Indoor Unit of Air Conditioner and Air Conditioner Including the Same

Abstract

An indoor unit of an air conditioner of the present invention includes a cabinet; an air inlet through which air is sucked into the cabinet; a centrifugal fan which blows the air sucked in to the surrounding portions; and an a heat exchanger which is provided in the direction of air supply of the centrifugal fan and allows heat exchange between the air and a refrigerant flowing thereinside, in which the following equation is satisfied: 0.16≦L/D≦0.19, where D is an outer diameter of the centrifugal fan and L is a distance between the centrifugal fan and the heat exchanger in their closest positions. Thus, a variation in a velocity distribution created in the heat exchanger can be suppressed, and the indoor unit of the air conditioner which achieves an improved energy saving property due to a reduced pressure loss and an improved heat exchange efficiency of the heat exchanger can be provided.

Description

CLAIM OF PRIORITY

The present application claims priority from Japanese Patent application serial No. 2015-037610, filed on Feb. 27, 2015, the content of which is hereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an indoor unit of an air conditioner and an air conditioner including the same.

2. Description of Related Art

Japanese Unexamined Patent Application Publication No. 2011-12937 (Patent Document 1) discloses that an indoor unit of an air conditioner includes a guide member which leads the air fed from a fan of a heat exchanger to a lower part of the heat exchanger on a side opposing the fan.

A heat exchanger arranged in an indoor unit is enlarged in size for the purpose of improving heat exchange efficiencies and reducing pressure losses. A height of the heat exchanger is greater than a height of a discharge port of a centrifugal fan. In addition, if the centrifugal fan is to be arranged in a limited space of the indoor unit, the centrifugal fan is inevitably arranged in an upper part of the heat exchanger. Such an arrangement creates a variation in a velocity distribution inside the heat exchanger.

Accordingly, a guide member which leads the air fed from the fan to a lower part of the heat exchanger is provided on the side opposing the fan, as in the constitution described in Patent Document 1, whereby the variation in the velocity distribution created in the heat exchanger can be suppressed.

The means for attaching the guide member around the centrifugal fan can suppress the variation in the velocity distribution created in the heat exchanger, but it does not suppress the generation of the variation itself, and has been insufficient to achieve further improvement in the efficiency and energy saving.

To this end, an objective of the present invention is to suppress the variation in the velocity distribution created in the heat exchanger, and to provide the indoor unit of the air conditioner which achieves an improved energy saving property.

SUMMARY OF THE INVENTION

In order to achieve the above object, an indoor unit of an air conditioner of the present invention includes a cabinet; an air inlet through which air is sucked into the cabinet; a centrifugal fan which blows the air sucked in to the surrounding portions; and an a heat exchanger which is provided in the direction of air supply of the centrifugal fan and allows heat exchange between the air and a refrigerant flowing thereinside, in which the following equation is satisfied:

0.16≦L/D≦0.19,

where D is an outer diameter of the centrifugal fan and L is a distance between the centrifugal fan and the heat exchanger in their closest positions.

According to the present invention, a variation in a velocity distribution created in the heat exchanger can be suppressed, and the indoor unit of the air conditioner which achieves an improved energy saving property due to a reduced pressure loss and an improved heat exchange efficiency of the heat exchanger can be provided. Other objects, constitutions, actions and effects of the present invention will be described below in the following Examples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an indoor unit of an air conditioner according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view which is perpendicular to an axis of rotation of a centrifugal fan of the indoor unit of the air conditioner according to an embodiment of the present invention;

FIG. 3 is a cross section of the indoor unit of the air conditioner shown in FIG. 2 taken along line A-A;

FIG. 4 is a graph in which a horizontal axis represents L/D, and a vertical axis represents a standard deviation of a velocity distribution occurring within a heat exchanger;

FIG. 5 is a graph in which a horizontal axis represents b2/H, and a vertical axis represents the standard deviation of the velocity distribution occurring within the heat exchanger;

FIG. 6 is a drawing which shows a region between a centrifugal fan and a heat exchanger;

FIG. 7 is a cross-sectional view in which the filter, the bell mouth and the centrifugal fan are enlarged in FIG. 3; and

FIG. 8 is a cross-sectional view of known filter, bell mouth and centrifugal fan.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Examples of the present invention will be described below with reference to the drawings.

