JPH03194370A - Heat exchanger for air conditioner - Google Patents

Abstract

PURPOSE:To still more enhance the heat efficiency of a heat exchanger to a degree exceeding conventional common sense hy positioning the fin joints left between slits in the vicinity of the intermediate parts of the stage pitches of heat transfer pipes on the windward side. CONSTITUTION:Windward heat transfer pipes 12a and leeward heat transfer pipes 12b are arranged in a zigzag pattern as a whole and the end parts of the respective heat transfer pipes are successively connected to the end parts of the other heat transfer pipes adjacent in a vertical direction and the end part of the windward heat transfer pipe 12a of the lowermost part is connected to the end part of the leeward heat transfer pipe 12b of the lowermost part in the same way to form one continuous cooling medium passage as a whole. The cooling medium from a compressor flows in a heat exchanger from an upper right-hand inlet pipe 13 to pass through the leeward heat transfer pipes 12b and subsequently passes through the windward heat transfer pipes 12a to flow out from an upper left-hand outlet pipe 14. A plurality of slits 15 are formed to fins in the central longitudinal direction of the fins so as to leave fin joints 16 having predetermined length. The fin joints 16 are positioned in the vicinity of the intermediate parts of the stage pitches of the windward heat transfer pipes 12a.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a heat exchanger for air conditioners, particularly a Rossfin tube type heat exchanger suitable for use in a condenser for heat pump heating.

[Conventional technology]

When heating a room with a heat pump type air conditioner, the indoor heat exchanger is used as a condenser.

The outdoor heat exchanger is used as an evaporator. In this case, a typical heat exchanger that can be used as a condenser is a so-called cross-fin tube heat exchanger. This type of exchanger has a large number of thin plates (fins) made of metal with good thermal conductivity (e.g. aluminum, copper, etc.) arranged side by side at a predetermined interval, and has one half on the windward side and one half on the leeward side. It is constructed by penetrating a plurality of heat exchanger tubes in a staggered manner as a whole.

The refrigerant from the compressor flows into the leeward heat transfer tube from the inlet pipe, and after exchanging heat with the air passing through the fins,
Flows into the windward heat transfer tube. The refrigerant flowing into the windward heat transfer tube further exchanges heat with the air passing through the fins, flows out from the outlet tube, and returns to the compressor via the pressure reducer and evaporator.

The temperature of the refrigerant decreases considerably while passing through the heat transfer tubes.

Therefore, the temperature difference between the windward side heat exchanger tube and the leeward side heat exchanger tube, especially the temperature difference between the heat exchanger tube near the outlet tube and the heat exchanger tube near the inlet tube, is at least about 10℃, depending on the operating conditions. often exceeds 60°C. Moreover, since the commercial heat tubes share a set of fins, a phenomenon occurs in which heat from the leeward side is transmitted through the fins and unnecessarily moves to the windward side, resulting in a significant decrease in thermal efficiency as a condenser.

In order to block heat conduction from the leeward side to the windward side, the windward half and the leeward half of the fin may be thermally separated by a plurality of slits of appropriate length or shape (e.g. (See Japanese Patent Application Laid-open No. 108394/1983).

If the windward and leeward halves of the fin are thermally separated by a plurality of slits, the heat on the windward side is forced to move through the fin connections left between the slits. First, the heat conduction path becomes narrower and longer, increasing thermal resistance and improving the thermal efficiency of the condenser. However, since the fin connections, which are good conductors of heat, exist between the slits, the thermal efficiency of this type of heat exchanger is
It was thought that it would be absolutely impossible to exceed the thermal efficiency of a heat exchanger in which the windward and leeward sides of the fins were completely separated both thermally and physically.

[Problem to be solved by the invention]

An object of the present invention is to optimize the formation conditions of a plurality of slits provided between the windward half and the leeward half of the fin in a cross-fin tube heat exchanger. The aim is to obtain better thermal efficiency that exceeds that of a heat exchanger in which both sides are completely separated both thermally and physically.

[Means to solve the problem]

In the heat exchanger of the present invention, when providing a plurality of slits between the windward half and the leeward half of the fins, the fin connection portions left between the slits are adjusted to match the step pitch of the windward heat exchanger tubes. Try to position it near the middle part. In this case, the length of the fin connection part should be in the range of 2% to 30% of the step pitch of the windward heat exchanger tube, preferably 10% of the same pitch.
It is desirable to do it before and after.

It is desirable that the fin connection parts be provided at each step pitch of the windward heat exchanger tubes, but if necessary, it is also possible to provide them at every other or every plural number of the same pitches. It is desirable that the heat exchanger tubes on the leeward side have the same stage pitch as the heat exchanger tubes on the windward side, and are located behind the fin connection portions with respect to the one-pass air.

