U.S. patent application number 13/091665 was filed with the patent office on 2011-10-27 for cooling system.
This patent application is currently assigned to GAC Corporation. Invention is credited to Naofumi EZAWA, Junichi Oki.
Application Number | 20110259573 13/091665 |
Document ID | / |
Family ID | 44814794 |
Filed Date | 2011-10-27 |
United States Patent
Application |
20110259573 |
Kind Code |
A1 |
EZAWA; Naofumi ; et
al. |
October 27, 2011 |
COOLING SYSTEM
Abstract
A cooling system comprises a first heat exchanger installed
inside a room; a second heat exchanger installed outside the room;
and a piping system that enables a refrigerant to naturally
circulate between the first heat exchanger and the second heat
exchanger. The piping system includes the first supply pipe and the
second supply pipe. The first supply pipe supplies liquid
refrigerant from the second heat exchanger to the first heat
exchanger and the liquid refrigerant is heated by heat exchanging
in a third heat exchanger with vaporized refrigerant supplied from
the first heat exchanger to the second heat exchanger. The second
supply pipe supplies liquid refrigerant from the second heat
exchanger to the first heat exchanger bypassing the third heat
exchanger.
Inventors: |
EZAWA; Naofumi; (Nagano,
JP) ; Oki; Junichi; (Nagano, JP) |
Assignee: |
GAC Corporation
Azumino-shi
JP
|
Family ID: |
44814794 |
Appl. No.: |
13/091665 |
Filed: |
April 21, 2011 |
Current U.S.
Class: |
165/253 ;
165/50 |
Current CPC
Class: |
F24F 12/002 20130101;
H05K 7/20745 20130101; Y02B 30/56 20130101; H05K 7/20827 20130101;
F24F 2012/005 20130101; Y02B 30/563 20130101; F24F 5/0007
20130101 |
Class at
Publication: |
165/253 ;
165/50 |
International
Class: |
F25B 29/00 20060101
F25B029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 26, 2010 |
JP |
2010-100810 |
Claims
1. A cooling system comprising: a first heat exchanger installed
inside a room; a second heat exchanger installed outside the room;
and a piping system that enables a refrigerant to naturally
circulate between the first heat exchanger and the second heat
exchanger, wherein the piping system includes: a first supply pipe
that supplies liquid refrigerant from the second heat exchanger to
the first heat exchanger, the liquid refrigerant being heated by
heat exchanging in a third heat exchanger with vaporized
refrigerant supplied from the first heat exchanger to the second
heat exchanger; and a second supply pipe that supplies liquid
refrigerant from the second heat exchanger to the first heat
exchanger bypassing the third heat exchanger.
2. The cooling system according to claim 1, wherein the piping
system further includes a changeover valve system that switches
between using the first supply pipe and the second supply pipe, the
cooling system further comprises a control unit that controls the
changeover valve system, and the control unit includes a functional
unit that switches from the second supply pipe to the first supply
pipe using the changeover valve system when a temperature of liquid
refrigerant outputted from the second heat exchanger becomes equal
to or below a first set temperature.
3. The cooling system according to claim 2, wherein the second heat
exchanger includes a second tube and a second fan that supplies
outside air to the second tube, wherein the control unit further
includes a functional unit that stops the second fan before
switching from the second supply pipe to the first supply pipe
using the changeover valve system when the temperature of the
liquid refrigerant outputted from the second heat exchanger becomes
equal to or below the first set temperature.
4. The cooling system according to claim 2, wherein the control
unit includes a functional unit that closes the first supply pipe
and the second supply pipe using the changeover valve system when a
temperature of outside air becomes equal to or below a second set
temperature that is lower than the first set temperature.
5. A hybrid air conditioning system comprising: a cooling system
according to claim 1, and a main air conditioning system that
further cools air that has been cooled by the first heat exchanger
of the cooling system and supplies cooled air.
6. A control method of a cooling system, the cooling system
including a first heat exchanger installed inside a room, a second
heat exchanger installed outside the room, and a piping system that
enables a refrigerant to naturally circulate between the first heat
exchanger and the second heat exchanger, the piping system
including: a first supply pipe that supplies liquid refrigerant,
which has been heated by heat exchanging in a third heat exchanger
with vaporized refrigerant supplied from the first heat exchanger
to the second heat exchanger, from the second heat exchanger to the
first heat exchanger; a second supply pipe that supplies liquid
refrigerant from the second heat exchanger to the first heat
exchanger bypassing the third heat exchanger; and a changeover
valve system that switches between using the first supply pipe and
the second supply pipe, the control method comprising of switching
by a control unit that controls the changeover valve system, from
the second supply pipe to the first supply pipe using the
changeover valve system when temperature of liquid refrigerant
outputted from the second heat exchanger becomes equal to or below
a first set temperature.
7. The control method according to claim 6, wherein the second heat
exchanger includes a second tube and a second fan that supplies
outside air to the second tube, and the control method further
comprises of stopping the second fan before the step of switching
when the temperature of the liquid refrigerant outputted from the
second heat exchanger becomes equal to or below a first set
temperature.
8. The control method according to claim 6, further comprising
closing the first supply pipe and the second supply pipe using the
changeover valve system when temperature of outside air becomes
equal to or below a second set temperature that is lower than the
first set temperature.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2010-100810, filed Apr. 26, 2010, the entire contents of which are
incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to a natural circulation
(vapor-phase circulation)-type cooling system that cools a room by
enabling refrigerant to naturally circulate between a first heat
exchanger installed in a room and a second heat exchanger installed
outside the room.
