Cross-flow heat exchanger with bypass-valve

(57) The present invention includes a cross flow heat exchanger for use in a space heating system adapted for heating air by means of a burner; which heat exchanger comprises two physically separated through-flow circuits thermally coupled by a number of parallel walls, which circuits are interwoven with each other and are transversely flowed through, respectively (1) an air flow from an outside air inlet to an outlet to the space to be heated (2) a gas flow from an inlet for, for example, hot flue gases from the burner to a exhaust for flue gases to the outside, or air from the room to an exhaust for the outside.

NL C 1007298

The content of this patent differs from the original filed description with claim (s) and possible drawing (s). The documents originally submitted can be viewed at the Industrial Property Office.

CROSS-FLOW HEAT EXCHANGER WITH BYPASS VALVE

The present invention relates to a cross-flow heat exchanger for use in a space heating system, which is adapted for heating air by means of a burner;

which heat exchanger comprises two physically separated through-flow circuits thermally coupled by a number of parallel walls, which circuits are interwoven with each other and are flowed in mutually transverse direction, respectively (1) an air flow from an outside air inlet to a discharge to the space to be heated (2) a gas flow from an inlet for, for example, hot flue gases from the burner to an outlet for flue gases to the outside, or air from the room to an outlet for it outside, all the walls being substantially congruent and interrelated by construction means, the heat exchanger having a generally substantially prismatic shape, the main direction of which parallel to the descriptive lines extends transversely of the main surfaces of the walls, wherein in the prismatic form a smaller prismatic part serving as bypass circuit with the same cross section with respect to the main direction is free from walls and comprises a space bounded by two walls, which space forms part of the first flow-through circuit, in which space is a valve which is movable by means of operating means coupled to the valve between a closed position and an open position, said valve comprising a shaft rotatable by a drive, and carrying a substantially plate-shaped element which extends substantially over the entire transverse dimension of said smaller prismatic part and extends between the side walls of the smaller one in the closed position of the valve prismatic part and in the open position of the valve a distance from at least one of said side walls.

Such a heat exchanger is known from French patent specification FR-A-2 626 969.

With such a known heat exchanger, a problem may arise in a certain period of the year, e.g. the summer period, in which the outside temperature is higher than the inside temperature. In that case, the heat recovery system will operate in reverse and the room concerned will be heated relative to the outside temperature. Under certain circumstances this may be undesirable. The present invention aims to improve the above-mentioned known heat exchanger, and in particular to improve the operation during the summer period.

This known heat exchanger is based on the principle that a cross-flow heat exchanger must be present in the space heating system, which must itself be provided with the bypass system. This offers the possibility of a very simple construction.

Therefore, the present invention provides a heat exchanger for use in a space heating system adapted to heat air by means of a burner;

which heat exchanger comprises two physically separated through-flow circuits thermally coupled by a number of parallel walls, which circuits are interwoven with each other and are transversely flowed through, respectively (1) an air flow from an outside air inlet to an outlet to the space to be heated (2) a gas flow from an inlet for, for example, hot flue gases from the burner to a exhaust for flue gases to the outside, or air from the room to an exhaust for that, all the walls being substantially congruent and interrelated by construction means, the heat exchanger having a generally substantially prismatic shape, the main direction of which parallel to the descriptive lines extends transversely of the main surfaces of the walls, wherein in the prismatic form a smaller prismatic part serving as bypass circuit with the same cross section with respect to the main direction is free from walls and comprises a space bounded by two walls, which space forms part of the first flow-through circuit, in which space is a valve which is movable by means of operating means coupled to the valve between a closed position and an open position, the valve comprising a shaft rotatable by a drive and carrying a substantially plate-shaped element which extends substantially over the entire transverse dimension of said smaller prismatic part and extends between the side walls of the smaller one in the closed position of the valve prismatic part and in the open position of the valve a distance from at least one of said side walls, characterized in that the control means for control can be connected to a sensor for the outside temperature or at least the temperature of the air flow from the outside air inlet.

