Note: Descriptions are shown in the official language in which they were submitted.
CA 02872717 2014-10-22
REFRIGERATING CAPACITY CONTROL DEVICE, A TESTING APPARATUS AND
A REFRIGERATING CONTROL METHOD USING THE DEVICE
[1] FIELD OF THE INVENTION
[2] This invention is related to a hot-gas refrigerating capacity control
device for
s accurate control of refrigerating capacity in climatic and environmental
testing
equipment. Particularly, this invention makes it possible for the
refrigerating system to
operate and maintain a temperature close to or higher than ambient temperature
with
less or no accessory heating. It can decrease the power consumption from
additional
heating, increase energy efficiency ratio and even eliminate the use of a
heater. The
lo control device features in simpler structure and lower energy
consumption. It can be
used as an important means of accurate temperature control for climatic and
environmental testing equipment. Moreover, the invention also relates to a
testing
apparatus incorporating the refrigerating capacity control device and a
control method
used in such control device.
15 [3] BACKGROUND OF THE INVENTION
[4] Climatic and environmental testing equipment (such as liquid baths and
circulators,
climatic and environmental testing chambers and refrigerated incubators etc.)
has
wide application in manufacturing, scientific research for laboratory and
process
control, in the fields of pharmaceuticals, medical sanitary, biotechnology,
agriculture
20 and forestry, electronics and electrics, metrological inspection and
verification, civil
engineering and petroleum chemicals etc.
[5] The refrigerating device is one of the important indispensable assemblies
for
climatic and environmental testing equipment. Refrigerating device and
technologies
are applied in all testing equipment requiring low temperature (below ambient
25 temperature) or heat withdrawal during normal operation. For the
requirements of
accurate temperature control and the features of small quantity and
diversities for
application, the refrigerating capacity and energy saving control of climatic
and
CA 02872717 2014-10-22
environmental testing equipment have been an important subject but are
neglected
for long times. The temperature control for almost all climatic and
environmental
testing equipment incorporating refrigerating device are based on conventional
technology of continuous refrigeration and additional counter heating,
resulting in
increased electric current drawing and substantial energy waste.
[e] According to Fig.1, a traditional refrigerating device fundamentally
comprises a
compressor, a condenser, a throttling device and an evaporator. The use of
capillary
tube, thermal expansion valve and electronic expansion valve as a throttling
device
and an indispensable important part for the refrigerating device, is a sign
evidencing
the development course, from simple to automatic control, of refrigerating
technology.
In accurate control of refrigerating capacity, the development and application
of
electronic expansion valve has been playing a more and more important role.
[7] For refrigerating capacity control, the modern technologies of inverter
compressor,
electronic expansion valve and heat pump have been extensively used in
household
is or commercial electrical appliances. The inverter compressor and electronic
expansion valve as a whole are usually incorporated in the refrigerating
device for
refrigerating capacity control. The success in the application of such
technology is
based on specific inverter compressor, sophisticated sensing and calculation
of the
superheat. Without extensive marketing survey, sufficient budget for
engineering and
zo manufacturing investment, it is difficult to apply this technology in
general purpose
appliance and equipment. Compared to traditional resistance electric heating,
the
heat pump technology, incorporated with a 4-way valve for switchover of the
condenser and evaporator for heating and refrigerating, has the advantage of
extremely higher energy efficiency ratio and energy saving property.
Nevertheless, the
as refrigerating capacity control needs to be depended on the technologies
of inverter
compressor and electronic expansion valve.
[8] Currently, the electronic expansion valve has been extensively used in the
fields of
household electrical appliances and commercial refrigeration. It is
specifically used as
a throttling device to match the system requirements of inverter compressor
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refrigeration. Its key function is to control the degree of Superheat at the
evaporator
outlet. The electronic expansion valve is normally located between the
condenser
outlet and the evaporator inlet. Based on requirement for the degree of
superheat at
the evaporator outlet, the electronic expansion valve is regulated to open,
close or
s .. maintain at certain degree of opening to respond changing temperature and
heat load
for possible maximum refrigerating capacity. Because of the specific purpose
of
superheat control, the electronic expansion valve as throttling device has the
limitation
for optimized refrigerating capacity and precise temperature control. To
acquire an
accurate superheat value, it is required that evaporating temperatures and/or
io .. refrigerant pressures at beginning and ending portions of the evaporator
be measured.
