REPORT No. 123 M
December 1968NEDERLANDS SCHEEPSSTUDIECENTRUM TNO
NETHERLANDS SHIP RESEARCH CENTRE TNOENGINEERING DPTME
LEEGHWATERSTRAAT 5, DELFTMARINE REFRIGERATION ENGINEERING
PART III
PROPOSAL FOR A SPECIFICATION
F A MARINE REFRIGERATING UNIT
AND TEST PROCEDURES
(SCHEEPSKOELTECHN]IEK)DEEL III
(VOORSTELLEN VOOR EEN SPECIFICATIE VAN EEN SCHEEPSKOELEENHEID
EN BEPROEVINGSPROCEDTJRES)
by
IR. J. A. KNOBBOUT
Senior Research Officer Central Technical Institute TNO
and
IR R. W. J. KOUFFELD
Research Officer Central Technical Instjtùte TNO
RESEARCH COMMITFEE
L. J. R. DE BOCK
IR. J. VAN HAASTERT
TH D H VAN HALDEREN
Fi. VAN HOLTEN IR. J. A. KNOBBOUT
J. P. H. RIKSEN
iii. F. N. DE RoÖY
-IR. C. VAN DER WEELE A. ZWÄRT
G. ZIJLSTRA
IR. A. rE Moo (ex officIo)
VOORWOORD
Descheepskoelinstal]atie, die tot tank heeft de temperatuur in de koelruimen Op een, afliañkelijk van bet produkt, constante waar-de te houwaar-den kan in drie hoofdwaar-delón worwaar-den onwaar-derscheiwaar-den tw: de koelmachine, het luchtciìcúlatië- en ventilatiesysteem en de isolatie. Het isgebruikeijk dat ontwerpeñ úitvoering van genoem-de hoofdgenoem-delen door verschillendè gespecialiseergenoem-de firma's wordt
vrzorgd.
Omdat de prestatie van de installatie niet alleth aThaiikelijk is van de prestaties van elk der componenten doch tevens van dó onderliñge aanpassing, zullen de ontwerpen op elkaar moeteñ worden afgestemd hetgeen betekent dat wederzijds eisen moeten
worden gesteld waarbij evenwel rekenmg gehouden moet
worden met de door de rederij en bouwwerf bepaalde economi sche- en technische grennen.
Het reäliseren van een optimaà.1 compromis wordt bemoeilijkt door de in het ontwerpstadium bestaande betrekkehjke onzeker heid inzake de capaciteit van de koelmachine en de waarde van de isolatie Omdat een onvoldoende prestatie van de koelinstal latie ernstige gevolgen kan hebben voor alle bu de bouw van het
schip betrokkenen wordt niet zelden een veiligheidsmarge in acht genomen door de componenten met overcapaciteit uit te voeren hetgeen uiteraard tot hogere mvestermgskosten leidt
Recente ontwikkehngen in de koeltechniek maken het mogehjk de koelmachine en dó isòlätie afzonderlijk te evalúeren.
Hierdoor is het mogelijk een isolatie die aan bepaalde ther
mische eisen voldoet te ontwerpen en de capaciteit van de
koel-machine in overeenstemming met deze eisen en die van de te vervoeren produkten vast te stellen hetgeen tot vermindering
van investeringskosten kan leiden.
Dit rapport is bedoeld als Izandleiding b het vaststellen van de eisen waaraan een als gedecentraliseerde unit gebouWde koel-machine moet voldoen en bu het ontwerp en de uitvoering van het beproevingsprogranima. Het pretendeert noch volledigheid noch een standaardbestek te zijn.
Het rapport heeft uitsluitend betrekking op de koelmachine
en kan derhalve niet op de gehele installatie worden toegepast.
NEDERLANDS SCHEEPSSTUDLECENTR!JM mio
PREFACE
The marine refrigerating system for keeping cargo spaces at a
constant temperature, dependent on the cargo, can be divided
into three main parts namely: refrigerating installation, the áiÈ circulation- and ventilation system and the insulatiOn.
It is common practice that the design and the construction of these mainparts is carried out by specialized firms.
Since the performance of the system not oniy depends on the
performances of the components but also on the matching of
same, the designs will have to fit in with each other, which means that mutual requirements have to be made, taking into account the economical-and technical limit set by the shipowner and the yar&
The realisation of an optimal compromise is made difficult by the uncertainty, regarding capacity of the refrigerating machine and insulation, existing in the design stage.
Since insufficient performance of the refngeratmg system may result in serious consequences for all concerned with the building of the ship, not seldom safety margins are used by designing the components with overcapacity, which will increase first costs.
Recent developments in refrigerating engineering enable to evàluãte the refrigerating machine and the insulation indepen-dently.
Therefore it is possible to design an insulation, meeting speci-fled requirements, and to determine the capacity of the refriger-ating rnächiñe in correspondence with these requirements and those of the cargo, which may result in a decrease of first costs. This report intends to be a guide-book for the specification of a decentralized marine refrigirating unit and the testing procedure. It does neither prótend completeness nor to be a standard spec-ification.
The report only deals with the refrigòrating unit and therefore it cannot be applied to the complete-system.
CONTENTS
i 2 page Summary . 7 Introduction '7Requirements the unit must satisfy 7
2.1 General requirements 7
2.2 Specifications of paits 8
22.1 Casing of the unit 8
2.2.2 Compressors 8 2.2.3 Condenser 9
2.24 Air cooler
9 2.2.5 Expansion valves 9 2.2.6 Refrigerant piping 9 2.2.7 Temperature control . 9 2.2.8 Fan 10 2.2.9 Oil pump 10 2.210 Filter drier 102.3 Control and safety instruments 10
2.3.1 Control instruments 10 2.3.2 Safety devices 10 2.4 Operation of unit 10 2.5 Quotation . . . 11 2.6 Included in delivery 11 2.7 Spare parts 11 3 Testingoftheunit
li
3.1 Type testingii
3.1.1 Test procedure 11 3.1.2 Required measurements 11 3.1.3 Accuracy of measurements 133.1.4 Facilities to be provided on the unit under test 13
3.1.5 Duration 14
3.2 Operating test 14
3.2.1 Test procedure 14
MARINE REFRIGERATION ENGINEERING
PART III
PROPOSAL FOR A SPECIFICATION OF A MARINE REFRIGERATING UNIT AND TEST PROOEDURES
by
Ir. J. A. KNOBBOUT and
Ir. R. W. J. KOUFFELD
Summary
Proposals are made regarding the specifications of a marine refrigerating unit. It is expected that if the design of a marine refrigerating unit is adapted to the principles of these proposals the installation can be optimized thus resulting in a decrease of first costs Furthermore test procedures for type testing äñd fòr an operational test are recommended.
i
htroductionA refrigerating unit is an installation embodying all the components, such as compressor, evaporator, condens-er and all the instrumentation and opcondens-erating equipment. It must be constructed and arranged in such a manner that it can be fitted in a ship as a unit ready for opera-tion. An air temperature set in the hold in advance must be mantaihed under given conditions without the crew's intervention. This means that in genéral the unit must not only be able to remove heat from the hold but must if necessary be able to supply heat to it. On the whole, there should be no need for any other work on board from making the necessary power and water connections etc. This means that the require-ments the unit has to satisfy must be stated as clearly as possible tö a contractor, and this necessitates clear specificatiOns. It is moreover necessary to test a com-pleted unit before installing it in the vessel. Two kinds of tests can be distinguished: a type test and an operat-Ing test.
A type test is that tO which at least every first unit of a new series ordered by the principal is subjected. Such testing is very detailed and its purpose is to as-certain whether the unit satisfies all the requirements of the specification.
Theoperating test is that which every unit undergoes. It is much shorter than the other, and its purpose is to ascertain by means of a few well selected measurements whether the unit satisfies the requirements of the spec-ification as closely as possible.
Both the principals and the contractor can of course propose modifications in the specifications and test
procedures and if both agree there is obviously no objection. there must, of course, be sound reasons for any modifications.
2 Requirements the unit must satisfy
2.1 General requirements
I. The unit must be able tó reach and maintain air temperatures in the hold of from ... °C to ... adjustable by stages of 0.5 °C.
As single stage compressors are preferable the attainable mi nimum air temperature depends on the type of refrigerant, for
instance: for R 12: 23 °C;
R 22: 34°C;
R502: 40°C.The set air temperature is to remain constant to ± 0.25 °C, measured in the suction duct or com-pressed air duct of the unit with a temperature gauge whose sensor has a thermal capacity of 10 kcal/°C. The sensor must be shielded from radia-tion.
The air temperature should preferably be controlled with a
reg-ulating valve in the compressor suction-duct controlled by a
pneumatic P añd I regulator.
The unit's net capacity at the lowest air tempera ture must be at least... kcal/h and at the highest air temperature at least
... kcal/h,
both at a
coolingwater inlet temperature of + 32 °C, when no moisture is deposited on the evaporator. The net capacity is defined as the quantity of heat extracted by the evaporator from the environ-ment less the capacity of the fan(s) requiredTfor air circulation as fat as they form part of the unit. The unit must be able to develop the maximum
8
capacity appropriate for any air temperature within the set limits without overloading the compressors' electromotors.
With the compressor(s) running, the unit's capa-city at any air temperature must be reducible to 0% without the suction pressure, measured at the compressor's suction side, falling below i atm. The capacity of the fan(s) should be:
Q
....
m3/h, whentp =
mm water columnThe outside dimensions of the unit are not to
exceed
x... . x..
mm and must moreover be adapted to the space availb1e for it as shown on the overall drawings.The refrigerant should be R.. . known under one of the following trade names:
freon frigen kaltron arcton
The condensation temperature is to be over 25 oc and below 40 oc.
The end compression-temperature measured in the pressure pipe immediately after the compressor must not exceed 130 °C.
The difference between the temperature of air from the hold and the evaporation temperature *) at the lowest air temperature and the appropriate maximum refrigerating capacity during storage must not exceed 5.0 oc.
If the cooling water temperature falls to 20 °C and the unit's ambient temperature rises to 40 °C, the unit's capacity under the conditions stated in i must not fall by more than 10%.
It must be possible to defrost the air cooler every 24 hours. The defrosting system must be able to defrost completely an almost fully frosted cooler within 2 hours at the lowest attainablé áir temper-äture (See also page 12). Defrosting must be started by a time switch; it must end automatically. It must also be possible to start it manually. It is difficult to define a fully frosted air cooler. If we take an evaporator however with 7 mm between the fins, 0.6 kg frost per in2 effective evap-orator surface seems acceptable.
The air cooler is to be defrosted with a perpetual defrosting system; with a view to heating the hold a system is preferable in which oil at 45° to 50 °C is fed through a coil fitted in the cooler.
The entire installatioñ is tó be constructed accord-ing to the regulations of the Classification Societies
S) The evaporation temperature is defined as the saturation
temperature at the arithmetical mean f the pressure before and after the evaporator.
and the Perishable Products Export control Board (P.P.E.c.B.).
The contractor must test at least one unit or have the same tested in accordance with the "type test" procedure mentioned in 3.1 and produce a certif-icate of this showing that the unit is satisfactorily. The other units are to be tested for operation as per 3.2. The contractor will nevertheless remain responsible for the unit's proper operation.
AIl the unit's moving parts must be replaceable and operational within 1 hour, either individually or in combination with other parts.
2.2 Spec ¡fication of parts
2.2.1 Casmg of unit
The part of the unit in which the cooling air circu-lates is to be provided with thermal insulation which must be water-vapour proof and airtight. The in-sulating value of the casing should be such that at the lowest air temperature inside the casing and an ambient temperature of 40 oc and a relative humi-dity of 50% no water vapour condenses on the
out-side.
The connection between the casing and the ventila-tors must be constructed so that there is no short circuit between the two ducts and no air can leak out.
All the unit's moving or adjustable parts are to be accessible. For instance, there might be an insulated door allowing access to the fan. It must be possible to exchange the fan complete via the door opening. The air velocity in this space must not exceed an average of 8 rn/sec over each cross-section of the air duct.
The unit must be provided with a number of devices for lifting and conveying, to permit both vertical and horizontal mvement.
The steelwork of the refrigerating units must be treated as follows:
The skin due to rolling and all traces of rust must be removed;
It must then be given 3 coats of epoxy paint. Where possible, supports must be made of stainless
steeL
2.2.2 Compressors
The unit may be equipped with one compressor, provided this complies, with the requirements of the Classificatión Societies. The maximum speed of the compressors is 1800 r.p.m.
The compressor must be equipped with suction shut-off and discharge shut-off valves and a strainer. The compressors must be fitted with automatic
sump heating and a device for preventing oil migra-tion from one compressor to the other(s).
The compressor and driving mechanism must be arranged so that their removal, and building in of a stand-by compressor or a compressor with driving mechanism requires a maximum of one hour. Make of compressOr:
2.2.3 Condenser
The unit may be equipped with one condenser pro-vided this complies with the requirements of the Classification Societies.
Type of condenser: shell and tube Materials: housing: steel
tubes: cupro-nickel tube plates: cupro-nickçl covers: al. bronze
or other materials as approved by the shipowners. Each condenser must be of such a capacity that it will contain the entire charge of refrigerant. The condensers must be equipped with a closable and easily observable level glass-and with a spring-loaded safety valve.
If a storage tank is used this must be able to hold the entire content of refrigerant and be equipped with closable and easily observable level glass. Both iñ the vapour supply pipe and in.the condensed refrigerant removal pipe a valve is to be fitted, the nominal bore Of the connection corresponding to the nominal diameter of the pipes-.
At the refrigerant side the condenser is to be pro-vided with -a vent and a filling valve. The minimum
- bore of the venting cock connection is to be: i".
In determining the dimensions of'the condenser a factor of must be allowed for the influence
of scale deposits.
Ifa water cóntrol valve is installed in order to meet the requirement that the condensation temperature must not fall below 25 °C, it must be possible to
shut off the connection between valve and refrig-erant side of the condenser.
The water inlet and outlet of the condenser or con-densers must be made so that the condenser can be cleaned at the waterside by removing only one cover. Valves and thermometers must be provided in the cooling water inlet and outlet;
In order to prevent vibration of the condenser tubes, these must be supported approximately every metre, but this must not affect the operation of the con-denser. The condenser must be provided with a bronze drain cock and a venting cock at the water
side.
Make of condenser:
Make of water control valve:
2.2.4 Air cooler
The unit must be provided with a finned air cooler consisting of at least two sections connected in parallel, each of which can be shut off.
The distance between the air cooler fins must be not less than 7 mm (if defrosting is not done daily
11 mm is required).
-The air cooler must be built to withstand a maritime atmosphere.
The air cooler is to be provided with a heated drip tray constructed so that defrost water, both from the air cooler and from other frosted-up- pipes runs off properly under all conditions and cannot be carried along by the airstream.
A non-return valve is to be fitted in the pipes for removing defrost water.
Make of coolers:
2.2.5 Expansion valves
Eaàh half of the air cooler is to be equipped with one thermostatic pressure-compensating expansion val-ve. Construction: unfianged joints between two valves with removable inside fittings Parallel to the thermostatic valve a manually operated control valve is to be fitted between two valves. The parts are to be fitted by nians of unflanged joints. Make of expansion valve:
2.2.6 Refrigerant piping
Piping and parts are to be connected with unflanged joints.
Material: in conformity with the requirements of the Classification Societies. The construction and assembly of the-pipes to be such that good oil return from air cooler to compressor is guaranteed and no oil pockets form.
The- suction pipe to be insulated preferably with plastic insulation, in such a manner that no con-densation occurs under engine room conditions as mentioned in 2.2.1 point 1.
