Improvements in Heating or Cooling Air, and in the Method of Applying such Air for Drying, Heating, Cooling, and other purposes.
Year: 1897

page_text: Date of Application, 9th Apr., 1897
Complete Specification Left, 10th Jan., 1898-Accepted, 5th Mar., 1898
PROVISIONAL SPECIFICATION.
Improvements in Heating or Cooling Air, and in the Method of
Applying such Air for Drying, Heating, Cooling, and other
purposes.
I, JAMES GARDNER CALVERT, of 38 Kyrkogatan, Gothenburg, in the Kingdom of
Sweden, Engineer, do hereby declare the nature of this invention to be as follows:
-
According to the method at present in general use for heating air and applying
the same for drying, heating, and other purposes, the air to be heated is first brought
into contact with a surface heated by steam, by the hot products of combustion of
fuel or otherwise, by means of a fan, air pump, or other appropriate means whereby
its temperature is raised, it is then passed into the room, chamber or stove where
the drying, heating or other required effect is to be produced, and is then discharged
into the outer atmosphere. As in this method, especially when applied to drying
purposes, the air is generally discharged into the atmosphere after having been
passed once only in contact with the heating surface and with the objects upon
which its drying effect is to be exerted, it is necessary to regulate the quantity of
air passed through in a given time so that on the one hand it shall take up the
maximum of humidity from the objects to be dried, and on the other hand shall
not be allowed to escape at too high or too low a temperature. The result of this is,
in many cases, that the air has to be passed comparatively slowly over the heating
surface, and inasmuch as the heating effect of such surface per unit is largely
dependent upon the quantity or weight of air brought into contact with it in a
given time, the quantity of heating surface required to produce a given heating
effect has hitherto been considerable because of the comparatively small weight
of air that it has been possible, under the above conditions, to bring into contact
with it per unit of surface and per unit of time. The chief object of my present
invention is to provide means whereby the required effect can be obtained with
very much less heating surface in the battery of heating pipes or other heating
surfaces than has been required heretofore, and in some cases the drying effect,
as in the case of timber drying for example, can be carried on and completed at a
lower temperature than usual, whereby cracking and warping of the timber is to
a large extent prevented, and in other cases, such as the drying of yarns the
work can be greatly accelerated by the rapid circulation of the air.
For these purposes instead of passing the air once over the heating surface, then
through the drying room or stove, and allowing it to escape continuously from the
latter as heretofore, I take in a charge of air from the atmosphere, pass it over the
heating surfaces and through the drying room or stove, thence back to the heating
surfaces, then to the drying room or stove again, and so on continuously until it
has attained the desired temperature, and has become as fully saturated with
moisture as is consistent with obtaining an economical effect; I then allow that
charge of air to escape and take in a fresh charge which I treat in the same way,
and so on continuously. By this means I bring in contact with the heating
surfaces in a given time a. quantity or weight of air which may be many times as
great as that brought into contact with them under the method at present in use;
and the consequence is that each unit of such surface is made to produce a much

page_text: greater heating effect than heretofore, and the total surface may therefore be
materially reduced without reducing the result in the drying room or stove, or a
better result can be obtained with the same heating surface. Another result of
my improved method is that, by reason of the more rapid circulation of the heated
air through and among the objects to be dried, the average temperature may be
materially reduced, and not only a corresponding economy of fuel secured, but in
many cases a great acceleration of the drying process can be obtained.
The same method, or a modification thereof, is applicable to the heating of rooms,
mills, manufactories and so forth, and for this purpose I use a fan or other suitable
device, for moving air, or a series of such fans or devices of sufficient capacity to
circulate the quantity of air to be heated, several times over the heating surfaces
until it has attained the desired temperature. I at the same time allow the air inlet
from the outer atmosphere to the fan to remain open, and I open the air outlet from
the heating surfaces to the room to be warmed just sufficiently to allow a portion only
of the warmed air to escape to the latter, the amount of the opening being regulated
according to the temperature desired. I provide a bye-pass through which the air
which does not escape through the aforesaid opening returns to the inlet of the fan,
and is again passed over the heating surfaces and so on continuously, a quantity of air
from the atmosphere being drawn into the fan through the aforesaid inlet opening
equal to that discharged through the outlet into the room to be heated. In this
case the power required to drive the fan moving the comparatively large volume
of air is economised to a considerable extent by the plenum of air returning to the
fan neutralizing the partial vacuum which the fan would otherwise produce.
I sometimes arrange the apparatus with two or more sets of heating surfaces
or batteries of pipes, each having its own fan or other device for moving the air,
and each fan and battery having its own bye-pass for the return of part of the air
to the inlet of the fan, while each fan delivers the rest of its air to the next fan
and battery in succession so as to work the air at a succession of temperatures, the
outlet from the last battery to the room being adjustable so as to regulate the
supply of heated air to the room, and consequently the amount of air flowing
through the entire system of fans and batteries.
It is obvious that the above described improvements are equally applicable to
cases where the air is to be cooled instead of heated, as for example in the case
of cold stores for the preservation of food, where the air is brought into contact
with pipes or other vessels through which cold brine or other refrigerating agent
circulated.
1 .
1
A
1 1007
J. G. CALVERT,
Per W. H. Beck, Agent.
115, Cannon Street, London, E.C.
COMPLETE SPECIFICATION.
Improvements in Heating or Cooling Air, and in the Method of
Applying such Air for Drying, Heating, Cooling, and other
purposes.
I, JAMES GARDNER CALVERT, of 38 Kyrkogatan, Gothenburg, in the Kingdom of 4
Sweden, Engineer, do hereby declare the nature of this invention, and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement: —
According to one method at present in general use for heating air and applying
the same for heating rooms, mills, or manufactories, drying materials, and so forth,

