U.S. patent application number 10/208242 was filed with the patent office on 2004-02-05 for method and apparatus for moving air through a heat exchanger.
This patent application is currently assigned to Thermo King Corporation. Invention is credited to Shaw, John J., VanderWoude, David J., Waldschmidt, John E..
Application Number | 20040020228 10/208242 |
Document ID | / |
Family ID | 30443673 |
Filed Date | 2004-02-05 |
United States Patent
Application |
20040020228 |
Kind Code |
A1 |
Waldschmidt, John E. ; et
al. |
February 5, 2004 |
METHOD AND APPARATUS FOR MOVING AIR THROUGH A HEAT EXCHANGER
Abstract
A transport temperature control apparatus includes a
refrigeration circuit and a heat exchanger having an air inlet and
an air outlet in fluid communication with a conditioned space. An
evaporator coil extends through the heat exchanger between the
inlet and air outlet and is fluidly connected to the refrigeration
circuit. A divider defines a first portion of the evaporator coil
and a second portion of the evaporator coil. A first fan is housed
in the heat exchanger and is adjacent the first portion. The first
fan has a first operating condition for directing air across the
evaporator coil in a first direction and a first non-operating
condition. A second fan is housed in the heat exchanger and is
adjacent the second portion. The second fan has a second operating
condition for directing air across the evaporator coil in a second
direction and a second non-operating condition.
Inventors: |
Waldschmidt, John E.; (New
Market, MN) ; Shaw, John J.; (Savage, MN) ;
VanderWoude, David J.; (Farmington, MN) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH LLP
3773 CORPORATE PARKWAY
SUITE 360
CENTER VALLEY
PA
18034-8217
US
|
Assignee: |
Thermo King Corporation
Minneapolis
MN
|
Family ID: |
30443673 |
Appl. No.: |
10/208242 |
Filed: |
July 30, 2002 |
Current U.S.
Class: |
62/234 ;
62/276 |
Current CPC
Class: |
F25D 19/02 20130101;
F25D 21/06 20130101; F25D 2317/0665 20130101; B60H 1/00014
20130101; B60H 2001/00961 20190501; F25B 2600/112 20130101; F25D
21/006 20130101; F25D 2317/0655 20130101 |
Class at
Publication: |
62/234 ;
62/276 |
International
Class: |
F25D 021/00; F25D
021/06 |
Claims
What is claimed is:
1. A transport temperature control apparatus operable in a cooling
mode and a defrost mode, the apparatus comprising: a refrigeration
circuit; a heat exchanger having an air inlet and an air outlet,
the air inlet and the air outlet being in fluid communication with
a conditioned space; an evaporator coil extending through the heat
exchanger between the air inlet and the air outlet and being
fluidly connected to the refrigeration circuit; a divider
substantially perpendicular to the evaporator coil, the divider
defining a first portion of the evaporator coil and a second
portion of the evaporator coil; a first fan housed in the heat
exchanger and being positioned adjacent the first portion of the
evaporator coil, the first fan having a first operating condition
for directing air across the evaporator coil in a first direction
and a first non-operating condition; and a second fan housed in the
heat exchanger and being positioned adjacent the second portion of
the evaporator coil, the second fan having a second operating
condition for directing air across the evaporator coil in a second
direction and a second non-operating condition, the second
direction being opposite the first direction.
2. The transport temperature control apparatus of claim 1, further
comprising a damper positioned in the air discharge for selectively
preventing air from flowing through the air outlet.
3. The transport temperature control apparatus of claim 1, further
comprising a heating element positioned in the heat exchanger.
4. The transport temperature control apparatus of claim 3, wherein
the heating element is an electric heater.
5. The transport temperature control apparatus of claim 3, wherein
the heating element is a heating coil.
6. The transport temperature control apparatus of claim 1, further
comprising a controller in electrical communication with the first
fan and the second fan, the controller alternately operating the
first fan in the first operating condition and the first
non-operating condition and the second fan in the second operating
condition and the second non-operating condition.
7. The transport temperature control apparatus of claim 6, wherein
the controller operates the first fan in the first operating
condition for a first predetermined time and the second fan in the
second non-operating condition for the predetermined time and then
operates the second fan in the second operating condition for a
second predetermined time and the first fan in the first
non-operating condition for the second predetermined time.
