U.S. patent application number 11/403950 was filed with the patent office on 2006-08-24 for controlling humidity in zones during a drying process.
Invention is credited to Claude Bourgault, Larry Dancey.
Application Number | 20060185838 11/403950 |
Document ID | / |
Family ID | 36911421 |
Filed Date | 2006-08-24 |
United States Patent
Application |
20060185838 |
Kind Code |
A1 |
Bourgault; Claude ; et
al. |
August 24, 2006 |
Controlling humidity in zones during a drying process
Abstract
A method of controlling humidity in each of a plurality of zones
of an enclosed space during a drying process includes, in each
zone, drawing air from the zone to create an air stream through a
heating element and discharging the air stream into the zone;
sensing the relative humidity of the air in a sensing location in
the zone; in response to the relative humidity sensed at the
sensing location, operating the heating element to raise a
temperature of the air stream as required to reduce the relative
humidity of the air in the zone to a desired relative humidity. The
method reduces over-drying and increases the efficiency of the
drying process.
Inventors: |
Bourgault; Claude; (St.
Brieux, CA) ; Dancey; Larry; (Melfort, CA) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Family ID: |
36911421 |
Appl. No.: |
11/403950 |
Filed: |
April 14, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10751455 |
Jan 6, 2004 |
|
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11403950 |
Apr 14, 2006 |
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Current U.S.
Class: |
165/223 |
Current CPC
Class: |
F26B 21/001 20130101;
E04B 1/7015 20130101; F26B 21/08 20130101 |
Class at
Publication: |
165/223 |
International
Class: |
F24F 3/14 20060101
F24F003/14 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 17, 2005 |
CA |
2,527,275 |
Claims
1. A method of controlling humidity in each of a plurality of zones
of an enclosed space during a drying process, the method
comprising: in each zone, drawing air from the zone to create an
air stream through a heating element and discharging the air stream
into the zone; sensing the relative humidity of the air in a
sensing location in the zone; in response to the relative humidity
sensed at the sensing location, operating the heating element to
raise a temperature of the air stream as required to reduce the
relative humidity of the air in the zone to a desired relative
humidity.
2. The method of claim 1 wherein the sensing location is located to
sense the relative humidity of the air stream after the air stream
passes through the heating element.
3. The method of claim 1 comprising drawing air from the zone to
create an air stream through a heating element and discharging the
air stream into the zone by providing a portable heat exchanger
unit in each zone, each portable heat exchanger unit comprising: a
fan operative to create the air stream by drawing air from an
intake and discharging the air through an outlet; and a heating
element located in the air stream.
4. The method of claim 3 comprising sensing the relative humidity
by providing a humidity sensor operative to sense the relative
humidity of the air in the sensing location in the zone and
operative to send a humidity signal.
5. The method of claim 4 comprising mounting the humidity sensor on
the portable heat exchanger unit in the zone such that the sensing
location is at the outlet of the portable heat exchanger unit to
sense the relative humidity of the air stream as it is discharged
through the outlet.
6. The method of claim 4 comprising providing a heat controller
operative to receive the humidity signal and operative to change an
amount of heat energy supplied to the heating element in response
to the humidity signal.
7. The method of claim 6 wherein the heating element comprises a
fluid coil connected to a fluid heater such that heated fluid from
the fluid heater flows through the fluid coil, and wherein the heat
controller is operative to adjust an amount of heated fluid flowing
through the fluid coil from a maximum flow to a minimum flow.
8. The method of claim 7 wherein the fluid heater is connected to
the fluid coil of a portable heat exchanger unit in each zone.
9. The method of claim 8 wherein a temperature of the heated fluid
at a supply port of the fluid heater increases when the amount of
heated fluid flowing through the fluid coils is reduced below the
maximum flow.
10. The method of claim 9 wherein the fluid heater has a heating
capacity that is insufficient to raise the temperature of the air
stream in each zone such that the relative humidity of each air
stream is reduced to the desired relative humidity, and wherein
when the heat controller on a first portable heat exchanger unit
reduces the flow of heated fluid below the maximum flow, the
temperature of the heated fluid at the supply port of the fluid
heater increases.