BACKGROUND
[0003] Japanese Laid-Open Patent Publication No. 2003-347782
discloses a cooling apparatus that is capable of further
suppressing condensation on the surfaces of a heat exchanger
provided in a room. To do so, an ebullient cooling apparatus that
cools the interior of a case according to Publication No.
2003-347782 includes a control device that stops a fan outside the
room and continuously drives a fan inside the room when a
condensation environment has been detected according to signals
from a temperature sensor that detects the temperature of the
surface of the heat exchanger inside the room and a humidity sensor
that is disposed next to the temperature sensor and detects the
humidity. By doing so, when the surfaces of the heat exchanger in
the room have become a condensation environment, the temperature of
such heat exchanger can be set equal to the room air temperature in
a short time, reliably suppressing the occurrence of condensation.
Note that hereinafter, the term "interior" refers to inside a room
subject to cooling and the term "exterior" refers to outside such
room. The terms "indoor" and "outdoor" refer to inside and outside
a building.
SUMMARY
[0004] A natural circulation-type (vapor-phase circulation) cooling
system that does not include a compressor and cools a room by
enabling refrigerant to naturally circulate between a first heat
exchanger installed inside a room (indoors) and a second heat
exchanger installed usually outside the room (and in particular,
outdoors) is known. Such natural circulation-type cooling system is
advantageous in that it is possible to cool a room with little
power consumption when the temperature of outside the room is lower
than that of inside the room. For a natural circulation-type
cooling system, it is important to suppress condensation on the
heat exchanger unit installed in the room.
[0005] With the technology disclosed in Publication No. 2003-347782
mentioned above, if the environment of the surface of the interior
heat exchanger is in a condensation condition even when the outdoor
fan is stopped, circulation of the refrigerant is stopped to
prevent condensation. This means that the above advantage of a
natural circulation-type (vapor-phase circulation) cooling system
is not fully realized.
[0006] One aspect of the present invention is a cooling system
including: a first heat exchanger installed inside a room; a second
heat exchanger installed outside the room; and a piping system that
enables a refrigerant to naturally circulate between the first heat
exchanger and the second heat exchanger. The piping system includes
the first supply pipe and the second supply pipe. The first supply
pipe supplies liquid refrigerant from the second heat exchanger to
the first heat exchanger and the liquid refrigerant is heated by
heat exchanging in a third heat exchanger with vaporized
refrigerant supplied from the first heat exchanger to the second
heat exchanger. The second supply pipe supplies liquid refrigerant
from the second heat exchanger to the first heat exchanger
bypassing the third heat exchanger.
[0007] In this cooling system, the first supply pipe supplies
heated liquid refrigerant, which has been heated with the vaporized
refrigerant in the third heat exchanger, to the first heat
exchanger. Accordingly, even if the temperature of the refrigerant
outputted from (output of) the second heat exchanger is a
temperature at which condensation occurs at the first heat
exchanger unit or lower, by heating the liquid refrigerant using
the third heat exchanger, it is possible to suppress condensation
at the first heat exchanger.
[0008] In addition, since it is possible to cause the refrigerant
to circulate naturally via the first supply pipe even when the
temperature of the liquid refrigerant supplied from the second heat
exchanger is a temperature at which condensation occurs at the
first heat exchanger or lower, it is possible to maintain the
amount (circulated amount) of refrigerant supplied to the second
heat exchanger. This means that even when the temperature of the
liquid refrigerant supplied from the second heat exchanger is a
temperature at which condensation occurs at the first heat
exchanger or lower, it is still possible to cool the room using the
cooling system. Therefore, according to this natural circulation
(vapor-phase circulation)-type cooling system, it is possible to
cool a room with low power consumption or without power consumption
while suppressing condensation at the first heat exchanger unit
even in conditions where the outside air temperature is even
lower.
[0009] On the other hand, when the temperature of the liquid
refrigerant supplied from the second heat exchanger has not fallen
as far as a temperature where condensation occurs at the first heat
exchanger, it is possible to use the second supply pipe to supply
liquid refrigerant from the second heat exchanger to the first heat
exchanger bypassing the third heat exchanger. Accordingly, a drop
in the cooling effect can be suppressed in such cases.
[0010] It is preferable for the piping system to include a
changeover valve system that switches between using the first
supply pipe and the second supply pipe, for the cooling system to
further comprise a control unit that controls the changeover valve
system, and for the control unit to include a function (functional
unit) that switches from the second supply pipe to the first supply
pipe using the changeover valve system when a temperature of liquid
refrigerant outputted from the second heat exchanger becomes equal
to or below a first set temperature. It is possible to
automatically select the first supply pipe and the second supply
pipe according to the temperature of the liquid refrigerant. A
typical example of the first set temperature is a temperature at
which there is the risk of condensation occurring at the first heat
exchanger.
[0011] One of aspects of the second heat exchanger includes a
second tube and a second fan that supplies outside air to the
second tube. It is possible to drive the second fan and maintain
the cooling effect while suppressing condensation at the first heat
exchanger even in conditions where the outside air temperature is
low.
[0012] In addition, the control unit may include a function
(functional unit) that stops the second fan before switching from
the second supply pipe to the first supply pipe using the
changeover valve system when the temperature of the liquid
refrigerant outputted from the second heat exchanger becomes equal
to or below the first set temperature. By stopping the second fan
that consumes power before switching from the second supply pipe to
the first supply pipe, it is possible to cool the room even more
efficiently. The first heat exchanger includes a first tube and may
include or not include a first fan that supplies room air to the
first tube. By omitting the first fan, it is possible to cool the
room with even lower power consumption.
