U.S. patent application number 11/674477 was filed with the patent office on 2008-08-14 for unit cooler with integrated refrigeration and dehumidification.
This patent application is currently assigned to BRR TECHNOLOGIES, INC.. Invention is credited to Thomas J. Backman, Shawn Lee Lachappelle.
Application Number | 20080190121 11/674477 |
Document ID | / |
Family ID | 39684678 |
Filed Date | 2008-08-14 |
United States Patent
Application |
20080190121 |
Kind Code |
A1 |
Backman; Thomas J. ; et
al. |
August 14, 2008 |
UNIT COOLER WITH INTEGRATED REFRIGERATION AND DEHUMIDIFICATION
Abstract
An integrated refrigeration and dehumidification unit cooler for
a refrigerated space, such as a cold room, includes directly
serially connected refrigeration and heating coils operationally
interfaced to effect passive control of room temperature and
humidity conditions preventing overhead condensation.
Inventors: |
Backman; Thomas J.;
(Morehead City, NC) ; Lachappelle; Shawn Lee;
(Salter Path, NC) |
Correspondence
Address: |
Ishman Law Firm P.C.
P.O BOX 1245
Cary
NC
27512-1245
US
|
Assignee: |
BRR TECHNOLOGIES, INC.
Morehead City
NC
|
Family ID: |
39684678 |
Appl. No.: |
11/674477 |
Filed: |
February 13, 2007 |
Current U.S.
Class: |
62/115 ; 165/65;
62/498 |
Current CPC
Class: |
F24F 3/153 20130101;
F25B 6/04 20130101; F25D 17/042 20130101 |
Class at
Publication: |
62/115 ; 62/498;
165/65 |
International
Class: |
F25D 21/04 20060101
F25D021/04; F25D 17/06 20060101 F25D017/06 |
Claims
1. A unit cooler dehumidification system for maintaining a design
temperature of below about 41.degree. F. in a refrigerated space
with supply air at a humidity and at a dew point temperature
preventing condensation during operation, said system comprising: a
compressor located exterior of the space, said compressor having a
suction side to which a working fluid is supplied as a vapor at a
saturated suction temperature and a discharge side from which the
working fluid is discharged as a vapor at a high pressure and
elevated temperature; a condenser heat exchanger located exterior
of the space, said condenser heat exchanger supplied with said
superheated vapor from said compressor for exhausting heat from
said vapor and discharging the working fluid as a saturated liquid
at high pressure; a unit cooler located entirely in the space, said
unit cooler having a fan for providing an air flow passage between
an inlet receiving return air from said room and an outlet
delivering the supply air to said room, a cooling coil in said air
flow passage registering with said inlet for cooling and
dehumidifying said return air to a temperature below said design
temperature to said dew point temperature and a heating coil in
said air flow passage downstream of said coiling coil and
registering with said outlet for heating the cooled return air from
said cooling coil to a temperature at about said design
temperature, said heating coil directly supplied with said liquid
at high pressure from said condenser heat exchanger and discharging
said liquid at a reduced temperature; an expansion device directly
supplied with said liquid at a reduced temperature from said
heating coil and supplying said liquid at reduced pressure to an
inlet of said cooling coil, said cooling coil discharging said
liquid at reduced pressure from an outlet directly and continuously
to said inlet of said compressor.
2. The system as recited in claim 1 wherein said saturated suction
temperature of said compressor is sufficient to attain said dew
point temperature at said cooling coil and a relative humidity of
70% to 85%.
3. The system as recited in claim 2 wherein said saturated suction
temperature is below 25.degree. F.
4. The system as recited in claim 3 wherein said heating coil has
about 15% to 35% of the heat transfer surface of the cooling
coil.
5. The system as recited in claim 4 wherein said heating coil has
about 20% to 30% of the heat transfer surface of the cooling
coil.
6. The system as recited in claim 2 wherein said dew point
temperature is below about 25.degree. F.
7. The system as recited in claim 2 wherein said supply air
temperature is about 31.degree. F.