11. A method of drying an enclosed space, the method comprising:
providing a plurality of portable heat exchanger units, each
portable heat exchanger unit comprising: a fan operative to create
an air stream by drawing air from an intake and discharging the air
through an outlet; a fluid coil located in the air stream; and a
heat controller operative to adjust a flow of fluid through the
fluid coil; positioning at least one portable heat exchanger unit
as an outside air unit with the intake thereof oriented to draw air
from outside the enclosed space and with the outlet thereof
oriented to discharge the air stream thereof into the enclosed
space; positioning a plurality of portable heat exchanger units as
inside air units at spaced apart unit locations inside the enclosed
space and orienting the intakes and outlets of each inside air unit
to draw air from the enclosed space adjacent to the inside air unit
and to discharge the air stream into the enclosed space adjacent to
the inside air unit; connecting the fluid coils of each portable
heat exchanger unit to a fluid heater and circulating heated fluid
from the fluid heater through the fluid coils and operating the
fans; sensing the relative humidity of the air stream created by
each inside air unit; and operating the heat controller of each
inside air unit to raise a temperature of the corresponding air
stream as required to reduce the relative humidity of the air
stream to a desired relative humidity, and allowing an amount of
air substantially equal to the amount of air drawn from outside the
enclosed space to exhaust from the enclosed space.
12. The method of claim 11 comprising dividing the enclosed space
into zones and positioning a portable heat exchanger unit in each
zone.
13. The method of claim 11 comprising sensing the relative humidity
of the air stream created by each inside air unit by mounting a
humidity sensor on each inside air unit at a sensing location such
that the humidity sensor is operative to sense the relative
humidity of the air stream, and wherein each heat controller is
operative to receive a humidity signal generated by the humidity
sensor.
14. The method of claim 11 further comprising sensing the relative
humidity of the air stream of the outside air unit and operating
the heat controller of the outside air unit to raise a temperature
of the corresponding air stream as required to reduce the relative
humidity of the air stream to a selected relative humidity.
Description
[0001] This is a continuation-in-part (CIP) of U.S. patent
application Ser. No. 10/751,455 "METHOD AND APPARATUS FOR
CONTROLLING HUMIDITY AND MOLD", filed Jan. 6, 2004, the disclosure
of which is hereby incorporated herein by reference.
[0002] This invention is in the field of removing moisture from
buildings and like enclosed spaces, and in particular methods for
controlling such removal to maximize efficiency.
BACKGROUND
[0003] It is well known that excessive moisture in buildings causes
considerable problems. Drywall and flooring absorb moisture and are
readily damaged if the excessive moisture condition persists for
any length of time. Interior elements such as insulation, studs,
and joists can eventually be affected as well. Furthermore, mold
begins to form on the damp building materials, and can remain in
the structure even after it has dried, causing breathing problems
for persons occupying the building.
[0004] At the extreme, such excessive moisture conditions are
exemplified by a flooded building. U.S. Pat. No. 6,457,258 to
Cressy et al., "Drying Assembly and Method of Drying for a Flooded
Enclosed Space", discloses an apparatus for drying flooded
buildings that overcomes problems in the prior art. Such prior art
is said to require stripping wall and floor coverings and using
portable dryers to circulate air to dry out the exposed floor
boards, joists and studs. The methods were slow and allowed mold to
form on the interior framing, which could then go unnoticed and be
covered up and then later present a health hazard to occupants.
[0005] The solution proposed by Cressy is to introduce very hot and
dry air into the building, indicated as being at 125.degree. F. and
5% relative humidity, in order to dry the building very quickly to
prevent mold growth and allow an early return to occupants. In the
apparatus of Cressy et al., outside air is heated by a furnace and
the heated air is blown into the building where it picks up
moisture and then is exhausted back outside. In Cressy heat from
the warmer exhaust air is transferred to the cooler outside air
prior to heating by the furnace, thereby increasing the efficiency
of the system.
[0006] U.S. Pat. No. 6,647,639 to Storrer, "Moisture Removal
System", addresses the problem of extracting water promptly to
prevent the formation of rot, mold, rust and the like in flooded
buildings. Storrer reveals the prior art as including passive
drying through opening windows, etc. and active drying using forced
air (heated or not) to expedite evaporation. Storrer discloses
using a blower to blow (or draw) dry air through a hose and
manifolds that can be directed at a particular area that it is
desired to dry.
[0007] In a similar vein, U.S. Pat. No. 5,960,556 to Jansen,
"Method for Drying Sheathing in Structures", is directed to drying
walls with warm, low humidity air.
