DE102014202478A1 - Method for diagnosing a heating system with at least one heat exchanger - Google Patents

Abstract

The invention relates to a method for the diagnosis of a heating system with at least one heatable heat exchanger, which is flowed through by a fluid to be heated. It is proposed that a message be issued and / or stored when a heating of the fluid by a certain or determinable temperature longer than a predetermined or predeterminable time needed and / or if the heating by the heat exchanger of a certain or determinable mass flow of the fluid below a predetermined or predeterminable temperature difference remains.

Description

The invention relates to a method for the diagnosis of a heating system with at least one heatable heat exchanger, which is flowed through by a fluid to be heated. The invention also relates to a heating system in which the method for diagnosis runs.

State of the art

Heat exchangers are used wherever a cold medium, such as water, is to be heated by heat transfer. With increasing use and aging of the heat exchanger decreases its heat transfer performance, for example due to pollution. Therefore, a heat exchanger must be cleaned at regular intervals.

It is desirable to equip a heating system which has at least one heat exchanger, so that the causes of reduced efficiency of the heat exchanger, in particular by contamination, can be detected early, so that maintenance and possibly repair of the heat exchanger allows early and full Functioning of the heat exchanger can be quickly restored.

Disclosure of the invention

This object is solved by the inventive method for diagnosis in a heating system with at least one heatable heat exchanger, which is traversed by a fluid to be heated, according to the main claim. The method is characterized in that a message is issued and / or stored when a heating of the fluid by a certain or determinable temperature longer than a predetermined or predeterminable time needed and / or if the heating by the heat exchanger of a certain or determinable mass flow of Fluids remains below a predetermined or predeterminable temperature difference.

Here, a fluid is defined as a flowable substance which can absorb, store and release heat, such as a gas or a liquid. In principle, solid substances are also conceivable which can store and release heat. When the term fluid is used here, it is meant in general heat transfer media that can be used in a heating system.

A heat exchanger is understood to mean a device for transferring heat to a fluid. The term heat exchanger is also used synonymously.

The time for heating the fluid by a certain or determinable temperature is also abbreviated as the warm-up time.

The features listed in the dependent claims advantageous refinements of the method for diagnosing a heating system according to the main claim are possible.

In one step of the method, one or more parameters are determined and / or stored, such as the time for heating the fluid by a certain or determinable temperature, that is, the warm-up time, and / or a heat transfer coefficient of the heat exchanger and / or a temperature difference between a flow and return temperature of the heat exchanger, which has the advantage that this information can be used for diagnostic and / or prognostic purposes, for example, with respect to the state of the heat exchanger. It is advantageous if a message, in particular about a reduced functionality of the heat exchanger, in particular due to contamination, issued and / or stored as soon as the number of cases in which the parameter or reaches a certain or determinable threshold, a certain or determinable value. Such a hysteresis has the further advantage that a message is not issued immediately at the first occurrence of such a case, but that the accumulation of occurring cases can be regarded as a reliable indication.

In order to obtain an even more reliable statement about the power state of the heat exchanger, it is advantageous if, in addition to the temperature difference between flow temperature and return temperature of the heat exchanger, a power of a pump in a first Teilheizkreis can be used as an indicator. If, for example, a higher power of the pump is required in the course of time, with a constant or even decreasing temperature difference, this indicates a reduced functionality.

To determine the temperature difference, it is advantageous if in a method step, the flow temperature, in particular via a first sensor in the flow of the first Teilheizkreises, and the return temperature, in particular via a second sensor in the return of the first Teilheizkreises can be determined.

In one step of the method, at least one threshold value for the parameter (s) is predetermined and / or calculated, as far as they are concerned not yet determined. Also, at least one value each is given as an upper bound for the number of cases in which the parameter (s) reach the associated threshold, if it has not yet been determined. This has the advantage that settings for the diagnosis of the heating system can be made flexibly and according to the needs and / or can be determined precisely by means of calculations. At the same time, the comfort for the user is increased, which makes it possible to enter values themselves or to use provided values.

For further diagnosis and for prognosis purposes, it is advantageous if the parameter (s), the respectively associated threshold value and / or the respectively associated value for the number of cases in which the respective threshold value is reached are recorded and / or output and / or can be read out.

