Tobacco barn with heat exchanger system

The present invention entails a heat exchanger system for a tobacco curing and drying structure that is designed to utilize the heat associated with exhaust air leaving the structure to heat fresh incoming air being directed into the structure. In particularly, the present invention entails a top mounted heated exchanger system including a pair of laterally spaced counterflow heat exchange modules connected to the barn and to a fresh air transfer duct that leads back into the curing and drying structure. Heated exhaust air is routed through the exchange modules before being exhausted to the atmosphere. Counterflowing, but separated, fresh air traveling through the same heat exchange modules is heated by the exhaust air before being introduced into the curing and drying structure.

FIELD OF THE INVENTION 
The present invention relates to tobacco curing and drying and more 
particularly to curing and drying structures having a heat exchange system 
associated therewith. 
BACKGROUND OF THE INVENTION 
Today, a majority of the flue cured tobacco crop is cured in a curing and 
drying structure that is typically referred to as a bulk barn. A bulk barn 
includes a curing and drying chamber or section and a furnace area that 
includes a fan. The fan functions to circulate air into the curing and 
drying chamber and vertically through the tobacco afterwhich the air is 
either exhausted or recirculated to the furnace area where it may be 
heated or not heated, depending on the temperature within the barn and the 
particular curing and drying phase. During certain periods of the curing 
and drying schedule, substantial quantities of moisture must be removed 
from the leaf. Thus, during the process, the heated air being circulated 
within the curing and drying structure becomes saturated or nearly 
saturated with moisture and accordingly to continue to be effective in the 
drying process, a certain portion of this moist air must be dumped or 
exhausted from the curing and drying structure. There is an abundance of 
energy in the form of heat associated with this warm moist air that is 
being exhausted from a tobacco barn, especially during the leaf drying 
period. This means that this energy is lost. With the cost of fuel 
continuing to rise and the cost of bulk tobacco barns continuing to 
increase, it is very important and beneficial to save as much fuel as 
possible in curing and drying tobacco and also to be able to cure and dry 
a certain size crop with a minimum number of barns. 
There have been attempts at incorporating heat exchangers into tobacco 
curing and drying structures. It has been recognized that the heat 
associated with the exhaust air from a curing a drying structure can be 
used to heat incoming fresh air. For example, there have been very 
simplistic approaches to this problem. Once such approach has been simply 
to dispose two ducts in side-by-side relationship about the end of a 
tobacco barn and to exhaust air through one such duct and route incoming 
fresh air through the other duct. In such a case, heat associated with the 
exhaust air to some extent at least, can be transferred to the incoming 
fresh air passing in the adjacent duct. Obviously, this is a very crude 
and inefficient system that has no flexibility whatsoever. 
In addition to the simplistic, there have been very complicated approaches 
to providing heat exchangers for tobacco curing and drying structures. In 
this regard, one is referred to U.S. Pat. No. 4,499,911 which discloses a 
solar tobacco barn having computer operated heat exchange system for a 
plurality of barns. The complexities and expense of this system are 
obvious from a review of the '911 patent. Again, the system disclosed in 
this patent is quite expensive and costly to maintain, but most 
importantly, the system is of the type designed to accommodate a series of 
six barns. Therefore, the system disclosed in the Johnson U.S. Pat. No. 
4,499,911, does not really address the real need of providing an 
effective, efficient, and reasonably priced heat exchanger for a single 
bulk curing barn. 
Beyond that, there are literally tens of thousands of barns existing on 
tobacco farms today that are owned by farmers struggling to make efficient 
use of their energy dollar. There are no heat exchanger kits or units 
commercially available that enable such a heat exchange system to be 
retrofited to a tobacco barn. 
