DE9318338U1 - Plate heat exchanger in modular design for recuperative heat exchange in the counterflow principle between gaseous media - Google Patents

Description

it 11/11/93

HEINZ SCHILLING KG

Development and planning
Möhlenring 53, ^7906 Kempem, Telephone: 02152/53002

Plate heat exchanger in modular design for recuperative heat exchange using the countercurrent principle between gaseous media.

The invention relates to a plate heat exchanger in modular design for recuperative heat exchange using the countercurrent principle between gaseous media according to the preamble of claim 1.

According to the state of the art, plate heat exchangers for gaseous media are known, which generally consist of prefabricated plates, profiles and frame components which are glued, pressed, welded or soldered to form the entire plate heat exchanger. The manufacturing and production method is efficient, but has the decisive disadvantage that these plate heat exchangers cannot be dismantled for cleaning purposes.

If the plate heat exchanger is to work on the countercurrent principle, to connect the previously known plate heat exchangers to the air duct system, at least one air deflector is required for each media flow or at least two air deflectors for one media flow.

A design without air redirection is known (Heat recovery in ventilation systems, H.Jüttemann, CF. Müller-Verlag, Karlsruhe, 1977, p. 111).

With the separating surface material used, reaction lengths of up to 3 m are required for high exchange rates in the countercurrent principle. Since the plate heat exchangers cannot be dismantled, cleaning would have to be carried out from the channel connections. However, air deflections and long reaction lengths make necessary cleaning more difficult, only take place inadequately or are not possible at all. With a reaction length of 3 n>, cleaning is difficult even without air deflection.

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This makes its use in buildings with increased cleanliness requirements, such as hospitals, but also for residential ventilation, hygienically questionable.
In the past, if contamination affected operation, the heat exchanger had to be completely replaced.

In order to obtain gas-tight plate heat exchangers, the partition walls must be soldered or welded, which on the one hand can damage a paint coating applied for corrosion protection and on the other hand significantly increases the manufacturing effort.

In the case of plate heat exchangers based on the countercurrent principle and high temperature exchange rates, condensation of the air humidity occurs on the exhaust air side when used as heat recovery units in ventilation systems.
At outside air temperatures below O ⁰ C there is a risk of condensation.

condensate freezing. Due to this freezing, the frozen condensate builds up on the separating surfaces until the air gap is "closed". To remedy this, preheaters and partially electrically heated automatic defrosting systems in the exhaust air have been installed in front of the heat recovery unit in the outside air, which requires additional energy and control technology. Another possibility provides for limiting the temperature exchange rate or passing part of the outside air past the heat exchanger, which represents the same energy. Despite the only slightly smaller flow pressure loss, the annual recovery remains much lower and either a higher temperature level or more heat exchanger surface must be used for reheating, so that overall efficiency remains low.

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The state of the art gives rise to the task of creating a highly efficient, freezing-proof plate heat exchanger for gaseous media that can be dismantled at any time (e.g. for cleaning) and reused over and over again and that can be manufactured using simple production techniques.

The plate heat exchanger should be connected to the ventilation duct system without air diversions so that cleaning can be carried out even when installed.

The nature of the separating surfaces should be able to be selected and adapted separately according to the properties of the media flows. The length of the plate heat exchanger in the direction of air and the distance between the separating surfaces should be freely selectable so that any required temperature exchange level can be achieved with a low pressure loss on the air side.

The plate heat exchanger should also be able to transfer heat between media flows with different operating pressures.

The object is achieved according to the invention by the features proposed in the characterising part of the protection claims.

By dividing the plate heat exchanger (Fig. 5.6) into stackable, dismantable and reassemblable interface modules (Fig. 1, 2, 3), the plate heat exchanger can be dismantled for cleaning purposes at any time. After releasing the pressing, the end plates (6) can be removed and the plate heat exchanger can be dismantled. The interface modules (Fig. 1, 2, 3) can be completely cleaned using suitable means and methods. The interface modules can then be stacked and pressed together again and can therefore be used again and again.

The opposite connection of the media flows (8a, 8b, 8c) to the plate heat exchanger enables countercurrent flow.

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Because the plate heat exchanger can be dismantled and reassembled at any time, the length of the interface modules can be freely selected, so that the ratio of length to width means that the heat exchange takes place in countercurrent. The high degree of temperature exchange that can be achieved in this way has an impact on efficiency.

By arranging the sealing surfaces (2) in the edge area and by stacking the normal (1) and mirror versions (5) of the separating surface modules (Fig. 1,3) alternately, the inflow (3a) and outflow openings (3b) of the media flows are automatically formed. The plate heat exchanger can now be connected to the ventilation duct system without air diversion using standard flanges (9). If inspection openings are provided in front of and behind the plate heat exchanger, the plate heat exchanger can be cleaned against the direction of the air using compressed air or a steam jet. If this type of cleaning is no longer sufficient, e.g. in the case of deposits, the plate heat exchanger can be dismantled into the individual separating surface modules and then cleaned. Individual separating surface modules that can no longer be cleaned or are defective can be easily and inexpensively replaced.