One of the described exemplary embodiments is designed in such a way that the operating means, which can for instance comprise a microprocessor or the like, can be connected to an outside temperature sensor for control.

For example, the system can have the following functional situations:

WO 7298 (1) Outside air temperature below 15 ° C; bypass closed; space heating system active. The supplied outside air is heated by the extracted inside air.

(2) Outdoor air temperature below 15 ° C or above 20 ° C; bypass open; space heating system not active. The supplied outside air is fed directly to the room without heating.

(3) Outdoor air temperature less than 20 ° C;

bypass closed; space heating system active. The supplied outside air is heated by the extracted inside air.

The mentioned levels of 15 ° C and 20 ° C are mentioned by way of example. For example, the system may be designed to allow the user of the space heating system to set these temperatures.

The described regulation can lead to less heating of the house in the summer during the day (when it is warm outside) and a faster cooling of the house during the night (when it is relatively cool outside).

In particular, in a preferred embodiment the heat exchanger according to the invention has the feature that the heat exchanger has the same general shape as a known heat exchanger and is thus interchangeable therewith.

The heat exchanger can also have the special feature that the prismatic part serving as circulating circuit is a separate unit. Such a relatively small prismatic part, which serves as a circulating circuit, forms a plug-in module and can be placed in a heat exchanger, which is provided with an empty space designed for this purpose, in which the said relatively small prismatic part fits.

In this case as well as in the embodiment described in the previous paragraph, it should be noted in this case that the bypass space causes some reduction in the effective dimensions of the heat exchanger. In practice, however, it appears that heat exchangers in space heating systems are so dimensioned that this does not present a problem.

A preferred embodiment has the special feature that the center line is placed symmetrically with respect to the said side walls. This embodiment has the advantage that the air flowing past loads the plate-shaped element, which of course has to be symmetrical with respect to the center line, symmetrically. As a result, the valve can also be rotated with very little effort during the flow of air, since no obstruction is encountered by the air flowing past. In the stationary state, the drive with this structure is also not subjected to rotation.

Furthermore, the cross-flow heat exchanger preferably has the special feature that the plate-shaped element is rotatably mounted at both ends. This prevents the plate-shaped element from being subjected to bending by air flowing past, especially in the closed state.

A specific embodiment has the special feature that the drive comprises a motor with a reduction transmission. This enables a smooth displacement of the plate-shaped element to be realized, whereby the force can be sufficiently great under all circumstances due to the slow movement.

A simple embodiment has the special feature that the drive comprises two limit switches, which determine the open and closed position of the valve, respectively. This structure has the advantage that both end positions can be determined with very simple, reliable and inexpensive means.

An alternative has the special feature that the drive comprises a stepper motor. A stepper motor also makes it possible in an easy manner to make any desired intermediate position. In principle, such an intermediate position could also be achieved with an ordinary motor. In that case, however, position-recording means should be used to report the current position of the plate-shaped valve element to the operating means which respond to it, by comparing the current position with a user-set or on the basis of program control and external signals set nominal position.

The invention will now be elucidated with reference to the annexed drawing. Show in this:

figure 1 shows a partly broken away perspective view of a part of a space heating system, in which a cross-flow heat exchanger according to the invention is included;

figure 2 shows a perspective view of a known heat exchanger;

figure 3a shows a view corresponding with figure 2 of the heat exchanger according to figure 1 in the state in which the bypass valve is closed; and figure 3b shows a view corresponding with figure 3a in the situation in which the bypass valve is fully opened.

Figure 1 shows a part of a space heating device 1. A cross-flow heat exchanger 2 is incorporated therein.

Via an inlet 3, cold outside air is supplied to the heat exchanger 2 via a first inlet space 4. The heated outside air, which the heat exchanger 2 has passed through a first flow-through circuit, is discharged via a first discharge space 5 through a fan 6 to a discharge 7, through which heated air is led to the space to be heated.

