US3415314A - Fan assisted heaters - Google Patents

Description

Dec. 10, 1968 H, JACKSON ET AL 3,415,314

FAN ASSISTED HEATERS Filed March 17, 1966 4 Sheets-Sheet 1 MMAW INVENTOR; H. E. JACKSON D. R. DEAN AJUELWMUAM Mm.

ATTOBN EYS.

Dec. 10, 1968 Filed March 17, 1966 H. E. JACKSON ET AL FAN ASSISTED HEATERS 4 Sheets-Sheet 2 FIG 2.

INVENTOES I H.E..TAC\(SON BY D. R. DEAN A0\C rvu.k0 -x 844L403 Dec. 10, 1968 H. E. JACKSON ET AL; 3,415,314

FAN ASSISTED HEATERS Filed March 17, 1966 4 Sheets-Sheet 5' N Q 9' h k ATTORNEYS De. l 0, 1 9 68 I H. E. JAcKsoN ETAL 3,

FAN ASSISTED HEATERS Filed March 17, 1966 4 Sheets-Sheet 4 INVENTOES H. E. Incusou D. R. DEAN M M Mm AT TOENEYS United States Patent 3,415,314 FAN ASSISTED HEATERS Harold Ernest Jackson, Plympton, Devon, and Douglas Raymond Dean, St. Budeaux, Plymouth, Devon, England, assignors to Petrol Injection Limited, Plympton, England, a British company Filed Mar. 17, 1966, Ser. No. 535,063 Claims priority, application Great Britain, Mar. 24, 1965, 12,461/65 4 Claims. (Cl. 165--122) ABSTRACT OF THE DISCLOSURE A transverse fio-w fan, air heater the housing of Which has a front face containing closely spaced air intake and outlet apertures, superposed to ensure adequate forwards directivity of the emergent heated air stream and separation of the emergent and intake air streams, shaped and positioned louvre strips spaced across its width and tilted to diverge from the inlet aperture in the direction of the emergent air stream to reduce turbulence. Trapeziurn (angle of tilt 9ll), aerofoil (46) and triangular (14l6) cross-section strips of plastics material and parallel-sided, round edged metal strips (4-6) are described.

This invention relates to fan assisted air heaters and particularly to such heaters having superposed inlet and outlet apertures in the same face of the heater housing.

In this type of heater, there can arise undesirable intermixing of the intake and emergent air streams, resulting in loss of efliciency of the heater. Whilst the problem is not serious in heaters having the inlet and outlet apertures spaced by a substantial distance, it can be acute in heaters of compact construction having a high thermal rating, and in which the air inlet and outlet apertures are closely separated.

According to the present invention, a fan assisted heater having superposed air inlet and outlet apertures in the same face of the heater housing has spaced louvres extending across the outlet aperture, the louvres being divergent at a small angle from the inlet aperture. In general, the angle of divergence of the outlet aperture louvres is so chosen that adequate separation of the emergent air stream from the intake air stream is obtained whilst maintaining good directivity of the emergent air stream forwards of the outlet aperture. The actual angle is to some extent dependent on the structure and material from which the louvres are made, ranging typically from about 416 for plastics materials, e.g. polypropylene or acrylonitrile butadiene and styrene (ABS), and from about 4-10 for metals, e.g., steel, and on the desirability of minimising turbulence in the emergent air stream. It has been found particularly suitable, both as regards efiiciency and costs, to use flat strips for the outlet aperture louvres, in the case of a plastics material the louvres having acutely angled trailing edges and in the case of steel louvres having rounded trailing and leading edges. However, louvres having aerofoil and triangular sections also have been used successfully.

The inlet aperture also can be louvred, the louvres being divergent from the outlet aperture to minimise air turbulence and to act as a barrier against entry of foreign bodies into the heater during operation thereof. A suitable range of inlet aperture angles of divergence is about 25 45 from the horizontal. The louvre shaping conveniently is the same as that adopted for the outlet aperture louvres but is not critical.