[0008] Prior art systems for drying flooded buildings also include
dessicant dehumidifiers that use a desiccant material with a high
affinity to water to absorb water from the air, and refrigerant
dehumidifiers that condense water out of the air by cooling it. In
both of these systems, the water must be disposed of in some
manner. The water absorbed by the dessicant material is removed by
subsequently drying the material. The water condensed by the
refrigerant system is collected in a reservoir that must be emptied
from time to time or piped to a disposal area. Care must be taken
that the collected water be removed so that mold does not form
therein and disperse within the building.
[0009] While flooded buildings demonstrate an extreme situation,
excessive moisture also causes problems in other situations as
well. During construction wet conditions are often present in
buildings. Long periods of rain during construction, burst pipes,
wet building materials (such as concrete), and like conditions can
contribute to humid conditions where excessive moisture can be
absorbed by joists and studs. These moist members are often covered
up by flooring and drywall such that drying is prevented, and rot,
mold, and the like can form.
[0010] In cold climates it is also common to use construction
heaters to warm buildings during construction. Such heaters that
use combustion inside the building also cause a significant
increase in the humidity of the air inside the building,
contributing to excessive moisture inside walls and floors and the
problems associated therewith.
[0011] The opposite condition of excessively dry air in a building
can cause problems as well. Excessively dry air can draw moisture
out of wood causing warping and splitting of floors and
millwork.
SUMMARY OF THE INVENTION
[0012] It is an object of the present invention to provide a method
and apparatus for controlling the condition of air in enclosed
spaces that overcomes problems in the prior art
[0013] The present invention provides, in a first embodiment, a
method of controlling humidity in each of a plurality of zones of
an enclosed space during a drying process. The method comprises in
each zone, drawing air from the zone to create an air stream
through a heating element and discharging the air stream into the
zone; sensing the relative humidity of the air in a sensing
location in the zone; in response to the relative humidity sensed
at the sensing location, operating the heating element to raise a
temperature of the air stream as required to reduce the relative
humidity of the air in the zone to a desired relative humidity.
[0014] The present invention provides, in a second embodiment, a
method of drying an enclosed space. The method comprises providing
a plurality of portable heat exchanger units, each portable heat
exchanger unit comprising: a fan operative to create an air stream
by drawing air from an intake and discharging the air through an
outlet; a fluid coil located in the air stream; and a heat
controller operative to adjust a flow of fluid through the fluid
coil; positioning at least one portable heat exchanger unit as an
outside air unit with the intake thereof oriented to draw air from
outside the enclosed space and with the outlet thereof oriented to
discharge the air stream thereof into the enclosed space;
positioning a plurality of portable heat exchanger units as inside
air units at spaced apart unit locations inside the enclosed space
and orienting the intakes and outlets of each inside air unit to
draw air from the enclosed space adjacent to the inside air unit
and to discharge the air stream into the enclosed space adjacent to
the inside air unit; connecting the fluid coils of each portable
heat exchanger unit to a fluid heater and circulating heated fluid
from the fluid heater through the fluid coils and operating the
fans; sensing the relative humidity of the air stream created by
each inside air unit; operating the heat controller of each inside
air unit to raise a temperature of the corresponding air stream as
required to reduce the relative humidity of the air stream to a
desired relative humidity; and allowing an amount of air
substantially equal to the amount of air drawn from outside the
enclosed space to exhaust from the enclosed space.
[0015] Raising the temp of air 10.degree. C. will reduce the
relative humidity of the air by about 50%. By sensing the relative
humidity of the air at a sensing location, conveniently at the air
stream outlet a heat controller can be operated to supply heat at
the proper rate to achieve a desired relative humidity in the air
stream, and thus in the zone.
[0016] The relative humidity of the air is an indicator of how much
water the air is holding, and thus how much more water it can hold.
For example, in a closed room with standing water on the floor, the
relative humidity would approach 100% (i.e. the air would become
saturated with water) and so no more water would evaporate off the
floor. Raising the air temp 10.degree. C. will reduce the relative
humidity by 50%, resulting in a humidity gradient between the water
and the air, and thus more water will evaporate off the floor and
the relative humidity will again rise to 100%, provided no air
moves in or out of the room. By bringing in a dryer air stream and
thereby pushing the wet air out of the room through an exhaust, the
water is literally carried out of the room by the exhaust air with
the result that all the water will eventually evaporate and be
carried out of the room.