8. The transport temperature control apparatus of claim 1, wherein
the first and second fans alternately direct air in the first
direction and the second direction.
9. The transport temperature control apparatus of claim 1, further
comprising a first flow path and a second flow path, the first flow
path extending from the first fan to the first portion of the
evaporator coil and then across the second portion of the
evaporator coil, the second flow path extending from the second fan
to the second portion of the evaporator coil and then across the
first portion of the evaporator coil, and wherein in the first
operating condition the first fan directs air along the first flow
path and in the second operating condition the second fan directs
air along the second flow path.
10. The transport temperature control apparatus of claim 1, further
comprising: a second divider coupled to the evaporator coil and
being substantially parallel to the first divider, the first and
second dividers defining the second portion of the evaporator coil
and the second divider defining a third section of the evaporator
coil; and a third fan housed in the heat exchanger and being
positioned adjacent the third portion of the evaporator coil, the
third fan having a third operating condition for directing air
across the evaporator coil and a third non-operating condition.
11. A method of conditioning air in a conditioned space with a
transport temperature control apparatus, the temperature control
apparatus including a heat exchanger having an air inlet and an air
discharge, an evaporator coil extending through the heat exchanger
between the air inlet and the air discharge, a divider coupled to
the evaporator coil and defining a first portion of the evaporator
coil and a second portion of the evaporator coil, a first fan
adjacent the first portion, and a second fan adjacent the second
portion, the method comprising: operating the temperature control
apparatus in a cooling mode, the cooling mode including: directing
air into the heat exchanger through the inlet with the first fan
and the second fan; transferring heat from the air to the
evaporator coil; and directing air out of the heat exchanger
through the discharge with the first fan and the second fan; and
operating the temperature control apparatus in a defrost mode, the
defrost mode including: activating the first fan and deactivating
the second fan, the first fan directing air in a first direction
across the first portion and then across the second portion;
activating the second fan and deactivating the first fan, the
second fan directing air in a second direction across the first
portion and then across the second portion, the second direction
being opposite the first direction; and heating air in the heat
exchanger with a heating element positioned in the heat
exchanger.
12. The method of claim 11, wherein the temperature control
apparatus includes a damper positioned in the air discharge, the
damper having an open position and a closed position, the method
further comprising moving the damper to the closed position during
operation in the defrost mode.
13. The method of claim 11, wherein the heating element is an
electric heater.
14. The method of claim 11, wherein the heating element is a
heating coil.
15. The method of claim 11, wherein the temperature control
apparatus includes a controller in electrical communication with
the first fan and the second fan, the controller alternately
operating the temperature control apparatus in the defrost mode and
the cooling mode.
16. The method of claim 15, wherein the controller activates the
first fan for a first predetermined time and deactivates the second
fan for the predetermined time and then activates the second fan
for a second predetermined time and deactivates the first fan for
the second predetermined time.
17. The transport temperature control apparatus of claim 1, wherein
the temperature control apparatus includes a second divider coupled
to the evaporator coil and being substantially parallel to the
first divider, the first and second dividers defining the second
portion of the evaporator coil and the second divider defining a
third section of the evaporator coil and a third fan housed in the
heat exchanger and being positioned adjacent the third portion of
the evaporator coil, and wherein operating in the defrost mode
includes alternately cycling the third fan on and off.
18. A method of conditioning air in a conditioned space with a
temperature control apparatus, the temperature control apparatus
including a heat exchanger having an inlet and an outlet, an
evaporator coil extending through the heat exchanger between the
inlet and the outlet, a divider coupled to the evaporator coil and
defining a first portion of the evaporator coil and a second
portion of the evaporator coil, a first fan adjacent the first
portion, and a second fan adjacent the second portion, the method
comprising: initiating a defrost mode; heating air in the heat
exchanger; preventing air from exiting the air outlet; activating
the first fan; deactivating the second fan blowing air with the
first fan along a first flow path, the first flow path extending
across the first portion and then across the second portion;
deactivating the first fan; activating the second fan; and blowing
air with the second fan along a second flow path, the second flow
path extending across the second portion and then across the first
portion.
