DE102024203836A1 - Method for controlling a decentralized ventilation system for a building - Google Patents

Abstract

The invention relates to a method for controlling a decentralized ventilation system (10) for a building (G), wherein the ventilation system (10) comprises at least two ventilation units (12, 14), each of which has a regenerator (16) for absorbing and releasing heat energy from or to the air flowing through the regenerator (16), at least one reversible fan (18) or two fans that can be operated in different directions during an operating cycle, wherein the at least one fan (18) is operated in such a way that the regenerator (16) is subjected to air flow in different directions at successive time intervals during an operating cycle in order to alternately release the heat energy stored in the regenerator (16) to the air flowing through the regenerator (16) or to absorb it from the air flowing through the regenerator (16).

Description

Technical field

The invention relates to a method for controlling a decentralized ventilation system for a building, characterized by particularly effective, i.e., highly efficient, operation of its ventilation units. The invention further relates to a ventilation system for carrying out the method according to the invention and to a computer program product.

State of the art

Decentralized ventilation systems for residential buildings using at least two ventilation units are known in the art. Typically, a first ventilation unit in a first area of the building exhausts stale indoor air to the outside, while the other ventilation unit simultaneously draws in ambient air. After a certain operating period, this process is reversed, meaning the two ventilation units operate in opposite directions. Furthermore, it is known to route the air through a regenerator in the ventilation unit during the supply and exhaust phases. This regenerator, for example, is made of ceramic material and acts as a heat storage element. If the outside air temperature is lower than the indoor temperature, the regenerator is heated by the exhausted indoor air and then releases this heat to the (fresh) ambient air when it is drawn into the building.

Furthermore, it is from the WO 2008/102227 A2 It is known to operate ventilation units of a ventilation system in a building in such a way that they supply and exhaust different quantities of air. The essential feature is that the ventilation units known from the aforementioned document are each simultaneously subjected to airflow in both directions using a heat exchanger, so that, overall, a surplus or deficit of supplied or exhausted air is achieved at each ventilation unit.

Furthermore, it is known that strong winds typically result in different wind loads on different sides of a building. If a ventilation unit is installed on each of these different sides, this usually leads to more air being drawn in during supply air operation than during exhaust air operation on the windward side of the building, as the fan of the ventilation unit then has to work against the wind pressure. Similarly, the opposite is true on the leeward side of the building, where a larger volume of air is exhausted to the outside or into the environment. Such uneven operation of the ventilation units means that the regenerator does not operate optimally, as the amounts of heat stored and released by the regenerator are unequal, thus reducing the efficiency of the ventilation unit.

Disclosure of the invention

The inventive method for controlling a decentralized ventilation system for a building, comprising the features of claim 1, has the advantage that its ventilation units are always operated in an optimal operating range, regardless of disturbances such as wind loads or similar factors, in which the thermal energy stored in the regenerator can be optimally utilized. This results in the ventilation units operated according to the inventive method exhibiting a particularly high efficiency.

The invention is based on the idea of operating one or more ventilation units in such a way that, depending on the deviation of the measured actual values of a control criterion compared to the target values, the amount of air flowing through the regenerator in the two different directions is equalized, i.e., as equal as possible, with regard to an operating cycle, i.e., during supply air operation followed by exhaust air operation. This results in the regenerator performing an equal temperature change (heating and cooling) in each case, or rather, the thermal energy stored in the regenerator being optimally utilized.

In light of the above explanations, a method according to the invention for controlling a decentralized ventilation system for a building with the features of claim 1 therefore provides that the ventilation system comprises at least two ventilation units, each of which has a regenerator for absorbing heat energy from the air flowing through it and for releasing heat energy to the air flowing through it. Furthermore, each ventilation unit has one reversible fan or two fans that can be operated in different directions, wherein the at least one fan is operated during an operating cycle such that the regenerator is subjected to alternating flow in different directions at successive time intervals in order to alternately transfer the heat energy stored in the regenerator to the air flowing through it. to discharge air flowing through the regenerator or to draw air from the air flowing through the regenerator. Means are also provided for determining a control criterion for the operation of the at least one fan of the ventilation unit, wherein, if a deviation of an actual value of the control criterion from a target value exceeds a predetermined tolerance, the at least one fan is operated in such a way that the sums of the air volumes flowing through the regenerator in the different directions during an operating cycle are at least approximately equal.

