Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
  • F16L55/00—Devices or appurtenances for use in, or in connection with, pipes or pipe systems
  • F16L55/10—Means for stopping flow in pipes or hoses
  • F16L55/103—Means for stopping flow in pipes or hoses by temporarily freezing liquid sections in the pipe
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
  • F25D15/00—Devices not covered by group F25D11/00 or F25D13/00, e.g. non-self-contained movable devices

Definitions

• the invention relates to a pipe freezer for freezing a pipeline carrying freezable media upstream and / or downstream of a pipeline section to be separated, with a refrigerant circuit which is hermetically sealed from the environment and which has a condenser, a downstream throttle element and at least one connected to it Has pliers, the jaws of which, in the closed position, form a pliers mouth, which comes into thermal contact with a tube, each contain a hollow body acting as an evaporator and are provided with an inlet and an outlet for the refrigerant.
• tube freezers of the type mentioned at the outset have been developed, the main feature of which is a refrigerant circuit which is hermetically sealed from the environment. If sleeves or tongs are used in such tube freezers, which are open to form a cavity with the tube, an adequate seal of the sleeve or tongs to the outer wall of the tube must be present. However, a secure seal can only be achieved with great effort and is therefore not entirely unproblematic. Therefore, the use of a pair of pliers is more suitable, the jaws of which contain a completely closed cavity with an inner wall which can be brought into contact with the pipe, as described in DE-GM 87 15225. Although the heat transfer from the tube into the cavity is slightly worse than in the case of a pair of pliers with an open cavity because of the inner wall between them, this disadvantage can be caused on the one hand by
• a capillary tube is used as a throttling device in this tube freezer to adjust the refrigerant mass flow, the tube length of each tube depending on the setting range of the thermostat used and the properties of the evaporator, compressor and condenser existing refrigerant circuit must be determined experimentally. That is, Because of the capillary tube length which has been determined once and cannot be changed thereafter, the cooling capacity remains fixed. The optimum evaporator charge can therefore only be achieved in a very specific operating state.
• the throttle element is a thermostatic expansion valve, the sensor of which measures the temperature of the refrigerant in the return line leading from the tongs to the condenser.
• the thermostatic expansion valve known per se which is used according to the invention for a tube freezer, permits regulation.
• the overheating at the end of the evaporator is used as a control variable for controlling the expansion valve.
• the valve With increasing overheating the valve opens for a larger mass flow of the refrigerant, with falling overheating it closes to limit the mass flow of the refrigerant.
• the hollow body acting as an evaporator in the tongs is optimally used because its heat exchange surface in every operating
• E SATC ⁇ ⁇ F state the maximum possible amount of heat is exceeded and can thus flow away. Seen from the refrigerant side, this means that the entire available heat exchange surface must always be wetted by the evaporating refrigerant.
• the thermostatic expansion valve With the help of the thermostatic expansion valve, the filling of the evaporator is now always controlled in such a way that, regardless of the prevailing temperature difference, which is very high at the beginning of cooling and relatively low after the desired freezing temperature has been reached, optimal filling of the evaporator is achieved without overfilling leading to the backflow of unevaporated refrigerant to the compressor. That is, due to the regulation of the refrigerant mass flow through the thermostatic expansion valve, only superheated steam is present in the return line leading from the tongs to the liquefier.
• the capacity of the system is not determined by the physical conditions in the freezer state, but is designed independently of it so that a rapid cooling of pipes, even those with a large diameter, is possible.
• the thermostatic expansion valve regulates the mass flow in such a way that it is greatest when there is a high temperature difference between the tongs and the pipe at the beginning of the cooling process and is reduced accordingly until the nominal freezing temperature is reached in the final state, since then the temperature difference limit is considerably lower and thus a correspondingly lower mass flow is only required.
• the temperature is correspondingly steep
• the cooling capacity of the tube freezer is preferably essentially determined by the amount of heat that can be dissipated via the tongs at the highest temperature difference, the width of the pincer mouth surrounding the tube being at least 0.9 times its diameter. This is because the pipe freezer according to the invention can be used particularly advantageously when the pliers jaws cover a pipe section over a surface area, the axial length of which is at least 0.9 times its outer diameter.
