR SHIPBUILDING AND NAVIGATION)
Reports
1
S
3
S
4
S
5
6
S
The detelmination olthe natural tequencies of ship
vib_rations (Dutch). By prof.
ir H. E.Jaeger.
December 1957.
ber
30
1951.
Standard-recommendations lor measured mile and
prof.
B. J.
corì-
(Dutch). By
June
ir
A. Verduin and
ir
B. Brrghå;-;tT
1952.
M 9y_lir4çl u.ear in marine diesel engines (Dutch). By
il J l. Visser. Deccmber. 1952.
B M $1al¡9is_gn! t_elting of lubr-icating oils (Dutch). By
ir R. N. M. A. Nlalotaux and irJ. G. Smt.-July 1SSS.
I S Stability experiments on nodeli of Dutch and French
S
ber
1958.
À,fodel tests concerning damping coeflìcient and the
increase in the momeñt of inerlia due to entrained
y¡r^ter of ship's propellers. 81, N. J. \¡isser. April
1960.
32S
of
33M
he
of
34
S
36S
F.
van Zeggeren. April i960.
Acoustìcal principles in ship design. By ir.f . H.
Janssen. October I95ì9.
Shipgrotions in longitudinal waves. By irJ. Gerrits-
ma. February
1960.
37}'4
N'I
12 M
11
M
An experimental anaìysis of shipmotions in longitudinal regnlar waves. By irJ. derritsma. Decem-
3l \,f
35S
13
Bonebakker.
1950.
Practical possibilities of constructional applications
of aluminium alloys to ship construction. B-y prof. ir
H. B.Jaeger. lVlarch 1951.
Co,rrugation of bottom shell plating in ships with allwelded _o_r partially welded bottoms (Dutch). By
prof. ir H. E. Jaegel and ir H. A. Verbeek. Nóvem-
S
7
of righting ìevers. By pr.of. ir J. W.
N{ay
?3urPoses
ï.Ñ:ö:
Investigation of cylinder wear in diesel engines by
(Dutch). By iiH. Vis-
means of laboratory machines
38S
39 N,I
a|-axial vibrations of
ir D. van Dort
ser. December 1954.
40s
and
factol for the added
vibrating ships with rectangular cross-sectjo":.Py i-r. W. P. A. Joosen ancl dr J. A. Sparenberg.
mass _of
Aplil
41
16
N{
ônalysis a_nd_testing of lubricating oils II (Durch).
By ir R. N. N4. A. l\Ialotaux and drs .I.B.Zabé\.
March
1956.
1961.
S
42S
43C
4+S
Some acoustical properries of ships with respecr to
noise control. Par.r I. By ir J. H.Janssen. Àugust
45S
Some acoustical propert-ies ol ships with respect to
noise control. Par[ II. By ir J. H.Janssen. August
1
I
962.
962.
46
C An investigation into the influence of the methocl of
application on the behaviour of anti-corrosive paint
:y^.^tg-. in seawater. By A. M. van Londen. Aùgust
47
C
Results of an inquiry into the condition of ships, hulls
48
C
Ekama, A. NL van Lõnden and drs P. de'Wolf. December 1962.
Investigations into the use of the wheel-abrator for
50
S
The influence of a bulbous bow on the motions and
5r
M
1962.
in relalion to iouìins and corrosion. Bv i; H.
C.
By prof. ir
.t3F3 *r,ooo
ma.January
52C
!
53S
54c
55s
s6c
57
M
58
S
59
M
60
S
61
S
The braking of large vessels. By prof. ir H. E. Jaeger.
August
A study ofship bottom paints in particular pertaining
to the behaviour and action of anti-fouling paints.
By A. M. van Londen. September I963.
Fatigue of ship structures. By ir J. J. W. Nibbering.
of exposure of anti-fouling paints in
Lesser Antilles. By drs P. de Wolf
uter-Schriel. November 1963.
Determination of the dynamic properties and propeller excited vibrations of a speciai ship stern arrangement. By ir R. Wereldsma. March 1964.
Numerical calculation of vertical hull vibrations of
ships by discretizing the vibration system. By J. de
Vries. Apriì 1964.
Controllable pitch propellers, their suitability and
econom,v for large sea-going ships propelled by conventional, directly-coupled engines. By ir C. Kap-
The distribution of the hydrodynamic forces on a
heaving and pitching shipmodel in still water. By
irJ. Gerritsma and W. Beukelman. September
1964.
