An indoor facility provided with a liquid refrigerant dehumidifier
coil connected with the main refrigeration coils in a secondary
refrigerant loop and a compressor waste heat coil coupled with the
primary refrigerant loop and heating a desiccant wheel for removing
further humidity from the process air stream.
What is claimed is:
1. In an indoor facility having an enclosed volume to be humidity
controlled, a dehumidification system comprising: an air handling
system having a process conduit and a regeneration conduit, a return
line fluidly connecting the enclosed volume with an inlet of said
process conduit and establishing a process air flow therethrough;
means for supplying ambient air to said return line; a supply line
fluidly connecting an outlet of said process conduit with the enclosed
volume; an aqueous liquid refrigeration system for maintaining a
cooling load in said volume; a dehumidification coil in said process
conduit operatively connected with said liquid refrigeration system;
rotating desiccant means in said air handling system having a first
portion disposed in said process conduit and a second portion disposed
in said regeneration conduit; fan means in said regeneration conduit
for conducting ambient air from an inlet to an outlet; a primary
refrigeration system including a compressor thermally coupled with
said secondary refrigeration system; waste heat exchange means in
said regeneration conduit thermally coupled with said compressor
for heating said second portion of said desiccant means to an elevated
temperature in said regeneration conduit and for thereby removing
in said process conduit a first portion of moisture from said process
air flow; and dehumidification means in said process conduit for
reheating and removing a second portion of moisture from said process
air flow supplied to said supply line.
2. The system as recited in claim 1 wherein said waste heat exchange
means heats said second portion of said desiccant means to about
50 to 100.degree. F. deg.
3. The system as recited in claim 2 wherein said reheating in said
process conduit heat said process air flow to about 50 to 70.degree.
4. The system as recited in claim 3 wherein said liquid refrigeration
system uses a refrigerant liquid selected from the group of glycols
5. The system as recited in claim 4 wherein said glycols includes
ethylene glycol and propylene glycol.
6. The system as recited in claim 4 wherein brines include calcium
chloride, sodium chloride or organic salt solutions.
7. A dehumidification system for an indoor facility having a cooling
load coupled with a secondary liquid refrigeration system which
is coupled with a direct expansion refrigeration system including
a compressor generating waste heat, a dehumidification system comprising:
air handling means having a process flow means and a regeneration
flow means, said process flow means receiving humid air from said
facility and returning dehumidified air to said facility, said regeneration
flow means discharging air to the exterior; dehumidification coil
means thermally coupled with said secondary liquid refrigeration
system in said process flow means for removing a first portion of
moisture from said humid air to a dew point of below about 36.degree.
F.; desiccant means in said air handling means rotating between
said process flow means and said regeneration flow means, said desiccant
means removing a second portion of moisture from said humid air
received in said process flow means from said dehumidification coil
means and for reheating said humid air to about 50 to 70.degree.
F., said desiccant means in said regeneration flow means being heated
to about 50 to 100.degree. F. and discharging said second portion
of moisture to said regeneration flow means.
FIELD OF THE INVENTION
The present invention relates to dehumidification and, in particular,
to a system using aqueous based secondary loop cooling augmented
with a low temperature range desiccant system for controlling excess
humidity under extreme or revised operating conditions.
BACKGROUND OF THE INVENTION
Indoor facilities employing freezing, cooling or refrigeration
loads can present significant dehumidification problems. Indoor
ice arenas and supermarkets present particular concerns. In ice
arenas, the ice rink surface is maintained at subfreezing temperatures
by a liquid secondary cooling loop, customarily utilizing glycol
as the liquid refrigerant. The ice surface and spectators and participants
generate a substantial humidity load that can result in undesirable
condensation, particularly under extreme environmental temperature
and humidity conditions and to the detriment of equipment and attendant
personnel comfort. Similarly, the freezer, cooler, and refrigeration
equipment, and customers in supermarkets generate substantial humidity
loads creating like equipment and personnel problems.