In a further step of the method, a counter is initiated as soon as the threshold is reached for the first time, and the counter is incremented as the parameter (s) reach the respective threshold once more. Depending on the choice of parameter (s), the counter is also initiated or incremented if the threshold is undershot or exceeded. This is advantageous because such a counter can serve as a starting point for the diagnosis of the heating system. Another advantage lies in the prognosis of a possible malfunction of the heating system or the need for maintenance, so that it is possible to respond quickly to errors.

It is advantageous if the counter can be recorded and / or output and / or read out.

berechnet, wobei c die Wärmekapazität des Fluids, ΔT_Schwelle die Temperaturdifferenz, beispielsweise zwischen dem Wärmetauscher und dem Fluid oder die Temperaturdifferenz von Vorlauftemperatur zu Rücklauftemperatur, ṁ der Massenstrom des Fluids, A die freie Wärmeübertragungsfläche und

die zu ΔT_Schwelle gehörende, gemittelte logarithmische Temperaturdifferenz ist, welche berechnet wird aus den Eintrittstemperaturen in den Wärmetauscher und den Austrittstemperaturen aus dem Wärmetauscher.The threshold value for the heat transfer coefficient can be calculated, which has the advantage that an accurate, theoretical value can be used as the reference value. In this case, in one step of the method, the threshold k _threshold according to the formula

calculated, where c is the heat capacity of the fluid, ΔT _threshold the temperature difference, for example between the heat exchanger and the fluid or the temperature difference of flow temperature to return temperature, ṁ the mass flow of the fluid, A the free heat transfer surface and

is the averaged logarithmic temperature difference associated with the ΔT _threshold , which is calculated from inlet temperatures into the heat exchanger and exit temperatures from the heat exchanger.

The invention also relates to a heating system with at least one heatable heat exchanger through which a fluid to be heated flows, in which the above-described method for diagnosis runs. In this case, a message is issued and / or stored when a heating of the fluid by a certain or determinable temperature longer than a predetermined or predeterminable time needed and / or if the heating by the heat exchanger of a certain or determinable mass flow of the fluid below a predetermined or predeterminable Temperature difference remains.

drawing

In the figures, a schematic representation of a heating system according to the invention is to be seen, as well as a method according to the invention for fault diagnosis, which will be explained in more detail in the following description. Show it

1 an embodiment of a heating system according to the invention,

2 the basic steps of the procedure for diagnosis in the heating system.

Description of the drawings

The embodiment in 1 shows a heating system 10 with a heat generator 12 , which with a heat exchanger 14 is provided. In a first partial heating circuit 16 is a fluid, such as hot water, through the heat exchanger 14 heated, and a second Teilheizkreis 18 is used to heat cold service water using a heat exchanger 20 , for example in the continuous flow principle. The first partial heating circuit 16 has a pump 22 and a three-way valve 24 and a three-way valve 25 on to ensure the circulation of the fluid. In this case, at least one heat consumer 25 supplied with warm heating water. In the flow of the heat generator 12 there is a sensor 26 , in particular a temperature sensor, for measuring the flow temperature. There is also a sensor in the return 28 for measuring the return temperature.

In the second partial heating circuit 18 is cold service water to the heat exchanger 20 transported where it is heated, then the hot water is passed to the end user. A sensor 30 Measures the temperature of the cold water before entering through the heat exchanger 20 , a sensor 32 Measures the temperature of the heated cold water after leaving.

At the heat generator 12 they can be a variety of heaters powered by fossil or renewable resources. In the embodiment, there are a gas burner 33 and the heat exchanger 14 in the heat generator 12 , This is the heat generator 12 with the help of a blower 34 over a line 36 fed to a gas-air mixture. In this line 36 there is still a valve 38 , Exhaust gas products are via an exhaust pipe 40 led to the outside. By one of the gas burner 33 Flame generated is the fluid passing through the heat exchanger 14 circulated, heated.

In the embodiment in 1 indicates the heating system 10 continue an ad 42 and a control and / or regulating unit 44 on, these being outside the heat generator 12 located. The ad 42 is at the heat generator 12 appropriate. The heat generator 12 , the control and / or regulating unit 44 and the ad 42 are connected and can communicate with each other. Often the heat generator 12 via the control and / or regulating unit 44 still with the heat consumer 25 and connected to other control or regulating elements, such as the pump 22 , the valves 23 . 24 , the blower 34 , the valve 38 and / or with a room thermostat to ensure an even more optimized and flawless operation. Conceivable in this case is a wired or a wireless connection, as well as a mixture of these types of connections.

