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Journal of Loss Prevention in the Process Industries 26 (2013) 830e838

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Journal of Loss Prevention in the Process Industries

journal homepage: www.elsevier .com/locate/ j lp

An experimental study on the temperature dependence of CO2explosive evaporation

M.M. van der Voort a,*, R.M.M. van Wees a, J.M. Hamb, M.P.N. Spruijt b, A.C. van den Berg a,P.C.J. de Bruijn a, P.G.A. van Ierschot a

a TNO, Dep. Explosions, Ballistics and Protection, PO Box 45, 2280 AA, Rijswijk, The Netherlandsb TNO, Dep. Urban Environment & Safety, PO Box 80015, 3508 TA Utrecht, The Netherlands

a r t i c l e i n f o

Article history:Received 4 January 2013Received in revised form19 February 2013Accepted 24 February 2013

Keywords:Explosive evaporationBlastBLEVEHomogeneous nucleation temperatureCarbon dioxideCO2

* Corresponding author. Tel.: þ31 (0) 888661288.E-mail address: martijn.vandervoort@tno.nl (M.M

0950-4230/$ e see front matter � 2013 Elsevier Ltd.http://dx.doi.org/10.1016/j.jlp.2013.02.016

a b s t r a c t

The need for transportation and storage of CO2 in bulk quantities is likely to increase in the near future.The handling of CO2 on such scale gives rise to a number of technological challenges and safety aspects.The accidental rupture of a vessel containing liquefied CO2 may lead to a Boiling Liquid ExpandingVapour Explosion (BLEVE). Whether explosive evaporation of liquefied CO2 is also possible at storagetemperatures below the homogeneous nucleation temperature 271 K (�2 �C) is unclear.

This article describes the results of 12 experiments with 40 L CO2 cylinders at various temperatures toinvestigate the temperature dependence of explosive evaporation. The cylinders were opened with linearshaped charges to simulate a near instantaneous rupture, and blast was measured at various locations.The observed blast could be clearly attributed to explosive evaporation. The results show that below thehomogeneous nucleation temperature, BLEVE blast does not disappear abruptly, but instead follows agradual decay. Predictions with a numerical BLEVE blast model overestimate the observed blast peakoverpressure and impulse, but qualitatively show a similar behaviour. The energy lost by the accelerationof the cylinder parts is a possible reason for overestimations of the model.

The consequence of the test results is that for accident scenarios with CO2 at low temperatures a BLEVEshould not be neglected in hazard assessments. Future large scale bulk storage will take place at a 105

times larger volume than the cylinders applied in the current small scale experiments. We expect thatthe blast-reducing effects of a tank shell will disappear at such scale.

The research leading to these results has received funding from the European Community’s SeventhFramework Programme (FP7/2007e2013) under grant agreement n� 241381.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

The need for transportation and storage of CO2 in bulk quantitiesis likely to increase in the near future. The handling of CO2 on suchscale gives rise to a number of technological challenges and safetyaspects. Transport through pipelines will take places under super-critical conditions with pressures ranging from 100 to 150 bar. Theforeseen ship transport of liquefied CO2 will take place in sphericaltanks with a volume in the order of 10,000 m3, at a temperature of223 K (�50 �C) and a pressure of 7 bar. Storage at higher temper-atures and pressures may be relevant for smaller tanks. The regimeof interest is shown in Fig. 1.

. van der Voort).

All rights reserved.

The accidental rupture of a vessel containing liquefied CO2 maylead to a Boiling Liquid Expanding Vapour Explosion (BLEVE). Adetailed account of such an event is described by Clayton andGriffin (October 1994). This scenario is considered in many indus-trial hazard evaluations and risk assessments. Whether explosiveevaporation of CO2 is also possible below the homogeneousnucleation temperature is unclear. The current article deals withthe experimental investigation of the temperature dependence ofthis phenomenon. The research leading to these results hasreceived funding from the European Community’s SeventhFramework Programme (FP7/2007e2013) under grant agreementn� 241381. In the remainder of this introduction we present anoverview of the state of the art of BLEVE research.

Under normal storage conditions, liquid and vapour in a vesselare in a state close to thermodynamic equilibrium. When a vesselruptures, the pressure suddenly drops to ambient pressure. Thevapour will expand, cool and partially condense and freeze. CO2 is

Fig. 1. Vapour pressure and liquid density for CO2 versus temperature, based on datafrom NIST (NIST chemistry webbook, 2012). A number of important temperatures andtemperature ranges are also indicated. THN is the homogeneous nucleation tempera-ture, TCrit is the critical temperature, TS is the sublimation temperature.

