Abstract:
A radiator operable with a flow of air for cooling a quantity of water and formed as zig-zag walls, each of which comprises air ducts of predetermined ratio of flow length to hydraulic diameter.

Description:
This is a continuation of Ser. No. 379,708, filed July 16, 1973, which was a continuation of Ser. No. 203,609, filed Dec. 1, 1971, both now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a motor-car radiator which is particularly suitable for use in the cooling system of an external combustion engine, said radiator having a number of parallel cooling water pipes which communicate at one end with an inlet and at the other end with an outlet for cooling water. The pipes are connected by a number of metal components, for example strips or gauze, extending at right angles to said pipes and being in a head conducting contact therewith. 
     In combustion engines, only a part of the evolved thermal energy is converted into mechanical energy, while the other part has to be dissipated as heat due to energy losses. A part of said heat due to energy losses is dissipated together with the hot exhaust gases, while another considerable part is given off to the ambient air via the cooling system and the radiator present therein. This radiator usually is situated in the front of the car in which the engine is present as a traction means. 
     When, as has been usual up till now, an internal combustion engine is used as a traction means, the space in the front of the motor-car usually is sufficient cooling capacity without too may difficulties. If, however, an external combustion engine, for example the Stirling engine or the steam engine, is used as a source of propulsion, difficulties occur immediately in connection with the radiator. As a matter of fact, the amount of thermal energy in this type of engines which has to be dissipated to the atmosphere via the radiator is much larger than in internal combustion engines. This means that the cooling capacity of the radiator has to be increased. 
     A first possibility of achieving this is to use a conventional radiator having a larger front face area. However, it will soon become apparent in this case that the dimensions of the radiator become too large for the front of the motor-car. A second possibility could be an increase of the cooling capacity per surface unit by refining the construction of the radiator, so by using narrower flow ducts for the air, or by increasing the length of the ducts by using a thicker radiator. This meets with two objections. First of all, with an acceptable front face area, these measures result in a radiator having such a large resistance to flow that the fan which is then necessary requires an unacceptably large power to draw in the required amount of air. Secondly, the fine flow ducts for the air will soon give rise to pollution of the radiator by insects and so on. 
     A third possibility which has been considered in carrying the invention into effect is the arrangement in V-shape of a number of conventional radiator units. Such a shape of radiator is known from United Kingdom Pat. No. 506,146 for incorporation in the wing of an airplane. Since the thickness of the conventional radiators is from 5 to 10 cm it will be obvious that, in order to obtain herewith an increase of the radiator surface area without increasing the overall transverse dimension, a radiator will be obtained having very a large dimension in the longitudinal direction which is unacceptable in motor-cars and is furthermore unattractive because the occurring flow losses in the deep V-shape reduce the effect of the increase in surface area. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to provide, on the basis of the above considerations, a radiator which has a large cooling capacity, a low weight and occupies little space. The radiator according to the invention is characterized in that the cooling water pipes are arranged in a number of flat elements, the upper and lower sides of which are each located in a common plane and the two other sides are located in the front and rear plane, respectively, of the radiator. The elements enclose an angle of more than 45° with the front and rear plane of the radiator, the elements being connected together alternately on their front and rear sides in an air-tight manner so that a pleated front and rear side, respectively, is obtained. The dimension of the thickness of each of the elements is at most 25 mm, the quotient L/d h  being smaller 15, L being the length and d h  the hydraulic diameter of the air ducts in each of the element. 
     In this manner a radiator is obtained in which a very large cooling capacity is associated with acceptable width and thickness dimensions so that incorporation in motor-cars is possible without great problems. As a result of the fine subdivision, a large cooling capacity per unit of front face area is obtained in which nevertheless the resistance to flow is low, while, as a result of the inclined position of the radiator element relative to the flow direction of the air, surprisingly substantially no pollution occurs. Insects and other dirt gather neatly at the areas where the rear sides of the elements are connected together. 
     In order to ensure that contaminations are readily caught and the radiator can easily be cleaned, a further favourable embodiment is characterized in that each of the connections on the rear side of the elements is constructed as a channel-shaped connection member for receiving contaminations. 
     In a preferred embodiment according to the invention, the channel-shaped connection members communicate on their lower side with an exhaust channel which extends below the radiator and whose aperture faces the front side of the radiator. In this manner, contaminations gathered in the channels with fall down and be removed via the exhaust channel when the vehicle is stationary. In order to ensure a good guide of the air entering the radiator, each of the connections on the front side of the elements have a good aerodynamic shape so that the air readily flows into the radiator. 
