Patent Application
20250172305
The invention relates to a method, a device and control system for operating inlet-air and waste-air heat exchangers of combined circulation systems for air-conditioning and ventilation systems.
In order to achieve a good energy efficiency of an air-conditioning system or ventilation system, a combined circulation system with heat exchangers in the inlet-air and waste-air stream is provided which are connected to one another via a hydraulic circuit and by means of which heat is withdrawn from the waste air and supplied to the inlet air in the case of heating or heat is withdrawn from the inlet air and can be supplied to the waste air in the case of cooling. In conventional systems for example, the air- and media-side temperatures and feed rates to inlet-air and waste-air heat exchangers are measured in each case to adapt the flow of the medium circulating in the heat exchangers in a continuously regulated manner to the air-side mass flow. However, this requires a relatively high expenditure since a relatively large number of sensors are required and since the regulation of the media flow through the heat exchanger(s) must be adapted and optimized depending on the numerous measured values for each specific usage and each individual system.
It is an object of the present invention to provide a method and a system whereby an efficient recovery of the heat of the waste air or heat dissipation of the inlet air (“recovery” of the cold of the waste air) can be ensured and which in the case of different air-conditioning systems and ventilation systems can be used with respectively one or more separate heat exchangers for the waste air and inlet air.
According to the invention, a method is provided in which respectively one or more heat exchangers are connected to a waste-air stream or several waste-air streams and one or more heat exchangers are connected to an inlet-air stream or several inlet-air streams of an air-conditioning and ventilation system. For each heat exchanger the temperature difference ΔT between the flow and return temperature of the heat exchanger is determined and the media flow through the relevant heat exchanger is set in such a manner that the ΔT value for the relevant heat exchanger is regulated to a target value.
In one embodiment, wherein for example, in each case one heat exchanger is provided in the inlet-air flow and one heat exchanger is provided in the waste-air flow, the setting of the media flow through the heat exchanger is accomplished in such a manner that a rotational speed of at least one speed-regulated pump is adapted.
In other embodiments wherein, for example, more than one heat exchanger is arranged in an inlet-air stream or several inlet-air streams and/or more than one heat exchanger is arranged in a waste-air stream or several waste-air streams, each heat exchanger can be assigned a delta-T control valve by means of which the flow through the relevant heat exchanger is set in such a manner that the value of the temperature difference ΔT is regulated to a target value which is either fixed in advance or can be scaled dynamically. As a result, an efficient energy recovery is achieved in a particularly simple manner merely by temperature measurements at the heat exchangers.
By controlling the at least one speed-regulated pump, a difference pressure regulation can be achieved as required to save energy of the combined circulation system. In addition, an automatic hydraulic compensation is achieved by this regulation.
The flow of the medium circulating in the heat exchangers such as for, example, a water/glycol mixture, can be controlled so that the heat exchangers can each be operated with an optimal degree of heat transfer.
According to one embodiment, the method further comprises determining and regulating the delta-T control valve which has the furthest degree of valve opening in the inlet-air and waste-air strand respectively and adapting the pressure increase due to one or more speed-regulated pumps such that the power consumption of the system is reduced to the minimum necessary.
For example, in the case of a ΔT value of a heat exchanger which is too low, the flow rate of the medium can be reduced and in the case of a ΔT value of the heat exchanger which is too high, the flow rate of the medium can be increased in order to optimize the heat transfer of this heat exchanger.
According to one embodiment of the invention, an automatic determination of an operating state of the air-conditioning and ventilation system can be executed based on the measured ΔT values, wherein the operating state comprises a heating or cooling operating state. In this case, ΔT target values for the determined operating state can be transferred to the respective delta-T control valves of the heat exchanger in the inlet-air and in the waste-air stream, and the regulation of the degree of opening for each delta-T control valve can be executed using the transferred target value. Thus, the method can be automatically set to different operating states and the energy recovery can be automatically set thereto whether the air-conditioning and ventilation system is located in a heating or cooling operating state.