Advantageous further developments of the inventive method for controlling a decentralized ventilation system for a building are listed in the dependent claims.

Preferably, the control criterion includes the detection of a temperature, in particular an indoor temperature, within a flow cross-section of the ventilation unit. The temperature of the air flowing into or out of the ventilation unit is preferably measured on the side facing the building's interior using a temperature sensor. This has the advantage of providing better operating conditions for such a temperature sensor, as the temperature range inside the building is smaller. Furthermore, ice cannot form on the building-facing inner surface of the ventilation unit during operation, which could potentially interfere with the temperature measurement. Another advantage is that the indoor temperature can be measured directly and is subject to greater fluctuations than the outdoor temperature, which is then calculated if necessary. Measuring the temperature on the building-facing outer surface of the ventilation unit would have the disadvantage that the outer surface is easily heated by solar radiation. In the worst-case scenario, this could cause the temperature sensor to heat up while the air does not, resulting in a measurement error.

It is also mentioned that it is generally possible to use the outside temperature as a control criterion instead of the indoor temperature, or a combination of indoor and outdoor temperature.

In a preferred embodiment of the aforementioned method, the temperature at a ventilation unit is recorded during several successive operating cycles and evaluated with regard to its minimum and/or maximum values, with the (different) minimum and/or maximum values forming the control criterion. The rationale behind this proposal is that, for example, when a building is subjected to wind load, a minimum temperature is reached at the end of the supply air operation when the at least one fan is operated at the same speed and for the same duration during both supply and exhaust air operation. This minimum temperature decreases or increases over several operating cycles (depending on whether the ventilation unit is located on the windward or leeward side). The deviation of these minimum or maximum values from a mean value or a target value (without wind load) thus represents a criterion that, on the one hand, indicates a wind load on the building and, on the other hand, can be compensated for by the inventive method to increase the efficiency of the ventilation unit.

Alternatively, the temperature at a ventilation unit can be recorded during several successive operating cycles and evaluated with regard to its temperature gradients, with the gradient profiles serving as the control criterion. In other words, this means that, based solely on differing gradient profiles, even without considering minimum or maximum temperature values at the end of an operating cycle, conclusions can be drawn about, for example, the wind load on the building.

Alternatively, the efficiency of a ventilation unit can also be recorded and evaluated over several operating cycles, with efficiency serving as the control criterion. The efficiency of a ventilation unit is understood as the extent to which the maximum possible temperature difference of the regenerator material can be utilized during an operating cycle. The greater the actual temperature difference compared to the maximum possible temperature difference, the greater the efficiency of the ventilation unit, or rather, the more efficiently the thermal energy stored in the regenerator is utilized.

Regarding the manner in which to react after detecting a deviation of an actual value from a target value of the control criterion that falls outside predefined tolerances and results in a change in the operation of at least one fan, there are several possibilities: One possibility is to operate the at least one fan at different speeds depending on the direction of airflow. This results in different volume flows per unit of time being achievable in supply and exhaust air operation. where the times for supply air and exhaust air operation are the same length during an operating cycle.

Alternatively or additionally, it can also be provided that at least one fan is operated for different lengths of time depending on the direction of airflow.

Furthermore, it may be provided that, in the event of wind loads and at least one ventilation unit located on the windward side of the building and one ventilation unit located on the leeward side of the building, the ventilation units are operated differently. This includes, to a certain extent, for example, allowing different air volumes during an operating cycle at the at least two ventilation units.

Furthermore, the invention also includes a device for carrying out a method according to the invention as described so far. The device comprises at least two ventilation units, each having a regenerator for absorbing heat energy from the air flowing through the regenerator and for releasing heat energy to the air flowing through the regenerator, as well as at least one reversible fan or two fans that can each be operated in one direction, as well as measuring means for detecting an actual value of the control criterion and an evaluation and control unit for controlling the at least one fan.

It is preferred if the measuring instruments include at least one temperature sensor.

Finally, the invention also includes a computer program product, in particular a data carrier or a data program, comprising instructions that cause the device to perform at least one process step of the method according to the invention.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments of the invention and from the drawings.

Short description of the drawings

• 1 shows a schematic representation of a building with a decentralized ventilation system and two ventilation units arranged on a leeward side and a windward side of the building,
• 2 a diagram of temperature profiles measured on the inside and outside of a ventilation unit during the occurrence of a wind load,
• 3 a diagram according to the 2 at constant wind load,
• 4 a representation of a temperature profile of a sensor on the interior of a building's ventilation unit, with the possibility of using it to calculate an outside air temperature and
• 5 a flowchart to explain a method according to the invention for controlling the decentralized ventilation system according to the 1 .

Embodiments of the invention

Identical elements or elements with the same function are provided with the same reference numbers in the figures.

In the 1 In a highly simplified manner, a building G with an exterior wall AW is depicted. A decentralized ventilation system 10 is installed on the building G, which, by way of example, comprises two ventilation units 12, 14 arranged on opposite walls W1, W2 of the building G. The two ventilation units 12, 14 are designed as so-called reciprocating fans with heat recovery. Furthermore, the two ventilation units 12, 14 are preferably identical and have a regenerator 16, preferably made of ceramic material, for creating a heat storage capacity, as well as a reversible fan 18 each. The regenerator 16 and the fan 18, which, by way of example, faces the interior of the building G, are each arranged in a housing 20 of the ventilation unit 12, 14, which extends through the respective wall W1, W2. Furthermore, a temperature sensor 22, 24 is arranged in the immediate vicinity of the housing 20 or in the airflow of the fan 18, which records the air temperature T in the interior area of the building G in the flow area of the ventilation unit 12, 14.

The measured values from the two temperature sensors 22, 24 can be supplied as input to an evaluation and control unit 25 of the ventilation system 10. The evaluation and control unit 25 comprises an algorithm 26 in the form of a data program or a data carrier, which acquires and evaluates the temperature measurements recorded by the temperature sensors 22, 24. Furthermore, the two fans 18 of the ventilation units 12, 14 can be controlled by the evaluation and control unit 25.

In the 1 The case is shown where a wind load acts on building G, i.e., that in the drawing plane of the 1 A (strong) wind from the left acts on building G, as illustrated by the flow arrows 28. This results in building G being blown away on one side. Wall W1 forms a windward side, while wall W2 is a leeward side.

Without the presence of a wind load, the two ventilation units 12 and 14 are each operated independently in a reversing manner. Specifically, if the outside temperature is lower than the temperature inside the building, during the first half of an operating cycle, ventilation unit 12 draws in air from the environment or the building exterior (supply air operation). This air is heated as it passes through the regenerator 16 and flows into the interior of building G. Subsequently, during the next half of an operating cycle, ventilation unit 12 operates in reverse, meaning that the air inside building G is exhausted to the exterior of building G or the environment, releasing heat to the regenerator 16 (exhaust air operation). Crucially, the air volume flows are equal during each half of the cycle.

For example, while one ventilation unit 12 is operating in supply air mode, the other ventilation unit 14 is simultaneously operating in exhaust air mode. This means that for half a cycle time, ventilation unit 14 extracts the same volume of air from building G that simultaneously flows into building G via ventilation unit 12, and vice versa. This ensures that the volume of air extracted from building G is always equal to the volume of air flowing into building G, thus maintaining a constant air pressure within building G.

If, on the other hand, both ventilation units 12, 14 are operated in the manner described under a wind load corresponding to the 1 When operated, ventilation unit 12 exhibits a higher volume flow rate in supply air mode than in exhaust air mode, as illustrated by the differently sized arrows 31 and 32. Furthermore, ventilation unit 14 exhibits a higher volume flow rate in exhaust air mode and a lower volume flow rate in supply air mode, as illustrated by arrows 34 and 35.

In the 2 The measured temperature profiles T in °C over time t in seconds are shown as examples in four curves A to D during four consecutive operating cycles of the ventilation unit 14. Curves A and B were measured using the temperature sensor 24 ( 1 ) were measured on the inside of building G and curves C and D were measured using a device located in the 1 The temperature sensor 27 shown is located on the ventilation unit 14 in the flow cross-section on the side of the ventilation unit 14 facing the outside of the building (of course, a corresponding temperature sensor 27 can also be provided on the ventilation unit 12).

Curves A and C represent the case without any wind load, and curves B and D represent the case where the wind load begins to build up. Furthermore, the typical curve pattern is evident in all curves A to D, where, during supply air operation, the temperature T increases due to the heat energy released by the regenerator 16, and during exhaust air operation, it decreases due to the heat transfer from the air to the regenerator 16. The duration t, or half the cycle time Zz/2, is approximately 50 seconds during both supply air and exhaust air operation.

It can be seen that the minimum temperature values T_{_min} , measured by temperature sensor 24, are constant without wind load (curve A) and increase when wind load occurs (on the leeward side of building G) according to curve B, as indicated by the slope of line 36. Similarly, the maximum temperature values T_{_max}, measured by temperature sensor 27, are constant without wind load (curve C) and also increase when wind load occurs (on the leeward side of building G) (curve D), as indicated by the slope of line 37.

From the presentation of 2 It can be seen that by evaluating the maxima and minima of the temperatures T of a temperature sensor 22, 24 and 27 it is possible to detect the beginning of a wind load (as well as the increase of the wind load based on the slope of the lines 36, 37).

In contrast to 2 are in the 3 Temperature profiles at ventilation unit 14 are shown as soon as a constant wind load occurs. It can be seen that, compared to curves A and C (without wind load), curves E and F each exhibit increased (constant) minimum values T _min and maximum values T _max , which is illustrated by the straight lines 38 and 39, connecting the respective minima and maxima, respectively, which have almost no slope or are constant.

The presentation of 3 This also illustrates that when the respective ventilation unit 12, 14 is operated under wind load, the efficiency e of the respective ventilation system 12, 14 decreases compared to an optimum, since not all of the heat energy that can be stored in the respective regenerator 16 is used.

In the context of the invention, efficiency e refers to the utilization of a maximum possible temperature difference ΔT _max at the regenerator 16. The relationship to the actual temperature lift ΔT _is understood during the supply air or exhaust phase at a fan unit 12, 14: $$\text{e}=\Delta {\text{T}}_{\text{ist}}/\Delta {\text{T}}_{\text{max}}$$

For example, ΔT _max at regenerator 16 in supply air operation according to curve A is approximately 12°C, while ΔT _is approximately 5°C during wind load. Thus, the efficiency e in the case of wind load is only 5°C / 12°C = 0.41, or 41% of the efficiency e without wind load.

Furthermore, it is possible to learn from the 3 It is also evident that the graphs or curve progressions of curves A and E differ during exhaust air operation. For example, at time _t1, the tangent tan1 to curve A has a steeper slope than the tangent tan2 to curve E at time _t1 . In other words, the presence of a wind load can be inferred from the temporal progression of curves A and E (or B and F), so that the minimum values _Tmin and maximum values _Tmax of the temperature T do not need to be recorded.

