TWI612268B - Heat exchange structure - Google Patents

Description

Heat exchange structure

The present invention relates to a water leaching sterilization apparatus, and more particularly to a heat exchange structure which is provided in a kettle body of a sterilizing apparatus for raising or lowering temperature of water inside the kettle body.

For all kinds of packaged foods and medical supplies, such as canned foods, bottled foods or bagged foods, the sterilization can be carried out after sterilization. The conventional sterilization kettles can be roughly classified into steam sterilization according to the different sterilization methods. Different forms such as kettle and water sterilizing kettle.

A water-rinsing sterilization kettle comprises a kettle body, a pipeline group, a circulation pump, a heater and a control unit, wherein the kettle system is arranged in a horizontally-shaped circular barrel for sterilizing And a kettle door at one end of the kettle body for closing the kettle body, the control unit is composed of a microcomputer and an electronic and motor component for controlling the operation of various components of the sterilization kettle, and the pipeline group is used for guiding water and steam to the kettle. Flowing between components such as body and heater, the pipeline group has a plurality of sprinkler pipes, a water pipe, a return pipe, a steam inlet pipe, a steam pipe and a steam pipe, and the sprinkler pipes are distributed in the kettle body. The inner circumference of the upper part of the section, the sprinkler pipe is provided with a plurality of sprinkling holes, according to which the water is sprayed inside the kettle body, and the sprinkling pipes are gathered at one end to be connected with the water pipe, and the water pipe is connected to the circulation pump through the heater. One end of the return pipe is connected with the circulation pump, and the other end is connected with the bottom edge of the inner part of the kettle body. The circulation pump is used for extracting the water liquid at the bottom edge of the kettle body and pumping it to the sprinkler pipe, according to the circulation of the water liquid, the end of the steam inlet pipe It is connected to a high-temperature steam supply such as a boiler, and the other end is heated. Communicates, at one end in communication with the output steam pipe heater, The other end is connected with the steam pipe, and the steam pipe is disposed at the bottom edge of the interior of the kettle body. According to the high temperature steam passing through the heater, the steam is injected into the interior of the kettle body, and the steam is passed through the heater to the water pipe. The water to be transported forms a heat exchange, and the sprinkling water pipe ejects the high-temperature water liquid, whereby the sterilized material placed inside the kettle body is heated and sterilized.

When the sterilized materials such as packaged foods and medical supplies are sterilized by the above-described conventional water sterilizing sterilizer, the sterilized material is placed on the inside of the kettle body by the carrier, and the kettle door is closed to the inside of the kettle body. The closed state is formed, and then an appropriate amount of water is injected into the interior of the kettle body, and the injected water liquid is accumulated in the bottom edge of the interior of the kettle body, and the circulating pump transports the accumulated water liquid to the sprinkler pipe through the heater, and the water liquid is transferred by the water. When the water pipe is transported through the heater, the water is heated by heat exchange with the high-temperature steam passing through the heater, and the heated hot water flows to the sprinkler pipe and is sprayed inside the kettle body, and the hot water sprayed from the sprinkler pipe falls on the bottom edge of the kettle body, and again It is pumped to the sprinkler pipe by the circulating pump, and the water liquid is heated and sprayed by the operation of the circulating pump, so that the sterilized material is heated to reach the appropriate temperature and maintained for a period of time, thereby performing the sterilization operation, and the high-temperature steam is transported after passing through the heater. The steam pipe to the inner bottom edge of the kettle body is sprayed upward, thereby assisting in heating the inner space of the kettle body.

The conventional water sterilizing kettle uses a pipeline group to transport water inside the kettle body through a heater located outside the kettle body or a mixer of steam and water, so that the water is heated to a high temperature hot water and then sent to the interior of the kettle body for spraying. The heater and the complicated pipeline configuration make the overall equipment of the water-jet sterilizer take up a large space, and the heat energy is easy to be externally lost.

In order to improve the problem that the conventional water-jet sterilizer takes up a large space due to the heater and the corresponding pipeline configuration, the main object of the present invention is to provide a heat exchange structure for accumulating the body of the sterilizing device by the heat exchange structure. Water warms or cools down, thereby reducing overall sterilization The space occupied by the device and the loss of thermal energy.