An improved energy efficient air handling system for maintaining
humidity levels in ice rink facilities is disclosed in my prior
patent, U.S. Pat. No. 6321551. Therein, the process air stream
is cooled and dehumidified at a dehumidifier unit serially connected
with the ice rink coils, and reheated by a waste heat exchanger
to a low return temperature. The system significantly reduces the
parasitic heating by the return air resulting in dramatically lowered
utility costs, and handles substantial dehumidification loads.
There is a current trend, however, at the state and municipal regulatory
level to mandate increases in the amount of exterior make up air
in the return air flow to the above facilities. This added make
up air volume establishes an incremental dehumidification burden
that can exceed the capabilities of the existing equipment. To avoid
the need for upsizing the equipment and thus increasing capital
and operating costs, it would be desirable to utilize the thermal
benefits of the patented system while handling the increased dehumidification
SUMMARY OF INVENTION
The present invention addresses and overcomes the aforementioned
problems and limitations by supplementing the dehumidification unit
in the process air stream with a desiccant rotor operating in temperature
ranges substantially below current practice. The regeneration portion
of the rotor is heated, without flame, by a reheat coil coupled
with a waste heat line from the compressor in the primary loop.
Inasmuch as these compressors are in the range of 110 to 600 hp.
substantial waste heat is available allowing reheating to a regeneration
temperature in the range of about 50.degree. to 100.degree.. These
temperatures are substantially below the regeneration temperature
of conventional desiccant systems that are flame heated operate
at regeneration temperatures of about 200.degree. to 350.degree.
F. and require substantial heating costs. This regeneration temperature
provides sufficient desiccant media capacity to remove further moisture
from the process air stream exiting the liquid cooled dehumidification
coil while reheating the dehumidifiedreturn air to a satisfactory
supply temperature of about 60.degree. to 80.degree. F.
DESCRIPTION OF DRAWINGS
The above and other objects and advantages of the present invention
will become apparent upon reading the following detailed description
taken in conjunction with the accompanying drawings in which:
FIG. 1 is a schematic diagram of a desiccant assisted dehumidification
system for secondary liquid refrigerant facilities in accordance
with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the FIG. 1 for the purpose of describing a preferred
embodiment of the present invention and not for limiting same, there
is shown an indoor facility 10 having a cooling coil array 12 coupled
with a cooling load 14 and provided with a desiccant assisted dehumidification
system 16 for establishing and maintaining humidity levels within
the enclosed space 18 of the facility 10 to prevent condensation
and provide personnel comfort. The present embodiment will be described
with reference to an ice rink facility wherein the cooling load
is the ice rink, and the coil array is the underlying rink coils.
For other applications such as supermarkets and like commercial
facilities, the cooling load is the refrigerated equipment and the
cooling load are the various refrigeration coils associated therewith.
The ice rink facility 10 is provided with underlying rink coils
12 connected in a liquid refrigerant secondary refrigeration system
22 thermally coupled with a direct vaporization primary refrigeration
system 24 at a heat exchanger 26 for maintaining the ice rink 14
at a temperature establishing a skating surface suited for the activities
conducted thereon. The liquid refrigerant employed in the secondary
refrigeration system is typically an aqueous based glycol or brine.
The primary refrigeration system 24 includes a compressor 30 connected
in fluid line 32 with the primary coil 34 of the heat exchanger
26. The secondary refrigeration system 22 includes a secondary coil
36 at the heat exchanger 26 connected to a main supply line 40
which is connected to the inlet of the rink coils 12. The outlet
of the rink coils 12 is connected with a main return line 42.
The system 16 includes an air handler 50 having a process conduit
52 conducting a process stream 53 in the direction of the arrows
and a regeneration conduit 54 conducting a regeneration stream 55
in the direction of the arrows. The inlet of the process conduit
52 is connected with the enclosure 18 of the facility 10 by a return
line 56. The return line 56 is connected at connection 57 to exterior
line 58 exhausting humidified air from the facility and make up
line 59 admitting air from exterior of the facility. The outlet
of the process conduit 52 is connected with the enclosure 18 of
the facility 10 by supply conduit 60. The regeneration conduit 54
has an inlet flow 61 obtained interior or exterior of the facility
10 and an outlet flow 62 discharging exterior of the facility.
