Method for operating and/or monitoring an HVAC system

Abstract

A method for operating and/or monitoring an HVAC system (10), in which a medium circulating in a primary circuit (26) flows through at least one energy consumer (11, 12, 13), the medium entering with a volume flow () through a supply line (14) into the energy consumer (11, 12, 13) at a supply temperature (T.sub.v) and leaving the energy consumer (11, 12, 13) at a return temperature (T.sub.R) via a return line (15), and transferring heat or cooling energy to the energy consumer (11, 12, 13) in an energy flow (E). A control unit (21) adaptively operates the system by empirically determining the dependence of the energy flow (F) and/or the temperature difference T between supply temperature (T.sub.v) and return temperature (T.sub.R) on the volume flow () for the energy consumers (11, 12, 13) in a first step, and by operating and/or monitoring the HVAC system (10) according to the determined dependency or dependencies in a second step.

Claims

1. A method for adaptively operating and/or monitoring a Heating, Ventilation and Air Conditioning (HVAC) system (10) under control of a controller (21, 22), the method comprising: circulating a medium in a primary circuit (26), such that the medium flows through at least one energy consumer (11, 12, 13), the medium entering at a volumetric rate of flow () into an energy consumer (11, 12, 13) through a supply line (14) at a supply temperature (T.sub.V) and leaving the energy consumer (11, 12, 13) at a return temperature (T.sub.R) by way of a return line (15) and, in so doing, releases heat energy or cold energy to the energy consumer (11, 12, 13) in a flow of energy (E), empirically determining a dependence of the flow of energy (E) and/or a temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) on the volumetric flow rate () for the respective energy consumer (11, 12, 13), adaptively changing operation of the HVAC system (10) in accordance with the determined dependence and/or dependences, wherein the dependence of the flow of energy (E) on the volumetric flow rate () is repeatedly determined empirically at varying time intervals by the controller, whereby the volumetric flow rate () and the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) are measured simultaneously at different points in time and, if desired, the associated flow of energy (E) is determined for each of the points in time from associated measurement values and assigned to a respective volumetric rate of flow () in order to determine empirically the dependence of the flow of energy (E) on the volumetric flow rate (), while the system is running, over a sufficiently long period of time, and wherein, on the basis of the determined dependence, an upper limit value (E.sub.max) of the flow of energy (E) is established, and said upper limit value is not exceeded while the HVAC system (10) is running.

2. The method, as claimed in claim 1, wherein the dependence of the flow of energy (E) on the volumetric flow rate () is determined empirically at a start of the operation in a newly installed HVAC system (10), and the HVAC system (10) or more specifically the individual components are changed or replaced, when the empirically determined dependences make it necessary.

3. The method, as claimed in claim 1, wherein temperature sensors (16, 17) for determining the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) as well as the at least one flow sensor (18) for determining the volumetric flow rate () are provided in the HVAC system (10) for carrying out the operation, and wherein the temperature and flow sensors (16, 17 and/or 18) are used for empirically determining the dependence of the flow of energy (E) on the volumetric flow rate ().

4. A method for adaptively operating and/or monitoring a Heating, Ventilation and Air Conditioning (HVAC) system (10) under control of a controller (21, 22), the method comprising: circulating a medium in a primary circuit (26), such that the medium flows through at least one energy consumer (11, 12, 13), the medium entering at a volumetric rate of flow () into an energy consumer (11, 12, 13) through a supply line (14) at a supply temperature (T.sub.V) and leaving the energy consumer (11, 12, 13) at a return temperature (T.sub.R) by way of a return line (15) and, in so doing, releases heat energy or cold energy to the energy consumer (11, 12, 13) in a flow of energy (E), empirically determining a dependence of a temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) on the volumetric flow rate () for the respective energy consumer (11, 12, 13), adaptively changing operation of the HVAC system (10) in accordance with the determined dependence and/or dependences, wherein the dependence of the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) on the volumetric flow rate () is repeatedly determined empirically at varying time intervals by the controller, whereby the volumetric flow rate () and the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) are measured simultaneously at different points in time and, if desired, the associated flow of energy (E) is determined for each of the points in time from associated measurement values and assigned to a respective volumetric rate of flow () in order to determine empirically the dependence of the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) on the volumetric flow rate (), while the system is running, over a sufficiently long period to time, wherein, on the basis of the determined dependence, a lower limit value (T.sub.min) of the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) is established.