8. A method of operating a unit cooler contained in a refrigerated
room at a room design temperature below 41.degree. F. under
conditions avoiding condensation on overhead surfaces of the room,
comprising the steps of: selecting a dew point for supply air that
avoids the condensation and a supply air temperature for
maintaining said room design temperature; providing a unit cooler
having a refrigeration coil and a heating coil serially disposed in
a fan assisted air passage to routing return air to an inlet and
the supply air from an outlet; providing a first working fluid flow
path between an outlet of the refrigeration coil and the heating
coil having a compressor and a heat exchanger; providing a second
working fluid flow path directly serially connecting an outlet of
said heating coil and an inlet of said cooling coil; providing an
expansion device in said second working fluid flow path; operating
said heating coil at a temperature to achieve said dew point; and
operating said heating coil to achieve said supply temperature
while enabling said heating coil to achieve said dew point
temperature.
9. The method as recited in claim 8 including the step of providing
said heating coil with about 15% to 35% as much heat transfer area
as said cooling coil.
10. The method as recited in claim 9 including the step of
providing said heating coil with about 20% to 30% as much heat
transfer area as said cooling coil.
11. The method as recited in claim 10 including operating said
compressor as a suction temperature sufficient for the cooling coil
to attain said dew point temperature and said heating coil to
attain said supply air temperature.
12. A unit cooler for mounting at the ceiling area of a
refrigerated space comprising: a housing having an inlet and an
outlet; means for mounting said housing at the ceiling area of the
refrigerated space; a fan in said housing for establishing an air
flow between said inlet and said outlet; a coiling coil in said
housing adjacent said inlet having a cooling heat transfer surface;
a heating coil disposed in said housing between said cooling coil
and said outlet whereby said air flow is directed serially from
said cooling coil to said heating coil; first conduit means for
directly fluidly connecting an inlet of said heating coil with a
source of high pressure fluid at an elevated temperature whereby
said heating coil is effective for heating the air flow from said
cooling coil and lowering the temperature of said high pressure
fluid; second conduit means in said housing for directly and
continuously operatively fluidly connecting an outlet of said
heating coil with an inlet of said cooling coil; an expansion
device in said second conduit means for converting said high
pressure fluid from said outlet of said heating coil to a low
pressure cooled vapor at a cooled temperature for supply to an
outlet of said heating coil; and third conduit means for directly
fluidly connecting an outlet of said cooling coil to the inlet of a
compressor, wherein said heating heat transfer surface has an
effective area of about 15% to 35% of said cooling heat transfer
surface.
13. The unit cooler as recited in claim 12 wherein said heating
heat transfer surface has an effective area of about 20% to 30% of
said cooling heat transfer surface
Description
FIELD OF THE INVENTION
[0001] The present invention relates to systems for conditioning
enclosed spaces, and in particular to a unit cooler for
refrigerating and dehumidifying a storage space and for eliminating
moisture condensation therein.
BACKGROUND OF THE INVENTION
[0002] Present governmental code, regulations, and guidelines do
not allow any water to drip from overhead surfaces in food
processing rooms down upon the production area. Additionally, those
regulations have strict limits as to the temperatures at which
refrigerated food must be maintained, 41.degree. F. being the
accepted upper limit. For decades, food processors have utilized
traditional direct expansion refrigeration unit coolers as standard
components in field erected, or built up, systems that refrigerate
the processing rooms. The unit coolers are located within the
processing room and include a cooling coil and fan for circulating
and cooling the air within the room. The cooling coil is connected
at a direct expansion device interior to the unit cooler and to a
compressor located exterior of the processing room. Installation
requires only two fluid connections and modest control.
[0003] These unit coolers are effective at temperature control, but
not at humidity control. The direct refrigeration system maintains
the relative humidity (% Rh) levels in the food processing room at
about 90 to 100% Rh. These high Rh. levels present problems for
food processors. From time to time, the overhead equipment and/or
the overhead structure gets colder than the dew point of the air in
the room, particularly during defrost cycles. In these situations,
water from the air condenses on the overhead equipment and/or the
overhead structure. The condensed water then drips down upon the
production area. Such dripping raises the potential for food
contamination. If a governmental or private inspector notes such
dripping from the ceiling, they will typically require a cleanup
and sanitation procedure in the food processing room. This shutdown
results in waste disposal of the involved food and many labor hours
of lost production time for the food processor. As a result this is
an active interest in eliminating condensation through improved
dehumidification.