19. The method of claim 18, wherein the temperature control
apparatus includes a damper positioned adjacent the discharge and
wherein preventing air from exiting the air outlet includes closing
the outlet with the damper.
20. The method of claim 18, wherein the temperature control
apparatus includes a heating element and wherein heating air in the
heat exchanger includes blowing air across the heating element.
21. The method of claim 18, wherein heating air in the heat
exchanger includes directing a warm fluid through the evaporator
coil.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to refrigeration and
air-conditioning systems, and more particularly, to a method and an
apparatus for controlling the flow of air through a transport
temperature control apparatus.
BACKGROUND OF THE INVENTION
[0002] Transport temperature control apparatuses are commonly
mounted on refrigerated containers, refrigerated straight trucks,
refrigerated tractor-trailer combinations, and the like to maintain
cargo, such as foods, beverages, plants, flowers, and the like, at
a desired set point temperature. In other applications, temperature
control apparatuses can be used to condition air in a conditioned
space to improve human comfort, such as for example, in buses and
passenger trains.
[0003] Typically, conventional temperature control apparatuses
include a heat exchanger, which extends into the conditioned space.
An evaporator coil extends through the heat exchanger and is
fluidly connected to a refrigeration circuit. In the refrigeration
circuit, a refrigerant, such as for example, a chlorofluorocarbon
(CFC) or a cryogen, is cooled, compressed, and/or stored. Liquid
refrigerant from the refrigerant cycle is forced into an inlet in
the evaporator coil. Warm conditioned space air is then drawn into
the heat exchanger through an air inlet and is blown across the
evaporator coil by a fan or blower. The relatively warm conditioned
space air contacts the relatively cool evaporator coil and is
cooled thereby before being forced back into the conditioned space
via a discharge in the heat exchanger. The refrigerant is then
directed out of the evaporator coil and may be re-compressed and
re-cooled in the refrigeration circuit to be recycled through the
evaporator coil.
[0004] Occasionally, water vapor from the conditioned space can be
separated from the air and can condense on the evaporator coil,
forming frost. To minimize the formation of frost on the evaporator
coil and to remove frost from the evaporator coil, conventional
temperature control apparatuses periodically operate in a defrost
mode. In the defrost mode, hot gases are directed through the
evaporator coil to heat the coil and melt any frost that may have
accumulated on the coil. Alternatively, electric heating elements
can be used to heat the air in the heat exchanger. To prevent
unnecessary heating of the conditioned space, air is not directed
through the heat exchanger during operation in the defrost mode. In
defrost, airflow is typically restricted using a damper to close
the discharge while the fans continue to operate.
SUMMARY OF THE INVENTION
[0005] According to the present invention, a transport temperature
control apparatus operable in a cooling mode and a defrost mode
includes a refrigeration circuit and a heat exchanger having an air
inlet and an air outlet. The air inlet and the air outlet are in
fluid communication with a conditioned space. An evaporator coil
extends through the heat exchanger between the air inlet and the
air outlet and is fluidly connected to the refrigeration circuit. A
divider is positioned substantially perpendicular to the evaporator
coil and defines a first portion of the evaporator coil and a
second portion of the evaporator coil. A first fan is housed in the
heat exchanger and is positioned adjacent the first portion of the
evaporator coil. The first fan has a first operating condition for
directing air across the evaporator coil in a first direction and a
first non-operating condition. A second fan is housed in the heat
exchanger and is positioned adjacent the second portion of the
evaporator coil. The second fan has a second operating condition
for directing air across the evaporator coil in a second direction
and a second non-operating condition. The second direction is
opposite the first direction.
[0006] In some embodiments, a damper is positioned in the air
discharge for selectively preventing air from flowing through the
air outlet and a heating element is positioned in the heat
exchanger. The heating element can include an electric heater
and/or a heating coil.
[0007] A controller is in electrical communication with the first
fan and the second fan. The controller alternately operates the
first fan in the first operating condition and the first
non-operating condition and the second fan in the second operating
condition and the second non-operating condition. The controller
operates the first fan in the first operating condition for a first
predetermined time and the second fan in the second non-operating
condition for the predetermined time and then operates the second
fan in the second operating condition for a second predetermined
time and the first fan in the first non-operating condition for the
second predetermined time. Also, the first and second fans
alternately direct air in the first direction and the second
direction.