• the expansion valve is arranged in the pliers. In this way, heat and pressure losses are avoided, which can occur in a line between the expansion valve and the pliers. Because in this development the evaporation takes place directly behind the expansion valve in the hollow bodies of the jaws.
• expansion valves which can continuously reduce their opening width to the closed position, are very expensive, since the construction is very complex and complicated.
• expansion valves of this type which have only a limited control range are considerably cheaper, ie they do not have a minimum opening width If you want to use such inexpensive expansion valves in the pipe freezer according to the invention for cost reasons, the desired rapid cooling is still obtained, but in the final state the danger of overfilling the return line can occur , since the expansion valve in the lowest operating point of its control range still delivers more refrigerant mass flow than is required for the evaporation in the tongs.
• a further embodiment of the invention is characterized in that the evaporator is additionally formed from the supply line leading to the tongs, the minimum volume of which is determined, given the total volume of the cavities of the tongs jaws the refrigerant has essentially evaporated at the lowest operating point of the control range specified by the thermostatic expansion valve at the beginning of the return line.
• the feed line from the expansion valve to the tongs thus serves - with a low and correspondingly slow mass flow - as a "pre * evaporator or buffer, in which part of the refrigerant evaporates before the tongs so that it reaches the
• the outlet from the pliers is completely evaporated, which avoids the risk of overfilling and thus a liquid hammer in the compressor.
• heat is extracted not only from the pipe but also from the environment, the refrigerant becomes a little bit from the expansion valve to the pliers This heat loss can, however, be accepted in view of the considerable cost savings in the expansion valve.
• two pliers can be connected in parallel; >. be by connecting the inlet of the first jaw to a feed line, the outlet of the first jaw to the inlet of the second jaw and the outlet of the second jaw to the return line for each pair of pliers.
• Each pair of pliers is preferably connected to the thermostatic expansion valve via a separate feed line.
• two pliers are connected in series, in that the inlet of the first jaw of the first pliers with the feed line, the outlet of the first jaw with the inlet of the second jaw of the first pliers, and the outlet of the second jaw of the first pliers with the inlet of the first jaw of the second pliers, the outlet of the first jaw is connected to the inlet of the second jaw of the second pliers and the outlet of the second jaw of the second pliers is connected to the return line.
• the parallel connection has the advantage that the same evaporation temperature prevails in both tongs, but a total of four supply and return lines are required. In contrast, only one supply and one discharge line are connected to the pair of pliers in the series connection, which can be advantageous in some applications due to the limited space available. However, the evaporation temperature is then not the same in both tongs, but is somewhat higher in the tongs downstream, so that the freezing takes a little longer there.
• the feed and discharge lines should preferably consist of cold-resistant hoses, for example of cold-resistant rubber or of polyamide with a rubber cover.
• thermostatic expansion valve should preferably be set to a temperature difference of 5 ° K.
• a liquid separator is connected to the return line leading to the condenser. This is only an additional security measure to protect a compressor.
• Fig. 1 is a block diagram of the
• ERSA - t.- i. Fig. 4 is a diagram showing the operation of the expansion valve used in the first and second embodiment
• FIG. 5 shows the connection of the two tongs to a third embodiment of a pipe freezer
• Fig. 7 is a diagram showing the operation of the expansion valve used in the third and fourth embodiments.
• a first embodiment of the tube freezer with the refrigerant circuit is shown schematically as a block diagram, which is hermetically sealed from the environment.
• a compressor 4 serves to compress and transport the refrigerant and is connected to a condenser 10 via an oil separator 6.
• the oil filtered out of the refrigerant by the oil separator 6 is returned to the compressor 4 via an oil return line 8.
• a fan 12 ensures improved heat dissipation from the condenser 10.
• the refrigerant is transported from the condenser 10 to a thermostatic expansion valve 20 via a collecting container 10, a dryer filter 16 and a sight glass 18. At the entrance to the thermostatic expansion valve 20, the refrigerant has a temperature of approximately + 28 ° C.