Alternatively, the control and / or regulating unit 44 also within the heat generator 12 are located. Other embodiments are also conceivable. The same applies to the ad 42 to.

For the diagnosis of the heating system 10 a procedure takes place, which is based on the 2 is described.

The time to heat the fluid through the heat exchanger 14 . 20 , called warm-up time, its heat transfer coefficient and the temperature difference between the flow and return temperature of the heat exchanger 14 . 20 are system-inherent parameters and are used according to the invention as indicators for a reduced functionality of the heat exchanger 14 . 20 , especially due to pollution used. Thus, the heat transfer coefficient decreases with increasing resistance of the heat exchanger 14 . 20 which, for example, is exactly the case when the surface of the heat exchanger 14 . 20 is increasingly polluted. In this case, the efficiency of the heat exchanger also decreases 14 . 20 , which leads to a higher warm-up time, on the other hand, if one specifies a fixed duration, to a lower temperature difference after this time.

While the heat transfer coefficient and the temperature difference during the operation of the gas burner 33 determined, the determination of the warm-up time depends on the burner start. The time measurement starts at burner start and ends as soon as a setpoint temperature for the fluid, for example for the service water or heating water, has been reached.

The core of the method is the output of a message when a heating of the fluid by a certain or determinable temperature longer than a predetermined or predeterminable time needed or when the heating by the heat exchanger 14 . 20 a certain or determinable mass flow of the fluid remains below a predetermined or predeterminable temperature difference. Both cases can occur. The message is saved for later purposes, such as for a prognosis or diagnosis, so that it is retrievable at any time.

The method is applicable in principle to any heat exchanger. The following is the heat exchanger 14 explained.

At the beginning of the procedure, in step 50 , the user enters the parameter (s) to be used for the diagnosis. He can select a diagnosis based on the warm-up time, the heat transfer coefficient or the temperature difference between flow and return temperature. It is also possible to select several modes at the same time, which are then executed in parallel or serially. In the following, the case is considered that all modes are selected and executed in parallel.

In step 52 are the flow temperature over the sensor 26 and the return temperature over the sensor 28 measured. Further, a target value for a temperature of the fluid, such as a target value for the temperature of the heating water and the service water, set.

In the steps 53 . 54 and 55 The values required for the procedure are specified or calculated if they are not yet available. The values can be specified for the same systems. For example, they can be set as defaults that are used automatically or chosen by the user. They can also be entered by the user. For new or maintained systems, the values can be reset or recalculated.

For the warm-up time is in step 53 a threshold 56 specified or calculated. Next can be a value or a maximum number 58 to be determined, which is an upper bound for the number of cases where the warm-up time is the threshold 56 reached or exceeds. Is the maximum number 58 for example 20 , so goes out a message when the 21 , Case of increased warm-up time occurs. The threshold 56 is present in the system as a default value or can be changed or specified by the user.

berechnet. Hierbei ist ΔT_Schwelle eine feste, vorgegebene Temperaturdifferenz zwischen einem idealen, beispielsweise unverschmutzten, Wärmetauscher, welcher von der vom Gasbrenner 33 erzeugten heißen Luft erwärmt wird, und dem Heizwasser, an welches die Wärme abgegeben wird, die freie Wärmeübertragungsfläche, ṁ der Massen- bzw. Volumenstrom und c die Wärmekapazität des Fluids. Die Temperatur und der Massenstrom können über entsprechende Sensoren gemessen werden. Die Wärmekapazität des Fluids kann Tabellen entnommen werden. Weiter ist

die zu ΔT_Schwelle gehörende, feste gemittelte logarithmische Temperaturdifferenz, welche bestimmt wird aus den fest vorgegebenen Temperaturen der anwesenden Eintritte und Austritte des idealen Wärmetauschers. Durch den Wärmetauscher 14 strömt das heiße Abgas des Gasbrenners 33, das sich abkühlt und seine Wärmeenergie auf das Heizwasser überträgt. For the heat transfer coefficient as an indicator of reduced efficiency of the heat exchanger 14 will be in step 54 a threshold 60 k _threshold specified or calculated. For the calculation, ideal heat transfer conditions of the heat exchanger 14 provided. The threshold 60 is about the expression