[0017] On a wet day for example if the outside air has a relative
humidity of 100%, raising the temperature of the outside air by
20.degree. C. will reduce the relative humidity of the air stream
to 25%. A relative humidity of 25% would be generally accepted to
be desirable for a construction site, being neither too moist and
thus promoting mold growth, nor too dry such that sensitive
materials such as flooring and millwork would be adversely
affected.
[0018] The amount of heat required to achieve the desired
temperature rise will depend on the volume of air drawn into the
air stream, which could be varied by increasing or decreasing the
fan speed. In any event, the relative humidity can be sensed at the
air outlet, and the amount of heat supplied then varied to achieve
the desired relative humidity of the outside air stream at the
output. Alternatively, the humidity and temperature could be sensed
at the intake, and the temperature sensed at the outlet. The
required adjustment in the amount of heat supplied could be
calculated, given the relative humidity of the outside air being
drawn in, by determining the temperature rise required to achieve
the desired relative humidity of the air stream at the outlet.
[0019] Depending on the volume of the air stream and the size of
the enclosed space, the relative humidity of the air inside the
enclosed space will be reduced over some period of time as the
dryer air stream pushes wetter air from inside the enclosed space
out through open windows, doors, exhaust vents, or the like. The
relative humidity of the inside air could also be sensed directly
to control the temperature rise supplied by the heat source. Care
should be taken however, since using such a direct control in a
relatively large enclosed space could result initially in over
drying of the air stream that could adversely affect materials near
the outlet of the air stream.
[0020] Larger spaces present particular problems for drying by
flushing dry air through the space and exhausting wetter air
through a vent. In a larger space there is typically some distance
between the location of the dry warm incoming air and the exhaust
location. As the dry warm air moves through the space it absorbs
moisture and the relative humidity of the air increases and reduces
its ability to absorb further moisture. Further, as the air absorbs
water, the phase change from liquid water to gaseous water vapor
absorbs heat, reducing the temperature of the air and further
increasing the relative humidity. Thus those areas near the wet air
exhaust will experience less drying than areas near the dry air
input.
[0021] Often buildings being dried are not well sealed, such that a
considerable amount of air leaves the building through seams in the
walls, or like leaks rather than through the vent. In areas near
where such leakage is significant, over-drying can occur as the
flow of air though the area is increased compared to other areas of
the building.
[0022] Larger spaces also typically include areas or zones that are
separated for example by walls into rooms, by shelves of stored
goods such as in warehouses, by floors in multi-story buildings,
and other like obstructions to airflow through the space. Such
obstructions create uneven air circulation and result in uneven
humidity in the space, and thus uneven drying. The various zones of
a larger space typically include areas that are wetter for one
reason or another. During construction for example, certain
procedures may be taking place in one zone that create
significantly higher humidity than in others, such as crack filling
drywall with drywall mud. Similarly where a building has been
flooded, certain parts of the building will typically be wetter
than others.
[0023] In order to provide more efficient and even drying, and to
reduce the possibility of over-drying, the method of the present
invention provides a plurality of portable heat exchanger units
comprising a fan drawing air from an intake through a heating
element and then out through an air output. The heating elements
could be electrically powered, however a typical application will
usually comprise a fluid coil connected to a fluid heater by
conduits such that heated fluid circulates through the fluid coil.
A heat controller on the unit is operative to increase or decrease
the flow of heated fluid through the coil, and thus control the
temperature rise between the air at the intake and that at the
output.
[0024] Outside air heat exchanger units are configured to draw in
outside air and direct a stream of warmed outside air with reduced
relative humidity into the space to be dried. A further number of
inside air heat exchanger units are distributed inside throughout
the space to be dried. Each inside unit includes a humidity sensor
connected to the heat controller to control the amount of heat
added to the air drawn through the unit, and thus control the
temperature rise of the air and the relative humidity thereof. The
inside air heat exchanger units are set to create an air stream at
the air output with a desired relative humidity level, typically
25-30% to provide effective drying without over-drying. The heat
controller is operative to add sufficient heat to the air drawn in
the intake thereof to reduce the relative humidity of the air
stream at the air output to the desired level.
[0025] The inside air heat exchanger units are spaced generally
evenly throughout the space to be dried. Due consideration may be
given to any particular circumstances of the space being dried,
such as larger or smaller rooms, wetter and drier areas, and like
considerations but generally the object is to have portable heat
exchanger units distributed throughout the space such that each
draws in air from around its location and discharges the air stream
back into the location.
[0026] The inside air heat exchanger units thus operate to bring
the relative humidity of the air in the zones in which they are
located to the desired level. As a particular zone dries, the
relative humidity of the air in the zone will decrease and the
amount of heat needed to bring the air stream at the output of that
unit to the desired relative humidity will decrease. When the
relative humidity in the zone reaches the desired level, the heat
controller will stop the flow of heated fluid to that unit.
[0027] The fans in the heat exchanger units will cause air to move
throughout the building, such that air from one zone intermingles
with air from another but the system operates such that the air in
any one zone or area is brought down to the desired level, but no
lower. At that time the fan will simply circulate the air until the
relative humidity of the air in the zone rises again due to
movement into the zone of wetter air from another zone. At that
time the humidity sensor will sense that the relative humidity has
risen, and call for heat to again reduce the relative humidity of
the air stream to the desired level.
[0028] Thus the method of the present invention substantially
prevents over-drying in one area or zone of a space being dried. In
addition to damaging sensitive materials, over-drying wastes energy
by expending heat energy to reduce the relative humidity of an area
below what is desired or required for drying. The method of the
present invention reduces energy costs by distributing heat only to
those zones where it is required to reduce the relative humidity to
the desired area.
DESCRIPTION OF THE DRAWINGS:
[0029] While the invention is claimed in the concluding portions
hereof, preferred embodiments are provided in the accompanying
detailed description which may be best understood in conjunction
with the accompanying diagrams where like parts in each of the
several diagrams are labeled with like numbers, and where:
[0030] FIG. 1 is a schematic side view of a portable heat exchanger
unit for use in the method of the invention, wherein the heating
element thereof is a fluid coil;
[0031] FIG. 2 is a schematic side view of an alternate portable
heat exchanger unit for use in the method of the invention, wherein
the heating element thereof is an electric element;
[0032] FIG. 3 is a schematic plan view of a building interior with
portable heat exchanger units configured to practice a method of
the invention;
[0033] FIG. 4 is schematic plan view of a fluid heater and conduits
connecting the fluid heater to the portable heat exchanger units of
FIG. 3;
[0034] FIG. 5 is a schematic plan view of an alternate building
interior with portable heat exchanger units configured to practice
a method of the invention.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS:
[0035] FIGS. 1 and 2 schematically illustrate portable heat
exchanger units 5, 105 each comprising a fan 7 operative to create
an air stream 9 by drawing air from an intake 11 and discharging
the air through an outlet 13. A heating element 15 is located in
the air stream 9 and a heating source is connectable to the heat
exchanger unit 5 to supply heat energy to the heating element 15 in
response to directions from a heat controller 17. The heat
exchanger unit 5 comprises a humidity sensor 19 placed at a sensing
location where it is operative to sense the relative humidity of
the air stream 9 and send a humidity signal to the heat controller
17. The heat controller 17 is operative to receive the humidity
signal and change the amount of heat energy supplied to the heating
element 15 in response to the humidity signal. Portability is
provided by wheels or the like as illustrated.
[0036] In the embodiment of FIG. 1, the heating element 15
comprises a fluid coil 30 and the heating source is a fluid heater
31 connectable to the fluid coil 30 by conduits 33 such that heated
fluid flows from the fluid heater 31 through the fluid coil 30 and
back to the fluid heater 31. The fluid heater 31 is conveniently a
water heater or boiler system set up at a central and connectable
to a plurality of portable heat exchanger units 5. The flow of
heated fluid through the coil 30 is controlled by a heat controller
17 which is operative to direct fluid from the fluid heater 31
either through the coil 30 or back to the fluid heater 31.
[0037] FIG. 2 illustrates an alternate embodiment of a heat
exchanger unit 105 wherein the heating element 15 comprises an
electric heating element 21 and the heating source is an electrical
power outlet connectable to the electric element by a power cord in
a conventional manner. The illustrated portable heat exchanger unit
105 also includes a fan controller 8 operative to change the speed
of the fan 7 to vary the volume of air in the air stream 9. The fan
controller can be manually controlled, or connected to receive the
humidity signal, temperature signals or the like and programmed to
vary the fan speed in response to information received. Thus both
the volume and relative humidity of the air stream 9 can be varied
in response to the humidity signal.
