CO2 evaporative cooling rig user`s manual
Contents
1. ratio of the CO gt when all the liquid CO has evoparted the temperature will increase This increase in temperature has no influence on the stability of the system as long as the liquid CO from the cylinder is pre cooled T1 before it experiences a pressure drop due to the needle valve flow regulator CO2 cooling blowsystem 40 T T T T T T H i i i f T 20 T Celsius Oo 20 H na peer E aerate Bcc caudiStccasa ee eee j 30 40 fi i i i i i i li 14 24 14 38 14 52 15 07 15 21 15 36 15 50 16 04 16 19 t HH MM Figure 13 Temperature time diagram of the power tests to determine the minimal mass flow 18 CO2 cooling blow system Figure 14 A view of the power that is added over time during the power tests CO2 cooling blow system t HH MM Figure 15 Pressure time diagram of the power tests 192. 02 Indication 3 0 1 0 0 1 15 06 Pressure adjustment to 12 bar 15 12 Add power I 12 9 95 4 Watt 1 0 0 2 15 16 Reduce mass flow indication 2 23 1 00 1 15 18 Indication 2 21 1 0 0 05 15 20 Indication 2 19 0 9 0 05 15 22 Indication 2 17 0 9 0 05 15 24 Indication 2 15 0 8 0 05 15 26 Indication 2 13 0 8 0 05 15 28 Indication 2 11 0 7 0 05 15 30 Indication 2 09 0 7 0 05 15 32 Indication 2 07 0 7 0 05 15 34 Indication 2 05 0 6 0 05 15 35 Power off 15 36 Adjust mass flow to indication 3 10 1 4 0 05 15 36 Indication 3 20 1 5 0 05 15 39 Adjust pressure to 12 bar 15 43 Add power I 18 3 200Watt 1 4 0 05 15 49 Indication 3 18 1 4 0 05 15 51 Indication 3 16 1 40 1 15 53 Indication 3 14 1 3 0 1 15 55 Indication 3 12 17 15 55 _ Power off power supply electricity wire too hot 15 57 CO cooling blow system off Figure 13 and Figure 14 give a view of the test results Temperature T5 is always above 20 C and depends on the amount of COQ that is evaporated in the experiment and heat exchanger 1 When the liquid vapour ratio is high this temperature will increase Temperatures T1 T2 and T3 are constant at a cooling temperature of 30 C The temperature peaks are a consequence of the pressure adjustments that are done see Figure 14 Temperature T4 has an instable course over time This is a consequence of the changing liquid vapour
3. flexible tubes e Balance and protector e Ramp e Botlle holder e CO cylinder e Front panel e 5 Thermocouples e Rheonik mass flow meter RHMO15 amp RHEO7 e 2 Pressure gauges e 2 Swagelok relief valve type SS 6R3A MM e Swagelok metering valve type SS 42GS6MM e Swagelok Filter type SS 6TF MM 05 e Swagelok tube fittings 6 mm Figure 10 Product assembly e Merinox stainless tube 3x0 5 mm e Merinox stainless tube 6x1 0 mm e Swagelok convoluted PTFE hose e CO cylinder connection RU1 e Nylon ring The Tamson hot bath circulator is the heat supply for the post heat exchanger heat exchanger 2 It is possible to place a mass flow meter in the system to monitor the mass flow of the CO through the system Adding a mass flow meter to the system must be done by a technician employed at Nikhef The CO cooling blow system exists out the blow system cycle build out of Swagelok parts as shown in Figure 11 With the two pressure gauges the cylinder pressure and system pressure can be monitored Five thermocouples give the system temperature at several points indicated in Figure 11 Figure 11 Schematic view of the CO cooling blow system 13 4 Failure and repair Interference of the Tamson hot bath circulator e Turn the power of the Tamson hot bath circulator off close the CO cylinder don t use the system and report the failure by the Mechanische Technologie department of Nikhef The system can t
4. SOTT Pana res ED based on formulation of R Span amp W Phys Chem Ret Duta 25 1509 1596 1996 Figure 12 Theoretical cooling process of the CO2 cooling blow system The total change in enthalpy for the cooling process is equal to Ah hy_4 hy_1 The change in enthalpy as a consequence of cooling the heat load of the experiment is equal to Ah h3_2 Where h Enthalpy at 20 C and 60 bar 254 kJ kg h Enthalpy after pre cooling and 60 bar kJ kg h Enthalpy after pre cooling and pressure drop kJ kg h _Enthalpy after cooling the experiment kJ kg The mass flow which is necessary for cooling the experiment is equal to the power of the experiment divided by the total change in enthalpy ae Pm Ah Where P Power of the experiment 200 J s Ah Total change in enthalpy kJ kg 15 Table 2 and Table 3give the theoretical calculated mass flows for heat loads of 20 50 100 200 Watt for the different cooling temperatures Table 2 Theoretical enthalpy for a cooling cycle with a liquid vapour ratio of 0 5 T C p bar h kJ kg hy kJ kg h kJ kg h kJ kg Ah kJ kg 30 14 3 254 134 133 285 152 Table 3 Theoretical calculated mass flows for a liquid vapour ratio 0 5 and a cooling temperature of 30 C m 20w g s Pm sow g s m1o0ow g s m 2oow g s 0 13 0 33 0 66 1 32 16 Appendix B Results of reducing mass flow tes