[0008] The present invention also includes a method of conditioning
air in a conditioned space with the transport temperature control
apparatus. The method includes operating the temperature control
apparatus in a cooling mode. The cooling mode includes directing
air into the heat exchanger through the inlet with the first and
second fans, transferring heat from the air to the evaporator coil
and directing air out of the heat exchanger through the discharge
with the first and second fans. The method also includes operating
the temperature control apparatus in a defrost mode. The defrost
mode includes activating the first fan and deactivating the second
fan. The first fan directs air in a first direction across the
first portion and then across the second portion. The defrost mode
further includes activating the second fan and deactivating the
first fan. The second fan directs air in a second direction across
the second portion and then across the first portion. Additionally,
the defrost mode includes heating air in the heat exchanger with a
heating element positioned in the heat exchanger.
[0009] Additional features and advantages of the invention will
become apparent to those skilled in the art upon consideration of
the following detailed description, claims, and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The present invention is further described with reference to
the accompanying drawings, which show preferred embodiments of the
present invention. However, it should be noted that the invention
as disclosed in the accompanying drawings is illustrated by way of
example only. The various elements and combinations of elements
described below and illustrated in the drawings can be arranged and
organized differently to result in embodiments which are still
within the spirit and scope of the present invention.
[0011] In the drawings, wherein like reference numerals indicate
like parts:
[0012] FIG. 1 is a side view, partially in section, of a vehicle
having a temperature control apparatus embodying the present
invention;
[0013] FIG. 2 is a side view of the temperature control apparatus
according to a first embodiment of the present invention;
[0014] FIG. 3 is a side view of the temperature control apparatus
according to a second embodiment of the present invention;
[0015] FIG. 4 is a side view of the temperature control apparatus
according to a third embodiment of the present invention; and
[0016] FIG. 5 is a left side view, partially in section, of a
vehicle having a temperature control apparatus according to a
fourth embodiment of the present invention.
DETAILED DESCRIPTION
[0017] FIG. 1 illustrates a transportation temperature control
apparatus 10 in accordance with the present invention. The
temperature control apparatus 10 is mounted on a trailer 12 having
a conditioned space 14. The trailer 12 is pulled by a tractor 16,
as is understood by those skilled in the art. In other
applications, the temperature control apparatus 10 can
alternatively be used on other vehicles, such as a straight truck,
a container, and the like. Similarly, the temperature control
apparatus 10 can be used to control the temperature in the
passenger space of a vehicle, such as for example, a bus or the
passenger compartment of a truck.
[0018] As used herein and in the claims, the term "conditioned
space" includes any space to be temperature and/or humidity
controlled, including transport and stationary applications for the
preservation of foods, beverages, plants, flowers, and other
perishables, maintenance of a proper atmosphere for the shipment of
industrial products, space conditioning for human comfort, and the
like.
[0019] Additionally, as used herein and in the claims, the term
"refrigerant" includes any conventional refrigerant including, but
not limited to, a chloroflourocarbon (CFCs), hydrocarbons, cryogens
(e.g., CO.sub.2 and N.sub.2), and other known refrigerants.
[0020] Referring now to FIG. 2, the refrigeration system 10
includes an outside housing 18, which is mounted outside the
trailer 12. The outside housing 18 includes a refrigeration circuit
20 that can include a compressor (not shown) and a condenser (not
shown), as is understood by those in the art. Alternatively, the
refrigeration circuit 20 can include a storage tank (not shown)
which houses a quantity of pressurized refrigerant, such as for
example, a cryogen.
[0021] The outside housing 18 also includes a prime mover 22, such
as for example, an electric generator, a fuel cell, a battery, an
alternator, diesel engine, or the like. The prime mover 22 supplies
power to the refrigeration system 10 and is electrically connected
to a controller 24, such as for example a microprocessor, which
controls operation of the temperature control unit 10. More
specifically, based, at least in part, upon data received by
sensors (not shown) distributed through the conditioned space 14,
the temperature control unit 10, and outside the trailer 12, the
controller 24 is programmed to shift between operation in cooling,
defrost, and heating modes to maintain a set point temperature
("SP") in the conditioned space 14.