5. The method, as claimed in claim 4, wherein the dependence of the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) on the volumetric flow rate () is determined empirically at a start of the operation in a newly installed HVAC system (10), and the HVAC system (10) or more specifically the individual components are changed or replaced, when the empirically determined dependences make it necessary.

6. The method, as claimed in claim 4, wherein temperature sensors (16, 17) for determining the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) as well as at least one flow sensor (18) for determining the volumetric flow rate () are provided in the HVAC system (10) for carrying out the operation, and wherein the temperature and flow sensors (16, 17 and/or 18) are used for empirically determining the dependence of the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) on the volumetric flow rate ().

7. A method for adaptively operating and/or monitoring a Heating, Ventilation and Air Conditioning (HVAC) system (10) under control of a controller (21, 22), the method comprising: circulating a medium in a primary circuit (26), such that the medium flows through at least one energy consumer (11, 12, 13), the medium entering at a volumetric rate of flow () into an energy consumer (11, 12, 13) through a supply line (14) at a supply temperature (T.sub.v) and leaving the energy consumer (11, 12, 13) at a return temperature (T.sub.R) by way of a return line (15) and, in so doing, releases heat energy or cold energy to the energy consumer (11, 12, 13) in a flow of energy (E), empirically determining a dependence of the flow of energy (E) and/or a temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) on the volumetric flow rate () for the respective energy consumer (11, 12, 13), adaptively changing operation of the HVAC system (10) in accordance with the determined dependence and/or dependences, wherein the dependence of the flow of energy (E) and/or the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) on the volumetric flow rate () is repeatedly determined empirically at varying time intervals by the controller, whereby the volumetric flow rate () and the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) are measured simultaneously at different points in time and, if desired, the associated flow of energy (E) is determined for each of these points in time from associated measurement values and assigned to a respective volumetric rate of flow () in order to determine empirically the dependence of the flow of energy (E) and/or temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) on the volumetric flow rate (), while the system is running, over a sufficiently long period to time, wherein results that are obtained in each case are compared with each other by the controller, in order to determine by the comparison a degradation of the system in function or effect, and wherein the measurement values are scaled, in particular, by means of a mathematical model of the energy consumer (11, 12, 13) for purposes of comparison, or wherein other comparable measurements are used for comparison, when specified operating parameters have changed significantly in the meantime.

8. The method, as claimed in claim 7, wherein the dependence of the flow of energy (E) and/or the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) on the volumetric flow rate () is determined empirically at a start of the operation in a newly installed HVAC system (10), and the HVAC system (10) or more specifically the individual components are changed or replaced, when the empirically determined dependences make it necessary.

9. The method, as claimed in claim 7, wherein temperature sensors (16, 17) for determining the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) as well as at least one flow sensor (18) for determining the volumetric flow rate () are provided in the HVAC system (10) for carrying out the operation, and wherein the temperature and flow sensors (16, 17 and/or 18) are used for empirically determining the dependence of the flow of energy (E) and/or the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) on the volumetric flow rate ().

10. An adaptive variable flow Heating, Ventilation and Air Conditioning (HVAC) system (10), comprising: a primary circuit (26), which is traversed by the flow of an energy transporting medium, at least one energy consumer (11, 12, 13), which is connected to the primary circuit (26) by way of a supply line (14) and a return line (15), temperature sensors (16, 17) for determining the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) at the energy consumer (11, 12, 13) as well as at least one flow sensor (18) for determining the volumetric flow rate () through the energy consumer (11, 12, 13), and a controller (21, 22) that is connected to the temperature and flow sensors (16, 17 and/or 18), wherein the controller (21, 22) receives and stores measurement values, which are outputted simultaneously by the temperature and flow sensors (16, 17 and/or 18), at different times, wherein a dependence of the flow of energy (E) on the volumetric flow rate () is repeatedly determined empirically at varying time intervals by the controller, and wherein, on the basis of the determined dependence, an upper limit value (E.sub.max) of the flow of energy (E) is established, and said upper limit value is not exceeded while the HVAC system (10) is running.