2.2.7 Temperature control -
-The air temperature preferably to be controlled with a suction-pressure control operated with a P and I regulator whose sensor is in the return air duct/expelled air duct. The regulator's proportional
bandtobe:-
-adjustable between 50% and 200%.
The integration time to be: adjustable between O and 15 minutes.
It must be possible to set and read the desired tem-perature at the operating side of the unit.
lo
3. If a pneumatic control is eployed a filter is to be
built into the compressed air supply pipe before the control, collecting dirt particles 3 1u and bigger.
4 Make Of control:
It must be possible to open the control valve by hand. Care must be taken that no water vapour condenses in the control valve servomotor, prefer-ably by lowering the dew point of the control air to the lowest evaporation temperature.
Make of control valve:
2.2.8 Fan
The Q-H curve of the fan(s) to be such that the capacity does not fall more than 10% upon a pres-sure increase of 10% relatively to working poiñt. The fan(s) to be driven by one (two) variable-speed motor(s) in such manner that the ratio between maximum and minimum revolutions is 1.5. The fan(s) must be able to rotate both ways. Make of fan:
2.2.9 Oil pump
I. If hot thermal oil is used for defrosting the air cooler this can also be used for heating the hold. In this case the unit is to be equipped with an electric oil pump.
Type: a displacement pump with a safety device against excessive pressure.
Maximum permissible pressureS atm. The pump must be able to pump oil at 60 °C and a viscosity of. . .. cS at 60 °C.
2. Make of pump:
-2.2.10 Filter drier
1. Filter driers are to be fitted in the liquid pipes
between the condenser(s) and the expansion valves Make:
The dimensions of the filter driers to be such that nominal refrigerant piping connections are at least equal to the nominal dimeñsion of the connecting
liqUid pipe.
2. Design of ifiter drier: a valve to be fitted before and after the filter drier, so that the charge can be replaced and the filter cleaned.
The filter drier to have unfianged joints.
Parallel to the ifiter a closable by-pass to be fitted, likewise with unfianged joints.
2.3 Control and safety instruments (whére not already mentioned)
2.3.1 Control instruments
I. Manometers with a dial diameter of at least 100 mm for measuring:
compressor suction-pressure (for each compres-sor),
- compressor discharge-pressure (for each compres-sor),
- compressor oil-pressure (fòr each compressor).
2. Thermometers with a scale length of at least... cm per °C and a range of... °C to.... °C indicating temperatures in compression and suction air ducts, independently of regulator reading.
2.3.2 Safety devices Safety devices against:
- excessive discharge pressure on the compressor (for each compressor),
- too low a suction pressure on the compressor (for each compressor),
- too low an oil pressure (for each compressor). These safety devices to be fitted so as to undergo the least possible effect from mechanical vibration. An easily accessIble centralised gauge and meter system is tecommended.
2.4 Operation of unit (where not dealt with above) i, Operating devices (switches, regulators, etc.) all to be fitted at one side of the unit (the operating side). Regulation to be such that once a given air temper-ature is set the unit switches over as required from cooling to heating and vice versa.
A choice must be possible between automatic and nonautomatic defrosting of the evaporator. With automatic operation, the evaporator to defrost once every 24 hours by means of a time switch. Defrost-ing to end immediately the evaporator is 99% de-froste4. *) During defrosting, fan to stop; and to switch on again after end of defrosting 10 to 20 seconds after resumption of refrigeration. Initiation of defrosting by hand must also be possible. The electromotors to be capable of direct connec-
-tion to supply system and suitable for ... V and Hert2.
If two compressors are employed the other to start automatically if one stops.
The unit to be protected against faulty operation, such as switching on of fan during defrosting, etc. Manual switching over from one compressor to the other must be possible. -
-It must be possible to switch by hand from "Cool" to "Heat".
-Replacement of parts of tarting and control instal-lation to be simple and quick. Preference is given to a control panel self-contained in the unit and built up of pull-out trays or panels.
- quantity of defrost water when water is used for de-frosting,
- power required for electric defrosting when
ppli-cable,
- quantity and temperature of oil in case of defrosting with hot oil,
compressed air in case of pneumatiò control. If the unit is also suitable for heating a hold, it must also be possible to supply heat to the insulated space.
3. 1 .2 Required measurements
I . Maximum gross refrigerating capacity and ñet
refrig-eratiñg capacity (Cf. 2. I point. 3)
The gross refrigerating capacity is defined as the total quantity of heat removed by the refrigerating unit. This heat consists of the heat supplied electrically to the insulated space to which the unit is connected, transmission losses through the walls of this space and the power consumption of the fan.
The net refrigerating capacity is defined as the gross refrigerating capacity less the power for ventilation. The gross capacity has to be determined in order to assess the behaviour of the unit and the net capacity in order to verify the requirements of 2.1 point 3
The maximum gross capacity is to be measured at at least three air temperatures (in each case the highest and lowest temperatures at which the unit must be able to operate) and to be plotted as a graph with the gross capacity on the vertiôal axis, the evaporation temperature on the horizontal axis and the air temper-ature as the parameter. It is then also possible to read the temperature difference between air and refrigerant. The evaporation temperature is for this purpose defined as the saturation temperature belonging tò the arith-metical mean of the pressures before and after the evaporator.
Note: If an evaporator with a distributor has been fitted, it is necessary for the principal to notify the pressure drop across this distributor for various volumes of refrigerant flowing through.
