REPORT No. 198M
December 1974
NEDERLANDS SCHEEPSSTUDIECENTRUM TNO
NETHERLANDS SHIP RESEARCH CENTRE TNO
ENGINEERING DEPARTMENT
LEEGHWATERSTRAAT 5, DELFT*
MARITIME TRANSPORTATION
OF CONTAINERIZED CARGO
PART IV
EVALUATION OF THE QUALITY LOSS OF TROPICAL PRODUCTS
DUE TO MOISTURE DURING SEATRANSPORT
(CONTAINERVERVOER PER SCHIP)
DEEL IV
(EVALUATIE VAN HET KWALITEITSVERLIES VAN TROPISCHE PRODUKTEN
TEN GEVOLGE VAN VOCHT TUDENS HET ZEETRANSPORT)
by
ING. P. J. VERHOEF
(Central Technical Institute TNO)W. N. BESSEM P. CADEE J. DE NEEF
IR. A. DE Moor (ex officio)
Het vervoer van containers per schip is de laatste jaren sterk
toe-genomen. Gesteld mag worden dat het van "huis naar huis"
transport-systeem geleid heeft tot een extra complicatie, nl. het voorkomen van schade aan de containerlading ten gevolge van vocht. Dit mag worden toegeschreven aan het feit dat de lading met cen veel grotere snelheid dan vroeger het geval was, gebieden passeert, die uit klimatologisch oogpunt zeer verschillend kunnen zijn. Tevens vindt vervoer plaats in landklimaten met grotere en meer frequente temperatuurwisselingen dan het geval is in een zeeklinuat.
Het is duidelijk dat kennis en ervaring met deze wijze van ver-voer muet worden opgebouwd terìeinde schadeclaims te voor-komen en nieuwe projecten op hun mogelijkheden te toetsen. Wat dit betreft wordt ernaar gestreefd orn door een combinatie van eenvoudige laboratorium experimenten en gedetailleerde met de computer uitgevoerde berekeningen het risico van vochtschade te evalueren.
Voor een eerste verkenning van de problematiek zijn praktijk-experimenten verricht waarvan de resultaten zijn vermeld in de rapporten 149 M en 151 M.
Als oorzaken van vochtschade kunnen worden aangemerkt: vocht dat met de lading in de container gebracht wordt en bet transport van vocht in de lading als gevolg van tempera-tuurverschillen.
Het verminderen van bet vochtgehalte door droging alvorens
de lading in de container te brengen of de migratie van vocht in de lading te verhinderen door eliminatie van de hieraan ten grond-slag liggende motorische krachten, zijn maatregelen, die de kans op vochtschade reduceren.
Ten aanzien van een theoretische evaluatie van de
vochtmigra-tie dient nog een aantal factoren gekwantiflceerd te worden. Hierbij wordt gedacht aan de randcondities van de container
en de stofconstanten (by. diffusiecoëfficiënt, soortelijke warmte) van het vervoerde produkt.
In het onderhavige rapport is als eerste benadering van dit
probleem aan de hand van praktijkmetingen een methode
opge-steld waarmee de ruimtemperatuur berekend kan worden als
functie van de temperaturen in aangrenzende ruimten en omge-ving. Daarnaast zijn in bet laboratorium van een aantal tropische produkten de vochtgchaltes bepaald, terwijl van groene koffie tevens o.a. de biologische activiteit werd vastgesteld.
Tevens werden procfverschepingen met groene koffie uitge-voerd. Geconcludeerd kon worden dat groene koffie geen vocht-schade zal oplopen indien de relatieve vochtigheid van de lucht op elke plaats in de lading beneden 78% wordt gehouden.
Tijdens deze proefverschepingen bleken de gemeten en bere-kende ruimtemperaturen een goede overeenstemming te vertonen.
Een meer gedetailleerd onderzoek inzake warmte- en vocht-transport zal echter gewenst zijn teneinde algemeen geldende
regels vast te stellen.
NEDERLANDS SCHEEPSSTUDIECENTRUM TNO
The transport of containerized cargo by ship has increased to large extent over the past few years. lt may be stated that this
kind of transportation system has resulted in a complication viz. the occurrence of cargo damage due to moisture. This may be attributed to the fact that cargo is nowadays being transported with much higher speeds through areas that are quite different from a climatic point of view. Furthermore transportation routes lead through continental climates having much greater and more frequent temperature fluctuations than is the case with oceanic climates.
It will be clear that knowledge and experience with this trans-portation system must be built up in order to prevent claims for damages and to evaluate the possibilities of new projects.
When combining simple laboratory experiments and detailed computer calculations it is believed to have a powerful tool for evaluation of the damage risk due to moisture. In a first attempt to tackle the problem experiments on board ship have been car-ried out. Full details are given in our reports 149 M and 151 M. Damage due to moisture has two main causes viz.:
moisture present in the cargo at the time the container is
loaded
migration of moisture in the cargo due to temperature differ-ences.
Decreasing the moisture content by drying the cargo before it is loaded in the container or preventing the moisture migration by elimination of the motory forces are both measures which reiuce the risk of moisture damage.
For a theoretical analysis of the moisture migration some fac-tors have to be quantitatively known like the boundary condi-tions of the container and the physical data (diffusion coefficient, specific heat) of the product.
The underlying report presents a mathematical model with which the hold temperature can be calculated as a function of
the temperature in adjacent spaces and surroundings.
Besides, the moisture content of a number of tropical products
have been determined in the laboratory whilst the biological activity of green coffee has also been determined. Also some
experimental shipments of green coffee have been carried out. It could be concluded that green coffee will not suffer from moisture damage if the relative humidity of the air anywhere in
the cargo is kept below 78. During these shipments the mea-sured and calculated hold temperatures closely
fit. A more
detailed investigation into heat and moisture transmission will be necessary to arrive at rules of general validity.
NETHERLANDS SHIP RESEARCH CENTRE TNO
page
List of symbols
6Summary
71
Introduction
72
Calculation method for predicting hold temperatures
82.1
Introduction
82.2
Description of the calculation model
82.3 Application of the calculation model to m.s. "Toledo"
102.4 Application of the calculation model to m.s. "Ceres"
Il3
Experiments on a laboratory scale
123.1
Introduction
123.2
Sensitivity to mould in green coffee
123.3
Biological activity of green coffee
123.4 Sorption-Isotherms of green coffee
123.5
Moisture content of green coffee from several shipments
123.6 Moisture content of several tropical products
124
Experiments on board ships
134.1
Introduction
134.2 Measurements on board ms. "Toled&'
I 34.3 Measurements on board m.s. "Ceres"
154.4 Measurement of the relative humidity in the bags after arrival.
165
Interpretation
I 65.1
Accuracy of the calculation model for predicting hold temperatures
165.2
Results of experimental transportation
186 Conclusions 18
7
Literature
19A B cp
E
K
Q V o QLIST OF SYMBOLS
area
latitude
specific heat
E is determined by: cos E
- tan B.tan O
fraction of side-wall area
of
hold section 3, which
sea levelheat flow
heat flow from the sun per square meter
see Chapter 2.2
coefficient
of
heat transmission
declination of the sun
coefficient of heat conduction in deeptank
flow of
ventilating air to the sections of the hold
specific weight [m2] [degrees] [i / kg. K] [degrees] is below[J/m2.s.K]
[degrees][J/m.s K]
[mi/s]
[kg/rn3]i
Introduction
The transportation of containerized cargo is often
ac-companied by the serious risk of damage due to
mois-ture. The primary cause of this is that in every cargo a
certain amount of water is shipped, first in the air
around the cargo parts, secondly within the cargo
it-self, if this has a hygroscopic nature.