[0004] One basic approach is currently used, wherein a separate
desiccant dehumidification system is added to supplement the
conventional unit cooler. While satisfactory for avoiding
condensation problems, installation and equipment costs are high
and a large increase in energy consumption, 50% to 200%, is
incurred because the dehumidifiers use energy to operate and add
heat to the refrigerated space. This in turn increases the cooling
load on the refrigeration system and results in higher energy cost
for the refrigeration system.
[0005] It would be desirable to provide a unit cooler for these
cold room facilities that would provide both the requisite
refrigeration and operate at humidity levels overcoming
condensation problems. The use of serial refrigeration and reheat
coils has been proposed for lowering excessive humidity conditions
in ambient personal comfort conditions. Representative of such an
approach is disclosed in U.S. Pat. Nos. 5,622,057 and 3,798,920
wherein a reheat coil, modulated in response to humidity
conditions, is inserted fluidly before the cooling coil and
downstream thereof in the airflow. The two coils are substantially
the same. When dehumidification is required, the subcooling coil is
operative until set conditions are attained and thereafter
modulates within control limits. Such systems are accepted for
applications above about 50.degree. F., but are not approved by the
manufacturers for high humidity conditions below this temperature.
For temperatures below this level, the coil must operate at below
freezing temperatures, resulting in progressive ice buildup
requiring defrost cycles and varying the air flow to the reheat
coil. This results in control instability leading to high
maintenance costs, compressor failures, poor room temperature
control, erratic air flow and poor room humidity control.
SUMMARY OF THE INVENTION
[0006] This present invention provides a unit cooler for cold rooms
that passively provides temperature and humidity control without
modulation. The unit cooler provides full time dehumidification and
refrigeration in a factory assembled unit cooler that may be
installed and operated without complexity for either the system
installer or the system operator. The unit cooler uses directly and
continuously serially connected refrigeration direct expansion (DX)
and reheat/subcool (SR) coils to achieve lower % Rh room conditions
without a large increase in energy consumption.
[0007] The foregoing advantages are achieved by a unit cooler
employing design criteria that allows the refrigeration system to
dehumidify and run through defrost cycles without additional
controls or complexity or the difficulties of the prior art systems
discussed above. The unit cooler provides a passive and natural
balance of over-cool and reheat of air during refrigeration. This
is achieved by providing a desired dew point for the supply air
that avoids condensation, operating the DX coil at a temperature is
achieve the dew point and operating the SR coil to achieve the
desired supply temperature for maintaining the space at room design
temperature.
[0008] In achieving this benefit, the DX coil is operated at a
reduced saturated suction temperature (SST) about 3 to 9 degrees F.
without significantly increasing compressor equipment or operating
cost. By example, if a conventional system operates at +25.degree.
F. SST as a traditional DX system, the design suction temperature
is lowered to .+-.20.degree. F. SST. This represents an efficiency
loss to the system of roughly 8%, the traditional DX system Energy
Efficiency Ration (EER) being about 11.2, the present invention
operates at EER of about 9.2, which is significantly recoupled in
the present invention.
[0009] The unit cooler design criteria also requires that the SR
coil gives energy back to the refrigeration system that has
experienced a loss in design efficiency due to the above decrease
in design SST. That energy is returned in the SR coil pass as the
condensed liquid is refrigerated from saturation to a subcooled
state, and allows for about 15 to 25% of compressor cooling
capacity to be returned in liquid cooling. To accomplish this, the
unit cooler is to be designed with the SR coil to have 15% to 35%,
and preferably 20% to 30% as much primary coil surface and
secondary coil surface as the DX coil. Above and below this range,
passive operation cannot be attained and unreliable modulating
operation would be required. This recovers much of the lost
efficiency in the system, resulting in a system having an EER of
only 3% or less than the traditional DX refrigeration system, and
substantially less than the energy costs of separate units for
dehumidification.