The air extracted from the space is supplied via a second inlet 8 via a second inlet space 9 to a second flow-through circuit of the heat exchanger 2 and is extracted therefrom via a second discharge space 10 to an outlet 11 for discharge to the outside. In this way, an effective means is found with the device 1

007299 recovery of the heat present in the air to be vented from the room.

Before discussing the heat exchanger 2 according to the invention, reference is now first made to Figures 2, 3a and 3b.

Figure 2 shows a known heat exchanger 12. This is of the cross-flow type with two physically separated from one another by means of a number of parallel walls 13, for example of aluminum, thermally coupled flow-through circuits. These circuits are interwoven and can be flowed in transverse direction. The general direction of the two aforementioned flow circuits is indicated on the right-hand end wall by means of two arrows 14, 15. The design of this heat exchanger 12 is generally known. The walls 13 are held together by means of construction means 16.

As Figure 2 shows, the heat exchanger 2 has a substantially prismatic shape, the main direction of which is parallel to the descriptive lines, extends transversely to the main surfaces of the walls.

The heat exchanger 17 according to Figures 3a and 3b has the same general prismatic shape as the heat exchanger 12 according to Figure 2. This makes it completely interchangeable with this heat exchanger 12.

With regard to the heat exchanger 12, the heat exchanger 17 has the special feature that in the prismatic form a smaller prismatic part 18 with the same cross-section relative to the main direction is free from walls and thus comprises a space 18 bounded by two walls. This space 18 forms part of the first flow-through circuit, which is indicated by 14 for heat exchanger 12 in Figure 2. In connection therewith it is therefore bounded laterally by two walls 19, 20. The space 18 accommodates a plate 21 serving as a valve body, which is movable between a closed position according to Figure 3a and an open position according to Figure 3b. In the open position shown in Figure 3b, the valve is with

1007298?

21 '. The plate 21 is centrally mounted at its longitudinal ends in rotation bearings 31, 32, which together define a center of rotation extending symmetrically with respect to the prismatic portion 18. The plate

21 is also placed symmetrically relative to the center line in question. Thus, the plate 21 can move between the closed position in Figure 3a, in which the long side edges of the plate 21 substantially adjoin the walls 19, 20 and the open position, in which the plate 21 extends in a plane which at least extends extends more or less parallel to the walls 19, 20. The rotation of plate 21 takes place by a drive 33, which in this case is a stepper motor. The control thereof takes place by central operating means, which for instance comprise a microprocessor, which is for instance connected to a room thermostat, an outside temperature sensor and operating means, which can for instance comprise a keyboard that can be operated by a user.

The airflow through the space 18 is not passed along the surfaces of the heat exchanger 17. A direct flow of outside air outside the heat exchanger thus takes place through this bypass space 18.

A space heating system is well known and widely used. Homes furnished with such a system must also remain ventilated by the intake fan in summer. In this connection it is noted that it is not always desirable or even possible to open windows, for example in connection with street noise. Nevertheless, it is necessary to sufficiently ventilate the spaces in these houses. For this purpose the valve 21 is placed in its position 21 '. In this way, the supply of air by means of the fan 6 is also ensured in summer with a considerably reduced flow resistance. This also entails a considerable reduction in the necessary power of the fan 6.

Attention is drawn to the fact that the heat exchanger 17 according to Figures 1 and 3 preferably has the same outer shape as the known heat exchanger according to Figure 2. Thus, the heat exchanger 17 can be used to replace known heat exchanger 12.

Furthermore, attention is drawn to the fact that the invention also relates to a circulation unit, which is arranged and intended to be added to a heat exchanger, which is provided with a space for accommodating such a unit. This bypass unit according to the invention is specified in claim 10.

The present invention is not limited to the above described preferred embodiment thereof; the requested rights are defined by the following claims, within the scope of which many modifications are conceivable.