[0013] The control unit may preferably include a function
(functional unit) that closes the first supply pipe and the second
supply pipe using the changeover valve system when the temperature
of the outside air becomes equal to or below a second set
temperature that is lower than the first set temperature. When the
temperature of the liquid refrigerant supplied to the first heat
exchanger becomes a temperature at which condensation occurs at the
first heat exchanger or lower even when such liquid refrigerant is
heated by the third heat exchanger, by stopping the circulation of
the refrigerant, it is possible to prevent condensation at the
first heat exchanger.
[0014] Another aspect of the present invention is a hybrid air
conditioning system including: the cooling system described above,
and a main air conditioning system that further cools air that has
been cooled by the first heat exchanger of the cooling system and
supplies the cooled air.
[0015] Yet another aspect of the present invention is a control
method for a cooling system including a first heat exchanger
installed inside a room, a second heat exchanger installed outside
the room, and a piping system that enables a refrigerant to
naturally circulate between the first heat exchanger and the second
heat exchanger. The piping system included in the cooling system
includes: a first supply pipe that supplies liquid refrigerant,
which has been heated by heat exchanging in a third heat exchanger
with vaporized refrigerant supplied from the first heat exchanger
to the second heat exchanger, from the second heat exchanger unit
to the first heat exchanger unit; a second supply pipe that
supplies liquid refrigerant from the second heat exchanger to the
first heat exchanger bypassing the third heat exchanger; and a
changeover valve system that switches between using the first
supply pipe and the second supply pipe. This control method
includes a step (a step of switching) of having a control unit that
controls the changeover valve system switch from the second supply
pipe to the first supply pipe using the changeover valve system
when a temperature of liquid refrigerant outputted from the second
heat exchanger becomes equal to or below a first set
temperature.
[0016] According to this control method, when the temperature of
the liquid refrigerant supplied from the second heat exchanger is
equal to or below a first set temperature, typically a temperature
at which there is a risk of condensation occurring at the first
heat exchanger, it is possible to switch the circulation path of
the refrigerant from the second supply pipe to the first supply
pipe to suppress condensation at the first heat exchanger.
[0017] When the second heat exchanger includes a second tube and a
second fan that supplies outside air to the second tube, the
control method may further comprise a step of stopping the second
fan before the switching when the temperature of the liquid
refrigerant outputted from the second heat exchanger becomes equal
to or below the first set temperature.
[0018] Compared to switching the circulation path of the
refrigerant from the second supply pipe to the first supply pipe,
it is possible to further lower the power consumption by stopping
the second fan, and there is also the possibility of suppressing
condensation at the first heat exchanger.
[0019] The control method may preferably further include a step of
closing the first supply pipe and the second supply pipe using the
changeover valve system when the temperature of the outside air
becomes equal to or below a second set temperature that is lower
than the first set temperature.
[0020] By doing so, it is possible to stop the circulation of the
refrigerant when the temperature of the liquid refrigerant supplied
to the first heat exchanger has fallen to a temperature where
condensation occurs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 shows an overview of a hybrid air conditioning system
including a cooling system according to an embodiment of the
present invention;
[0022] FIG. 2 is a diagram schematically showing circulation of
refrigerant in the cooling system;
[0023] FIG. 3 is a diagram schematically showing circulation of
refrigerant by the cooling system when the outside air temperature
is even lower;
[0024] FIG. 4 shows one example of an interior heat exchanger;
[0025] FIG. 5 is a flowchart of a control method for the cooling
system; and
[0026] FIG. 6 shows an overview of a hybrid air conditioning system
including a cooling system according to another embodiment of the
present invention.
DETAIL DESCRIPTION
[0027] FIG. 1 shows one example of a cooling system of a data
center. This cooling system (hybrid air-conditioning system) 10a
cools the servers 5 and the room (indoors) 1. A raised (access)
floor 2 has a two-level construction composed of a floor surface 2a
and an underfloor 2b. The cooling system 10a supplies cooling air
61 to a plurality of servers 5 disposed on the floor surface 2a
using the space of underfloor 2b. The hybrid air-conditioning
system 10a includes a floor-standing main air conditioning system
20 and a cooling system (supplementary air conditioning system) 11
disposed near the ceiling 3 of the room 1.
[0028] The main air conditioning system 20 includes a
floor-standing indoor (interior) unit 21 and an outdoor unit 29.
The indoor unit 21 includes an evaporator 24 including cooling
tubes, a heater 25, and an interior fan (indoor fan) 22. The indoor
unit 21 takes in air via an intake 23a at a ceiling side of the
indoor unit 21, controls the temperature of the air, and expels air
(cooling air) 61 whose temperature has been controlled into the
underfloor space 2b from an outtake 23b provided so as to pass
through the floor 2. The outdoor unit 29 includes a compressor 26,
an outside fan 27, and a condenser 28.
[0029] In the main air conditioning system 20, refrigerant that has
been compressed by the compressor 26 is cooled by the condenser 28
using the outside air temperature, then, in the evaporator 24 of
the indoor unit 21, by reducing the pressure and evaporating the
refrigerant to evaporate, the cooling air 61 is generated. In the
indoor unit 21, the air 65 drawn in from the intake 23a by the
interior fan 22 is cooled by the evaporator 24 and the resulting
cooling air 61 is expelled to the underfloor space 2b to cool the
servers 5. At the servers 5, electronic equipment inside the
servers 5 is cooled by the cooling air 61 supplied from the
underfloor space 2b and heated air 62 is discharged toward the
ceiling 3.