As the absolute moistUre content of the air is very
low, experts generally consider the humid air harmless,
so that moisture in cargoes remains the primary factor
causing the trouble. lt should be emphasised that in
this context not only the goods taken from one place
to another have to be regarded as cargo, but also
aux-iliary materials such as packing materials, dunnage
woods and so on. It is found that these materials often
play a role in the moisture damage problem. The
second cause of moisture damage in the cargo lies in
the migration of water due to temperature differences
in the cargo.
It is clear that it is necessary to eliminate these causes
in order to get rid of the moisture problem. Thus,
removing the water or lowering the water content of
cargoes by drying is a method to eliminate or reduce
the risk of damage.
Another method is preventing the water molecules
to migrate, either by using vapour barriers (e.g. by
packing goods in plastics bags) or by eliminating the
driving forces for the transport of water by ensuring
a uniform temperature distribution in the cargo
(ree-fers).
MARITIME TRANSPORTATION OF CONTAINERIZED CARGO
PART iV
EVALUATION OF THE QUALITY LOSS OF TROPICAL PRODUCTS
DUE TO MOISTURE DURING SEATRANSPORT
by
Ing. P. J. VER HOEF
Summary
Problems concerning quality loss due to moisture in coffee during seatransport are being investigated. The investigations include a theoretical study into the course of hold temperature as a function of the course of outside-temperature, laboratory work on product properties and experiments on board ships.
The experiments on board ships have been made on board m.s. "Toledo', on her voyage from Singapore to Rotterdam in December 1972, and on board m.s. "Ceres", on her voyage from Colombia to Amsterdam in February 1973.
The theoretical study has produced a calculation model for hold temperatures that closely fits the measurements on board ships. The experiments in laboratories and on board ships have yielded a number of product properties that play a role in the moisture prob-lem and have resulted in some measures that reduce the risk of moisture damage.
The experiments give the impression that moisture transport in bulk coffee is a very slow process, and that the problem of moisture damage seems to originate in the interactions between the stowage surface and the surroundings, on the assumption that the product
has a good initial quality and a low initial moisture content.
For the migration of water vapour two mechanisms
exist: diffusion and convection. Diffusion occurs in
stationary air; it is a relatively slow process. When the
vapour molecules are transported by the sweeping
action of an air stream, the moisture moves rather fast;
this is called convective mass (water) transport. To get
the latter type of water movement it is necessary that
there is enough open space in the cargo for air streams
to be generated. The driving force for these air streams
can be temperature differences (free convection), but
the air can also be forced through the cargo by a fan.
lt has been stated above that preventing water
mi-gration partly eliminates the problem, and for this
reason water movement by diffusion, which is a slow
process, is to be preferred to transport by convection,
so that from this point of view air circulation in cargoes
must be avoided.
There is, however, another aspect that has to be
considered, namely the transfer of heat in the cargo.
Heat transfer is effected by about the same transport
mechanisms as water vapour migration: conduction
and convection. Conduction is relatively slow, whereas
convective heat transfer by air streams is much faster.
To reduce the driving forces for water transport the
temperature differences in the cargo should be as small
as possible, which can be achieved by stimulating heat
transport. From this point of view it follows that the
air circulation in cargoes must be promoted.
When this conclusion is compared with the earlier
mentioned conclusion, the picture appears rather
con-fusing. To get a better knowledge of the rather difficult
8
problem of the simultaneous heat and moisture
trans-port in cargoes, and to be able to provide practical
recommendations for transporting products, further
investigations have to be carried out.
It should be kept in mind that the above-mentioned
phenomena are not restricted to containerized cargo
only, but also apply to holds of conventional ships. The
reason for explicitly dealing with these problems in
containers is that the ratio of heat and moisture
trans-fer in containers often diftrans-fers quantitatively from that
in the holds of conventional ships.
The purpose of the experiments described in this
report is to collect data that can contribute to solving
heat- and mass-transfer problems in cargoes.
2
Calculation method for predicting hold temperatures
2.1
Introduction
The water-vapour pressure above a product depends
on the nature of the product, its moisture content and
temperature, if
it has a hygroscopic nature. Thus,
temperature differences in a cargo, may result in
water-vapour
pressure
differences, whichrepresent
the
driving force for watervapour migration. Temperature
differences in cargoes are caused by changes in climate
during the voyage.
In order to investigate how the temperature in the
cargo is affected by the climate, the relation: change
in climatic conditions to change in hold temperature
has been investigated theoretically and experimentally.
At a later stage the relation change in hold temperature
to change in temperature distribution in the cargo
should be investigated.
103 Al
In order to predict the course of hold temperatures
as a function of the climatic conditions, a calculation
model has been developed. The model is a schematic
representation of reality, which enables a mathematic
approach of the physical problems. Although the model
applies to ships with four decks, it can also be used for
three-, two-, and one-deck ships.
Based on this calculation model a computerprogram
has been made.
2.2 Description of the calculation model
The calculation model presented graphically in Figs.
I and 2 consists of one deeptank and four
superim-Fig. I. Sketch of ship's longitudinal section on behalf of the
calculation of hold temperatures.
1011 0110 0<18 T A 12 0g 0<9 016 o5 01 3 0114 Tg A1<. Ai 0119 1 20 T A 014
} LA
sen level}
Fig. 2. Sketch of ship's cross-section on behalf of the calculation model of hold temperatures. *1 ventilation) 020 013 lolot radiatton) A 10 0<25 T12 26
T11 -0.
o<19 01<. 102L2
sedtior 1 021 p Q-0 I Ois 4g 1011 412 0110 _- 0 g section2 0.OoO 0117 018 83 0g Ois 0(9 A13 As Tg__... Q section3 0.0 0 0< 15 aiS Q 7 o<6 o(5 T8 section 4 0.0 0 0< 13 0<14 Qig 02 0(4 deeptonk Sd Od 3 Ag 012 Sedaniti
0112 0<21 0 15 08 T 07 cc 12 0<21 section 2 12 010 A 07 12 1<24 45 sect ion 3 T3 1< 23 019 05 section C T 01e 0101 venlIotlortl 020 013 solar rodatnl
T 12 AiD 0<25
/
014 dveptnk 8(3 tor°
¶05 26 0 21Table I. Symbols and numerical values for calculation of hold temperatures
posed parts of the hold. These sections are enclosed by
walls, which will he considered as system boundaries.
Heat flows perpendicular to the cross-section will be
neglected, unless a section is situated near a room with
much deviating temperatures (e.g. an engine room).
In Figs. 1 and 2 the parameters that play a role in the
calculations are indicated. The various symbols are
given in Table I.
At stationary conditions the heat flows to each
sec-tion of the hold must equal the heat flows from each
section. This yields the following equations:
hold,sectionl:Q11+Q12+Q14+Q15+Q21=O (2.1)
Q8+Q10+Q9+Q16
= Q11 (2.2)Q5+Q7+QtT+Q6+Q19 = Q8
(2.3)Q1+Q3+Q4+Q18 = Q5
(2.4)deck:
Q20+Q,1 = Q13
(2.5)The relations for the calculation of Q1 to Q21 are
given in Table 2. Combination of relations (2.1) to
(2.5) gives five equations with the five variables T1, T2,
T3, T4 and
T12.Based on the calculation model given in Figs. i and 2
a computer program has been made to solve the
above-mentioned five equations.
lt computes T1, T,, T3,
T4 and T12 as a linear combination
of
T5 to T12,
ac-cording to [1]:
T0C,tOCOfhUld = aT5+bT6+cT7+dT8+
eT9+»T10+gT11+hT12
(2.26)with:
a+h+c+d+e+f+g+/i =
The influence
of ventilation of the various parts
of
the
hold is included in coefficient b.
The magnitude of the various coefficients represents
the influence of the temperatures belonging to them.
The heat capacity
of
the cargo, which introduces a
time lag
of
the hold temperature, has been taken into
account by combining the temperature computed with
relation (2.26) and the temperature computed for the
day before, as follows:
of hold. actual = V 'ectionof hold, the day bcfore +
(1 - V)
Tectjoa of hold, relation(2.26) (2.27)If V = 1, the actually computed temperature of a
sec-tion
of
the hold remains constant, which means the
simulation of an infinite heat capacity of the cargo.