The invention is particularly suited to incorporation in a fan heater having superposed, elongated intake and out- 3,415,314 Patented Dec. 10, 1968 let compartments with which respective elongated air inlets and outlet apertures communicate. The intake compartment contains a transverse flow fan having a bladed cylinder, through which air from the air inlet aperture passes twice transversely of the cylinder axis before passing over an elongated heat exchanger arrangement in the outlet compartment and thence through the outlet aperture. Such a heater is capable of very compact construction with the fan rotor and heat exchanger occupying substantial proportions of the intake and outlet compartments and the thermal output of the heater can be made very high in relation to the overall size of the heater.

By way of example, an embodiment of the invention will be described in greater detail with reference to the accompanying drawings, in which:

FIG. 1 is a cross-section of a fan assisted heater,

FIG. 2 is a section on the line 11-11 of FIG. 1,

FIG. 3 is a frontal view of FIG. 1, and

FIG. 4 shows detail sections of suitable outlet louvre shapes.

The heater has an elongated housing 1 within which are defined intercommunicating superposed outlet and inlet compartments 2 and 3 respectively. The upper, outlet compartment 2 contains heat exchanger devices, shown as a liquid circulation heat exchanger in the form of a finned tube 4 and electric heating elements 5. The lower, intake compartment 3 contains a transverse flow fan 6 comprising a bladed rotor the blades 7 of which have outer edges 8 leading their inner edges 9 and presenting concave leading faces 10. The heat exchanger and fan occupy substantial proportions of the outlet and intake compartments in order to provide a compact assembly.

The front face 11 of the housing 1 defines an elongated outlet aperture 12 leading from the outlet compartment 2 and an elongated inlet aperture 13 leading to the intake compartment 3. In addition, a further inlet aperture 14, at the rear of the intake compartment, can communicate therewith under control of a pivoted flap 15 which can be moved between positions in which it closes the inlet aperture 13 (full line position FIG. 1) and in which it closes the inlet aperture 14 (broken line position FIG. 1). In intermediate positions of the flap 15, both inlet apertures 13 and 14 communicate with the intake compartment 3.

Movement of the flap 15 is ellected by an operating rod 16, a coil spring 17 (biasing the flap towards the position in which it closes the inlet aperture 14.

The fan 6 is driven by an electric motor 18 and when rotating, assuming that the flap 15 closes the inlet 'aperture 14, draws in air through the inlet aperture 13 into the intake compartment 3, the air passing twice through the rotor blades 7, at all times-transversely of the rotor axis, into the upper compartment 2, over the heat exchanger elements 4, 5 and thence through the outlet aperture 12.

It will be noted that the inlet and outlet apertures 12, 13 are separated by but a short portion, typically about one inch, of the front face 11 and this small separation can lead to undesirable intermixing of the incoming and emergent air streams resulting in inetficient operation of the heater.

To overcome this problem, louvres 19 are incorporated in the outlet aperture 12, extending along the length of the aperture and being slightly tilted from the horizontal so that they are divergent from the inlet aperture 13 by a small amount. The precise angle of divergence is dependent partly on the shape of the lou vres 19 and the material 'from which they are made, the optimum angle being readily determined by experiment. This arrangement permits a compact heater construction to be adopted whilst avoiding undesirable intermixing of the incoming and emergent air streams. In general, a range of angles extending from about 4l6 to the horizontal has been found suitable, the actual range depending both on the material from which the louvres are made as well as on the cross-sectional shape of the louvres, as will be explained with reference to FIG. 4.

Using a plastics material, e.g. Polypropylene or Acrylonitrile Butadiene and Styrene (ABS), a range of angles between 4 and 16 has been found useful using crosssectional shapes as shown in FIGS. 4a, 4b and 4c. The aerofoil section shown in FIG. 4a has been found to give rise to minimum turbulence using a preferred angle of inclination of 5 to the horizontal, and extending a degree or so either side, but the section is relatively difficult to manufacture. The trapezium shape shown in FIG. 4b has been found most effective using a preferred angle of inclination of to the horizontal. The shape is easier to manufacture than that shown in FIG. 4a but introduces rather more turbulence, necessitating the increased angle of inclination. The triangular section shown in FIG. 40 has been found to work using a preferred angle of inclination of the upper surface of but introduces more turbulence than either of the sections shown in FIGS. 4a and 4b and is also more difficult to manufacture than that shown in FIG. 412.

