U.S. patent application number 13/144658 was filed with the patent office on 2011-11-10 for heat transfer arrangement and electronic housing comprising a heat transfer arrangement and method of controlling heat transfer.
This patent application is currently assigned to TELEFONAKTIEBOLAGET L M ERICSSON (PUBL). Invention is credited to Klas Hedberg, Gustaf Wigren.
Application Number | 20110271696 13/144658 |
Document ID | / |
Family ID | 41056740 |
Filed Date | 2011-11-10 |
United States Patent
Application |
20110271696 |
Kind Code |
A1 |
Hedberg; Klas ; et
al. |
November 10, 2011 |
Heat Transfer Arrangement and Electronic Housing Comprising a Heat
Transfer Arrangement and Method of Controlling Heat Transfer
Abstract
A heat transfer arrangement comprises a refrigerant circuit
(102). The refrigerant circuit (102) comprises an evaporator (104)
adapted to be arranged inside an electronic component housing
(202), a condenser (108) adapted to be arranged outside the
electronic component housing (202), a first conduit leading (106)
from the evaporator (104) to the condenser (108), and a second
conduit leading from the condenser (108) to the evaporator (104). A
refrigerant is present in the refrigerant circuit (102) and in use,
under first temperature conditions, is arranged to self-circulate
in the refrigerant circuit (102) by evaporating in the evaporator
(104), rising as a gas through the first conduit, condensing in the
condenser (108) and flowing through the second conduit to the
evaporator (104). In the refrigerant circuit (102) a further
separate gas or separate gas mixture is present in a quantity such
that in use, under second temperature conditions, said quantity of
further separate gas or separate gas mixture expands inside the
condenser (108) to thereby displace refrigerant from the condenser
(108). Heat transfer is thus controlled. Also an electronic
component housing comprising such a heat transfer arrangement and a
method of controlling heat transfer from such an electronic housing
are provided.
Inventors: |
Hedberg; Klas; (Huddinge,
SE) ; Wigren; Gustaf; (Vaxholm, SE) |
Assignee: |
TELEFONAKTIEBOLAGET L M ERICSSON
(PUBL)
Stockholm
SE
|
Family ID: |
41056740 |
Appl. No.: |
13/144658 |
Filed: |
January 15, 2009 |
PCT Filed: |
January 15, 2009 |
PCT NO: |
PCT/SE09/50028 |
371 Date: |
July 14, 2011 |
Current U.S.
Class: |
62/64 ;
62/259.2 |
Current CPC
Class: |
F28D 15/0266 20130101;
F28D 15/06 20130101; H05K 7/2029 20130101 |
Class at
Publication: |
62/64 ;
62/259.2 |
International
Class: |
F25D 31/00 20060101
F25D031/00; F25D 17/02 20060101 F25D017/02 |
Claims
1. A heat transfer arrangement comprising a refrigerant circuit
comprising: an evaporator adapted to be arranged inside an
electronic component housing, a condenser adapted to be arranged
outside the electronic component housing, said condenser being
separate from and arranged above said evaporator, a first conduit
leading from the evaporator to the condenser, and a second conduit
leading from the condenser to the evaporator, wherein a refrigerant
is present in the refrigerant circuit and in use, under first
temperature conditions, is arranged to self-circulate in the
refrigerant circuit by means of gravity and buoyancy forces whereby
said refrigerant is evaporating in the evaporator, rising as a gas
through the first conduit, condensing in the condenser and flowing
through the second conduit to the evaporator and wherein the
refrigerant circuit comprises a further separate gas or separate
gas mixture which is present in a quantity such that in use, under
second temperature conditions, said quantity of further separate
gas or separate gas mixture expands inside the condenser to thereby
displace refrigerant from the condenser such that heat transfer in
the condenser is reduced.
2. The heat transfer arrangement according to claim 1, wherein a
constant weight of the refrigerant and a constant weight of the
further separate gas or separate gas mixture are present in the
refrigerant circuit.