If V = O, the heat capacity of the cargo is zero.
A1,A 63 A14 A5 A6 AT A8 69 A10 11
Al2 A13 A14
2
(n
Velue for n.a. Toledo
Value for u.u. "Ceres" 300 465,96 11414 0 128 1465.96 115 290.140 128 465.96 102 0 300 1465.96 77 156.60 330 1465.96 68 52.95 614 0 29 97.07 96 0 Symbol 01 02 03 014 05 06 08 09 010 a 013 0114 015 016 017 018 019 020 021 023 0214 025 026
Value for n.a. "ToledO" Value for n.a. "Ceres"
1000 1000 1.75 1.75 0.31 0.31 0.414 0.144 0.61. 0.414 0.4!. 0.44 0.64 3.1414 0.414 32 32 2.3 2.3 2.3 2.3 2.25 2.25 2.25 2.25 2.2 2.2 2.2 2.2 1.75 1.75 1.73 1.75 1.75 1.75 0 1.73 0 1.73 32 32 0.414 0.41t Symbol 2 93 9 95 K
Value for n.a. "Toledo Value for n.a. 'Cerca"
5.23 7.17 1.19 4.3 1.58 0 0.7114 2.87 .75 0 -0.878
lo
Table 2. Relations for the calculation of Q1 to Q
1/a1 + d/A + . A,.(T5 - T7)
a1 e15 16 - e15 + e16 a2 + e214 e5. e9 - e5 + e9 a = e1 + a18 . A1
.(T10 -
T2) e12 .a22 lO e + e . A7 .(T6 - T2) 12 22 e10.e11+e
.A8. (T2-T1) 10 11 e12.e2 - 12 + e21 . A9 (T6 - T1) A114.(T8 - T14) - T3) A13.(T9 - T3) A5.(1 - K).(T6 - T3) A6.(T3 - T2) e 9.e20 = e1 + e . A11 .(T11 - T1) 9 20 = 2 c .(T6 - T1) Q16 = . p e2 .(T - T2) Q17 = . p c .(T6 - T3) Q18 = . p . c .(T - T14) 19 e1 + e23 K . A5 .(T5 - T3) Q20 = A10.(T12 -
T6) e26 . A10 . (T12 - T1)The deck temperature T12 is partly determined by
the heat flow from the sun to the deck
(Q13,relation
(2.5)). The average quantity of heat a ship's deck
recei-ves from the sun per m2 per second can he calculated
with:
(2.7)
B is the latitude in degrees. The value of B must be
taken positive for northern latitudes and negative for
(2.8)
southern latitudes.
The value of E can be calculated with:
(2.9)
cos E = tan Btan (5
(-70<B< +70)
(2.29)ô is the sun's declination. Table 3 shows the value of
(2.10)
ô for each month.
(2.11) Table 3. Declination of the sun
(2.12) january
21°20'
february13°20'
march- 21O'
(2.13) april+ 9°40'
may +18°50' june +23° (2.114) july +21°30' august + 14° september+ 30
(2. 15) october- 8°30'
novemberl83O'
december23
(2.16)Fig. 3 shows a cross-section of hold no. 5 of m.s.
(2.18)
"Toledo". The difference between the calculation model
and the hold of m.s. "Toledo" is the presence of the
cold storage rooms.
(2.19)
Application of the calculation model in this case is
possible by assuming the heat flows through the walls
(2.20)
of the cold storage room to be negligible, (by setting
a23 and a24 equal to zero, and by reducing A4, A6, and
(2.21)
A13 to the areas that conduct heat.)
The numerical values of the heat transmission
coefficients, wall areas, and ventilating air flows are
(2.22)
given in Table I.
The deeptank of hold no. 5 has been used for feed
(2.23)
water. During the ship's voyage from Singapore to
Rotterdam the bottom of the deeptank cooled due to
(2.214)
a change in sea-water temperature. As free convection
in the deeptank will probably not occur in this case,
the upper side of the deeptank will have had an almost
(2.25)
constant temperature. Calculation of the temperature
of the top of the deeptank resulted in a temperature of
29.6 C. The heat flow from deeptank to section 4 of
the hold (Fig. 2) was therefore calculated with:
a
Q3 (2.30)
-
a1 + e2 A3 .(T5 - T14) (2.6)q1
242(sin Bsin ôE+cos Bcos (5sin E)
(2.28)2.3
Application of the calculation model to m.s.
"To-Q13 = A10
-(2.17)
ledo"
insulation
T5
The temperature of the engine room has been
calcu-lated with:
room =
O.5(T5+T6)+ IO
with:
(Tengincroom 25) (2.31)
Relation (2.31) appears to give results that closely fit
reality.
2.4 Application of the calculation model to ms. "Ceres"
Fig. 4 shows a cross-section of hold no. 3 of m.s.
"Ceres". The difference between the calculation model
and the hold is the absence of sections 2 and 4 of the
0(21 Ag 012 A 0(2 A3 -Ql adiabatic - room cold_storogo, 20 021 2 section 1 05 section 2 06 A3 0<5 section 3
T
0(16 017 T5 ala 0(4 section 4 A5 o A1Fig. 3. Cross-section of hold no. 5 of ms. "Toledo".
/. 0<6 T, 17 T4 0(25 T7 3 5
Fig. 4. Cross-section of hold no. 3 of ms. "Ceres".
04
O
A14 0(13 T 15 in su lot ion 15hold. Application of the calculation model is possible by
giving A3 = A7 = Al2 = A14 the value 0, 0(4 = 0(5 =
0(9
to =
O, and by setting cP=
= OThe numerical values of the heat transmission
co-efficients, wall areas and ventilating-air flows are given
in Table I.
The deeptank of m.s. "Ceres" has been used for the
storage of heavy oil, in order to keep the oil at a low
viscosity its temperature was kept constant at about
27 °C. The heat flow from the deeptank to section 4
of the hold (Fig. 2) was therefore calculated with
relation (2.30). The temperature of the engine room
was calculated with relation (2.31).
20 13 A 11 0<10 udiobulic - room cold _storogel 13 L.. 1,7 A0 0(75
12
3
Experiments on a laboratory scale
3.1 Introduction
In order io collect product properties that play a role
in the moisture problem in cargoes, a number of
ex-periments have been carried out in several
TNO-laboratories.
3.2 Sensitivity to mould in green coflèe [2]
Samples of green Colombia coffee were stored during
21
days (transport time) at 25 °C in six closed boxes.
The relative humidity in each of these boxes was kept
constant by means of saturated solutions of salt in
water. Every day the pressure inside the boxes was
equalised to the pressure outside the boxes, so that
respiration (if any) could take place.
After storage the samples were sent to a taste panel
of the roastingfactory of"Douwe Egberts". The results
are given in Table 4.
Table 4. Results of storage tests with green coffee Storage period 21 days; Temperature 25 C
visual observations much mould much mould mouldy molLldy unchanged unchanged
This table shows that, after a storage time of 21 days
at 25 °C, there is an incipient quality loss due to mould
forming at relative humidities higher than 78%. In
general mould may start growing at relative
humidi-ties in excess of 70%, so that in case of long storage
times the relative humidity should be kept below 70%.
Mould creates its own micro-climate, so if there is
already some mould present in the cargo, then the
mould will grow even at humidities below 70%.
3.3 Biological activityof
green coff'eIn order to measure the biological activity of green
Colombia coffee, a number of samples were placed in
an apparatus to facilitate the measurement of both
the oxygen consumption and the ratio of carbon
dio-xyde emission relative to the oxygen consumed.
The experiments were made twice for five samples at
25 °C and 80 %R.H. From these experiments it
appear-ed that:
- The oxygen consumption by green
coffee was very
small, the largest measured consumption being
2 10_6 l/g coffee/day.
