RU2760419C2 - Method for countering accumulation of icing on heat regenerator installed in air purification unit - Google Patents

Abstract

FIELD: ventilation.

SUBSTANCE: method for countering the accumulation of icing on heat regenerator (1) installed in air purification unit (2) is proposed, wherein specified heat regenerator (1) is made with the possibility of transferring energy between first air flow (3) and second air flow (4). First air flow (3) contains first exhaust air (5) in a flow direction, and second air flow (4) contains first outdoor air (7) in a flow direction. Air purification unit (2) also contains exhaust fan (9) and fan (10) for intake air and control equipment (11). The method includes measuring the temperature of exhaust air (5), the moisture content of exhaust air (5), calculating the current temperature T_5dp of a dew point of exhaust air (5), determining the validation temperature T_v for the current operating mode and the temperature T_f of icing accumulation, where T_f=F (s1, s2, … s8), i.e. T_f is a function F depending on at least one of following parameters: s1 = type of heat regenerator (1); s2 = temperature efficiency; s3 = moisture content efficiency; s4 = moisture content of exhaust air (5); s5 = temperature of exhaust air (5); s6 = temperature of outdoor air (7); s7 = air speed for intake air (8); s8 = air speed for exhaust air (5). The method includes examining T_v relatively to at least one of two criteria K₁, K₂, where K₁: T_v≤T_f, K₂: T_v≤T_5dp+Δ₁°C, where Δ ₁≥0, and, when performing at least one of criteria K₁ or K₂, decreasing the efficiency η of heat regenerator (1) and/or increasing temperature T₇ of outdoor air (7) before heat regenerator (1). The validation temperature T_v is increased so much that at least one of criteria K₁, K₂ is no longer fulfilled.

EFFECT: preventing the accumulation of icing on the regenerator.

11 cl, 3 dwg

Description

Technology area

[0001] The present invention relates to a method of using it in an air purification unit that is equipped with a heat recovery unit of some kind for recovering energy from an exhaust air stream and transferring this energy to an intake air stream. The objective is to prevent, in each operating mode, the accumulation of ice on the surface of the heat exchanger, but while maximizing the use of the heat exchanger, preferably by means of a minimum number of sensors, thus minimizing the energy losses that occur when the heat exchanger needs to be defrosted.

State of the art

[0002] A well-known problem in air purification technology is that ice build-up easily occurs on the surfaces of the heat exchanger under certain conditions, such as high moisture content in the exhaust air combined with a low outside temperature, and in many cases the outside air is practically non-existent. reaches the heat exchanger when heated. Since the accumulation of ice on the surfaces of the heat regenerator negatively affects the rate of reuse, it is desirable either to completely prevent the accumulation of ice, or to allow some freezing or accumulation of ice, followed by its defrosting by various methods and devices. Known methods typically involve multiple measurements that indicate the build-up of ice or the risk of ice build-up. For example, one method is to measure the temperature and moisture content of the exhaust air, as well as the inlet outside temperature of the heat exchanger, and enable them to be used as an indicator to determine the need to reduce heat recovery, thereby defrosting or preventing accumulated ice from accumulating. Another known, among others, method is to measure the pressure drop across the heat exchanger to detect the beginning of the accumulation of ice or frost on the heat exchanger, followed by a gradual increase in the pressure drop compared to the previous value. The latter is very common, and the most common and relatively simple method is to defrost the heat exchanger when ice or frost accumulates, and the defrosting occurs either by reducing the heat recovery, or due to the fact that the preheating battery heats the outside air reaching the heat exchanger, so that there is no possibility of freezing of condensed water. It is not energy efficient, and energy efficiency requirements are constantly increasing. Energy efficiency requirements have also recently led to an increase in the number of air purification units featuring so-called VAV regulation. VAV stands for Variable Air Volume and stands for Demand-Controlled Ventilation, i.e. for an unused room or space, the ventilation flow is reduced to a minimum and then returned to normal or forced operation when the room is in use. In general, this affects the flow and pressure drop across the AHU components. In this case, it is difficult or even impossible to measure the pressure drop and use it as an indicator of ice accumulation. In many cases, preheating battery solutions have to be used, which usually means that an electric heating battery with a relatively high power consumption and thus a high energy consumption is installed upstream of the regenerator in an external defrosting air flow. As mentioned above, high power consumption is undesirable. Another problem with the prior art is to measure the temperature at a specific location, for example, on the heat exchanger, inside or after it, to determine whether there is a risk of frost or ice accumulation in the coldest part of the heat exchanger. Ice build-up usually occurs on the surfaces of the heat exchanger, but for practical reasons the air temperature is usually measured inside or after the heat exchanger. For so-called plate heat exchangers, such as cross-flow or counter-flow, the most critical temperature takes place in the so-called "cold corner" in the art, which then represents the place where the lowest temperature is observed or expected and in which, therefore, the temperature must be measured. Another problem with a rotary heat exchanger is that the temperature is generally variable across the entire rotor cross-section. The choice of the most characteristic point for the measurement is problematic, since, firstly, it is undesirable to have many different sensors to register the most critical point in each working case, and, secondly, the "optimal" place can be different depending on the working case, which prevails at a given time. With the known technology, measurements have to be made either at many points or at a point that can be considered representative, but which, therefore, is in fact a compromise, since the location can undergo a change depending on the number of rotor revolutions per minute, the size of the rotor, air flow, temperature conditions, etc. Known methods and solutions are "generalizations" used with relatively large safety margins, and this solution often consists in defrosting, rather than preventing the accumulation of ice, and, if using the latter, then with a large tolerance, since it is difficult to make correct measurements in the right place. Therefore, there is a need for a more accurate method that works in the case of variable differential pressures across the plant and with the greatest possible recuperation to meet future energy conservation goals.