[0022] A heat exchanger 28 extends into the conditioned space 14
and includes an air inlet 30 and an air outlet or discharge 32. Air
enters the heat exchanger 28 (as illustrated in the figures by
arrows 31) through the inlet 30 and travels across an evaporator
coil 34 before being returned to the conditioned space 14 via the
air outlet 32 (as illustrated in the figures by arrows 33). The
evaporator coil 34 is fluidly connected to the refrigerant circuit
20 via an evaporator coil inlet 38 and an evaporator coil outlet
40. During operation in the cooling mode, cold liquid refrigerant
is directed from of the refrigerant circuit 20 into the evaporator
coil 34 via the evaporator coil inlet 38. The relatively warm
conditioned space air warms the refrigerant, vaporizing the
refrigerant. The vaporized or mostly vaporized refrigerant is then
returned to the refrigerant circuit 20 to be recycled or
alternatively is exhausted to the atmosphere. Simultaneously, the
conditioned space air is cooled by contact with the relatively cool
evaporator coil 32. The cooled air is then returned to the
conditioned space 14 to maintain the desired set point temperature
SP.
[0023] The evaporator coil 34 includes an evaporator coil divider
42, which extends across the evaporator coil 34, dividing the
evaporator coil 34 into a first portion 44 and a second portion 46.
A first fan or blower 50 is located in the heat exchanger 28 and is
adjacent the first portion 44 of the evaporator coil 34. A second
fan or blower 52 is located in the heat exchanger 28 adjacent the
second portion 46 of the evaporator coil 34. The first and second
fans 50, 52 are in electrical communication with and are controlled
by the controller 24. In various embodiments, the first and second
fans 50, 52 can be belt driven, electrically driven, clutch
operated, or can be driven in any other conventional manner.
[0024] During operation in the cooling mode, the first and second
fans 50, 52 blow air across the evaporator coil 34 and back into
the conditioned space 14. Occasionally, during operation in the
cooling mode, water vapor from the conditioned space 14 can be
separated from the air and can condense on the evaporator coil 34,
forming frost. To minimize the formation of frost on the evaporator
coil 34 and to remove frost from the evaporator coil 34, the
controller 24 is programmed to periodically operate the temperature
control unit 10 in the defrost mode. The defrost mode can be
initiated in any number of different manners. For example, the
controller 24 can be programmed to initiate the defrost mode at
timed intervals (e.g., every two hours). Also, the controller 24
can be programmed to initiate the defrost mode if sensors
distributed throughout the temperature control apparatus 10 and the
conditioned space 14 supply data to the controller 24 indicating
that frost has accumulated on the evaporator coil 34 or that
conditions are right for the formation of frost. Alternatively or
in addition, an operator can manually initiate the defrost
mode.
[0025] In the defrost mode, a damper 58 is closed preventing air
from exiting the heat exchanger 28 through the air outlet 32.
Additionally, a first valve (not shown) in the refrigeration
circuit 20 is closed, preventing cold refrigerant from flowing into
the evaporator coil 34. A second valve (not shown) is opened,
causing a relatively warm fluid to flow through the evaporator coil
34. The second valve is fluidly connected to a heating circuit (not
shown), which extends into the outside housing 18. In some
applications, the heating circuit includes a heating element (not
shown), such as for example a pan heater, which heats refrigerant
from the refrigeration circuit 20 and then supplies the heated
refrigerant to the evaporator coil 34 for heating and defrosting.
In other applications, hot gas from the compressor (not shown) is
directed through the heating circuit to the evaporator coil 34. In
still other embodiments, other warm fluids, including but not
limited to, antifreeze can be directed through a coil (not shown)
adjacent to the evaporator coil 34.
[0026] As shown in FIG. 2, the heat exchanger 28 also includes an
electric heater 60, which is in electrical communication with and
is controlled by the controller 24. During operation in the heating
and defrost modes, the heater 60 is turned on to heat the air in
the heat exchanger 28.