A dehumidifier coil 70 is disposed in the process conduit 52 adjacent
the return line 56. The coil 70 is connected in parallel to the
return line 42 of the secondary refrigeration system 22 by inlet
line 72 and outlet line 74. A control valve 76 maintains the coil
70 at a temperature of below about 36.degree. F., preferably 34.degree.
F. or below, with below freezing coil temperatures achievable with
coil defrost cycles.
A conventional rotating desiccant wheel 80 includes a reheat sector
82 disposed in the process conduit 52 and a dehumidification sector
84 disposed in the regeneration conduit 54. The reheat sector 82
is effective for absorbing moisture from the process air stream
exiting the dehumidifier coli 70 and raising the temperature of
the air stream entering the supply conduit 60. A waste heat exchanger
86 is disposed in the process conduit 52 upstream of a dehumidification
sector 84 of the desiccant wheel 80. The waste heat exchanger 86
is effective to raise the temperature of the dehumidification sector
84 to expel absorbed moisture therefrom for delivery to the exit
stream. The waste heat exchanger 86 is thermally coupled by lines
90 92 with the compressor 30 for transferring waste heat therefrom.
A fan 94 in the regeneration conduit 54 establishes and regulates
fluid flow in the conduit 52.
In the regeneration sector, the desiccant is heated to a regeneration
temperature in the range of about 50.degree. to 100.degree. F. This
range is substantially below conventional desiccant systems that
are flame heated to operate at regeneration temperatures of about
200.degree. to 350.degree. F., which correlates to a supply temperature
of about 110.degree. to 135.degree. F. The waste heat generated
by the large horsepower compressor is sufficient for such reheat.
This regeneration temperature provides a desiccant media capacity
for removing further moisture from the process air stream 53 exiting
the dehumidification coil 70 and to reheat the return air to a supply
or process return temperature of about 50.degree. to 70.degree..
This capacity gives the system sufficient capability to handle variable
amounts of makeup air without resizing of the secondary refrigeration
system or air handler equipment as illustrated by the following
An ice rink facility requires a total air flow of 10000 SCFM and
a return air supply temperature at a dew point of 34.degree. F.
to avoid condensation effects. Under original code, a 20% outdoor
air flow was required. Under new code regulations, a 30% outdoor
air flow is required. The facility is provided with an existing
system in accordance with the '221 patent. The new system incorporates
the desiccant assist of the present invention.
Old Code New Code New Code Description Orig. Sys. Orig. Sys. New
Sys. Total Air Flow SCFM 10000 10000 10000 Return Air Flow SCFM
8000 7000 7000 Outdoor Air Flow SCFM 2000 3000 3000 Coil Cooling
Capacity, tons 35.8 35.8 35.8 Coil Moisture Removal, lb/hr 150.8
155.5 155.5 Coil Dew Point, Deg. F. 34 38 38 Desiccant Moisture
Removal, lb/hr 0 0 35.5 Total Moisture Removal, lb/hr 150.8 155.5
190.0 System Dew Point, Def. F 34 38 34 Supply Air Temp., Deg. F.
65 65 65
The foregoing demonstrates that the existing system, while able
to handle the original operating conditions, is not able to handle
the increase of outdoor air flow without raising the dew point,
i.e. 38 deg F., to a level where adverse condensation effects occur.
On the other hand, keeping the in-place equipment and supplementing
with only the desiccant system allows facility to maintain acceptable
dew point and supply air temperatures.
Suitable aqueous based refrigeration fluids suitable for the secondary
system include: glycol solutions comprising ethylene glycol and
propylene glycol; and brines comprising calcium chloride, sodium
chloride and organic salt materials.
The above description is intended to be illustrative of the preferred
embodiment, and modifications and improvements thereto will become
apparent to those in the art. Accordingly, the scope of the invention
should be construed solely in accordance with the appended claims.