3. The heat transfer arrangement according to claim 1, wherein the
further separate gas or separate gas mixture is present in the
refrigerant circuit at a fixed weight ratio with respect to the
refrigerant.
4. The heat transfer arrangement according to claim 3, wherein the
weight ratio of the further separate gas or gas mixture is in the
interval of 3%-40% of the refrigerant.
5. The heat transfer arrangement according to claim 4, wherein the
weight ratio of the further separate gas or gas mixture is in the
interval of 5%-25% of the refrigerant.
6. The heat transfer arrangement according to claim 1, wherein the
refrigerant has a molecular structure referred to as R134a.
7. The heat transfer arrangement according to claim 1, wherein the
separate gas is nitrogen or the separate gas mixture is air.
8. The heat transfer arrangement according to claim 1, wherein an
outer heat transfer surface of the condenser and/or the evaporator
is/are arranged at an angle (.alpha.) of 5-60 degrees from a
horizontal line.
9. An electronic component housing comprising a heat transfer
arrangement according to claim 1 and further comprising a first gas
moving device for circulating a gas such as air inside the
electronic component housing over an outer surface area of the
evaporator.
10. The electronic component housing according to claim 9,
comprising a second gas moving device for blowing ambient air over
an outer surface area of the condenser.
11. The electronic component housing according to claim 9, wherein
the electronic component housing is part of a radio base
station.
12. A method of controlling heat transfer from an electronic
component housing according to claim 9, to an environment,
comprising the steps of: self-circulating the refrigerant in the
refrigerant circuit, under first temperature conditions, by means
of gravity and buoyancy forces whereby said refrigerant is
evaporating in the evaporator, rising as a gas through the first
conduit, condensing in the condenser and flowing through the second
conduit to the evaporator, controlling the second gas moving
device, stopping the second gas moving device when heat transfer is
to be reduced and, displacing the refrigerant from the condenser,
under second temperature conditions, when a pressure inside the
refrigerant circuit is reduced and the separate gas or separate gas
mixture expands inside the condenser such that heat transfer in the
condenser is reduced.
13. The method of controlling heat transfer according to claim 12,
comprising a step of: controlling the first gas moving device to
circulate a gas inside the electronic component housing over the
outer surface area of the evaporator.
14. The method of controlling heat transfer according to claim 13,
wherein the step of controlling the first gas moving device
includes, reducing a speed of the first gas moving device to a
minimum speed when a limit temperature, in the interval of +5 to
+30 degrees Celsius, inside the electronic component housing is
reached, and maintaining the minimum speed when a temperature
inside the electronic component housing is lower than the limit
temperature.
15. The method of controlling heat transfer according to claim 12,
wherein the step of stopping the second gas moving device is
performed when a temperature inside the electronic component
housing is in the interval of +5 to +20 degrees Celsius and the
second gas moving device is maintained stopped at even lower
temperatures inside the electronic component housing.
Description
TECHNICAL FIELD
[0001] The present invention relates to a heat transfer arrangement
comprising a refrigerant circuit. In use a refrigerant is arranged
to self-circulate in the refrigerant circuit. The invention also
relates to an electronic component housing comprising such a heat
transfer arrangement and a method of controlling heat transfer from
such an electronic housing.
BACKGROUND
[0002] Heat transfer systems utilizing a refrigerant circulating
through an evaporator and a condenser are well known. Such heat
transfer systems wherein the refrigerant self-circulates, i.e.
gravity and buoyancy are forces driving the circulation of the
refrigerant, are sometimes referred to as thermosiphons.
[0003] Some electronic component housings need to be cooled due to
the heat generated by the electronic components inside the housing.
A cooling fan directing air through the housing is sufficient for
some applications and/or under certain operating conditions. For
other applications and/or under other operating conditions a heat
transfer system utilizing a refrigerant, which evaporates in an
evaporator and condenses in a condenser, might be required. The
evaporator would be arranged to use heat from the electronic
components to evaporate the refrigerant and in this way cool the
electronic components.
