Refrigeration – Reversible – i.e. – heat pump – With refrigerant collection and intermittent discharge
Reexamination Certificate
2003-03-17
2004-12-07
Doerrler, William C. (Department: 3744)
Refrigeration
Reversible, i.e., heat pump
With refrigerant collection and intermittent discharge
C062S324100, C062S160000
Reexamination Certificate
active
06826924
ABSTRACT:
TECHNICAL FIELD OF INVENTION
The present invention relates to a heat pump apparatus which performs a refrigeration cycle.
BACKGROUND OF INVENTION
Airconditioners of the so-called multi type have been known in the prior art. Japanese Patent Kokai Gazette No. (1998)300292 discloses one such airconditioner that includes a single outdoor unit and a plurality of indoor units connected to the outdoor unit. In this airconditioner, the outdoor unit contains an outdoor circuit and each indoor unit contains an indoor circuit. The outdoor circuit of the outdoor unit includes a compressor, an outdoor heat exchanger, an outdoor expansion valve, a receiver, et cetera. On the other hand, the indoor circuit of each indoor unit includes an indoor heat exchanger and an indoor expansion valve. The indoor units are each connected in parallel to the outdoor unit to form a refrigerant circuit of the airconditioner.
The above-described airconditioner performs a refrigeration cycle by circulation of a refrigerant through the refrigerant circuit. Additionally, the airconditioner operates switchably between a cooling mode of operation and a heating mode of operation by reversing the circulation direction of refrigerant in the refrigerant circuit.
During the cooling mode of operation, a cooling operation, in which each indoor heat exchanger acts as an evaporator, is carried out. During the cooling mode of operation, a refrigerant discharged from the compressor is caused to condense by the outdoor heat exchanger. After passing through the receiver, the refrigerant is distributed to each indoor circuit. Thereafter, the refrigerant is depressurized by the indoor expansion valve, is caused to evaporate by the indoor heat exchanger, is brought back to the outdoor circuit, and is drawn into the compressor.
During the heating mode of operation, a heating operation (i.e., a heat pump operation), in which each indoor heat exchanger acts as a condenser, is carried out. During the heating mode of operation, a refrigerant discharged from the compressor is distributed to each indoor circuit and is caused to condense by the indoor heat exchanger. The refrigerant condensed is depressurized by the indoor expansion valve. Thereafter, the refrigerant is delivered to the outdoor circuit. And, after passing through the receiver, the refrigerant is further depressurized by the outdoor expansion valve. Thereafter, the refrigerant is caused to evaporate by the outdoor heat exchanger and is drawn into the compressor.
Installation of a multi type airconditioner in a building may result in a difference in installation height between indoor units. For example, when an outdoor unit is installed on the roof and indoor units are installed on the first floor and on the second floor, respectively, there is a difference in installation height between the indoor units. In this case, the refrigerant, while changing in phase, circulates between an outdoor circuit contained in the outdoor unit installed on the roof and each of indoor circuits contained in the indoor units installed on the first and second floors.
However, if the difference in installation height between the indoor units becomes greater, this causes the problem that the refrigerant flows only through the upper-situated indoor unit, in other words no refrigerant flows in the lower-situated indoor unit during the heating mode of operation of the airconditioner. As a result, the lower-situated indoor unit fails to provide sufficient heating. Consequently, conventional airconditioners are subject to many restrictions on the difference in installation height between indoor units and the degree of layout freedom at the time of installation in a building is little.
Referring to
FIG. 4
, such a drawback will be illustrated by an example case in which a first indoor unit (
12
) is installed lower than an outdoor unit (
11
) and a second indoor unit (
13
) is disposed lower than the first indoor unit (
12
). Here, the description will be made on the condition that there is an installation height difference of H
1
between the second indoor unit (
13
) and the first indoor unit (
12
) and there is an installation height difference of H
2
between the first indoor unit (
12
) and the outdoor unit (
11
) is (see FIG.
2
).
FIG. 4
is a Mollier diagram (i.e., a pressure-enthalpy diagram) showing a typical refrigeration cycle performed in the refrigerant circuit of the airconditioner. During the heating mode of operation, a refrigerant condensed by an indoor heat exchanger of the first indoor unit (
12
) is depressurized by an indoor expansion valve of the first indoor unit (
12
) and, as a result, the pressure decreases by &Dgr;P
i1
. On the other hand, a refrigerant condensed by an indoor heat exchanger of the second indoor unit (
13
) is depressurized by an indoor expansion valve of the second indoor unit (
13
) and, as a result, the refrigerant pressure decreases by &Dgr;P
i2
. The refrigerant condensed in the second indoor unit (
13
) flows toward the outdoor unit (
11
) and the refrigerant pressure will have decreased by a liquid head difference &Dgr;
h1
corresponding to the installation height difference H
1
between the first indoor unit (
12
) and the second indoor unit (
13
) at the moment that the refrigerant reaches the height of the first indoor unit (
12
). Thereafter, the refrigerant from the first indoor unit and the refrigerant from the second indoor unit flow into each other and the refrigerant pressure decreases by a liquid head difference &Dgr;
h2
corresponding to the installation height difference H
2
between the first indoor unit (
12
) and the outdoor unit (
11
). And, the refrigerant flows into the receiver. The refrigerant, which has exited the receiver, is depressurized by the outdoor expansion valve and the refrigerant pressure decreases by &Dgr;P
0
. Then the refrigerant is caused to evaporate by the outdoor heat exchanger and is drawn into the compressor.
If the installation height difference H
1
between the indoor units (
12
,
13
) is increased, then the liquid head difference &Dgr;
h1
corresponding to the installation height difference H
1
also increases. In this case, the valve travel of the indoor expansion valve (which has already been in a certain open state) of the second indoor unit (
13
) is increased to a further extent so as to reduce the differential pressure &Dgr;P
i2
between the inlet pressure and the outlet pressure of the indoor expansion valve, whereby the flow rate of refrigerant to the second indoor unit (
13
) is assured. However, even when the indoor expansion valve of the second indoor unit (
13
) is fully opened, it is impossible to reduce the differential pressure &Dgr;P
i2
to zero. Accordingly, if the installation height difference H
1
between the indoor units (
12
,
13
) becomes excessive, this makes it impossible to assure the flow rate of refrigerant to the second indoor unit (
13
) by adjustment of the valve travel of the indoor expansion valve of the second indoor unit (
13
). As a result, the flow rate of refrigerant to the second indoor unit (
13
) decreases. Therefore, severe restrictions have been imposed on the indoor unit installation height difference H
1
in order to prevent occurrence of such a situation.
In consideration of the above-described inconvenience, the present invention was made. Accordingly, an object of the present invention is to relax restrictions on the installation of a heat pump apparatus including a plurality of utilization side circuits, thereby improving the freedom of installation thereof.
SUMMARY OF INVENTION
The present invention discloses a heat pump apparatus comprising a refrigerant circuit (
15
) in which a plurality of utilization side circuits (
60
,
65
) having respective utilization side heat exchangers (
61
,
66
) and utilization side expansion mechanisms (
62
,
67
) are each connected in parallel to a heat source side circuit (
20
) having a compressor (
41
,
42
), a heat source side expansion mechanism (
24
), and a receiver (
23
), and the heat pump apparatus performs a
Matsuoka Hiromune
Shimoda Junichi
Daikin Industries Ltd.
Doerrler William C.
Nixon & Peabody LLP
Studebaker Donald R.
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