- The rates of carbon dioxyde emission to oxygen
con-sumption was about I. This means that the oxygen
consumed has been used for the conversion of
carbo-hydrates.
From the results of these experiments it can be
con-cluded that green coffee does not need ventilation as
far as respiration of the coffee is concerned.
3.4 Sorprion-isotherins
of
green coffte [3]Sorption-isotherms give the relation between the
rela-tive humidity of the air and the moisture content of the
product at stationary conditions. En order to determine
the sorption isotherms of eleven kinds of coffee, samples
of about 2 grams were stored during five weeks at 20 °C
at different relative humidities, which were kept
con-stant by means of saturated solutions of salt in water.
After five weeks of storage the moisture content was
measured by drying to constant weight. The samples
were also weighed during storage to ensure stationary
conditions (a constant weight of the samples indicates
a constant moisture content).
The results of the measurements are given in Table 5
(readings from graphs).
All samples stored at 85% RH. became mouldy
after 5 or IO days; this confirms the results of the
measurements described in Chapter 3.2.
Table 5. Results of measurements of sorption-isotherms
3.5 Moisture content
of
green coff'e from severalship-ments
In order to investigate how the moisture content of
shipped green coffee from several shipments develops
with time, the moisture content of a number of samples
was determined by drying and weighing.
The results of the measurements are given in Fig. 5.
3.6 Moisture content
of
several tropical productsMoisture contents of several tropical products were
determined in January 1972 and January 1973.
The results are given in Table 6.
coffee
moisture content (dry-weight basis) at
30% RH. 50% RH. 80%R.H.
I Peru coffee 5.8 8.0 17.6
II Honduras coffee 6.2 8.8 18.5
111 Guatemala coffee 5.8 8.4 18.8
IV Dominica coffee 6.0 8.5 17.6
V Costa Rica coffee 6.1 8.8 18.4
VI Colombia coffee 6.1 8.7 18.1
VII Equador coffee 7.1 9.9 20.0
VIII HaIti coffee 5.9 8.1 17.4
IX Nicaragua coffee 6.0 8.5 18.8
X El Salvador coffee 6.2 8.8 9.0
Xl Suriname coffee 5.3 7.0 16.5
relative
sample humidity
no. (%) results of panel
1 100 nasty 2 96 nasty 3 89.5 over-fermentation 4 85 over-fermentation 5 78 tolerable 6 71 tolerable
16 D 15 14 13 12 11 10
e9
67
6 QOct Nov Dec J00 Feb March Apr May Jorre JuLy
72 '72 72 " 073 073 073
- trme
Fig. 5. Moisture Content of samples of green coffee from several shipments.
Table 6. Moisture content of several tropical products
(dry-weight basis)
4
Experiments on board ships
4.1
Introduction
The purpose of the experiments on board ships was:
to determine the accuracy of the model for the
cal-culation of hold temperatures (described in Chapter
2)
- to verify the statement that green coffee does not
need ventilation
to verify the statement that no moisture damage
occurs if the relative humidity is kept below 78%
anywhere in the cargo.
samples received in
4.2
Measureme,its on board in.s. "Toledo"
In order to deteriiine the accuracy of the calculation
model measurements of latitude, seawater-, outside
air-, and hold temperatures were made. The results of
these measurements are given in Table 7.
Table 7. Observations of ms. "Toledo" 's crew mean temperature of
In order to verify the statements given in Chapter 4.1
ten plastic bags were filled with green coffee and coded
A to J. The bags were divided into five pairs. To four of
the five pairs different quantities of silicagel were added
to achieve different moisture contents in the various
pairs of bags. The method of calculating the quantity
of silicagel to be added to the coffee is given in
Appen-dix A. The bags were stored for three weeks to allow an
even moisture distribution in the bags. After storage
the bags were shipped to Rotterdam.
day no. date
outside air CC) seawater
(C)
section 4 of hold CC) latitude (degrees) 1 9/12 28.3 30 30.3+ 5
2 10/12 27.6 30 30.4+ 5
3 11/12 27.6 30 30.0+ 5
4 12/12 27.3 30 30.7+ 6
5 13/12 31 30 32.0+ 6
6 14/12 28.3 30 29.7+ 6
7 15/12 27.6 30 30.5+ 7
8 16/12 28.3 30 32.0+ 3
9 17/12 28.6 30 30.5- 3
lO 18/12 30.6 30 30.4- 8
19/12 28.6 30 30.3-12
2 20/12 27.6 30.6 29.9-12
13 21/12 29.6 29 30.0-13
14 22/12 29 28.6 30.0-20
15 23/12 27.6 28 29.7-24
16 24/12 24 25.6 28.2-28
17 25/12 23.3 25 27.0-32
18 26/12 24 22.6 26.7-36
19 27/12 21 21.3 24.9-36
20 28/12 21.3 21 24.3-30
21 29/12 23 21.6 24.9-23
22 30/12 24 23 25.5-16
23 31/12 25 25 26.7-lO
24 1/1 28.7 27.3 27.7- 3
25 2/1 28.3 29 29.! - 4 26 3/1 28.6 29.6 30.2 H-11 27 4/1 22.3 23 28.1 +17 28 5/1 19 20 26.0 ±23 29 6/1 18.6 19.6 25.0 ±30 30 7/I 16.6 18.3 24.3 +36 31 8/I 12.3 16.3 21.7 +43 32 9/1 11.6 16 20.2 +44 33 10/1 8.3 15.3 18.7 +45 34 11/I 9 13 16.7 +49 35 12/1 2.6 10.3 15.5 +53 36 13/1 2.3 5.3 12.9 +54 3714/1 - 3
3 10.3 ±54 38 15/1 2.3 3.3 11.3 +53 39 16/I 5 9 11.3 +52 Nutmeg in shell 8.2% 7.3%Nutmeg without shell 7.5% 5.9%
Black pepper 11.7% 10.3% White pepper 10.8% 20.1% Cassia (Vera) 11.3% Cassia (Java) 17.0-12.9% Cassia (China) 11.0% Tapioca 9.4% Tapioca flour 12.3% Coffee beans 10.1% Colombia coffee 9.1% Lombong coffee 9.8% Mace 6.7% Gum damac 0.3% Gum copal 0.3% s.m.r. Rubber 0.8% Crepe rubber 0.3% Sheet rubber 0.4% Shellac 2.3% Palm kernels 5.6% Copra 3.5% White wax 0.2%
14
port
Fig. 6. Location of the plastic bagswithgreen coffee on board m.s. "Toledo". OA DE DB DO Dc engine room Fig. 7a Fig.7b star board
Figs 6, 7, and 8 show the location
of
the bags during
transport. After arrival of the bags, the coffee and
sui-cagel were weighed and the moisture content
of
the
coffee was determined. Samples of each bag of
coffeewere sent to Douwe Egberts, where a panel tasted the
quality of the coffee.
The results of the experimental transportation are
given in Table 8.
Fig. 8a
Fig. 8b
Fig. 7. Location of plastic bags with green coffee on board Fig. 8. Location of plastic bags with green coffee on board
Table 8. Moisture conditions in bags of coffee during voyage of m.s. "Toledo" and quality of coffee after unloading
- The added silicagel contained 5% water. - The quality increases at increasing valuation.
Table 9. Observations of ms. "Ceres" crew mean temperature of
section
outside number 4
air seawater of hold latitude
day no. date (°C) (CC) (CC) (degrees)
- The silicagel added contained 5% (dry-weight basis) water. - The quality increases at increasing valuation.
4.3 Measurements on board m.s. "Ceres"
The measurements made to verify the calculation model
did not differ from the measurements on board m.s.
"Toledo". The results of these measurements are given
in Table 9.
In order to verify the statements given in Chapter
4.1 six plastic bags were coded K to P, and filled with
green coffee. The six bags were divided into three pairs.