[0030] FIGS. 2 and 3 show the cooling system 11 extracted from the
hybrid air-conditioning system 10a. FIG. 2 schematically shows
circulation (cycling) of the refrigerant in a state where the
outside temperature is lower than the room temperature but is not
sufficiently low to cause condensation to occur in the room. FIG. 3
shows circulation (cycling) of the refrigerant in a state where the
outside temperature is low and there is the possibility that
condensation would occur if no countermeasures were taken.
[0031] The cooling system 11 includes a first heat exchanger (or
"interior heat exchanger", "interior heat exchanger unit", "indoor
heat exchanger unit", or "room apparatus") 30 that is installed in
the room (indoors) and a second heat exchanger (or "exterior heat
exchanger", "exterior heat exchanger unit", "outside heat exchanger
unit", or "outside apparatus") that is installed outside the room,
typically installed outdoor (outside). The interior heat exchanger
30 includes a plurality of interior tubes (first tubes) 31 disposed
at an angle or perpendicular to (i.e., vertically) the ceiling 3 of
the room 1 that extends in the horizontal direction (note that only
one indoor tube is shown in the drawings), a supply header 32 that
is supplied with liquefied refrigerant, and a discharge header 33
that collects vaporized refrigerant, with the plurality of interior
tubes 31 being connected to both the supply header 32 and the
discharge header 33. Note that the in-room heat exchanger 30
according to the present embodiment does not include a fan
(interior fan).
[0032] In the interior heat exchanger 30, the discharge header 33
is disposed closer to the ceiling 3 than the supply header 32. This
means that the plurality of interior tubes 31 extend diagonally or
vertically upward from the supply header 32 toward the discharge
header 33.
[0033] The interior heat exchanger 30 includes the interior tubes
31 that are disposed in a housing 39. In FIG. 1, in the same way as
the interior tubes 31, the housing 39 is installed so as to be
inclined with respect to the ceiling 3. The upper surface of the
housing 39 is a supply opening 38a through which air is supplied to
the interior tubes 31, and the lower surface of the housing 39 is
an outtake 38b that discharges air that has been cooled by the
interior tubes 31. The outtake 38b is connected via a duct 37 to
the intake 23a of the floor-standing interior unit 21.
[0034] Note that although the interior heat exchanger 30 is
supported via the duct 37 by the floor-standing interior unit 21 in
this supplementary air conditioning system 11, it is also possible
to suspend the interior heat exchanger 30 from the ceiling 3 using
an appropriate method or to support the interior heat exchanger 30
from the floor 2. Also, the housing 39 may be disposed or installed
so as to be perpendicular to the ceiling 3.
[0035] The exterior heat exchanger 40 is outside the room (and
typically outdoors) 9 and includes a plurality of exterior tubes
(second tubes) 41 installed at a higher position than the interior
tubes 31, a supply header 42 that is supplied with vaporized
refrigerant, and a discharge header 43 that discharges liquid
refrigerant, with the plurality of exterior tubes 41 connecting the
supply header 42 and the discharge header 43. In this exterior heat
exchanger 40 the supply header 42 supplied with the vaporized
refrigerant is disposed so as to be positioned higher than the
discharge header 43 that discharges liquid refrigerant and the
exterior tubes 41 are disposed in the perpendicular direction so as
to join the supply header 42 and the discharge header 43. The
exterior heat exchanger 40 further includes an exterior fan (second
fan) F2 that forcibly supplies outside air 8 to the exterior tubes
41 and a fan motor 45 that drives the exterior fan F2. In this
exterior heat exchanger 40, the exterior fan F2 suctions the air
for supplying the air to the exterior tubes 41.
[0036] Typical examples of the interior tubes 31 and the exterior
tubes 41 are aluminum tubes or copper tubes, and such tubes may be
equipped with fins or may be finless. When fins are used, such fins
may be corrugated, plate-like, or in the form of spines. The
refrigerant may be any refrigerant that vaporizes at room
temperature and liquefies at outside air temperature as operating
conditions, and as one example, HFC134a (whose chemical formula is
CH.sub.2FCF.sub.3) may be used.
[0037] The cooling system 11 further includes a piping system 70
that enables the refrigerant to naturally circulate between the
interior heat exchanger 30 and the exterior heat exchanger 40. The
piping system 70 of the cooling system 11 connects (fluidly
connects) the interior tubes 31 of the interior heat exchanger 30
and the exterior tubes 41 of the exterior heat exchanger 40 with no
compressor in between.
[0038] The piping system 70 includes pipes (or "connecting pipes"
or "supply pipes") 71 to 75 and a changeover valve system 76. The
first supply pipe 71 is a pipe for liquid refrigerant and connects
(fluidly connects) an outlet pipe 73 of the exterior heat exchanger
40 and an inlet pipe 74 of the interior heat exchanger 30. From the
exterior heat exchanger 40-side, a first valve CV1 and an internal
heat exchanger (or "third heat exchanger") 90 are provided on the
first supply pipe 71. A pipe (vaporized refrigerant supply pipe) 75
for vaporized refrigerant (i.e., refrigerant that has boiled and
vaporized in the interior tubes 31) that supplies vaporized
refrigerant from the interior heat exchanger 30 to the exterior
heat exchanger 40 is connected (fluidly connected) to the internal
heat exchanger 90 so as to the vaporized refrigerant pass thought
the internal heat exchanger 90, with the liquid refrigerant
supplied by the first supply pipe 71 being heated inside the
internal heat exchanger 90 and supplied to the interior heat
exchanger 30. Accordingly when the first valve CV1 is opened,
liquid refrigerant that has been heated by vaporized refrigerant in
the internal heat exchanger 90 can be supplied via the first supply
pipe 71 to the interior heat exchanger 30. That is, the first
supply pipe 71 is a pipe for supplying liquid refrigerant, which
has been heated by heat exchange with vaporized refrigerant
supplied from the interior heat exchanger 30 to the exterior heat
exchanger 40 in the internal heat exchanger 90, from the exterior
heat exchanger 40 to the interior heat exchanger 30.