• the refrigerant is expanded by the expansion valve 20 to a pressure of approximately 1.66 kp / cm 2 and reduced to a temperature of approximately -35'C.
• a T-connector 22 is connected to the expansion valve 20, from which two supply hoses 24, 24 "lead to two pliers 26, 26 '.
• the supply hoses 24, 24 * are preferably made of cold-resistant rubber or polyamide with rubber cover and have at least a length of 2m and an inner diameter of 7.9mm.
• the structure of the pliers 26, 26 'in detail is shown in FIG. 2, the pliers 26 being shown.
• the main component of the pliers are two jaws 28, 30, which together form a pliers mouth 40 that can be placed on a tube.
• Each jaw 28, 30 contains a cavity of approximately 48 cm 3 , to each of which an inlet 32 and 36 and an outlet 34 and 38 lead.
• the jaws 28, 30 are articulated to one another via a connecting joint 42 which is provided with a spring (not shown) which generates a clamping pressure.
• Each jaw 28, 30 terminates in a handle 48, 49 protruding beyond the connecting joint 42.
• the pliers jaw 40 is formed by hollows 50, 51 formed in each jaw 28, 30.
• Half-shells (not shown) can be releasably inserted into each trough 50, 51 and can be exchanged in order to enable adaptations to different pipe diameters of a pipe to be repaired.
• each inlet 32 and 36 and each outlet 34 and 38 is designed as a connecting piece.
• FIG. 1 shows both pliers 26, 26 'are connected in parallel.
• the pliers 26, 26 ' The associated supply hose 24 or 24 'is connected to the inlet 32 or 32' of the first jaw 28 or 28 '.
• the outlet 34 and 34 * of the first jaw 28 or 28 ' is at each pliers 26, 26' to the inlet 36 or 36 'of the i ze s jaw 30 or 30' and the outlet 38 and 3 with a Return line 60 or 60 'connected.
• the cavities in the pliers jaws 28, 28 ', 30, 30' act as evaporators, in which the refrigerant evaporates completely at a temperature of approximately -32 ° C., so that through the two return lines 60, 60 'only Steam is carried. Possibly. a portion of the refrigerant is already evaporating in the two supply hoses 24, 24 * in front of the pliers 26, 26 ', which will be described in more detail below.
• both return line hoses 60, 60' lead to a T-connector 62, which connects them to a single suction gas line 68.
• the return line hoses 60, 60 * can preferably consist of the same material as the line line hoses 24, 24 '.
• an expansion valve sensor 64 measures the temperature, which is transmitted as an electrical signal to the thermostatic expansion valve 20 via a sensor line 66.
• the thermostatic expansion valve is set to a temperature difference of 5 * K.
• the vaporous refrigerant has a Tempera ⁇ ture of about -30 ⁇ C and a pressure of about 2.03 kgf / cm 2.
• a filling control connection 70 is connected to the common suction gas line 68.
• the suction gas Line 68 leads to a liquid separator 72, which is installed in the compressor 4 as an additional safeguard against liquid hammer. The refrigerant is then finally returned to the compressor 4 by the liquid separator 72.
• both pliers 26, 26 * can also be connected in series, as shown in FIG. 3.
• This embodiment differs from the one described above in that in total only one supply hose 24 and one return hose 60 are connected to the pair of pliers 26, 26 ', so that the T-connectors 22 and 62 required in the first embodiment are omitted.
• the outlet 34 or 34' of the first jaw 28 or 28 ' is connected to the inlet 36 or 36' of the second jaw 30 or 30 '.
• the outlet 38 of the second jaw 30 of the first tong 26 is connected via a connecting hose to the inlet 32 * of the first jaw 28 'of the second tong 26'.
• the outlet 38 'of the second jaw 30' of the second pliers 26 ' is connected to the return hose 60, which is connected to the suction gas line 68 in the housing 80.
• both pliers 26, 26 'via a supply hose 24 or 24' to the thermostatic expansion valve 20 are connected.
