US3073296A - Furnaces - Google Patents

Description

Jan. 15, 1963 J. H. HOLLINGSWORTH ET AL 3,073,296

FURNACES 2 Sheets-Sheet 1 Filed Jur le 26, 1958 A TTORNEVS Jan. 15, 1963 J. H. HOLLINGSWORTH ETAL 3,073,296

FURNACES Filed June 26, 1958 l F/G. 2. V!

2 Sheets-Sheet 2 INVENTORS. JOHN H. hOLL/NGSWOQTH I54 LEO BLOCK m MM A T TORNE YS United States Patent 3,073,296 FURNACES John H. Hollingsworth, Altadena, and Leo Block, Los Angeles, Caiifi, assignors to The Siegler Corporation, Chicago, Ill., a corporation of Delaware Filed June 26, 1958, Ser. No. 744,753 2 Claims. (Cl. 126-110) This invention relates to forced air furnaces for use in dwellings and the like. The novel furnaces of the invention bring improved performance to a variety of forced air heating systems but are particularly useful when the systems are also used for air cooling by refrigeration.

This application is a continuation-in-part of our copending application Serial No. 617,408, filed October 22, 1956, now abandoned.

A conventional forced air heating system has a blower that forces air through a casing containing a hollow radiator in which fuel is burned. The air thus heated is driven from the casing through a duct system and discharged into one or more rooms. The thermal efficiency of such a system (i.e. the proportion of the heat generated by the fuel burned that is transferred to the air forced through the casing) is related to the velocity at which the air is forced through the casing. Generally, the greater this velocity, the greater the efficiency. However, there are limitations on such velocity. If the velocity is too high, the air rushing through the casing produces excessive noise. Secondly, as velocity is increased the motors and blowers required to attain the increase become more expensive to build and to operate, thus imposing an economic limitation. A third limitation is imposedby the American Gas Association, which requires that the air passing the radiator be heated above a temperature that would allow water vapor to condense in the furnace or in the flue and thus cause corrosion in either place. The furnaces may be designed to give such a high air velocity that the flue temperatures and the temperature rise of theair flowing past the radiator are both so low that designed.

It has been proposed to modify forced air heating systems by placing a cooling coil in series with the furnace of the" system so that in Warm weather the blower and duct work of the system canbe used to convey cooled air to the rooms. The proposal is attractive from the stand point of economy of structure. Unfortunately, forced air furnaces that are designed as described above to give acceptable thermal efficiency and also avoid moisture condensation and excessive noise are not suitable for use with a refrigerating unit in series, and attempts tomodify forced air systems containing such furnaces by theaddition of an air cooling unit have resulted in systems that .are not satisfactory for heating or cooling.

. Many builders install forced air heating systems in newhomes'andattempt to make provision for later installation of a cooling unit in series with the furnace to provide year round air conditioning. But when the home ownermfi for cooling. The home owner discovers that the motor "ice and blower installed in the system, although adequate for operation when the system is employed for heating, are not large enough to supply the increased volume of air required when cooling is to be accomplished, or even to overcome the increased resistance to air flow which is represented by the cooling element. By way of example, a forced air heating system with a rating of 100,000 B.t.u. per hour (with a rise of requires a blower capable of driving 850 cubic feet of air per minute through the furnace casing. For cooling with an added refrigeration unit capable of freezing 3 tons of ice per 24 hours, the air flow past this refrigeration unit should be, according to conventional practice of providing 400 cubic feet per ton of ice-making capacity, about 1200 cubic feet per minute-an increase of about 50%.. If the original blower and motor (which are not large enough to provide this increase) are replaced by motor and blower of adequate size, problems still remain, for the increased air flow means increased air velocity. Increased air velocity raises the noise level above tolerable limits. And if this velocity is retained when the system is again employed for heating, condensation of water vapor in the flue gases will occur and corrosion will'result inthe furnace or in the flue. Hence the system, which has been revised to make'it suitable for both heating andcooling, turns out to be suitable for neither.

One approach to the foregoing problem is to provide the furnace with a by-pass to handle the additional air required in cooling and to provide a movable damper in this by-pass. At the same time the blower is equipped with a two-speed motor, one speed corresponding to the air volume required in heating, the other speed being greater to move the additional air required in cooling. When the furnace is to be used for heating alone, it is operated with the damper closing the by-pass, and at the first motor speed. Whena cooling coil is installed in series with the furnace and the system employed for cooling, the damper is moved to open the by-pass and the motor speed is increased to deliver the additional air required in cooling. The cross section of the bypass is such that there is the same air velocity past the furnace in cooling as in heating.