[0039] The second supply pipe 72 is a pipe for liquid refrigerant
that connects (fluidly connects) the outlet pipe 73 of the exterior
heat exchanger 40 and the inlet pipe 74 of the interior heat
exchanger 30. A second valve CV2 is provided on the second supply
pipe 72 between the branch of the first supply pipe 71 and the
interior heat exchanger 30. The second supply pipe 72 connects the
outlet pipe 73 of the exterior heat exchanger 40 and the inlet pipe
74 of the interior heat exchanger so as to bypass the internal heat
exchanger (the third heat exchanger) 90. Accordingly, when the
second valve CV2 is opened, liquid refrigerant can be supplied to
the interior heat exchanger 30 via the second supply pipe 72 so as
to bypass the internal heat exchanger 90.
[0040] The third supply pipe (vaporized refrigerant supply pipe) 75
is a pipe for supplying vaporized refrigerant (i.e., refrigerant
that has boiled and vaporized in the interior tubes 31) from the
interior heat exchanger 30 to the exterior heat exchanger 40. The
liquid refrigerant supply pipes (the first and second supply pipes)
71 and 72 and the vaporized refrigerant supply pipe 75 fluidly
connect between the interior heat exchanger 30 and the exterior
heat exchanger 40 disposed higher than the interior heat exchanger
30 so that fundamentally no counter gradient is produced midway in
the pipes.
[0041] FIG. 4 shows one example of the internal heat exchanger (the
third heat exchanger) 90. The internal heat exchanger 90 shown in
FIG. 4 is a double pipe-type heat exchanger and includes an outer
pipe 91 provided so as to surround the outside of the supply pipe
75 through which the vaporized refrigerant 81 flows. Heat
exchanging occurs between the vaporized refrigerant 81 passing
through inside the inner pipe 75 and the liquid refrigerant 82
passing through inside the outer pipe 91, and warmed (heated)
liquid refrigerant 82 is supplied to the interior heat exchanger
30. The outer pipe 91 also has a function as a receiver with a
storage capacity of several hundred cubic centimeters to several
liters of refrigerant. When the cooling system 11 is constructed,
after the pipes 71 to 75 have been connected, it is possible to
fill the pipes 71 to 75 with refrigerant that is held in advance in
the outer pipe 91 of the internal heat exchanger 90. The internal
heat exchanger 90 is installed in the housing 39 with interior heat
exchanger 30. It is possible to dispose the internal heat exchanger
(the third heat exchanger) separately from the interior heat
exchanger 30, or with the exterior heat exchanger 40.
[0042] The changeover valve system 76 is used to switch between the
first supply pipe 71 and the second supply pipe 72. The changeover
valve system 76 according to the present embodiment includes the
first valve CV1 and the second valve CV2. The first valve CV1 is
provided at a position midway on the first supply pipe 71, in this
case, that is at a position close to the exterior heat exchanger
40-side branching point between the first supply pipe 71 and the
second supply pipe 72. The second valve CV2 is provided at a
position midway on the second supply pipe 72, in this case, that is
close to the exterior heat exchanger 40-side branching point
between the first supply pipe 71 and the second supply pipe 72.
Note that the changeover valve system 76 only needs to switch
between the first supply pipe 71 and the second supply pipe 72 and
may be a three-way valve that replaces the two valves CV1 and
CV2.
[0043] The cooling system 11 further includes temperature sensors
TH1 to TH4. The first temperature sensor TH1 is disposed close to
an air inlet 38a of the interior heat exchanger 30 and using the
first temperature sensor TH1, it is possible to detect the room
temperature of the server room 1. The second temperature sensor TH2
is disposed close to an air outlet 38b of the interior heat
exchanger 30 and using the second temperature sensor TH2, it is
possible to detect the temperature of the airflow 65 outputted from
the interior heat exchanger 30.
[0044] The third temperature sensor TH3 is installed on the outlet
pipe 73 of the exterior heat exchanger 40, that is, on the exterior
heat exchanger unit 40-side (i.e., upstream) of the branching point
between the first supply pipe 71 and the second supply pipe 72.
Using the third temperature sensor TH3, it is possible to detect
the temperature of the liquid refrigerant outputted from (output
of) the exterior heat exchanger 40. The fourth temperature sensor
TH4 is disposed on an air intake side of the exterior heat
exchanger 40 and using the fourth temperature sensor TH4, it is
possible to detect the temperature (outside air temperature)
outside the room.
[0045] The supplementary cooling system 11 further includes a
control unit 50 that controls a fan motor 45 of the interior fan F2
and the changeover valve system 76 (in the present embodiment, the
opening and closing of the valves CV1 and CV2). The control unit 50
includes a first functional unit 51, a second functional unit 52,
and a third functional unit 53.