[0004] WO99/60709 discloses a method and an apparatus for cooling
electronic components of radio base stations installed at elevated
locations. An evaporator of a thermosiphon cooling system is in
thermal contact with heat-generating electronic components to be
cooled. A condenser of the thermosiphon cooling system is arranged
above the evaporator. The condenser is constructed and arranged for
natural convection of ambient air.
[0005] Generally, a modern radio communication system comprises a
radio access network and a number of communication devices. The
radio access network is built up of several nodes, in particular,
radio base stations. The primary task of a radio base station is to
send and receive information to/from the communication devices
within a cell served by the radio base station. In many cases, the
base station is run 24 hours a day. Therefore, it is of particular
interest and importance to ensure that the base station is operable
predictably and reliably. The radio base station comprises an
electronic component housing. Inside the electronic component
housing there are arranged electronic components and circuitry for
performing different tasks of the radio base station. For example,
the circuitry may comprise a power control unit, a radio unit,
comprising a radio amplifier, and a filtering unit for performing
corresponding tasks.
[0006] Heat generated in the circuitry of the base station, in
particular the radio unit, may not always dissipate naturally to a
sufficiently high degree. Instead, heat is accumulated in the
circuitry and temperature of the circuitry increases. The increased
temperature of the circuitry may impair the performance of
circuitry within the radio base station, e.g. the circuitry within
the radio base station may fail. Consequently, unpredicted
interruptions in operation of the base station may occur.
[0007] This is clearly not desired and a thermosiphon cooling
system as disclosed in WO99/60709, mentioned above, could be used
to cool the electronic component housing. WO99/60709 does however
not disclose how cooling may be controlled in a thermosiphon
cooling system. Under certain conditions it is namely desirable to
not cool the electronic component housing in order to avoid a too
low temperature inside the electronic component housing, which also
could harm the electronic components and circuitry inside the
electronic component housing.
SUMMARY
[0008] An object of the present invention is to obviate the above
disadvantage and provide an improved heat transfer arrangement with
a refrigerant arranged to self-circulate. According to an aspect of
the invention, the object is achieved by a heat transfer
arrangement comprising a refrigerant circuit. The refrigerant
circuit comprises an evaporator adapted to be arranged inside an
electronic component housing, a condenser adapted to be arranged
outside the electronic component housing, a first conduit leading
from the evaporator to the condenser, and a second conduit leading
from the condenser to the evaporator. A refrigerant is present in
the refrigerant circuit and in use, under first temperature
conditions, is arranged to self-circulate in the refrigerant
circuit by evaporating in the evaporator, rising as a gas through
the first conduit, condensing in the condenser and flowing through
the second conduit to the evaporator. In the refrigerant circuit a
further separate gas or separate gas mixture is present in a
quantity such that in use, under second temperature conditions,
said quantity of further separate gas or separate gas mixture
expands inside the condenser to thereby displace refrigerant from
the condenser.
[0009] It is to be understood that the further separate gas or
separate gas mixture remains separate from the refrigerant. That
is, the further separate gas or separate gas mixture may be mixed
with the refrigerant in the refrigerant circuit but it will remain,
under intended operating conditions, a separate gas or separate gas
mixture different from the refrigerant.
[0010] A prevailing pressure inside the refrigerant circuit is
primarily determined by the pressure of gas inside the refrigerant
circuit because a liquid, i.e. in this case liquid refrigerant, is
incompressible. The pressure inside the refrigerant circuit is
dependent on refrigerant saturation pressure at prevailing
temperature. When temperature is high inside and/or outside the
electronic component housing, the pressure inside the refrigerant
circuit is high due to high refrigerant saturation pressure. As
temperature decreases, inside and/or outside the electronic
component housing, the pressure inside the refrigerant circuit
decreases due to a lower refrigerant saturation pressure. Thus,
under the first temperature conditions the temperature inside
and/or outside the electronic component housing is generally higher
than under the second temperature conditions.