[0027] Regardless of the source, the warm fluid enters the
evaporator coil 34 through the evaporator coil inlet 38 and exits
through the evaporator coil outlet 40. The warm refrigerant heats
the evaporator coil 34, melting the frost formed on the exterior of
the evaporator coil 34. However, the relatively cold evaporator
coil 34 cools the warm fluid as the warm fluid flows through the
evaporator coil 34 so that when the warm fluid exits the evaporator
coil 34, the warm fluid is significantly cooler than it was at the
evaporator coil inlet 38. Therefore, to ensure that the evaporator
coil 34 is defrosted evenly and as rapidly as possible, the
controller 34 is programmed to alternately activate and deactivate
the first and second fans 50, 52. More particularly, when the
defrost mode is initiated, the controller 24 shuts down the second
fan 52 and continues to operate the first fan 50. In this manner,
the first fan 50 blows air through the heat exchanger 28 along a
first flow path 64 (represented by arrows 64) across the first
portion 44 of the evaporator coil 34 and back across the second
portion 46 of the evaporator coil 34. The controller 24 continues
to operate the first fan 50 for a predetermined time period (e.g.,
two minutes). After the predetermined period of time, the
controller 24 shuts down the first fan 50 and starts the second fan
52, directing air through the heat exchanger 28 along a second flow
path 66 (represented by arrows 66). The second flow path 66 extends
across the second portion 46 of the evaporator coil 34 and then
across the first portion 44 of the evaporator coil 34. In this
manner, the second fan 52 directs heat from the substantially
defrosted first portion 44 onto the second portion 46, defrosting
the second portion 52. At the same time, warm refrigerant is
flowing through the second portion 46, further defrosting the
second portion 52.
[0028] The first and second fans 50, 52 also force air across the
heater 60 so that heat from the heater 60 is more evenly
distributed throughout the heat exchanger 28 to defrost the
evaporator coil 34. More specifically, when the first fan 50 is in
operation, heated air from the heater 60 is directed along the
first flow path 64 across the second portion 46 of the evaporator
coil 34 and then across the first portion 44 of the evaporator coil
34. Similarly, when the second fan 52 is in operation, heat from
the heater 60 is directed along the second flow path 66 across the
first portion 44 and then across the second portion 46.
Additionally, as mentioned above, the damper 58 is closed during
operation in the defrost mode so that the heater 60 does not heat
the conditioned space 14.
[0029] By periodically reversing the flow of air across the
evaporator coil 34, the evaporator coil 34 is defrosted relatively
evenly. More specifically, the evaporator coil inlet 38 and outlet
40 are defrosted at approximately the same rate. Additionally,
because the first and second fans 50, 52 are alternately operated,
rather than being operated simultaneously, the pressure inside the
heat exchanger 28 rises relatively slowly. Conversely, in
conventional heat exchangers 28, when two fans are in operation at
the same time, the pressure inside the heat exchanger 28 rises at a
much higher rate. Because the pressure inside and outside the heat
exchanger 28 is relatively similar in the present invention, very
little heated air leaks from the heat exchanger 28 into the
conditioned space 14 through cracks and gaps in the heat exchanger
housing. It is particularly desirable to prevent air from leaking
out of the heat exchanger 28 during operation in the defrost mode
because the relatively warm air in the heat exchanger 28 can heat
the conditioned space air, thereby reducing the efficiency of the
temperature control apparatus 10.
[0030] The controller 24 continues to cycle the first and second
fans 50, 52 on and off as long as defrost is required. Once the
controller 24 determines that defrost is no longer required or
after the defrost mode times out, the controller 24 is programmed
to close the second valve, stopping the flow of warm fluid into the
evaporator coil 34. The controller 24 is also programmed to open
the first valve, restoring the flow of refrigerant from the
refrigeration circuit 20. Additionally, the controller 24 opens the
damper 58 and shuts down the heater 60. The controller 24 then
resumes operation in the cooling mode as required by load
conditions and the ambient temperature.
[0031] FIG. 3 shows a temperature control apparatus 10 according to
a second embodiment of present invention, which is substantial
similar to the previously described embodiment. For simplicity,
like parts have been labeled with like reference numbers and only
differences between the first and second embodiments will be
described in detail hereafter.