In the 4 The temperature profile of a temperature sensor 22, 24 is shown during several operating cycles without wind load or after a specific time during a (constant) wind load. In particular, it can be seen that the temperature T decreases exponentially during the supply air phase according to curve H. This can be explained by the release of heat energy from the regenerator 16 into the air flowing into the building G, which is highest at the beginning of the supply air phase and decreases as the residual energy of the regenerator 16 decreases. If curve H is extended according to the dashed curve 40, the outside temperature at the building G can be determined as the limit of the curve's profile. In other words, the outside temperature can also be determined from the curve of the inside temperature.

To enable the most efficient operation of each ventilation unit 12, 14, it is necessary to utilize the thermal energy stored in each regenerator 16 as efficiently as possible, i.e., to maximize the efficiency e. This is achieved by ensuring that the volume of air supplied to building G via regenerator 16 during supply air operation is equal to the volume of air extracted from building G during exhaust air operation. This ensures that the temperature difference across regenerator 16 is at least approximately the same, meaning that the heat supplied to regenerator 16 is subsequently (almost completely) released. Furthermore, the two ventilation units 12, 14 are operated such that one unit 12, 14 is simultaneously operating in supply air mode and the other in exhaust air mode. This minimizes pressure differences within building G.

To ensure the highest possible efficiency, it is necessary to define a control criterion RK, which is evaluated by the evaluation and control unit 25 to control the fans 18 of the two ventilation units 12 and 14. Specifically, if a predefined difference between a setpoint and an actual value of the control criterion RK is exceeded, the control of the fans 18 is modified beyond normal operation. Normal operation is defined as the fan 18 of the ventilation units 12 and 14 operating for the same duration and at the same speed during both supply and exhaust air operation during a single operating cycle. This ensures that, assuming no wind load occurs in the vicinity of the ventilation units 12 and 14, the air volume is the same during both supply and exhaust air operation.

The rule criterion RK can be used according to the representation of the 2 and 3 The recording of the minimum values T _min and/or the maximum values T _max of the temperature T is used. If the aforementioned minima or maxima change during several successive operating cycles at a ventilation unit 12, 14 beyond predefined tolerances (for example, by more than 3 Kelvin during three operating cycles), it is concluded that the air volume through the regenerator 16 is different during supply air operation and exhaust air operation, as explained by the occurrence of a wind load.

Alternatively, even without knowing the exact minimum values T _min and/or the maximum values T _max of the temperature, it is possible to infer the occurrence of, for example, a wind load from the curve of a graph A to F, as is done in connection with curve E based on the 3 This has been explained. Thus, the mathematical function of a curve A to E and deviations or tolerances thereof represent the control criterion RK.

Alternatively, the efficiency e of the respective ventilation unit 12, 14 can be used as a control criterion RK, whereby if a predetermined (minimum) efficiency e is undershot, a control deviation that needs to be corrected is assumed.

To illustrate the method according to the invention, reference is now made to the flowchart as shown in the 5 referred to. Step 101 represents the recording of the rule criterion RK cha The measured variables are represented as characteristic parameters, for example, minimum values T_{_min} and/or maximum values T_{_max} of the temperature T, a temperature curve T, or the determination of the efficiency e. This is preferably carried out on ventilation units 12, 14. The measured variables are supplied to the evaluation and control unit 25 as input.

In step 102, the algorithm 26 of the evaluation and control unit 25 then takes into account or performs any necessary corrections and filters, e.g. a correction of the temperature minima due to the influence of different indoor temperatures in building G.

Subsequently, in step 103, a target/actual comparison of the control criterion RK is carried out by the evaluation and control unit 25 during, for example, several successive operating cycles.

In the subsequent step 104, it is checked whether the actual values reach a predefined tolerance value from the target values with respect to the control criterion RK. If this is not the case, no change is made to the operating mode of the fans 18 in step 105; that is, they will continue to operate at the same speed in one direction or the other for half the cycle time. If, however, an impermissible tolerance deviation is detected in step 104, an evaluation is carried out in step 106 to determine whether the tolerances have been exceeded or fallen below. Depending on the outcome, either a reduction or an increase in the speed of fan 18 during half the cycle time occurs in step 107 or step 108, or the respective half cycle time is lengthened or shortened.