[Effect]

In the present invention, rather than completely thermally separating the windward and leeward sides of the fins, it is better to actively create a certain thermal correlation between the windward and leeward sides of the fins, thereby increasing the thermal efficiency of the condenser. This is based on new knowledge that shows that it can be further improved.

FIG. 1 is a drawing for explaining the basic concept of the present invention. In the figure, reference numeral 11 denotes a fin made of a metal such as aluminum or copper that has good thermal conductivity. Although only one fin is shown in the drawing for convenience, in reality, a large number of fins are arranged side by side at predetermined intervals. 1.2a and 12b are a plurality of heat exchanger tubes provided to penetrate through the windward half (a on the left in the drawing) and the leeward half (on the right in the drawing) of the fin 11, respectively. Arrow A indicates the direction of air passage to the heat exchanger. Heat exchanger tubes], 2a and 12b are generally arranged in a staggered manner. The refrigerant from the compressor flows in from the upper right, passes sequentially through the heat transfer tubes 12b on the leeward side, flows into the heat transfer tubes 1.2a on the windward side at the bottom of the heat exchanger, sequentially passes through the heat transfer tubes 1. flows out from

Reference numeral 15 denotes a plurality of slits for thermally separating the windward half and the leeward half of the fin 11, which are shown here as elongated strip-shaped openings formed by punching or the like. These slits 15 are arranged in the vertical direction (direction perpendicular to the air passage direction A), leaving a connecting portion 1G of a certain length that is a part of the fin.

For convenience of explanation, the length of the slit 15 is L, and the length of the fin connection part 16 is S1.
2a and the leeward heat transfer tube 12b) is Pl, the step pitch of the windward heat transfer tubes 12a (the distance between the windward heat transfer tubes 12a) is P2, and the fin connection portion with respect to the position of the windward heat transfer tube 12a. The displacement amount of 16 is expressed as H. In addition,
For simplicity, it is assumed that the stage pitch of the leeward heat exchanger tubes 12b is P2, which is the same as the stage pitch of the windward side heat exchanger tubes 12a,
The leeward heat exchanger tube 12b is.

It is assumed that the heat exchanger tubes are arranged so as to be displaced from the windward side heat exchanger tubes 12a by exactly half of the one-stage pitch P2.

The inventors have proposed that the fin connection portion 16 for the step pitch P2 be
relative position (H/P2) and relative length of the connection part (S/P2)
Based on the prediction that 2) is closely related to the heat exchange characteristics of the condenser, we decided to find its optimum value through calculations and actual measurements. The results are shown in FIGS. 2 and 3. Here, the vertical axis indicates the heat exchange capacity ratio, with the case where no slit 15 is provided in the fin j1 being 1.

The calculations and experiments were performed using commercially available standard heat exchanger tubes and fins, with the inlet air temperature at 0°C, the temperature of the windward heat exchanger tube 1.2a at 60°C, and the temperature of the leeward heat exchanger tube 12b at 100°C. Heat tube row pitch P is 12.5+1m, stage pitch P2 is 2
The width of the slit 15 was set to 1.5 mm, and the velocity of the incoming air was set to 0.5 m/see.

The characteristic curve in FIG. 2 shows the relative length (S/
P, ) is fixed at 0.2, and the relative position of the connection part (H/P
2) shows the change in capacity ratio when changing. As is clear from the figure, the heat exchange capacity as a condenser is
In the case of H/P2=0.5, in other words, the fin connection part 1
6 is maximum when it is near the middle part of the stage pitch of the windward side heat exchanger tubes 12b.

Next, based on the measurement results shown in Fig. 2, the relative position (H/P'2) of the fin connection part 16 is fixed at the optimum value of 0.5, and the relative length (S/P2) of the connection part is changed. I let it happen. The result is the characteristic curve shown in FIG. As is clear from the figure, the heat exchange capacity of the condenser is.

It is maximum when S/P2=0.1 (when the length S of the fin connection portion 16 is 1/10 of the step pitch P2). Furthermore, the value is actually larger than that in the case where S/P2=O (in the case where the fins 11 are completely divided by continuous slits).

According to conventional wisdom in the industry, if even a small portion of the fin connection, which is a good conductor of heat, remains, it will not be possible to completely prevent heat conduction from the leeward side to the windward side, and the condenser will not function as a condenser. Thermal efficiency will inevitably deteriorate accordingly (there is no way it will be better than if the fins were completely separated by continuous slits).

In fact, in Fig. 3, the length S of the fin connection part is equal to the step pitch P2.
(S/P, > 0.3), the capacity ratio as a condenser is greater than when the fins are completely separated by continuous slits (S/p2=o). It is clearly declining.