[0010] Generally it is preferred to deliver air to the cold room at
roughly the same temperature, i.e. 41.degree. F. or less, and flow
rate as it would with a traditional DX refrigeration system to
maintain the design temperature. This is accomplished because the 3
to 9.degree. F. lower design SST creates a minimum air temperature
at the DX coil that is about 2 to 8.degree. F. lower than the
tradition DX refrigeration system. This establishes a dew point
with the passively integrated unit cooler that is about 2 to
8.degree. F. lower than a traditional DX refrigeration system.
[0011] With these design criteria the unit cooler naturally
delivers air with a relative humidity at 70% to 85%. For operation
within this range, controls are not needed as the dehumidification
unit cooler naturally balances out at these conditions. With this
supply air relative humidity, the passively integrated unit cooler
prevents water condensation dripping issues in the refrigerated
space.
[0012] The ability to refrigerate and dehumidify at the same time,
this invention has many applications outside of food processing
rooms. Those applications include controlled humidity storage rooms
for goods ranging from seeds to paper and from consumer goods to
industrial goods.
[0013] Accordingly, it is an object of the present invention to
provide a unit cooler providing a supply air at a humidity avoiding
condensation in cold room facilities.
[0014] Another object is to provide a unit cooler refrigeration
system that passively provides humidity control for cold room
facilities.
[0015] A further object is to provide a unit cooler for preventing
condensation problems in cold room facilities that may be installed
and operated without increased complexity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The above and other advantages of the present invention will
become apparent upon reading the following written description
taken in conjunction with the accompanying drawings in which:
[0017] FIG. 1 is a schematic drawing of cold room refrigeration
system having a unit cooler with integrated refrigeration and
dehumidification in accordance with an embodiment of the
invention;
[0018] FIG. 2 is a schematic drawing of the unit cooler of FIG.
1;
[0019] FIG. 3 is a schematic drawing of a cold room refrigeration
system incorporating a unit cooler in accordance with the prior
art;
[0020] FIG. 4 is a schematic drawing of the unit cooler of FIG.
3;
[0021] FIG. 5 is a pressure/enthalpy diagram comparing the systems
of FIG. 1 and FIG. 3;
[0022] FIG. 6 is a psychometric chart of the prior art
refrigeration system of FIG. 3; and
[0023] FIG. 7 is a psychometric chart of the refrigeration system
of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] A traditional DX refrigeration system for a unit cooler for
conditioning of a refrigerated space such as a cold room or walk-in
refrigerated or freezer room is shown in FIG. 3. Therein, a DX
refrigeration system 100 is provided for controlling the interior
temperature of a refrigerated room 102. The refrigeration system
100 comprises a refrigeration compressor 110 that delivers working
fluid such as refrigerant as a hot, high pressure discharge gas
from an outlet through outlet line 112, to the inlet of a condenser
114. The condenser 114 changes the refrigerant from a hot gas to a
warm liquid by rejecting heat from the refrigerant into another
medium such as air or water. The warm liquid is conveyed from an
outlet of the condenser through refrigerant line 116 to the inlet
of a direct expansion device 118 and through line 120 to a unit
cooler 122 located within the room 102. As shown in FIG. 4, the
unit cooler 122 includes a housing 124 typically mounted at the
ceiling area 125 of the room. The housing 124 encloses
refrigeration DX coil 126. The expansion device 118 expands the
refrigerant from a warm, high pressure liquid to a cold, low
pressure mixture of liquid and vapor refrigerant. This mixture is
delivered from the outlet of the expansion device 118 to the inlet
of the DX coil 126. The unit cooler 122 includes a fan 128 for
drawing return air from an inlet 130 through the coil 126 to an
outlet 132 for circulating conditioned air to the room at a
saturated controlled temperature, as indicated by the arrows. The
unit cooler 122 thus refrigerates the room 102 by absorbing heat at
the coil, boiling most or all of the cold liquid refrigerant to
cold vapor refrigerant. The resulting cold vapor is conveyed at low
pressure from the outlet of the coil 126 through line 134 to the
suction side or inlet of the compressor 110 at a saturated suction
temperature (SST).
