Patent Publication Number: US-2017370609-A1

Title: Enthalpy Heat Exchanger

Description:
TECHNICAL FIELD 
     A counter-flow enthalpy exchanger, having a parallelogram-shaped central part, at whose ends it is joined in the flow direction through the exchanger by end parts which become narrower in the direction from the central part, whereby for the separation of the flow of the heat transfer medium in the direction from the inner space to the outer space are arranged vapour-permeable lamellae with identical contours which are sealed with respect to the flowing medium and have shaping means for generating turbulent flow. Moreover, every two adjacent lamellae in the central part form one inter-plate flow channel. 
     BACKGROUND ART 
     Known are regenerative heat exchangers, through which a heat transfer medium flows countercurrent inside spaces which are separated from each other by heat transfer walls. 
     An example of such a regenerative system is a device according to document WO2013091099A1. Heat-transfer surfaces of the actual exchanger are water vapour-permeable pleated sheets stacked in layers on top of each other in such a manner that they form a system of parallel channels which are separated from each other. Through them flow against each other the warmer fluid giving off heat and vapour and the cooler fluid receiving heat and vapour. The outlets and inlets are performed by means of distribution systems connected to both sides of the exchanger. The above-mentioned device is substantially characterized by laminar flow of the heat-transfer medium in the straight channels of the exchanger. However, this is not favorable especially with regard to the efficiency of the exchanger itself. Moreover, the structure of the individual layers formed by connecting the actual heat-transfer surface to the system of fluid supply and exhaust is relatively complicated. 
     The exchanger according to patent CZ 300299 B6 comprises a frame in which are arranged layers of thin lamellae, in which is alternately led the air exiting the room and the air entering the room. Each of the lamellae has an inlet and outlet area for the flowing medium in its end parts. The middle part of the lamellae is formed by channels whose task is to change the direction and velocity of the air flow, since the turbulence of a gaseous medium significantly increases the efficiency of heat exchange. The material of the walls of the lamellae is a thin metal or plastic film. Such a material has sufficient rigidity and therefore there is no need to reinforce it by frames or other reinforcing elements. This is advantageous with respect to achieving the maximum possible area of the efficient surface of the exchanger. 
     Nevertheless, apart from heat exchange, and in the winter season apart from heating the supply air by the exhaust air, the requirement that devices for air-conditioning of enclosed spaces should meet is prevention of moisture leakage. By making use of the exiting heat it is necessary to prevent moisture loss in this case and pass it from the stream of the exiting air to the supplied air. The devices fulfilling this task are the so-called enthalpy exchangers. It is evident that between the exiting and entering air there cannot be dividing walls that are impermeable to the air or moisture. 
     Between two separated inner spaces of a counter-flow enthalpy exchanger, through which the air flows in counter-current configuration, it is necessary to use a wall with a function of a membrane permeable to water vapour and not to the air. The air exiting the heated space transfers heat and at the same time also moisture to the air entering the room, which has a positive effect of preventing drying of the air in the room. Due to low rigidity of the material of the vapour-permeable membranes it is required that the membrane is reinforced by a supporting means to which it is attached. 
     The supporting part of a lamella of an enthalpy exchanger according to the background art is formed by reinforcing supporting distance grids, which form rigid plastic skeletons coated with a material fulfilling the function of a vapour-permeable membrane. Owing to the fact that the membrane is glued onto the skeleton, the skeleton decreases the functional area of the lamella, thereby decreasing the efficiency of both heat and moisture transfer. 
     The aim of the invention is to increase the efficiency of the enthalpy exchanger without increasing outer dimensions of the exchanger and without a significant increase in the costs of production of its lamellae. 
     PRINCIPLE OF THE INVENTION 
     The aim of the invention is achieved by an enthalpy exchanger comprising flow lamellae for two counter-flow streams of the medium, whose principle is the fact that a lamella is made as a self-supporting moulding of the central part and end parts without a reinforcing supporting grid, whereby the lamella is vapour-permeable. Such lamellae do not contain reinforcing elements, for example grids which decrease the heat-transfer and vapour-transfer area. 
     The end parts of the lamella comprise protrusions situated in the direction the heat-transfer medium flow between the central part and a corresponding inlet or outlet of this medium. That decreases resistance to the flow in these sections, by which means the effectiveness of the exchanger is higher. 