Our novel forced air furnace has a blower that will accommodate motors and impellers of various sizes. In our preferred structure, theseare easily changed, even after the furnace has been installed. Moreover, ournew furnace offers superior performance in a forced air heating system, permits higher air deliveries at optimum air velocities within tolerable noise levels, and without danger of moisture condensation and corrosion. Lastly, a forced air heating system in which it is included may be converted to a cooling system of various capacities with facility and withoutencountering any of the difiiculties that have been outlined above.

The forced air furnaceof our invention has a casing with front and back walls and two side walls. The furnace has a partition extending from side to side which divides its easing into two compartments. One compartment contains at least one radiator and preferably at least two hollow slab-like radiators disposed side by side and spaced from each other and from the side walls of the easing. Fuel is burn-ed in these radiators, which have high tending from front to rear of the casing. Preferably, the

axis is horizontal and parallel to the side walls. The

3 housing has inlet openings at front and rear adjacent the respective sides of the impeller. The impeller is driven by a motor which is disposed coaxially with it inside the casing. Conveniently, the motor is disposed within the impeller itself.

Preferably the radiator compartment is above the blower compartmenn'with the refrigerator (if one is employed) mounted above the radiator compartment. However, in some instances, the reverse situation prevails, with the blower at the top and the refrigerator at the bottom. Likewise, the blower, radiator, and cooling coil maybe disposed in that order side'by side at or about the same level, and the appended claims are to be construed to cover all such arrangements.

Forced air furnace design has proceeded for'many years on the assumption that a furnace is a furnace and a blower is a blower" and that the operation of one is independent of the other. We have discovered that this is not trueand that there can be'highly beneficial cooperation between furnace and blower if the two are properly shaped, proportioned and oriented. Thus we have discovered that resistance to the flow of air through a squirrel cage blower-furnace combination can be reduced substantially if the axis of rotation of the blower is oriented with long narrow air passages through the furnace.

In our furnace structure, the air currents generated by the blower are substantially parallel to the major surfaces, i.e. the sides, of the slab-like radiators. The air flow therefore tends to be smooth and non-turbulent, which is not the case when the axis of rotation of the impeller is transverse to the major radiator surfaces. The resulting reduction in turbulence means that higher air velocities may be attained without objectionable noise. In short, in the furnace of our invention higher air velocities and hence better thermal eiiiciencies may be obtained within tolerable noise limits.

The orientation of the fan housing and of the impeller in our furnace is different from that in most conventional forced air heating systems. In conventional furnaces, the axis of rotation of the impeller extends from side to side of the casing instead of from front to back. In such conventional furnaces, the entire fan is demountable and may be pulled out of the lower front of the casing. On the contrary, in the furnaces of the invention, the fan housing is permanently mounted in the casing and fan capacity may be altered by chan ing the impeller, one impeller being pulled out of the front of the casing, and replaced by another inserted from the front. If the motor is directly mounted on the impeller, which is preferable, the motor is changed at the same time.

In our presently preferred form of furnace, the rear of the fan housing is well inside the casing and spaced from its rear wall. There is also a space at the side of the fan housing within the blower compartment so that air may flow from the front of this compartment around the outside of the housing to the rear fan inlet. Access of air'to the fan is therefore easy, and the total resistance to air flow in the system is reduced.

When the furnace of our invention is employed as a heater, i.e. when fuel is being burned in the radiators, the

7 between a casing side wall and the radiator nearest that side wall, the internal partition being spaced from both "the side wall and the radiator to provide a by-pass. If a damper or plate is disposed in the by-pass, it may be opened to reduce resistance through the casing when 4 this is used merely as a conduit for air going to the refrigerator. When the raidators come into play to introduce heat to the air stream, the damper maybe moved to close the by-pass, thus forcing the air from the blower to flow at higher velocity as thin ribbons along the radiator surfaces, increasing heat recovery and thermal efficiency. If desired, the damper may be controlled automatically, for example, by a bimetallic element, so 7 quired for air conditioning is carried by the by-passes' and the velocity of air past the radiators remains substantially unchanged so that noise level remains low and condensation is prevented.

These and other aspects of our invention will be'understood thoroughly in the light of the following detailed description which is illustrated by the accompanying drawings in which:

'FIG. 1 is a front view, partly insection, of a preferred form of the furnace of our invention;

FIG. 2 is a sectional side view of the furnace of FIG. 1 taken along the line 2-2;

FIG. 3 is an enlarged view of a portion of FIG. 1 showing an automatic damper;

FIG. 4 is a fragmentary view showing a modification of the apparatus of Fl-G. l in which a permanently mounted plate or cap is employed to close the space between the side of the casing and the upwardly extending bafiie of FIG. 1; and

FIG. 5 is a front sectional view of the blower of FIG. 1.