11. The HVAC system, as claimed in claim 10, wherein the controller (21, 22) comprises a data logger (22).

12. The HVAC system, as claimed in claim 10, wherein the controller (21, 22) is configured for calculating and assigning the flow of energy (E) from and/or to the measurement values outputted by the temperature and flow sensors (16, 17 and/or 18).

13. The HVAC system, as claimed in claim 10, wherein the controller includes a control unit, which controls and/or regulates by way of a control valve (19) the volumetric rate of flow () through the energy consumer (11, 12, 13) and into which the limit values (E.sub.max) for the flow of energy (E) can be entered.

14. The HVAC system, as claimed in claim 13, wherein the control unit is connected to the temperature and flow sensors (16, 17 and/or 18).

15. The HVAC system, as claimed in claim 10, wherein the temperature sensors (16, 17) comprise a first temperature sensor (16) for measuring the supply temperature and a second temperature sensor (17) for measuring the return temperature, and wherein the at least one flow sensor comprises a flowmeter (18), which is disposed in the supply line (14) or the return line (15) of the energy consumer (11, 12, 13).

16. The HVAC system, as claimed in claim 10, wherein the energy consumer (11, 12, 13) comprises a heat exchanger (11), by means of which energy is released to a secondary loop (27).

17. An adaptive variable flow Heating, Ventilation and Air Conditioning (HVAC) system (10), comprising: a primary circuit (26), which is traversed by the flow of an energy transporting medium, at least one energy consumer (11, 12, 13), which is connected to the primary circuit (26) by way of a supply line (14) and a return line (15), temperature sensors (16, 17) for determining the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) at the energy consumer (11, 12, 13) as well as at least one flow sensor (18) for determining the volumetric flow rate () through the energy consumer (11, 12, 13), and a controller (21, 22) that is connected to the temperature and flow sensors (16, 17 and/or 18), wherein the controller (21, 22) receives and stores measurement values, which are outputted simultaneously by the temperature and flow sensors (16, 17 and/or 18), at different times, wherein dependence of the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) on the volumetric flow rate () is repeatedly determined empirically at varying time intervals by the controller, and wherein, on the basis of the determined dependence, a lower limit value (T.sub.min) of the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) is established.

18. The HVAC system, as claimed in claim 17, wherein the controller (21, 22) comprises a data logger (22).

19. The HVAC system, as claimed in claim 17, wherein the controller (21, 22) is configured for calculating and assigning the flow of energy (E) from and/or to the measurement values outputted by the temperature and flow sensors (16, 17 and/or 18).

20. The HVAC system, as claimed in claim 17, wherein the controller includes a control unit, which controls and/or regulates by way of the control valve (19) the volumetric rate of flow () through the energy consumer (11, 12, 13) and into which the limit value (T.sub.min) for the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) can be entered.

21. The HVAC system, as claimed in claim 20, wherein the control unit is connected to the temperature and flow sensors (16, 17 and/or 18).

22. The HVAC system, as claimed in claim 17, wherein the temperature sensors (16, 17) comprise a first temperature sensor (16) for measuring the supply temperature and a second temperature sensor (17) for measuring the return temperature, and wherein the at least one flow sensor comprises a flowmeter (18), which is disposed in the supply line (14) or the return line (15) of the energy consumer (11, 12, 13).

23. The HVAC system, as claimed in claim 17, wherein the energy consumer (11, 12, 13) comprises a heat exchanger (11), by means of which energy is released to a secondary loop (27).

24. An adaptive variable flow Heating, Ventilation and Air Conditioning (HVAC) system (10), comprising: a primary circuit (26), which is traversed by the flow of an energy transporting medium, at least one energy consumer (11, 12, 13), which is connected to the primary circuit (26) by way of a supply line (14) and a return line (15), temperature sensors (16, 17) for determining the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) at the energy consumer (11, 12, 13) as well as at least one flow sensor (18) for determining the volumetric flow rate () through the energy consumer (11, 12, 13), and a controller (21, 22) that is connected to the temperature and flow sensors (16, 17 and/or 18), wherein the controller (21, 22) receives and stores measurement values, which are outputted simultaneously by the temperature and flow sensors (16, 17 and/or 18), at different times, wherein dependence of the flow of energy (E) and/or the temperature differential T between the supply temperature (T.sub.V) and the return temperature (T.sub.R) on the volumetric flow rate () is repeatedly determined empirically at varying time intervals by the controller, and wherein results that are obtained in each case are compared with each other by the controller, in order to determine by means of the comparison a degradation of the system in function or effect.