     The self-supporting moulding is composite, whereby one of its components is formed by a supporting nonwoven layer, which is connected to a vapour-permeable membrane. In a preferred embodiment, the material of the vapour-permeable membrane is sulfonated block copolymer, which has very good properties in terms of vapour permeability, strength and dimensional stability both in dry and wet conditions. 
     The connection of the supporting nonwoven layer with the vapour-permeable membrane is accomplished by moulding or welding or gluing or dipping. This is favourable from the point of view of technology, since it can be performed on known coating or laminating devices. 
     The lamellae are mutually connected at least in some parts of the circumference by welding or gluing by means of airtight weld joints. In this manner, it is possible to obtain a perfect separation of the incoming and outgoing medium in an economical manner. 
     Preferably, the lamella is made by pressing from a planar blank held along the circumference between forming plates having a temperature higher than 40° C. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       The device according to the invention is schematically represented in the drawing, where 
         FIG. 1  shows an oblique view of an enthalpy exchanger with the directions of the working medium flow, 
         FIG. 2  illustrates a lateral view of the enthalpy exchanger from  FIG. 1  in the direction P 1 , 
         FIG. 3  shows a plan view of a lamella, 
         FIG. 4 a    shows a cross-section C-C from  FIG. 3 ,  FIG. 4 b    represents a detail of the curve of the protrusions of the central part of the lamella from  FIG. 3 , 
         FIG. 5  shows an oblique view of the part of the exchanger comprising four lamellae in their joined state and 
         FIG. 6  is a detail of the end part from  FIG. 5 . 
     
    
    
     SPECIFIC DESCRIPTION 
     An enthalpy exchanger is a device serving to transfer heat and humidity from a gaseous medium coming out of the inner working space to a gaseous medium coming from the outer space into the inner space. 
     The basic constructional element of an enthalpy exchanger  1  according to the invention is a profiled plate, hereinafter referred to as a lamella  10 . The lamellae  10  are stacked in layers on top of each other, whereby adjacent lamellae are along part of their circumferences connected to each other. Thus, alternating flow interplate spaces arise between pairs of lamellae  10  forming channels  2  for the flow of a gaseous medium in the direction A from the enclosed space to the outer space and channels  3  for the flow of the gaseous medium in the direction B from the outer space to the enclosed space. These lamellae allow heat transfer from the heated and humid medium which is taken away, e.g., from an air-conditioned space to a cool and usually dry medium supplied from outside. The lamellae  10  is substantially a moulding made of a planar blank comprising protrusions and recesses on both sides. 
     A set of lamellae  10  is inserted and fixed in a casing  100  of the enthalpy exchanger  1 . Both outer lamellae  10 ′, which are adjacent to the side walls inside the casing  100 , contribute to the desired character of the medium flow in both end flow spaces, heat and moisture exchange through them virtually does not occur. 
     A diagram of the exchanger is shown in  FIGS. 1 and 2 . In these hatched are the areas between the lamellae  10 , or  10 ′, the areas between inlet or outlet nozzles in the flow inter-plate spaces, while the closed flow inter-plate spaces are not hatched. 
     The lamella  10  consists of two components. The first component is a supporting layer of nonwoven fabric, which is coated with a vapour-permeable membrane. Preferably, the membrane is made of sulfonated block polymer. The connection of the supporting nonwoven layer with the vapour-permeable membrane is accomplished by moulding or gluing or dipping. Sulfonated block polymer is advantageous with respect to the degree of vapour permeability, rigidity and dimensional stability both in dry and wet conditions. Moreover, it is also advantageous in terms of the production technology of the membrane, which can be implemented on known coating or laminating devices. Thus, protrusions and recesses can be formed by compressing in the area of the resulting lamella, their purpose being to generate turbulent flow of the medium passing through the gap which constitutes a flow channel between two adjacent lamellae  10   10 ′. Generally, turbulent flow increases heat transfer and moisture passage efficiency of the flowing medium separated by the lamella. 
     A major advantage is the self-supporting structure of the lamella  10 . This structure does not contain a reinforcing grid, which in other structures decreases the efficient area for the exchange of heat and humidity between the exhaust and supply stream of the gaseous medium. 