63
C The mode of action of anti-fouling paints: InteracM
64
C
65
S
66S
67S
tion between anti-fouling paints and
A. M. van Londen. October 1964.
sea
water. By
71
S
77l.j
r965.
Experiments on vibrating propeller models. By
R. \À'ereldsma. March 1965.
Research on bulbous bow ships. Part
performance of a
large bulbous bow.
meren and ir J. J.
ir
79C
965.
Research on bulbous bow ships. Part I.B. The behaviour of a fast cargo liner with a conventional and with
a bulbous bow in a seaway. By ir R. Wahab. De-
cember 1965.
Comparative shipboard measurements of surface
temperatures and surface corrosion in air cooled and
water cooled turbine outlet casings of exhaust driven
marine diesel engine turbochargers. By prof. R. W.
cember 1965.
The pre-treatment of ship plates: A comparative
investigation on some pre-treatment methods in use
in the shipbuilding industry. By A. M. van Londen,
81
S
83S
84S
ing. December 1965.
The pre-treatment of ship plates: A practical investigation into the influence of different working
procedures in over-coating zinc rich epoxy-resin
based pre-construction primers. By A. M. van Londen, ing. and W. Mulder. December 1965.
The performance of lJ-tanks as a passive anti-rolling
device. By ir. C. Stigter. February 1966.
Low-cycle fatigue of steel structures. By ir J.
J. W.
Nibbering andJ. van Lint. April 1966.
Roll damping by free surface tanks. By ir J. J. van
den Bosch and irJ. H. Vugts. April 1966.
Behaviour of a ship in a seaway. By prof.
irJ. Ger-
ritsma. May 1966.
85S Brittle fracture of full scale structures damaged by
latigue. By ir J. J. W. Nibbering, J. van Lint and
R. T. van Leeuwen. May 1966.
86M Theoretical evaluation of heat transfer in dry cargo
ship's tanks using thermal oil as a heat transfer me87
dium. By D. J. van der Heeden. December
S
II.A. Still water
with
ir R. Wahab. October 1965.
Hull vibrations of the cargo-passenger motor ship
"Oranje Nassau". By ir W. van llorssen. August
Stuart Mitchell and V. A. Ogale. December 1965.
rneasurements of a cargo ship
with special afterbody. By dr ir R. Wereldsma. De-
82S
ir L. L. Mulder. March
P. A. van Katwijk. June 1965.
Research on bulbous bow ships. Part I.A. Still water
investigations into bulbous bow forms for a fast cargo
Iiner. By prof. dr ir W. P. A. van Lammeren and
78M Stern tube vibration
cember 1964.
lnvestigations into the strength of ships' derricks,
Part L By ir F. X. P. Soejadi. February 1965.
Heat-rransfer in cargotanks of a 50,000 DWT tanker.
By D.J. van der Heèden and
1 965.
ir F. V. A. Pangalila. June 1965.
in a vertically corrugated bulkhead. By prof. ir H. B. Jaeger and ir
Stress and strain distribution
1
76S
BOC
M Guide to the application of Method for calculation
of cylinder liner temperatures in diesel engines. By
dr ir H. W. van Tijen. February 1965.
69 M Stress measurements on a propeller model for a
42,000 DWT tanker. By ir R. Wereldsma. March
M
75S
diesel engines using heaw fuels. By prof. R. W.
Stuart Mitchell and V. A. Ogale. March 1965.
Barnacle fouling on aged anti-fouling paints; a survey ofpertinent literature and some recent observations. By drs P. de WoIf. November 1964.
The lateral damping and added mass of a horizon-
68
70
745
Corrosion in exhaust driven turbochargers on marine
tally oscillating shipmodel. By G. van Leeuwen. De-
Research on bulbous bow ships. Part II.B. Behaviour
of a 24,000 DWT bulkcarrier with a large bulbous
bow in a seaway. By prof. dr ir W. P. A. van Lam-
meren and
73S
senberg. June 1964.
Natural frequencies of free vertical ship vibrations.
By ir C. B. Vreugdenhil. August 1964.
proL
62
725
1963.
1966.
Model experiments on sound transmission from engineroom to accommodation in motorships. By Ir.