25. The HVAC system, as claimed in claim 24, wherein the controller (21, 22) comprises a data logger (22).

26. The HVAC system, as claimed in claim 24, wherein the controller (21, 22) is configured for calculating and assigning the flow of energy (E) from and/or to the measurement values outputted by the temperature and flow sensors (16, 17 and/or 18).

27. The HVAC system, as claimed in claim 24, wherein the controller includes a control unit, which controls and/or regulates by way of a control valve (19) the volumetric rate of flow () through the energy consumer (11, 12, 13).

28. The HVAC system, as claimed in claim 27, wherein the control unit is connected to the temperature and flow sensors (16, 17 and/or 18).

29. The HVAC system, as claimed in claim 24, wherein the temperature sensors (16, 17) comprise a first temperature sensor (16) for measuring the supply temperature and a second temperature sensor (17) for measuring the return temperature, and wherein the at least one flow sensor comprises a flowmeter (18), which is disposed in the supply line (14) or the return line (15) of the energy consumer (11, 12, 13).

30. The HVAC system, as claimed in claim 24, wherein the energy consumer (11, 12, 13) comprises a heat exchanger (11), by means of which energy is released to the secondary loop (27).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention shall be explained in detail below with reference to some exemplary embodiments in conjunction with the drawings. The drawings show in:

(2) FIG. 1 a section of a simplified schematic of an HVAC system according to one exemplary embodiment of the invention.

(3) FIG. 2 the profiles of the volumetric rate of flow and the temperature differential T between the supply temperature and the return temperature in a real HVAC system, where said profiles were measured over a period of about one day.

(4) FIG. 3 the pairs of values E.sub.i(.sub.i) and T.sub.i(.sub.i), which are determined from the profiles in FIG. 2 according to the invention and which yield in each case a characteristic curve.

(5) FIG. 4 a characteristic curve E(), which is abstracted from the drawing in FIG. 3, with the plotted limit value E.sub.max; and

(6) FIG. 5 a schematic representation of a change in the curve E () caused, for example, by a degradation of the system over a prolonged period of operation.

DETAILED DESCRIPTION OF THE INVENTION

(7) FIG. 1 shows a section of a simplified schematic of an HVAC system according to one exemplary embodiment of the invention. The HVAC system 10 in FIG. 1 comprises at least one energy consumer in the form of a water/air heat exchanger 11, which is traversed by the flow of air on the secondary side. Then this air is conducted to an air duct 12 by a fan or blower 13. On the primary side the heat exchanger or more specifically the heat transfer device 11 is connected to a primary circuit 26 by means of a supply line 14 and a return line 15. An energy transporting medium, in particular water, feeds heat or cold energy to the heat exchanger 11 from a central heat or cold source, which is not depicted in the drawing, by means of said primary circuit. The medium enters the heat exchanger 11 at a supply temperature T.sub.v by way of the supply line 14 and issues again from the heat exchanger 11 at a return temperature T.sub.R by way of the return line 15.

(8) In order to determine the flow rate of the medium flowing through the heat exchanger 11, a flowmeter 18 of the customary design is disposed in the supply line 14. It goes without saying that the flowmeter may also be arranged, as an alternative, in the return line 15. In order to regulate or control the flow rate, a control valve 19 of the typical design is disposed in the return line 15; and this control valve can be adjusted by means of a controllable drive 20.

(9) In order to measure the supply temperature T.sub.V, a temperature sensor 16 is provided in the supply line. However, the supply temperature T.sub.v can also be measured at any point in the primary circuit, since this temperature is usually the same for the primary loop in its entirety and for all of the energy consumers. The return temperature T.sub.R is measured by means of an additional temperature sensor 17, which is arranged on the return line 15.