In order to meet the intended purpose, the present invention is a heat exchange structure comprising an input pipe, an output pipe and a heat exchanger, wherein the heat exchanger is disposed in a kettle body of the sterilization device, and the kettle body is disposed horizontally. a circular barrel body, the kettle body forming a water storage area at the bottom for accumulating water for sterilization operation, the kettle body forming a sterilization area above the water storage area for accommodating the sterilized material; the heat exchange Provided in the water storage area, the input pipe and the output pipe are respectively connected to the heat exchanger and the medium device for passing the medium through the heat exchanger, and the heat exchanger constitutes a passage through which the medium passes, according to The water inside the water storage cylinder accumulates water from the inside of the kettle body to raise or lower the temperature.

The heat exchange structure as described above, wherein the heat exchanger mainly comprises a first socket, a second socket, a first connecting pipe and a second connecting pipe, and an inlet is formed inside the first connecting seat a chamber and an outlet chamber, the input tube is in communication with the inlet chamber, the outlet tube is in communication with the outlet chamber, and a second chamber is formed inside the second socket, the first connecting tube is respectively opposite to the inlet chamber and the middle chamber In communication, the two ends of the second connecting pipe are respectively connected to the outlet chamber and the middle chamber, thereby forming a passage through which the medium passes.

The heat exchange structure as described above, wherein the heat exchanger comprises a first socket, a second socket, a first adapter tube, a second adapter tube and a plurality of transmission tubes, the first socket Forming an inlet chamber, an outlet chamber and a relay chamber, the input tube is in communication with the inlet chamber, the outlet tube is in communication with the outlet chamber, and the second socket forms a second intermediate chamber, and the first connecting tube has two ends respectively And communicating with the inlet chamber and the middle chamber, the two ends of the second connecting tube are respectively connected to the outlet chamber and the middle chamber, and the relay chamber communicates with each of the middle chambers by the conveying tubes, thereby forming the medium passing through aisle.

a heat exchange structure as described above, wherein one end of the input pipe is connected to the heat exchanger, and the other end branches to form a first branch pipe and a second branch pipe, and the first branch pipe is connected to a first medium device, The second branch pipe is in communication with a second medium device, the first branch pipe is provided with a third control valve for controlling on/off of the first branch pipe, and the second branch pipe is provided with a fourth control valve. The fourth control valve is configured to control on/off of the second branch pipe; one end of the output pipe is connected to the heat exchanger, and the other end branches to form a third branch pipe and a fourth branch pipe, the third branch pipe and the third pipe a medium device is connected, the fourth branch pipe is in communication with the second medium device, the third branch pipe is provided with a fifth control valve for controlling on/off of the third branch pipe, and the fourth branch pipe is provided A sixth control valve for controlling on/off of the fourth branch.

The heat exchange structure as described above, wherein the kettle body is provided with a water storage tank, and the water storage area is formed in the water storage cylinder, and at least one drainage tube is disposed at the top end of the water storage cylinder to communicate with the sterilization zone.

The present invention relates to a heat exchange structure of a sterilization apparatus, comprising a plurality of input tubes, a plurality of output tubes and a plurality of heat exchangers, wherein the heat exchanger is disposed in a kettle body of the sterilization apparatus, and the kettle body is horizontally a circular barrel body, the kettle body forming a water storage area at the bottom for accumulating water for sterilization operation, the kettle body forming a sterilization area above the water storage area for accommodating the sterilized object; The heat exchanger is disposed in the water storage area, and each of the input tubes is respectively connected to each of the heat exchangers, and each of the output tubes is respectively connected to each of the heat exchangers, and the input tubes are collected and connected to the medium device, and the outputs are respectively The tube collects and communicates with the medium device, and each of the input tubes is respectively provided with a first control valve, and each of the first control valves is used for controlling the on/off of each of the input tubes, thereby controlling the flow of the medium to each of the heat exchangers. .

The heat exchange structure of the sterilizing device as described above, wherein each of the output pipes is respectively provided with a second control valve, and each of the second control valves is used for controlling the on/off of each of the output pipes, thereby controlling to leave each The medium of the heat exchanger is returned to the media device.

