US 3481322 A
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1969 c. c; HOKANSON. SR E L HEATING APPARATUS INCLUDING A HEAT EXCHANGE AND TURBULENCE CREATING IMPELLER Filed Nov. 2, 1967 United States Patent 3,481,322 HEATING APPARATUS INCLUDING A HEAT EXCHANGER AND TURBULENCE CREAT- ING IMPELLER Carl G. Hokanson, Sr., Los Angeles, and Richard A. Evans, Irvine, Calif., assignors to Lear Siegler, Inc., Santa Monica, Calif., a corporation of Delaware Filed Nov. 2, 1967, Ser. No. 680,207 Int. Cl. F24c 9/00; B60h 1/02; F22b 3/ 06 US. Cl. 126-247 6 Claims ABSTRACT OF THE DISCLOSURE A heating unit is disclosed which delivers heated air free of any contaminants. A driving unit is coupled to an impeller located within a closed container having an inlet and an outlet port and a main portion which is substantially larger than the dimensions of the impeller. The energy of the driving unit is converted into heat in a substantial quantity of air which is trapped within the main portion and is turbulently mixed by the impeller. A small percentage of air relative to the total volume of the container is continually introduced into the large container and a similar small percentage is contin-ually exited at a desired static pressure provided by oifsetting the impeller close to a side wall of the container. The remaining volume of air is subjected to innumerable mixings and, thus, is heated by the impeller during the time it is trapped in the container. The prime mover for the impeller may be a liquid-cooled engine equipped with valves to selectively supply the heated liquid of the engine to a heat exchanger located in the input stream of air prior to the inlet port of the container. A sound baffie and acoustic and insulating material enhance heating and also sound diminution.
BACKGROUND OF THE INVENTION Field of the invention This invention relates, in general, to air heating apparatus and, more particularly, relates to a simple substantially instantaneous heater which converts horsepower directly into heat in a trapped quantity of air thereby providing heated air which is free of any odors or contamination. The fields in which the present invention is applicable include aircraft, mobile trucks, trailers and other vehicles, as well as heating plants for homes, factories and similar establishments.
Description of the prior art It has been commonplace for many years to employ combustion heating Where air is heated in a chamber which includes a heater element, such as a flame or an electric coil. Normally associated with the heater element is a blower is driven by an electric motor and is positioned to move the heated inlet air through an outlet port. In such units, the blower rotor is designed to fit snugly in a volute housing which is increasingly spaced away from the blower rotor at the outlet port as compared to the spacing between the blower rotor and the housing at the inlet port. Generally speaking, the rotor and its housing are designed to produce a minimum amount of turbulence while at the same time delivering a substantial quantity of heated air to the outlet port. Great care has been taken in the past to control manufacturing tolerances in such a manner that the blower eificiency is improved by directly minimizing any undesired turbulence in the air passing from the inlet to the outlet port.
A somewhat related technique, particularly in those instances wherein the heater must be mobile, has been to 3,481,322 Patented Dec. 2, 1969 ice employ an engine, which is liquid-cooled, as the heating element. The liquid used for cooling the engine as well as the heat from the exhaust system of the engine, is then indirectly employed to heat a stream of air moved by the blower. This technique requires a long warm-up time in order that the liquid coolant reach a high enough temperature to heat great quantities of air. This long warm-up time is particularly objectionable at low ambient temperatures when a mobile heater is coupled to the duct system of a commercial airplane during instances when the aircrafts engines are off and the aircraft is docked for loading and discharging passengers. In such instances, it is almost mandatory that the heater be substantially instantaneous in order to avoid wasting fuel for the engine during long warm-ups and, furthermore, be readily available whenever discrepancies appear in the aircraft schedules. Furthermore, in this prior art approach the exhaust system of an engine often tends to introduce odors in the air being heated in a manner somewhat similar to the odors produced from open flame burners and such odors are particularly objectionable in the ducting of aircraft. Finally, at low ambient temperatures the engine often fails to warm up to a high enough temperature that large volumes of air may be suitably heated.
The foregoing and other objectional features and problems of the prior art are avoided in our invention.
SUMMARY OF THE INVENTION This invention provides a simple substantially instantaneous heating system which heats ordor-free quantities of air that may be controllably supplied in desired amounts and temperatures at :a selected static pressure.
The operational principles upon which this invention is based represent a radical departure from the prior art in that the invention has employed a characteristic, which has heretofore been regarded as objectionable, to a new and unique advantage. Thus, applicants have departed from normally recognized standards for the design of blowers by developing a housing chamber which is considerably larger, in all dimensions, i.e., width, height and depth, than the dimensions of the rotatable impeller housed in the chamber. The impeller, or blower rotor, is located in an end wall of the housing at a position which is oifset from the end falls center toward one side wall so as to develop a desired amount of static pressure for air within the container.