The heater illustrated in the drawings has a casing 10 in the form of a box of rectangular plan having side walls 23, 14, front 15; and back wall 16. The particular casing is about twice as high as it ,is deep and about twice as deep as it is wide. It is separated into an upper (radiator) compartment 17 and a lower (blower) compartment 18 by a partition 19 that extends from side to side of the tors are spaced from each other by a narrow gap and from a the side walls of the casing by' wider gaps. The bottoms of the radiators are rounded to reduce resistance to air flow upwardly around and between them. Each radiator is provided with a burner 22 which discharges natural gas into the bottom of the radiator, where it burns in a rising current of air, the productsof combustion. being dis charged from the top of the casing to a flue 23. Internal partitions 24, 25 extend upwardly from front to back of the casing between the side walls of the casing and the radiators, being spaced from both to provide by-passes- In the apparatus of FIG. 1, the spaces betweenthe internal partitions and the side walls may be closed by dampers 26, 27 which are fastened to the partitions. One of these dampers is shown in greater detail in FIG. 3.

' It comprises a strip of bimetal which bends upwardly upon heating and moves out to the dotted position 26A. When the damper is cool," it lies substantially flat against the partition in position 26. Bimetal structures operate by reason of the fact that one of two adjacent metal strips has a coefficient of expansion that is greatly different from that of the other. This phenomenon is employed in a number of thermally-responsive devices and is used in the present case.

The lower compartment 18 of the casing may have a front opening 15A and contains a fan or blower 28. This blower is of the centrifugal squirrel cage type and has a housing 29 with an upwardly projecting discharge conduit 30 that flares outwardly and extends substantially from one side of the casing to the other at the partition which separates one compartment from the other. It will be noted that one side wall 30A of the discharge conduit is tilted inward from the vertical. This tends to produce a uniform distribution of the air flowing upwardaround and between the radiators and improves thermal efficiency. In other words, the shapes and orientation of blower and radiators cooperate to distribute the air properly at the heat transfer surfaces.

The fan housing has a rear. wall 31 which is spaced from the rear wall of the casing by a substantial distance and a front wall 32 which is spaced from the front wall of the casing by a greater distance. The front and rear walls of the fan housing contain air inlet members 33, 34 and between these air inlet members a squirrel cage impeller 35 is placed. This impeller rotates on a horizontal axis extending from front to back of the casing parallel to the side walls of casing and radiators and is directly connected to a motor 36 having a coaxial drive shaft 37. The motor is actually disposed within the squirrel cage impeller. The motor in turn is mounted on a bracket 38 disposed in the space in the lower compartment in front of the fan housing.

The fan housing is permanently fastened in the lower compartment, but the motor and the attached squirrel cage impeller are demountable and may easily be removed with or without the bracket, through the front of the lower compartment. An impeller of a different size can be accommodated by replacingv the annular air inlets 33, 34 with others having a different conduit length or a larger or smaller diameter. By way of example, the conduit portion (skirts) 33A, 34A or either of them may be made longer, while the impeller is made shorter, thus reducing fan capacity. Likewise, fan capacity may be reduced by employing an impeller of smaller diameter, changing the air inlets to match.

As shown in FIG. 1, there is a space 40 on the outside of the fan housing and within the lower compartment so that air entering the front of the lower compartment can move around the fan housing and enter it from the rear through the inlet 33, as well as from the front through the inlet 34.

As shown in FIG. 1, a conventional refrigerator unit 41 (containing a cooling coil) may be mounted above the heater in series with it so that air passing through the upper casing around the radiators enters the cooling unit and passes thence through a duct system 42. This carries the air (heated or cooled) to the rooms (not shown).

The furnace just described may be employed in several ways. When it is employed in a forced air system that lacks refrigeration means, maximum thermal efiiclency is assured by installing caps 43 (see FIG. 4) to close the by-passes between the internal partitions and the cas ng walls and force the air past the radiator at relatively high velocity to assure a temperature rise of 85 F. in the a1r.

We have already pointed out that the furnaces of our invention can be employed to solve the problem of proper air velocities for heating and for air conditioning.

Thus, tests conducted by the AGA verify that our furnaces are capable of delivering approximately 800 c.f.rn. (amount required for-2 tons of air conditioning) when by-passes are closed and approximately 1200 c.f.m.

(amount required for 3 tons of air conditioning) when by-passes are opened.