[0046] The first functional unit 51 includes a function that
switches from the second supply pipe 72 to the first supply pipe 71
using the changeover valve system 76 when the temperature of the
liquid refrigerant outputted from the exterior heat exchanger 40
(i.e., the temperature detected by the third temperature sensor
TH3) becomes equal to or below a first set temperature and if the
interior fan F2 has already stopped. In the present embodiment, the
first temperature is set as a dew point temperature TD of the
server room 1. For example, the humidity inside the server room 1
is controlled using a humidifier or the like so that the dew point
is 15.degree. C. or higher according to environmental guidelines
intended to prevent static electricity and the like. Accordingly,
one example of the dew point temperature TD is 15.degree. C. When
the temperature of the liquid refrigerant supplied to the interior
heat exchanger 30 is equal to or below the dew point temperature
TD, there is the possibility of at least part of the interior tubes
31 of the interior heat exchanger 30 reaching the temperature of
the liquid refrigerant, that is, the dew point temperature TD or
below, which means there is the possibility of condensation on the
surfaces of the interior tubes 31.
[0047] In this cooling system 11, the interior heat exchanger 30
does not include an interior fan. Accordingly, the speed of the
airflows that pass the interior tubes 31 is not especially high and
there is little possibility of water that has condensed on the
surfaces of the interior tubes 31 becoming included in the airflow
65. However, when condensation occurs on the interior tubes 31, it
is not possible to eradicate the risk of the resulting moisture
somehow affecting the servers 5. For this reason, when the
temperature of the liquid refrigerant detected by the temperature
sensor TH3 is equal to or below the dew point temperature TD, the
first supply pipe 71 is selected by the first functional unit 51
and the liquid refrigerant is heated by the vaporized refrigerant
using the internal heat exchanger 90. Also, by supplying the liquid
refrigerant that has been heated above the dew point temperature TD
to the interior heat exchanger 30, the occurrence of condensation
on the surfaces of the interior tubes 31 is prevented.
[0048] The second functional unit 52 includes a function that stops
the exterior fan F2 before the changeover valve system 76 switches
from the second supply pipe 72 to the first supply pipe 71 when the
temperature of the liquid refrigerant outputted from the exterior
heat exchanger 40 is equal to or below the first set temperature
(the dew point temperature TD) and if the interior fan F2 has not
stopped. By stopping the exterior fan F2, it is possible to lower
the heat exchanging efficiency of the exterior heat exchanger 40,
which means that there is the possibility of raising the
temperature of the liquid refrigerant supplied from the exterior
heat exchanger 40. In addition, by stopping the exterior fan F2, it
is possible to reduce the power consumption. Accordingly, when the
temperature of the liquid refrigerant detected by the temperature
sensor TH3 becomes equal to or below the dew point temperature TD,
by stopping the exterior fan F2 using the second functional unit 52
before using the first functional unit 51, the occurrence of
condensation on the surfaces of the interior tubes 31 is
prevented.
[0049] When the wind speed outdoors is high and/or the outside
temperature is lower, there are cases where the temperature of the
liquid refrigerant supplied from the exterior heat exchanger 40
will become equal to or below the dew point temperature TD even if
the exterior fan F2 is stopped. In such case, by having the first
functional unit 51 operate following the second functional unit 52
to heat the liquid refrigerant in the internal heat exchanger 90,
the temperature of the liquid refrigerant supplied to the interior
heat exchanger 30 is raised to the dew point temperature TD or
higher. Accordingly, with the cooling system 11, it is possible to
enable the refrigerant to naturally circulate between the interior
heat exchanger 30 and the exterior heat exchanger 40 and to expel
the thermal load of the server room 1 outdoors, even under
conditions where the temperature of the liquid refrigerant supplied
from the exterior heat exchanger 40 is at the dew point temperature
TD or below even when the outside fan F2 is stopped.
[0050] By bypassing using the second functional unit 52, the first
functional unit 51 may switch, by the changeover valve system 76,
from the second supply pipe 72 to the first supply pipe 71 without
stopping the exterior fan F2 when the temperature of the liquid
refrigerant supplied from the exterior heat exchanger 40 becomes
equal to or below the first set temperature (the dew point
temperature TD). By continuously driving the interior fan F2, both
of a drop in the cooling performance and condensation of the
interior heat exchanger 30 can be suppressed without lowering the
heat exchanging performance of the exterior heat exchanger 40.
[0051] The third functional unit 53 includes a function that closes
both the first supply pipe 71 and the second supply pipe 72 using
the changeover valve system 76 when the outside air temperature
detected by the fourth temperature sensor TH4 is equal to or below
the second set temperature. If the outside air temperature has
fallen excessively and so low as to exceed the performance of the
internal heat exchanger 90, there are cases where the temperature
of the liquid refrigerant supplied to the interior heat exchanger
30 will be equal to or below the dew point temperature TD even if
the interior fan F2 is stopped and the liquid refrigerant is heated
in the internal heat exchanger 90. The third functional unit 53
shuts off circulation of the liquid refrigerant between the
exterior heat exchanger 40 and the interior heat exchanger 30 in
such state to prevent condensation from occurring at the interior
heat exchanger 30. The second set temperature is set lower than the
first set temperature, and as one example, the second set
temperature is set at -20.degree. C.
[0052] In this way, in the cooling system 11, in a case (normal
state, regular state) where the temperature of the liquid
refrigerant outputted from the exterior heat exchanger 40 is above
the first set temperature (the dew point temperature TD or above),
as shown in FIG. 2, the refrigerant circulates via the second
supply pipe 72. That is, the circulation route of the refrigerant
is the exterior heat exchanger 40.fwdarw.the supply pipe
73.fwdarw.the second supply pipe 72 (the valve CV2).fwdarw.the
supply pipe 74.fwdarw.the interior heat exchanger 30.fwdarw.the
third supply pipe 75.fwdarw.the exterior heat exchanger 40. Note
that in the present embodiment, the second supply pipe 72 (the
valve CV2) and the supply pipe 74 are in the housing 39 of the
interior heat exchanger 30.