Fig. 2. Blast charts for the explosive evaporation of liquid CO2 calculated analogous toVan den Berg (2008). Non-dimensionalised peak overpressure and scaled impulseversus scaled distance. The distance and impulse have been scaled with the liquid massM to the power 1/3. Graphs are given for four relevant temperatures within the rangeof future storage conditions. The location of the pressure transducers B1 through B4applied in the experiments is also shown.

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special compared to other pressure-liquefied gases, it becomes asolid at ambient pressure and low temperature. The liquid will startto boil when it is depressurised. The evaporation process requiresheat, which is extracted from the liquid. As a consequence, thetemperature and the vapour pressure of the remaining liquid fall.The evaporation changes to sublimation and continues until thetemperature of the solid CO2 has reached the equilibrium tem-perature at ambient pressure. The quick phase change from liquidto vapour causes a large volume increase. Ambient air will bepushed aside, with a blast wave as possible consequence when theevaporation is quick enough.

Van den Berg, Van der Voort, Weerheijm, and Versloot (2004),Van den Berg, Van der Voort, Weerheijm, and Versloot (2006), andVan den Berg (2008) developed amodel for the prediction of BLEVEblast, which computes the gas dynamics of an explosive evapora-tion process numerically. The model starts from the assumptionthat the expansion is vapour pressure-driven and there are nothermodynamic limitations to the evaporation rate. This meansthat thermodynamic equilibrium at the interface between liquidand vapour is assumed. As a result there are negligible limitationson the transfer of heat andmass to the surface. The evaporation rateand the consequent expansion process are then fully determined bythe inertia of the developing vapour and the surrounding atmo-sphere being pushed away. The heat needed for the evaporation isextracted uniformly from the liquid. The flow model is a homoge-neous two-phase flow model in which a single set of Euler equa-tions is solved. The fact that the evaporation, in general, isincomplete is taken into account in the form of an effective densityof the liquid/vapour mixture represented as a single phase. Thisinertia-limited approach is obviously safe and conservative in itsstarting points.

The BLEVE blast model shows a reasonable agreement withexperimental results described by Van der Voort, Van den Berg,Roekaerts, Xie, and de Bruijn (2012). During these experiments40 L CO2 cylinders at standard room temperaturewere openedwithlinear shaped charges, to simulate a near instantaneous rupture.The blast overpressure was measured at various distances. Goodqualitative agreement between model and experiment was found,while quantitatively the results of the model give an over-estimation. The rupture was near-instantaneous, but the accelera-tion of the cylinder fragments takes time and energy. This is nottaken into account in the model, and is therefore a likely reason forthe overestimation. The model reproduces the characteristic BLEVEblast which exhibits a deep and long negative phase which isrelated to the supersonic expansion flowwithin the expanding mixof vapour and liquid.

Blast charts generated with a 1 D spherically symmetric versionof the model (Van den Berg, 2008) are shown in Fig. 2 for initialtemperatureswithin the range of CO2 storage conditions (Fig.1). Theblast charts give the non-dimensionalised peak overpressure andscaled impulse of the BLEVE blast wave versus the scaled distance.

The critical temperature for CO2 is 304 K (31 �C). Above thistemperature there is no distinction between the liquid and vapourphase. Although a vessel rupture under these conditions may alsolead to a blast wave, this is by definition not a BLEVE.

According to some authors also a minimum temperature for aBLEVE exists. At small superheating the evaporation will only startat evaporation nuclei at walls and at impurities or ions in the liquid.The evaporation rate is then far too low for the development of anysignificant blast effect. Reid (1976, 1979) observed however, thatexplosive evaporation occurs when the liquid temperature is abovethe superheat limit temperature (also called homogeneous nucle-ation temperature).

Only in this case evaporation occurs simultaneously throughoutthe liquid. In the entire liquid volume, vapour develops andstrongly expands, entraining the remaining liquid. During thisprocess, the liquid atomizes into small droplets, which allows anefficient further phase change. According to Reid (1976, 1979), only

Fig. 3. Schematic overview of the experimental setup (top view).

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such an evaporation process can be fast enough to produce signif-icant blast. As a rule of thumb, Reid (1976, 1979) found the homo-geneous nucleation temperature to be approximately equal to 89%of the critical temperature. For CO2 this temperature equalsapproximately 271 K (�2 �C). Note that the BLEVE blast model(Fig. 2) does not include nor predict the homogeneous nucleationtemperature. As a result the model predicts blast even below thehomogeneous nucleation temperature. If relevant the homoge-neous nucleation temperature has to be set as an artificialboundary.

A theoretical prediction of the conditions for which a BLEVEmayoccur was recently described by Clifford (2008). They calculate atwhich point the so-called ‘spinodal curve’ is reached for a specificequation of state. A BLEVE is only possiblewhen the ‘spinodal point’is reached, which occurs when:

�vPvV

�T¼ 0

From this property Clifford (2008) calculate the regime ofpressures and temperatures for which a BLEVE may occur.

Although the superheat limit theory of explosive evaporation iswidely accepted in the literature on explosions (Abbasi & Abbasi,2007a, 2007b), it has not been directly proven to be true, due tothe impossibility to do detailed measurements in the superheated

Fig. 4. Left: CO2 cylinder mounted with 1 m length Semtex RAZOR 10 linear shape

liquid during a realistic BLEVE experiment. In fact Birk, Davison, andCunningham (2007) have expressed doubt whether evaporation ofsuperheated liquids can occur sufficiently fast to produce signifi-cant blast at all. On the other hand CO2 is special; the liquid tends tocrystalize at ambient pressure. If crystals are formed throughoutthe liquid, these might allow efficient evaporation. Also the evap-oration rate that can generate ’significant’ blast has not beenestablished.

The current article describes an extension of the experiments byVan der Voort et al. (2012) focussed on the temperature depen-dence of the explosive evaporation of CO2. These experiments wereconducted to test the superheat limit theory of explosive evapo-ration, and to answer the question whether explosive evaporationis possible below the homogeneous nucleation temperature.

In Section 2 the experimental setup is described. The experi-mental results are presented in Section 3, and conclusions aredrawn in Section 4.

2. Description of the experiments

A total of 12 experiments have been conducted at TNO’s Labo-ratory for Ballistic Research (TNO Explosions, Ballistics and Pro-tection) in a test bunker with an internal volume of 6 � 12 � 4 m3.In Fig. 3 a top view of the experimental setup is shown. A 40 L CO2

d charges on two opposite sides. Right: one of two remaining cylinder parts.

Table 1Initial conditions of the CO2 test series.

Test Vapourpressure(bar)

Temperature(�C)

CO2

mass(kg)

Fillfraction(�)

Blastenergyliquid (MJ)

Blastenergyvapour (MJ)

1 N/A N/A 0 0 0 02 48.0 13.5 29.0 0.84 2.151 0.1143 56.1 19.9 29.1 0.92 2.371 0.0754 28.8 �5.8 28.5 0.72 1.688 0.0985 39.0 5.3 27.4 0.73 1.820 0.1416 19.8 �18.2 29.0 0.69 1.507 0.0657 23.0 �13.4 28.7 0.67 1.568 0.0788 58.0 21.3 29.4 0.96 2.466 0.0439 51.0 15.9 28.9 0.86 2.214 0.11010 14.5 �25.4 28.5 0.66 1.372 0.05311 33.8 0.4 28.7 0.75 1.821 0.11012 26.5 �7.7 28.2 0.70 1.635 0.096

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cylinder is placed centrally in the test bunker. 1 m length SemtexRAZOR 10 linear shaped charges are placed on two opposite sides ofthe cylinder to realize a near instantaneous rupture (Fig. 4, left).These shaped charges have an explosive content of 140 � 10 g/mSEMTEX (RDX/PETN), and are able to cut through 10 mm steel. Thisis enough to cut a CO2 filled cylinder (which has a wall thickness of6 mm) in two parts (Fig. 4, right). The expansion of the CO2 will notbe perfectly cylindrical, because of the obstruction by the cylinderparts.

Blast overpressures were measured along the central axis of thetest bunker. The plane defined by the shaped charges was given asmall deflection with respect to the central measurement axis, toavoid direct impacts by shaped charge fragments at the pressuretransducers. The fragments from the CO2 cylinder were alsodirected away from the transducers. Nevertheless all measurementequipment and cables in the test bunker were appropriatelyshielded.

To monitor the blast waves, four pressure transducers (Endevco8530B) were installed at locations along the central axis of the testbunker. The pressure transducers were mounted in skimmer platesat locations B1 (1 m) and B2 (2 m). These distances are measuredrelative to the CO2 cylinder wall. With a cylinder diameter equal to250mm, the distances to the cylinder axis are 125mm larger. At theother side the transducers were mounted vertically in a large blastpencil. This pointed tube is used frequently in blast experimentsand is intended to protect the transducers from fragments, whileminimising the disturbance to the blast wave. The tube may how-ever give some disturbances to the blast wave propagation. In test 1and 2 the blast tube was positioned such that B3 and B4 had adistance of respectively 2 and 3 m to the cylinder wall. In later tests(3e12) the blast pencil was moved closer to the cylinder, as it wasobserved that most interesting blast signals were recorded at 1 and2 m distance. The transducers were placed at a height of 1.12 mmeasured from the floor. This can be compared to the cylinderheight of 1.19 m. Black grease was applied to the transducersbefore each test to limit heat transfer and to reduce the influenceof the flash during the shaped charge explosion.

The pressure signals have been obtained using the SCADAS IIIsystem with a sampling rate of 202 kHz. Before the experiments,the total measurement chain of transducers, cables, amplifier andADC was calibrated. To do this the transducers were connected to astatic pressure calibrator and loaded with different pressure values.With this calibrationmethod the pressure can bemeasured with anaccuracy of about 1%. Because the opening of the cylinders is notperfectly repeatable, stochastic variations were a dominant factorin the overall measurement error. Themagnitude of this error could

Fig. 5. Estimation of the cooling and heating of CO2 cylinders.

not be properly quantified due to the limited number of performedexperiments. Other sources of error are blast wave reflections fromthe walls and roof of the test bunker disturbing the events underinterest. This phenomenon starts to play a significant role afterabout 20ms. Themeasured pressure signals have been processed inthe signal analysis program FAMOS. To focus on BLEVE Blast phe-nomena, a low pass filter at 3 kHz was applied to the presentedsignals.

The first test was a reference test with an empty cylinder, tocapture the blast from the shaped charges alone. Test 2e12 are testswith CO2 filled cylinders at temperatures ranging from 248 K(�25 �C) to 294 K (21 �C). This temperature range is also indicatedin Fig.1. The homogeneous nucleation temperature at 271 K (�2 �C)is situated half waywithin this range. The cylinders were brought atdesired temperatures by exposing them to the outside temperature(about 5 �C) or by placing them in a freezer (minimum �25 �C),before bringing them into the test bunker (15 �C) and attaching theshaped charges. An estimate for the required time of cooling wasobtained by following the ‘cooling curves’ in Fig. 5. When the cyl-inders were employed in a test, the vapour pressure was measuredby connecting a Class 1 analogue manometer to the cylinder. Theambient pressure was 1.0 bar during the tests. The manometer hada full scale of 60 bar, and a specified measurement error of 1% fullscale (0.6 bar). The vapour pressure is directly related to the CO2

temperature, as was also shown in Fig. 1. A measurement was takenin the latest possible moment before a test. The time interval be-tween this measurement and the test was between 3 and 10 min.The time interval was registered and a correction was determinedfollowing the ‘heating curves’ in Fig. 5. Both the cooling and heatingcurves are based on time-dependent heat transfer theory for nat-ural convection. It is assumed that the heat capacity of a CO2 cyl-inder is fully determined by CO2, while the thermal conductivity is

Fig. 6. Blast energy versus temperature for the liquid and vapour phase for the CO2 testseries.

Fig. 7. Pressure time signals recorded at B1 (1 m from the cylinder) for the reference test and for a typical test with CO2 (at 19.9 �C).

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limited by that of CO2. It has been verified that the heat transfer forthis situation is in the laminar regime, from which a Nusseltnumber follows in the order of 37. To verify the quality of thisprediction the heating of a cylinder from�5 �C has been monitoredin the test bunker (atþ15 �C). The temperature increase follows theheating curve from �5 �C quite well.

Note that the CO2 was not in perfect equilibrium in the test, dueto the temperature difference between the cylinder and the testbunker. Low temperature cylinders will have been boiling on thecylinder wall/liquid interface and the vapour was at slightly highertemperature than the liquid.

The initial conditions of the 12 tests are given in Table 1. Eachcylinder had a serial number, and a tar mass registered by themanufacturer. Before the test series each cylinder was weighed,from which the net CO2 mass could be determined. Observedfluctuations are caused by inaccurate filling. Based on the liquiddensity given in Fig. 1 the fill fraction (volume fraction liquid CO2)could be determined. Within the tested temperature range it varied

Fig. 8. Pressure time signals recorded at B1 (1 m from the cylinder) f

from about 66% to 92%. This means that especially for the lowertemperatures a significant vapour space is present. With a methoddescribed in PGS 2 (Yellow Book) (2005), the available expansionenergy for both the liquid and vapour phase has been determined,assuming an isentropic expansion from the initial state to ambientpressure. The results are also displayed in Fig. 6. The results indicatethat the blast energy of the vapour phase is always just a fewpercent of that of the liquid phase. The fluctuations are a directconsequence of the fluctuations in CO2 mass.

3. Experimental results

During the reference test the empty cylinder did not failcompletely. Two 1 m length cuts could be observed at the originalshaped charge locations. During all tests with CO2 filled cylindersthe cylinders failed completely in two parts as was already shownin Fig. 4 (right). Apparently an internal pressure is required to causecrack growth and subsequent complete failure.

or the reference test and tests with CO2 at various temperatures.

Fig. 9. Impulse versus time recorded at B1 (1 m from the cylinder).

M.M. van der Voort et al. / Journal of Loss Prevention in the Process Industries 26 (2013) 830e838 835

In Fig. 7 pressure time signals recorded at B1 (1 m from thecylinder) are shown for the reference test (empty cylinder) and for atest with CO2 at 19.9 �C. The first visible event is the passage of theshaped charge blast wave after 2 ms. This event is very wellreproduced in all tests. The positive phase of the BLEVE blast wavefollows between 3 and 5 ms, and has a peak overpressure of about40 kPa. A relatively deep and long negative phase can be observedfrom 5 to 18 ms, with a magnitude of about �50 kPa. These valuesare comparable to earlier measurements for CO2 at this tempera-ture and distance by Van der Voort et al. (2012). The shaped chargereflection from the roof and walls of the test bunker arrives at B1after 13 ms in the reference test. In the tests with CO2 filled cylin-ders this reflection arrives slightly later, presumably because thereflection propagates back through an expanding medium.

In Fig. 8 the pressure time signals recorded at B1 are showntogether for all tests. The reference test signal is shownagain inblack

Fig. 10. Pressure time signals recorded

while the signals for the various temperatures have been givenintuitive colours ranging from purple (lowest temperature) to blue,green, yellow, and red (highest temperature). The observationsmade for the test at 19.9 �C in Fig. 7 are generally also valid for theother tests. The peak overpressure of the BLEVE blast positive phaseand the depth of the negative phase increasewith temperature. Thetime of the deepest negative phase shifts from5 to 7ms to 10e13mswhen the temperature increases from 5 to 13 �C.

The impulse has been calculated by integrating the pressuretime signals from 0 s up to the time displayed on the horizontalaxis. The result is displayed in Fig. 9, and shows even more clearlythe consistent increase of explosion strengthwith temperature. Themaximum impulse is equal to 100 Pa s (compared to 60 Pa s for thereference test).

The signals recorded at B2 (at 2 m from the cylinder) are shownin Fig. 10. The same consistent trend with temperature can be

at B2 (2 m from the CO2 cylinder).

Fig. 11. Impulse versus time recorded at B2 (2 m from the cylinder).

M.M. van der Voort et al. / Journal of Loss Prevention in the Process Industries 26 (2013) 830e838836

recognized as at B1. Compared to B1 the shaped charge and BLEVEblast pass slightly later. The relatively short duration shaped chargeblast decays more rapidly than the BLEVE blast. Therefore, theBLEVE blast is more dominant as compared to Fig. 7. The BLEVEblast overpressure stays limited to 25 kPa, while the deepestnegative phase is �35 kPa.

The impulse calculated at B2 is shown in Fig. 11. The maximumimpulse is equal to 120 Pa s (compared to 50 Pa s for the referencetest). This means that compared to B1 the shaped charge impulsedecreases, but the BLEVE blast impulse increases.

The pressure time signals recorded at B3 and B4 show similartrends. They have been left out to limit the size of the currentarticle.

The observed peak overpressures have been plotted versustemperature in Fig. 12. The experimental data exhibits a slow in-crease with temperature, and no extraordinary behaviour isobserved around the homogeneous nucleation temperature.

Fig. 12. Peak overpressure versus temperature at 1 and 2 m from the cylinder. Note that in twith the BLEVE blast model (Van den Berg, 2008) are also shown.

Predictions with the 1 D spherically symmetric BLEVE blast model(Van den Berg, 2008) show a significant overestimation at 1 mdistance. At 2 m distance the overestimation is only slight. Themodel shows a stronger increase of the peak overpressure versustemperature than the experiments. The energy lost by the accel-eration of the cylinder parts was already mentioned in Section 1 asa possible reason for overestimations.

The impulse of just the BLEVE blast has been estimated as thedifference between the impulse observed for a test with a CO2 filledcylinder, and the impulse observed in the reference test. The resultis shown in Fig. 13.

As for the overpressure the impulse exhibits a slow increasewith temperature, and no extraordinary behaviour is observedaround the homogeneous nucleation temperature. A strikingfeature is that the impulse consistently shows an increase withdistance in the range from 1 to 2 m. This can be explained if werevisit the blast impulse chart in Fig. 2. In the figure the location of

est 2 the location of transducer B3 and B4 differed from tests 3 through 12. Predictions

Fig. 13. Impulse observed in tests with CO2 filled cylinders minus the impulse observed in the reference test, versus temperature at 1 and 2 m from the cylinder. Note that in test 2the location of transducer B3 and B4 differed from tests 3 through 12. Predictions with the BLEVE blast model (Van den Berg, 2008) are also shown.

M.M. van der Voort et al. / Journal of Loss Prevention in the Process Industries 26 (2013) 830e838 837

the pressure transducers at 1 m (B1 and B3) and at 2 m (B2 and B4)are located close to the local impulse maxima. In this regime a smallchange in blast energy may shift the pressure transducers into thepart of the blast chart where impulse increases with scaled dis-tance. Furthermore it should be realized that the blast charts havebeen generated with a spherically symmetric 1D version of theBLEVE blast code, while the source in the tests is a cylinder. Thismay have a similar effect.

4. Conclusions

The need for transportation and storage of CO2 in bulk quantitiesis likely to increase in the near future. The handling of CO2 on suchscale gives rise to a number of technological challenges and safetyaspects. The accidental rupture of a vessel containing liquefied CO2may lead to a Boiling Liquid Expanding Vapour Explosion (BLEVE).Whether explosive evaporation of liquefied CO2 is also possible atstorage temperatures below the homogeneous nucleation tem-perature 271 K (�2 �C) is unclear.

This article describes the results of 12 experiments with 40 LCO2 cylinders at various temperatures to investigate the tem-perature dependence of explosive evaporation. The cylinderswere opened with linear shaped charges to simulate a nearinstantaneous rupture, and blast was measured at various loca-tions. The observed blast could be clearly attributed to explosiveevaporation. The results show that below the homogeneousnucleation temperature, BLEVE blast does not disappearabruptly, but instead follows a gradual decay. Predictions with anumerical BLEVE blast model overestimate the observed blastpeak overpressure and impulse, but qualitatively show a similarbehaviour. The energy lost by the acceleration of the cylinderparts has been mentioned as a possible reason for over-estimations of the model.

For future experimentation it is recommended to use an openair test site. This avoids blast reflections, and also enables thepossibility to measure the velocity of the cylinder parts in order toestimate the lost energy. Furthermore the test vessel design andshaped charges could be better matched. For the vapour pressuresapplied in the described experiments the vessel design could be

lighter. This holds the advantage that shaped charges with a lowerexplosive content are sufficient to open the vessel, causing lessdisturbances from shaped charges to the pressureetime signals.Additionally a lighter test vessel will cause a smaller energy loss byacceleration of vessel parts.

The consequence of the test results is that for accident scenarioswith CO2 at low temperatures a BLEVE should not be neglected inhazard assessments. Future large scale bulk storage will take placeat a 105 times larger volume than the cylinders applied in thecurrent small scale experiments. We expect that the blast-reducingeffects of a tank shell will disappear at such scale. The physics of aBLEVE at this scale introduces additional questions like whetherexplosive evaporation can take place simultaneously throughoutthe entire liquid volume.

The experimental results also lead to the question how otherliquefied gases such as LNG will behave below the homogeneousnucleation temperature. With respect to CO2 further questions arehow it behaves in case a vessel ruptures above the critical tem-perature, and whether a Rapid Phase Transition (RPT) can takeplace during an spill on water.

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