The sealing surfaces (2) can also be applied in such a way that, by stacking them alternately, intermediate branches (3c) are created for feeding and discharging partial flows (8c) for any one or both media flows (8a, 8b) (see Fig. 7). If such an intermediate branch is created for the outside air flow, part of the already heated air can be fed back in front of the plate heat exchanger and mixed with the unheated outside air. If a certain amount is branched off at the right place, the mixed outside air in front of the plate heat exchanger reaches a temperature at which the risk of condensate freezing can be ruled out.

The calculations are carried out according to the rules of thermodynamics,

The gas tightness is achieved by more or less strong pressing of the stacked interface modules (Fig. 6,7) (1,5) between the rigid end plates (6). The applied sealing surfaces seal the media flows to the outside and between the heat-exchanging

The plate heat exchanger can be adapted to the respective operating pressure using the pressure and the sealing surface width.

Since the reaction length can be freely selected, any desired temperature exchange degree can be achieved. However, high exchange degrees require long reaction lengths, so that the ratio between the length and distance of the separating surface modules leads to a high pressure loss. This can be solved according to the invention by also allowing the distance between the separating surfaces to be freely selected. This is taken into account in the design by the thickness of the pressure-resistant, inner sealing surface component.

The possibility of combining the countercurrent principle with freely selectable reaction lengths, separation surface distances and the possibility of return air bypass ensures a high degree of exchange with low pressure loss, i.e. low fan work, and without the risk of icing. The fan work requires electrical energy, which in turn is generated from heat in power plants with a certain efficiency. With an average power plant efficiency of around 0.33 and further losses during idle operation, starting and shutting down and distribution, four units of heat are required for one unit of electricity. If the ratio of heat recovery to fan work is higher than four, the heat exchange can be considered efficient. A ratio of over 10 can be described as highly efficient. With the proposed features, a plate heat exchanger can be built whose design meets the condition of being highly efficient.

To make assembly easier, the separating surface modules have features such as bevels (4a), notches (4b), centering nipples or color markings. The separating surface modules (Fig. 1,2,3) each have bevels (4a) or notches (4b) on one side, which can be of different widths and are located at different distances from the edge. The separating surface module closest to the stack (Fig. 5. Pos. 1) has a notch where the separating surface module deeper in the stack (Fig. 5. Pos. 5) has a bevel, or vice versa.

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If the notches and edges on one side are wider or narrower or further or closer to the edge than on the opposite side, the correct assembly of the separating surface modules, which are stacked alternately in normal (1) and mirror image (5) versions, is guaranteed. This also ensures that the separating surface modules are stacked exactly on top of each other. A color marking is also sufficient for correct assembly.

Heat exchange between media with different operating pressures can be achieved without bulging of the separating surfaces towards the lower pressure side by applying small, short pieces (10) of the sealing surfaces (2) or made of suitable materials to the separating surface modules {Fig. 1,2,3).

Claims (1)

HEINZ SCHILLING K Ö ** Development and planning
Möhlenring 53, 47906 Kempein, Telephone: 02152/53002 Protection claims: 1. Plate heat exchanger in modular design for recuperative heat exchange using the countercurrent principle between gaseous media, characterized, that the heat exchanger (Fig. 5.6) consists of stackable, dismantable and reassemblable separating surface modules (Fig. 1,2,3) on which sealing surfaces (2) are applied in such a way that by alternately stacking normal (1) and mirror image (5) versions of the separating surface modules (Fig. 1,2,3) the inlet (3a) and outlet openings (3b) and also intermediate branches (3c) for the media flows (8a, 8b, 8c) are inevitably formed, the media flows seal themselves to the outside and between the heat-exchanging media, a countercurrent flow of the media flows is formed and the separating surface modules (Fig. 1,2,3) are kept at the desired distance. 2. Plate heat exchanger according to claim 1
characterized in that the separating surface modules (Fig. 1, 2, 3) have devices in the form of folds (4a), centering nipples, notches (4b) or color markings, so that only right-angled, congruent and correct-side stacking is possible. 3· Plate heat exchanger according to claims 1 and 2
characterized in that the separating surface modules (Fig. 1, 2, 3) can be pressed together again at any time after stacking between two equally long, rigid end plates (6). 11/11/93 h. Plate heat exchanger according to claims 1 to 3
characterized in that the interface modules (Fig. 1,2,3) are variable in length, width and distance depending on the required temperature exchange rate, the permissible flow pressure loss and the volume flow. 5. Plate heat exchanger according to claims 1 to k
characterized in that the interface modules (Fig. 1,2,3) are made of the appropriate materials depending on the operating conditions, type and properties of the heat-exchanging media (8a, 8b, 8c) or are coated differently on one or both sides. 6. Plate heat exchanger according to claim 1 characterized in that the sealing surfaces (2) applied to the separating surface modules (Fig. 1,2,3) consist of two or more enclosing components (Fig. k), (7a,7b), whereby the inner component (7b) is designed to be so pressure-resistant that the sealing surfaces (2) simultaneously ensure the desired distance between the separating surface modules (Fig. 1,2,3), which can be determined separately for each media flow. 7. Plate heat exchanger according to claims 1 and 6
characterized in that the sealing surfaces (2) are adapted in terms of sealing width and material, which can be selected separately for each media flow, depending on the operating conditions, type and properties of the heat-exchanging media (8a, 8b, 8c), flow velocity and differential pressure between the environment and the media flows.