(10) During normal operation the medium enters the heat exchanger 11 at the supply temperature T.sub.V by way of the supply line. In said heat exchanger the medium releases the heat or cold energy to the air flowing through the air chamber 12 and then leaves again at a return temperature T.sub.R that deviates from the supply temperature T.sub.V. The flow of energy E that is transferred to the air flow on the secondary side is obtained, according to the aforementioned formula, from the volumetric rate of flow on the primary side and the temperature differential T between the supply temperature T.sub.V and the return temperature T.sub.R. Of interest is only the amount of the flow of energy, against the equation of the absolute value of the temperature differential T.

(11) In order to control the transfer of energy to the energy consumer, there is a control unit 21, to which the measurement values from the temperature sensors 16 and 17 and the flowmeter 18 are fed. Then the control unit 21 controls the control valve 19 in accordance with the closed loop control characteristics by way of the drive 20. FIG. 2 shows the profiles of the volumetric rate of flow and the temperature differential T between the supply temperature and the return temperature in a real HVAC system during the cooling operation, where said profiles were measured as a function of the time over a period of about one day. FIG. 2 shows very clearly the nocturnal decrease between midnight (about 12:00:00 o'clock) and the early morning (about 7:00:00 o'clock), where the volumetric rate of flow practically disappears and the temperature differential T is very low, and the high values starting after noon (about 13:00:00 o'clock).

(12) If in such an operation with a varying volumetric rate of flow and a changing temperature differential T at many different points in time t.sub.i, the associated pairs of values .sub.i and T.sub.i are logged and plotted on a graph T.sub.i (.sub.i), the result is a point distribution, as shown for the diamond-shaped points in FIG. 3. In FIG. 3 the volumetric rate of flow is given in gallons per minute (GPM; 1 GPM is equivalent to 3.785 l/min); the temperature differential is given in degrees Fahrenheit ( F.).

(13) Then the associated flow of energy E.sub.i can be calculated from the pairs of values .sub.i and T.sub.i. The corresponding point distribution E.sub.i (.sub.i) with the square points is also plotted on the graph in FIG. 3.

(14) The results of the two point distributions T.sub.i(.sub.i) and E.sub.i(.sub.i) are the characteristic curves for the energy consumer (heat exchanger 11 plus the secondary circuit); and these characteristic curves can be evaluated for the operation of the system and the evaluation and monitoring of the system. Such a characteristic E () curve with the curve profile V1 is shown in FIG. 4 as a single dotted line.

(15) This single dotted line shows again the point distribution E.sub.i(.sub.i) from FIG. 3. Based on the curve, it is now possible to select and specify in an adaptive manner a maximum energy flow value E.sub.max that is optimally adapted to the respective energy consumer, and that should not be exceeded during closed loop control of the energy consumer associated with this curve. Such a maximum energy flow value E.sub.max is obtained, according to FIG. 3, for example, from the location (upper dotted circle in FIG. 3), at which the point distribution E.sub.i(.sub.i) reaches a region B, which can be referred to as the zone of energy waste. The lower dotted circle in FIG. 3 marks the corresponding entry of the point distribution T.sub.i (.sub.i) into this zone (here, too, a curve comparable to the one in FIG. 4 can be created), so that a minimum temperature differential T.sub.min can also be used as the limit value.

(16) In the present case the sensors 16 to 18, which are present in any event for the closed loop control process, are used for determining the characteristic point distributions or more specifically the characteristic curves T.sub.i (.sub.i) and E.sub.i(.sub.i). However, it is also conceivable within the scope of the invention to provide independent sensors for this determination, so that this determination can be carried out independently of the rest of the open and/or closed loop control process.

(17) In the example from FIG. 1, in which there are no independent sensors, a data logger 22 is formed inside the control unit 21. This data logger can be implemented through special programming of a microprocessor, which is used in the control unit 21. However, said data logger can also be present as an independent electronic unit. The data logger 22 logs the measurement points .sub.i and T.sub.i in pairs at defined points in time t.sub.i and saves them in a memory unit. Added to this is then the corresponding calculated energy flow value E.sub.i. Then the resulting point distributions T.sub.i(.sub.i) and E.sub.i(.sub.i) can be displayed, for example, on an output unit 24 and, as a result, are available to the system operator as information about the respective status and the characteristic properties of the system. Based on the outputted information, suitable limit values can be entered into the control unit 21 by means of an input unit 23. However, it is, of course, also possible to let the adaptive specification of the limit values run automatically according to a given algorithm in the control unit 21 itself.