5. This manual is for internal use of Nikhef Manual Carbon dioxide cooling blow system Mechanische technologie Sciencepark 105 1098 XG Amsterdam www nikhef nl Introduction The CO cooling blow system may only be used and controlled by technicians employed at Nikhef This document first gives a short introduction of a cooling cycle followed by the cooling cycle of the CO cooling blow system Next the manual describes the usage control and handling of the blow Caution Carefully read the manual of the CO cooling blow system before use Don t use the CO cooling blow system in a poorly ventilated room and without CO alarm system to avoid the danger of suffocation When the electricity supply fails immediately close the CO cylinder The weight of the CO cylinder is above 25 kg move the cylinder with at least two persons During transport of the CO cooling system always remove the CO cylinder from the system Transport of the CO cylinder has to be done with a cylinder trolley In use always fasten the cylinder in the CO cooling blow system with the cylinder holder strap SPPP Contents Di POCMUCHION es Ea scented duswievlvesdiesves tte E capseeva de diatetateeteuieseveseetvelvens 2 E e a EAE O E A anoles A A N 2 COMLEMES E E E E E E E EEE 3 1 Refrigeration Cycle eunonsnenn in A EEA 4 1 1 Blow system CyCle iiras canainean EA a EA EEEE RA glans EEEE 5 1 2 COz cooling blow system Gesien s ssss
6. ains two types of sensors temperature sensors and pressure sensors The two pressure gauges on the front panel of the system function as pressure sensors Gauge 8 indicates the pressure in the CO cylinder and gauge 3 indicates the system pressure The temperature sensors are thermocouple sensors and indicate the temperature of CO at the following points e TI Temperature of the heat exchanger loutlet e T2 Temperature of the experiment inlet e T3 Temperature of the experiment return e T4 Temperature of the heat exchanger 2 inlet e T5 Temperature of the heat exchanger 2 outlet vent 2 2 Connecting the blow system Check if the cylinder is secured with the cylinder holder strap and that the ramp is secured Next make sure that all the Swagelok connections to the CO cooling blow system are connected securely The connections to consider are e Experiment inlet 2 e Experiment return 4 e Relief connection 9 e Cylinder connection 7 Plug the power plugs of the Tamson hot bath circulator and if present the flow meter in sockets 2 3 Disconnecting the blow system Make sure that the CO cylinder is closed properly Measure the temperature of the CO and the system pressure p bar T C The table to the left indicates the system pressure and the temperature of 60 40 CO at which a pressure drop to 1 bar may occur without snow formation 50 30 in the system 40 20 There won t be snow formation when
7. cooling blow system The needle valve causes a pressure drop and thereby the cooling temperature During the passage of the experiment the liquid CO will evaporate as a consequence of the added heat produced by the experiment The post heat exchanger heats the CO up to 20 C and the cooling fluid can be vented safely into the environment The relief valve makes it possible to regulate the pressure and thereby the cooling temperature in the blow system 2 CO2 cooling blow system usage The CO cooling blow system can be used for quick experiment power cooling The system is able to cool down experiments to a temperature range of 30 to 10 C The maximal power that can be cooled with the blow system is equal to 200 Watt Figure 5 gives a view of the CO cooling blow system with indication of the important parts and controls 7 Bottle connection Regulator 2 Experiment Pressure gauge Pressure gauge 10 Bottle 4 Experiment 9 Relief Holder Return connection 5 Pressure Regulator Hot bath circulator 12 Bottle Plateau 13 Bottle Balance Figure 5 Indication of the parts of the CO cooling blow system Don t use the CO cooling blow system in a poorly ventilated room and without CO alarm system to avoid the danger of suffocation In use always fasten the cylinder in the CO cooling blow system with the cylinder holder strap 2 1 Sensors of the CO2 cooling blow system The CO cooling blow system cont