     In a further favorable embodiment, each of the elements comprises on its outer circumference a layer of fine gauze having a mesh-width smaller than 1.5 mm. This prevents pollution of the radiator in a very effective manner while in addition said gauze is effectively involved in the heat exchange. 
     In order that the invention may be readily carried into effect, it will now be described in greater detail, by way of example, with reference to the accompanying drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 and 2 are two mutually perpendicular sectional views of a radiator consisting of a number of elements arranged in V-shape, 
     FIG. 3 is a sectional view of another embodiment of a radiator, 
     FIG. 4 shows a parallel arrangement of the elements. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 and 2 show two mutually perpendicular sectional views, which are diagrammatic and not drawn to scale, of a part of a radiator which is constructed from a number of elements 1 which enclose an angle α with the front and rear faces 2 and 3, respectively, of the radiator. 
     Each of the elements 1 comprises a number of cooling water pipes 4 which communicate at one end with a common inlet duct 5 and on the other end with a common outlet duct 6. The pipes 4 are connected together by a large number of flat metal strips 7 which are connected in a heat conducting relationship with the pipes, for example, by soldering. 
     The elements 1 are connected together by a channel-like part 9 on their rear side and at the area 8 and on their front side. When the radiator is accommodated in a motor-car, the air entering the radiator will flow through the radiator in the direction of the arrows. The connections at the area 8 have a good aerodynamic shape, so that the air entering the radiator can easily be guided to the radiator surfaces. 
     As a result of the arrangement in V-shape of the elements 1, the radiator surface area has been increased considerably, namely by a factor (1/cos.α ). Of course the thickness of the elements should be subtracted therefrom, because at the areas 8 and 9 this provides a section through which no air can pass. In known radiators having a thickness from 5 to 10 cm, a large part of the effect of the V-shape is thus lost. In the radiator according to the invention the thickness d of each of the elements is at most 25 mm. This means that the connections 8, 9 require only little space. In order to enable this small thickness of the elements, while maintaining a sufficient cooling capacity per surface unit, it furthermore holds for the ducts 10 through which the air flows (between cooling water pipes and metal strips 7) that the quotient L/d h  &lt; 15. So when L = 25 mm, the hydraulic diameter of said ducts must be smaller than or equal to 1.6 mm, the hydraulic diameter being defined as 4 times the surface divided by the circumference of the cross-section of the relevant duct. This means consequently an extremely fine division of the radiator, in which the metal strips 7 are situated only at a very small distance from each other (smaller than or equal to 0.8 mm). It has been found that in this manner a radiator is obtained having a cooling capacity per surface unit which is many times larger than that of known radiators. 
     The surprising effect is that said radiator, in spite of its fine division, is not polluted during use. Contaminations in the air have been found to collect at the area 9. This is a result of the fact that, whereas the air is deflected, the contaminations go straight forward due to their larger inertia and land in the channel 9. In order to even better check pollution, a layer of a fine gauze having a maximum mesh width of 1.5 mm may be provided on the outside of the elements, if desirable, which gauze simultaneously serves as a heat transmitting surface since it is in a good heat conducting contact with the metal strips. Alternatively, instead of the strips 7 it is possible to provide only a number of layers of gauze on the cooling water pipes. In addition, all possible combinations of strips and gauze may be used. 
     Although the channel 9 has certain advantages, for example as far as cleaning is concerned, it may be omitted in certain circumstances in which case the elements at that area are in direct contact with each other. The dirt will then accumulate of course in the corner formed, but if this is taken into account in calculating the radiator, this need not be a drawback. 
     It is shown diagrammatically in FIG. 3 that the channels 9 are open on their lower sides and communicate with an outlet channel 12 which is open on the radiator front side of the area 13. When the vehicle is stationary, any contaminations which have remained behind in the channels 9 will fall down and can disappear through the outlet channel 12. Also when the radiator is cleaned by spraying with water, said exhaust channel 12 may be useful. Since the exhaust channel 12 opens at the area 13 on the front of the radiator, the pressure in the channels 9 will not experience any drawback from the open condition of the channels 9 on their lower side. 
     FIG. 4 shows how the elements 1 may be arranged in parallel, if desirable, so that, as it were, a crenel-shaped radiator is obtained.