calculated. Here, ΔT _{threshold is} a fixed, predetermined temperature difference between an ideal, for example, unpolluted, heat exchanger, which of the gas burner 33 heated hot air is generated, and the heating water to which the heat is released, the free heat transfer surface, ṁ the mass or volume flow and c the heat capacity of the fluid. The temperature and the mass flow can be measured via corresponding sensors. The heat capacity of the fluid can be found in tables. Next is

the fixed averaged logarithmic temperature difference associated with the ΔT _threshold which is determined from the fixed preset temperatures of the inlet and outlet of the ideal heat exchanger. Through the heat exchanger 14 the hot exhaust of the gas burner flows 33 , which cools and transfers its heat energy to the heating water.

To step 54 also includes the specification of a maximum number 62 for the heat transfer coefficient, from which a message on the reduced efficiency of the heat exchanger 14 should be issued. The maximum number 62 gives an upper bound for the number of cases where the heat transfer coefficient is the threshold 60 below.

Is the temperature difference between flow and return of the heat exchanger 14 used as an indicator, then in step 55 a threshold 64 and a maximum number 66 specified or calculated for the temperature difference, analogous to the steps 53 and 54 , The maximum number 66 is an upper bound for the number of cases where the temperature difference is the threshold 64 below. Were the flow and return temperatures not yet measured, for example because step 52 was skipped, this will be in step 55 made up.

Should the power of the pump 22 together with the temperature difference as an indicator of reduced efficiency of the heat exchanger 14 be consulted, so in step 55 a threshold 65 for the performance of the pump 22 additionally specified. Alternatively it can be calculated. The maximum number 66 is then an upper bound for the number of cases where the temperature difference is the threshold 64 reaches or falls below and the performance of the pump 22 the threshold 67 reached or exceeded.

All values are stored and can be recalled or changed by the user.

In step 68 become a counter 70 for the warm-up time, a counter 72 for the heat transfer coefficient and a counter 74 initiated for the temperature difference. For example, they are set to 0.

Once the heat generator 12 starts, starts in step 76 a time measurement for determining the warm-up time of the fluid through the heat exchanger 14 , If the heating water reaches the specified setpoint temperature, the time measurement is ended. The elapsed time is saved as the warm-up time.

zugrunde gelegt. Hier ist nun ΔT die (variable) Temperaturdifferenz zwischen dem Wärmetauscher 14 und dem Heizwasser und ΔT die (variable) mittlere logarithmische Temperaturdifferenz zwischen Wärmetauscher 14 und Heizwasser, gegeben durch

In step 77 the heat transfer coefficient is calculated. For this the formula becomes

based on. Here ΔT is the (variable) temperature difference between the heat exchanger 14 and the heating water and .DELTA.T the (variable) average logarithmic temperature difference between heat exchangers 14 and heating water, given by

ΔT ₂ ≥ ΔT _{1 was} assumed for the mean logarithmic temperature difference to be positive. ΔT ₂ and ΔT ₁ are defined as follows: At the first inlet of the heat exchanger 14 the temperature T _{inlet1 of} the hot air is measured or the temperature of the heat exchanger 14 , At the first exit there is the temperature T _{outlet 1 of} the cooled air in the exhaust pipe. At the second inlet, the entry of the return heating water into the heat exchanger 14 , was in step 52 over the sensor 28 the return temperature T _inlet 2 measured, and at the second exit from the heat exchanger the Flow temperature T _{outlet 2} through the sensor 26 , Now Calculate the difference .DELTA.T ₁ ≔ | T _entry1 - T _Austritt2 | and ΔT ₂ ≔ | T _{outlet 1} - T _{inlet 2} |, if ΔT ₁ ≥ ΔT ₂ . Otherwise, AT is ₂ ≔ | T _entry1 - T _Austritt2 | and .DELTA.T ₁ ≔ | T _Austritt1 - T _Eintritt2 |.

In step 78 the calculation of the temperature difference between the flow and return temperatures is performed. Were the flow and return temperatures not yet measured, for example because step 52 was skipped, the measurement is performed before the calculation of the temperature difference.