Then, why in the case of S/P = 0.1 (to be exact, S
Does such an unexpected heat exchange capacity maximization phenomenon occur only when /P2<0.3? The present inventors understand as follows.

If the fins are completely separated by continuous slits,
Although it is possible to effectively prevent the heat from the leeward side from moving to the windward side, on the other hand, the temperature in the windward half of the fins, especially the temperature near the middle part of the step pitch of the windward heat transfer tubes, decreases abnormally. As a result, the thermal efficiency of that part deteriorates. Therefore, if the minimum necessary amount of heat on the leeward side, which is high temperature, is diverted to the windward side and the temperature of that portion is maintained high, the thermal efficiency of the condenser can be further improved. This is why the capacity ratio is maximized when the fin connection portion is located near the middle of the stage pitch of the windward heat exchanger tubes.

However, if the amount of heat to be diverted is larger than necessary, an undesirable temperature drop will occur on the leeward side, and the thermal efficiency of the condenser will deteriorate. However, by selecting the length S of the fin connection part in the range of 2% to 3o% of the step pitch (preferably around 10% of the step pitch), the amount of heat diverted to the windward side can be optimized, resulting in condensation. The thermal efficiency of the container can be further increased. Here, the length S of the fin connection part is set in the range of 2% to 30% of the step pitch, because if it is less than 2%, the windward half and the leeward half of the fin 11 will be thermally isolated. This is because they are effectively separated mechanically.
This is because if it exceeds 30%, the amount of heat diverted to the windward side will be too large, which will actually cause a decrease in thermal efficiency.

Table 1 summarizes the results of experimentally fabricating several fin-shaped heat exchangers and actually measuring the temperature of outflow air and the heat exchange capacity ratio. The setting conditions are that the velocity of the incoming air is 0.4 m.
/see is the same as in FIGS. 2 and 3. In addition, please refer to FIG. 4 for details of the setting position of the fin connection part.

If you look at the wooden surface, you will see 1 Prototype 5 (H
/P2=0.5, S/P2=0.1) is superior to the separated fin type prototype 2 (S/P2=O) in both the outlet air temperature and heat exchange capacity ratio. should be obvious.

In addition, making the step pitch of the leeward side heat transfer tubes the same as the step pitch of the windward side heat transfer tubes, and positioning the leeward side heat transfer tubes behind the fin connection part with respect to the passing air, will reduce the temperature of the windward side fins. Although this is a desirable condition for optimizing, it is not necessarily an essential condition. If the condition of locating the fin connection part near the middle of the step pitch of the windward heat transfer tube is satisfied, even if the above condition is not satisfied, the heat from the leeward side can be transferred to the relevant part of the windward side fin. This is because it is possible to separate the flow.

It is also not always an essential condition to arrange the fin connection portions at every stage pitch of the windward heat exchanger tubes. Depending on the conditions of use of the heat exchanger, it is fully possible to obtain the desired effect by arranging the fin connection portions at every other step pitch or every plural step pitches of the windward heat exchanger tubes.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

FIG. 5 shows a refrigeration cycle when a heat pump type air conditioner is used as a heater. In the same figure, 1
2 is a compressor, 2 is a four-way valve, 3 is an indoor heat exchanger, 4 is a pressure reducer, 5 is an outdoor heat exchanger, 6 is an outdoor fan, and 7 is an indoor fan.

The refrigerant compressed by the compressor 1 flows into the indoor heat exchanger 3 through the four-way valve 2, as shown by the solid arrow.

The heat exchanger acts as a condenser and releases heat to warm the air in the room. The refrigerant that has passed through the indoor heat exchanger 3 is reduced in pressure by a pressure reducer 4 and reaches the outdoor heat exchanger 5 . The air exchanger acts as an evaporator and absorbs heat from the outdoor air. The refrigerant that has passed through the outdoor heat exchanger 5 returns to the compressor 1 through the four-way valve 2 and is compressed again by the compressor.

The indoor heat exchanger 3 has a structure shown in FIGS. 6(a) to 6(c). In the figure, arrow A indicates the direction in which air passes through the heat exchanger 3. 11 is.

A large number of fins 12a and 12b arranged side by side at predetermined intervals are a plurality of heat transfer tubes that are passed through the windward half and the leeward half of the fins 11 at predetermined intervals.