[0038] Raising the temp of air 10.degree. C. will reduce the
relative humidity of the air by about 50%. By sensing the relative
humidity of the air stream 9 the heat controller 17 can be operated
to supply heat at the proper rate to achieve the desired relative
humidity in the air stream 9. Alternatively, temperature sensors
could be provided and the humidity and temperature of the air
coming into the unit 5 could be sensed at the intake 11, and the
temperature of the air stream 9 sensed at the outlet 13. The
required adjustment in the amount of heat supplied could be
calculated, given the relative humidity of the air being drawn in,
by determining the temperature rise required to achieve the desired
relative humidity of the air stream 9 at the outlet.
[0039] FIGS. 3 and 5 schematically illustrate a plurality of
portable heat exchanger units 5 set up in buildings 40 and 41, each
enclosing an interior space that requires drying, in configurations
to practice the method of the invention for drying an enclosed
space. The buildings 40, 41 may have been flooded from rising
waters outside the building or by a water leak inside the building.
The buildings 40, 41 may also require drying due to construction
activities being carried on inside the building, such as
plastering, pouring concrete or like activities that generate
undesirable elevated moisture levels in the building.
[0040] Heated fluid flows to the portable heat exchanger units 5
through conduits 33 from a central fluid heater 31. The portable
heat exchanger units 5 are connected in parallel with the supply
conduits 33 as schematically illustrated in FIG. 4 and heat
controllers 17 control the amount of heated fluid flowing through
the fluid coil of each unit 5. The fluid heater 31 is typically set
to provide heated fluid at the supply port 35 thereof at a
pre-determined supply temperature. The heated fluid circulates
through the coils of the portable heat exchanger units 5 and the
heated fluid returns to the return port 37 of the fluid heater 31
at a reduced return temperature, is heated by the fluid heater to
the supply temperature, and is pumped out the supply port to
circulate again.
[0041] In order to provide drying of the building interior, it is
necessary to draw in outside air from outside the building and
allow an amount of air substantially equal to the amount of air
drawn from outside to exhaust from the building interior through a
vent 42. Commonly, the outside air will have a relative humidity
level that is above a level that will provide effective drying, and
so it is necessary to reduce the relative humidity of the air drawn
into the building to a level of about 25%-30%. Air at these
relative humidity levels provides a significant relative humidity
difference between the air stream and liquid water in wet plastered
walls, flooded areas, and the like, such that effective drying can
be accomplished and yet over-drying is prevented. The drier the air
the greater the moisture gradient between water and the air, and
the faster the air will absorb moisture.
[0042] In order to reduce the relative humidity of the air drawn
into the building, portable heat exchanger units 5 are positioned
as outside air units SA with the intakes 11 A thereof oriented to
draw air from outside the building 40 and with the outlets 13A
thereof oriented to discharge the air streams 9A thereof into the
building interior.
[0043] Drying can be accomplished by simply drawing in the outside
air and discharging it into the building interior at one or more
locations as an air stream with the desired relative humidity, and
then exhausting the air from the building interior at another
location such that the dry air streams 9A move through the building
absorbing moisture and then move out the exhaust as a wetter air
stream.
[0044] As the dry air streams 9A move through the building interior
toward the vent 41, they absorb moisture which raises the relative
humidity thereof and reduces the moisture gradient between the air
in the building interior and water in the building, and thus
reduces the ability of the air to dry the building by absorbing
water. When water is absorbed by the air it changes phase from a
liquid to gaseous water vapor, a process which absorbs heat, and
thus the air also cools as it moves through the building interior
and absorbs water. Since the relative humidity of air rises when
the temperature cools, the drying effectiveness of the air stream
is reduced by the cooling effect as well as the fact that the
relative humidity is rising because the air is absorbing water from
the building interior. In such a system then the relative humidity
of the exhaust air leaving the vent 42 has a higher relative
humidity and lower temperature than the incoming air stream 9A.
[0045] The drying effect in such a system is thus uneven since air
nearer the intake has a lower relative humidity than air near the
vent 42. This uneven drying is exacerbated in a building interior
such as that illustrated in FIG. 3 that is divided into various
rooms, and results in over-drying in some areas or zones of a
building interior, and increased drying times in other zones.
Similar obstructions to air flow are presented by goods stacked in
a warehouse, for example and like situations. While air circulation
can be improved by providing a fan or like means to circulate air
into and out of the rooms, air circulation is reduced in the
individual rooms, in particular those rooms that do not include a
vent.