[0032] In the second embodiment of the present invention, a heating
coil 72 extends through the heat exchanger 28 between the first and
second fans 50, 52 and the evaporator coil 34. However, in other
applications, the evaporator coil 34 can be positioned between the
first and second fans 50, 52 and the heating coil 72. The heating
coil 72 is fluidly connected to the heating circuit. During
operation in the defrost and heating modes, relatively warm fluid
from the heating circuit enters the heating coil 72 through a
heating coil inlet 74 and exits the heating coil 72 via a heating
coil outlet 76.
[0033] In the second embodiment, when the defrost mode is
initiated, the controller 24 shuts a valve (not shown) preventing
refrigerant from entering the evaporator coil 34 and closes the
damper 58 so that air does not leave the heat exchanger 28 via the
air outlet 32. The controller 24 also opens a second valve (not
shown) allowing warm fluid to enter the heating coil 72 via the
heating coil inlet 74. The first and second fans 50, 52 are then
cycled on and off for a predetermined time period as described
above with respect to the previous embodiment. When the first fan
50 is on and the second fan 52 is off, air is directed along the
first flow path 64. In the second embodiment, air traveling along
the first flow path 64 is blown across the heating coil 72, the
first portion 44 of the evaporator coil 34, the second portion 46
of the evaporator coil, and back across the heating coil 72. When
the first fan 50 is off and the second fan 52 is on, air is
directed along the second flow path 66. In the second embodiment,
air traveling along the second flow path 64 is blown across the
heating coil 72, the second portion 46 of the evaporator coil 34,
the first portion 44 of the evaporator coil 34, and back across the
heating coil 72.
[0034] When defrost is no longer required or when the defrost mode
times out, the controller 24 shuts the second valve, preventing
warm fluid from entering the heating coil 72. The controller 24
also opens the first valve, reconnecting the evaporator coil 34 to
the refrigeration circuit 20 and opens the damper 58 so that air
can exit the heat exchanger 28 through the air outlet 32.
[0035] FIG. 4 shows a temperature control apparatus 10 according to
a third embodiment of the present invention, which is substantial
similar to the previously described embodiments. For simplicity,
like parts have been labeled with like reference numbers and only
differences between the third embodiments and the previous
embodiments will be described in detail hereafter.
[0036] In the third embodiment of the present invention, a first
divider 42 and a second divider 43 extend across the evaporator
coil 34 dividing the evaporator coil 34 into a first portion 44, a
second portion 46, and a third portion 48. The first fan or blower
50 is adjacent the first portion 44, the second fan or blower 52 is
adjacent the second portion 46, and a third fan or blower 54 is
adjacent the third portion 48.
[0037] During operation in the defrost mode, the damper 58 is
closed, and the first valve is closed, preventing refrigerant from
the refrigeration circuit 20 from entering the evaporator coil 34.
Additionally, the second valve is opened to allow warm fluid from
the heating circuit to enter the evaporator coil 34. The controller
24 then cycles the first, second, and third fans 50, 52, 54 on and
off to move air through the heat exchanger 28 along at least two
flow paths.
[0038] For example, the controller 24 can be programmed to activate
the first fan 50 and deactivate the second and third fans 52, 54,
directing air through the heat exchanger 28 along a first flow path
80 (represented by arrows). The first flow path 80 extends across
the first portion 44 and back across the second and third portions
46, 48. The controller 24 can be programmed to activate the first
and second fans 50, 52 and deactivate the third fan 54, directing
air along a second flow path 82 (represented by arrows). The second
flow path 82 extends across the first and second portions 44, 46
and back across the third portion 48. The controller 24 can be
programmed to activate the first and third fans 50 and 54 and
deactivate the second fan 52, directing air along a third flow path
84 (represented by arrows). The third flow path 86 extends across
the first and third portions 44, 46 and then back across the second
portion 46. The controller 24 can be programmed to activate the
second fan 52 and deactivate the first and third fans 50, 54,
directing air across along a fourth flow path 88 (represented by
arrows). The fourth flow path 88 extends across the second portion
46 and back along the first and third portions 44, 48. One having
ordinary skill in the art will appreciate that by alternately
activating and deactivating the first, second, and third fans 50,
52, 54, the controller 24 can direct air along a number of other
air flow paths, which for reasons of simplicity and brevity have
not been described herein. Similarly, one having ordinary skill in
the art will appreciate that the present invention can alternately
include four, five, six or more fans with any number of air flow
pathways.
[0039] When defrost is no longer required or when the defrost mode
times out, the controller 24 shuts the second valve, preventing
warm fluid from entering the evaporator coil 34. The controller 24
also opens the first valve, reconnecting the evaporator coil 34 to
the refrigeration circuit 20 and opens the damper 58 so that air
can exit the heat exchanger 28 through the air outlet 32. The
controller 24 then activates the first, second, and third fans 50,
52, 54 and begins operation in either the cooling mode or the
heating mode.
[0040] FIG. 5 shows a temperature control apparatus 10 according to
a fourth embodiment of present invention, which is substantial
similar to the previously described embodiments. For simplicity,
like parts have been labeled with like reference numbers and only
differences between the fourth embodiment and the previous
embodiments will be described in detail hereafter.
[0041] In the fourth embodiment, the temperature control apparatus
10 is mounted on a truck 15 having a conditioned space 14. A heater
60 is positioned in the heat exchanger 28 between the evaporator
coil 34 and the first and second fans 50, 52. The heater 60 is an
electric heater with an internal heating coil (not shown).
Alternately, one having ordinary skill in the art will appreciate
that in other embodiments the evaporator coil 34 can be positioned
between the heater 60 and the first and second fans 50, 52. In
still other embodiments, the heater 60 can be formed integrally
with the evaporator coil 34. More specifically, the heater 60 can
include electric heating coils (not shown) which extend between
fins 80 located on the evaporator coil 34.
[0042] When the defrost mode is initiated, the controller 24 closes
the damper 58, preventing air from exiting the heat exchanger 28
through the air outlet 32. Additionally, the first valve (not
shown) in the refrigeration circuit 20 is closed, preventing cold
refrigerant from flowing into the evaporator coil 34. A heating
circuit 82 is in fluid communication with the truck's engine 84 and
extends into the outside housing 18. The heating circuit includes a
second valve (not shown). When heating or defrost is required, the
second valve is opened, allowing hot antifreeze from the truck's
engine 84 to enter the evaporator coil 34. The controller 24 cycles
the first fans 50 on to move air through the heat exchanger 28
along the first air flow path 64, which extends across the first
portion 44 and the second portion 46. After a predetermined time
(e.g., two minutes), the controller 24 cycles the first fan 50 off
and cycles the second fan 52. The second fan 52 directs air along
the second air flow path 66, which extends across the second
portion 46 and the first portion 44. In this manner, the heater 60
heats air in the heat exchanger 28, which in turn defrosts the
evaporator coil 34. Simultaneously, the warm antifreeze flows
through the evaporator coil 34, warming the evaporator coil 34 and
melting any frost that has accumulated on the coil 34. After
traveling through the evaporator coil 34, the antifreeze is
returned to the truck's engine 84 via the heating circuit.
[0043] When defrost is no longer required or when the defrost mode
times out, the controller 24 shuts the second valve, preventing
antifreeze from entering the evaporator coil 34. Also, the
controller 24 shuts down the heater 60 and directs the temperature
control apparatus 10 to resume operation the cooling mode, as
determined, at least in part, by the ambient temperature, the set
point temperature SP, and the temperature of the conditioned space
14.
[0044] The embodiments described above and illustrated in the
drawings are presented by way of example only and are not intended
as a limitation upon the concepts and principles of the present
invention. As such, it will be appreciated by one having ordinary
skill in the art, that various changes in the elements and their
configuration and arrangement are possible without departing from
the spirit and scope of the present invention as set forth in the
appended claims.
[0045] For example, the present invention is described herein as
being used in a trailer 12 having a single conditioned space 14.
However, one having ordinary skill in the art will appreciate that
the present invention could also be used in trucks or trailers
having multiple conditioned spaces 14.
[0046] As such, the functions of the various elements and
assemblies of the present invention can be changed to a significant
degree without departing from the spirit and scope of the present
invention.
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