     One clear area in the casing  100  of the exchanger  1  is formed by two lamellae  10 , which have the same area contour but which differ by the direction of the bending of peripheral edges, by means of which the lamellae are mutually connected. In the description of the shape, to distinguish these two types according to requirements, they will be hereinafter referred to as lamella  10   x  and  10   y.    
     In an exemplary embodiment, the central part  11  of the lamella  10  has the shape substantially of a square or rectangle, which is joined in the direction of the length of the lamella by the end part  12 ,  13 , whose area becomes narrower in the direction from the central part. In an illustrative embodiment, the areas of the end parts are triangular. This facilitates an arrangement of the input and output flow of the medium through the exchanger diagonally (see  FIG. 1 ). The flow space between two adjacent lamellae  10  is not divided by any closed partition. It is, of course, possible for the shape of the central part to be also a rectangle or rhomboid with, for example, adjoining unequal-sided triangles of the end parts  12 ,  13 . 
     The central part  11  of the lamella  10   x  is in an example of embodiment according to  FIG. 3  shaped by longitudinal parallel undulated protrusions  111 . The curve of their ridges  111 ′ is in the plane of the surface of the lamella  10  substantially a sinusoid Sx. The distance between two neighbouring ridges  111 ′ is a pitch R. The ridges  111 ′ of the protrusions  111  are indicated by the solid line, recesses in the middle between them form protrusions on the other side of the lamella  10 . The cross-section C-C of the central part from  FIG. 3  is shown in  FIG. 4 a   . In an exemplary embodiment, the height v of the wave of the protrusions  111 , that is the maximum thickness of the lamella  10 , is 3.5 mm. The sinusoid Sx of the ridge  111 ′ of the protrusions  111  starts in the part adjacent to the end part  12  with a lower peak DV. In the part adjacent to the end part  13  the sinusoid Sx ends with an upper peak HV. 
     In the case of the lamella  10   x  of the first type, the edge  123  of the end part  12  (in  FIG. 3  up on the left) is bent upwards, the second edge  124  of the end part  12  is bent downwards. The edge  133  of the end triangular part  13  parallel to the edge  123  of the end triangular part  12  is bent upwards, while the edge  134  of the end triangular part  13  parallel to the edge  124  of the end triangular part  12  is bent downwards. 
     In the case of the lamella  10   y  of the second type, the sinusoid Sy of the ridge  111 ″ of the protrusions  111  is shifted relative to the position of the sinusoid Sx of the lamella  10   x  by half the length λ of the wave of the sinusoid Sx, Sy so that it begins in the part adjacent to the end part  12  with the upper peak HV and in the part adjacent to the end part  13  ends with the sinusoid Sy with the lower peak DV ( FIG. 4 b   ). At the points where the sinusoid Sx and Sy cross or touch each other, the adjacent ridges  111 ′,  111 ″ touch each other as well. 
     The end triangular parts  12 ,  13  are provided with moulded straight elongated discontinuous protrusions  121 ,  131 , which have the direction of the medium flow in this part of the flow space and which on the opposite side of the lamella form recesses  122 , 132 , which do not worsen the flow on this opposite side of the lamella, although they are perpendicular to this direction. 
     The height of the protrusions  121 ,  131  and recesses  122 ,  132  of the end parts  12 ,  13  is at the most 1.7 mm. 
     The thickness and planar dimensions of the lamella  10 , the height of the protrusions  121 ,  131 , the height v of the wave of the undulated central part  11  in the embodiments according to the technical solution (not shown) may change, without exceeding the scope of protection defined by patent claims. 
     In the case of the lamella  10   y  of the second type, the edge  123  of the end part  12 , which is parallel to the protrusions  121 , is bent downwards, whereas the second edge  124  of the end part  12  is bent upwards. The edge  133  of the end triangular part  13  which is parallel to the edge  123  of the end triangular part  12 , is bent downwards, while the edge  134  of the end triangular part  13 , which is parallel to the edge  124  of the end triangular part  12 , is bent upwards. 