Disclosure of the essence of the invention

[0003] According to the present method, the above problems in the air purification unit are solved by the restrictive part of claim 1, in which the above problems are solved by a continuous or discontinuous method consisting in the initial measurement of the temperature and moisture content of the exhaust air in one place, preferably immediately before the heat exchanger, and then calculating the current temperature T _{dp of} the dew point of the exhaust air based on the measured values. Thereafter, for the current operating mode and on the basis of the measured and calculated values, a so-called confirmation _{temperature T v is determined either by calculation or by measurement.} For different types of heat exchangers, the confirmation temperature will be defined differently, therefore at this stage we speak of “defining” the confirmation temperature. Calculation of the confirmation temperature is most preferred, since for most different types of heat exchangers the number of sensors can be minimized, and this sensor becomes independent of where the measurement is to be made, since the measurement is unnecessary. Thus, the idea is to calculate the moment when the risk of ice accumulation occurs, and it should not start too early or too late, but rather “accompany” the current operating data for optimal recovery of as much energy as possible and for as long as possible without the accumulation of ice on the heat exchanger. and without too large safety margins. In many cases, the confirmation temperature may coincide with the "critical temperature", i.e., the temperature at which condensation occurs or the freezing point is passed, and in other cases it is selected with a certain tolerance relative to the freezing point and / or dew point for this service. case. In some applications for determining the confirmation temperature, it may be appropriate to take a measurement instead of a calculation, for example, in the case of so-called battery heat exchangers, where the measurement of the temperature of the water entering the battery for the exhaust air can be performed instead of calculation, since it is relatively simple, cost-effective. safe and characteristic measurement carried out on liquid coupled heat exchangers. As mentioned above, other heat exchangers, such as the rotor, have varying temperatures over virtually the entire surface, making it difficult to locate the sensor in a specific location. In addition to the confirmation temperature, a so-called _{ice accumulation temperature T f} is also determined, which is a value depending on one or more properties or characteristics of the application in question, and in the current operating case, for example, the type of heat regenerator, the efficiency of the temperature of the regenerator and, in if necessary, its efficiency of moisture content, moisture content and temperature of the exhaust air, the temperature of the outside air and possibly from the velocities of the intake air and exhaust air. Thus, this T _f value is a function of one or more of these characteristics and can be obtained either empirically or analytically. Thus, the temperature of ice accumulation can be constant or be subject to an equation describing a straight line or curve, or another model based on empirically determined data for all possible operating conditions, or based on algorithms. For example, for a plate heat exchanger, this value can be constant, and the battery heat exchanger can be described by an interval (line).

[0004] In order to properly perform the action to prevent the accumulation of ice, the set _{confirmation temperature T v} is checked against at least two criteria K ₁ , K ₂ :

K ₁ : T _v ≤T _f , and

K ₂ : T _v ≤T _dp + Δ ₁ ° C, where Δ ₁ ≥0.

[0005] When at least one of the two criteria is met, action is taken to influence the operating mode of the heat exchanger to prevent the accumulation of ice on the heat exchanger until at least one criterion is no longer met or is no longer met with a certain tolerance or after a certain period of time. The first criterion is related to checking whether the confirmation temperature of the so-called ice accumulation temperature is lower, and the second - to whether the confirmation temperature of the dew point (dew point) is lower. For the latter, a “safety factor” Δ ₁ can be selected, which is set to zero or more. In other words, there is a variable tolerance that must be entered into the control unit prior to performing an action in order to prevent frost / ice build-up or stop the action. Choosing 0 for the safety factor achieves a minimum energy loss, but in practice it is likely that a certain tolerance, preferably a small tolerance, will be chosen to take measures to prevent the formation and accumulation of ice. Thus, when at least one of the criteria is met, the action is activated, as a result of which the operating mode of the heat regenerator is influenced. This occurs either by reducing the efficiency of the heat exchanger and / or by increasing the temperature of the outside air flow entering the heat exchanger. In a preferred embodiment, said efficiency is the temperature efficiency of the heat exchanger, but moisture efficiency is also changed to change the temperature efficiency, and therefore the term efficiency is used to denote both types. Through this method, it is also possible to choose how precise the control should be to prevent the accumulation of ice and thus very closely follows the current operating conditions with the optimal use of heat recovery, in contrast to the known solutions, which have only approximate and general control of measures for defrosting and / or protection against ice accumulation.

[0006] In accordance with a preferred embodiment of the present invention, the heat regenerator is a liquid-coupled heat exchanger that includes at least one battery for exhaust air in a first air stream and at least one battery for intake air in a second air stream. In this case, between these batteries, a controlled (relative to the flow rate) fluid flow circulates in the fluid circuit (piping system), and this fluid flow transfers energy between the air streams for reuse. With such a heat exchanger in the air purification unit, the method according to a preferred embodiment of the present invention includes the additional steps of measuring the temperature of the liquid to be monitored entering the exhaust air stack and determining the confirmation temperature, which should be equal to the measured temperature of the liquid entering the stack. for exhaust air. Further, when at least one of the criteria K ₁ or K _{2 is} satisfied, an action is performed that affects the mode of operation of the heat exchanger by reducing its efficiency. The latter is achieved in that the control signal, which controls the fluid flow in various ways, is changed either by controlling the circulation pump to increase or decrease the flow through the battery, or by adjusting the signal in a valve included in the circulation loop, as a result of which a change in the flow through the battery occurs. The combination of a circulation pump and a control valve can also be used to control flow. By adjusting the temperature of the inlet liquid according to any action, the efficiency is changed to prevent the accumulation of ice on the exhaust air battery. In this case, in practice, it is sufficient to measure the temperature of the incoming liquid, and not to calculate it. This is due to the fact that it is sufficient to use one sensor, which is designed to measure either directly in the liquid flow or outside the tube. This measurement is reliable and the measurement point is definitely the coldest place before liquid flows into the exhaust air battery. However, this does not exclude the possibility of using the calculated value instead of the measured one to determine the confirmation temperature. The proposed method on a liquid-coupled regenerator provides more accurate control with maximum use of heat recovery without accumulation of ice in comparison with the known methods.