[0011] At reduced gas pressure inside the refrigerant circuit, the
further separate gas or separate gas mixture will expand in
comparison with refrigerant in gas form. The refrigerant in gas
form will thus be displaced from the condenser and an inner heat
transfer surface thereof. Heat transfer in the condenser is reduced
and thus also the heat transferred from the electronic component
housing.
[0012] As a result, the above mentioned object is achieved.
[0013] At further reduced gas pressure inside the refrigerant
circuit most of the refrigerant in gas form will have been
displaced from the inner heat transfer surface of the condenser by
the separate gas or separate gas mixture and heat transfer is
reduced to a minimum.
[0014] In example embodiments of the heat transfer arrangement, a
constant weight of the refrigerant and a constant weight of the
further separate gas or separate gas mixture may be present in the
refrigerant circuit. A heat transfer arrangement with an
uncomplicated refrigerant circuit can be used. There is no need for
any additional devices for actively adding or removing the
refrigerant and/or the further separate gas or separate gas mixture
from the refrigerant circuit to control heat transfer.
[0015] In example embodiments of the heat transfer arrangement, the
further separate gas or separate gas mixture may be present in the
refrigerant circuit at a fixed weight ratio with respect to the
refrigerant. Again, a heat transfer arrangement with an
uncomplicated refrigerant circuit can be used and there is no need
for any additional devices for adding or removing the refrigerant
and/or the further separate gas or separate gas mixture from the
refrigerant circuit to control heat transfer.
[0016] In example embodiments the refrigerant circuit may be
defined as comprising only components flowed through by refrigerant
during the self-circulation of refrigerant.
[0017] According to example embodiments the weight ratio of the
further separate gas or gas mixture may be in the interval of
3%-40% of the refrigerant.
[0018] According to example embodiments the weight ratio of the
further separate gas or gas mixture may be in the interval of
5%-25% of the refrigerant.
[0019] In example embodiments the refrigerant may have a molecular
structure referred to as R134a. R134a is a refrigerant having
suitable properties and will operate in temperature intervals
commonly occurring for electronic component housings. Other
refrigerants may also be suitable, as well as e.g. water, methanol
or acetone.
[0020] In example embodiments the separate gas may be nitrogen or
the separate gas mixture may be air. Nitrogen and air are readily
available and will remain separate from the refrigerant in the
refrigerant circuit.
[0021] In example embodiments of the heat transfer arrangement, the
condenser and/or the evaporator may be arranged at an angle of 5-60
degrees from a horizontal line. In this way vertical installation
height of the heat transfer arrangement may be reduced while still
a respective external heat transfer surface of the evaporator
and/or the condenser may be available for lateral exposure.
[0022] According to example embodiments the condenser and/or the
evaporator may be of plate and fin type.
[0023] In an aspect of the invention an electronic component
housing may comprise a heat transfer arrangement as discussed
above. According to example embodiments it may further comprise a
first gas moving device for circulating a gas such as air inside
the electronic component housing over an outer surface area of the
evaporator. In this way cold gas may be transported from the
evaporator to electronic components and warm gas from the
electronic components to the evaporator.
[0024] According to example embodiments the electronic component
housing may comprise a second gas moving device for blowing ambient
air over an outer surface area of the condenser. Heat transfer
between ambient air and the condenser may be improved by
mechanically transporting air over the outer heat transfer
surface.
[0025] According to example embodiments the electronic component
housing may comprise two of the above mentioned heat transfer
arrangements, the evaporators of which are arranged adjacent to
each other inside the electronic component housing. Cooling effect
may in this way be increased inside the electronic housing while
space requirement for a collective heat transfer arrangement is
kept low inside the electronic housing.
[0026] According to example embodiments the electronic component
housing may be part of a radio base station.
[0027] In an aspect of the invention a method of controlling heat
transfer from an electronic component housing, e.g. as mentioned
above, to an environment, may comprise the steps of: [0028]
Self-circulating the refrigerant in the refrigerant circuit, under
first temperature conditions, by evaporating in the evaporator,
rising as a gas through the first conduit, condensing in the
condenser and flowing through the second conduit to the evaporator.