8. ely close the CO cylinder As soon the temperature of the experiment is sensors T2 and T3 is cold turn the flow regulator to the required indication which is given in paragraph 2 6 Adjust the pressure regulator to the required pressure Mind to do this slowly for small pressure changes small turns and wait 30 seconds Watch temperature sensor T4 for this temperature gives an indication for the stability of the cooling temperature When T4 increases much over time it s possible that the flow is too low and the system isn t able to cool the power of the experiment After a while the experiment temperatures T2 and T3 will increase due to the mass flow shortage Keep an eye on temperature sensors and mind that e T4 may not increase much in time e T2 and T3 must be approximately equal to the acquired cooling temperature e T5 may not be lower than 10 C The power of the experiment can be set when the acquired pressure cooling temperature and mass flow is reached 2 6 System settings The settings of the metering valve of the CO cooling blow system are measured for certain mass flows The settings will be set so that the cooling temperature 30 C is reached The mass flow will be set to reach a liquid vapour ratio of 0 5 after passing the experiment The power of the experiment will be varied between 20 and 200 Watt In the following tables the settings for the metering valve for the cooling temperatures and heat loads are gi
9. flow tests cecessecscceseeseeeeceseceeeeaeeaeceeceaeesececeaeesesereeaeeneeess 17 1 Refrigeration cycle The cooling cycle of a refrigerator is a process based on dry compression cooling a cooling process where the cooling medium is heated up to overheated vapour before it is compressed A view of the dry compression cooling process by means of a pressure enthalpy diagram is given in Figure 1 h kJ kg hg h4 Figure 1 Schematic view of the cooling cycle of a refrigerator in a pressure enthalpy diagram Liquid from the condenser 4 1 is expanded between node 1 and 2 The expansion causes a pressure drop from p to p a phase change from liquid to a liquid vapour mixture and a temperature decrease to temperature T the saturation temperature of p Next the cooling medium is evaporated and overheated at constant pressure between node 2 and 3 After evaporation of the cooling medium to vapour the cooling medium is isentropic compressed from pressure p to pz 3 4 During this process work hy h is added to the system in form of compression The compressed vapour at node 4 is cooled to node 5 and condensed to node 1 at a constant pressure During this process the overheated vapour changes back to liquid to restart the described cycle Pre cooling the cooling medium before expanding makes it possible to reach a vapour ratio of 0 after expanding the cooling medium node 2 The dry compression cooling process with pre c
10. inder connection mind that the nylon ring is present 2 5 Getting started When the CO cooling blow system is properly connected as described in paragraph 2 2 it is time to start cooling It is important to follow the instructions for the user safety Temperature Turn on the power of the Tamson hot bath circulator as shown in Figure 8 The temperature of the water in the hot bath can be set with the temperature knob on top of the Tamson 40 C Consider that the temperature knob is secured The temperature can be read from the thermometer on top Wait approximately 10 minutes so that heat exchanger 2 behind the front panel is warm A surface temperature of approximately 37 C Figure 8 Tamson hot bath circulator Now check that the flow regulator is partially open indication 5 0 and the pressure regulator is almost closed this means a high pressure The pressure of the system is regulated with the pressure regulator and is indicated with the lower pressure gauge The mass flow is regulated with the flow regulator Don t let the system pressure drop below 10 bar Figure 9 Front panel of the blow system 10 When heat exchanger 2 is warm the CO cylinder can be turned open Make sure that you stand beside the blow system when opening the cylinder related to the high pressure in the cylinder and check that there is no hissing sound from a leak in the system When the electricity supply fails immediat