[0007] According to another preferred embodiment of the present invention, the heat reclaimer is a liquid-coupled heat reclaimer that includes at least one battery for exhaust air in a first air stream and at least one battery for intake air in a second air stream. At the same time, between the said batteries in the pipeline system, a flow controlled, relative to the flow rate, circulates, transmitting energy between the air flows, as described above. In addition, the air purification unit also contains a pre-heating device that is located in a different air flow in the direction of flow in front of the exhaust air battery. The method also includes the steps in which, as in the previously presented case, the temperature of the liquid entering the exhaust air bank is measured and, in addition, the confirmation temperature is determined, which should be equal to the measured temperature of the fluid entering the exhaust air bank. In addition, when at least one of the criteria K ₁ or K ₂ is satisfied, an action is taken to influence the operating mode of the heat exchanger by increasing the temperature of the exhaust air in front of the intake air stack. This is done by changing the control signal supplied to the preheater to thereby increase the power output therefrom and thereby prevent the accumulation of ice in the exhaust air battery. Thanks to the combined heat recovery control and preheating device, as well as the constant monitoring of the confirmation temperature according to the K ₁ and K ₂ criteria, optimal operation is achieved with low energy consumption, despite the prevention of ice build-up and thus there is no need for an energy-intensive defrosting sequence. an ice regenerator as in the prior art.

[0008] In another preferred embodiment of the present invention, the heat exchanger is a plate heat exchanger (either a cross-flow heat exchanger or a counter-flow heat exchanger) that is configured to exchange energy between the first and second air streams. Thus, the method includes the step of measuring the temperature T _cc in the so-called "cold corner" of the plate heat exchanger. Cold corner is a well-known term for plate heat exchangers and corresponds to the coldest place where the air meets the extract air. In addition, the method includes the step of setting the confirmation temperature to be equal to the temperature Tcc measured in the cold corner, which is believed to be a safe and cost effective way to measure the temperature, i. E. with a correctly installed temperature sensor in the "cold corner". This is because this location is by far the coldest, in contrast to the uncertainty that prevails when measuring, for example, with a rotary heat exchanger. In this case, the mode of operation of the heat exchanger is affected by a decrease in the efficiency of the plate heat exchanger by changing the control signal applied to the throttle control devices, which are usually located on the outside air side of the plate heat exchanger and in the so-called "bypass section". In this case, air is passed through the recirculation part of the heat regenerator by bypassing at least some of the outside air, and the efficiency is reduced to prevent the accumulation of ice in the heat regenerator. By means of this method, the confirmation temperature is controlled in accordance with the above criteria in order to continuously prevent the accumulation of ice, but with the simultaneous maximum possible recovery of heat, i.e., with as close to the limit of the accumulation of ice as is necessary for the existing installation, which saves energy and eliminates the need for repeatable defrosting sequences such as in the prior art in plate heat exchangers.

[0009] According to another preferred embodiment of the present invention, the heat recycler is also in this embodiment in the form of a plate heat exchanger, which is configured to exchange energy between the first and second air streams. Thus, the method includes the step of measuring the temperature T _cc in the so-called "cold corner" of the plate heat exchanger, as mentioned above. The method also includes the step of setting the confirmation temperature to be equal to the measured temperature in the cold corner, which is believed to be a safe and cost effective way to measure the temperature, that is, with the temperature sensor in the "cold corner" properly installed. The mode of operation of the heat exchanger in this case depends on the fact that the air purification unit also contains a pre-heating device, which is located in the first air flow in the direction of flow in front of the plate heat exchanger. The method then includes the step of influencing the operating mode of the heat exchanger by increasing the outside air temperature in front of the plate heat exchanger by changing the control signal supplied to the preheater to increase its power output in order to prevent the accumulation of ice in the heat exchanger. Thanks to the combined heat recovery control and preheating device and the constant monitoring of the confirmation temperature in accordance with the K ₁ and K ₂ criteria, optimum operation is achieved with low energy consumption, despite avoiding ice build-up. Thus, there is no need for the energy-intensive defrosting sequence of the ice-covered regenerator as in the prior art.

[0010] According to another preferred embodiment of the present invention, the heat exchanger in this embodiment is a plate heat exchanger capable of exchanging energy between the first and second air streams. The method includes the steps of measuring the exhaust air flow, the intake air flow, the temperature and moisture content of the exhaust air, and the temperature and moisture content in the exhaust air before the plate heat exchanger. Using these values, the dew point as well as the efficiency of the plate heat exchanger are calculated in a known manner for the current operating conditions. Then, in this embodiment, the confirmation temperature is determined by theoretically calculating the coldest point temperature based on the measured and calculated values, instead of using at least a slightly more uncertain measured value. This results in a temperature value used for control and the confirmation temperature is checked against the set ice build-up temperature and / or dew point as previously described. Finally, actions are taken to influence the operating mode of the heat exchanger, and this is also achieved in this embodiment by reducing the efficiency of the plate heat exchanger by using a modified control signal for the throttle control devices as described above. At the same time, the efficiency of preventing the accumulation of ice in the heat exchanger is reduced.

[0011] According to another embodiment of the plate type heat exchanger heat exchanger, the confirmation temperature is calculated theoretically instead of being measured as described above. However, in this case, this action is taken instead of using a preheating device, which in this embodiment is located in the first air flow in the direction of flow in front of the plate heat exchanger. The method then includes, as described above, the step of influencing the operating mode of the heat exchanger by increasing the outside air temperature in front of the plate heat exchanger by changing the control signal supplied to the preheater to increase the power output from the heater to prevent ice build-up in the heat exchanger.

[0012] In accordance with another preferred embodiment of the present invention, the heat recovery unit is a rotary heat recovery unit, and the method includes steps in a known manner to measure exhaust air flow, intake air flow, temperature and moisture content of exhaust air, and temperature and moisture content. exhaust air in front of the rotary heat exchanger. Using these values, the dew point as well as the efficiency of the heat exchanger are calculated in a known manner for the current operating conditions. Then, according to this embodiment, the confirmation temperature is determined by a calculation based on the measured and calculated values. As mentioned in the description of the prior art, the measurement should, in accordance with known technology, be performed either at many points or at a single point that can be considered representative to allow measurement at the coldest point. In fact, a compromise has to be made as this location can be different depending on rotor RPM, rotor size, air flow, temperature conditions, etc., and therefore in many cases good safety tolerances are chosen to start defrosting on time or use more power to shorten the defrosting time. To prevent the use of a large number of sensors or the need to take risks when placing one or more sensors, the approach, as mentioned, is to theoretically calculate the temperature at the coldest point for the current case and use it instead of the undefined measurement value. A safe temperature for external control is thereby obtained, the confirmation temperature then being compared with the set ice accumulation temperature and / or dew point as previously described. Finally, an action is set to influence the mode of operation of the heat exchanger, and in this embodiment this is achieved by reducing its efficiency by changing the control signal that controls the speed of the rotary heat exchanger for optimal recovery and at the same time preventing the accumulation of ice on the rotary heat exchanger. This method avoids the use of a large number of sensors or a highly uncertain placement and measurement of the characteristic confirmation temperature, which is an advantage over the known methods.

[0013] A possible alternative to the just described embodiment of the present invention is to measure the temperature of the exhaust air at a representative location instead of calculating it and enable it to be used as a confirmation temperature. Otherwise, the effect on the operating mode of the heat exchanger will be the same as indicated above and will be achieved by changing the rotor speed.

[0014] Another embodiment of the present invention is to use a preheater also as an alternative when the heat recuperator is a rotary heat recuperator. The heater is placed in the second air flow (intake air) in the direction of flow in front of the rotary heat regenerator, and the method includes the known steps of measuring the exhaust air flow, the intake air flow, the temperature and moisture content of the exhaust air and the temperature and moisture content of the exhaust air in front of the rotary heat regenerator. Using these values, the dew point and the efficiency of the heat exchanger are calculated in a known manner. Then, the confirmation temperature is determined by calculation based on the measured and calculated values as described above, and finally, an action affecting the operating mode of the heat exchanger is performed. This is achieved by changing the control signal supplied to the preheater to increase its power output and by optimizing the recuperation control while preventing ice build-up on the rotary heat exchanger.

[0015] In accordance with another embodiment of the present invention, instead of calculating the confirmation temperature, preheaters are used together with the rotor (as in the most recent embodiment) to measure the exhaust air temperature and determine it as the confirmation temperature. When checking the criteria to indicate an action is required, the control signal to the preheater should be changed as described above to increase the output of the heater. The control and coordination of the recuperation and preheating work as described above for optimal recuperation without the need to remove any ice already accumulated on the rotor.

[0016] The present invention provides a number of advantages over prior art solutions:

- preventing the formation of frost / accumulation of ice on the regenerator when using an improved method that does not consume as much energy as the known solutions;

- the need for defrosting has been eliminated, since they do not allow the accumulation of ice;

- by determining the confirmation temperature in different ways and evaluating it according to various criteria and with a given possible tolerance, the sensitivity of the defrosting operation can be better adjusted than in known methods, and this can be taken into account for optimal heat recovery;

- this method works well in installations with controlled ventilation (VAV), in contrast to the known technical solutions, in which the pressure drop in the heat exchanger is used as an indicator of the accumulation of ice;

- embodiments of the present invention, in which the confirmation temperature is calculated, provide a reliable value and eliminate the risk of taking a measurement in the wrong place in the heat exchanger, which, in contrast to the known solutions, leads to appropriate and reliable data and minimizes the number of sensors. This is especially advantageous in the case of a rotary heat exchanger since it is difficult to measure essential data by means of one or more sensors;

- the method works for several different types of heat exchangers;

- minimized the need for multiple sensors in different locations to provide reliable data.

Brief Description of Drawings

[0017] In the following drawings:

- in FIG. 1 schematically shows an air purification unit equipped with a liquid-coupled heat exchanger;

- in FIG. 2 schematically shows an air purification unit equipped with a plate heat exchanger; it can be a counter-flow heat exchanger or a so-called cross-flow heat exchanger;

- in FIG. 3 schematically shows an air purification unit equipped with a rotary heat exchanger.

[0018] A structural embodiment of the present invention is shown in the following detailed description of three embodiments of the invention with reference to the accompanying drawings, showing preferred but non-limiting examples of embodiments of the present invention.

Implementation of the invention

[0019] FIG. 1 schematically shows an air purification unit 2 with a heat recuperator 1 of the type of a liquid-coupled heat recuperator 1. The heat regenerator 1 is configured to transfer energy between the first flow 3 and the second air flow 4, the first exhaust air flow 3 containing in the flow direction the first exhaust air 5, which, when passing through the heat regenerator 1, is called the exhaust air 6. The second air flow 4 contains in the direction of flow, the first exhaust air 7, which after it passes through the heat regenerator 1 is called intake air 8. The air cleaning unit 2 also contains an exhaust air fan 9 that moves the first air stream 3 and an intake air fan 10 that moves the second air flow 4. To control and monitor the air purification unit 2 and its components, and thus to implement the method proposed in the present invention, control equipment 11 is installed. The heat regenerator 1, in turn, contains at least one battery 12 for exhaust air in the first stream 3 air and at least one battery 13 for intake air in the second air stream 4. For the transfer of energy between the batteries 12, 13, i.e. for heat recovery (or cooling), a fluid flow is circulated, which can be controlled relative to the flow rate in the fluid circuit 14 between the batteries 12, 13. The liquid is circulated using a circulation pump 15, which is preferably the embodiment can be controlled with respect to the speed to change the flow through the stacks 12, 13. The fluid circuit in the drawing is also provided with a control valve 16, which, alternatively or in conjunction with the speed control of the pump 15, can be controlled to regulate the flow through the exhaust stack 12. To measure air temperatures and moisture content in different places, several sensors are schematically shown, located (without designations) to measure the temperature T ₅ and moisture content X _{5 of the} exhaust air 5, the temperature T _{7 of the} outside air 7 and the temperature T _{8 of the} intake air 8. Thus, in according to this method, measured temperature T ₅ and the humidity of the exhaust air ₅ X 5, and wherein the calculated current temperature T _5dp dew point of the exhaust air 5. Thereafter defined so-called temperature T _v confirm that with this type of heat regenerator 1 is set equal to the measured the temperature T _{wi of the} fluid entering the exhaust air stack 12, which is schematically shown as a pipe temperature sensor.

[0020] The temperature T _{wi of the} liquid is a convenient and reliable temperature that safely measures the coldest temperature with sufficient accuracy, so it is preferable to use it for easy setup and control. In accordance with this method, the so-called _{ice accumulation temperature T F is} also determined, which depends on at least one, but preferably on several characteristics and / or conditions s1 ... s8 for the current operating case and the heat regenerator 1 in question. The ice accumulation temperature T _f is either based on empirical data obtained by testing the corresponding heat exchanger in a large number of operating cases, the current operating mode giving a critical value, i.e. the _{ice accumulation temperature T f} , alternatively this value can be determined analytically by calculating ... The data that form the basis for the function (which gives the temperature T _f of ice accumulation) is usually the following:

s1 = type of heat exchanger (1),

s2 = efficiency η _T temperature,

s3 = efficiency η _x moisture content,

s4 = moisture content x _{5 of the} exhaust air (5),

s5 = temperature T _{5 of the} exhaust air (5),

s6 = _{outdoor temperature T 7} (7)

s7 = _{air speed v 4} for intake air (8)

s8 = _{air speed v 4} for exhaust air (5).

[0021] Depending on the type of heat regenerator 1, a different amount of data from the above data is used in determining the ice accumulation _{temperature T f.} For the liquid-coupled heat regenerator 1, the data s1, s2, s4, s5 and s6 are preferably used. Other data that can have an impact are s7 and s8, which can be added as important parameters in the calculations. For certain values of temperature T _v confirmation and temperature T _F is carried out comparing the accumulation of ice temperature T _v confirm at least one of the two criteria K _1, K _2, K ₁ where: T _v ≤T _f, i.e. check the value of the confirmation temperature is equal to or lower than the temperature of ice accumulation. In addition, the second criterion K ₂ can also be checked according to K ₂ : T _v ≤T _5dp + Δ ₁ ° C, i.e. check the temperature of the confirmation of the calculated dew point is equal or lower. This criterion also contains an optional constant Δ ₁ to add to the calculation, which gives some tolerance for how close to the dew point the value should be at which Δ ₁ ≥0. When at least one of the criteria K ₁ or K _{2 is} fulfilled, according to one alternative, the _{temperature efficiency η T of} the heat exchanger is reduced by changing the fluid flow through the exhaust air stack 12, by controlling the speed of the circulation pump 15, or by controlling the valve 16, so that the temperature T _{wi of the} liquid entering the exhaust air stack 12 rises. This changes the operating mode of the heat regenerator 1, so that at least any of the criteria K ₁ , K _{2 is} no longer fulfilled. Another option is to increase the temperature T _{7 of the} outside air 7 by means of a preheating device 17, which in this case is located in the second air stream 4 (intake air), upstream of the heat regenerator 1, wherein the operating mode of the heat regenerator 1 is changed so that at least one of the criteria K ₁ , K _{2 is} no longer met, for optimal recovery and at the same time counteracting the accumulation of ice on the heat regenerator 1. Both of these variants are implemented by means of a control signal from the control equipment 11 to the circulation pump 15 and / or to the control valve 16, or, alternatively, to the preheating device 17.

[0022] FIG. 2 schematically shows an air purification unit 2 with a plate-type heat exchanger heat exchanger 1, which may be in the form of a cross-flow heat exchanger or a counter-flow heat exchanger. The plate heat exchanger 1 is equipped in accordance with known technology with several controllable throttle devices 18, which can be controlled to completely or partially close or open the heat regenerator 1 for passing the outside air 7 in combination with the opening and closing of the so-called bypass throttle, if necessary. a certain part of the outside air 7. This is the possibility of regulating the heat regenerator 1 through the control equipment 11. The air purification unit 2 is constructed in the same way as described above, with the first and second air flows 3, 4, fans 9, 10, exhaust air 5, exhaust air 6, outside air 7 and intake air 8. The difference is what is unique for the heat exchanger type 1. To measure air temperature and moisture content at different locations in the same way as shown in FIG. 1, several sensors (without designations) are located to measure the temperature T ₅ and moisture content X _{5 of the} exhaust air 5 and the temperature T _{7 of the} outside air 7 and the temperature T _{8 of the} intake air 8. In the same way as above, the temperature T _{5dp of the} current dew point The exhaust air 5 is based on the measured data of the exhaust air 5. The _{confirmation temperature T v} is then also determined here, which for this type of heat exchanger 1 is set equal to the measured temperature T _cc in the so-called "cold corner". This place is well known and can be easily identified as the coldest place in plate heat exchangers, and this is the meeting point of the cold outside air 7 with the extract air 6. The temperature T _cc in a cold corner is a convenient and reliable temperature that can be measured with sufficient accuracy. therefore, it is preferable to use it for easy installation and control. However, it is also possible to choose to use the calculated temperature, which is described in more detail in connection with the rotary heat exchanger, and a number of other measurements must also be made (see the additional description of the calculation of the confirmation temperature for the rotary heat exchanger, FIG. 3). The ice accumulation temperature is determined in the same way as described above by means of a function depending on at least one, but preferably on a number of characteristics and / or conditions s1 ... s8 for the current operating case and for the current heat regenerator 1. For plate heat regenerators 1, the characteristics s1, s2, s4, s5 and s6 are preferably used. Other influencing characteristics are s7 and s8, which can be added as important parameters in the calculations. Further, in this case, the method is continued in the same way, so that at certain values of the _{confirmation temperature T v} and the temperature T _f of ice accumulation, the _{confirmation temperature T v} is checked according to two criteria K ₁ , K ₂ and measures are taken if at least one of them is satisfied ... As described above, when using another variant of the heat regenerator 1 _{, the temperature efficiency η T} decreases, but in this case this is due to the control signal from the control equipment 11, which replaces the throttle devices 18 to reduce heat recovery. This changes the operating mode of the heat regenerator 1, so that at least one of the criteria K ₁ , K _{2 is} no longer fulfilled. In the second embodiment, the temperature T _{7 of the} outside air 7 is increased by means of a preheating device 17, which is located in the second air stream 4 (intake air) upstream of the heat regenerator 1, as a result of which the operating mode of the heat regenerator 1 is changed so that at least one of the criteria K ₁ , K _{2 are} no longer met, for optimal recuperation and at the same time counteracting the accumulation of ice on the heat regenerator 1. The power output of the preheater 17 is changed as a result of the fact that a control signal is supplied from the control equipment 11 to the heater 17.

[0023] FIG. 3 schematically shows an air purification unit 2 with a heat recuperator 1 of a rotary heat recuperator 1. The air purification unit 2 is made in the same way as described above, with the first and second air streams 3, 4, fans 9, 10, exhaust air 5, exhaust air 6, outside air 7 and intake air 8. It is also excellent here that is unique for a given type of heat regenerator 1, in this case for a rotary heat exchanger 1. To measure air temperature and moisture content at different locations, schematically similar to FIG. 1 and FIG. 2, a number of sensors (without designations) are located to measure the temperature T ₅ and moisture content X _{5 of the} exhaust air 5, the temperature T _{7 of the} outside air 7 and the temperature T _{8 of the} intake air 8. In the same way as above, the temperature T _{5dp of the} current dew point exhaust air 5 is based on measurement data for exhaust air 5. In addition to these measurement data, the control equipment 11 also collects measurement data relating to the current flow V _{4 of the} intake air, the current flow V _{3 of the} extract air and the temperature T _{7 of the} outside air 7 and moisture content X ₇ in the place in front of the rotary heat exchanger 1. In addition, the efficiency η _{1 of the} rotary heat regenerator 1 is calculated for the current operating mode. Thereafter, the _{confirmation temperature T v} is determined, which in this type of heat regenerator 1 is assumed to be equal to the design temperature based entirely on the series of measured values just listed. When performing calculations instead of measuring, a trade-off approach to the measured value from the (hopefully characteristic) sensor output can be avoided, which is still unreliable since the optimal location varies with rotor RPM, rotor size, air flow, temperature conditions, and etc., which is especially problematic, for example, in variable air volume (VAV) systems. Thus, the calculated _{confirmation temperature T v} is calculated, which is the lowest temperature, and it is this temperature that is then checked against the determined _{ice accumulation temperature T f} and / or the _{dew point T 5dp} , as previously described. For the rotary heat exchanger 1, the values s1-s6 are preferably used, and other values that can affect the use are the values s7 and s8, which can be added as significant parameters in calculations to determine the ice accumulation _{temperature T F.} Then, when at least one or both of the criteria K ₁ , K _{2 are} met for performing the action, this action is performed to influence the operating mode of the rotary heat regenerator 1. The options available for this, as before, consist in reducing the efficiency η of the heat regenerator 1 by changing the control signal that controls the speed of the rotary heat exchanger 1 for optimal recovery and at the same time preventing the accumulation of ice on the rotary heat exchanger 1. Another embodiment is to use a preheating device 17 in external air 7 to heat it in place in the second air stream 4 (intake air) in front of the rotary heat regenerator 1. In this case, the control signal will increase the output of the heater 17. An alternative to calculating the _{confirmation temperature T v} may be to measure, instead of calculating, the temperature in the extract air T ₆ , slightly away from the rotor, and assign this temperature to the confirmation _{temperature T v.} The temperature sensor for this alternative is shown as a dashed extract air sensor in FIG. 3.

List of designations

1 = heat recovery

2 = air purification unit

3 = first air flow

4 = second air stream

5 = exhaust air

6 = extract air

7 = outside air

8 = intake air

9 = exhaust fan

10 = fan for intake air

11 = control equipment

12 = battery for exhaust air

13 = battery for intake air

14 = fluid circuit

15 = circulation pump

16 = control valve

17 = pre-heater

18 = throttle devices

T = temperature

x = moisture content

F = function

K = criterion

η = efficiency

V = flow

v = speed

s = specific property

Claims (124)

1. A method of preventing the accumulation of ice on the heat regenerator (1) installed in the air purification unit (2), and the specified heat regenerator (1) is configured to transfer energy between the first air flow (3) and the second air flow (4), while the first air stream (3) contains, in the direction of flow, the first exhaust air (5) passing through the heat regenerator (1) and hereinafter referred to as the exhaust air (6), and the second air stream (4) contains, in the direction of flow, the first outside air (7) passing through the heat regenerator (1) and hereinafter referred to as intake air (8), wherein said air purification unit (2) also contains an exhaust fan (9) that controls the first air flow (3) and a fan (10) for intake air that drives the second air flow (4), and control equipment (11) is installed to control and monitor the air purification unit (2) and its components, characterized in that in order to counteract the accumulation of ice in each mode of operation of the heat regenerator (1), the method includes the following steps: a) measurement: a1. temperature T _{5 of} exhaust air (5), a2. moisture content x ₅ exhaust air (5), b) calculation: b1. the current temperature T _{5dp of} the dew point of the exhaust air (5) based on the measured values, c) definition: c1. temperature T _v confirmation for the current operating mode, c2. temperature T _f of ice accumulation, where T _f = F (s1, s2, ... s8), i.e. T _f is a function F depending on at least one of the following parameters: s1 = type of heat exchanger (1), s2 = efficiency η _T temperature, s3 = efficiency η _x moisture content, s4 = moisture content x _{5 of the} exhaust air (5), s5 = temperature T _{5 of the} exhaust air (5), s6 = temperature T ₇ outside air (7), s7 = _{air speed v 4} for intake air (8), s8 = _{air speed v 3} for exhaust air (5); d) checking T _v against at least one of the two criteria K ₁ , K ₂ , where: K ₁ : T _v ≤T _f , K ₂ : T _v ≤T _5dp + Δ ₁ ° C, where Δ ₁ ≥0, and e) when at least one of the criteria K ₁ or K _{2 is} fulfilled, a decrease in the efficiency η of the heat regenerator (1) and / or an increase in the temperature T _{7 of the} outside air (7) in front of the heat regenerator (1), and the confirmation temperature T _v is increased so that at least one of the criteria K ₁ , K _{2 is} no longer met, for optimal reuse and at the same time to prevent the accumulation of ice on the heat regenerator (1). 2. The method according to claim 1, characterized in that the heat regenerator (1) is a liquid-coupled heat regenerator, which contains at least one battery (12) for exhaust air in the first air stream (3) and at least one battery (13) for intake air in the second stream (4 ) air, while between these batteries (12, 13), the circulation of a liquid flow, controlled relative to the flow rate, is provided in the liquid circuit (14) located between the batteries (12, 13), and energy transfer is provided by the fluid flow between the air flows (3, 4), and the method also includes the step: a) measurements: a3. the temperature T _{Wi of the} liquid for the controlled flow T _{s of the} liquid entering the battery (12) for the exhaust air, in that at step c1) the _{confirmation temperature T v} is determined, equal to the measured temperature T _{Wi of the} liquid entering the exhaust air battery (12), and by the fact that in step e) they influence the operating mode of the heat regenerator (1), reducing its efficiency η by changing the fluid flow by adjusting the speed of the pump (15) or by controlling the bypass valve (16) so that the temperature T rises _Wi liquid entering the battery (12) for exhaust air. 3. The method according to claim 1, characterized in that the heat regenerator (1) is a liquid-coupled heat regenerator, which contains at least one battery (12) for exhaust air in the first air stream (3) and at least one battery (13) for intake air in the second stream (4 ) air, while between the indicated batteries (12, 13), a circulation of a liquid flow is provided, controlled with respect to the flow rate, which transfers energy between the air flows (3, 4), and the air purification unit (2) comprises a pre-heating device (17), which is located in the second air flow (4) in the direction of flow upstream of the battery (13) for intake air, wherein the method also includes the step: a) measurements: a3. temperature T _{Wi of} liquid entering the battery (12) for exhaust air, in that at step c1) the _{confirmation temperature T v} is determined, equal to the measured temperature T _{Wi of the} liquid entering the exhaust air battery (12), and in that in step e) the operating mode of the heat regenerator (1) is influenced by increasing the temperature T _{7 of the} outside air (7) in front of the intake air bank (13) by increasing the power output of the preheating device (17). 4. The method according to claim 1, characterized in that the heat regenerator (1) is a plate heat exchanger, and the method also includes the step: a) measurements: a4. temperature T _cc in the so-called "cold corner" on the plate heat exchanger (1), which is the coldest place in the plate heat exchanger (1), in which the outside air (7) meets the extract air (6), in that at step c1) it is determined that the _{confirmation temperature T v} is equal to the measured temperature T _cc in the cold corner, and the fact that in step e) they influence the operating mode of the heat regenerator (1) by reducing its efficiency η by changing the control signal supplied to the throttle devices (18), which are located on the outside air side of the plate heat exchanger (1), to reduce the throughput the ability of the air (7) through the heat exchange portion of the plate heat exchanger (1) and instead directing at least some of the outside air (7) through the bypass portion of the plate heat exchanger (1). 