In step 80 If the query takes place as to whether the respective parameters reach their associated threshold value: A query is made as to whether the warm-up time is greater than the threshold value 56 is whether the heat transfer coefficient is smaller than the threshold 60 is and if the temperature difference is less than the threshold 64 is.

If not (step 82 ), so the counters remain 70 . 72 . 74 unchanged. The procedure is in the steps 76 . 77 and or 78 depending on whether the warm-up time, the heat transfer coefficient and / or the temperature difference have been selected (step 50 ).

Returns the query in step 80 Yes, so the warm-up time is greater than the threshold 56 or the heat transfer coefficient is less than the threshold 60 or the temperature difference is less than the threshold 64 so are the counters 70 . 72 . 74 in step 84 increased, for example, by 1.

Of course, hybrids are conceivable, for example, the warm-up time is greater than the threshold 56 and the heat transfer coefficient is smaller than the threshold value 60 , Then the counter 70 and the counter 72 elevated. Or the temperature difference is less than the threshold 64 and the warm-up time is greater than the threshold 56 , Then the counter 74 and the counter 72 Increased, etc. Which and how many meters have been increased, can also be an indication of reduced functionality of the heat exchanger 14 give. Therefore, the current state of the counter 70 . 72 . 76 stored and is readable at any time.

In step 86 is queried, if at least one of the counters 70 . 72 . 76 the associated maximum number 64 . 66 . 68 has reached or exceeded.

If this is not the case, the procedure starts again at step 76 , Step 77 and step 78 if all three modes were selected in parallel, as assumed in this embodiment. The heat generator 14 continues to run and it is checked again whether a reduced function or malfunction exists.

If not all modes have been selected, for example only one, then the process goes to step 82 in step 76 , Step 77 or step 78 continued, depending on which mode was selected. Accordingly, mixed forms are possible. Also a serial processing of the steps 76 . 77 . 78 is possible, which is not shown.

The method may be intermittently interrupted or prematurely terminated to resume in a step of choice, for example in one of the steps 50 . 52 . 53 . 54 . 55 etc.

For example, if the procedure is in step 80 , or another step, the user pauses and selects step 50 , this corresponds to a kind of restart. Already measured or calculated parameters, such as the warm-up time, or messages have been saved and can be read out. You can enter new values that will be used as the basis for the diagnosis, or you will use preset default values or previously entered values.

For example, from step 84 , or another step, in step 68 jumped, this corresponds to a kind of reset. In step 68 become the counters 70 . 72 . 74 initiated, for example, set to 0. For example, was at least one of the counters 70 . 72 . 74 greater than this initial value, it will be reset to this initial value. Thus, the procedure begins again with the count of injury cases, but uses the values and measurements already entered.

The method may also be programmed to automatically switch to another selectable step after a selected step. It can also be turned off completely.

Results in step 86 the query that at least one of the maximum numbers 58 . 62 . 66 has been reached or exceeded, so in step 88 a corresponding message about it is issued and saved. The date and time of the message are saved with. For example, the message may include text stating that the functioning of the heat exchanger 14 is reduced, in particular due to pollution. The text can also state that the heat exchanger 14 requires maintenance or cleaning or the like. The message may additionally or solely consist of a flashing of a light source, such as a light-emitting diode, or of a sound, such as a one-time or multiple beep. Other types of messages are also conceivable. The message can persist until the user actively terminates it. Also conceivable is a one-time issue that does not have to be actively terminated. The message will be recorded for retrieval at a later time.

So in step 88 For example, a beep sounds for a few seconds, parallel to this, a red light is lit or flashing until the user confirms that he has taken note of the message, for example, by pressing a button or a spoken command.

The heat generator 12 continues to operate normally after the message has been sent, even if no maintenance or cleaning or the like has been carried out, and even if the message persists.

In step 90 it is queried whether maintenance or cleaning or the like has been carried out.

If this is not the case, then the procedure goes on in step 76 , Step 77 and step 78 continue if all three modes have been selected. The message continues to be output. For example, the flashing of a light-emitting diode continues.

After maintenance or cleaning, that is, the query in step 90 was affirmed, in step 92 the parameter values, such as the warm-up time, the heat transfer coefficient, the temperature difference, the flow and return temperatures, the counters 70 . 72 . 74 , reset. The procedure starts again at step 50 , and the diagnosis of the heat generator 14 starts again.