page_text: the air to be heated is first brought into contact with a surface heated by steam,
by the hot production of combustion of fuel, or otherwise, by means of a fan, air-
pump or other appropriate means, whereby the temperature of such air is raised
and the air is then passed into the room, chamber, stove or other space where the
drying, heating or other required effect is to be produced, and is then discharged
into the outer atmosphere. As in this method especially when applied to drying
purposes the air is generally discharged into the atmosphere after having been
passed once only in contact with the heating surface and with the objects upon
which its drying effect is to be exerted it is necessary to regulate the quantity of
air passed through in a given time so that on the one hand it shall take up the
maximum of humidity from the object to be dried, and on the other hand shall
not be allowed to escape at too high or too low a temperature, and shall remain in
contact with the heating surfaces a sufficient time to become heated to the required
extent. The result of this is, in many cases, that the air has to be passed com-
paratively slowly over the heating surfaces, and inasmuch as the heating effect of
such surfaces per unit is largely dependently upon the quantity or weight of air
brought into contact with them in a given time the quantity of heating
surface required to produce a given heating effect has heretofore been
considerable because of the comparatively small weight of air that it
has been possible, under the above conditions, to bring into contact with it
per unit of surface and per unit of time. The chief object of my present inven-
tion is to provide means whereby the required effect can be obtained with very much
less heating surface in the battery of heating pipes or other heating surfaces than
has been required heretofore, and in some cases, the drying effect, as in the case
of timber drying, for example, can be carried on and completed at a lower tempera-
ture than usual, whereby cracking and warping of the timber is to a large extent
prevented, and in other cases such as in the drying of yarns the work can be greatly
accelerated and in most cases the desired effect can be obtained with economy of
fuel.
For these purposes I use a fan or other suitable device, for moving air, or a series
of such fans or devices of sufficient capacity to circulate the quantity of air to be
heated, several times over the heating surfaces until it has attained the desired
temperature. I at the same time allow the air inlet from the outer atmosphere to
the fan to remain open, and I open the air outlet from the heating surfaces to the
room to be warmed just sufficiently to allow a portion only of the warmed air to
escape to the latter, the amount of the opening being regulated according to the
temperature desired. I provide a bye-pass through which the air which does not
escape through the aforesaid opening returns to the inlet of the fan, and is again
passed over the heating surfaces and so on continuously, a quantity of air from the
atmosphere being drawn into the fan through the aforesaid inlet opening equal to
that discharged through the outlet into the room to be heated. In this case the
power required to drive the fan moving the comparatively large volume of air is
economised to a considerable extent by the plenum of air returning to the fan
neutralizing the partial vacuum which the fan would otherwise produce.
I sometimes arrange the apparatus with two or more sets of heating surfaces
or batteries of pipes, each having its own fan or other device for moving the air,
and each fan and battery having its own bye-pass for the return of part of the air
to the inlet of the fan, while each fan delivers the rest of its air to the next fan and
battery is succession so as to work the air at a succession of temperatures, the outlet
from the last battery to the room being adjustable so as to regulate the supply
of heated air to the room, and consequently the amount of air flowing through
the entire system of fans and batteries.
The accompanying drawing shows diagrammatically, and partly in section, an
air-heating apparatus constructed in accordance with my invention.
A is a closed chamber containing a battery of pipes B heated by steam or other-
wise in the usual way. In the example shown the air is caused to pass up and down
in contact with the pipes B by means of the partitions C. D is a fan or other

