JPH0726773B2 - Absorption refrigeration cycle absorber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an absorber of an absorption refrigeration cycle, which has been improved to improve the absorption performance of a refrigerant.

(Prior Art) Some conventionally known absorption refrigeration cycles use water as a refrigerant and a lithium bromide solution as an absorption liquid of the refrigerant. This absorption refrigeration cycle includes an evaporator that evaporates water of a refrigerant in a negative pressure and absorbs heat, and an absorber that absorbs vaporized water vapor into an absorbing liquid and collects the same and supplies a negative pressure to the evaporator. And a regenerator that heats an absorbing liquid that has absorbed water in the absorber to separate water vapor, and a condenser that cools the water vapor separated in the regenerator and returns the water to the evaporator. It is configured to

The absorber is classified into a water-cooled type and an air-cooled type, and the air-cooled type has a structure as shown in FIG. In the absorber 10 shown in the figure, chambers 4 and 5 are provided at the upper and lower sides, and a plurality of hollow heat transfer tubes 1 are vertically arranged in parallel between the upper and lower chambers 4 and 5. Then, along the inner surface 2 of the heat transfer tube 1, the absorbing liquid 3 is allowed to naturally flow down from the upper chamber 4 by gravity to absorb the vaporized refrigerant, and the dropped liquid is dropped into the lower chamber 5. Vapor (not shown because it is a gas) from an evaporator (not shown) and absorption liquid 3 (which is a concentrated solution from which water has been removed) have flowed into the upper chamber 4 from a regenerator (not shown). The absorbing liquid (which is a dilute solution diluted by absorbing water) 3 accumulated in the lower chamber 5 is sent to a regenerator (not shown). Also,
A large number of fins 6 are provided on the outer periphery of the heat transfer tube 1 in order to increase the contact area with the cooling air.

(Problems to be Solved by the Invention) However, in the above-mentioned conventional example, since the inner surface of the heat transfer tube was a smooth surface, the absorbing liquid that naturally flows down due to gravity flows down while uniformly spreading over the entire inner surface of the heat transfer tube. It was not possible to expect this, and there was often a case in which the absorbing liquid concentratedly flowed on a part of the inner surface of the heat transfer tube. When this uneven flow occurs, the steam is directly cooled and condensed in the portion where the absorbing liquid does not flow, and stays without being absorbed by the absorbing liquid, or the absorbing liquid concentrates and flows down. There was a problem such as a decrease in absorption performance and a decrease in cooling performance.

(Means for Solving the Problems) In order to solve the above problems, the present invention is to allow gravity to flow down an absorbing liquid along the inner surfaces of hollow heat transfer tubes that are arranged in parallel in the vertical direction. In the absorber of the absorption refrigeration cycle for absorbing vaporized refrigerant, the inner surface of the heat transfer tube has a twist angle of 40 ° to 50 °, and a groove depth of a spiral shape having a film thickness of the absorbing liquid or more. The groove is formed.

(Operation) In the present invention, since the spiral groove is formed on the inner surface of the heat transfer tube, the absorbing liquid that naturally flows down in the heat transfer tube flows down while spreading spirally due to the resistance of the groove. It spreads over a wide area on the inner surface and can prevent uneven flow.

Furthermore, the present invention, by setting the twist angle of the groove to 40 ° to 50 ° and setting the groove depth to be equal to or more than the film thickness of the absorbing liquid, the ratio of the absorbing liquid flowing spirally along the groove and A suitable ratio is a ratio that the liquid flows vertically over the crests of the groove, and an action (hereinafter referred to as wettability) in which the absorbing liquid spreads over the entire inner surface of the heat transfer tube can be obtained very well.

(Example) Hereinafter, one example of an absorber of an absorption refrigeration cycle according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a vertical sectional view showing the structure of this embodiment. In the figure, the same components as those of the conventional absorber 10 shown in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 1, in the absorber 20 of this embodiment, a plurality of hollow heat transfer tubes 21 are arranged between the upper and lower chambers 4 and 5 so that the tube axes coincide with each other in the vertical direction, as in the conventional example. It is set up. And
A spiral groove 22 having a constant pitch is formed on the inner surface of the heat transfer tube 21. The groove 22 has an inverted trapezoidal cross section that contracts toward the bottom as shown in an enlarged view in FIG. 2, and the twist angle θ is set within the range of 40 ° to 50 °. Also,
The depth h of the groove 22 is set to be equal to or larger than the film thickness formed by the absorbing liquid 3 flowing down in the heat transfer tube 21. The groove angle α (shown in the enlarged view of FIG. 3) is preferably around 45 °, as will be shown by the experimental results described later.

The spiral groove 22 is formed so as to be continuous from the upper end to the lower end of the heat transfer tube 21, and the number of the grooves 22 is automatically determined from the relationship between the twist angle θ with respect to the tube diameter of the heat transfer tube 21 and the groove depth h. To be decided.

In the absorber 20 of the present embodiment configured in this way,
The absorbing liquid 3 that naturally flows down from the upper chamber 4 by gravity on the inner surface of the heat transfer tube 21 flows in a spiral shape under the resistance of the spiral groove 22 and also flows downward in the vertical direction beyond the ridges of the groove 22. Therefore, the absorbing liquid does not spread over a wide area on the entire inner surface of the heat transfer tube 21 and uneven flow does not occur. Further, by setting the twist angle of the groove 22 to 40 ° to 50 ° and setting the groove depth h to be equal to or larger than the film thickness of the absorbing liquid 3, the ratio of the absorbing liquid 3 flowing spirally along the groove 22 and the groove A suitable ratio is a ratio of flowing in the vertical direction over the 22 ridges, and the wettability of the absorbing liquid can be extremely excellent.

Specifically, as shown in FIG. 1, the absorbing liquid 3 accumulated on the bottom surface of the upper chamber 4 flows from the upper end surface of the heat transfer tube 21,
It tries to flow vertically due to gravity, but spiral grooves
Part of the absorbing liquid 3 flows over the groove 22 in order to flow over the 22.
Spirally flows along. Therefore, the absorbing liquid 3 flowing down in the heat transfer tube 21 flows down while drawing a spiral having a pitch larger than the pitch of the grooves 22 as a whole.
The absorbing liquid 3 spreads on the inner surface of the heat transfer tube 21. Therefore, in the heat transfer tube 21 of the present embodiment, the contact area between the absorbing liquid 3 and the water vapor is increased, and the water vapor absorption efficiency is improved. For this reason,
The negative pressure generated in the absorber 20 increases, and this negative pressure is supplied to the evaporator, thereby promoting evaporation of water in the evaporator. Therefore, the cooling efficiency in the evaporator is increased.

In the experiment conducted by the inventor of the present application, the groove depth h is 0.5 mm or more (since the film thickness of the absorbing liquid required to generate the water vapor absorption capacity is about 0.3 mm, it is necessary to set the groove depth h or more. If the groove angle α is 45 °, the water vapor absorption efficiency and the wettability of the absorbing liquid 3 are extremely good.

(Effects of the Invention) As described in detail above, the absorber of the absorption refrigeration cycle according to the present invention has the spiral groove formed on the inner surface of the heat transfer tube, so that the absorption liquid that naturally flows down in the heat transfer tube is Since it flows downward while spreading spirally due to the resistance of the groove, it is possible to spread the absorbing liquid over a wide range on the inner surface of the heat transfer tube, and it is possible to prevent uneven flow of the absorbing liquid.

Furthermore, the present invention, by setting the twist angle of the groove to 40 ° to 50 ° and setting the groove depth to be equal to or more than the film thickness of the absorbing liquid, the ratio of the absorbing liquid flowing spirally along the groove and A preferable ratio is a ratio of flowing in the vertical direction over the crests of the groove, and the wettability of the absorbing liquid can be improved. Therefore, the contact area between the absorbing liquid and the refrigerant can be increased, the refrigerant absorbing performance can be improved, and the cooling efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing the structure of an embodiment of an absorption type refrigeration cycle absorber according to the present invention, FIG. 2 is an enlarged sectional view of a heat transfer tube in the same embodiment, and FIG. FIG. 4 is an enlarged sectional view of the groove, and FIG. 4 is a vertical sectional view of a conventional absorber. 3 ... Absorbing liquid, 4,5 ... Chamber 6 ... Fin, 20 ... Absorber 21 ... Heat transfer tube, 22 ... Groove θ ... Twist angle

Claims (1)

[Claims] 1. An absorber of an absorption refrigeration cycle for allowing gravity of an absorbing liquid to flow down along the inner surfaces of hollow heat transfer tubes arranged in parallel in the vertical direction so that the absorbing liquid absorbs vaporized refrigerant. In the inner surface of the heat transfer tube, a helix angle of 40 ° to 50 °, and a spiral groove having a groove depth of not less than the film thickness of the absorbing liquid is formed, and the absorber of the absorption refrigeration cycle. .