Therefore, the degree of complexity and reliability for the control circuit
and software
algorithm becomes critical to the success of the system. Without optimistic
prospect of
industrialization and sufficient budget for engineering and manufacturing
investment
for mass production, it is difficult to afford the expensive cost for a
sophisticated and
15 .. reliable system. In the mean time, the application temperature range of
traditional
electronic expansion valve is limited between ambient temperature and -40 C,
while
the requirements for application in climatic and environmental testing
equipment are
extended down to -90 C and up to +300 C. With the status of small quantity and
diversity in application, it is difficult to apply the electronic expansion
valve in climatic
20 and environmental testing equipment for precise temperature and
refrigerating
capacity control, in the traditional way as in household and commercial
appliances.
[9] The hot-gas bypassing refrigeration is characterized in an additional hot
gas
bypassing channel into a traditional refrigerating device to achieve simple
normal
cooling and hot-gas bypassing heating. Its basic working principle is to close
the
25 .. hot-gas valve for maximum refrigerating capacity when cooling is
expected. When the
refrigerating capacity needs to be decreased or heating is desired, the hot-
gas valve
is opened and the hot refrigerant vapor from the discharge outlet of the
compressor is
directly bypassed into the evaporator without cooled by the condenser. As a
result, the
refrigerating capacity is restrained, the cooling is limited and even heating
is possible.
30 When constant temperature is required, the hot-gas valve is opened and
closed at
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certain frequency to achieve regulation of refrigerating capacity and constant
temperature, Although it is popular knowledge, the current hot-gas bypassing
technology has the disadvantages of:
[10] (1) Due to the restrain from the service life of a solenoid valve, the
operation
s interval of
the hot gas bypassing should be limited to certain extent. As a result, the
control precision of refrigerating capacity is also limited;
[11] (2) With the solenoid valve remaining opened for a long time under
continuous
heating condition, the discharge pressure of the compressor will decrease
gradually.
As a result, the refrigerating device based on hot-gas bypassing can only
achieve
lo limited
heating or even no heating. It is actually difficult to maintain an operating
temperature close to or higher than ambient;
[12] (3) With the function and operation of a solenoid valve, it emits
unfavorable
noise including that of valve operation and that of hot-gas flow; and
[13] (4) The stress of pressure impact resulting from operating of the
solenoid valve
15 creates
additional fatigue and reduces the service life of related refrigerating parts
or
components, including the solenoid valve itself.
[14] SUMMARY OF THE INVENTION
[15] This invention is intended to provide:
a refrigerating capacity control device to address the technical difficulties
in the control
20 of
refrigerating capacity, the regulation of temperature and its excessive energy
consuming in a refrigerated climatic and environmental testing equipment;
[16] a testing apparatus incorporating the refrigerating capacity control
device; and
[17] a control method used in the refrigerating capacity control device.
[18] The technical solution of the invention to address relevant technical
difficulties is:
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[19] A refrigerating capacity control device comprises a controller, a
pressure
regulating valve, a throttling device, a refrigerating device, a control panel
for driving a
hot-gas valve, and a hot-gas valve. The controller is connected to the hot-gas
valve
through the control panel for driving a hot-gas valve; the pressure regulating
valve is
located between a discharge outlet of the compressor of the refrigerating
device and
an inlet of the condenser; the throttling device is installed between an
outlet of the
condenser of the refrigerating device and an inlet of the evaporator; the hot-
gas valve,
having one-end installed on a pipeline between the discharge outlet of the
compressor
and a front end of the pressure regulating valve, and another end installed on
a
pipeline between a location downstream from the throttling device and the
inlet of the
evaporator.
[20]The refrigerating capacity control device, wherein the throttling device
is a thermal
expansion valve.
[21] The refrigerating capacity control device, wherein the throttling device
is a
capillary tube.
[22] The refrigerating capacity control device, wherein the throttling device
is an
electronic expansion valve.
[23] The refrigerating capacity control device, wherein the hot-gas valve is a
continuously variable, electrically operated valve or an on/off solenoid
valve.
[24] The refrigerating capacity control device, wherein the refrigerating
device
comprises a compressor, a condenser and an evaporator connected sequentially
by
pipelines.
