Heat Exchanger with Heat Exchanger Rods

The invention relates to a heat exchanger comprising at least one support and having heat exchanger rods arranged on the support, a heat exchanger system, a ventilator and a double ventilator.

According to the current legal situation, renovated and new dwellings must be virtually air-tight. The previously common gap ventilation is therefore increasingly being replaced by active ventilation concepts. In this context, use is made of dwelling ventilation systems whose task is to feed in external air as required and to transport stale air to the outside.

Such ventilation systems are based on flow through the entire living area as required. To minimize a space requirement, decentralized systems comprising heat exchangers have already been developed, as described, for example, in DE 10 2011 080 358 and in DE 10 2014 200 538. In this case, integral ceramic heat exchangers are preferably used as heat exchangers. The production of ceramic heat exchangers of this kind is expensive and energy-consuming and, in addition, it is only with difficulty that the length of ceramic heat exchangers can be adapted to installation circumstances after their production.

In the text which follows, the term “gas” denotes not only a single gas but also mixtures of several gases.

Heat exchangers are devices for transferring thermal energy from one substance stream to another.

Regenerators are heat exchangers which use a heat storage device in order to store thermal energy of a hotter medium and then transfer it to a colder medium. In particular, regenerators are used in the form of gas-solid body heat exchangers. Gas-solid body heat exchangers are designed to transfer thermal energy from a hotter gas to a colder gas. During this process, the thermal energy of the hotter gas is first of all stored temporarily in a heat storage device and then released to the colder gas. For this purpose, the hotter gas first passes through the heat exchanger and heats the heat storage device. The colder gas then flows through the heat exchanger and absorbs the thermal energy stored by the heat storage device, as a result of which the heat storage device cools down and the previously colder gas heats up. In general, the two gases pass through the regenerator with a time delay and in the opposite direction.

Recuperators are devices for transferring thermal energy from a hotter gas to a colder gas, wherein there are dedicated flow ducts that are fluidically separated from one another but thermally coupled for the two gas flows. Owing to the thermal coupling of the two flow ducts, the hotter gas continuously releases thermal energy to the colder gas without necessarily requiring a heat storage device. In general, the two gas flows are passed through the recuperators in opposite directions.

Relevant parameters for the efficiency of heat exchangers are material properties such as the thermal conductivity of the heat storage device and the geometrical guidance of the media through the heat exchanger.

For heat exchangers in regenerators, use is made, for example, of storage masses made of copper or ceramic storage masses on account of their good thermal conductivity.

In the field of living-space ventilation, it is customary to install systems consisting of heat exchangers and fans into house facades as ventilation and heat recovery systems. The heat exchangers used in such systems are often regenerators since their offset mode of operation is suitable for this area of application. Warmer air, which may contain less oxygen, is discharged through the heat exchanger from an interior into an external environment by means of a fan. In this case, the heat storage device of the heat exchanger stores a large proportion of the thermal energy of the interior air discharged. Subsequently, colder fresh air containing more oxygen is fed through the heat exchanger into the interior from the external environment by means of the fan. During this process, the colder fresh air absorbs the thermal energy temporarily stored in the heat storage device and warms up. As a result, temperature-controlled fresh air containing more oxygen is fed to the interior, as a result of which the interior does not cool down and heating energy can be saved. An efficient heat exchanger with lower material and production costs is desirable.

It is here that the invention intervenes, its object being to provide a heat exchanger that is improved in respect of costs and/or heat recovery.

According to a first aspect of the invention, this object is achieved by a heat exchanger designed as a gas-solid body heat exchanger which comprises at least one support. A multiplicity of heat exchanger rods is arranged on the at least one support. The heat exchanger rods extend from the support.

The invention is based on the recognition that frequent collisions between the gas and the heat exchanger are important for effective heat transfer of thermal energy from a gas to a heat exchanger and from the heat exchanger to a gas. This is promoted especially by flow ducting of the medium through the heat exchanger which as far as possible does not pass in a straight line through the heat exchanger but guides the gas through the heat exchanger via winding or branched channels, for example. This results in frequent collisions between the gas and the heat exchanger and, as a result, in heat transfer between the gas and the heat exchanger. Moreover, turbulent flow of the medium through the heat exchanger is particularly conducive to effective heat transfer since it promotes frequent collisions between gas particles and the heat exchanger.