(1) ‧ ‧ ‧ body

(2) ‧ ‧ bactericide

(3) ‧ ‧ rails

(4) ‧ ‧ sprinkler pipes

(5) ‧ ‧ water storage area

(6) ‧‧‧sterilization area

(7) ‧‧‧pipe group

(8) ‧ ‧ Circulating pump

(9) ‧ ‧ water storage

(91)‧‧‧Drainage tube

(12)‧‧‧ Input tube

(122)‧‧‧First tube

(124)‧‧‧Second tube

(13)‧‧‧ Output tube

(132) ‧ ‧ third tube

(134) ‧ ‧ fourth tube

(14)‧‧‧First control valve

(15)‧‧‧Second control valve

(16)‧‧‧ Third control valve

(17)‧‧‧fourth control valve

(18)‧‧‧Fifth Control Valve

(19) ‧‧‧ sixth control valve

(20) ‧‧ ‧ heat exchanger

(21) ‧‧‧first socket

(211)‧‧‧ Entrance Room

(212)‧‧‧Exports room

(213) ‧ ‧ relay room

(22)‧‧‧Second socket

(221) ‧‧‧中室

(23) ‧‧‧First connection

(24) ‧‧‧Second connection

(25)‧‧‧Transport tube

The first figure is a cross-sectional view of the first embodiment of the present invention.

The second figure is a schematic front view of the first embodiment of the present invention disposed inside the kettle body.

The third drawing is a cross-sectional view of a heat exchanger according to a second embodiment of the present invention.

The fourth figure is a front view showing the third embodiment of the present invention disposed inside the kettle body.

The fifth figure is a schematic diagram of the configuration of the fourth embodiment of the present invention.

The sixth figure is a schematic diagram of the configuration of the fifth embodiment of the present invention.

The seventh figure is a schematic diagram of the configuration of the sixth embodiment of the present invention.

As shown in the first and second figures, the first embodiment of the heat exchange structure of the present invention comprises an input pipe (12), an output pipe (13) and a heat exchanger (20), wherein the heat exchanger (20) is disposed inside a kettle body (1) of the sterilization device, and the kettle body (1) is a circular barrel provided in a horizontally-shaped shape for accommodating the sterilized material (2), according to which the kettle body (1) The inside of the kettle body (1) is provided with a pair of rails (3) on both sides adjacent to the bottom for carrying the trolley (not shown) for setting the sterilized object (2), and the kettle body (1) The inner side and the top edge are respectively provided with a sprinkler pipe (4) for spraying water or steam on the sterilized object (2) to raise or lower the sterilized object (2) for sterilization operation, and the kettle body (1) The internal space forms a water storage area (5) at the bottom for accumulating water for sterilization operation, and the internal space of the body (1) forms a sterilization area (6) above the water storage area (5) for receiving The sterilized material (2) and the sterilizing equipment are provided outside the kettle body (1) Pipe group (7), one end of the pipeline group (7) is connected with the water storage zone (5), the other end is connected with the sprinkler pipe (4), the pipe group (7) is in the water storage zone (5) and the sprinkler pipe A circulating pump (8) is provided between (4) for pumping water accumulated in the water storage zone (6) to the sprinkler pipe (4).

The heat exchanger (20) is disposed in the water storage area (5), the input pipe (12) and the output pipe (13) are respectively connected to the heat exchanger (20), and the input pipe (12) is connected to a a medium device (not shown), wherein the medium device may be a boiler or a cooling water tower for supplying a medium capable of carrying heat energy such as heating steam or cooling water for cooling, and the output pipe (13) is connected to the medium device. The medium such as steam or cooling water passes through the heat exchanger (20) for exchanging heat between the medium and the water accumulated in the water storage area (5) to accumulate in the water storage area ( 5) The water is warmed or cooled.

The heat exchanger (20) mainly comprises a first socket (21), a second socket (22), a first connecting pipe (23) and a second connecting pipe (24), thereby forming a medium. Passing through the passage, the medium enters the heat exchanger (20) from the input pipe (12), and passes through the first joint (21), the first connecting pipe (23), and the second connecting pipe (24) And the second socket (22) flows out of the heat exchanger (20) by the output tube (13); wherein the first socket (21) and the second socket (22) are respectively connected to the kettle body (1) contacting, according to which the heat exchanger (20) is positioned in the kettle body (1), the input pipe (12) and the output pipe (13) are respectively connected to the first socket (21), According to the guiding medium, the heat exchanger (20) is formed, and an inlet chamber (211) and an outlet chamber (212) are formed inside the first socket (21), and the input tube (12) is connected to the inlet chamber (211). The output tube (13) is in communication with the outlet chamber (212), and a second chamber (221) is formed inside the second socket (22), and the two ends of the first connecting tube (23) are respectively associated with the inlet chamber (211) And communicating with the middle chamber (221), the two ends of the second connecting tube (24) are respectively connected with the outlet chamber (212) and the middle chamber (221), according to the Connecting seat (21), connected to the second seat (22), the first adapter tube (23) and said second connecting tube (24) configured to provide a medium through the medium passage.