[25] A testing apparatus incorporating the refrigerating capacity control
device, the
testing apparatus comprising:
a refrigerating capacity control device, a chamber or bath requiring
temperature
control and a temperature sensor;
an evaporator of the refrigerating capacity control device and the temperature
sensor are installed within the chamber or bath requiring temperature control;
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the temperature sensor is connected to a controller of the refrigerating
capacity
control device.
[26] A refrigerating capacity control method comprising:
installing a pressure regulating valve between the compressor and condenser of
a
traditional refrigerating device; installing one-end of a hot-gas valve on a
pipeline between an discharge outlet of the compressor and a front end of the
pressure regulating valve, and another end of the hot-gas valve on a pipeline
between a location downstream from the throttling device and an inlet of the
evaporator;
connecting the hot-gas valve to the controller by using a control panel for
driving a
hot-gas valve;
installing a throttling device between an outlet of the condenser of the
refrigerating
device and the inlet of the evaporator;
wherein the pressure regulating valve is used to maintain a stable discharge
pressure and a hot-gas temperature to avoid the discharge pressure being
affected by the switching-on or switching-off of the hot-gas valve;
wherein the throttling device is used to independently control the evaporating
temperature and degree of superheat; and
wherein the hot-gas valve releases directly the hot vapor from the discharge
outlet
of the compressor according to its opening setting or frequency. the pressure
regulating valve reduces the output of a refrigerating system by restricting
the
refrigerant entering the condenser, and thereby heating and refrigerating
capacity is effectively controlled and the temperature is precisely maintained
at a set value.
[27] The hot-gas valve is a continuously variable, electrically operated valve
or an
on/off solenoid valve.
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128) This invention has the beneficial effects in that traditional electronic
valve or
solenoid valve are used as hot-gas bypassing valve, combined with a
traditional
throttling device to constitute a refrigerating device. As a result, the
accurate control
for refrigerating capacity between 300W-16kW or higher, and precise
temperature
control for refrigerating device operating between -90-4-20 C, are readily
achieved,
even when the refrigerating device is expected to work under operating
temperature
lower than -30 C and, even when the orifice of the hot-gas valve is relatively
bigger.
As one of the most critical control assemblies of the refrigerating device for
climatic
and environmental testing equipment, it eliminates the defects that the
refrigerating
io capacity cannot be controlled continuously with traditional thermal
expansion valve or
capillary tube, and that the electronic expansion valves available for
commercial
appliances are featured with excessive refrigerating capacity and lower
control
precision.
[29] BRIEF DESCRIPTION OF THE DRAWINGS
[30] Fig. 1 shows the structural diagram of a traditional refrigerating
device.
[31] Fig. 2 shows the structural diagram of a testing apparatus utilizing the
refrigerating capacity control device of the invention, wherein
1. Controller; 2. Compressor; 3. Condenser fan; 4. Pressure regulating device;
5.
Condenser; 6. Throttling device; 7. Evaporator; 8. Circulating fan or pump; 9.
Chamber or bath requiring temperature control; 10. Temperature sensor; 11.
Electronic expansion valve; 12. Refrigerating pipeline; 13. The control panel
for driving
an electronic expansion valve.
[33] DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE
INVENTION
[34] Operation of the refrigerating capacity control device can be understood
by
reference first to a traditional refrigerating device as shown in Fig 1 and
then by
reference to the current invention as shown in Fig 2. A refrigerating capacity
control
7
=
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device comprises a controller (1), a compressor (2), a condenser fan (3) , a
pressure
regulating valve (4), a condenser (5) , a throttling device (6), an evaporator
(7),
circulating fan or pump (8), chamber or bath (9) requiring temperature
control,
temperature sensor (10), an electronic expansion valve for hot-gas bypassing
(11),
refrigerating pipelines (12) and a control panel (13) for driving an
electronic expansion
valve. VVherein, the compressor (2), the condenser (5), the throttling device
(6), and
the evaporator (7) connected sequentially by refrigerating pipeline (12),
condenser fan
(3) for the condenser (5) , chamber or bath (9) requiring temperature control
and
circulating fan or pump (8) for forced convection are parts for a traditional
refrigerating
device. Wherein, the electronic expansion valve (11) functions as the hot-gas
bypassing valve (11), connected in parallel, having one-end installed on a
pipeline
between the discharge outlet of the compressor (2) and a front end of the
pressure
regulating valve (4), and another end installed on a pipeline between a
location
downstream from the throttling device (6) and the inlet of the evaporator (7),
The control panel (13) for driving an electronic expansion valve accepts
driving
signals such as voltage or current from the controller (1) and directly
regulates the
opening, closing and opening degree of the hot-gas bypassing valve (11). The
controller (1) is connected to the compressor (2), temperature sensor (10),
condenser
fan (3), circulating fan or pump (8) and control panel (13) for driving an
electronic
expansion valve for input and output control. The temperature sensor (10) and
evaporator (7) are installed within the chamber or bath (9) requiring
temperature
control for heating, cooling and maintaining the temperature.