[0029] Controlling the second gas moving device. [0030] Stopping
the second gas moving device when heat transfer is to be reduced,
and [0031] displacing the refrigerant from the condenser, under
second temperature conditions, when a pressure inside the
refrigerant circuit is reduced and the separate gas or separate gas
mixture expands inside the condenser.
[0032] In example embodiments a step of controlling the first gas
moving device to circulate a gas inside the electronic component
housing over the outer surface area of the evaporator, may be
included.
[0033] In example embodiments the step of controlling the first gas
moving device may include: Reducing a speed of the first gas moving
device to a minimum speed when a limit temperature in the interval
of +5 to +30 degrees Celsius inside the electronic component
housing is reached, and maintaining the minimum speed when a
temperature inside the electronic component housing is lower than
the limit temperature. In this way a minimum circulation of gas
inside the electronic component housing is ensured.
[0034] In example embodiments the step of stopping the second gas
moving device may be performed when a temperature inside the
electronic component housing is in the interval of +5 to +20
degrees Celsius and the second gas moving device is maintained
stopped at even lower temperatures inside the electronic component
housing. Heat exchange between the condenser and the environment
will in this way be reduced and thus also heat transferred from
inside the electronic component housing to the environment. Thus,
the heat transfer arrangement will contribute less to further
cooling of the electronic component housing and favourable
temperature conditions may more easily be maintained inside the
electronic component housing.
[0035] Further features of, and advantages with, the present
invention will become apparent when studying the appended claims
and the following description. Those skilled in the art realize
that different features of the present invention may be combined to
create embodiments other than those described in the following,
without departing from the scope of the present invention, as
defined by the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] The various aspects of the invention, including its
particular features and advantages, will be readily understood from
the following detailed description and the accompanying drawings,
in which:
[0037] FIG. 1 illustrates schematically a heat transfer arrangement
according to example embodiments,
[0038] FIG. 2 illustrates schematically an electronic component
housing according to example embodiments comprising a heat transfer
arrangement,
[0039] FIG. 3 illustrates schematically an electronic component
housing according to example embodiments comprising two heat
transfer arrangements, and
[0040] FIG. 4 illustrates an exemplary method for controlling heat
transfer from an electronic housing.
DETAILED DESCRIPTION
[0041] The present invention now will be described more fully with
reference to the accompanying drawings, in which example
embodiments are shown. However, this invention should not be
construed as limited to the embodiments set forth herein. Disclosed
features of example embodiments may be combined as readily
understood by one of ordinary skill in the art to which this
invention belongs. Like numbers refer to like elements
throughout.
[0042] As used herein, the term "comprising" or "comprises" is
open-ended, and includes one or more stated features, elements,
steps, components or functions but does not preclude the presence
or addition of one or more other features, elements, steps,
components, functions or groups thereof.
[0043] As used herein, the term "and/or" includes any and all
combinations of one or more of the associated listed items.
[0044] As used herein, the common abbreviation "e.g.", which
derives from the Latin phrase "exempli gratia," may be used to
introduce or specify a general example or examples of a previously
mentioned item, and is not intended to be limiting of such item. If
used herein, the common abbreviation "i.e.", which derives from the
Latin phrase "id est," may be used to specify a particular item
from a more general recitation.
[0045] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise.
[0046] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein.
[0047] It will be understood that when an element is referred to as
being "coupled" or "connected" to another element, it can be
directly coupled or connected to the other element or intervening
elements may also be present. In contrast, when an element is
referred to as being "directly coupled" or "directly connected" to
another element, there are no intervening elements present.
[0048] Well-known functions or constructions may not be described
in detail for brevity and/or clarity.