[0053] On the other hand, when the temperature of the liquid
refrigerant outputted from the exterior heat exchanger 40 is equal
to or below the first set temperature (dew point temperature TD or
above), as shown in FIG. 3, the refrigerant circulates via the
first supply pipe 71. That is, the circulation route of the
refrigerant is the exterior heat exchanger 40.fwdarw.the supply
pipe 73.fwdarw.the first supply pipe 71 (the valve CV1) and the
internal heat exchanger 90.fwdarw.the supply pipe 74.fwdarw.the
interior heat exchanger 30.fwdarw.the third supply pipe
75.fwdarw.the exterior heat exchanger 40.
[0054] In this cooling system 11, the interior tubes 31 of the
interior heat exchanger 30 contact a region along the ceiling 3 of
the room 1, that is, a high-temperature air zone 63 in the upper
part of the room 1, at an angle. When the refrigerant (liquid
refrigerant) inside the interior tubes 31 is heated by the
high-temperature air zone 63, the refrigerant boils and vaporizes.
On the other hand, since the air of the high-temperature air zone
63 loses heat, such air is cooled to produce down flow 65 that
flows downward from the region close to the ceiling 3 of the room
1. This flow of air (down flow) 65 flows substantially vertically.
Since the interior tubes 31 are disposed so as to be inclined,
effective contact is made with the high-temperature air zone 63
that extends in the horizontal direction and the down flow 65 is
efficiently produced. Accordingly, it is possible to cool the room
1 comparatively efficiently even when an interior fan is not
provided. Note that an interior fan (or "first fan") may be
provided.
[0055] In addition, since the interior tubes 31 are inclined with
respect to the ceiling 3, the interior tubes 31 draws hot air so as
not to interfered with the down flow 65. Accordingly, the air in
the high-temperature air zone 63 along the ceiling 3 is efficiently
drawn in by the interior heat exchanger 30 to form a certain air
flow 64 in the high-temperature air zone 63. This means that
according to the cooling system 11, it is possible to eradicate hot
spots formed at upper parts of the servers 5 comparatively easily,
to promote heat exchanging at the servers 5, and to cool the
servers 5 even more effectively.
[0056] In this way, with the interior heat exchanger 30,
comparatively hot air 64 flows from a nearly horizontal direction
substantially across the ceiling 3 into the air intake opening 38a
and cooled air 65 is discharged in a substantially vertical
direction from the outtake 38b. Although the cooling system 11 is
capable of cooling the server room 1 on its own, in the example
shown in FIG. 1, the cooling system 11 functions as a supplementary
air conditioning system for the main air conditioning system 20.
The air 65 that has been discharged from the interior heat
exchanger 30 of the cooling system 11 is drawn in from the intake
23a of the floor-standing interior unit 21, is cooled further, and
then supplied to the servers 5. Accordingly, under a condition
where a cooling effect is manifested by the cooling system 11, the
load of the main air conditioning system 20 can be reduced, thereby
reducing the power consumption of the main air conditioning system
20. When the interior heat exchanger 30 of the cooling system 11 is
used as a supplementary air conditioning system, inside the room it
is possible to use an air flow produced by a fan of the main air
conditioning system 20. Accordingly, it is possible to omit the
interior fan of the cooling system 11.
[0057] In addition, in the cooling system 11, since the refrigerant
(vaporized refrigerant) that has boiled and vaporized in the
interior tubes 31 of the interior heat exchanger 30 circulates in
the piping system 70 due to the difference in specific gravity with
the liquid refrigerant, a compression device such as a compressor
or a pump is not required and aside from fans, fundamentally no
power is consumed. Accordingly, it is possible to provide the air
conditioning system that has high efficiency and low power
consumption. In addition, in the cooling system 11, since the
interior tubes 31 are disposed at an angle, air in the room 1 is
caused to circulate and to efficiently contact the interior tubes
31. Accordingly, an interior fan does not need to be provided in
the interior heat exchanger 30 and the driving force (power)
required by such a fan is also unnecessary.
[0058] Also, with the cooling system 11, even if the outside air
temperature falls and the temperature of the liquid refrigerant
supplied from the exterior heat exchanger 40 becomes equal to the
dew point or below, by using the internal heat exchanger 90 to heat
the liquid refrigerant using the vaporized refrigerant, it is
possible to circulate the refrigerant with fundamentally no power
consumption and to maintain the cooling performance by natural
circulation. Therefore, according to the cooling system 11, it is
possible to cool the room 1 with a natural circulation cycle during
the night and day and throughout the year, even under conditions
where the outside temperature is low, and possible to further
reduce the power consumption required by cooling (air
conditioning).
[0059] FIG. 5 is a flowchart explaining one example of the control
method of the cooling system 11. If in step 101 the outside air
temperature detected by the temperature sensor TH4 is above
-20.degree. C. and in step 102 the temperature of the liquid
refrigerant outputted from the exterior heat exchanger 40 (i.e.,
the temperature detected by the temperature sensor TH3) is greater
than the dew point TD, in step 103 the cooling system 11 is driven
with the first valve CV1 closed and the second valve CV2 open. By
doing so, the refrigerant is circulated in a cycle made up of the
exterior heat exchanger 40.fwdarw.the supply pipe 73.fwdarw.the
second supply pipe 72 (the valve CV2).fwdarw.the supply pipe
74.fwdarw.the interior heat exchanger 30.fwdarw.the supply pipe
75.fwdarw.the exterior heat exchanger 40 to cool the room 1 (see
FIG. 2). Note that in a condition where the outside temperature is
higher than the room temperature and the refrigerant is not
condensed in the exterior heat exchanger 40, the refrigerant is not
circulated and the room is not cooled using the cooling system
11.