[0025] The installation is simple requiring only two fluid
connections at the preassembled unit cooler The controls for such a
system are also basic, requiring a temperature control, and a
defrost system for deicing the coil. Deicing may be effected,
during system shut down conventionally through ambient thawing, or
electric or gas assisted deicing. The room operates at saturated
conditions at the design temperature, and deicing raises the air
temperature allowing condensate buildup, liquid or ice, on the now
colder room components resulting in undesired release onto food
products therein.
[0026] The present invention is shown in FIG. 1 and incorporates a
unit cooler that provides increased dehumidification without
increased complexity for the refrigeration system installer or
operator. The invention achieves humidity levels below 90% in
refrigerated rooms.
[0027] An integrated refrigeration and dehumidification unit cooler
system 10 according to an embodiment of the invention is shown in
FIGS. 1 and 2. Therein the system 10 provides both refrigerated and
dehumidified air for controlling temperature and humidity in a
refrigerated room 11, such as a food processing room. The
refrigeration system 10 comprises a refrigeration compressor 12
that delivers refrigerant as a hot, high pressure discharge gas
from an outlet through outlet line 14, to the inlet of a condenser
16. The condenser 16 changes the refrigerant from a hot gas to a
warm liquid by rejecting heat from the refrigerant into another
medium such as air or water. The compressor 12 and condenser 16 are
located exterior of the room, generally as outdoor units. The warm
liquid is conveyed to a unit cooler 18 located in the room 11 from
an outlet of the condenser 16 through refrigerant line 20.
[0028] As shown in FIG. 2, the unit cooler 18 includes a housing 22
typically mounted at the ceiling area 23 of the room. The housing
20 encloses an expansion device 24, a refrigeration DX coil 26, and
a subcool/reheat SR coil 28. The inlet of the SR coil 28 is
connected to line 20. The outlet of the SR coil 28 is connected to
the expansion device 24. The expansion device 24 is connected to
the inlet of the DX coil 26. The coils are thus directly fluidly
connected. The outlet of the DX coil 26 is connected by line 34 to
the inlet or suction side of the compressor 12.
[0029] The unit cooler 18 includes a fan 36 that draws return air
from an inlet 38 in an air path serially through the coils 26, 28
to an outlet 40 for circulating conditioned supply air as indicated
by the arrows and return to the inlet 32. As hereinafter described,
the supply air is at a supply air temperature for maintaining
temperature conditions at or below a design temperature and at a
dew point preventing condensation on overhead surfaces
notwithstanding defrost cycles and operational conditions.
[0030] The SR coil 28 uses coil air from DX coil 26 to subcool the
refrigerant liquid to a temperature below saturation. The subcooled
refrigerant liquid is moved through subcooled liquid line 30 to the
expansion device 24, which receives refrigerant liquid in a
sub-cooled state. With sub-cooled refrigerant liquid, the expansion
device can do more cooling than it could with warm, saturated
refrigerant liquid in the prior art system. The sub-cooling of the
refrigerant liquid gives DX coil 26 the ability to do more cooling
than it could with warm, saturated refrigerant liquid. The extra
cooling capacity allows DX coil 26 to cool air entering the unit
cooler to a lower temperature than it could with warm, saturated
refrigerant liquid. In this case the colder air coming from DX coil
26 is still at 100% Rh. Once the DX coil 26 cools the air to this
new lower level, the air is heated by SR coil 28. In this way the
air ends up with a relative humidity below 100% Rh due to the
reheating by the SR coil 28 to a temperature above the moisture
saturation condition.
[0031] The unit cooler 18 refrigerates and dehumidifies the air by
delivering air to the room 11 at a temperature that is still low
enough to hold the room at the design temperature, but at a lower
relative humidity. Obtainable relative humidity numbers for air
leaving the SR coil 28 are in the range of 75% to 90%.
[0032] Because SR coil 28 drives lower air temperatures in DX coil
26, the temperature that unit cooler 18 delivers to room 11 is
nominally the same after SR coil 28 as it would be in the prior art
DX refrigeration system of FIG. 2. The heat that SR coil 28 removes
from the refrigeration system results in colder air leaving DX coil
26. Then SR coil 28 returns the same amount of heat to the treated
air, an air dehumidification process that is termed overcool and
reheat.