In accordance with the present invention, a furnace was tested in which j i (a) The by-pass was provided with a movable damper, the blower was equipped with a two speed motor, one speed corresponding to the air volume required in heating and the other speed being greater to move the additional air required in cooling; and

(b) An air conditioning unit was installed initially in series with the furnace and the blower.

When this installation was operated for heating the dampers in the by-passes were closed to prevent flow of air through the lay-passes. At the same time the motor was operated at its lower speed and provided sufiicient air for a 85 F. rise in temperature, this air amounting to 817 c.f.m.

When the system was operated on the cooling cycles the dampers were in an open position and the motor was switched to the second or higher speed. This provided the increase in air necessary for air conditioning, but as the additional air flowed through the bypasses the velocity of air flow over the heating element (radiator) was not increased.

We claim:

1. In a forced air heater, the combination which comprises a casing having a narrow front wall and a narrow back wall and two wide side walls, a partition disposed in the casing transverse to the back and side walls dividing the casing into a radiator compartment and a blower compartment, a plurality of hollow slab-like radiators disposed side-by-side in the radiator compartment and spaced from each other and from the side walls of the casing, the front and rear walls of the radiators being high and narrow and the side walls of the radiators being parallel to the casing wall and extending substantially from the front wall of the casing to the rear wall of the casing, an interior partition disposed in the radiator compartment between one side wall and the radiator nearest that side Wall and spaced from both that side wall and that radiator while extending substantially parallel to both, a damper disposed to close the space between the interior partition and the side wall of the casing, means for automatically moving the damper to close said space when the temperature in the vicinity of the damper increases and to open said space when the temperature in the vicinity of the damper decreases, a blower including a fan housing disposed in the blower compartment with its outlet conduit connected to and communicating with the radiator compartment through the partition, an impeller disposed in the housing and extending substantially from the front inlet tothe rear inlet and rotatable on an axis extending from the front of the casing to the rear of the casing, and a drive motor connected to the impeller.

2. In a forced air heater, the combination which comprises a casing having a narrow front wall and a narrow back wall and two wide side Walls, a partition disposed in the casing transverse to the back and side walls dividing the casing into a radiator compartment and a blower compartment, a plurality of hollow slab-like radiators disposed side-by-side in the radiator compartment and spaced from each other and from the side walls of the casing, the front and rear walls of the radiators being high and narrow and the side walls of the radiators being parallel to the casing wall and extending substantially fromthe front wall of the casing to the rear wall of the casing, an interior partition disposed in the radiator compartment between one side wall and the radiator nearest that side wall and spaced from both that side wall and that radiator while extending substantiallyparallel to both, a damper disposed in the space between the interior partition and the adjacent side wall of the casing,

References Cited in the file of this patent UNITED STATES PATENTS 1,991,449 Cornelius Feb. 19, 1935 2,001,531 Hall May 14, 1935 2,015,960 Norris Oct. 1, 1935 8 Kuenhold Aug. 17, 1937 Payne Mar. 31, 1938 Nelson Sept. 12,1939 Da nielson Aug. 5, 1941 Tuck -2 Aug. 4, 1942 Wessel Mar. 15, 1949 Druseikis Sept. 11, 1956 Costello et a1 July 23, 1957 Jaye et al. Oct. 1, 1957 Brugler Dec. 17, 1957

Claims (1)

1. IN A FORCED AIR HEATER, THE COMBINATION WHICH COMPRISES A CASING HAVING A NARROW FRONT WALL AND A NARROW BACK WALL AND TWO WIDE SIDE WALLS, A PARTITION DISPOSED IN THE CASING TRANSVERSE TO THE BACK AND SIDE WALLS DIVIDING THE CASING INTO A RADIATOR COMPARTMENT AND A BLOWER COMPARTMENT, A PLURALITY OF HOLLOW SLAB-LIKE RADIATORS DISPOSED SIDE-BY-SIDE IN THE RADIATOR COMPARTMENT AND SPACED FROM EACH OTHER AND FROM THE SIDE WALLS OF THE CASING, THE FRONT AND REAR WALLS OF THE RADIATORS BEING HIGH AND NARROW AND THE SIDE WALLS OF THE RADIATORS BEING PARALLEL TO THE CASING WALL AND EXTENDING SUBSTANTIALLY FROM THE FRONT WALL OF THE CASING TO THE REAR WALL OF THE CASING, AN INTERIOR PARTITION DISPOSED IN THE RADIATOR COMPARTMENT BETWEEN ONE SIDE WALL AND THE RADIATOR NEAREST THAT SIDE WALL AND SPACED FROM BOTH THAT SIDE WALL AND THAT RADIATOR WHILE EXTENDING SUBSTANTIALLY PARALLEL TO

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