       FIGS. 5 and 6  illustrate stacking the individual lamellae  10  on top of each other and their connection. In an exemplary embodiment, the enthalpy exchanger  1  comprises twenty lamellae  10 .  FIG. 4  illustrates four lamellae, which are indicated from top to bottom as  10   x   1 ,  10   y   2 ,  10   x   3 ,  10   y   4 .  FIG. 6  shows a detail of the left side of the set of the lamellae. 
     The circumferences of the assembled lamellae touch along the longitudinal sides  112  of the central part  11 , where they are cement, forming opposite walls  113  of the casing  100  of the exchanger  1 . Similarly, also the ends of the end parts forming the narrow faces  114  of the casing  100 . 
     Adjacent lamellae  10  are alternately closed by the edges  123 ,  124 ,  133 ,  134  according to  FIGS. 5 and 6 . The edges  123 ,  124 ,  133 ,  134  are connected by welding or gluing. 
     On the left-hand side of  FIG. 5  and  FIG. 6  there are welded edges  123  of the lamellae  10   y   2 ,  10   x   3 , by which means the space between these lamellae is closed, whereas between the edges  123  of the lamellae  10   x   1  and  10   y   2  the inlet into or outlet out of the space is opened. Also between the edges  124  of the lamellae  10   x   3  and  10   y   4  there is an inlet or outlet opening. Further on, there is an illustration of two welded edges  124  of the lamellae  10   x   1  and  10   y   2 ,  10   x   3  and  10   y   4 . 
     On the right-hand side of  FIG. 5  there is a visible welded joint of the edges  133  of the lamellae  10   y   2  and  10   x   3  and inlet nozzles between the edges  133  of the lamellae  10   x   1  and  10   y   2 ,  10   x   3  and  10   y   4 . On the contrary, the invisible art of the circumference of the end part  13  contains analogically to a part of the circumference of the end part  12  with the edges  124  (a front view in  FIG. 6 ) two welded edges  134  of the lamellae  10   x   1  and  10   y   y ,  10   x   3  and  10   y   4 . Between the edges  134  of the lamellae  10   y   2 ,  10   x   3  there is also an inlet or outlet opening. 
     Beside the major advantage, which is the self-supporting structure of the lamella  10  and therefore the absence of a reinforcing grid, the enthalpy exchanger  1  entails an advantage of a relatively long path, on which the exchange of heat and humidity between counterflow streams of the medium takes place. Beside irregularities of the surface of the lamellae  10  of the central part  11  contributing to a considerable extent to the effectiveness of the exchange of heat and humidity, further increase in the efficiency is achieved by reducing the resistance to the flow of the medium in the end parts  12 ,  13  by means of the shape and particularly the direction of the protrusions  121 ,  131  in these parts. 
     LIST OF REFERENCES 
     
         
           1  enthalpy exchanger 
           10  lamella ( 10 ′,  10   x ,  10   y ,  10   x   1 ,  10   x   3 ,  10   y   2 ,  10   y   4 ) 
           100  casing of the exchanger 
           11  central part (of the lamella) 
           111  protrusion (of the central part of the lamella) 
           111 ′ ridge of the protrusion (of the central part of the lamella) 
           111 ″ ridge of the protrusion (of the central part of the lamella) 
           112  longitudinal side of the central part 
           113  wall of the casing (of the exchanger upper, lower) 
           114  narrow face (of the casing of the exchanger front, rear) 
           115  side wall (of the casing of the exchanger) 
           12  end part (of the lamella) 
           121  (straight) protrusion (in the area of the end part) 
           122  (straight) recess (in the area of the end part) 
           123  edge (of the end part) 
           124  edge (of the end part) 
           13  end part (of the lamella) 
           131  (straight) protrusion (in the area of the end part) 
           132  (straight) recess (in the area of the end part) 
           133  edge (of the end part) 
           134  edge (of the end part) 
           2  channel (flow in direction A) 
           3  channel (flow in direction B) 
         A direction of flow (from the enclosed space outwards) 
         B direction of flow (from the outer space to the inner space) 
         DV lower peak (sinusoid) 
         HV upper peak (sinusoid) 
         R pitch distance of the crests (of the protrusions of the central part) 
         S x  sinusoid 
         S y  sinusoid 
         v height of the wave of protrusions (of the central part) 
         λ length of the wave of sinusoid S x , S y