All values, whether entered, calculated or determined in the course of the procedure, are stored and recorded. The time of their creation is also stored. For example, how quickly in succession do the warm-up time, the heat transfer coefficient, or the temperature difference find their respective thresholds 56 . 60 . 64 did not comply with when the corresponding counters 70 . 72 . 74 were increased and when the maximum number 58 . 62 . 66 was achieved. Next is the time and type of message in step 88 saved. After maintenance, the memory can be reset to avoid a memory overflow. The time of maintenance is retained. The memory can also be reset manually. The user has access to all data for diagnostic and forecast purposes.

Claims (10)

Method for diagnosing a heating system ( 10 ) with at least one heatable heat exchanger ( 14 . 20 ), which is flowed through by a fluid to be heated, characterized in that a message is issued and / or stored when a heating of the fluid by a certain or determinable temperature longer than a predetermined or predeterminable time needed and / or if the heating by the heat exchanger ( 14 . 20 ) of a certain or determinable mass flow of the fluid remains below a predetermined or predeterminable temperature difference. A method according to claim 1, characterized in that one or more parameters, such as the time for heating the fluid by a certain or determinable temperature and / or a heat transfer coefficient of the heat exchanger ( 14 . 20 ) and / or a temperature difference between a flow and return temperature of the heat exchanger ( 14 . 20 ), determined and / or stored, and that a message, in particular on a reduced functionality of the heat exchanger ( 14 . 20 ) is emitted and / or stored, in particular as a result of pollution, as soon as the number of cases in which the parameter (s) reaches a certain or determinable threshold value reaches a certain or determinable value ( 58 . 62 . 66 ) exceeds. Method according to one of claims 1 to 2, characterized in that the temperature difference between flow temperature and return temperature of the heat exchanger ( 14 . 20 ) and a power of a pump ( 22 ) as an indicator of reduced efficiency of the heat exchanger ( 14 . 20 ), in particular due to contamination. Method according to one of claims 1 to 3, characterized in that a flow temperature, in particular via a first sensor ( 57 ) in the flow of a first Teilheizkreises ( 54 ), and a return temperature, in particular via a second sensor ( 58 ) in the return of the first Teilheizkreises ( 54 ). Method according to one of claims 1 to 4, characterized in that at least one threshold ( 56 . 60 . 64 ) for the parameter or parameters and that at least one value each ( 58 . 62 . 66 ) for the number of cases in which the parameter or parameters exceed the threshold ( 56 . 60 . 64 ), predefined and / or calculated, if they have not yet been determined. Method according to one of the preceding claims, characterized in that the parameter or parameters, the respectively associated threshold ( 56 . 60 . 64 ) and / or its associated value ( 58 . 62 . 66 ) and / or output and / or read out. Method according to one of claims 1 to 6, characterized in that a counter is initiated as soon as the threshold ( 56 . 60 . 64 ) is reached for the first time and that the counter is incremented when the threshold ( 56 . 60 . 64 ) is reached again. Method according to one of the preceding claims, characterized in that the counter is recorded and / or output and / or readable. Method according to one of claims 5 to 8, characterized in that the threshold value ( 58 ) for the heat transfer coefficient, k _threshold , according to the formula

where c is the heat capacity of the fluid, ΔT _{threshold is} the temperature difference, for example between the heat exchanger ( 14 . 20 ) and the fluid or the temperature difference of flow temperature to return temperature, ṁ the mass flow of the fluid, A the free heat transfer surface and

is the averaged logarithmic temperature difference associated with ΔT _threshold , which is calculated from the inlet temperatures into the heat exchanger ( 14 . 20 ) and the outlet temperatures from the heat exchanger ( 14 . 20 ). Heating system with at least one heatable heat exchanger ( 14 . 20 ), which is traversed by a fluid to be heated and in which a method for the diagnosis runs in particular according to one of the preceding claims, characterized in that a message is issued and / or stored when a heating of the fluid by a certain or determinable temperature longer required as a predetermined or predeterminable time and / or when the heating by the heat exchanger ( 14 . 20 ) of a certain or determinable mass flow of the fluid remains below a predetermined or predeterminable temperature difference.

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