In step 109, for example, no measurements are recorded or the control criterion is calculated for ten subsequent operating cycles to allow the ventilation system time for the measurements for the control criterion to normalize. Step 101 is then performed again.

The method described so far can be adapted or modified in various ways without deviating from the inventive concept. Likewise, the ventilation system 10 can have more than two ventilation units 12, 14, which are preferably operated in pairs, or such that the total amount of air supplied to building G is equal to the total amount of air extracted from building G.

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• WO 2008/102227 A2 [0003]

Claims (11)

Method for controlling a decentralized ventilation system (10) for a building (G), wherein the ventilation system (10) comprises at least two ventilation units (12, 14), each having a regenerator (16) for absorbing and releasing heat energy from/to the regenerator (16), air flowing through it, at least one reversible fan (18) or two fans that can be operated in different directions during an operating cycle, wherein the at least one fan (18) is operated such that the regenerator (16) is subjected to air flow in different directions at successive time intervals during an operating cycle in order to alternately release the heat energy stored in the regenerator (16) to the air flowing through it or to absorb it from the air flowing through it, and comprising means for determining a control criterion (RK) for the operation of the at least one fan (18) of the ventilation unit (12, 14), wherein, with a predetermined tolerance exceeding the deviation of an actual value of the control criterion (RK) from a target value, at least one fan (18) is operated in such a way that the sums of the air volumes flowing through the regenerator (16) in the different directions during an operating cycle are at least approximately equal. Procedure according to Claim 1 , characterized in that the control criterion (RK) comprises the detection of a temperature (T), in particular an indoor temperature, in the area of a flow cross-section of the ventilation unit (12, 14). Procedure according to Claim 2 , characterized in that the temperature (T) at a ventilation unit (12, 14) is recorded during several successive operating cycles and evaluated with regard to its minimum values (T _min ) and/or maximum values (T _max ). Procedure according to Claim 2 , characterized in that the temperature (T) at a ventilation unit (12, 14) is recorded during several successive operating cycles and evaluated with regard to its temporal course and the course of the temporal change of the temperature (T) forms the control criterion (RK). Procedure according to Claim 2 , characterized in that the efficiency (e) of a ventilation unit (12, 14) is recorded and evaluated during several successive operating cycles, wherein the efficiency (e) forms the control criterion (RK). Procedure according to one of the Claims 1 until 5 , characterized in that the at least one fan (18) is operated at different speeds depending on the direction of airflow through the regenerator (16) to achieve the same air volumes in supply air operation and in exhaust air operation during an operating cycle. Procedure according to one of the Claims 1 until 6 , characterized in that the at least one fan (18) is operated for different lengths of time depending on the direction of airflow through the regenerator (16) to achieve the same air volumes in supply air operation and in exhaust air operation during an operating cycle. Procedure according to one of the Claims 1 until 7 , characterized in that when wind loads occur and at least one ventilation unit (12, 14) is arranged on a windward side and one on a leeward side of the building (G), the ventilation units (12, 14) are operated differently. Ventilation system (10) for carrying out a procedure according to one of the Claims 1 until 8 , with at least two ventilation units (12, 14) each having a regenerator (16) for receiving and releasing heat energy from/to the regenerator (16), with at least one reversible fan (18) or two fans that can be operated in one direction each, with measuring means for recording an actual value of the control criterion (RK), and with an evaluation and control unit (25) for controlling the at least one fan (18). Device according to Claim 9 , characterized in that the measuring means comprise at least one temperature sensor (22, 24, 27). Computer program product, in particular data carrier or data program, comprising commands that cause the ventilation system (10) to Claim 9 or 10 at least one procedural step after one of the Claims 1 until 8 executes.