SUMMARY AND OBJECTS OF THE INVENTION 
The present invention presents an efficient heat exchanger system for a 
tobacco curing and drying structure that can be either incorporated during 
the manufacture of a new bulk barn or can be retrofited to existing 
tobacco barns. The heat exchanger system of the present invention entails 
a pair of laterally spaced counterflow heat transfer modules that are 
mounted atop a conventional tobacco curing and drying barn. Each module 
includes a plurality of spaced apart conduits or channels that are 
designed to accommodate counter flowing fresh incoming air and heated 
exhaust air. The fresh incoming air that is heated by the exhaust air is 
directed and transferred into a main transfer or delivery duct that 
extends between the two exchange modules. This main fresh air transfer 
duct is communicatively connected to the curing and drying structure and 
functions to direct heated incoming fresh air into the curing and drying 
structure where that heated fresh air is circulated throughout the barn. 
It is therefore an object of the present invention to provide an effective 
and efficient heat exchanger system for a tobacco curing and drying 
structure. 
Another object of the present invention entails the provision of a heat 
exchanger system for a tobacco curing and drying structure that is 
particularly suited for use by a single bulk tobacco barn or curing a 
drying structure. 
Another object of the present invention resides in the provision of a heat 
exchanger system that is capable of being easily retrofited to an existing 
curing and drying structure. 
Still a further object of the present invention resides in the provision of 
a heat exchanger system that is capable of being retrofited to most, if 
not all, bulk tobacco barns. 
Another object of the present invention resides in the provision of a heat 
exchanger system for a tobacco curing and drying structure that is capable 
of substantial savings in fuel cost and in curing time. 
Another object of the present invention resides in the provision of a heat 
exchanger system that allows for relatively high flow rates of incoming 
fresh air that permits total curing and drying time to be reduced. 
It is also an object of the present invention to provide a heat exchanger 
system that is easily adaptable for use with a series of barns for the 
purpose of transferring energy or heat from one barn or another during 
various curing and drying schedules. 
A further object of the present invention resides in the provision of a 
heat exchanger system where a conventional bulk tobacco curing and drying 
structure that does not change the basic operating characteristic of the 
curing and drying structure. 
Still a further object of the present invention resides in the provision of 
a heat exchanger for a bulk tobacco curing and drying structure that can 
be moved from one curing structure to another. 
Other objects and advantages of the present invention will become apparent 
and obvious from a study of the following description and the accompanying 
drawings which are merely illustrative of such invention.

DESCRIPTION OF THE INVENTION 
With further reference to the drawings, the curing and drying structure of 
the present invention is shown therein and indicated generally by the 
numeral 10. Drying structure 10 is a conventional bulk tobacco barn. Such 
bulk tobacco barns are conventional and are presently commercially 
available. Therefore, a detailed description of such is not required and 
is not per say material to the present invention. For a complete and 
unified understanding of bulk tobacco barns, one is referred to the 
disclosures found in U.S. Pat. Nos. 3,105,713; 3,503,137; 3,937,227 and 
3,664,034, these disclosures being expressly incorporated herein by 
reference. 
Briefly describing the curing and drying structure or bulk tobacco barn 10 
shown in the drawings, the same includes a foundation slab 12 that 
supports a perforated floor 13 and wherein there is defined an air flow 
plenum 15 between the perforated floor 13 and slab 12. Formed about the 
front of the curing and drying structure 10 is one or more front doors 14. 
The curing and drying structure further includes a top 16 and a back 18. 
Formed internally within the curing and drying structure 10 is a front 
curing and drying chamber 20 that is adapted to receive and hold tobacco 
therein for curing and drying. Disposed rearwardly of the curing and 
drying chamber is a furnace room or area 22 that is separated from the 
curing and drying chamber 20 by a separating wall 28. Conventionally 
provided within the furnace room 22 is a furnace system 24 having a 
circulating fan 26. Formed in the separating wall 28 is a pair of 
recirculating static dampers 30 that function to control the volume and 
flow of air that is recirculated from the curing and drying chamber 20 to 
the furnace room 22 during the curing and drying process. 