[0049] FIG. 1 illustrates schematically a heat transfer arrangement
according to example embodiments. A refrigerant circuit 102
comprises an evaporator 104, a first conduit 106, a condenser 108
and a second conduit 110. Inside the refrigerant circuit 102 there
is a refrigerant and a further separate gas or further separate gas
mixture. The refrigerant in liquid form inside the evaporator 104
evaporates and rises in gas form through the first conduit 106 to
the condenser 108. Inside the condenser 108 the refrigerant in gas
form condenses to liquid and flows through the second conduit 110
back to the evaporator 104. In this manner the refrigerant
self-circulates in the refrigerant circuit 102.
[0050] Gravity and buoyancy are forces driving the
self-circulation. When the condenser 108 is arranged above the
evaporator 104, as schematically shown, an efficient
self-circulation of refrigerant takes place. Liquid refrigerant
will not be collected to any substantial extent in the condenser
108 but will flow through the second conduit 110 down to the
evaporator 104. Also in a refrigerant circuit with the evaporator
and the condenser arranged laterally beside each other and the
first conduit arranged such that refrigerant in gas form can rise
therein, a refrigerant may self-circulate. However, in this case
liquid refrigerant would take up part of the condenser, the
condenser and evaporator being communicating vessels.
[0051] FIG. 2 illustrates schematically an electronic component
housing according to example embodiments comprising a heat transfer
arrangement. The electronic component housing 202 is adapted to
house electronic components 204. In example embodiments the
electric component housing 202 may be a radio base station and the
electric components 204 may be part of devices associated with such
a radio base station, e.g. a radio unit. The heat transfer
arrangement is adapted to cool the electronic components 204 and
comprises a refrigerant circuit 102. An evaporator 104 of the
refrigerant circuit 102 is arranged inside the electric component
housing 202. Further in the refrigerant circuit 102 a first conduit
106 leads from the evaporator 104 to a condenser 108 arranged
outside the electronic component housing 202. From the condenser
108 a second conduit 110 leads back to the evaporator 104. The
refrigerant circuit is filled with a refrigerant and a further
separate gas or further separate gas mixture. The refrigerant
self-circulates inside the refrigerant circuit 102.
[0052] Inside the electronic component housing 202 a first gas
moving device, e.g. a first fan 206, is arranged and adapted to
circulate a gas, commonly air, inside the electronic component
housing 202. Outside the electronic component housing 202 a second
gas moving device, e.g. a second fan 208, is arranged and adapted
to blow ambient air over an outer surface area of the condenser
108. The condenser 108 and also the second fan 208 may be arranged
in a non-shown separate housing. Suitably such a separate housing
communicates with ambient environment. To save vertical space
inside the electronic component housing the evaporator 104 may be
arranged at an acute angle .alpha. from a horizontal line, e.g.
5-60 degrees. Also the condenser 108 may arranged at an acute
angle, the same as .alpha. or different from .alpha..
[0053] In use, the electronic components 204 inside the electronic
component housing 202 generate heat. Depending inter alia on
generated heat, construction of the electronic component housing
202 and on ambient conditions such as temperature, air movement
(e.g. wind) and precipitation (e.g. rain), the temperature inside
the electronic component housing 202 may increase to a level which
could harm the electronic components 204. The heat transfer
arrangement and primarily the evaporator 104 of the refrigerant
circuit 102 is arranged to cool the inside air of the electronic
component housing 202 to avoid such harmful temperature levels. A
suitable aim of example embodiments may be to keep the temperature
inside the electronic component housing 202 below +60 degrees
Celsius.
[0054] Under certain conditions the refrigerant self-circulates
inside the refrigerant circuit 102 as explained above with
reference to FIG. 1. By utilizing heat inside the electronic
component housing 202 for evaporating the refrigerant, the
temperature of the air inside the electronic component housing 202
will fall and may be used to cool the electronic components 204.