When the sterilizing operation is carried out using the water leaching sterilizing apparatus of the first embodiment, the water injected into the body (1) is accumulated in the water storage area (5), and the water accumulated in the water storage area (5) The liquid level is higher than the heat exchanger (20).

When the interior of the kettle body (1) is to be heated and sterilized, steam is used as a medium through which the steam passes through the heat exchanger (20) through the inlet pipe (12) and the outlet pipe (13), and by the heat The exchanger (20) exchanges heat with the water accumulated in the water storage area (5), and the circulation pump (8) extracts the warmed water out of the water storage area (5) toward the inner top edge of the kettle body (1). The sprinkling pipe (4) is pumped, and the sprinkling pipe (4) is sprayed in the sterilizing zone (6) in a mist form to raise the temperature of the sterilized material (2), and the water sprayed from the sprinkling pipe (4) falls on the storage The water zone (5) is again heat-exchanged with the steam passing through the heat exchanger (20), and the water circulation is heated and sprayed to raise the temperature of the sterilized material (2) to a desired sterilization temperature for a certain period of time. operation.

When the sterilization is completed, to cool the interior of the kettle body (1), cooling water is used as a medium, and the cooling water passes through the heat exchanger (20) through the input pipe (12) and the output pipe (13), and The heat exchanger (20) exchanges heat with the water inside the water storage zone (5), and the circulation pump (8) pumps the cooled water to the sprinkler pipe (4) inside the kettle body (1). And being sprayed by the sprinkler pipe (4) inside the kettle body (1), the water sprayed from the sprinkler pipe (4) falling in the water storage zone (5), and again passing through the heat exchanger (20) Cooling water heat exchange, the water circulation inside the kettle body (1) is cooled and sprayed, and the internal environment of the kettle body (1) and the sterilized material (2) are cooled to reach a desired temperature, and the kettle body can be opened (1) ) Remove the sterilized material (2).

The heat exchanger (20) forms a passage through which the medium such as high-temperature steam or cooling water passes through the water storage region (5) inside the kettle body (1), and the medium and the interior of the kettle body (1) are accumulated in the storage. The water heat exchange in the water zone (5) causes the water to be heated or cooled, and then sprayed into the interior of the kettle body (1) via the sprinkler pipe (4). The heat exchanger (20) does not need to occupy the space required for equipment installation outside the kettle body (1), and the correspondence between the heat exchanger (20) and the kettle body (1) and the medium device The piping configuration is simplified, the space occupied by the overall sterilization equipment is reduced, and the heat exchange is completed in the water storage area (5) inside the kettle body (1), which can reduce the loss of thermal energy.

The second embodiment is the same as the first embodiment, and the second embodiment is the same as the first embodiment. The heat exchanger (20) of the second embodiment includes a first connection. a seat (21), a second socket (22), a first connecting pipe (23), a second connecting pipe (24) and a plurality of conveying pipes (25), thereby constituting a passage for providing a passage of the medium, so that The medium enters the heat exchanger (20) through an input pipe (12), and flows out of the heat exchanger (20) by an output pipe (13); wherein an inlet chamber is formed inside the first socket (21) ( 211) an outlet chamber (212) and a relay chamber (213), the input tube (12) is in communication with the inlet chamber (211), and the outlet tube (13) is in communication with the outlet chamber (212), the second connection Two seats (221) are formed inside the seat (22), and two ends of the first connecting pipe (23) are respectively connected with the inlet chamber (211) and a middle chamber (221), and the two ends of the second connecting pipe (34) Connected to the outlet chamber (312) and the other intermediate chamber (221), respectively, the relay chamber (213) communicates with each of the intermediate chambers (221) by means of the transfer tubes (25), thereby forming a passage for providing media passage therethrough. .