Based on this insight, the invention includes the recognition that the construction according to the invention of the heat exchanger with a multiplicity of heat exchanger rods greatly deflects a gas flowing through the heat exchanger in a flow motion and, since the gas repeatedly collides with the multiplicity of heat exchanger rods on account of the deflection, this results in particularly effective heat transfer between the gas and the heat exchanger rods.

Furthermore, the invention is based on the surprising insight that it is possible, in a heat exchanger with such a high efficiency in terms of heat transfer between a gas and a solid body, to dispense with materials of particularly good thermal conductivity in the heat exchanger, thereby making it possible to reduce costs in production and materials since, by virtue of the improved interaction in the heat exchanger between the gas and the solid body due to the increased number of collisions, it is possible to achieve sufficiently high levels of efficiency, even with materials with relatively low levels of thermal conductivity.

The at least one support can have a hollow profile or a solid profile. A support with a hollow profile can enclose a flow channel in its interior, wherein the flow channel can extend in the longitudinal direction of the support from one end face to another end face of the support. Such a flow channel can thus allow flow in the longitudinal direction of the supports. A plurality of supports having hollow profiles and arranged concentrically one inside the other can enclose a plurality of flow channels between them.

Advantageous developments of the invention can be found in the dependent claims and the following description and specify in detail advantageous possibilities for implementing the concept explained above within the scope of the stated object and with regard to further advantages.

At least one heat exchanger rod is preferably arranged in at least one plane arranged orthogonally to a longitudinal axis of the heat exchanger. A multiplicity of heat exchanger rods is preferably arranged in a multiplicity of respective planes arranged, in particular, orthogonally to the longitudinal axis of the heat exchanger.

In one preferred embodiment of the heat exchanger, the at least one support is an internal support, from the outer surface of which the heat exchanger rods extend, or an external support, from the inner surface of which the heat exchanger rods extend, or a middle support, from the inner surface and outer surface of which heat exchanger rods extend.

The external support and the middle support can each be formed by hollow profiles. Particularly in embodiments with a middle support and an external support, the middle support can have a smaller diameter than the external support, thus enabling the middle support to be arranged within the external support. The internal support can have a solid profile, which can be arranged within an external support and/or a middle support. In the case of a combination of an internal, a middle and/or an external support, the supports can be arranged concentrically one inside the other. In principle, the heat exchanger can have a single support or a combination of a plurality of supports, in particular situated concentrically one inside the other.

Thus, a heat exchanger can have just one external support or just one internal support, for example. A heat exchanger may also be formed by an external support and a middle support and an internal support which are situated concentrically one inside the other. It is also possible for a plurality of middle supports to be arranged between an external support and an internal support or only within an external support.

Particularly where a middle support is used, it is possible, in the case of a fluidically leaktight embodiment of the middle support, to enable guidance of two fluidically separated but thermally coupled air flows through the heat exchanger. In another embodiment, the at least one support may also have apertures.

The design of the at least one support as an internal, middle or external support provides many degrees of freedom in the functional configuration of the heat exchanger, by means of which its effectiveness can be enhanced. In particular, it is also possible, by combinations of different supports, to increase a density of heat exchanger rods of the heat exchanger and thus to enhance the efficiency of the heat exchanger. If a short length of the heat exchanger is required, it is possible, for example, to increase the density of the heat exchanger rods in the heat exchanger and to maintain a high efficiency of the heat exchanger.

In another advantageous embodiment of the heat exchanger, the heat exchanger rods are arranged in such a way that the heat exchanger rods form a continuous surface when considered in a plan view of an end face of the heat exchanger.

For effective heat transfer, it is advantageous for the gas to be deflected as often as possible in its flow motion. Gas molecules passing through the heat exchanger should preferably not be able to take any path on which no collisions or only a few collisions with the heat exchanger rods occur. Arrangement of the heat exchanger rods in such a way that they form a continuous surface in a plan view of the end face of the heat exchanger therefore leads to a high efficiency because direct routes through the heat exchanger without a collision are avoided.

In another preferred embodiment of the heat exchanger, one heat exchanger rod is covered by another heat exchanger rod in the plan view of the end face of the heat exchanger. A multiplicity of heat exchanger rods is preferably covered by a multiplicity of other heat exchanger rods in the plan view of the end face of the heat exchanger rod.