11. ooling the medium before expanding it is indicated in Figure 1 with nodes 1 2 3 3 and 4 Figure 2 gives a view of the block schema of the cooling cycle with the components of the refrigerator Temperature Phase change to liquid Pressure increase decrease 4 Heat Condenser Compressor Needle Cooling exchanger y valve 2 area 3 anos 3 Pressure and temperature Temperature increase decrease increase Figure 2 Block schema of the cooling cycle of a refrigerator with pre cooling The amount of heat extracted from the cooling medium by pre cooling is indicated between node 1 and 1 This amount of heat is absorbed by the cooling medium in the return line of the heat exchanger The energy increase as a consequence of the pre cooling process is indicated between node 3 and 3 A decreased vapour ratio before the cooling process starts is preferred because liquid can absorb heat by changing to vapour In case of a high vapour ratio the vapour can begin to function as an isolator between the liquid medium and the wall of the tube The isolating layer can decrease heat transfer between the tube wall and the liquid medium this means that liquid becomes unable to evaporate at the tube wall This phenomenon is called dry out 1 1 Blowsystem cycle The cooling blow system is the evaporator section of a refrigerator Instead of compressing and condensing the CO back to liquid it will be vented into the atmos
12. phere The CO will be provided by a CO vessel instead of a condenser The thermodynamic cycle of the blow system is given in the pressure enthalpy diagram of Figure 3 The continuous green line is the blow system cycle The dashed line is the imaginary refrigeration cycle which is abandoned At the state of the compressor inlet the overheated vapour is now heated to room temperature and expanded to atmospheric pressure and vented afterwards R 744 carbon dioxide reference state tat de r f rence h 200 0 kJ kg cea for i i Pressure Pression MPa Pressure Pression bar 50 550 650 NIST Enthalpy Enthalpie kJ kg ea mamaa g Aaronen n FDNY Pans a D Figure 3 Pressure enthalpy diagram for the cooling blow system cooling at 30 C 1 2 CO2 cooling blow system design A schematic overview of the design of the CO cooling blow system is given in Figure 4 The liquid CO is led from the CO bottle through a filter In the heat exchanger the liquid CO is pre cooled by the fluid in the return line Pollution filtering Pressure CO bottle 1 Temperature decrease 1 sensor Heat Needle Experiment Post heat Pressure Experiment 4 exchanger exchanger sensor Temperature Temperature increase increase Relief valve Pressure regulation Pressure and temperature decrease Temperature increase Figure 4 Schematic overview of the CO
13. reach the necessary cooling capacity e Turn the flow regulator slowly open The mass flow of the CO increases and is able to absorb more heat from the experiment e Make sure that the tubing from the experiment inlet en to the experiment outlet is properly insulated It is possible that the tubing experiences a large heat transfer as a consequence of the temperature difference with the surroundings The system doesn t reach the cooling temperature e Slowly turn the pressure regulator so that it closes a bit As a consequence of the pressure drop in the CO cooling blow system the relation of temperature and pressure in the system is lost e Turn the flow regulator maximal open en check the mass flow When the mass flow isn t larger than 1 5 g s the CO cylinder is empty and needs to be refreshed 5 Maintenance The maintenance of the CO cooling blow system will be done by technicians employed at Nikhef 14 Appendix A Theoretical mass flow calculation An indication will be given of the mass flow that is necessary to cool certain powers to a cooling temperature of 30 C The theoretical change in enthalpy during the cooling process is determined and next the mass flow is calculated ecg Bet SSS 50 Pressure Pression MPa Pressure Pression bar 0 4 4 50 100 150 200 250 300 350 400 450 500 550 600 650 700 NIST zen Enthalpy Enthalpie kJ kg eerie nena a Aaroa nan FT
14. sssssss2issecgsisaarateses baeeesi enue og niren a E eN TENE ETE ESETET 6 2 CO cooling blow systemi USAGE ce essececeseeeeceeeeseeeeeseesecsecesecseceeeeaeeseceeeeseeseeeecaecaeeeaessecneeeaeens 7 2 1 Sensors of the CO cooling blow system s esssesesesessesseesrsssrsssestssestisestrsesteseserseserseserseseese 8 2 2 Connecting the blow SyStOm wicscccceccntisshianesds toscnesceatiiershs eee chaasaanaadestoa nas ceteueapienbiiatreesiune 8 2 3 Disconne cting th DIOW System sis c icsceccciecgeaseesstasseessatnceseunnst locaudcasessnbavedsrgienebsanteessatcesedens 9 ZA Refreshing the COs Cylinder oscena a sevsccvacesinviceccuscuvduaneyecesceveveccoacene 10 25 Getting stated sesen sete cosaveess cesecssccacenscvnecsashcensecnauvaccodenuchsecoceds cvbecnavhdevnecacentevsedaueanecbeuaets 10 2 6 System settings csi cess sascasegeunavevsceancaatatoddudsctee aggcasuxpares edule ducaaeahendesuecgs bane capuchans ESEE EN TEES 11 2 7 Turning the CO cooling blow system Off cesecesseeseeeeeeseeteeeeeesecseeeaeesececeaeeseeereeaeeneeees 12 2 8 CO cooling blow system transport secip ission esiseinas eieiei E 12 3 Product aSsenDly aineinaan snein nE a EEEE a aE AEN E AES E AEAN EEEE 13 4 Faloreand repli osoren a NNER N EN E ENKE EEE 14 D Maintenance serenon n R T RAN stents 14 Appendix A Theoretical mass flow calculation ssssesesesessssesseersrstssstersrssrsesesrsrsrntststeresrsrsrererereeeere 15 Appendix B Results of reducing mass