Inter alia to ensure proper cooling of the electronic components
204, the first fan 206 may circulate the air, as indicated by arrow
210, inside the electronic component housing 202 past the
evaporator 104 and the electronic components 204. Circulation in
another direction than indicated by arrow 210 is also possible. In
the condenser 108 the refrigerant in gas form will condense to
liquid form by emitting heat to the ambient environment. Transfer
of heat from the condenser 108 to the ambient environment may be
increased by switching on the second fan 208 to blow ambient air
over an outer surface area of the condenser 108, e.g. in the
direction indicated by arrow 212.
[0055] To avoid harming the electronic components 204, it is also
desirable to not allow the temperature inside the electronic
component housing 202 to fall below a certain temperature. A
suitable aim of example embodiments may be to keep the temperature
inside the electronic component housing 202 above +5 degrees
Celsius.
[0056] FIG. 3 illustrates schematically an electronic component
housing according to example embodiments. There are two heat
transfer arrangements, each comprising a separate refrigerant
circuit 102, 102', associated with the electronic component housing
202. Evaporators 104, 104' of the refrigerant circuits 102, 102'
are arranged adjacent each other inside the electronic component
housing 202. A circulating gas inside the electric component
housing 202 will be cooled in two steps as it flows first over an
outer surface of one evaporator 104 and then over an outer surface
of the other evaporator 104'. By this arrangement a higher
temperature efficiency is achieved and the circulating gas inside
the electronic component housing 202 will be cooled to a lower
temperature than if only one refrigerant circuit would be used. The
gas inside the electronic component housing 202 may be circulated
in any direction but the direction indicated by arrow 302 is
advantageous when condensers 108, 108', of the refrigerant circuits
102, 102' are arranged as shown in FIG. 3 and ambient air is blown
as indicated by arrow 304.
[0057] With reference to FIG. 4 an exemplary method for controlling
heat transfer from an electronic component housing is described.
The electronic component housing may for instance be a radio base
station, from which heat is to be transferred to an ambient
environment.
[0058] Ambient conditions and conditions inside an electronic
component housing are such that a refrigerant self-circulates 402
inside a refrigerant circuit of a heat transfer arrangement for
transferring heat from the electronic component housing to the
environment. A fan adapted to blow ambient air over a condenser of
the refrigerant circuit is controlled 404, e.g. speed controlled.
Temperature inside the electronic component housing is monitored
406. If the temperature is above a limit value, e.g. +10 degrees
Celsius, control of the second fan continues. If the temperature is
below the limit value, the second fan is stopped 408 and heat
transfer from the electronic component housing reduced. As ambient
temperature decreases, self-circulation in the refrigerant circuit
decreases further 410 due to the separate gas or separate gas
mixture displacing refrigerant in gas form from an inner heat
exchange surface of the condenser and heat exchange from the
electronic component housing to the environment by means of the
heat transfer arrangement is reduced to a minimum. The temperature
limit value inside the electronic component housing may suitably be
selected within the interval +5 to +20 degrees Celsius.
[0059] According to example embodiments, inside a refrigerant
circuit of a heat transfer arrangement there is a refrigerant and a
further separate gas or further separate gas mixture. The
refrigerant may be R134a and the separate gas may be nitrogen.
Alternatively, a separate gas mixture to be used may be air. R134a
is a name for 1,1,1,2-Tetrafluoroethane, it has the formula
CH.sub.2FCF.sub.3. The refrigerant and the separate gas or separate
gas mixture are present at a fixed weight ratio inside the
refrigerant circuit, i.e. the refrigerant circuit, during
manufacturing, is filled with a predetermined quantity of
refrigerant and a predetermined quantity of the separate gas or
separate gas mixture and then sealed. Once ready for installation,
e.g. in an electronic component housing, the refrigerant circuit
contents remain unaltered.
[0060] Having a refrigerant and a separate gas or separate gas
mixture inside the refrigerant circuit will give the refrigerant
circuit a different characteristic compared to if the refrigerant
circuit would be filled will refrigerant only. With the separate
gas or separate gas mixture, the cooling capacity of the
refrigerant circuit will depend on temperature: The cooling
capacity is high when the temperature is high and the cooling
capacity is low when the temperature is low. At a fixed weight
ratio of 3-40% of separate gas or separate gas mixture an
advantageous characteristic is achieved, in particular for heat
transfer arrangements for electronic component housings, e.g. radio
base stations. A weight ratio interval of further interest would be
separate gas or separate gas mixture at 5-25%.