First Embodiment

FIG. 1 shows a perspective view of an indoor unit of an air conditioner according to an embodiment of the present invention. The indoor unit of FIG. 1 is connected with an outdoor unit (not shown) via a refrigerant pipe, and is a component of the air conditioner. A compressor is arranged in the outdoor unit. A refrigerant is compressed by this compressor, and a refrigerating cycle is formed by circulating the refrigerant through the inside of the refrigerant pipe. The indoor unit includes a cabinet 1 disposed inside a ceiling and a panel 2 attached to on an indoor side of the cabinet 1. The panel 2 is provided with a grill 3 for drawing indoor air in, and four air outlets 4 for blowing the air sucked in from the grill 3 indoors. Air outlets 5 are each provided with a louver 4 attached thereto in a manner of being rotationally driven by a motor for the louver (not shown), which adjusts a direction of the air blown out. In other words, the panel 2 has an air inlet through which the air is sucked into the cabinet 1.

FIG. 2 is a drawing which shows a cross-sectional view of the indoor unit of FIG. 1 seen toward a direction of an axis of rotation Z of the fan (FIG. 3). As shown in FIG. 2, the indoor unit of this Example has a centrifugal fan 10 having backward curved blades which are disposed in a central portion of the indoor unit and discharges air in a direction away from the axis of the rotation Z, and a heat exchanger 11 which is disposed in the direction of air supply of the centrifugal fan 10 in a manner of surrounding the centrifugal fan 10 and performs heat exchange between the air from centrifugal fan 10 and the refrigerant which flows through thereinside.

The configuration of the heat exchanger 11 is a polygon such that it has a curvature at a corner when seen in a cross section perpendicular to the axis of rotation Z of the centrifugal fan 10, and has a substantially rectangular shape with a part of the corners being open. In FIG. 2, the heat exchanger 11 has such a shape that the centrifugal fan 10 is surrounded by three corner portions and four straight sides. One of the corners has a straight line shape shorter than other straight parts, and has such a shape that the distance between itself and the outer circumference of the centrifugal fan 10 is shorter than from other corners. Although not illustrated, in the space provided between this corner and the cabinet 1, a drain pump for discharging a dew condensation water (a drain water) generated by the heat exchanger 11 during an air conditioning operation is disposed.

FIG. 3 is a drawing which shows a cross section taken along line A-A in FIG. 2. By rotating the centrifugal fan 10 about the axis of rotation Z by motor 20 connected to centrifugal fan 10, air is sucked in through a filter 6 attached to the grill 3. The air sucked in passes through a bell mouth 12 whose opening portion gradually contracts towards the centrifugal fan 10, and is blown out to a radial direction (the direction of the circumference) of the centrifugal fan 10 by the centrifugal fan 10. The air blown out passes through the heat exchanger 11, flows out from the heat exchanger 11, and is then discharged into the room from the air outlet 5 so that an air current 50 shown in FIG. 3 is formed. When the air shown by the airflow 50 is blown out from the air outlet 5 into the room, the wind direction is adjusted by the louver 4 attached to the panel 2.

Heat exchange is performed between air and the refrigerant flowing through the inside of the heat exchanger 11 in the heat exchanger 11 during a heating operation or cooling operation, whereby heating or cooling of indoor air is performed. An electrical component box 7 accommodating a control board (not shown) for controlling the behavior of the indoor unit is attached to a lower part of the bell mouth 12 that is a space between the filter 6 and bell mouth 12.

Next, a dimensional relationship between the centrifugal fan 10 and heat exchanger 11 in this Example will be described.

The outer diameter of the centrifugal fan 10 is D, and the distance that the centrifugal fan 10 and the heat exchanger 11 is the closest is defined as L in a cross section perpendicular to the axis of rotation Z of the centrifugal fan 10 (see FIG. 2). The ratio L/D is the lowest when the distance between the centrifugal fan 10 and the heat exchanger 11 in their closest positions is L. It should be noted that the heat exchanger 11 has four straight line portions, but the distances L between each of the straight line portions and the centrifugal fan 10 are approximately the same.

Conventionally, a centrifugal fan has been designed to have a reduced shaft power at the same flow rate by increasing the diameter of the centrifugal fan 10 as much as possible. The present invention, however, does not simply aim at providing a larger diameter, but focuses on the relationship L/D between the outer diameter D of the centrifugal fan 10 and the distance L between the centrifugal fan 10 and the heat exchanger 11 for the purpose of reducing the pressure loss and improving the performance of the heat exchange cycle of the heat exchanger 11 by reducing a variation in the flow rate of the air passing through the inside of the heat exchanger 11.