[0033] The differences between the present and prior art systems
are apparent from the pressure enthalpy diagram of FIG. 5 that
represents the specific energy states and corresponding pressures
in the refrigeration cycle. Therein, the prior art system is shown
in solid lines with the component numbers used in FIG. 3. The
present system is shown in solid and dashed lines with the
component numbers used in FIG. 1. The prior art refrigeration
system comprises the line 110 that represents the refrigeration
compressor that delivers hot, high pressure refrigerant discharge
gas through a point that the inlet to the condenser. The line 114
represents the condenser that changes the refrigerant from a hot
gas to a warm liquid by rejecting heat from the refrigerant into
another medium such as air or water. The warm liquid is conveyed to
the inlet of the expansion device. The line 118 represents the
expansion device that expands the refrigerant from a warm, high
pressure liquid to a cold, low pressure mixture of liquid and vapor
refrigerant. This expanded refrigerant is delivered to the inlet of
the DX coil located in a unit cooler. The line 122 represents the
change in enthalpy across the DX Coil where the resulting cold
refrigerant vapor is conveyed at low pressure to the inlet of the
compressor whereat the process repeats.
[0034] The enthalpy diagram for the present invention, as in prior
art system, the line 12 represents the change across the compressor
and the line 14 the change across the condenser. The contribution
of the SR coil to subcooling is denoted by line 28 wherein the
refrigerant liquid is further cooled into the lower enthalpy
sub-cooled zone. The change across the expansion device is denoted
by line 18. Thus, the contribution of the DX coil to the change in
enthalpy is increased as denoted by line 26 in comparison to line
122.
[0035] The contribution of the SR coil 28 to the dehumidification
of supply air to the room is shown in the comparison of the systems
in the psychometric charts of FIGS. 6 and 7. FIG. 6 shows the prior
art system of FIG. 3 and represents the specific energy states and
corresponding absolute moisture content of air. The air is cooled
in the unit cooler by the DX coil along line 122 and exits at the
outlet point 132. The air passes through the room along line 102
and returns to the unit cooler at inlet point 130 with a relative
humidity of 85 to 98%. As the air passes through DX coil 122
sensible heat (dry) and latent heat (wet) are removed. This has the
effect of lowering the dry bulb temperature of the air and lowering
the absolute moisture content of the air. The air exits at outlet
point 132 with a relative humidity at or near 100%. This air motion
cools the refrigerated room while gaining sensible heat, which
increases the dry bulb temperature, and gaining latent heat, which
increases the moisture content. In this process moisture is removed
from the air, but the room stays in a condition of high relative
humidity. This creates an environment where temperature fluctuation
and refrigeration system defrost cycles can create dew point
temperatures that are higher than the temperature of equipment or
structural components in the refrigerated room. That is when liquid
water condenses on the overhead equipment and/or the overhead
structure. The condensed water then drips down upon the storage
area or production area in the refrigerated room. The air is
returned at point 132 around a 98% Rh.
[0036] In FIG. 1 and 2, the present invention, the SR coil 28
reduces the dry bulb temperature to the outlet point 40 providing
an 81% Rh. The air circulation in the room along line 11 results in
an intake condition at inlet point 38 of 85% Rh, a humidity
condition that accommodates room temperature excursions during
operation. This is achieved by the unit cooler delivering colder,
lower humidity air. Although the air is gaining sensible heat,
which increases the dry bulb temperature, and gaining latent heat,
which increases the moisture content, the room remains in a
condition of low enough relative humidity to prevent condensation
dripping. This creates an environment where temperature fluctuation
and refrigeration system defrost cycles do not create dew point
temperatures that are higher than the temperature of equipment or
structural components in the refrigerated room.