[0061] Utilizing a heat transfer arrangement with a refrigerant
circuit where the refrigerant and the separate gas or separate gas
mixture weight ratio is within these intervals, the temperature
inside an electronic component housing may be kept within
favourable limits. In combination with gas moving devices, such as
the above exemplified first and second fans, the temperature inside
an electronic component housing is easily controlled.
[0062] The volume ratio between refrigerant in gas form and the
separate gas or separate gas mixture inside the refrigerant circuit
is dependent on the pressure inside the refrigerant circuit, which
in turn depends on the temperature inside the electronic component
housing and the ambient temperature.
[0063] The refrigerant exists inside the refrigerant circuit in
both liquid form and gas form. The separate gas or separate gas
mixture only exists in gas form inside the refrigerant circuit. A
high pressure inside the refrigerant circuit depends on more
refrigerant being in gas form than at a low pressure. The higher
the pressure inside the refrigerant circuit, the less volume the
separate gas or separate gas mixture will occupy inside the
refrigerant circuit. Conversely, as pressure is reduced inside the
refrigerant circuit, the separate gas or separate gas mixture
expands in comparison with refrigerant in gas form. Since the
separate gas or separate gas mixture is lighter than liquid
refrigerant the separate gas or separate gas mixture will expand
inside the condenser and displace refrigerant in gas form from the
condenser and an inner heat transfer surface thereof.
[0064] The gas, e.g. air, inside the electronic component housing
is circulated by the first fan, over the outer surface area of the
evaporator and towards the electronic components. The speed of the
first fan may suitably be controlled. Even though the first fan
could be stopped at low temperatures inside the electronic
component housing, it is suitable to maintain a minimum speed of
the first fan e.g. to avoid local heat build up at electronic
components.
[0065] In a first situation, when electronic components inside the
electronic component housing generate heat to such an extent that
the inside of the electronic component housing requires cooling,
the refrigerant self-circulates in the refrigerant circuit and the
second fan is controlled to blow air over the outer surface of the
condenser to improve heat transfer from the condenser to the
environment.
[0066] In a second situation, e.g. when ambient temperature has
fallen, a desired temperature may be maintained inside the
electronic component housing by means of the heat transfer
arrangement but without the aid of the second fan. The second fan
is stopped to decrease the heat transfer between the condenser and
the environment. The refrigerant still self-circulates in this
situation and a desired temperature is maintained inside the
electronic component housing.
[0067] An additional or separate criterion for stopping the second
fan may be when a temperature inside the electronic component
housing is in the interval of +5 to +20 degrees Celsius.
[0068] In a third situation, e.g. when ambient temperature has
fallen further, a desired temperature may be maintained inside the
electronic component housing without the aid of the heat transfer
arrangement, heat transfer from the electronic component housing to
the environment is reduced to a minimum due to the separate gas or
separate gas mixture having expanded to such an extent inside the
condenser that self-circulation of the refrigerant has been reduced
to a minimum.
[0069] Example embodiments may be combined as understood by a
person skilled in the art. It is also understood by those skilled
in the art that first and second fans may be any other gas moving
devices suitable for producing a flow of gas over an outer surface
of an evaporator or condenser. A heating apparatus may be arranged
to heat the inside of the electronic component housing to avoid too
low temperatures inside the electronic component housing even when
the heat transfer from the electronic component housing is minimal.
Heating could become necessary under certain ambient
conditions.
[0070] Therefore, it is to be understood that the foregoing is
illustrative of various example embodiments and is not to be
limited to the specific embodiments disclosed and that
modifications to the disclosed embodiments, combinations of
features of disclosed embodiments as well as other embodiments are
intended to be included within the scope of the appended
claims.
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