15. the system pressure is kept above 30 10 10 bar 20 10 When the measured temperature is above the indicated temperature at the 10 20 system pressure the pressure may be lowered to 1 bar Now partly open the flow regulator 1 and the pressure regulator 5 Let the pressure drop to 0 bar on both pressure gauges Disconnect both experiment connections and the relief connection When the power of the Tamson hot bath circulator is off pull the plugs from the sockets Figure 6 Front panel 2 4 Refreshing the CO2 cylinder Make sure that the blow system is disconnected paragraph 2 3 from the experiment 2 4 relief 9 and electricity supply Place the blow system so that there is enough room to lower the ramp and to position the cylinder trolley in front of the ramp 11 Lock the front wheels of the blow system and disconnect the cylinder connection 7 Next lower the ramp and place the cylinder trolley in front of the ramp Loosen the cylinder holder strap Carefully turn the cylinder of its plateau 12 down the ramp into the cylinder trolley Fasten the strap of the cylinder trolley Position the new CO cylinder in the trolley before the ramp Loosen the strap of the trolley and carefully turn the cylinder up the ramp onto the cylinder plateau Next fasten the strap Figure 7 Cylinder connection with nylon of the cylinder holder round the cylinder Pick up the ramp ring and secure it Connect the cyl
16. ts The minimal CO mass flow of the CO cooling blow system for certain experiment powers is determined A thin tube is connected to the CO cooling blow system power is added to the tube with a power supply At a constant power the mass flow is reduced to the point at which the mass flow is too little to be able cool the thin tube First the mass flow is established a bit above the theoretical mass flow Next the power is added and the mass flow is reduced until an unstable state is reached Time Action Mass flow 14 18 Heat exchanger 1 is warm 37 3 C 14 20 Cylinder open pressure set on 12 bar and flow at indication 10 3 3 14 22 Calibrate load 0 6 Ohm 14 24 Pressure much to high flow reduced to indication 2 0 5 14 26 System and experiment are cold adjust the pressure to 12 bar 0 5 14 27 Reduce flow at 0 Watt indication 1 10 0 1 0 05 14 32 Flow instituted at 2 0 0 5 0 1 14 32 Add power accidently 300 Watt 14 34 Add power I 5 8 A 20 Watt indication 1 20 0 3 0 1 14 39 Indication 1 15 0 25 0 1 14 43 Indication 1 10 0 20 1 14 48 Indication 2 0 0 50 1 14 48 Add power I 9 1 47 1 Watt 14 49 Power off wait until T4 is cooled down 14 56 Add power I 9 1 47 1 Watt adjust pressure to 12 bar 14 58 Indication 1 20 0 35 40 1 15 00 Power off wait until T4 is cooled down 15
17. ven Table 1 Metering valve settings at approximately 30 C P Watt T C p bar dm g s Metering valve indication 20 30 1341 0 3 40 1 1 15 50 30 131 0 4 0 1 1 20 100 30 131 0 7 0 05 2 07 200 30 1341 1340 1 3 12 11 2 7 Turning the CO2 cooling blow system off To turn off the CO cooling blow system close the CO cylinder Open the flow regulator partially so that the high pressure behind the valve can leave the system When the system has warmed up as indicated in paragraph 0 the power of the Tamson hot bath circulator can be turned off 2 8 CO2 cooling blow system transport By transport of the CO cooling system always remove the CO cylinder from the system The blow system can be moved by means of the wheels of the system Make sure that the blow system is disconnected properly as indicated in paragraph 2 3 and that the CO cylinder is removed from the cylinder plateau and thus from the blow system paragraph 2 4 The weight of the CO cylinder is above 25 kg move the cylinder with at least two persons Transport of the CO cylinder must be done with a cylinder trolley 12 3 Product assembly A view of CO cooling blow system assembly is given in Figure 10 and the parts list is given e Frame of Bosch profile 45 X 45 mm e 2castors with polyurethane band e 2casters with polyurethane band e Polyethylene box 16 litre e Tamson hot bath circulator e 2 blue
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