FIG. 4 is a graph in which a horizontal axis represents L/D, and a vertical axis represents a standard deviation indicating the variation in the flow rate of the air passing through the inside of the heat exchanger 11. A height b2 of a discharge port of the centrifugal fan 10 illustrated in FIG. 3 is changed, and the changes in the standard deviation relative to L/D at different values of b2 are shown by a solid line and a broken line. The lowered standard deviation shows that the variation in the flow rate of the air passing through the inside of the heat exchanger 11 is reduced and the velocity distribution becomes nearly uniform. When the velocity distribution becomes nearly uniform, the pressure loss of the heat exchanger 11 is reduced, and the effects in improving the heat exchange efficiency can be obtained. In a conventional device, for example, L=54 mm, D=490 mm, and L/D=0.11, but this graph revealed that the region of L/D in which the standard deviation becomes low is when 0.16≦L/D≦0.19.

Specifically, when the centrifugal fan 10 and the heat exchanger 11 are too close (L/D is low), the wind velocity of the closest part between the centrifugal fan 10 and the heat exchanger 11 becomes locally high, and therefore a variation in the velocity distribution occurs. On the other hand, when the centrifugal fan 10 and the heat exchanger 11 are too far apart (L/D is high), the outer diameter D of the centrifugal fan 10 becomes too small relative to the heat exchanger 11, and therefore the number of revolutions of the centrifugal fan 10 needs to be increased in order to deliver the same volume of air into the heat exchanger 11. Since the increased number of revolutions increases the circumferential speed, the air blowing angle from the centrifugal fan 10 becomes nearly parallel to the inflow face of the heat exchanger 11, which adversely affects the velocity distribution. Considering this, based on FIG. 4, in this Example, the centrifugal fan 10 and the heat exchanger 11 are so configured to attain 0.16≦L/D≦0.19. It is further desirable that 0.17≦L/D≦0.18. This can greatly improve the velocity distribution and heat exchange efficiency.

Moreover, in order to change L/D (for example, in order to increase L/D), there are the following options: reducing the outer diameter of the centrifugal fan 10; and enlarging the heat exchanger 11. If the heat exchanger 11 is enlarged, the air outlet 5 between the cabinet 1 and the heat exchanger 11 is narrowed, which increases the pressure loss and lowers the air blowing efficiency. Meanwhile, there is an option to maintain the opening area of the air outlet 5 by also enlarging the cabinet 1 with the enlargement of the heat exchanger 11. However, it is desirable that the installation space of the indoor unit (especially in-ceiling type) is not changed in terms of construction, and that a conventional size of the cabinet: approximately 840 mm is not changed. Therefore, it is preferable that the requirement that 0.16≦L/D≦0.19 is satisfied and further the external dimension W of the cabinet 1 is designed to satisfy 830 mm≦W≦850 mm. Moreover, it is preferable that the outer diameter D of the fan is 440 mm≦D≦470 mm in order not to affect the dimensions of the heat exchanger 11 and the air outlet 5.

Second Embodiment

FIG. 3 shows the definitions of the height b2 of the discharge port of the centrifugal fan 10 and the height H of the heat exchanger 11. In this case, the ratio of the height b2 of the discharge port of the centrifugal fan 10 to the height H of the heat exchanger 11 is b2/H. By setting b2/H to an appropriate value, the efficiency of the centrifugal fan 10 can be further increased by applying the above first embodiment.

First, the case where the height H of the heat exchanger 11 is constant, and the height b2 of the discharge port of the centrifugal fan 10 is changed will be described.

As the height b2 of the discharge port of the centrifugal fan 10 is reduced and b2/H is lowered, the width of the passage composed of a hub face 101 and a shroud face 102 of the centrifugal fan 10 is reduced, and an increased friction loss within the centrifugal fan 10 lowers the efficiency of the centrifugal fan 10.

On the other hand, as the height b2 of the discharge port of the centrifugal fan 10 is increased and b2/H is increased, the width of the passage composed of the hub face 101 and the shroud face 102 is increased, and the friction loss is lowered. The centrifugal fan 10 is characterized in that it draws air from the bottom in FIG. 3 in the direction of the axis of rotation Z, and blows air at an angle which is perpendicular to the axis of rotation Z or the almost the same angle. Accordingly, it is desirable that the air sucked in by the centrifugal fan 10 flows along the shroud face 102. However, when the width of the passage composed of the hub face 101 and the shroud face 102 increases, the air sucked in by the centrifugal fan 10 peels off from the shroud face 102, resulting in a lowered efficiency of the centrifugal fan 10.