The volume of air contained in the housing chamber of this invention is substantially greater than the volume of air in prior art blower chambers and, this again, represents a departure from conventional blower designs in that normal blowers are :aranged to receive a fixed quantity of air at an inlet port and pass that fixed quantity of air out the outlet port without creating turbulence and without trapping any substantial amount of air.
In applicants heating apparatus, a hollow container or chamber substantially larger than the impeller is provided for receiving a given volume of air. A predetermined percentage of this volume of air, after heating, is passed from the container via an outlet port. A remaining, and substantially larger percentage of this volume of air, is trapped within the container wherein it is directly subjected to heating through work performed on it by a violently turbulent action induced therein by the impeller. A centrifugal-type impeller of a given width and diameter, both of which are less than the inner dimensions of the container is mounted in one wall. A prime mover is provided for rotating the impeller about a spin axis at a location in the end wall which is offset from the end walls center toward one side wall. This location allows the air delivered by the impeller to be squeezed impellers location or the location of the outlet port may be adjusted as a means of varying the outlet pressure andthe amount of heating as Well.
A cylindrical air inlet port is located at an opening in the front Wall which is coaxial with the spin axis of the impeller. This inlet port is flush with the interior surface and extends away from the front wall in a manner which blocks the recirculated air from exiting out the inlet port. This inlet port, in one embodiment, is longitudinally adjustable into the housing as a means of chang ing the efi'iciency and thereby controlling the amount of heating.
In one preferred embodiment, the prime mover for rotating the impeller is a high horsepower engine having a liquid cooling system. A heat exchanger comprising a plurality of conduits, each provided with numerous heat conducting radiation fins, is located adjacent the cylindrical inlet port. These conduits may selectively receive an adjustable amount the heated liquid from the prime mover so as to controllably add heat by convection and radiation to the air passing through the heat exchanger prior to its entrance into the inlet port. The speed of the prime mover is adjustable to controllably vary the energy supplied to the impeller and thereby control the amount of heat supplied by the unit.
The continuous and turbulent recirculation of a large volume of air for heating the air, in accordance with this invention, introduces, in addition to heat, a high noise level. The container is surrounded by a dense blanket of acoustic and temperature insulating material which aids in damping out this noise level and preserving the temperature increase in the heated air. In one further preferred embodiment, the heat exchanger is cylindrical in form with a diameter substantially larger than that of the inlet port and having an axial length which is also longer than the length of the cylindrical inlet port. The cylindrical heat exchanger surrounds the inlet port. An impervious sound baflie which is also of acoustic and temperature insulating material is mounted at the end of the heat exchanger coil which is remote from the housing chamber. This sound baflie absorbs noise which otherwise may tend to be emanated out the inlet port.
BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a top view of the heater of this invention, partially broken away and showing in schematic form a prime mover;
FIGURE 2 is a side elevation of a major portion of the impeller and its housing in accordance with this invention; and
FIGURE 3 is an end view showing one form of the heat exchanger of FIGURE 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to FIGURE 1, the heating apparatus in accordance with this invention is shown including two main portions, namely, a prime mover portion and an air heating and static pressure creating unit 75. The engine 25 and the heater 75, it should be understood, may be mounted on any suitable frame (not shown in FIGURE 1) such as a trailer unit or a self-mobile heating truck. Any particular prime mover 25 may be utilized, for example, a gasoline, diesel or electric engine would sufiice provided that the engine develops considerably more horsepower than that which would normally be rated for the impeller 65 when enclosed within a standard voluted container.
Selecting the prime mover 25 as a liquid-cooled engine provides additional heating ability in that the liquid that cools the engine 25 absorbs heat and may be controllably circulated through a heat exchanger unit 60 of heating apparatus 75.
A liquid coolant such as water is piped through the main body of the engine block 20 in a standard fashion whereafter it is normally supplied through a radiator 15 equipped with fan 16 which serves to remove the heat conducted into the liquid during its circulation through block 20. A pair of control valves 17 and 18 which are respectively located in the inlet and outlet lines 13 and 14 connecting the radiator 15 to block 20. These valves 17 and 18 may be any well-known valve which is automatically or manually controllable in such a manner that all, or a portion of, the liquid passing through the block 20 may be diverted from radiator 15 and supplied instead to the heat exchanger 60 via conduits such as pipe or rubber hoses 10 and 12. The engine 25 is further provided with any suitable power drive unit 21, such as a gear box, which is mechanically coupled to an impeller shaft 74 of the impeller 65. This mechanical coupling may be through belts or any other suitable drive linkage as is well known in the art.