During these tests, which are to be made for two hours after a stationary situation has also been main-tained for at least two hours, the following quantities must in any case be determined:
power supplied to the insulated space, power supplied to the fan,
mean temperature in the insulated space, mean temperature outside the insulated space, mean temperature after the evaporator, mean temperature in the air return duct.
In the air duct in which the señsor of the temper-ature regulator is fitted, tempertemper-ature fluctuations must also be measured.
11
2.5 Quotation
The quotation to include:
A design drawing showing all the components of the unit (and also inside and outside pipe
diam-eters).
When the specification permits a choice in certain cases, the choice is to be stated and the reasons therefore.
Maximum power consumption. Maximum cooling water consumption. Maximum air consumption.
Maximum oil flow (where applicable)
7 Dimensions and location of connections to air
dUcts.
Diameter and location of sea water pipes. Diameter and location of compressed air pipe for
regUlator.
Diameter and location of oil pipes.
Il. Diameter and location of defrost water disposal.
2.6 Supply to include: (included for reference) Drawings for installing unit on board the ship. Drawings for connecting unit to air ducts on the
ship.
Instruction manual with full description of unit, adjustment of components, control diagrams, wiring diagram, etc.
2.7 Spare parts
Spare parts included with the unit to conform to Clas-sification Societies' regulations.
3 Testing of unit
3.1 Type testing
As stated in the introduction, at least one unit of eYery new series is to be thoroughly tested. The purpose of this test is to ascertain whether the unit meets all the reqUirements of Section 2.
3 1.1 Test procedure
For carrying out the test the unit s to be put in an assembly able to prOvide the conditions to be investi-gate4. For this purpose the unit is to be connected to an iúsulated space from which it can extract a known quantity of heat. The space should be big enough to prevent the outfiowing air influencing the flow pattern in the suction duct. The test laboratory must of course possess all facilities for connecting the unit as in prac-tical conditions, for instance:
- the correct voltage and power,
12
Fig. 1.
must be capable of air_tight closure
This measurement is made with an instrument which causes a negligible pressure drop. For the requisite connections see .3.1.4 and Figure 1.
It is then possible to determine the volumetric -yiêld of the compressors, so that their proper operation can be judged. This measurement is also a check on measurement of the refrigeration load by means of electrical elements, provided the oil content is taken into account, while this method of capacity determination can also be used when the unit is not connected to a testing chamber. See also 3.2.2.
Reduced capacity (cf. 2.1 point 5).
The operation of the unit must be investigated at the minimum capacity for which it has to be suitable according to the specifications, at three air tempera-tures; two of these to be the highest and lowest working temperatures. The same quantities as in 3.1.2 point i
are now also measured, with the exception of (u). Extreme conditions (Cf. 2.1 point 11)
At an air temperature at which the maximum gross refrigerating capacity is determined but not the highest or lowest temperature, the cooling water inlet temper-ature is lowered to ± 20 oc and the unit's ambient temperature increased to + 40 °C. The maximum gross capacity now to be measured must not be more than 10% below the capacity meásured in accordance with 3.1.2 point 1.
Defrosting of air cooler (Cf. 2.1 point 12)
Defrosting of the air cooler must be tested. It must first be frosted under the following conditions:
A cylindrical, stainless steel temperature sensor is to be used for this. Its diameter is to be 10 mm, its length at least 50 mm. The temperature is measured at the cylinder's geometrical centre.
compression end-temperature, measured immedi-ately after the compressor(s),
temperature at the inlet end of the compressor(s), temperature of the liquid after the condenser(s), or after the liquid tank, if any,
pressure before the expansion valves, temperature before the expansion valves,
I. suction pressure of compressor(s),
oil pressure of compressor(s), discharge pressure of compressor(s), pressure in condenser(s),
pressure at inlet side of each, evaporator or evapo-rator section,
pressure at outlet side of each evaporator or evapo-rator section,
quantity of cooling water,
cooling water inlet temperature. It must be possible to keep this constant at 32 °C,
cooling water outlet temperature,
mean air velòcity in the air return duct. From this the "output" of the fan can be calculated.
y. refrigerant circulation.
As stated, the uflit's refrigerating capacity is deter-mined by measuring the quantity of heat added to the air cooled by the unit. It is. also possible, however, to calculate refrigerating capacity from refrigerant circu-lation and the increase in enthalpy of the refrigerant in the evaporator; This measurément has many advan-tages besides those already mentioned.
Verification of measurement already mentioned. This measurement can be used to determine the capacity of units only undergoing the operäting test described in 3.2, as the unit is not then connect-ed to an insulatconnect-ed space.
It can be used to determine the capacity of a unit already located on board a ship. It is then readily possible, for instance, to ascertain the volumetric yield of the compressor of a unit already in opera-tion for some time.
This measurement can very simply be extended by measuring the quantity of oil circulating in the refrigerant.
If this measurement is to have any purpose and be comparable with that mentioned earlier, its accu-racy must be of the same order of magnitude. A degree of accuracy obtainable and necessary with the earlier mentioned method is ± 5%. In order to achieve this with the second method, refrigerant circulation must be measured to an accuracy of
- capacity about 50% of maximum,
- air temperature 2 oc,
- moisture applied by means of superheated steam at a constant velocity (kg moisture per hour) so that the relative humidity dóes not exceed 99%,
- moisture is supplied until a frost thickness gauge, if available, indicates that the cooler requires de-frosting, or otherwise until about 0.6 kg frost has deposited per m2 effective cooler surface.