[0046] The present invention therefore provides a plurality of
portable heat exchanger units 5 positioned as inside air units 5B
at spaced apart unit locations inside the building interior. The
intake 11 of each inside air unit draws air from the building
interior adjacent to the inside air unit and discharges an inside
air stream 9B through the outlet 13 into the building interior
adjacent to the inside air unit. A humidity sensor on each unit 5B
senses the relative humidity of the air stream 9B and sends a
signal to the heat controller of the unit such that the flow of
heated fluid through the coil is sufficient to reduce the relative
humidity of the inside air stream 9B to reduce the relative
humidity of the air stream to a desired relative humidity,
typically 25%-30%.
[0047] Thus each inside air unit 5B controls the relative humidity
of the air in a zone comprising the immediate vicinity of the unit.
In the configuration of FIG. 3, zones are fairly well defined by
the rooms into which the building interior is divided. Two inside
air units 5B are positioned in the larger room 44, and to dry a
smaller room 46 one of the inside air units 5B is oriented to
direct its air stream 9B into the room 46 through the bottom of a
door forcing air in the room out through the top of the door.
[0048] In operation, the fans are operated and heated fluid is
circulated from the fluid heater 31 through the coil of each
portable heat exchanger unit 5. The outside air units 5A reduce the
relative humidity of the outside air to the desired level by
heating the air stream, and direct the outside air stream 9A into
the building interior. Each inside air unit 5B operates to reduce
the relative humidity of the inside air streams 9B. The inside air
will circulate from one zone to another, however at each inside air
unit 5B, there will be created an inside air stream 9B with the
desired relative humidity. When the relative humidity of the air
being drawn into one of the inside air units 5B decreases, less
heat will be required to reduce the relative humidity of the air
stream 9B to the desired level and the heat controller will reduce
the flow of heated fluid to the coil of the unit. Since less heat
is being drawn from the circulating heated fluid, the return
temperature of the heated fluid will increase, and the heat
required to be generated by the fluid heater to heat the return
fluid to the supply temperature will be reduced.
[0049] For example, in FIG. 3 one room may dry faster than another
such that the relative humidity of the air in the room reaches the
desired level, and the air entering the intake 11 of the inside air
unit will not require any heating to maintain the air stream 9B at
the desired level. The heat controller will cut off all flow of
heated fluid through the coil. The fan however will continue to
operate, and air will circulate and some of the air from the room,
at the desired relative humidity level, will move out of the room
and other air from the building interior, at a relative humidity
level above the desired level, will move into the room, raising the
relative humidity level such that the air drawn in by the unit 5B,
and also the air stream 9B, will have a relative humidity above the
desired level. As the relative humidity of the air stream 9B
increases, the heat controller will direct heated fluid through the
coil to again reduce the relative humidity of the air stream 9B to
the desired level.
[0050] Thus at substantially all times in every zone of the
building interior air at the desired relative humidity level is
discharged from each inside air unit 5B. When one zone is dry such
that the air there is at the desired level of relative humidity,
heat to the inside air unit in that zone is cut off. Thus as each
different zone of the building interior dries, the relative
humidity decreases in each zone and progressively less heat is
required from the fluid heater. Circulating air moves from one zone
to the next, but by sensing the relative humidity of each air
stream 9B the system automatically compensates and works toward
reducing the relative humidity of the entire interior of the
building to the desired relative humidity. Once that is achieved,
drying is generally complete.
[0051] During the drying process using the method of the invention,
as air moves from the outlets of the outside air units 5A through
the wet building interior to the vent 42 it will absorb moisture,
however the relative humidity of the air throughout the building
interior is maintained at substantially the same desired level by
the inside air units 5A. The exhaust air stream 9C leaving through
the vent 42 thus has substantially the same relative humidity as
the incoming air streams 9A. but it carries substantially more
water because the temperature is higher. Each inside air unit
raises the temperature of the air to reduce the relative humidity,
but as the air absorbs moisture, the temperature thereof must be
increased to reduce the relative humidity to the desired level.
[0052] Thus for example the outside air stream 9A entering the
building interior might be at 25.degree. C. and a relative humidity
of 30%. The exhaust air stream 9C might be at 35.degree. C. and a
relative humidity of 30% which corresponds to about 60% relative
humidity at 25.degree. C. The exhaust air stream is thus carrying
significantly more moisture than the incoming outside air stream
9A, and thus is carrying water out of the building interior and
causing same to dry.