It is appreciated that during the curing and drying process that fresh 
outside air is brought into the structure and circulated through the 
tobacco supported within the structure. To make room for the fresh 
incoming air, it follows that some existing air within the barn must be 
exhausted. This is especially true during drying portions of the curing 
and drying schedule because it is during this portion of the curing and 
drying schedule where substantial quantities of moisture are removed from 
the tobacco. To provide for an efficient drying process, it follows that 
one must continue to exhaust this moisture laden air so as to enable fresh 
air to be induced into the barn. In exhausting this moisture laden air, 
substantial energy is lost because such exhaust air has been heated and is 
relatively warm while the incoming fresh air is relatively cool and must 
be heated so as to maintain the temperature within the barn at a given 
scheduled drying temperature. 
In order to recapture heat associated with air that is being exhausted from 
the curing and drying structure 10, the present invention provides a heat 
exchanger system, indicated generally by the numeral 50, that is mounted 
on the top 16 of curing and drying structure 10. As will become apparent 
from subsequent portions of this disclosure, the heat exchanger system 50 
functions to transfer heat associated with air being exhausted from the 
curing and drying structure to fresh incoming air so as to effectively 
heat the same prior to the fresh incoming air entering the curing and 
drying structure. 
The heat exchanger system 50 comprises a pair of side-by-side counter flow 
heat exchanger modules 52 and 54. Each heat exchange module is of a 
rectangular elongated duct type design and includes a top 56, pair of 
sides 58 and a bottom 60. As seen in the drawings, each exchanger module 
52 and 54 is supported on top of the curing and drying structure 10 by a 
support structure. 
Viewing each exchanger module 52 and 54, it is seen that each comprises a 
series of spaced apart elongated panels 64 with the respective panels 
defining a series of spaced apart channels 66. As will be appreciated from 
subsequent portions of this disclosure, some of the channels 66 will be 
designated exhaust air channels while some will be designated as fresh or 
draft air channels. The exhaust air and fresh air channels are alternately 
spaced such that there will be streams of exhaust and fresh air flowing 
adjacent to each other but in counter directions. 
About a rear or first end portion of each exchanger module 52,54 is a fresh 
air inlet section indicated generally by the numeral 68. It is appreciated 
that the fresh air inlet section 68 is formed on the outside of each 
exchanger module 52,54. Essentially, fresh air inlet section 68 is open to 
fresh air inlet channels, referred to by 68a, formed within respective 
heat exchanger module 52 or 54. Consequently, every other channel 66 
extending across the fresh air inlet section 68 is a fresh air inlet 68a 
and is open to receive induced or draft fresh air. Secured to each heat 
exchange module 52 and 54 adjacent the fresh air inlet section 68 is a 
weather shield or shroud 69. Note that the weather shield or shroud 69 
extends downwardly over the fresh air inlet section and tends to prevent 
rain from being induced into the heat exchange modules 52 and 54. 
Formed about the opposite end of each heat exchanger module 52,54 is an 
exhaust air inlet section indicated generally by the numeral 70. It is 
appreciated from the drawings that exhaust air inlet section 70 extends 
transversely across the end of each heat exchanger module 52 or 54 and 
thus is disposed at a right angle with respect to the side disposed fresh 
air inlet section 68. In any event, exhaust air inlet section 70 is open 
to alternatively designated exhaust air channels 66 and is closed to 
channels designated as fresh air chambers. 
Formed about the inner side of each heat exchanger module 52 and 54 about 
the front end or end adjacent the exhaust air inlet sections 70, is a 
fresh air outlet section indicated generally by the numeral 72. Fresh air 
outlet section 72 provides an outlet in the appropriate designated fresh 
air channels 66 that permits the fresh air traveling towards the front of 
the curing and drying structure 10 to exit the heat exchanger modules 52 
and 54. Communicatively connected to both fresh air outlet sections 72 of 
the respective heat exchanger module 52 and 54 is a main fresh air 
transfer duct indicated generally by the numeral 74 which extends from a 
front portion of the curing and drying structure to the furnace area 22. 