The third embodiment is changed from the first embodiment. As shown in the fourth figure, the third embodiment includes an input pipe (not shown), an output pipe (not shown), and a heat exchanger (20). The specific configuration of the input pipe, the output pipe and the heat exchanger (20) is the same as that of the first embodiment, and the heat exchanger (20) is disposed in a kettle body (1). A water storage area (5) is formed inside the kettle body (1), and the water tank (1) is provided with a water storage tank (9) formed in the water storage cylinder (9). At least one drainage tube (91) is connected to the sterilization zone (6) of the kettle body (1) at the top end of the water storage cylinder (9), and the water used for the sterilization operation enters the water storage zone (5), where The number of drainage tubes (91) can be increased or decreased as needed. The indication cannot be used as a limit on the number of the draft tube (91).

The fourth embodiment is changed from the first embodiment, and the fourth embodiment is the same as the first embodiment. The description of the first embodiment is not repeated. As shown in the fifth figure, the fourth embodiment includes a plurality of input tubes (12) and a plurality of outputs. a tube (13) and a plurality of heat exchangers (20), wherein each of the heat exchangers (20) is disposed in a kettle body (not shown) of the sterilization apparatus, and the kettle body is arranged in a horizontal shape. a barrel body which forms a water storage area at the bottom for accumulating water for sterilizing operation, and the kettle body forms a sterilizing area above the water storage area for accommodating the sterilized material; each of the heat exchangers 20) disposed in the water storage area, each of the input tubes (12) is respectively connected with each of the heat exchangers (20), and each of the output tubes (13) is respectively connected with each of the heat exchangers (20), and the input is respectively The tube (12) is collected and connected to a medium device (not shown), each of the output tubes (13) is gathered and connected to the medium device, and each of the input tubes (12) is respectively provided with a first control valve (14). Each of the first control valves (14) is configured to control an on/off state of each of the input tubes (12), thereby controlling a medium such as high temperature steam or cooling water to flow to each of the heat exchangers (20).

In the fourth embodiment, by controlling the opening and closing of each of the first control valves (14), whether the medium passes through the heat exchangers (20) is controlled, so that the opening and closing of the first control valves (14) are respectively changed. The medium can be passed through a specific heat exchanger (20) to control the rate of temperature rise or decrease of the water used for spraying inside the kettle body.

The fifth embodiment is changed from the fourth embodiment, and the fifth embodiment is the same as the fourth embodiment, and the detailed description is not repeated. As shown in the sixth figure, the fifth embodiment includes several input tubes (12) and several outputs. a tube (13) and a plurality of heat exchangers (20), wherein each of the output tubes (13) is respectively provided with a second control valve (15), and each of the second control valves (15) is used to control each of the outputs The on/off state of the tube (13), whereby the medium leaving each of the heat exchangers (20) is controlled to flow back to the medium device.

Embodiment 5 controls the conduction of each of the output tubes (13) by each of the second control valves (15) The medium is prevented from passing through a heat exchanger (20) and then flowing to the other heat exchanger (20) to improve the reliability of the medium passing back through the heat exchangers (20) to the medium device.

The sixth embodiment is changed from the first embodiment, and the sixth embodiment is the same as the first embodiment. The description of the first embodiment is not repeated. As shown in the seventh embodiment, the sixth embodiment includes an input tube (12) and an output tube ( 13) and a heat exchanger (20), wherein one end of the input pipe (12) is connected to the heat exchanger (20), and the other end branches to form a first branch pipe (122) and a second branch pipe (124). The first branch pipe (122) is in communication with a first medium device (not shown), and the second branch pipe (124) is in communication with a second medium device (not shown), the first branch pipe (122) a third control valve (16) is provided for controlling the opening/closing of the first branch pipe (122), and the second branch pipe (124) is provided with a fourth control valve (17). The fourth control valve (17) is for controlling the on/off of the second branch pipe (124).

One end of the output tube (13) is connected to the heat exchanger (20), and the other end branches to form a third branch tube (132) and a fourth branch tube (134), the third branch tube (132) and the first medium The device is connected, the fourth branch pipe (134) is in communication with the second medium device, the third branch pipe (132) is provided with a fifth control valve (18), and the fifth control valve (18) is used for controlling the third branch pipe The opening/closing of (132), the fourth branch pipe (134) is provided with a sixth control valve (19) for controlling the on/off of the fourth branch pipe (134).