[0037] The method for establishing the above operation for a
refrigerated space will initially prescribe a supply air
temperature for maintaining an upper permissible room temperature
or less and also the required air flow volume. Based on operations
within the room, a dew point range for the supply air is prescribed
that will provide acceptable humidity conditions preventing
condensation on overhead surfaces. The dew point thus establishes
the operating dew point for the DX coil and the temperature rise
from the SR coil. A compressor/condenser package is then selected
for achieving the dew point. A SR coil size is determined to
achieve the temperature rise at the air flow. The heat balance of
the system is then determined. Because of the addition of the SR
coil and consequent lowering of the fluid temperature to the
expansion device and DX coil, a lower DX coil dew point may result
requiring reiterations of these steps be undertaken as necessary to
establish the interface between the coils to achieve performance
within the design limits.
[0038] An example of the foregoing advantages is set forth in the
following example.
EXAMPLE
[0039] A prior art system is operated with a compressor, Model No.
06DM316, from Caryle, providing a saturated suction temperature
(SST) of 25.degree. F. and a saturated condensing temperature (SCT)
of 115.degree. F. The net refrigeration effect of this
refrigeration system is (nominal 4 Tons) 48,000 btu/hr of cooling,
which is delivered to a refrigerated room through a system of FIG.
3 using a traditional unit cooler. The power consumption of the
refrigeration compressor is 5.5 kW in this condition. The unit
cooler will treat air from the refrigerated space while following
the saturation line. Accordingly, although moisture is removed, the
air is delivered to the refrigerated room at 100% RH. The unit
cooler has in intake of 2,640 scfm of air at 40.0.degree. F.
db/39.8.degree. F. wb (98% RH). The unit cooler supplies air to the
refrigerated space at 31.1.degree. F. db/31.0.degree. F. wb (99%
RH). The unit cooler removes (nominal) 21,000 btu/hr of latent
(wet) cooling load from the refrigerated space. The unit cooler
removes moisture removal at (nominal) 17 lbs/hr.
[0040] A system in accordance with FIG. 1 uses a compressor, Model
number 06DA818 from Caryle Corp, which is slightly larger than the
compressor in the prior example. The compressor operates at a
saturated suction temperature (SST) of 20.degree. F. (lower than
the prior example) and a saturated condensing temperature (SCT) of
115.degree. F. (same as the example). The net refrigeration effect
of this refrigeration system is (nominal 5.1 Tons) 61,000 btu/hr of
cooling, which is delivered to a refrigerated room through a
traditional unit cooler. The power consumption of the refrigeration
compressor is 5.8 kW (5.5% higher than the base example) in this
condition of (nominal 5.2 Tons) 61,000 btu/hr of cooling. The unit
cooler will draw in 2,640 scfm of air at 40.0.degree. F.
db/38.1.degree. F. wb (85% RH). This unit cooler supplies air to
the refrigerated space at 31.2.degree. F. db/29.3.degree. F. wb
(81% RH). The unit cooler removes (nominal) 21,000 btu/hr of latent
(wet) cooling load from the refrigerated space. This is the same
latent cooling as the prior base example, but with a lower relative
humidity than the base example, by 14% RH. The unit cooler moisture
removal is (nominal) 17 lbs/hr, which is the same as the base
example.
[0041] These examples demonstrate that the system in accordance
with the present invention incorporating the integral
sub-cool/reheat coil able to achieve dehumidification in a
refrigerated space runs with 5.5% more power consumption than
traditional DX refrigeration, but with a lower relative humidity by
14% RH. Such a reduction accommodates the temperature excursions
typically encountered in food processing without presenting a
condensation condition on in-place equipment. The modest power
increase is substantially less, both in capital and operating cost,
that a supplemental installation. The synergistic effects of the
subcooling and reheating of the SR coil thus provides an effective
solution for overcoming condensation problems in refrigerated
storage applications.
[0042] Having thus described a presently preferred embodiment of
the present invention, it will now be appreciated that the objects
of the invention have been fully achieved, and it will be
understood by those skilled in the art that many changes in
construction and widely differing embodiments and applications of
the invention will suggest themselves without departing from the
spirit and scope of the present invention. The disclosures and
description herein are intended to be illustrative and are not in
any sense limiting of the invention, which is defined solely in
accordance with the following claims.
* * * * *