An offset arrangement of the heat exchanger rods is an even more powerful way of preventing straight-line paths through the heat exchanger. By virtue of the offset arrangement of the heat exchanger rods, gas molecules which pass through the heat exchanger will inevitably collide with a multiplicity of heat exchanger rods and be deflected, promoting improved heat exchange between the gas and the heat exchanger rods.

In the context of another advantageous embodiment of the heat exchanger, the external support forms a housing or is integrated into a housing. This advantageously results in a compact construction of the heat exchanger since, in addition to its function as a support for heat exchanger rods, the external support simultaneously also forms the housing of the heat exchanger.

In another advantageous embodiment of the heat exchanger, a plurality of the heat exchanger rods is arranged at uniform or nonuniform intervals with respect to one another on the support within at least one plane, which is preferably arranged orthogonally to the longitudinal axis of the heat exchanger, and/or the planes are spaced apart equally or unequally from one another. It is thereby possible to obtain both regular structures which, in particular, are easier to implement in terms of manufacturing, and irregular structures, which contribute to increased efficiency through increased nonuniform deflections of the gas flow.

In another advantageous embodiment of the heat exchanger, the at least one support has a circular, oval, rectangular or polygonal cross section.

In another advantageous embodiment of the heat exchanger, a plurality of the heat exchanger rods, in particular all the heat exchanger rods, are in each case of the same construction. This advantageously results in simplified manufacture of the heat exchanger rods.

In another advantageous embodiment of the heat exchanger, the heat exchanger rods each have a round, oval, rectangular or polygonal cross section, and the length of the heat exchanger rods is a multiple of the largest cross-sectional dimension of the heat exchanger rods.

By means of different cross sections of the heat exchanger rods, the gas flowing through the heat exchanger can be decelerated further and more strongly deflected. While smooth and streamlined cross sections are easier to manufacture, polygonal cross sections, for example, can ensure additional turbulence of the gas flowing through the heat exchanger at their corners. It is thereby possible to achieve a further increase in the efficiency of the heat exchanger. As an additional advantage of this further development there is an additional degree of freedom in the functional configuration of the heat exchanger, which allows consideration of simpler cross-sectional shapes and more complex cross-sectional shapes of the heat exchanger rods. In particular, combinations of heat exchanger rods with different cross-sectional shapes may also increase the efficiency of the heat exchanger by more complex deflection of the gas flowing through the heat exchanger.

In the context of another preferred embodiment of the heat exchanger, at least one heat exchanger rod has a constant or a varying cross-sectional profile over its length. In this case, the variation in the cross section over the length can be continuous or discrete, or the at least one heat exchanger rod has a cross-sectional profile over its length which is a combination of regions of constant cross sections and regions with cross sections that vary continuously or discretely over the length.

This results in a further degree of freedom in the functional configuration of the heat exchanger in respect of flow deceleration and deflection of the gas by the heat exchanger rods. Different cross-sectional profiles of the heat exchanger rods over the length allows greater deflection and deceleration of a flow passing through the heat exchanger, thereby making it possible to achieve higher efficiency on account of greater heat transfer between the gas and the heat exchanger rods. By way of example, heat exchanger rods can have a studded and/or corrugated surface and/or a ridged surface. Cross-sectional profiles of the surfaces of the heat exchanger rods can be formed by various combinations of raised portions and recesses on their outer surfaces.

Another preferred embodiment of the heat exchanger envisages that the heat exchanger rods are rectilinear or bent or spiral-shaped. This results in a further degree of freedom in the functional configuration of the heat exchanger, which can contribute per se and especially in combination with other embodiments of the heat exchanger to an increase in the efficiency of the heat exchanger. Spiral heat exchanger rods cover a larger region of the flow cross section in comparison with rectilinear heat exchanger rods and thus ensure greater deflection and deceleration of the gas, as a result of which the efficiency of the heat exchanger is increased. In particular, spiral heat exchanger rods, for example, with a studded surface, for example, can further increase the efficiency of the heat exchanger. Moreover, combinations of straight and/or bent and/or spiral heat exchanger rods are also possible in a heat exchanger.