[0053] The building 41 illustrated in FIG. 5 shows a fairly large
open space that is divided into nominal zones 47, as illustrated by
the phantom lines, with an inside air unit 5B in each zone. The
zones 47 are determined by substantially equally dividing the
building interior, and may also take into account areas that are
wetter or drier than others. The zones 47 can be smaller where the
area encompassed by the zone is wetter, and larger where the area
is drier. The vent 42 can be located in a drier corner of the
building interior where slower drying could be acceptable. Those
skilled in the art will recognize that various conditions can be
considered when dividing the building interior into zones.
[0054] The method of the invention provides increased efficiencies
of operation, and reduced capital equipment costs. For example in
the configuration of FIG. 5 the portable heat exchanger units 5
could each have a rated heat output of 65,000 BTU/hour, and the
fluid heater could be a water heater with a rated maximum heat
generating capacity of 800,000 BTU/hr. At initial start up of the
portable heat exchanger units 5 in a wet building interior and
where the outside relative humidity is high, the heat controller on
each unit could be operating to direct all available heated fluid
through the coil of each unit. There are 4 outside air units 5A and
10 inside air units 5B, for a total of 14. Each has a rated output
of 65,000 BTU/hr for a total of 910,000 BTU/hr, while the fluid
heater can only generate 800,000 BTU/hr. Thus the heated fluid at
the supply port of the fluid heater will not attain the rated
supply temperature, and each portable heat exchanger unit will
operate at somewhat less than capacity, but drying will begin to
take place. The desired relative humidity of, for example 25%, may
not be attained in each zone immediately, and the air streams 9B
may have a relative humidity of 28% instead, a level at which
drying is still effective.
[0055] As the relative humidity of the air in a zone begins to go
down, the amount of heat drawn by the inside air unit 5B in that
zone will be reduced, the supply temperature will rise, and more
heat will be available where it is needed. As further zones dry and
call for reduced heat, the inside air units 5B in those zones that
are wettest will receive the rated heat and operate to reduce the
air flowing through them to the desired level. Thus the system can
supply the available heat to each unit 5B equally, and then, as
more heat becomes available because of a reduced demand for heat in
one zone, that heat is directed to those zones calling for more
heat. A smaller capacity fluid heater 31 can thus effectively
provide well distributed heat to dry the building interior.
[0056] The system may be configured such that the outside air units
5A have a priority by increasing the set point for the heat
controllers at one or more of the inside air units from 25% to 30%
so that the inside air units do not initially call for as much
heat, and there will be sufficient heat available to reduce the
relative humidity of the outside air streams 9A to the desired
level of 25%. As the heat requirement goes down during drying, the
set points can be changed to the desired level.
[0057] The set point for the desired relative humidity of the air
streams 9A and 9B can be varied according to conditions from the
typical level of 25%-30%. Where materials are present in the space
to be dried that are very sensitive to over-drying the relative
humidity of the incoming air stream might be increased, and where
over-drying is not a particular concern the relative humidity can
be decreased.
[0058] The invention thus provides a method for controlling
humidity in each of a plurality of zones of an enclosed space
during a drying process. The method comprises in each zone, drawing
air from the zone to create an air stream through a heating element
and discharging the air stream into the zone; sensing the relative
humidity of the air in a sensing location in the zone; in response
to the relative humidity sensed at the sensing location, operating
the heating element to raise a temperature of the air stream as
required to reduce the relative humidity of the air in the zone to
a desired relative humidity.
[0059] Conveniently the sensing location is located to sense the
relative humidity of the air stream 9 after the air stream passes
through the heating element 15, providing a direct measurement of
the relative humidity of the air stream 9. A portable heat
exchanger unit 5, 105 can be provided in each zone, with a humidity
sensor 19 mounted on the portable heat exchanger unit to sense the
relative humidity of the air stream 9 as it is discharged through
the outlet 13, and a heat controller 17 operative to change the
amount of heat energy supplied to the heating element 15 in
response to the humidity signal.
[0060] The foregoing is considered as illustrative only of the
principles of the invention. Further, since numerous changes and
modifications will readily occur to those skilled in the art, it is
not desired to limit the invention to the exact construction and
operation shown and described, and accordingly, all such suitable
changes or modifications in structure or operation which may be
resorted to are intended to fall within the scope of the claimed
invention.
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