To one bag of each of the three pairs 5.3 kg silicagel
was added. After sealing the bags were stored for one
week. Although one week of storage is probably too
short to achieve even moisture distributions, they were
shipped to Amsterdam. The bags had to be shipped
after one week because the next call of m.s. "Ceres"
would be several weeks later.
The location of the bags during transportation are
given in Figs. 9 and IO. The measurements taken after
arrival were the same as those after arrival of ms.
"Toledo". The results of the experimental
transpor-tation are given in Table IO.
bag, code quantity of sil icagel added (kg) quantity of coffee (kg) quantity of silicagel (kg) quantity of coffee (kg) moisture content of coffee (dry-weight basis) (%) relative humidity of air (%) quality index after unloading on departure on arrival A 0 43.3 0 43.3 12.5 67 2 B 1.6 40.5 2.14 40.1 11.0 65 3 C 3.4 43.9 4.50 44.8 9.8 60 5 D 7.4 46.3 9.50 44.2 7.1 40 4 E 12.8 38.5 15.50 35.8 4.l approx. 15 3 F 0 46.9 0 46.9 12.4 66 5 G 1.6 51.2 2.l2 50.7 12.2 66 2 H 3.4 43.0 4.35 41.6 8.4 52 2 1 7.4 45.8 9.50 43.7 6.9 35 4 .1 12.8 46.1 15.50 43.4 5.4 22 3 I 11/2/7327.3 24.5 28.0 5 2 12/2 27 26 28.0 8 3 13/2 26.7 28 27.5 12 4 14/2 28.3 26.7 27.8 14 5 15/2 26.5 27.2 27.3 17 6 16/2 25.2 25.7 27.3 22 7 17/2 22.8 23 26.8 25 8 8/2 20 20.5 25.5 31 9 19/2 17.8 18.8 24.1 34 lO 20/2 16.8 17.8 21.0 37 II 21/2 16.5 16 20.8 39 12 22/2 15.2 14.5 19.6 43 13 23/2 13.2 13 19.0 46 f4 24/2 13 11.5 18.7 47 15 25/2 7.7 10 16.0 49 16 26/2 3.7 8 5.0 53
Table 10. Moisture conditions in bags of green coffee during voyage of ms. "Ceres" and quality of coffee after unloading
bag, code quantity quantity of silicagel of added coffee (kg) (kg) quantity quantity of of silicagel coffee (kg) (kg) moisture content of coffee (dry-weight basis) (%) relative humidity of air (%) quality index after unloading on departure on arrival K 5.3 41.2 6.75 39.75 13.6 73 7 L 5.3 41.2 6.85 39.65 12.6 70.5 5 M 5.3 41.2 6.70 40.30 12 69 5 N 0 54.5 0 54.5 14.7 75 7
0
0 54 0 54 15.1 76 8 P 0 59 0 55 15.2 76.5 6port 16
Fig. 9. L.ocationofbags in hold of ms. "Ceres".
Fig. lOa. Bags K and N against the ceiling.
Fig. lOb. Bags M and P stowed in stowage centre.
Fig. IO. Locationofbags in the stowage on board ms. "Ceres".
4.4 Measurement of the relative hui;iidity in the bags
after arrival
in order to determine the moisture content of the
cof-fee, a number of samples out of each bag from both
shipments were examined. From the results it followed
that the moisture content of the coffee could differ
from place to place in one bag. This was confirmed by
repeated measurements of the relative huniidity in the
bags of m.s. "Toledo"s coffee three weeks after arrival.
As the bags had been stored for three weeks in a
starboard
room with almost constant temperature, it was
con-cluded that the water vapour transport in coffee bulk is
a very slow process.
5
Interpretation
5.1
Accuracy of the calculation model for predicting
hold temperatures
With the computer program based on the calculation
model given in Chapter 2, the course of hold
tempera-tures for both ships has been computed for various
values of V.
For both ships the computed results closely fit the
measurements for V = 0.2. These results are given for
e-30
Fig. Il. Seawater, outside air, calculated and measured hold
temperatures during the voyageofms. "Toledo".
u 30 20 10 20 lo O O 11-2.73 s 10 15 20
time of voyage (days)
Fig. 12. Courseofseawater, outside air, calculated and measur-ed hold temperatures during the voyage of ms. "Ceres".
indication teiiiperature courseof seawater
autside air section section
4at hold (calculated tar V
40fhald (measured) 0,2)
o-o-o-o--o
indication temperature courseof seawater
++ outsideair
-'----o- section 1 of hold (measured) section 4ofhoLd (calculated tarV0,2)
o
28 30 32 34 36 38 40 o--time ut voyage (days)
4 6 8 10 12 14 16 18 20 22 24 26
Numerical valuesofhold temperatures: (V = 0.2)
temp. temp. temp. temp. temp. temp. temp.
temp. open section 4 section 4 section 3 section 2 section I deck sun's
lati-day no. sea (°C) air (°C) cale, (CC) meas. (OC) caic. (-C) calc. (°C) cale.
(C)
calc.(C)
(W/m)heat tude (degrees) 1 30.0 28.3 29.0 30.3 28.7 28.7 29.1 34.7 209 5.0 2 30.0 27.6 28.8 30.4 28.6 28.6 28.9 34.1 209 5.0 3 30.0 27.6 28.7 30.0 28.4 28.4 28.8 34.! 209 5.0 4 30.0 27.3 28.6 30.7 28.3 28.3 28.7 33.7 206 6.0 5 30.0 31.0 29.1 32.0 28.9 28.9 29.3 37.3 206 6.0 6 30.0 28.3 29.1 29.7 28.9 28.9 29.2 34.7 206 6.0 7 30.0 27.6 29.0 30.5 28.7 28.7 29.1 33.9 203 7.0 8 30.0 28.3 29.0 32.0 28.7 28.7 29.1 34.9 214 3.0 9 30.0 28.6 29.0 30.5 28.8 28.7 29.1 35.7 230- 3.0
10 30.0 30.6 29.4 30.4 29.2 29.2 29.6 38.0 241 -- 8.0il
30.0 28.6 29.4 30.3 29.2 29.1 29.6 36.3 249-12.0
12 30.6 27.6 29.2 29.9 28.9 28.9 29.3 35.3 249-12.0
13 29.0 29.6 29.3 30.0 29.1 29.1 29.6 37.3 251-13.0
14 28.6 29.0 29.3 30.0 29.2 29.2 29.6 37.1 262-20.0
IS 28.0 27.6 29.1 29.7 28.9 28.9 29.4 35.9 267-24.0
16 25.6 24.0 28.2 28.2 28.0 28.0 28.5 32.4 271-28.0
17 25.0 23.3 27.4 27.0 27.2 27.2 27.6 31.8 274-32.0
18 22.6 24.0 26.8 26.7 26.6 26.6 27.1 32.5 276-36.0
19 21.3 21.0 25.8 24.9 25.5 25.5 26.1 29.5 272-30.0
20 21.0 21.3 25.0 24.3 24.8 24.8 25.3 29.7 272-30.0
2! 21.6 23.0 24.7 24.9 24.5 24.5 25.0 31.2 266-23.0
22 23.0 24.0 24.6 25.5 24.5 24.5 25.0 31.9 256-16.0
23 25.0 25.0 24.8 26.7 24.6 24.6 25.1 32.6 245-10.0
24 27.3 28.7 25.6 27.7 25.5 25.5 26.0 35.8 232- 3.0
25 29.0 28.3 26.3 29.0 26.1 26.1 26.6 35.0 215 4.0 26 29.6 28.6 26.9 30.2 26.7 26.7 27.2 34.7 195 11.0 27 23.0 22.3 26.1 28.! 25.9 25.9 26.3 27.8 176 17.0 28 20.0 19.0 24.8 26.0 24.6 24.6 25.0 23.8 156 23.0 29 19.6 18.6 23.7 25.0 23.5 23.5 23.8 22.7 131 30.0 30 18.3 16.6 22.5 24.3 22.2 22.2 22.5 20.0 108 36.0 31 16.3 12.3 20.7 21.7 20.3 20.3 20.5 14.8 81 43.0 32 16.0 11.6 19.2 20.2 18.7 18.6 18.9 14.0 78 44.0 33 15.3 8.3 17.3 18.7 16.7 16.7 16.9 10.6 74 45.0 34 13.0 9.0 16.0 16.7 15.3 15.3 15.4 10.8 58 49.0 35 10.3 2.6 13.8 15.5 12.9 12.9 13.0 4.0 44 53.0 36 5.3 2.3 11.8 12.9 11.0 10.9 11.0 3.6 40 54.0 37 3.0-3.0
9.4 10.3 8.4 8.3 8.3-1.7
40 54.0 38 3.3 2.3 8.3 11.3 7.3 7.3 7.2 3.7 44 53.0 39 9.0 5.0 8.0 11.3 7.0 7.0 6.9 6.5 47 52.0Table 11. Computed results for hold temperatures ms. "Toledo" Numerical valuesofcoefficients a to h
coefficient
belonging to coefficient
numerical values for: section 4 ofhold section 3 of hold section 2 of hold section I of hold
sea water a 9.62408E-02 2.78268E-03 369378E-05 1.31312E-06
outside air b .840281 .960836 .963161 .897862
deeptank c 2.08734E-02 6.03528E-04 8.01 132E-06 2.84799E-07
engine room d 4.22365E-02 1.22122E-03 1.62106E-05 5.76280E-07
engine room e 3.60888E-04 3.35088E-02 4.44802E-04 1.58125E-05
engine room f 1.03372E-05 9.59817E-04 3.31983E-02 1.18018E-03
engine room g 2.19237E-07 2.03564E-05 7.04087E-04 2.26475E-02
18
Table 12. Computed results for hold temperatures m.s. "Ceres" Numerical values of coefficients a to h from relation 12.6 are:
') The influence of coefficients e, f and g is negligible.