[0060] If in step 102 the temperature (temperature sensor TH3) of
the liquid refrigerant outputted from the exterior heat exchanger
40 is not greater than the dew point TD, the second function 52
first confirms in step 104 whether the fan F2 is operating and if
the fan F2 is operating, stops the fan F2 (the fan motor 45) in
step 105. By doing so, it is possible to suppress the heat
discharging performance of the exterior heat exchanger 40, which
means there is the possibility that the temperature (temperature
sensor TH3) of the liquid refrigerant outputted from the exterior
heat exchanger 40 will become above the dew point TD. After
stopping the fan F2, operation of the cooling system 11 continues
in a state where the fan F2 is stopped.
[0061] If in step 102 the temperature (temperature sensor TH3) of
the liquid refrigerant outputted from the exterior heat exchanger
40 is equal to or below the dew point TD and in step 104 the fan F2
has already stopped, in step 106 the first function 51 opens the
first valve CV1 and closes the second valve CV2. By doing so, the
refrigerant is circulated in a cycle made up of the exterior heat
exchanger 40.fwdarw.the supply pipe 73.fwdarw.the first supply pipe
71 (the valve CV1) and the internal heat exchanger 90.fwdarw.the
supply pipe 74.fwdarw.the interior heat exchanger 30.fwdarw.the
supply pipe 75.fwdarw.the exterior heat exchanger 40 (see FIG. 3).
Note that in this example, the first supply pipe 71 (the valve CV1)
and the supply pipe 74 are included in the housing 39 of the
interior heat exchanger 30. In this cycle, since the liquid
refrigerant is heated by the vaporized refrigerant inside the
internal heat exchanger (the third heat exchanger) 90, it is
possible to circulate the refrigerant even when the temperature
(temperature sensor TH3) of the liquid refrigerant supplied from
the exterior heat exchanger 40 becomes equal to or below the dew
point TD. Therefore, the amount of circulating refrigerant is
maintained) This means that it is possible to move heat inside the
room out of the room and continue cooling the room 1 using the
natural circulation-type cooling system 11.
[0062] If, as described earlier, steps 104 and 105 are omitted and
the temperature (temperature sensor TH3) of the liquid refrigerant
supplied from the exterior heat exchanger 40 in step 102 is equal
to or below the dew point TD, switching of the valves may be
carried out by the first functional unit 51 in step 106.
[0063] If, in step 101, the outside air temperature detected by the
temperature sensor TH4 is equal to or below -20.degree. C., in step
107 the third functional unit 53 closes both the first valve CV1
and the second valve CV2 to stop the circulation of the
refrigerant.
[0064] FIG. 6 shows an overview of a hybrid air conditioning system
10b according to another embodiment of the present invention. In
the air conditioning system 10b, the main air conditioning system
20 and the cooling system 11 are disposed in an air conditioning
room 7 adjacent to the server room 1, and a partition wall 6 is
provided between the server room 1 and the air conditioning room 7.
The main air conditioning system 20 takes in air from the server
room 1 via an upper opening 6a of the partition wall 6 and cools
such air before expelling the air from an underfloor opening 6b to
an underfloor of the server room 1. Accordingly, the air
conditioning room becomes negatively pressured with respect to the
server room 1.
[0065] The interior heat exchanger 30 of the cooling system 11 that
functions as a supplementary system for the main air conditioning
system 20 is attached so as to face the upper opening 6a of the
partition wall 6. Accordingly, the interior tubes 31 of the
interior heat exchanger 30 are disposed substantially vertically
along the partition wall 6. Due to the pressure difference between
the server room 1 and the air conditioning room 7, air (warm air)
from the server room 1 is supplied to the interior tubes 31, and
since the interior tubes 31 extend in the vertical direction, there
is high contact efficiency, resulting in the air in the server room
1 being efficiently cooled by the interior tubes 31 and then drawn
into the main air conditioning system 20. The exterior heat
exchanger 40 of the cooling system 11 is disposed above (i.e., at a
higher position than) the interior heat exchanger 30, for example
on a deck provided on a higher floor than the floor on which the
servers 5 are installed.
[0066] In this way, according to the hybrid air conditioning
systems 10a and 10b that include the cooling system 11 and the
control methods thereof, it is possible to operate the natural
circulation-type cooling system 11 even if the temperature of the
liquid refrigerant supplied from the exterior heat exchanger 40 is
equal to or below the dew point, which means that it is possible to
carry out cooling with low power consumption over an even longer
period. Accordingly, it is possible to provide an air conditioning
system with an even lower running cost.
[0067] Also, although an example of a cooling system installed in a
data center has been described above, the cooling load for the
present invention is not limited to information equipment such as
servers. The cooling system and hybrid air conditioning system
according to the present invention can also be favorably used for
cooling in conditions where it is not possible to open a window to
let in breezes, such as when cooling a clean room.
[0068] In addition, although a cooling system according to the
present invention has been described for an example where the
system is combined with a floor-standing cooling system, it is also
possible to use the system according to the present invention alone
or in combination with another type of air conditioning system.
Also, aside from being used alone, the cooling system according to
the present invention may be used according to a variety of other
methods, such as in combination with an existing cooling system, in
accordance with the conditions and environment for cooling.
[0069] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *