JPH04126964A - Absorption device of absorption type freezing cycle - Google Patents

Abstract

PURPOSE:To prevent an occurrence of a deflection flow of absorption liquid by a method wherein a helical groove with its groove depth being more than a film thickness of absorption liquid in a specified twisting angle is formed at an inner surface of a heat transfer pipe. CONSTITUTION:An absorption device 20 is made such that a plurality of hollow heat transfer pipes 21 are disposed in a side-by-side relation between an upper chamber 4 and a lower chamber 5. An inner surface of each of the heat transfer pipes 21 is formed with a helical groove 22. The helical groove 22 has a trapezoidal section. Its twisting angle theta is set to 40 deg. to 50 deg.. Its depth (h) is set to have a value higher than a film thickness formed by the absorption liquid 3 flowing down in each of the heat transfer pipes 21. Absorption liquid 3 naturally flowing down at an inner surface of each of the heat transfer pipes 21 under its gravity action from the upper chamber 4 receives a resistance caused by the helical groove 22, flows in a helical form, rides over top portions of the grooves 22 and also flows down in a vertical direction, resulting in that the absorption liquid is expanded over an entire range of the inner surface of each of the heat transfer pipes 21 and no deflection flow is generated. A rate in which the absorption liquid 3 flows along the groove 22 and another rate in which the absorption liquid 3 rides over the top portions of the groove 22 and drops down in a vertical direction become preferable rates and then a leakage characteristics of the absorption liquid can be got quite well.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an absorber for an absorption refrigeration cycle that has been improved to improve refrigerant absorption performance.

(Prior Art) Some conventionally known absorption refrigeration cycles use water as a refrigerant and a lithium bromide solution as an absorption liquid for the refrigerant. This absorption refrigeration cycle consists of an evaporator that absorbs heat by evaporating refrigerant water under negative pressure, and an absorber that absorbs and recovers vaporized water vapor into an absorption liquid and supplies negative pressure to the evaporator. , a regenerator that heats the absorption 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 it to water and supplies it to the evaporator. It is structured as follows.

There are two types of absorbers: water-cooled ones and air-cooled ones, and the air-cooled ones have a structure as shown in Figure 4.
ing. The absorber 10 shown in the figure has upper and lower chambers 4 and 5, and between the upper and lower chambers 4 and 5, a plurality of hollow heat exchanger tubes 1 are arranged in parallel in the vertical direction. Then, the absorption liquid 3 is caused to flow down by gravity from the upper chamber 4 along the inner surface 2 of the heat exchanger tube 1 to absorb the vaporized refrigerant and drip into the lower chamber 5.

The upper chamber 4 contains steam (not shown because it is a gas) from an evaporator (not shown) and absorption liquid 3 from a regenerator (not shown).
(a concentrated solution from which water has been removed) is flowing. The absorbent liquid 3 (which is a diluted solution that has absorbed moisture) accumulated in the chamber 5 below is sent to a regenerator (not shown). Further, in order to increase the contact area with the cooling air, a large number of fins 6 are provided on the outer periphery of the heat exchanger tube 1.

(Problem to be solved by the invention) However, in the conventional example, since the inner surface of the heat exchanger tube was a smooth surface, the absorbed liquid naturally flowed down due to gravity or spread uniformly over the entire inner surface of the heat exchanger tube. However, it could not be expected that the absorbing liquid would flow downward, and a drifted flow often occurred in which the absorbing liquid was concentrated on a part of the inner surface of the heat exchanger tube. When this drift occurs, the water vapor may be directly cooled and condensed in areas where the absorption liquid does not flow, and may remain without being absorbed by the absorption liquid, or the absorption liquid may concentrate and flow down, resulting in a significant contact area with the water vapor. This has resulted in disadvantages such as a decrease in absorption performance and a decrease in cooling performance.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention allows an absorption liquid to naturally flow down by gravity along the inner surface of a plurality of hollow heat transfer tubes arranged in parallel in the vertical direction. In an absorber for an absorption-type refrigerating cycle for absorbing refrigerant vaporized in water, a spiral groove is formed on the inner surface of the heat transfer tube, the helix angle is 40° to 50°, and the groove depth is greater than or equal to the film thickness of the absorption liquid. was formed.

(Function) In the present invention, by forming a spiral groove on the inner surface of the heat exchanger tube, the absorption liquid that naturally flows down inside the heat exchanger tube spreads spirally due to the resistance of the groove. It spreads over a wide area on the inner surface and prevents the occurrence of drift.

Furthermore, in the present invention, the helix angle of the groove is set to 40° to 50°, and the depth of the groove is set to be equal to or greater than the film thickness of the absorbent liquid, so that the absorbent liquid flows spirally along the groove. The ratio and the ratio of flowing down in the vertical direction over the ridges of the grooves are suitable, and the effect of spreading the absorption liquid over the entire inner surface of the heat exchanger tube (hereinafter referred to as wettability) can be obtained extremely well.

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

FIG. 1 is a longitudinal sectional view showing the configuration of this embodiment. In the same figure, the same components as those of the conventional absorber 2 (10) shown in FIG.

As shown in FIG. 1, the absorber 20 of this embodiment, like the conventional example, has hollow heat transfer tubes 21 arranged between the lower chambers 4 and 5 so that the tube axes are vertically aligned. There are multiple numbers of 11■. Further, on the inner surface of the heat exchanger tube 21, spiral grooves 22 with a constant pitch are formed. This groove 22 has an inverted trapezoidal cross section that contracts toward the bottom, as shown in an enlarged view in FIG. 2, and its twist angle θ is set within the range of 40° to 500°. Further, the depth 1 of the groove 22 is set to be equal to or greater than the film thickness formed by the absorbing liquid 3 flowing down inside the heat transfer tube 21. Note that, as shown in the experimental results described later, the groove angle α (shown in the enlarged view of FIG. 3) is preferably around 45°.

This spiral groove 22 is formed so as to be continuous from the upper end to the lower end of the heat exchanger tube 21, and the number of grooves 22 is determined based on the relationship between the twist angle θ and the groove depth 1 with respect to the tube diameter of the heat exchanger tube 21. Determined automatically.

In the absorber 20 of this embodiment configured in this way, the absorption liquid 3 flowing down the inner surface of the heat transfer tube 21 due to gravity from the upper chamber 4 is resisted by the spiral grooves 22 and flows into a spiral shape. Since the absorption liquid spreads over a wide area and flows down in the vertical direction over the peaks of the grooves 22, the absorption liquid spreads over a wide area over the entire inner surface of the heat exchanger tube 2I, and no uneven flow occurs. Also,
The helix angle of the groove 22 is set to 40° to 50°, and the groove depth l
] is set to be greater than or equal to the film thickness of the absorbent liquid 3, the ratio of the rate of the absorbent liquid 3 spiraling along the grooves 22 and the rate of flowing down in the vertical direction over the peaks of the grooves 22 becomes a suitable ratio, and the absorbent liquid Very good wettability can be obtained.

Specifically, as shown in FIG. 1, the absorption liquid 3 accumulated at the bottom of the upper chamber 4 flows from the two end surfaces of the heat transfer tube 21 and tries to flow vertically due to the heavy horns, but it does not flow in a spiral direction. Because the absorption liquid 3 flows down over the shaped groove 22, a part of the absorption liquid 3 flows spirally along the groove 22. Therefore, heat exchanger tube 2
The absorption liquid 3 flowing down inside the heat exchanger tube 1 flows down while drawing a spiral with a pitch larger than the pitch of the grooves 22 as a whole, and as a result, the absorption liquid 3 spreads on the inner surface of the heat exchanger tube 21.

Therefore, in the heat exchanger tube 21 of this embodiment, the absorption liquid 3
The contact area between the water vapor and water vapor increases, and the water vapor absorption efficiency improves. Therefore, the negative pressure generated within the absorber 20 increases, and this negative pressure is supplied to the evaporator, thereby promoting the evaporation of water in the evaporator. Therefore, the cooling efficiency in the evaporator increases.

In the inventor's experiments related to the application, the groove depth 11 was 0.5
mm or more (because the film thickness of the absorbing liquid required to generate water vapor absorption capacity is about 0.3 mm, it is necessary to set it to 2 from this point), and the groove angle α was set to 45°. In this case, the water vapor absorption efficiency and the wettability of the absorption liquid 3 were extremely good.

(Effects of the Invention) As explained in detail above, the absorber of the absorption refrigeration cycle according to the present invention has a spiral groove formed on the inner surface of the heat exchanger tube, so that the absorption liquid that naturally flows down inside the heat exchanger tube can be absorbed by the absorber. Since the absorption liquid flows down while spreading in a spiral shape due to the resistance of the groove, the absorption liquid can be spread over a wide range on the inner surface of the heat exchanger tube, and the occurrence of uneven flow of the absorption liquid can be prevented.

Furthermore, in the present invention, the helix angle of the groove is set to 40° to 50°, and the groove depth is set to be equal to or greater than the film thickness of the absorbent liquid, thereby increasing the rate at which the absorbent liquid flows spirally along the groove. The rate at which the absorbent liquid flows down in the vertical direction over the ridges of the groove is a suitable rate, and the wettability of the absorbent liquid can be improved. Therefore, the contact area between the absorption liquid and the refrigerant can be increased, the refrigerant absorption performance can be improved, and the cooling efficiency can be improved.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing the structure of an embodiment of an absorber in an absorption refrigeration cycle according to the present invention, FIG. 2 is an enlarged sectional view of a heat exchanger tube in the same embodiment, and FIG. 3 is an inside view of the heat exchanger tube. FIG. 4 is a longitudinal sectional view of a conventional absorber. 3...Absorbing liquid 4,5...Chamber...Fin 0...Absorber■...Heat transfer tube...Groove θ...Twisting angle

Claims (1)

[Claims] An absorption type refrigeration cycle in which an absorption liquid is allowed to flow down by gravity along the inner surface of a plurality of hollow heat transfer tubes arranged in a vertical direction, and the vaporized refrigerant is absorbed into the absorption liquid. In the absorption refrigeration cycle, a spiral groove having a twist angle of 40° to 50° and a groove depth equal to or greater than the film thickness of the absorption liquid is formed on the inner surface of the heat transfer tube. vessel.