Numerical values of hold temperatures measured and calculated are: (V = 0.2)
temp. temp. temp. temp.
temp. temp. section 3 section 3 section 1 deck
seawater open air meas. cale. cale. cale. sun's heat latitude
day no.
(C)
(C)
( C) (DC)(C)
( C) (W/m2) (degrees)m.s. "Toledo" in Fia. Il and in Table il, and for ms.
"Ceres" in Fig. 12 and in Table 12.
lt is remarkable that the value of V, at which the
computed results fit the measurements best, is the same
for both ships.
5.2 Results
of
experimental Iransporta!iunFrom Tables 8 and 10 it follows that there is no relation
between the quality of the coffee and the relative
humi-dity of the air in the bags. This confirms the statement
that no moisture damage will occur if the relative
humidity is kept below 78%.
The good quality of the coffee in bags K to P
con-firms the statement that green coffee does not need
ventilation.
The poor quality of the coffee in bags A to J after
arrival is probably the result of a poor initial quality
of the coffee.
6 Conclusions
- Green coffee is not susceptible to damage by moisture
if the relative humidity of the air is kept below 78%
numerical values for
anywhere in the cargo, during a three-week voyage.
- Coffee does not need ventilation as far as respiration
is concerned.
- The calculation method developed for predicting the
temperature in the ventilated holds of both ships
during the voyage gives results that are in close
agree-ment with the hold temperatures measured during
the experimental shipments.
- With the normal ventilating rates on both ships the
ambient air temperature contributes to the hold
temperature for about 85%, which means that the
influence of the ambient air prevails as compared
with sunshine effects and seawater temperatures.
(coefficient b = 0.840281 for m.s. "Toledo", and
0.852283 for ms. "Ceres") (see Table Il and 12).
- The initial condition of the coffee has an overriding
influence. The impression is that coffee can he
trans-ported safely in closed plastic bags, presupposing a
good initial quality and condition of the coffee and a
carefull handling of the bags.
- Water vapour transport through bulk coffee is a very
slow process and any problems of moisture damage
to be due to moisture transport between the stowage
1 24.5 27.3 28.0 27.3 27.6 34.3 227 5 2 26.0 27.0 28.0 27.3 27.6 33.9 221 8 3 28.0 26.7 27.5 27.2 27.5 33.3 212 12 4 26.7 28.3 27.8 27.4 27.7 24.7 207 14 5 27.1 26.5 27.3 27.3 27.5 32.7 200 17 6 25.7 25.2 27.8 27.0 27.1 31.0 186 22 7 23.0 22.8 26.8 26.2 26.3 28.3 177 25 8 20.5 20.0 25.5 25.0 25.1 24.9 158 31 9 18.8 17.8 24.1 23.7 23.7 22.4 148 34 10 17.8 16.7 21.0 22.4 22.3 21.0 138 37 11 16.0 16.5 20.8 21.3 21.2 20.6 131 39 12 14.5 15.2 19.6 20.2 20.1 18.8 116 43 13 13.0 13.2 19.0 18.9 18.7 16.5 105 46 14 11.5 13.0 18.7 17.8 17.6 16.2 101 47 15 8.7 7.7 16.0 16.0 15.7 10.6 94 49 16 8.0 3.7 15.0 13.8 13.3 6.1 79 53
coefficient belonging to coefficient section 3 section 1
seawater a .102214 1.76142E-03
outside air b .852283 .953 199
deeptank e 1.94466E-02 3.35115E-04
engine room
d')
2.52432E-02 8.22347E-03surface and the surroundings; presupposing a good
initial quality and low moisture content of the coffee.
- A theoretical study should be undertaken into the
heat- and mass-transfer aspects of the problem to
arrive at more detailed results and conclusions of
general validity.
7
Literature
1. KNoBBouT,Ir. J. A., Maritime transportation of containeriz-ed cargo. Part [1. Experimental investigations concerning the
carriage of green coffee from Columbia to Europe in sealed
containers. Publication of the Netherlands Ship Research
Centre TNO, no. 149M, 1971.
KREUK, Ir. J. F. de en L. C. VAN DE LELLE Onderzoek naar de invloed van opslag, bij verschillende relatieve vochtigheden, op de smaak en de bepaling van de biologische activiteit van groene koffie. Rapport C.T.E.-TNO 72135.
TIMMERMAN, J. Bepaling dampdrukisothermen van elf
on-gebrande koffiesoorten (z.g. groene koffie) bij 20 °CELi C. Rapport I.V.V.-TNO, 123/69.
PERRY, J. H. Chemical Engineers' Handbook. Third Edition Mc-Graw-Hill Publishing Company Ltd.
20
Appendix A
Calculation method for the quantity of silicagel added
At stationary conditions there is a relation between the
water content of a hygroscopic product and the
(equi-librium) relative humidity of the surrounding air. This
relation is often given graphically (sorption-isotherms).
Sorption-isotherms are almost independent of
tem-perature in the range 20 to approx. 50 oc.
The partial water-vapour pressure above coffee can
be calculated by using sorption-isotherms and a steam
table. The partial vapour pressure above a hygroscopic
product at a certain temperature is the vapour pressure
of pure water at that temperature multiplied by the
equilibrium relative humidity at the moisture content
of the product.
Figure Al shows the partial vapour pressure above
Colombia coffee as a function of moisture content and
temperature. Colombia coffee has been supposed to be
representative also for Singapore coffee as far as the
sorption isotherm is concerned. A dotted line indicates
the use of the graph.
In the same way, such a graph has been made for
water vapour pressure
(mm. Hg)
10
5
silicagel (Fig. A2 [4]). [f coffee and silicagel are put
together in a closed space, the vapour pressures above
coffee and silicagel become the same after a certain
time. lt is now possible to calculate the dehydration of
coffee by silicagel at stationary conditions by making
use of Figs. A! and A2.