[35] The controller (1) can start or stop the operation of compressor (2),
condenser fan
(3) and circulating fan or pump (8). With the temperature sensor (10), the
controller (1)
can detect the temperature of the air or liquid in the chamber or bath (9)
requiring
temperature control. Compared to the set temperature of the controller (1), in
case of
a higher actual temperature, the electronic expansion valve (11) tends to be
closed,
while in case of lower actual temperature, the electronic expansion valve (11)
tends to
be opened. With the actual temperature becomes stabilized, the opening degree
of
the electronic expansion valve (11) tends to be constant.
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[36] The compressor (2), condenser (5), throttling device (6) and evaporator
(7) are
fundamental components of a traditional refrigerating device. The function of
the
compressor (2) is to suck the refrigerant vapor of low pressure/normal
temperature
from the evaporator (7), and pressurize it to deliver high pressure/high
temperature
vapor. The models of the compressor (2) include types of reciprocating,
rotary, scroll
and screw. The function of the condenser (5) is to condense high pressure/high
temperature refrigerant vapor, as cooled by condenser fan (3) or other liquid
coolant,
to become high pressure/normal temperature refrigerant liquid. The condenser
(5) can
be any type of fin tube, sleeve, shell tube, plate and etc. The function of
the throttling
io device (6) is to lower the pressure of the refrigerant liquid to produce
low temperature
when the refrigerant boils and evaporates with its pressure dropping. In the
practical
application, the throttling device (0) can be capillary tube, thermal
expansion valve,
electronic expansion valve or any available conventional expansion device. The
function of the evaporator (7) is to provide a space where the liquid
refrigerant boils
is and evaporates. During the evaporating or boiling process of the liquid
refrigerant, the
evaporator (7) keeps absorbing the heat from ambient, presenting cooling
effect of the
refrigeration. The critical aspect of the design for the refrigerating system
is that liquid
refrigerant keeps evaporating completely within the evaporator (7) to the
extent for
maximum superheat of 5 C. As a result, when the refrigerant vapor leaves the
20 evaporator (7), its temperature is close to the operating temperature of
the chamber or
bath (9) requiring temperature control or the ambient temperature where the
equipment is installed.
[37) The pressure regulating valve (4) is a special automatic control device
to
maintain discharge temperature of the compressor (2). The pressure regulating
valve
25 (4) is not an essential component for traditional refrigerating device,
but is a specific
component particular to this invention. The mechanism of pressure regulating
valve (4)
is, with the increase of the discharge pressure, it tends to open allowing
more
refrigerant flow. In other words, when the pressure reaches the set value, the
pressure
regulating valve (4) starts to open. The operation of the pressure regulating
valve (4)
30 is dependent on the discharge pressure of the compressor (2), and has
nothing to do
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with the pressure at the outlet of pressure regulating valve (4) or the
pressure in the
condenser (5). In this case, the affection on the discharge pressure resulting
from
operation of the electronic expansion valve (11) can be minimized. As a
result, stable
discharge pressure and hot-gas bypassing temperature can be guaranteed. Even
when the electronic expansion valve (11) keeps opening continuously, the
constant
discharge pressure can guarantee stable heat source to ensure sufficient
heating
temperature and precise temperature control. In other words, without the
pressure
regulating valve (4), it is not possible for the refrigerating device to
achieve energy
regulation as expected. When the temperature in the chamber or bath (9)
requiring
io temperature control increases, the electronic expansion valve (11) will be
closed to
achieve normal refrigeration. When the temperature in the chamber or bath (9)
requiring temperature control becomes lower, the electronic expansion valve
(11) will
be opened. Without the pressure regulating valve (4), the discharge pressure
will
decrease gradually with the electronic expansion valve (11) opened and the
heating in
progress, Although the electronic expansion valve (11) is kept opened for
heating, the
heating temperature is not high enough and the heating energy is limited. At
the same
time, the refrigeration is still possible through the normal function of the
condenser (5)
and throttling device (6). As a result, under particular conditions, the
heating by
hot-gas bypassing cannot be expected, not to mention the regulation of the
zo refrigerating capacity. In addition, the incorporation of the pressure
regulating valve (4)
can increase the heating temperature from the electronic expansion valve (11)
and
hot-gas bypassing, and limit the refrigerating capacity of the throttling
device (6) as
well. The increased temperature and limited cooling are the critical aspects
for the
regulation of refrigerating capacity and hot-gas bypassing heating.