Next, the case where the height b2 of the discharge port of the centrifugal fan 10 is constant, and the height H of the heat exchanger 11 is changed will be described. When the height H of the heat exchanger 11 is decreased and b2/H is increased, a heat transfer area of the heat exchanger 11 is decreased, resulting in the lowered heat exchange efficiency.

On the other hand, when the height H of the heat exchanger 11 is increased, and b2/H is decreased, the heat transfer area of the heat exchanger 11 is increased, which improves the heat exchange efficiency, but the height H of the heat exchanger 11 becomes excessively large, and an air blow from the centrifugal fan 10 becomes ununiform. As a result, a variation is created in the velocity distribution of the air passing through the inside of the heat exchanger 11, resulting in a lowered heat exchange efficiency.

FIG. 5 is a graph in which a horizontal axis represents b2/H and a vertical axis represents the standard deviation indicating the variation in the flow rate of the air passing through the inside of the heat exchanger 11. As in FIG. 4, it means that when the standard deviation is lowered, the variation in the flow rate of the air passing through the inside of the heat exchanger 11 is reduced, and the velocity distribution becomes nearly uniform. This graph reveals that the region of b2/H in which the standard deviation becomes low is when 0.3≦b2/H≦0.5.

Thus, too high or low a value of b2/H results in a lowered efficiency of the centrifugal fan 10 and a lowered heat exchange efficiency of the heat exchanger 11. It is therefore desirable that 0.3≦b2/H≦0.5. It is even more desirable that 0.35≦b2/H≦0.45.

Third Embodiment

FIG. 6 is a drawing which shows a region between the centrifugal fan and the heat exchanger. In a cross section perpendicular to the axis of the rotation Z of the centrifugal fan 10 of the centrifugal fan 10, an area enclosed by an outer periphery of the centrifugal fan 10, an inflow face of the heat exchanger 11, and a straight lines connecting the peripheral ends of the heat exchanger 11 with the rotational center of the centrifugal fan 10 is referred to as a region X, which is indicated in gray in FIG. 6.

When the outer diameter D of the centrifugal fan 10 and the height H of the heat exchanger 11 are the same, and the radial distance between the centrifugal fan 10 and the heat exchanger 11 becomes longer, that is, when an area A of the region X is increased, the inflow area of the heat exchanger 11 is increased. The increase in the inflow area increases the heat transfer area of the heat exchanger 11, thereby improving the heat exchange efficiency. Moreover, the pressure loss of the heat exchanger 11 changes depending on the flow rate of the air passing through thereinside. Accordingly, the increase in the inflow area decreases the average flow rate of the air passing through the inside of the heat exchanger 11, whereby the pressure loss of the heat exchanger 11 is reduced, and the shaft power of the centrifugal fan 10 is reduced.

According to the above first embodiment, attaining 0.16≦L/D≦0.19 can suppress the variation in the velocity distribution of the air passing through the inside of the heat exchanger 11. This expectedly improves the heat exchange efficiency and reduces the pressure loss of the heat exchanger 11. Furthermore, increasing the area A of the region X, that is, increasing A/W² which corresponds to a ratio of the area calculated from the external dimension W of the cabinet 1 to the area A of the region X expectedly improves the heat exchange efficiency and reduces the pressure loss.

However, as the A/W² is increased when 0.16≦L/D≦0.19, the heat exchanger 11 gradually expands towards the outside. In such a case, the sufficient opening area of the air outlet 5 and width of the air outlet passage 8 can be no longer ensured, and the pressure loss in these is increased, which prevents the air conditioner from performing its main function of conditioning the indoor air. Accordingly, it is desirable that 0.21≦A/W²≦0.27.

Fourth Embodiment

A fourth embodiment which allows obtaining more effects by applying the above first embodiment will be described.

According to the above first embodiment, attaining 0.16≦L/D≦0.19 can suppress the variation in the velocity distribution of the air passing through the inside of the heat exchanger 11. However, when the outer diameter D of the centrifugal fan 10 is changed so that L/D becomes the same, the dimension of the heat exchanger 11 needs to be changed.

Regarding a ratio D/W of the outer diameter D of the centrifugal fan 10 to the external dimension W of the cabinet 1, lowering D/W reduces the dimension of the heat exchanger 11 which is defined by D+2L. At the same time, the circumferential length of the heat exchanger 11 is reduced. And then the heat transfer area is reduced, and the heat exchange efficiency is deteriorated.