Defrosting takes place at the lowest attainable air temperature.
During defrostirig, measurements are made of: quantity of defrost water collected as a function of time,
- temperature of defrost water,,
- quantity of heat supplied for defrosting,. i.e.: for electric defrosting: the electrical power, for water defrosting: quantity and temperature
of "warm" water supplied,
for hotoil defrosting: quantity and temper4ture of incoming and outgoing oil.
Defrosting must be completed in not more than two hours. The criterión for completion of defrosting is the time at which 99% of the frost has been collected from the evaporator.
At that time there must be no more frost on the evaporator and there must be no surplus water left in the drip tray and the discharge pipes. In order to know how much 99% of the water ultimately to be collected is, the defrosting process must be continued until at least 10 seconds has elapsed between collection of two drops of water in a measuring glass placed under the defrost water outlet pipe.
Check on lubricating oil
In order to judge whether no difficulties occur with oil circulation even after a longer period of time, the unit must be tested for at least 48 hours under the most unfavourable conditions of oil circulation.
These conditions are established by the supplier, customer and the laboratory making the test unless either supplier or customer make the test themselves. Oil level and oil pressure are now checked regularly. The oil pressure must remain at least 0.5 kg/cm2 higher than the suction pressure unless the compressor manu-facturer stipulates to the contrary.
The conditions under which the most unfavourable conditions occur regarding oil return depend so much on the design of the unit (oil separator, refrigerant, control, etc.) that it is impossible to prescribe them specifically).
Checking safety devices and circuits
The high, low and differential oil pressure pressostats must be tested. Any electricál safety devices must be
checked wherever possible. The arrangement of various parts of the unit must be compared with the specifica-tion.
Check on cleanliness of the installation
In order to judge the cleanliness of the installation the filter in the liquid pipe must be removed and if neces-sary cleaned before, half way through and after testing. The amount of dry dirt is measured which has collected between commencement and completion of the test. The weight of dry dirt is defined as its weight after washing with tiichlorethylene followed by drying. (This quantity of dry dirt should not exceed i gramme per 10 m2 evaporator surfàce).
3.1.3 Accuracy of measurements
The accuracy of the measurements should be as follows:
refrigerating capacity
±5%
temperature in general ± 0.2 oc end compression-temperature ± 5 oc discharge pressure ± 0.1 kg/cm2 suction pressure ± 0.01 kg/cm2 power±1%
refrigerant circulation±1%
3.1.4 Facilities to be provided on the unit under test For quick and efficient testing, it is essential for facil-ities to be provided on the unit used for the type test, in order to be able to make the measurements.
I. Flow meter connections for measuring refrigerant circulation (See also 3.1.2 point 1). In the liquid pipe, after the condensers or after the liquid tank, if any, or after the heat exchanger two closable side pipes with cocks must be fitted, while it must also be possible to close off the liquid pipe between both side pipes. See Fig. 1.
This system can also be used when a need arises to check the unit's performance on board.
2. Pressure measuring points for: suction pressure of compressor(s), oil pressure of compressor(s), discharge pressure of compressor(s), pressure in condenser(s),
pressure at inlet side of each evaporator or evaporator section,
pressure at outlet side of each evaporator or evaporator section.
The arrangement of these pressure connections is
shownin Fig. 2 On the pipe in which pressure has to be measured, a valve is fitted with a " flare connection via a small pipe at least 50 mm long.
It is advisable to close off the part of the valve fading away from the installation with a cap or soldered off
14 min im um 50 mm 1/4" /4" valvé must be capabÌe of air-tight closure Fig. 2.
pipe. After testing, the, pipes befôre the valves are squeezed together and soldered off, after which the valves are returned to the priñcipal. These connecting points' and the places where temperature measurements have to be made (See 3.1.2 point 1) must be easily
accessible.
3.1.5 Duration
In drawing up a timetable it must be remembered that a well-equipped laboratory will need about 4 to 6 weeks for these tests.
3.2 Operating test
All units undergo this test befOre delivery; the purpose is to ascertain whether the behaviour of the umts does not, differ substantially from that of the prototype. This test can be made either in a workshop or on board ship.
3.2.1 Test procedure
This test does not necessitate connecting the unitj to an insulated space.
It must, however, be possible to connect the unit
pipe in which pressure has to be measured
similarly to practical conditions, and this requires the availability of:
- the correct voltage and power,
- the correct quantity of defrosting water, if appro-priate,
- sufficient power if electrical defrosting is applied, - sufficient oil of the required temperature in case of
hot oil defrosting,
- sufficient compressed air in case of pneumatic control.
3.2.2 Measurements (See also 3.1.2)
The unit is set in operation withoût being connected to a test chamber, and it is not therefore possible to
mea-sure directly the quantity of heat the evaporator
extracts from the air. It may be possible, however, by short-circuiting the outfiowing and inflowilig airfiows to maintain a temperature of, say, about O °C 'around the evaporator.It will now suffice to record the following:
I. refrigerant circúlation.
FOr this, provisiOn must howevef be made for connecting the necessary meter (See 3.1.4 point 1). suction, discharge and oil pressures of the com-pressors.
temperature around the evaporator. the quantity of dirt deposited on the ifiter. the progress of defrosting.
