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.
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.
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.
Examples of the present invention will be described below with reference to the drawings.
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
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
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.
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
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.
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
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.
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.
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.
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.
Number | Date | Country | Kind |
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2015-037610 | Feb 2015 | JP | national |