J. H. Janssen. December 1966.
a
n Lam-
Cornrnunications
1M Report on the use of heavy fuel oil in the tanker
"Auricula"
2S
3S
4S
5S
of the Anglo-Saxon Petroleum Company
(Dutch). August 1950.
mile (Dutch). By
Ship speeds over the measured mile
Februarv 1951.
195
ösingh. February
ir W. H. C. E. Rosineh.
ing ships and their analysrs
analysis
On voyage logs ofsea-going
of
(Dutch). By prof. irJ.
i
W. Bonebakker and irJ. Gerritsma. November 1952.
Analysis of model experiments, trial and service performance daTa of a single-screw tanker. By prof. ir
J. W. Bonebakker. October 1954.
Determination of the dimensions of panels subjected
to water pressure only or to a combination of water
pressure and edge compression (Dutch). By prof.
ir
6S
the effect of free sur-
7S
Herßt. April 1956.
On the calculation of stresses in a stayed mast. By
ir B. Burghgraef. August 1956.
BS
(Dutch). By
ir
L.
P.
load and compressive forces in the middle plane.
By ir B. Burghgraef. February 1958.
Review of the investigations into the prevention of
corrosion and fouling of ships' hulls (Dutch). By
ir H. C. Ekama. October 1962.
l0 S/M Condensed report of a design study for a 53,000
DWT-class nuclear powered tanker. By the Dutch
International Team (D.I.T.), directed by ir A. M.
Fabery de Jonge. October 1963.
9C
l1 C
Investigations into the use of some shipbottom paints,
based on scarcely saponifiable vehicles (Dutch).
By A. M. van Londen and drs P. de Wolf. October
C
The pre-treatment of ship plates: The treatment of
welded joints prior to painting (Dutch). By A. M.
van Londen, ing. and W. Mulder. December 1965.
Corrosion, ship bottom paints (Dutch). By ir H. C.
12
C
Ekama. April 1966.
14 S lluman reaction to shipboard
13
Simply supported rectangular plates subjected to the
combined action of a uniformly distributed lateral
M : engineering department
S
:
1964.
shipbuilding department
vibration, a study of
existing literature (Dutch). By ir W. ten Cate. August
1966.
C
:
corrosion and antifouling department
U
16
+
rË-
E
€d
!
4
]T: =
I
E_
tl
r+
¡
4
T
I
I
L-t
T!
.:-
-l
-
:L
-1r
îh
+
:tt
rl¡j
.llf
L
#
F
il-
eti
+ EèI
:I
11:
la
L-
+
I
li
t
l1:1
h
lr:
Êl
nrt
:ll
-
:f
ft 3,
L1::
fr: +lt
l++
*I
!
I
+
Ér
Ë
ri
n:
ll:
Ê:
Ë
1+
it:t
1
È
I
t]
ll
¡f'
il-
nl ,+
l¿
qd
t:
¡ll
t_-. L
L:]
1
+
rl
ffi
Ð
ii: l.::
I
\
io;
,41-'
,,F
:il
{
.J
::t
E1
fl
*! :\.
I
E:
_j
l+
r:Ìå
\
r-5
lll
Itrl
rf:
È
l-l l:.n
d- Lll
i-
I
Iili
l-
ili
F.l
Itr
i:l
jl
il
I
l
J
I,ii E:
r1
l--
+
Ir
ll
l.i.
0
-1
Fi :i
r:-j
:II
0
-5
l
illl
:11l
IL
i.ll
!:rl
T
::+:
i!
ñ
r-
FJ
:l
ï
F
t:
:rE
lil
I
f,
tr
l
++
+;
Ê
ll
;+
10
]]l
r+-
J
s
t=
=2
I
12
,-l
L:I
d
r+:
EI
t_
rf, r rl-
't
ll
+-
l-
ú,
:l-l
l:;
r+r
-+
I
1
lT:l
14
I
I
Ê
l+
I
I
il
l::j
I
'JI
L
,l
iLl
I
t_
il
IJ
ll
Ìr
H
.J
:l
ii
l:
il.l
l!
lii
l0
15
I
I
J
20
L
25
---------------*
Fig. 1 }Ieat transfer coefficient for free flow along a vertical wall.
t*"il
(oc)
Fig.
50
2 lleat
00
'150
transfer coefficient for free laminar flow around horizontal pipes.
I