Embodiment 6 controls the input pipe (12) by the third control valve (16), the fourth control valve (17), the fifth control valve (18) and the sixth control valve (18), respectively The output pipe (13) is in an on/off state between the first medium device and the second medium device, and the first medium device can be implemented as a steam boiler, and the second medium device can be implemented as a cooling water tower. When the sterilization kettle is used for sterilization, it is possible to control different media such as high-temperature steam or cooling water according to the requirements of different stages such as temperature rise/sterilization/cooling, and control the interior of the kettle body for spraying by the heat exchanger (20). Water warming Or cool down.

Further, the heat exchangers of the foregoing embodiments and the water used for sterilization are located in a water storage area inside the kettle body of the sterilization apparatus, and the heat exchanger and the water used for sterilization inside the kettle body are under the same pressure environment. The steam/cooling water for heating/cooling is isolated from the sterilizing water circulating inside the kettle body, and the steam/cooling water does not mix into the sterilizing water contacting the sterilized material, thereby ensuring that the sterilizing water is clean and free from contamination.

(1) ‧ ‧ ‧ body

(2) ‧ ‧ bactericide

(3) ‧ ‧ rails

(4) ‧ ‧ sprinkler pipes

(5) ‧ ‧ water storage area

(6) ‧‧‧sterilization area

(7) ‧‧‧pipe group

(8) ‧ ‧ Circulating pump

(20) ‧‧ ‧ heat exchanger

Claims (3)

A heat exchange structure of a water leaching sterilization device comprises an input pipe, an output pipe and a heat exchanger, wherein the heat exchanger is arranged in a kettle body of the water leaching sterilizing device, and the kettle body is horizontally a circular barrel body, the inner space of the kettle body forms a water storage area at the bottom for accumulating water for sterilization operation, and the kettle body forms a sterilization area above the water storage area for accommodating the sterilized object; The heat exchanger is disposed in the water storage area, and the input pipe and the output pipe are respectively connected to the heat exchanger and the medium device for passing the medium through the heat exchanger, and the heat exchanger constitutes a passage through which the medium passes. According to the inside of the water storage cylinder, the water from the inside of the kettle body is heated or cooled; one end of the input pipe is connected to the heat exchanger, and the other end branches to form a first branch pipe and a second branch pipe, the first The branch pipe is in communication with a first medium device, and the second branch pipe is in communication with a second medium device, the first branch pipe is provided with a third control valve for controlling on/off of the first branch pipe, The second branch is provided with a fourth control valve, the fourth a control valve is configured to control on/off of the second branch pipe; one end of the output pipe is connected to the heat exchanger, and the other end branches to form a third branch pipe and a fourth branch pipe, the third branch pipe and the first media device Connected, the fourth branch pipe is in communication with the second medium device, the third branch pipe is provided with a fifth control valve for controlling on/off of the third branch pipe, and the fourth branch pipe is provided with a sixth pipe a control valve for controlling on/off of the fourth branch. The heat exchange structure of the water sterilizing apparatus according to claim 1, wherein the heat exchanger mainly comprises a first socket, a second socket, a first connecting pipe and a second connecting An inlet chamber and an outlet chamber are formed inside the first socket, and the inlet tube is connected to the inlet chamber The outlet tube is connected to the outlet chamber, and a second chamber is formed in the second socket. The two ends of the first connecting tube are respectively connected to the inlet chamber and the middle chamber, and the two ends of the second connecting tube are respectively The outlet chamber and the intermediate chamber are in communication, thereby forming a passage through which the medium passes. The heat exchange structure of the water sterilizing apparatus according to claim 1, wherein the heat exchanger comprises a first socket, a second socket, a first connecting pipe and a second connecting pipe. And a plurality of transfer tubes, wherein the first socket forms an inlet chamber, an outlet chamber and a relay chamber, the input tube is in communication with the inlet chamber, the outlet tube is in communication with the outlet chamber, and the second socket is internally formed In the middle chamber, the two ends of the first connecting pipe are respectively connected with the inlet chamber and the middle chamber, and the two ends of the second connecting pipe are respectively connected with the outlet chamber and the middle chamber, and the relay chamber borrows each of the conveying tubes and the respective The middle chamber is connected to form a passage through which the medium passes.