The windward heat exchanger tubes 12a and the leeward heat exchanger tubes 12b are generally arranged in a staggered manner as shown in FIG. 6(a). The ends of the heat exchanger tubes are connected in turn to the ends of other heat exchanger tubes adjacent to each other in the vertical direction, and the ends of the lowermost windward heat exchanger tubes are connected to the ends of the lowermost leeward heat exchanger tubes. are connected to form one continuous refrigerant passage as a whole. The refrigerant from the compressor flows into the upper right inlet pipe 13 and passes through the heat transfer pipe 12 on the leeward side.
After passing through the heat exchanger tube 12a on the windward side, it flows out from the outlet tube 14 on the upper left.

A plurality of slits 15 are formed in the central longitudinal direction of the fin 11 (in a direction perpendicular to the air passage direction A), leaving a fin connection part 16 of a predetermined length. Although the slit 15 is described here as an opening having a certain width and length, it may have any other shape as long as it has the function of preventing heat conduction between the windward side and the leeward side. slits can be used. Therefore, for example, the slits may be formed by making linear cuts in the fin material at predetermined intervals and bending them in opposite directions. However, by providing a predetermined gap between the cut edges of the fin materials that are offset from each other, or by making the cut edges at least in line contact with each other, heat conduction between the windward side and the leeward side will occur. Care must be taken to ensure that this does not occur.

The fin connection portion 16 is located near the middle of the step pitch of the windward heat exchanger tubes 12b. For the reasons mentioned above, it is desirable that the length of the fin connection portion 16 be in the range of 2% to 30% of the single step pitch, preferably around 10% of the step pitch. In the case of this embodiment, the stage pitch of the leeward heat exchanger tubes] and 2b is selected to be the same as the stage pitch of the windward side heat exchanger tubes 12a, and each leeward side heat exchanger tube 12b is The fin connecting portion 16 is located behind the fin connecting portion 16. If such an arrangement is adopted, temperature control of the windward half of the fin can be easily optimized.

〔Effect of the invention〕

By employing the present invention, the thermal efficiency of a cross-fin tube heat exchanger as a condenser can be further improved beyond conventional wisdom. Moreover, the fin connection part 1
The fact that the length of 6 can be set in the range of 2% to 30% of the stage pitch means that a heat exchanger with sufficient mechanical strength can be manufactured at low cost, and in this respect also has high practical value. .

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a cross-fin tube heat exchanger for explaining the basic concept of the present invention, and Figures 2 and 3 are experiments to determine the optimal values of the relative positions and relative lengths of the fin connections. A curve diagram showing the results, Fig. 4 is a diagram showing the arrangement of fin connections of various prototypes, Fig. 5 is a system diagram showing the refrigeration cycle during heating of a heat pump type air conditioner, and Fig. 6 is a diagram according to the present invention. It is a drawing showing one example of a heat exchanger. 6(a) is a perspective view of the heat exchanger, FIG. 6(b) is a sectional view taken along line II in FIG. 6(a), and FIG. 6(c) is a sectional view taken along line n-- It is an n cross-sectional view. Explanation of symbols> 11... Fin of heat exchanger, 12a... Windward side heat exchanger tube of heat exchanger, 12b... Leeward side heat exchanger tube of heat exchanger,
15...Slit, 16...Fin connection part

Claims (1)

[Claims] 1. A large number of fins are arranged side by side, and a plurality of heat transfer tubes are passed through the windward half and the leeward half in a staggered manner as a whole, and the windward half and the leeward half of the fins In a cross-fin tube heat exchanger in which the leeward half is thermally separated from the leeward half by multiple slits, the fin connections left between the slits are located at the middle of the stage pitch of the windward heat exchanger tubes. A heat exchanger for an air conditioner, characterized in that the heat exchanger is located near the air conditioner. 2. The heat exchanger tubes on the leeward side have the same stage pitch as the heat exchanger tubes on the windward side, and are respectively positioned behind the fin connection portions with respect to the passing air. A heat exchanger for an air conditioner according to Scope 1. 3. The air conditioner according to claim 1, wherein the length of the fin connection portion is selected within a range of 2% to 30% of the step pitch of the windward heat exchanger tubes. Heat exchanger. 4. The heat exchanger for an air conditioner according to claim 3, wherein the length of the fin connection portion is selected to be approximately 10% of the stage pitch of the windward side heat transfer tubes. 5. The heat exchanger for an air conditioner according to claim 1, wherein the fin connection portions are provided for each step pitch of the windward heat transfer tubes. 6. The heat exchanger for an air conditioner according to claim 1, wherein the fin connection portions are provided at every other step pitch or every plural number of step pitches of the windward side heat transfer tubes. vessel. 7. In a heat pump type air conditioner that uses an indoor heat exchanger as a condenser and an outdoor heat exchanger as an evaporator, at least the indoor heat exchanger has the following features: An air conditioner characterized by being a heat exchanger according to any one of Item 6.