In addition, a preferred embodiment of the heat exchanger envisages that at least one heat exchanger rod is hollow. Hollow heat exchanger rods allow cost savings in terms of materials and, as a result, more advantageous manufacture. Moreover, hollow heat exchanger rods, especially when combined with a hollow support, enable an additional air flow or temperature-control medium to be carried within the structures of the heat exchanger. This can contribute to an increase in efficiency.

In another preferred embodiment of the heat exchanger, the heat exchanger rods all have the same length, or a plurality of heat exchanger rods has different lengths.

This results in a further degree of freedom in the functional configuration of the heat exchanger. Through the use of heat exchanger rods of different lengths, it is possible to vary the covering by the heat exchanger across the cross section in the plan view as seen from the end. It is thereby possible to obtain greater coverage by heat exchanger rods in those regions in which higher flow velocities or higher flow rates are to be expected. In this region, there is thus an increased interaction and there are more deflections in regions in which the through flow is poorer, e.g. on account of dead zones of a fan used with the heat exchanger.

In another preferred embodiment of the heat exchanger, a plurality of heat exchanger rods is mounted individually on the support and/or a plurality of heat exchanger rods grouped together into heat exchanger groups is mounted on said support.

Densely packed groups of heat exchanger rods can bring about greater deceleration and deflection of the gas than individual heat exchanger rods and can thereby contribute to improved efficiency of the heat exchanger.

In another preferred embodiment of the heat exchanger, at least one of the heat exchanger rods comprises a ceramic, a polymer material, in particular polystyrene or ABS, or a metallic material, in particular stainless steel.

With the construction according to the invention, a wider selection of materials with different levels of thermal conductivity can be used than with conventional heat exchangers. This provides the advantage of material selection as required and, as a result, the possibility of cost savings on the production side and on the materials side. Heat exchanger rods made of ceramics or of metallic materials have better thermal conductivity and therefore have a higher material-related efficiency as regards the absorption and dissipation of heat. Owing to the high number of collisions between the gas and the heat exchanger rods resulting from the construction of the heat exchanger, efficient heat transfer can be achieved even without materials that have good heat-conducting properties, and it is therefore possible, for example, to use inexpensive plastics that can be handled in a very flexible way during manufacture, in particular polystyrene or acrylonitrile butadiene styrene copolymer (ABS).

In another embodiment, at least one of the heat exchanger rods has a basic structure made of plastic and is at least partially coated with a material of relatively high thermal conductivity.

There is a further preference for an embodiment of the heat exchanger in which the heat exchanger rods are arranged in sockets on the support. In terms of manufacture, this provides the possibility of manufacturing the heat exchanger rod separately from the supports. As a result, the heat exchanger rods can be manufactured from a different material than that of the supports. There is furthermore the possibility of simply replacing damaged heat exchanger rods subsequently with undamaged heat exchanger rods or of exchanging a number of heat exchanger rods with other heat exchanger rods. It is thus possible, in the context of this embodiment, for example, to exchange heat exchanger rods made of plastic with heat exchanger rods made of ceramics or to exchange rectilinear heat exchanger rods with spiral heat exchanger rods. In particular, this provides the possibility, when using a support that is identical in all cases, of using different heat exchanger rods to adapt to the usage requirements.

In one alternative embodiment of the heat exchanger, the support and the heat exchanger rods are manufactured together in integral form.

Integral manufacture can be achieved, for example, by means of additive manufacturing methods, e.g. by means of 3D printing or stereolithography. In comparison with separate manufacture of the support and the heat exchanger rods, it is possible here to eliminate the assembly step in which the supports are fitted with heat exchanger rods.

In the context of another preferred embodiment of the heat exchanger, the heat exchanger has at least one dividing wall over the entire longitudinal axis of the heat exchanger for the fluidically separate guidance of two air flows.

By way of example, the dividing wall can be formed by a middle support with, for example, an annular cross section which is positioned within an external support or a housing. In addition, an internal support can be positioned within the middle support. The middle support then fluidically separates an outer air flow between the external support or housing and the middle support and an inner air flow in the middle support or between the middle support and the internal support. Here, the middle support can be constructed from a material which is at least slightly thermally conductive and can thus thermally couple the two air flows to one another.

However, the at least one dividing wall may also be a separate component which adjoins the at least one support and fluidically separates two air flows. Here, the at least one dividing wall can be constructed from a material which is at least slightly thermally conductive and can thus thermally couple the two air flows to one another.