page_text: suitable device for moving air, of sufficient capacity to circulate the quantity of
air to be heated, several times over the heating surfaces B before it passes away to
the room or space to be heated, E is an inlet pipe for admitting air from the outer
atmosphere to the fan D. This pipe E is provided with a valve F by means of
which the quantity of air admitted to the fan can be regulated as required. Gis
the air delivery pipe from the fan D to the chamber A. H is the air outlet pipe
from the chamber A leading the air therefrom to the room or space to be heated,
and I is a bye-pass pipe leading from the outlet pipe H back to the inlet pipe J
of the fan D. K is a valve in the outlet pipe H, and L a similar valve in the
bye-pass pipe I which valves may be employed or not according to circumstances.
It will now be understood that if the valves F, and K, be closed and the valve L
to be opened, and the fan D set in motion, air will be drawn from the chamber A
through the outlet pipe H, bye-pass pipe I, and pipe J to the fan D and forced
from the latter through the pipe G back to the chamber A, and up and down
through the latter in contact with the heating pipes B, thence by the pipes H, I
and J back to the fan D, and so on round and round until it is heated to the required
degree. If now the valve F be opened to admit a supply of air from the outer
atmosphere to the fan, and the valve K sufficiently to allow a portion only of the
warmed air to escape through the pipe H to the room or other space to be heated,
the amount of the opening of the valve K being regulated according to the tempera-
ture desired and the valve L being partially closed to assist this object the air which
does not escape through the valve K returns to the inlet J of the fan along with a
quantity of air from the atmosphere drawn in through the valve F equal to that
discharged at K into the room or other space to be heated, and is again passed
through the heating chamber A. By this means a large volume, and consequently
a great weight of air, is kept constantly circulating round and round in contact
with the heating surfaces, a portion only of such air escaping in a given time to
the room or other space to be heated, and a corresponding quantity of fresh air from
the outer atmosphere being drawn in at the same time.
It will also be understood that the power required to drive the fan D moving the
comparatively large volume of air is economised to a considerable extent by the
plenum of air returning to the fan through the bye-pass I neutralizing to a certain
extent the partial vacuum which the fans tend to produce.
The apparatus may be arranged with two or more sets of heating surfaces or
batteries of pipes, each having its own fan or other device for moving the air,
and each fan and battery having its own bye-pass for the return of part of the air
to the inlet of the fan, while each fan delivers the rest of its air to the next fan
and battery in succession, so as to work the air at a succession of temperatures;
the outlet from the last battery to the room being adjustable so as to regulate the
supply of heated air to the room or other space to be warmed, and consequently
the amount of air flowing through the entire system of fans and batteries.
The dotted lines in the drawing represent a second apparatus consisting of a
battery of heating pipes or other heating surfaces A¹ B¹, a fan D¹ and a bye-pass I'
connected to the outlet pipe H of the apparatus shown in full lines and arranged to
be worked in the manner last above described, the valves K¹ and L' serving to
regulate the quantity of air passing from the combined apparatus to the room or
other space to be warmed.
It is obvious that the above described improvements are equally applicable to
cases where the air is to be cooled instead of heated, as for example in the case of
cold stores for the preservation of food, where the air in brought into contact with
pipes or other vessels containing brine or other refrigerating agent or through
which a refrigerating agent is circulated.*
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, I declare that what,
I claim is:
First. The improved method of heating or cooling air which consists in causing

page_text: a quantity of air to circulate round and round in contact with heating or cooling
surfaces, and in allowing such air, so heated or cooled, to escape from the apparatus
to the room or space to be heated or cooled at a slower rate than that at which the air
is circulated in contact with the heating or cooling surfaces, substantially as
described.
Second. The modification of the method forming the subject matter of the first
claiming clause hereof in which the air is treated by a succession of operations of
the kind claimed in the said first claiming clause, substantially as described.
Third. Apparatus for carrying out the method forming the subject matter of
the first and second claiming clauses hereof, which consists of heating or cooling
surfaces B enclosed in a casing A, a fan D or other suitable device for moving air,
a bye-pass pipe or passage I between the inlet and outlet passages of the air-moving
device, and regulating valves, F, K, and L, combined and operating, substantially
as described.
Fourth. The combination of two or more of the apparatuses forming the subject
of the third claiming clause hereof, so that the air is operated upon successively
by each such apparatus in turn, substantially as described.
Dated this 8th day of January 1890.
J. G. CALVERT,
Per W. H. Beck, Agent,
115, Cannon Street, London, E.C.
J. G. CALVERT,
Per W. H. Beck, Agent,
115, Cannon Street, London, E.C.

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