• This arrangement is recommended when a thermostatic expansion valve 20 is used which has only a limited control range, ie cannot fall below a minimum opening width.
• such expansion valves are simpler and considerably less expensive in their construction.
• Such an expansion valve also regulates the coolant mass flow in such a way that it is greatest at a high temperature difference between tongs 26 and 26 'at the beginning of the cooling process and is reduced accordingly until the nominal freezing temperature on the pipe is reached.
• the temperature decreases rapidly at the beginning of the cooling process, while the slope of the temperature curve decreases more and more towards the final state.
• the thermostatic expansion valve 20 regulates the refrigerant mass flow, as the diagram of FIG. 4 shows schematically.
• the temperature difference is very high, e.g. B. 105 * K, if the liquid medium in the tube at the point enclosed by the pincer jaw 40 is +70 ⁇ C and should be cooled down to -35 ⁇ C.
• the minimum opening width of the above-mentioned thermostatic expansion valve 20 of a simple design is above the opening width required in the final state in the range of the freezing temperature, so that in relation to the prevailing low temperature difference, more refrigerant mass flow is always delivered than for the evaporation is required in the tongs when the freezing temperature is reached.
• Return hose 60 or 60 * occur. However, this is avoided by the fact that the evaporator is additionally formed from the supply hose 24 or 24 'leading to the pliers 26, 26'.
• the supply hose 24 or 24 'thus serves as a "pre" evaporator or buffer, in which part of the refrigerant evaporates even before the tongs 26, 26' - and the more the temperature increases, the more so in the tube approaches the evaporation temperature in tongs 26, 26 * and the temperature difference between the tube and the tongs 26, 26 'is reduced. This ensures that the refrigerant is completely evaporated when it enters the return hose 60 or 60 ', thereby avoiding the risk of overfilling and thus of a liquid hammer in the compressor 4.
• thermostatic expansion valve can also be used for the tube freezer according to the invention, which can continuously reduce its opening width up to the closed position. Then, in order to avoid heat losses, it is advisable to arrange the expansion valve directly on the pliers 26 or 26 '. Such an embodiment is shown in FIGS. 5 and 6.
• the embodiment according to FIG. 5 thus differs from the embodiment according to FIG. 1 in that instead of an expansion valve in front of the T-connector 22, a thermostatic expansion valve 20 'and 20 "is now arranged on each pair of pliers 26, 26' directly at the inlet 32 or 32 'of the first jaw 28 or 28 *.
• the associated expansion valve sensor 64' or 64 is arranged at the outlet 38 or 38 * of the second jaw 30 or 30 ' net.
• the design of this embodiment is the same as that of the tube freezer shown in FIG. 1.
• FIG. 6 shows an embodiment which differs from the embodiment according to FIG. 3 distinguishes in that the thermostatic expansion valve 20 'at the inlet 32 of the first jaw 28 of the first tong 26 and the associated expansion valve sensor 64' at the outlet 38 * of the second jaw 30 'of the second tong
• ge 26 ' is arranged. Otherwise, the structure is the same as in the embodiment according to FIG. 3.
• FIG. 7 shows the characteristic curve of the control range of the expansion valve used in the embodiments according to FIGS. 5 and 6. From this it can be seen that this thermostatic expansion valve is a valve with "ideal" control behavior. This valve differs from the valve used in the embodiment according to FIGS. 1 and 3 in that it also regulates the mass flow in the lower temperature range in accordance with the dashed curve B of FIG. 4.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Devices That Are Associated With Refrigeration Equipment (AREA)

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• 1989
  • 1989-05-17 DE DE3916025A patent/DE3916025A1/de active Granted
• 1990
  • 1990-05-17 EP EP19900907025 patent/EP0425627A1/de not_active Withdrawn
  • 1990-05-17 AU AU56535/90A patent/AU5653590A/en not_active Abandoned
  • 1990-05-17 WO PCT/EP1990/000796 patent/WO1990014550A1/de not_active Application Discontinuation

Non-Patent Citations (1)

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