[38] The chamber or bath (9) requiring temperature control is the most popular
component associated with the refrigerating device in climatic and
environmental
testing equipment. In order to meet the requirements of temperature range and
operating conditions of climatic and environmental testing equipment, the
chamber or
bath (9) requiring temperature control is usually composed of interior chamber
or bath
tank, enclosure and insulating materials. For easy operation and access, the
chamber
CA 02872717 2014-10-22
and bath (9) is also equipped with a door or cover. In case the operating
temperature
is far beyond the ambient temperature, the door or cover must also be
insulated,
together with the sealing gasket or cushion.
(39] The temperature sensor (10) is used to detect the temperature of the air
or liquid
in the chamber or bath (9) requiring temperature control. The position of
temperature
sensor (10) and the operation of circulating fan or pump (8) are important and
will
severely affect the truth of sensed temperature, and as a result affect the
operation of
the electronic expansion valve (11) for hot-gas bypassing.
(40] The electronic expansion valve (11) and control panel (13) for driving an
ao electronic expansion valve are specific components particular to the
preferred
embodiment of this invention. The control panel (13) for driving an electronic
expansion valve is an automatic assembly with its opening, closing and degree
of
opening regulated by and proportional to the input of voltage or current. The
control
panel (13) for driving an electronic expansion valve accepts driving signals
such as
is voltage or current from the controller (1) and directly regulates the
opening, closing
and opening degree of the hot-gas bypassing valve (11). The output of the
control
panel (13) shall be compatible to the driving required by the electronic
expansion
valve (11). Usually, when the control panel (13) receives an input voltage of
OV or
current of 4mA, the electronic expansion valve (11) shall be fully closed.
While the
20 control panel (13) receives an input voltage of 5V or current of 20mA,
the electronic
expansion valve (11) shall be fully opened. When the input signal ranges
between the
maximum and minimum values, the position. or degree of the opening for the
electronic expansion valve (11) shall be linearly proportional to the input
level.
Therefore, in case the detected temperature is higher and the output voltage
or
25 current of the controller (1) becomes smaller, the opening degree of the
electronic
expansion valve (11) will become smaller. As a result, the refrigerating
capacity is
increased and the temperature comes down accordingly. Contrary, in case the
detected temperature is lower and the output voltage or current of the
controller (1)
becomes bigger, the opening degree of the electronic expansion valve (11) will
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CA 02872717 2014-10-22
become larger. As a result, the refrigerating capacity is decreased and the
temperature goes up accordingly. At the time that the detected temperature
becomes
stabilized, the output voltage or current of the controller (1) is kept
unchanged, and the
opening degree of the electronic expansion device (11) is kept constant.
One end of the electronic expansion valve (11) is installed to a pipeline
between the
discharge outlet of the compressor (2) and a front end of the pressure
regulating valve
(4), and another end is installed on a pipeline between a location downstream
from
the throttling device (6) and the inlet of the evaporator (7). A thermal
expansion valve
is used to control the evaporating temperature and regulate degree of
superheat
independently. With the temperature close to the set value, the controller (1)
will send
a signal to control the electronic expansion valve (11) to release directly
the hot vapor
from the discharge outlet of the compressor (2) according to its opening
setting. The
pressure regulating valve (4) reduces the output of the refrigerating system
by
restricting the refrigerant entering the condenser (5), and thereby heating
and
refrigerating capacity is effectively controlled, and the temperature is
precisely
maintained at a set value. The electronic expansion valve (11) for the above
mentioned hot-gas valve can be a type of continuously variable flow valve. A
solenoid
valve can also be used as hot-gas valve if cost reduction becomes more
significant
than the control precision of temperature and refrigerating capacity.