Using metal, e.g. steel, louvres, a parallel sided strip section with curved ends, as shown in FIG. 4d, has been found very suitable using angles in the range 4-10, and with a preferred range centered on 5 and extending a degree or so either side. Little turbulence is introduced and the section is easy to manufacture.

In addition, the inlet aperture 13 incorporates louvres 20, extending along the aperture, and tilted downwards so that they are divergent from the outlet aperture 12.

The tilt angle is relatively large, suitable in the range -45 to the horizontal, and the effect is to decrease air turbulence at the front face 11 of the housing 1 and also to provide a barrier against entry of foreign bodies through the inlet aperture 13.

The inlet 14 can be connected to a suitable fresh air source to permit circulation of fresh air, with or without operation of the heat exchanger elements 4, 5.

In a particular construction, the inlet and outlet apertures are 14 /2 inches long and 3 /2 inches broad and are separated by a distance of 1 inch along the front face of the heater. Each aperture has six plastic louvres of cross-sectional shape as shown in FIG. 412 having crosssectional dimensions:

d= /z inch e being dependent on the angle of tilt used but typically inch.

The louvres in the outlet aperture diverge from the inlet aperture at an angle of 10 to the horizontal and the inlet aperture louvres diverge from the outlet aperture at an angle of to the horizontal. The overall dimensions of this heater are about 24" x 9" x 5". The heat output, using a water circulation rate through the heat exchanger 4 (the heater elements 5 being omitted) of 1.5 gallons per minute and water temperature 100 F. above the required space ambient temperature, is at least 9,000 B.t.u. per hour at a fan speed of 2,100 rpm. The construction and disposition of the outlet aperture louvres has been found most effective in making adequate separation between the intake and emergent air streams, whilst retaining good forwards directivity of the emergent air stream in this compactly constructed, high thermal output heater, despite the small separation of the inlet and outlet apertures.

Instead of using louvres having the cross-sectional shape shown in FIG. 4b, any of the shapes shown in FIGS. 4a, 0 or d could be used instead, typical 'values for the dimensions indicated in FIG. 4 being:

FIG. 4a a /z inch, b: inch, 0: 9 inch.

FIG. 40 g= /z inch, i= inch, h being dependent on the angle of inclination used and typically inch.

FIG. 4d j: /2 inch, k:%; inch or nearest sheet metal gauge.

The heater preferably incorporates a thermostatic switching device for controlling operation of the fan, the switching device having a temperature responsive element located adjacent the air inlet aperture. The temperature responsive element has an associated auxiliary heating device and the switching device is operable to energise that heating device only when energising the fan motor. With this arrangement, the effects of local heating of the temperature sensitive element by the heat exchanger elements of the heater are compensated by the auxiliary heater providing an equivalent heat input to the element when the fan is operating.

This arrangement is not shown herein but is more fully described in our co-pending application No. 12,935/64.

We claim:

1. In a fan assisted heater having a housing including a front face and defining elongated superposed, intercommunicating air intake and outlet compartments divided by partition means, said front face having elongated superposed air inlet and outlet apertures extending lengthwise of and communicating with said intake and outlet compartments respectively, said inlet and outlet apertures being closely spaced apart along their respective lengths, louvers extending horizontally across said inlet aperture and set at a downward angle of about 25 45 from the horizontal, heat exchanger means disposed coextensively with said outlet compartment and transverse flow air intake fan means comprising a cylindrical bladed rotor disposed in said intake compartment for drawing air via said inlet aperture into said intake compartment and passing such air into heat exchange relation with said heat exchanger means thence to emerge from the said air outlet, and spaced louvre strips extending lengthwise across and fixedly secured in said outlet aperture, the improvement according to which said outlet louvre strips are strips of plastic material having a trapezoidal cross-section and inclined at an angle of approximately 9l1 to an imaginary horizontal plane, and the rearward edge of each trapezoidal strip is inclined to said imaginary horizontal plane in a direction opposite the direction of inclination of that strip to minimize the turbulence of the heated air leaving the heater and thereby separate the air intake stream to the inlet aperture from the air stream emergent from the outlet aperture while maintaining forward directivity of said emergent air stream from said front face of the housing.