In order to illustrate the use of Figs. Al and A2, a
calculation of the quantity of silicagel to be added will
be carried out for an arbitrary case.
Problem:
50 kg of green Colombia coffee, with an initial moisture
content of l3% (dry-weight basis) must be dehydrated
to 8 %.The temperature is 30 °C. The quantity of
sili-cage! to be added to the coffee is to be calculated. The
initial moisture content of the silicagel is 5%.
Solution:
50 kg of coffee with I 3% moisture contains 100/113 x
50 = 44.2 kg pure coffee. To be removed from the
coffee (13-8)/lOO x44.2 = 2.21 kg water. The
water-vapour pressure above coffee of 8% moisture at 30 °C
moisture content
(dry _weight_basis) temp
1%) 1°c)
7
--q--
-3'7 -RH.1 9 5 1? 9 7 5 20 15 3,1.5 3,/.0 3,35 3,30 3,25 xlOli T (
[1g. Al Vapour pressure above Colombia coffee as a function of moisture content and temperature.
102
5 35
30
water vapour pressure (mm. Hg) 102 5 10 5
4-
4-3.45 40l/T (K)
is approx. 14 mm Hg. This equals the vapour pressure
above the silicagel after absorption of 2.21 kg water.
Fig. A2 shows that in this case the silicagel contains
28% water. The initial moisture content of the coffee
is 5%, so that the silicagel has adsorbed 28-5 = 23%
moisture content
(dry _weght_bosis)
1%)
Fig. A2 Vapour pressure above silicagel as a function of moisture content and temperature.
¿.0 35 30 25 20 15 10 8 temp.
(°c)
40 1 35 3:J 25 20 15of its dry weight. Then the quantity of dry silicagel to
be added to 50kg coffee is 100/23 x2.21 = 9.6 kg. As
the initial moisture content of the silicagel
is 5%,
1.05 x 9.6 = 10.09 kg silicagel, containing 5% moisture,
mLlst be added.PUBLICATIONS OF THE NETHERLANDS SHIP RESEARCH CENTRE TNO
LIST OF EARLIER PUBLICATIONS AVAILABLE ON REQUEST PRICE PER COPY DFL. 10.- (POSTAGE NOT INCLUDED)
M = engineering department S = shipbuilding department C = corrosion and antifouling department
Reports
i 14 S The steering of a ship during the stopping manoeuvre. J. P.
Hooft, 1969.
I 15 S Cylinder motions in beam waves. J. H. Vugts, 1968.
i 16 M Torsional-axial vibrations of a ship's propulsion system. Part I. Comparative investigation ofcalculated and measured
torsional-axial vibrations in the shafting of a dry cargo motorship.
C. A. M. van der Linden. H. H. 't Hart and E. R. Dolfin. 1968.
I I 7 S A comparative study on four different passive roll damping
tanks. Part II. J. H. Vugts, 1969.
118 M Stern gear arrangement and electric power generation in ships propelled by controllable pitch propellers. C. Kapsenberg. 1968. I 19 M Marine diesel engine exhaust noise. Part IV. Transferdamping
data of 40 modelvariants of a compound resonator silencer.
J. Buiten, M. J. A. M. de Regt and W. P. Hanen, 1968. 120 C Durability tests with prefabrication primers in use for steel plates.
A. M. van Londen and W. Mulder. 1970.
121 S Proposal for the testing of weld metal from the viewpoint of
brittle fracture initiation. W. P. van den Blink and J. J. W. Nib-bering, 1968.
122 M The corrosion behaviour of cunifer 10 alloys in seawaterpiping-systems on board ship. Part I. W. J. J. Goetzee and F. J. Kievits,
1968.
123 M Marine refrigeration engineering. Part III. Proposal for a specifi-cation of a marine refrigerating unit and test procedures. J. A.
Knobbout and R. W. J. Kouffeld, 1968.
124 S The design of U-tanks for roll damping of ships. J. D. van den Bunt, 1969.
125 S A proposal on noise criteria for sea-going ships. J. Buiten, 1969. 126 S A proposal for standardized measurements and annoyance rating of simultaneous noise and vibration in ships. J. H. Janssen, 1969. 127 S The braking of large vessels II. H. E. Jaeger in collaboration with
M. Jourdain, 1969.
128 M Guide for the calculation of heating capacity and heating coils for double bottoni fuel oil tanks in dry cargo ships. D. J. van der 1-leeden. 1969.
129 M Residual fuel treatment on board ship. Part III. A. de Mooy,
P. J. Brandenburg and G. G. van der Meulen. 1969.
130 M Marìne diesel engine exhaust noise. Part V. Investigation of a double resonatorsilencer. J. Buiten, 1969.
131 S Model and full scale motions of a twin-hull vessel. M. F. van
Sluijs, 1969.
132 M Torsional-axial vibrations of a ship's propulsion system. Part II. W. van Gent and S. Hylarides, 1969.
133 S A model study on the noise reduction effect of damping layers aboard ships. F. H. van ToI. 1970.
134 M The corrosion behaviour of cunifer-lO alloys in
seawaterpiping-systems on board ship. Part II. P. J. Berg and R. G. de Lange.
1969.
135 5 Boundary layer control on a ship's rudder. J. H. G. Verhagen.
1970.
136 S Observations on waves and ship's behaviour made on board
of Dutch ships. M. F. van Sluijs and J. J. Stijnman, 1971. 137 M Torsional-axial vibrations of a ship's propulsion system. Part III.
C. A. M. 'van der Linden, 1969.
138 S The manoeuvrability of ships at low speed. J. P. Hooft and
M. W. C. Oosterveld, 1970.
139 S Prevention of noise and vibration annoyance aboard a sea-going
passenger and carferry equipped with diesel engines. Part I.
Line of thoughts and predictions. J. Buiten, J. H. Janssen,
H. F. Steenhoek and L. A. S. Hageman, 1971.
140 S Prevention of noise and vibration annoyance aboard a sea-going
passenger and carferry equipped with diesel engines. Part li. Measures applied and comparison of computed values with
measurements. J. Buiten, 1971.
141 S Resistance and propulsion of a high-speed single-screw cargo liner design. J. J. Muntjewerf, 1970.
142 S Optimal meteorological ship routeing. C. de Wit, 1970.
143 S Hull vibrations of the cargo-liner "Koudekerk". H. H. 't Hart,
1970.
i44 S Critical consideration of present hull vibration analysis. S. Hyla-rides, 1970.
145 S Computation of the hydrodynamic coefficients of oscillating
cylinders. B. de Jong, 1973.
146 M Marine refrigeration engineering. Part IV. A Comparative stuyd on single and two stage compression. A. H. van der Tak, I 970. 147 M Fire detection in machinery spaces. P. J. Brandenburg, 1971. 148 S A reduced method for the calculation of the shear stiffness of a
ship hull. W. van Florsscn. 1971.
149 M Maritime transportation of containerized cargo. Part II. Experi-mental investigation concerning the carriage of green coffee from Colombia to Europe in sealed containers. J. A. Knobbout, 1971.
150 5 The hydrodynamic forces and ship motions in oblique waves.
J. H. Vugts, 1971.
151 M Maritime transportation of containerized cargo. Part 1. Theoretical and experimental evaluation of the condensation risk
when transporting containers loaded with tins in cardboard
boxes. J. A. Knobbout, 1971.
I 52 S Acoustical investigations of asphaltic floating floors applied on a steel deck. J. Buiten, 1971.
153 S Ship vibration analysis by finite element technique. Part Il. Vibra-tion analysis. S. Hylarides, 1971.
1545 Canceled.
155 M Marine diesel engine exhaust noise. Part VI. Model experiments on the influence of the shape of funnel and superstructure on the radiated exhaust sound. J. Buden and M. J. A. M. de Regt, 1971. 156 S The behaviour of a five-column floating drilling unit in waves.
