Refrigeration – Refrigeration producer – Sorbent type
Reexamination Certificate
1999-09-15
2001-07-03
Buiz, Michael Powell (Department: 3744)
Refrigeration
Refrigeration producer
Sorbent type
C062S494000
Reexamination Certificate
active
06253571
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a liquid distributor, a falling film heat exchanger, and an absorption refrigerating machine.
RELATED ART
Conventionally, liquid distributors for falling film heat exchangers include a dripping type one, a spraying type one and the like, and falling film heat exchangers using such liquid distributors have been widely used for evaporators, absorbers, regenerators, low temperature regenerators in absorption refrigerating machines, and low temperature regenerators in dual-effect absorption refrigerating machines. For example, in the evaporator, a multiplicity of heat exchanger tubes are arranged horizontally in a closed vessel to form banks of heat exchanger tubes. A liquid coolant being an evaporative cooling medium is made to flow down surfaces of the banks of heat exchanger tubes, and evaporation of the liquid coolant is promoted by causing an absorber connected to the closed vessel to absorb vapor. Such heat of evaporation cools a heat exchanging medium in the tubes through the heat exchanger tubes.
Evaporation occurs at a gas-liquid interface of the liquid coolant, which covers the outer surfaces of the heat exchanger tubes, and the larger a ratio of an area of portions covered by the liquid coolant, to an entire surface area of the heat exchanger tubes, the higher the evaporating performance is enhanced. The ratio of the areas is increased by uniformly feeding the liquid coolant, which forms falling liquid films, in a longitudinal direction of the heat exchanger tubes. Further, in the case where the banks of heat exchanger tubes are arranged in a plurality of rows in a vertical direction, the ratio of an area of portions covered by the liquid coolant, to an entire surface area of the heat exchanger tubes is increased for an improved performance of the evaporator by uniformly feeding the liquid coolant in the longitudinal direction of the topmost stage of the respective tube array.
Accordingly, in order to enhance the evaporating performance, it is necessary to uniformly distribute the liquid coolant, which forms falling liquid films, along the overall lengths of the heat exchanger tubes. Further, in order to form falling liquid films in a wide region with a limited amount of the liquid coolant supplied, it is important to surely distribute all the liquid coolant over the banks of heat exchanger tubes so as not to produce ineffective liquid coolant which would fall down without forming falling liquid films. In connection with this, a dripping type liquid distributor capable of surely supplying a liquid over surfaces of the heat exchanger tubes is advantageous over a spraying type one, in which a liquid is uniformly sprayed in planar manner.
Japanese Patent Unexamined Publication No. 5-172438 discloses an example of a drip type liquid distributor, in which a branch header, a distribution pipe for primary distribution, which is disposed in parallel with heat exchanger tubes, a splash preventing cover plate, and a primary liquid droplet dispersing plate in order to improve distribution of sprinkling density, that is, distributing performance.
Further, Japanese Patent Unexamined Publication No. 7-4782 discloses another drip type liquid distributor, which comprises a box-shaped primary distribution tray disposed in parallel with heat exchanger tubes, a wide secondary distribution guide body of mountain-shape arranged below the distribution tray, and block-off walls provided at four sides of a liquid receiving section in the guide member to be tray-shaped to store a liquid on a top surface thereof, thereby preventing a liquid surface from disappearing from the guide member on an upper side in the event of being installed in oblique position.
Further, as measures for preventing degradation of performance depending upon the configuration of heat exchanger tubes in the case of an absorption refrigerating machine body being installed in oblique position, Japanese Patent Unexamined Publication No. 8-159605 discloses an apparatus, in which heat exchanger tubes are formed therein with a plurality of recesses, which extend in an axial direction of the heat exchanger tubes to be discontinuously arranged extending in the axial direction.
With the above-described spray type liquid distributor, nozzles are required to be provided on the lower surface of a distribution pipe installed in parallel with the heat exchanger tubes, and spray holes having a small diameter of 4 mm or less are required for atomizing the liquid, which results in failure of spraying due to blocking-off of the spray holes by foreign matters such as metallic particles, which might be mixed in the liquid.
Further, Japanese Patent Unexamined Publication No. 5-172438 discloses a liquid distributor having such a complicated configuration that two rows of heat exchanger tubes require a single distribution pipe, a cover plate and a liquid droplet distributing plate which belong to the distribution pipe, thus the liquid distributor becoming high in cost. Further, the liquid displaying device disclosed in the Japanese Patent Unexamined Publication No. 7-4782 is many in the number of parts and complicated in construction to become high in cost because two rows of heat exchanger tubes require a single tray and a guide body having blocking-off walls at four sides thereof, and downwardly extending flashing protrusions must be provided on the respective guide bodies so as to smoothly drip a liquid.
Further, the guide body having blocking-off walls at four sides thereof is in the form of a tray, and is capable of storing the liquid on a top surface thereof. However, in the case where the guide body is inclined under the condition of installation, such inclined arrangement causes the liquid flowing out from a primary distribution tray to be moved toward the lower side of the guide body on the guide body. As a result, liquid heads in distribution holes are extremely different between the upper side and the lower side of the guide body, so that a flow rate of the liquid from dripping holes provided on the upper side of the inclined guide body decreases while the flow rate on the lower side thereof increases. In this manner, in the case where the liquid distributor is installed in inclined manner, outflowing of the liquid from the lower side of the inclined guide body can be blocked off, but distribution in a longitudinal direction remains extremely nonuniform.
Further, because the primary distribution tray is of open type, distribution of the liquid from the primary distribution tray become nonuniform due to different liquid heads in the distribution holes between the upper and lower sides of the tray in the case where the tray is installed in inclined manner.
Further, rows of heat exchanger tubes, to which a single liquid distributor can feed a liquid, is fixed in two in number in either of the liquid distributors disclosed in the above-described Japanese Patent Unexamined Publication Nos. 5-172438 and 7-4782. Accordingly, if a combination of the above two is used to try to set the number of rows of heat exchanger tubes in a falling film heat exchanger to an odd one, a liquid supplied in an amount of capable of forming falling liquid films on one row of the heat exchanger tubes falls into the bottom of the heat-exchanger without being fed onto the heat exchanger tubes, which results in waste spraying. Thus, such arrangement is low in degree of freedom in design, and thus impedes optimization, which takes performance, size and cost into account.
Further, with the liquid distributor disclosed in the above-described Japanese Patent Unexamined Publication No. 8-159605, a plurality of recesses extending in an axial direction of heat exchanger tubes are provided discontinuously on outer surfaces of the heat exchanger tubes, and so performance is not degraded due to the inclined installation. However, such effect premises that the liquid is uniformly distributed over and dripped onto the topmost stage of the heat exchanger tubes, so that such arrangement has not yet solved the above-d
Fujii Tatsuo
Miyake Satoshi
Sato Takehiro
Antonelli Terry Stout & Kraus LLP
Buiz Michael Powell
Hitachi , Ltd.
Jones Melvin
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