It must also be examined whether all safety devices work properly.
With this information, and With the results obtained in testing the prototype, the refrigerating capacity can be determined, even though with less accuracy than in type tests, and a good idea Of correct operation can be obtained.
PUBLICATIONS OF THE NETHERLANDS SHIP RESEARCH CENTRE TNO
PUBLISHED AFTER 1963 (LIST OF EARLIER PUBLICATIONS AVAILABLE ON REQUEST)
PRICE PER COPY DFL.
10,-M = engineering department S = shipbuilding department C = corrosion and antifouling department
Reports
57 M Determination of the dynamic properties and propeller excited
vibrations of a special ship stem arrangement. R. Wereldsma, 1964.
58 S Numerical calculatiOn of vertical hull vibrations of ships by
discretiuing the vibration system, J. de Wies, 1964.
59 M Controllable pitch propellers, their suitability and economy for large seagoing ships propelled by conventional, directly coupled engines. C. Kapsenberg, 1964.
60 S Natural frequencies of free vertical ship vibratiOns. C. B. Vreug-dthhil, 1964.
61 S The distribution of the hydrodynamic forces on a heaving and
pitching shipmodel in still water. J. Gethtsma and W. Beukel-man, 1964.
62 C The mode of action of anti-fouling aiIItS : Interaction between anti-fouling paints and sea water. A. M. van Londen, 1964.
63 M Corrosion in exhaust driven turbochargers on marine diesel
engines using heavy fuels. R. W. Stuart Michell and V. A. Ogale,
1965.
64 C Barnacle fouling on aged anti-fouling paints ; a survey of perti-nent literature and some recent observations. P. de Wolf, 1964. 65 S The lateral damping and added mass of a horizontally oscillating
shiprnodel. O. van Lecuwen, I 964.
66 S Investigations into the strength of ships' derricks. Part. I. F. X.
P.Soejädi, 1965.
67 S Heat-transfer in cargötanks of a 50,000 DWT tanker. D. J. van
der Heeden and L. L. Mulder, 1965.
68 M Guide to the application of Method for calculation of cylinder liner temperatures in diesel engines. H. W. van Tijen, 1965.
69 M Stress measurements on a propeller model for a 42,000 DWT
tanker. R. Weretdsma, 1965.
70 M Experiments on vibrating propeller models. R. Wereldsma, 1965.
71 S Research on bulbous bow ships. Part II. A. Still water
perfor-mance of a 24,000 DWT bulkcarrier with a large bulbous bow. W. P. A. van Lammeren and J. J. Muntjewerf, 1965.
72 S Research on bulbous bow ships. Part. JJ: B. Behaviour of a
24,000 DWT bülkcarrier with a large bulbous bow in a seaway. W. P. A. van Lammeren and F. V. A. Pangalila, 1965. 73 S Stress and strain distribution in a vertically corrugated bulkhead.
H. E. Jaeger and P. A. van Katwijk, 1965.
74 S Research on bulbous bow ships. Part. I. A. Still water investiga tions into bulbous bow forms for a fast cargo liner. W. P. A. van Lammeren and R. Wahab, 1965.
75 S Hull vibrations of the cargo-passenger motor ship "Oranje
Nassau", W. van Horssen, 1965.
76 S 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 sea-way. R. Wahab, 1965.
77 M Comparative shipboard measurements of surface temperatures
and surface corrosion in air cooled and water cooled turbine outlet casings of exhaust driven marine diesel engine
turbo-chargers. R. W. Stuart Mitchell and V. A. Ogale, 1965. 78 M Stern tube vibration measurements of a cargo ship with special
afterbody. R. Wereldsma, 1965.
79 C The pre-treatment of ship plates: A comparative investigation
on some pre-treatment methods in use in the shipbuilding iñdus-try. A. M. van Londen, 1965.
80 C 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. A. M. van Londen and W. Mulder, 1965.
81 S The performance of U-tanks as a passive anti-rolling device.
C. Stigter, 1966.
82 S Low-cycle fatigue of steel structures. J. J. W. Nibbering and
J. van Lint, 1966.
83 S Roll damping by free surface tanks. J. J. van den Bosch and J. H. Vugts, 1966.
84 S Behaviour of a ship in a seaway, J. Gerritsma, 1966.
85 S Brittle fracture of full scale structures damaged by fatigue. J. J. W. Nibbering, J. van Lint and R. T. van Leeuwen, 1966. 86 M Theoretical evaluation of heat transfer in dry cargo ship's tanks
using thermal oil as a heat transfer medium. D. J. van der
Heeden, 1966.
87 S Model experiments on sound transmission from engineroom to açcommodation inrnotorshipsJ. H. Janssen, 1966.
88 S Pitch and heave with fixed and controlled bow fina. J. H. Vugts,
1966.
89 5 Estimation of the natural frequencies of a ship's double bottom by means of a sandwich theory. S. Hylarides, 1967.
90 S Computation of pitch and heave motions for arbitrary ship forms. W. E. Smith, 1967.
91 M Corrosion in exhaust driyen turbochargers on marine diesel en-gines using heavy fuels. R. W. Stuart Mitchell, A. J. M. S. van
Montfoort and V. A. Ogale, 1967.