Main fresh air transfer duct 74 includes an inlet end portion 74a that 
effectively connects to the fresh air outlet sections 72 of the respective 
heat exchange modules 52 and 54. In addition, main fresh air transfer duct 
74 includes an outlet end portion 74b that turns downwardly and extends 
through an upper opening in the furnace room 22 and terminates just above 
furnace system 24 and fan 26. 
In order to transfer exhaust air from the curing and drying chamber 20 to 
the respective heat exchanger modules 52 and 54, there is provided a pair 
of exhaust air transfer ducts 76. Note in the drawings that each exhaust 
air transfer duct 76 is communicatively connected with the curing and 
drying chamber 20 through an opening formed in the top 16 of the curing 
and drying structure 10. In addition, each exhaust air transfer duct is 
coupled directly to the end of the exhaust air inlet section 70 of each 
heat exchanger module 52,54. 
Secured to the opposite ends of each heat exchanger module 52 and 54 is an 
exhaust air discharged stack 78. It is appreciated that the discharge 
stack 78 is communicatively connected to the respective exhaust air 
channel 66 formed in the heat exchanger module thus resulting in the 
exhaust air being directed into the discharge stack 78 which results in 
the exhaust air being directed into the atmosphere. 
Fresh or draft air is induced into the fresh air inlet sections 68 and 
after entering the fresh air inlet sections, the air is turned 
approximately 90.degree. C. and travels down the heat exchanger modules 52 
and 54 towards the front of the curing and drying structure. It is thus 
appreciated that the fresh or draft air is moving within the heat 
exchanger modules 52 and 54 counter to the flow of the heated exhaust air. 
Because the fresh air and the heated exhaust air travel in alternately 
spaced channels 66, it is appreciated that efficient heat transfer occurs 
as the energy in the form of heat associated with the exhaust air is 
transferred through the elongated panels 64 to the fresh incoming air 
traveling in the dedicated fresh air channels. Once the fresh air reaches 
the forward portion of the respective heat exchanger modules 52 and 54, 
the fresh air is exhausted out the fresh air outlet section 72 into the 
main fresh air transverse duct 74 where the now heated fresh air is 
transferred into the furnace room 22 where fan 26 is operative to 
recirculate that air through the curing and drying structure. 
In order to control the flow of exhaust air and fresh air through the heat 
exchanger system of the present invention, there is provided a control 
damper 80 that is disposed in the terminal portion of the main fresh air 
transfer duct 74. An actuator assembly 82 is connected to the control 
damper 80 and extends from the rear of the curing and drying structure for 
convient access, allowing the farmer to manually control the flow of 
exhaust and fresh air through the heat exchanger system by simply 
adjusting the position of damper 80. Consequently, it is appreciated that 
the farmer can, from time to time, vary and control the flow of fresh air 
being induced into the barn 
The advantages of the heat exchanger system 50 of the present invention are 
many. First and foremost, it extracts energy from heated exhaust air that 
is being wasted to the atmosphere and transfers that energy in the form of 
heat to the incoming fresh air. This obviously means that the fresh 
incoming air is preheated prior to the time it is directed into the curing 
and drying structure and consequently less fuel is required to cure and 
dry a certain quantity of tobacco. Beyond that, greater drying efficiency 
is achieved by being able to increase the volume of fresh incoming air 
thereby expediting the drying process which consequently has the effect of 
shortening the drying period. This will enable a farmer to cure and dry a 
greater quantity of tobacco crop for a given number of tobacco barns. 
The present heat exchanger system for a tobacco curing and drying structure 
is very efficient and effective in conserving energy and expediting the 
curing and drying schedule. The design of a heat exchanger system is not 
complex and can be properly operated by farmers themselves. 
The present invention may, of course, be carried out in other specific ways 
than those herein set forth without departing from the spirit and 
essential characteristics of the invention. The present embodiments are, 
therefore, to be considered in all respects as illustrative and not 
restrictive and all changes coming within the meaning and equivalency 
range of the appended claims are intended to be embraced therein.