On the other hand, increasing D/W increases the dimension of the heat exchanger 11 defined as above, and the heat transfer area is increased. Although this improves the heat exchange efficiency, the passage width of the air outlet passage 8 is decreased. And the area of the air outlet 5 can be no longer sufficiently ensured, which increases the pressure loss of the air outlet 5. Accordingly, it is desirable that 0.52≦D/W≦0.56 to further obtain effects by applying the above first embodiment.

Fifth Embodiment

FIG. 8 is a cross-sectional view of the filter 6, a bell mouth 12a, and the centrifugal fan 10 in the case where this Example is not applied. The bell mouth 12a is so configured to have an opening area which is gradually contracting from an inlet diameter D_b1 to an outlet diameter D_b2 to guide air to the centrifugal fan 10. When the connection of a face 13 on which the filter 6 and the bell mouth 12a are parallel as shown in FIG. 8 and the opening portion of the bell mouth 12a is configured by a single arc, if a height H_b of the bell mouth 12a is not high enough, the inlet diameter D_b1 of the bell mouth 12a becomes small, and the area of the face 13 increased. Since the distance between the filter 6 and the face 13 is shorter than other portions, the flow rate of the air passing through the region of the filter 6 overlapping the face 13 becomes lower than the flow rate of the air passing through the center of the filter 6. Accordingly, as the area of the face 13 increases, as a flow field 51 shown in FIG. 8, the flow rate of the air passing through the filter 6 tends to be greater at the center of the filter 6.

FIG. 7 is a cross-sectional view of the filter 6, a bell mouth 12, and the centrifugal fan 10 in the case where this Example is applied. The bell mouth 12 includes an inclined plane 12b having a constant inclination angle and a face 13. The face 13 is parallel to the filter 6. That is, the opening portion of the bell mouth 12b is formed to be cone-shaped (to be a shape of a hollow truncated cone). This allows the inlet diameter of the bell mouth 12b to be increased from D_b1 to D_b1′ even if the height H_b of the bell mouth 12 cannot be sufficiently ensured. Also, this allows the area of the face 13 to be decreased. As a result, as a flow field 52 shown in FIG. 7, the flow rate of the air passing through the edge portions of the filter 6 can be increased, and the flow rate of the air passing through the filter 6 can be nearly uniform throughout the filter 6, and therefore the pressure loss of the filter 6 can be reduced.

Claims

1. An indoor unit of an air conditioner comprising:

a cabinet;

an air inlet through which air is sucked into the cabinet;

a centrifugal fan which blows the air sucked in to the surrounding portions; and

an a heat exchanger which is provided in the direction of air supply of the centrifugal fan and allows heat exchange between the air and a refrigerant flowing thereinside,

wherein the following equation is satisfied: 0.16≦L/D≦0.19,

where D is an outer diameter of the centrifugal fan and L is a distance between the centrifugal fan and the heat exchanger in their closest positions.

2. The indoor unit of the air conditioner according to claim 1,

wherein the following equation is satisfied: 835 mm≦W≦845 mm,

where W is an external dimension of the cabinet.

3. The indoor unit of the air conditioner according to claim 1,

wherein the outer diameter D of the centrifugal fan satisfies the following equation: 440 mm≦D≦470 mm.

4. The indoor unit of the air conditioner according to claim 2,

wherein the outer diameter D of the centrifugal fan satisfies the following equation: 440 mm≦D≦470 mm.

5. The indoor unit of the air conditioner according to claim 1,

wherein the following equation is satisfied: 0.3≦b2/H≦0.5,

where b2 is a height of a discharge port of the centrifugal fan and H is a height of the heat exchanger.

6. The indoor unit of the air conditioner according to claim 1, wherein the following equation is satisfied:

A/W2≧0.21,

where W is an external dimension of the cabinet, and A is an area of a region enclosed by an outer peripheral line of the centrifugal fan, an inner peripheral line of a face through which air flows into the heat exchanger, and straight lines connecting peripheral ends of the heat exchanger and a rotational center of the centrifugal fan in a cross section perpendicular to an axis of rotation of the centrifugal fan.

7. The indoor unit of the air conditioner according to claim 1,

wherein the following equation is satisfied: 0.52≦D/W≦0.56,

where W is an external dimension of the cabinet.

8. The indoor unit of the air conditioner according to claim 1,

further comprising a bell mouth which guides the air flowing from the air inlet to the centrifugal fan,

wherein the bell mouth has a curved surface portion which curves in such a direction that its opening area expands towards the air inlet, and an inclined plane having a shape which is inclined in such a direction that its opening area further expands from the curved surface portion.

9. An air conditioner comprising:

the indoor unit according to claim 1;

an outdoor unit; and

pipes connecting these.