The impeller shaft 74 is suitably mounted for rotation in a bearing 73 which is located adjacent an opening 72 in the end wall 59 of the impeller housing chamber 70. The housing chamber 70 is substantially larger than the impeller 65 and confines a substantially large volume of air. Opening 72 which receives the impeller shaft 74 is offset toward one side wall of the chamber 70. As engine 25 drives the impeller 65 for high speed rotational movement on shaft 74, this ofiset location for impeller 65 tends to squeeze the air centrifugally thrown out the impeller blades 65A against the closely positioned side wall of housing chamber 70. This offset location converts the velocity pressure of air expelled from the tips of the blades 65A against the side wall of housing chamber 70 into a predetermined amount of static pressure.
As is well known, static pressure is the amount of pressure necessary to overcome the resistance of ducts, nozzles, etc. to which the outlet duct 78 may be connected. This static pressure is variable depending upon the rotational speed of the impeller 65 and the flow rate of air through the housing chamber 70. The static pressure, if desirable, may also be changed by utilizing an elongated opening 72 which would allow the spacing between the outermost tips of the blades 65A of impeller 65 and the closest side wall of housing chamber 70 to be varied. Additionally this same result may be achieved by varying the location of outlet port 76 to a lower pressure location in chamber 70. Although not depicted in the drawing, for simplicity purposes it should be' understood that selected locations may receive outlet port 76, or it may be flanged and slidably moved in runways provided in the end wall. Such flanges and runways are known to the sheet metal art and thus need not be described herein in further detail. The location depicted for outlet port 76 provided maximum pressure and outlet volume in one preferred embodiment.
In one particularly advantageous system, which is not to be taken as limiting, the spacing between the tips of the blades 65A of impeller 65 and the closely adjacent side wall of chamber 70, is in the order of one-half to one inch. In this reference unit, an eight-bladed centrifugaltype impeller, rotating at a speed of approximately 5,000 revolutions per minute, created a static pressure of approximately twenty inches. In this same unit a flow rate of 4,000 cubic feet of air per minute was established with a temperature gradient increase from turbulence alone of approximately 100 F.
Air to be heated enters unit 75 through an inlet opening 30 fitted with a suitable viscous coated air filter 31 and into the portion of the heating unit occupied by heat exchanger 60. From the heat exchanger chamber air passes through air inlet duct 71 t0 impeller chamber 70. Prior to entering the inlet duct 71, the filtered air may, if desired, be preheated by passing it through the heat exchange unit 60 in a manner more fully described hereinafter.
Reference to FIGURE 2 depicts a side elevation partially cut away and including arrows 80 representative of the substantially laminar air flow input through ducts 71 and 7-8 and wavy arrows 81 which are representative of the turbulent recirculation which the volume of air within the housing chamber 70 experiences. Thus, a large percentage of the overall volume of air contained within the housing chamber 70 is trapped between the front wall 58 and the end wall 59. The centrifugal force of the rotating impeller 65 forces this trapped volume of air against the front, end and side walls of chamber 70.
This large volume of trapped air represents a considerable workload for the impeller '65. Motors for driving impellers such as impeller 65 normally require (in a standard voluted housing) a horsepower rating of thirty or forty horsepower depending upon such variables as housing design, static pressure and flow rate. In accordance with the principles of this invention that rated horsepower is substantially exceeded to such extent, for example, that the horsepower available at the shaft 74 of impeller 65 may be in the order of 150 to 200 horsepower. This substantial amount of horsepower energy required to rotate the impeller 65 is converted directly into heat in the volume of trapped air through pressure and viscous friction since the impeller 65 is substantially the only load for engine 25. The horsepower energy is thus readily absorbed by the turbulence of the trapped air and is represented therein as a temperature increase gradient which for the exemplified heater mentioned hereinbefore is approximately 100 F. This temperature gradient at the illustrative flow rate of 4,000 cubic feet per minute represents approximately 400,000 B.t.u.s per hour at a fuel consumption rate for engine 25 of approximately one-half pound per hour per horsepower and thus is far more eflicient and economical than other comparable prior art units. In addition, it should be understood that this temperature gradient is independent of the temperature of air supplied to the inlet and thus does not drop olf rapidly in efiiciency at lower operational temperatures as experienced by most prior art apparatus.
Even in extreme cold the temperature gradient provided by the turbulence impeller of this invention is substantially instantantous in that only three or four minutes warm-up time is required. This limited warm-up time provides an initial amount of heated air suitable for rapidly heating commercial aircraft as one typical use. In employing the heating apparatus of this invention for heating commercial aircraft, the outlet duct 78 may be connected through any suitable flexible duct terminating in a coupling adaptable to join with the internal duct work of an aircraft. Outlet duct 78 further includes a damper 77 which may be either manually or automatically adjusted to control the volume of air flow out of the heater unit 75. Of course, the duct work at outlet port 76 may be connected to any other apparatus to be heated in a quick and economical manner by this invention.