2. In a fan assisted heater having a housing including a front face and defining elongated superposed, intercommunicating air intake and outlet compartments divided by partition means, said front face having elongated superposed air inlet and outlet apertures extending lengthwise of and communicating with said intake and outlet compartments respectively, said inlet and outlet apertures being closely spaced apart along their respective lengths, louvres extending horizontally across said inlet aperture and set at a downward angle of about 25 -45 from the horizontal, heat exchanger means disposed coextensively with said outlet compartment and transverse flow air intake fan means comprising a cylindrical bladed rotor disposed in said intake compartment for drawing air via said inlet aperture into said intake compartment and passing such air into heat exchange relation with said heat exchanger means thence to emerge from the said air outlet, and spaced louvre strips extending lengthwise across and fixedly secured in said outlet aperture, the improvement according to which said outlet louvre strips are strips of plastic material having an aerofoil cross-section, said strips of plastic material inclined at an angle of approximately 46 to an imaginary horizontal plane and the nose of each areofoil strip faces outwardly from the outlet aperture to minimize the turbulence of the heated air leaving the heater and thereby separate the air intake stream to the inlet aperture from the air stream emergent from the outlet aperture while maintaining forward directivity of said emergent air stream from said front face of the housing.

3. In a fan assisted heater having a housing including a front face and defining elongated superposed, intercommunicating air intake and outlet compartments divided by partition means, said front face having elongated superposed air inlet and outlet apertures extending lengthwise of and communicating with said intake and outlet compartment respectively, said inlet and outlet apertures being closely spaced apart along their respective lengths, louvres extending horizontally across said inlet aperture and set at a downward angle of about -45 from the horizontal, heat exchanger means disposed coextensively with said outlet compartment and transverse flow air intake fan means comprising a cy1in drical bladed rotor disposed in said intake compartment for drawing air via said inlet aperture into said intake compartment and passing such air into heat exchange relation with said heat exchanger means thence to emerge from the said air outlet, and spaced louvre strips extend ing lengthwise across and fixedly secured in said outlet aperture, the improvement according to which said outlet louvre strips are strips of plastic material having an acute-angled triangular cross-section and inclined at an angle of approximately l416 to an imaginary horizontal plane with the short base of each strip facing outward from the outlet aperture and the long base facing upward to minimize the turbulence of the heated air leaving the heater and thereby separate the air intake stream to the inlet aperture from the air stream emergent from the outlet aperture while maintaining forward directivity of said emergent air stream from said front face of the housing.

4. In a fan assisted heater having a housing including a front face and defining elongated superposed, intercommunicating air intake and outlet compartments divided by partition means, said front face having elongated superposed air inlet and outlet apertures extending lengthwise of and communicating with said intake and outlet compartments respectively, said inlet and outlet apertures being closely spaced apart along their respective lengths, louvres extending horizontally across said inlet aperture and set at a downward angle of about 25 45 from the horizontal, heat exchanger means disposed coextensively with said outlet compartment and transverse flow air intake fan means comprising a cylindrical bladed rotor disposed in said intake compartment for drawing air via said inlet aperture into said intake compartment and passing such air into heat exchange relation with said heat exchanger means thence to emerge from the said air outlet, and Spaced louvre strips extending lengthwise across and fixedly secured in said outlet aperture, the improvement according to which said outlet louvre strips are strips of metal having a cross-section consisting of parallel flat upper and lower surfaces and curved side edges and inclined at an angle of approximately 46 to an imaginary horizontal plane to minimize the turbulence of the heated air leaving the heater and thereby separate the air intake stream to the inlet aperture from the air stream emergent from the outlet aperture while maintaining forward directivity of said emergent air stream from said front face of the housing.

References Cited UNITED STATES PATENTS 2,985,089 5/1961 Gilmore 98-40 3,045,578 7/1962 McGrath 98-40 3,147,368 9/1964 Walker -122 X 3,182,579 5/1965 Wiseman 98-40 3,280,901 10/1966 Laing 165-122 ROBERT A. OLEARY, Primary Examiner.

T. W. STREULE, Assistant Examiner.

US. Cl. X.R. 98-40; 165-54

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