J. P. Hooft, 1971.
157 S Computer programs for the design and analysis ofgeneral cargo ships. J. Holtrop, 1971.
158 S Prediction of ship manoeuvrability.
G. van Leeuwen and
j. M. J. Journée. 1972.
159 S DASH computer program for Dynamic Analysis of Ship Hulls. S. Hylarides, 1971.
160 M Marine refrigeration engineering. Part 711. Predicting the con-trol properties of water valves in marine refrigerating installations A. H. van der Tak, 1971.
161 S Full-scale measurements of stresses in the bulkcarrier m.v. Ossendrecht'. Ist Progress Report: General introduction and
information. Verification of the gaussian law for stress-response to waves. F. X. P. Soejadi, 1971.
162 S Motions and mooring forces of twin-hulled ship configurations. M. F. van Sluijs, 1971.
163 5 Performance and propeller load fluctuations of a ship in waves. M. F. van Sluijs, 1972.
164S The efficiency of rope sheaves. F. L. Noordegraaf and C. Spaans, 1972.
165 S Stress-analysis of a plane bulkhead subjected to a lateral load. P. Meijers, 1972.
166 M Contrarotating propeller propulsion, Part 1, Stern gear, line
shaft system and engine room arrangement for driving contra-rotating propellers. A. de Vos, 1972.
167 M Contrarotating propeller propulsion. Part
Il. Theory of the
dynamic behaviour of a line shaft system for drivingcontra-rotating propellers. A. W. van Beck, 1972.
169 5 Analysis of the resistance increase in waves of a fast cargo ship. J. Gerritsma and W. Beukelman, 1972.
170 S Simulation of the steering- and manoeuvring characteristics of
a second generation container ship. G. M. A. Brummer, C. B.
van de Voorde, W. R. van Wijk and C. C. Glansdorp, 1972.
172 M Reliability analysis of piston rings of slow speed two-stroke
marine diesel engines from field data. P. J. Brandenburg, 1972. 173 S Wave load measurements on a model of a large container ship.
Tan Seng Gie, 1972.
174 M Guide for the calculation of heating capacity and heating coils for deep tanks. D. J. van der Heeden and A. D. Koppenol, 1972. 175 S Some aspects of ship motions in irregular beam and following
waves. B. de Jong. 1973.
l76S Bow flare induced springing. F. F. van Gunsteren, 1973.
177 M Maritime transportation of containerized cargo. Part III. Fire
tests in closed containers. H. J. Souer, 1973. 178 S Fracture mechanics and fracture contro] for ships.
A. W. van Beck, 1973.
183 M Marine diesel engine exhaust noise. Part VII. Calculation of the acoustical performance of diesel engine exhaust systems. J. Buiten, E. Gerretsen and J. C. Vellekoop, 1974.
184 S Numerical and experimental vibration analysis of a deckhouse. P. Meijers, W. ten Cate, L. J. Wevers and J. H. Vink, 1973. 185 S Full scale measurements and predicted seakeeping performance
of the containership "Atlantic Crown". W. Beukelman and
M. Buitenhek, 1973.
186 S Waves induced motions and drift forces on a floating structure. R. Wahab, 1973.
187 M Economical and technical aspects of shipboard reliquefaction of cargo "Boil-off" for LNG carriers. J. A. Knobbout, 1974. 188S The behaviour of a ship in head waves at restricted water depths.
J. 1'. Hooft, 1974
189 M Marine diesel engine exhaust noise. Part VIII. A revised mathe-matical model for calculating the acoustical source strength of the combination diesel engine - exhaust turbine. P. J. Branden-burg, 1974.
190 M Condition monitoring, trend analysis and maintenance prediction for ship's machinery (literature survey). W. dc Jong, 1974.
191 S Further analysis of wave-induced vibratory ship hull bending
moments. F. F. van Gunsteren, 1974.
192 S Hull resonance no explanation of excessive vibrations. S. Hyla-rides, 1974.
193 s Wave induced motions and loads on ships in oblique waves.
R. Wahab and J. H. Vink, 1974.
194 M On the potentialities of polyphenylene oxide (PPO) as a
wet-insulation material for cargo tanks of LNG-carriers. G. Opschoor, 1974.
195 s Numerical hull vibration analysis of a Far East container ship. P. Meijers, 1974.
197 M Transverse vibrations of ship's propulsion systems. Part I. Theoretical analysis, S. Hylarides, 1974.
198 M Maritime transportation of containerized cargo. Part IV.
Evalu-ation of the quality loss of tropical products due to moisture
during seatransport. P. J. Verhoef, 1974.
199 S Acoustical effects of mechanical short-circuits between a floating floor and a steel deck. J. Buiten and J. W. Verheij, 1974. 200 M Corrosivity monitoring of crankcase lubricating oils for marine
diesel engines. L. M. Rientsrna and H. Zeilmaker, 1974. 201 S Progress and developments of ocean weather routeing. C. de Wit,
1974.
J. B. van den Brug and W. A. Wagenaar, 1969.
19 5 The computer programmes system and the NALS language for numerical control for shipbuilding. H. le Grand, I 969.
20 5 A case study on networkplanning in shipbuilding (Dutch). J. S. Folkers, H. J. de Ruiter, A. W. Ruys, 1970.
21 s The effect of a contracted time-scale on the learning ability for manoeuvring of large ships (Dutch). C. L. Truijens, W. A. Wage-naar, W. R. van Wijk, 1970.
22M An improved stern gear arrangement. C. Kapsenberg, 1970. 23 M Marine refrigeration engineering. Part V (Dutch). A. H. van der
Tak, 1970.
24 M Marine refrigeration engineering. Part VI (Dutch). P. J. G. Goris and A. H. van der Tak, 1970.
25 5 A second case study on the application of networks for pro-ductionplanning in shipbuilding (Dutch). H. J. de Ruiter, H.
Aartsen, W. G. Stapper and W. F. V. Vrisou van Eck, 1971.
26 S On optimum propellers with a duct of finite length. Part Il. C. A. Slijper and J. A. Sparenberg, 1971.
27 5 Finite element and experimental stress analysis of models of shipdecks, provided with large openings (Dutch). A. W. van
Beck and J. Stapel, 1972.
28 5 Auxiliary equipment as a compensation for the effect of course instability on the performance of helmsmen. W. A. Wagenaar. P. J. Paymans, G. M. A. Brummer, W. R. van Wijk and C. C. Glansdorp. 1972.
29 S The equilibrium drift and rudder angles of a hopper dredger
with a single suction pipe. C. B. van de Voorde, 1972.
30 S A third case study on the application of networks for production-planning in shipbuilding (Dutch). H. J. de Ruiter and C. F. Heij-nen, 1973.
31 S Some experiments on one-side welding with various backing
materials. Part I. Manual metal arc welding with coated
electro-des and semi-automatic gas shielded arc welding (Dutch).
J. M. Vink, 1973.
32 S The application of computers aboard ships. Review of the state of the art and possible future developments (Dutch). G. J. l-loge-wind and R. Wahab, 1973.
33 S FRODO, a computerprogram for resource allocation in network-planning (Dutch). H. E. I. Bodewes, 1973.
34 s Bridge design on dutch merchant vessels; an ergonomic study.
Part I: A summary of ergonomic points of view (Dutch).
A. Lazet, H. Schuffel, J. Moraal. H. J. Leeheek and H. van Dam, 1973.
35 S Bridge design on dutch merchant vessels; an ergonomic study. Part Il: First results of a questionnaire completed by captains, navigating officers and pilots. J. Moraal, H. Schuffel and A. Lazet, 1973.
36 5 Bridge design on dutch merchant vessels; an ergonomic study.
Part III: Observations and preliminary recommendations. A.
Lazet, H. Schuffel, J. Moraal, 1-l. J. Leebeek and H. van Dam, 1973.
37 5 Application of finite element method for the detailed analysis of hatch corner stresses (Dutch), J. H. Vink. 1973.