92 M Residual fuel treatment on board ship. Part H. Comparative
cylinder wear measurements on a laboratory diesel engine using filtered or centrifuged residual fUel. A. de Mooy, M. Verwoest and G. G. van der Meulen, 1967.
93 C Cost relations of the treatments of ship hulls and the fuel
con-sumption of ships. H. J. Lageveen-van Kuijk, 1967.
94 C Optimum conditions for blast cleaning ofsteel plate. J. Remmelts,
1967.
95 M Residùal fuel treatment on board ship. Part. I. The effect of cen-trifuging, filtering and homogenizing on the unsolubles in
residual fuel. M. Verwoest and F. J. Colon, 1967.
96 S Analysis of the modified strip theory for the calculation of ship motions and wave bending moments. J. Gerritsma and W. Beu-kelman, 1967.
97 S On the efficacy of two different roll-damping tanks. J. Bootsrna and J. J. van den Bosch, 1967.
98 S Equatiön of motion coefficients for a pitching and heaving des-troyer model. W. E. Smith, I 967.
99 S The rnanoeuvrability of ships on a straight course. J. P. Hooft,
1967.
100 5 Amidships forces and moments on a CB = 0.80 "Series 60"
model in waves from various directions. R. Wahab, 1967. 101 C Optimum conditions for blast cleaning ofsteel plate. Conclusion.
;J. Remmelts, 1967.
102 M The axiäl stiffness of marine diesel engine crankshafts. Part I. Comparison between the results ôf full scale measurements and
those of calculations according to published formu1ae. N. J.
Visser, 1967.
103 M The axial stiffness of marine diesel engine crankshafts. Part II. Theory and results of scale model measurements and comparison with published formulae. C. A. M. van derLinden, 1967 104 M Marine diesel engine exhaust noise. Part I. A mathematical model.
J. H. Janssen, 1967.
105 M Marine diesel engine exhaust noise. Part II. Scale models of
exhaust systems. J. Buiten and J. H. Janssen, 1968.
106 M Marine diesel engine exhaust noise. Part. ifi. Exhaust sound
criteria for bridge wings. J. H. Janssen en J.. Buiten. 1967.
107 S Ship vibration analysis by finite element technique. Part. I. General review and application to simple structures, statically loaded. S. Hylarides, 1967.
108 M Marine refrigeratiön engineering. Part I. Testing of a
decentrai-ised refrigerating installation. J. A. Knobbout and R. W. J.
Kouffeld, 1967.
109 S A comparative study on four different passive roll damping
tanks. Part I. J H. Vugts, 1968.
110 S Strain, stress and flexure of two corrugated and one plane
bulk-head subjected to a lateral, distributed load. H. E. Jaeger and
P. A. van Katwijk, 1968.
111 M Experimental evaluation of heat transfer in a dry,cargo ships'
tank, using thermal oil as a heat transfer medium. D. J. van der Heeden, 1968.
112 S The hydrodynamic coefficients for swaying, heaving and rolling cyhnders in a free surface. J. H. Vugts, 1968.
113 M Marine refrigeration engineering Part II. Some results of testing a decentralised marine refrigerating unit with R 502. J. A. Knob-bout and C. B. Colenbrander, 1968.
115 S Cylinder motions in beam waves. J. H. Vugts, 1968.
116 M Torsional-axial vibrations of a ship's propulsion system. Part I. Comparative investigation of calculated and measured
torsional-axial vibrations in the shafting of a dry cargo motorship.
118 M Stern gear arrangement and electric power generation in ships propelled by controllable pitch propellers. C. Kapsenberg, 1968. 119 M Marine diesel engine exhaust ñöise. Part IV. Transfer damping
data of 40 modelvariants of a compOund resonatorsileÌcer. J. Biten, M. J. A. M. de Regt and W. P. H. Hanen, 1968.
121 S Proposal for thé testiñg of 'e1d metni froth the viewpoint of
brittle fracture initiation. W; P. van den Blink and J. J W.
Nibbering, 1968.
122 M The corrosion behaviour of cunifer IO alloys in seawaterpiping-Systems on board ship. Part I. W. J. J. Gotzee and F. J. Kievits,
1968.
123 M Marine refrigeration engineering. Part III. Proposal foî a
specifi-cation of a marine refrigerating unit and test proedures. J. A.
Knobbout and R. W. J. Köuffeld, 1968.
Communications
li C Investigations into the use of someshipbottom paints, based on
scarcely saponifiable vehicles (Dutch). A. M. van Londen and P. de Wolf, 1964.
12 C The pre-treatrnent of ship plates: The treatment of welded joints
prioÈ to painting (Dutch). A. M. van Londen and W. Mulder,
1965.
-13 C Corrosion, ship bottom paints (Dutch). H. C. Ekama, 1966.
14 S Human reaction to shipboard vibration, a study of existing
literature (Dutch). W. ten Cate, 1966.
15 M Refrigerated containerized transport (Dutch). J. A. Knobbout,
1967.
16 S Measures to prevent souñd and vibration annoyance aboard a
seagOing passenger and carferry, fitted out with dieselengines (Dutch). J. Buiten, J. H. Jansseñ, H. F. Steenhoek and L. A. S. Hageman, 1968.
17 S Guide for the specification, testing and inspection of ¿lass
reinforced polyester structures in shipbuilding (Dutch). G.