5. The method according to claim 1, characterized in that heat regenerator (1) is a plate heat exchanger, and the air purification unit (2) comprises a pre-heating device (17), which is located in the first air flow (3) in the direction of flow in front of the plate heat exchanger (1), and the method also includes the stage: a) measurements: a4. temperature T _cc in the so-called "cold corner" of the plate heat exchanger (1), which is the coldest place in the plate heat exchanger (1), in which the outside air (7) meets the extract air (6), in that at step c1) it is determined that the _{confirmation temperature T v} is equal to the measured temperature T _cc in the cold corner, and in that in step e) the operating mode of the heat regenerator (1) is influenced by increasing the temperature T _{7 of the} outside air (7) in front of the intake air bank (13) by increasing the power output of the preheating device (17). 6. The method according to claim 1, characterized in that heat regenerator (1) is a plate heat exchanger, and the method also includes the steps: a) measurements: a5. flow V ₄ intake air, a6. exhaust air flow V _3, a7. temperature T _{7 of the} outside air (7) in front of the heat regenerator (1), a8. moisture content X ₇ in the outside air (7) in front of the heat regenerator (1), b) calculations: b2. efficiency η of the heat regenerator (1) for the current operating mode, in that in step c1) the _{confirmation temperature T v} is determined by calculation based on the measured and calculated values, and the fact that in step e) they influence the operating mode of the heat exchanger (1), reducing its efficiency η by changing the control signal supplied to the throttle devices (18), which are located on the outside air side of the plate heat exchanger (1), to reduce the throughput the ability of the air (7) through the heat exchange portion of the plate heat exchanger (1) and instead directing at least some of the air (7) through the bypass portion of the plate heat exchanger (1). 7. The method according to claim 1, characterized in that heat regenerator (1) is a plate heat exchanger, and the air purification unit (2) comprises a pre-heating device (17), which is located in the first air flow (3) in the direction of flow in front of the plate heat exchanger (1), and the method also includes the steps: a) measurements: a5. flow V ₄ intake air, a6. exhaust air flow V ^3, a7. temperature T _{7 of the} outside air (7) in front of the heat regenerator (1), a8. moisture content X ₇ in the outside air (7) in front of the heat regenerator (1), b) calculations: b2. efficiency η of the heat regenerator (1) for the current operating mode, in that in step c1) the _{confirmation temperature T v} is determined by calculation based on the measured and calculated values, and in that in step e) they influence the operating mode of the heat regenerator (1) by increasing the temperature T _{7 of the} outside air (7) in front of the plate heat exchanger (1) by increasing the power output of the preheating device (17). 8. The method according to claim 1, characterized in that heat recuperator (1) is a rotary heat recuperator, and the method also includes the steps: a) measurements: a5. flow V ₄ intake air, a6. exhaust air flow V _3, a7. temperature T _{7 of the} outside air (7) in front of the heat regenerator (1), a8. moisture content X ₇ in the outside air (7) in front of the heat regenerator (1), b) calculations: b2. efficiency η of the heat regenerator (1) for the current operating mode, in that in step c1) the _{confirmation temperature T v} is determined by calculation based on the measured and calculated values, and by the fact that in step e) they influence the operating mode of the heat regenerator (1), reducing its efficiency η by changing the rotation speed of the rotary heat regenerator (1). 9. The method according to claim 1, characterized in that heat recuperator (1) is a rotary heat recuperator, and the method also includes the step: a) measurements: a9. exhaust air temperature Т ₆ (6), in that at step c1) the _{confirmation temperature T v} is determined, equal to the temperature T _{6 of the} exhaust air (6), and by the fact that in step e) they influence the operating mode of the heat regenerator (1), reducing its efficiency η by changing the rotation speed of the rotary heat regenerator (1). 10. The method according to claim 1, characterized in that the heat recuperator (1) is a rotary heat recuperator, and the air purification unit (2) contains a pre-heating device (17), which is located in the second air flow (3) in the direction of flow in front of the rotary heat regenerator (1), and the method also includes the steps: a) measurements: a5. flow V ₄ intake air, a6. exhaust air flow V _3, a7. temperature T _{7 of the} outside air (7) in front of the heat regenerator (1), a8. moisture content X ₇ in the outside air (7) in front of the heat regenerator (1), b) calculations: b2. efficiency η of the heat regenerator (1) for the current operating mode, in that in step c1) the _{confirmation temperature T v} is determined by calculation based on the measured and calculated values, and in that in step e) they influence the operating mode of the heat recuperator (1) by increasing the temperature T _{7 of the} outside air (7) in front of the rotary heat recuperator (1) by increasing the power output of the preheating device (17). 11. The method according to claim 1, characterized in that heat recuperator (1) is a rotary heat recuperator, and the air purification unit (2) comprises a pre-heating device (17) which is located in the second air stream (3) in the direction of flow upstream of the rotary heat exchanger (1), and the method also includes the step a) measurements: a9. exhaust air temperature Т ₆ (6), in that at step c1) the _{confirmation temperature T v} is determined, equal to the temperature T _{6 of the} exhaust air (6), and in that in step e) they influence the operating mode of the heat recuperator (1) by increasing the temperature T _{7 of the} outside air (7) in front of the rotary heat recuperator (1) by increasing the power output of the preheating device (17).

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