In some extreme instances, the 100 F. temperature increase gradient of the turbulence impeller may not suffice. In such an event, the heating apparatus of this invention has the additional advantage of readily supplying approximately 50 to 75 F. additional temperature rise through the combination of the turbulence impeller heater unit 75 and the heat exchanger 60. Thus, as mentioned earlier, the engine 25 is loaded down by the work required to drive the impeller 65 and rapidly reaches its upper temperature operating level which may be controlled by a thermostat to approximately 180 F.
In order to supplement the turbulence-impeller heater by employment of heat exchanger 60, valves 17 and 18 may be variably controlled to divert any desired amount of hot liquid away from radiator 15. The diverted hot liquid is passed by pipes 10 and 12 through a plurality of heat exchanger coils 62.
Reference to FIGURES 2 and 3 depicts views showing the inlet and outlet pipes 10 and 12 connected to four circular heat exchanger coils '62. Thus, the hot liquid is fed through the lower inlet pipe 10 (FIGURE 3) through the T couplings around the circular heat exchanger pipe 62 to the uppermost T coupling at the upper outlet pipe 12. Any suitable heat exchanger configuration, of course, may be employed other than the circular heat exchanger 60 provided that it is located at a position wherein the air must pass through the radiating fins 61 which surround each one of the heat exchanger conduits 62 prior to the entrance of the air into the cylindrical inlet duct 71 and inlet port 79.
Inlet duct 71 is adjustable inwardly toward impeller 65 as by sliding, turning or otherwise. We have discovered that the position of inlet duct 71 is a simple means for controlling the efliciency and heating amount for our unit. In one embodiment maximum volume and heat was obtained by adjusting inlet duct 71 so that it was substantially flush with the interior of the front wall 58. Thus, the elongated cylindrical inlet duct 71 serves as a trap which admits the air and at the same time blocks the passage of air out the inlet port. The adjustability of the inlet port further serves to controllably restrict the turbulence effects within chamber housing 70.
A good deal of noise is created by the turbulence, which noise would emanate out port 79 and duct 71. The 'bafiile plate 55 is located directly in front of the outer point of duct 71 and is spaced from it enough to allow air to enter the duct 71. Bafile plate 55, as well as all portions of the chamber housing 70 (except for filter inlets not shown), is covered with a thick layer of densely celled acoustic and insulating material 56 of any well-known type. Such insulating material 56 serves to confine both heat and noise within the unit to levels suitable for a great number of commercial and industrial uses.
It is to be understood that the foregoing features and principles of this invention are merely descriptive, and that many departures and variations thereof are possible by those skilled in the art, without departing from the spirit and scope of this invention.
1. Apparatus for mechanically heating air and the like comprising:
an elongate housing having opposite end walls spaced along a housing centerline axis,
a rotatable radially bladed impeller disposed in the housing substantially closer to one end wall than to the other end wall and eccentrically of the housing axis for rotation in a plane normal to the housing axis, the impeller being provided independently of and in the absence of a stationary shroud or volute circumferentially thereof,
an inlet to the housing through the other end wall coaxially of the impeller,
an outlet from the housing through the one end wall I substantially parallel to the housing axis eccentrically of said axis and radially outwardly of the impeller,
the inlet and the outlet being of substantially equal area, and
means coupled to the impeller for rotating the impeller at a high rate.
2. Apparatus according to claim 1 including an inlet duct cooperating with the inlet and extending from said other end wall substantially parallel to the housing centerline axis.
3. Apparatus according to claim 2 wherein the inlet duct extends away from the impeller relative to the other end wall of the housing.
4. Apparatus according to claim 2 wherein the inlet duct is mounted for movement relative to the housing other end wall toward and away from the impeller.
5. Apparatus according to claim 1 including sound bafiling means operatively associated with the inlet housing for suppressing noise generated within the housing during operation of the apparatus.
7 s 1 6. Apparatus according to claim 1 including acoustic 3,221,415 12/1965 Murray 126-110 X and thermal insulating means covering the housing. 3,245,399 4/1966 Lawson 126-247 3,385,287 5/1968 Lawson et a1 126-247 References Cited UN STATES PATENTS 5 ROBERT A. OLEARY, Primary Examiner 1,750,681 3/1930 Morse 230-133 X A. W. DAVIS, Assistant Examiner 1,862,289 6/1932 Anderson 230-114 2,562,405 7/1951 Altman 126-247 X US. Cl. X.R.
2,951,630 9/1960 Murphy 230-133 X 122-26; 237-123