(18) In addition to the adaptive specification of the limit values T.sub.min and/or E.sub.max, the empirical determination of the characteristic distribution of the measurement points or more specifically the characteristic curves can be used to monitor the system. In the event that the transfer properties of the heat exchanger 11 degrade, for example, over a longer period of operation (for example, due to calcification, rusting or the like), the flow of energy E decreases while the volumetric rate of flow remains constant. If then at a much later time (for example, months or years) a measurement/determination of the point distribution E.sub.i (.sub.i) is and/or are repeated, the result for the resulting curve profiles is the picture shown in FIG. 5. The curve determined at a later time has a curve profile V2, which deviates significantly from the original curve profile V1, because for a particular value 1 of the volumetric flow rate the result is a flow of energy E that is reduced by E. Such a change implies a degradation of the system that can then be corrected in a targeted way within the framework of maintenance/repair work. For continuous monitoring, routine determination of the characteristic point distributions is practical.

(19) However, a direct comparison of two such curve profiles V1 and V2 is only possible if the other important operating parameters, such as the supply temperature T.sub.v and the (air) flow rate in the secondary loop of the heat exchanger 11, do not change in the meantime or change only negligibly. If, however, these variables change significantly, the measured values have to be scaled accordingly for comparison purposes either, in particular, by means of a mathematical model of the heat exchanger 11, or other (comparable) measurement results, which have been obtained with similar operating parameters, have to be used for comparison purposes.

(20) The measurement of the volumetric rate of flow by means of the flowmeter 18 can also be used advantageously to determine the pressure drop (pressure differential p between the valve inlet and the valve outlet) that occurs at the control valve 19 and to make said pressure drop useful for controlling and/or monitoring the system. The net result is a virtual pressure sensor, which makes directly acting pressure measuring means superfluous. For evaluation purposes, the correlation between the volumetric rate of flow and the pressure differential p is used, and said correlation can be described with the equation for the valve characteristic =K.sub.v p, where K.sub.v denotes the flow coefficient that depends on the valve position (valve lift), in that for a known family of characteristics for the control valve 19, for which said family of characteristics is stored in the control unit 21, the position of the control valve 19 together with the measured volumetric flow rate is transmitted to the control unit 21, where the corresponding pressure differential p can be determined, and/or if one pressure value is known, the other pressure value of the pressure differential can be determined and subsequently used. It is obvious that such a virtual pressure sensor can also be implemented with other valves and in other contexts.

(21) The proposed empirical determination of the characteristic curves and/or properties of the system offers the following advantages: If a significant sub-functioning of the heat exchanger is determined, a safety circuit can be provided. Specific limit values for T and/or E lead to savings in the energy consumption of the pumps and a reduction in the cooling capacity in the central station. The recommissioning of the system is facilitated. The efficiency of the heat exchanger can be easily checked. The system can be continuously adapted and improved. The developments and improvements of the system can be documented. The function of the heat exchanger can be compared with the manufacturer's data. A problem can be quickly identified and corrected with the acquired data. A necessary replacement of the heat exchanger can also be derived from the data. Easy diagnosis is possible for: a. fluid flow in the wrong direction b. non-functioning sensors c. obstruction of flow d. low T

LIST OF REFERENCE NUMERALS

(22) 10 HVAC system

(23) 11 heat exchanger (heat transferring device)

(24) 12 air duct

(25) 13 fan

(26) 14 supply line

(27) 15 return line

(28) 16 temperature sensor (supply temperature)

(29) 17 temperature sensor (return temperature)

(30) 18 flowmeter

(31) 19 control valve

(32) 20 drive

(33) 21 control unit

(34) 22 data logger

(35) 23 input unit

(36) 24 output unit

(37) 25 memory unit

(38) 26 primary circuit

(39) 27 secondary circuit

(40) E flow of energy

(41) T temperature differential

(42) volumetric rate of flow

(43) V1, V2 curve profile