In this case, the automatic determination of the operating state of the air-conditioning and ventilation system comprises determining for each heat exchanger with reference to the ΔT values whether this is in a neutral operating state, in a heating operating state or in a cooling operating state; and determining in which operating state the majority of the heat exchangers are located, wherein heat exchangers located in a neutral operating state are not taken into account. The operating state of the air-conditioning and ventilation system can be set as the operating state of the majority of the heat exchangers. If the same number of heat exchanges should be located in the heating and in the cooling operating state, the operating state corresponding to the heat exchanger with the ΔT value having the largest amount is set. As a result, in every operating situation even when, for example, individual heat exchangers and individual components of the air-conditioning and ventilation system are not in operation, an operating state can be determined and the ΔT target values can be automatically adapted with reference to the determined operating state.
In addition to energy recovery, the inlet air to the one or more inlet-air heat exchangers can be temperature-controlled by supplying heat or cold. In this case, the ΔT target value for the respective inlet-air heat exchanger can be suitably adapted to prevent the supplied energy being supplied to the waste-air heat exchangers via the return.
Since the flow rates are regulated via the valves and the pressure increase via the valve controller for an optimal degree of energy recovery, no additional hydraulic compensation of the system is necessary.
According to some embodiments, it can be further determined whether a ΔT value of a heat exchanger is less than a fixed minimum value over a defined time interval and if this is the case, the delta-T control valve of the heat exchanger can be completely closed since the heat exchanger does not contribute to the energy recovery.
The closed delta-T control valve of the heat exchanger can be opened after a pre-determined time interval and the determination of whether the ΔT value of a heat exchanger is less than a fixed minimum value over a defined time interval can be repeated after opening the delta-T control valve in order to determine whether the heat exchanger contributes to the energy recovery in the meantime. Instead of at pre-determined time intervals, this repetition can also be triggered, for example, by the fact that an energy recovery operation is briefly interrupted by a superordinate building automation and restarted when a room air technology device coupled to the heat exchanger is switched on or if no heat exchanger in the inlet-air or in the waste-air flow has a sufficiently large ΔT value.
According to a further embodiment, the present invention also provides a method for dehumidifying cold recovery (EKR) of the inlet air of an air-conditioning and ventilation system, wherein a plurality of heat exchangers are each arranged in an inlet air stream, the inlet air is cooled by a first dehumidifying heat exchanger in order to reduce the moisture content of the inlet air and the inlet air is again supplied with thermal energy by means of a downstream heat exchanger. In this case, the two heat exchangers are connected via a common media circuit and wherein the media flow through the dehumidifying heat exchanger and the downstream heat exchanger is regulated in such a manner that a ΔT value between a flow and a return temperature of the medium for each of these heat exchangers is regulated to an EKR target value. Thus, in an EKR mode the energy recovery by means of the EKR heat exchanger can be optimized by the temperature measurements of the respective flow and return temperatures without measurements of the inlet-air temperature, the inlet-air stream or the like being required.
The invention provides a device for regulating the operation of inlet-air and waste-air heat exchangers of combined circulation systems for air-conditioning and ventilation systems, a combined circulation system station and a machine-readable storage medium which contains instructions which, when executed in a processor of a controller of a combined circulation system for air-conditioning and ventilation systems, are suitable for executing the method described above.
In the following detailed description exemplary embodiments and variants of the present invention are explained with reference to the appended drawings. This merely helps to understand the invention and the invention is naturally not restricted to a specific embodiment. Features of different embodiments can be combined with one another even if this is not specifically explained in the individual case.
Furthermore, optional temperature sensors can be provided in the inlet-air stream which measure the temperature of the inlet air passing the cooler 13 and the afterheater 14. With the aid of these measured temperatures, an inlet-air temperature regulation with dehumidifying cold recovery is achieved.
A heat/cold feed module 16 can be provided for temperature control of the medium.
During operation the medium is pumped by means of one or several pumps 18 in each case through the waste-air heat exchanger(s) 11 and the inlet-air heat exchanger(s) 12, wherein a pressure compensating container 17 is provided. The flow of the medium through the waste-air heat exchanger(s) 11 and the inlet-air heat exchanger(s) 12 is controlled by delta-T control valves 19 according to the determined ΔT values, as will be explained in detail hereinafter with reference to some examples. In the exemplary embodiment shown here the delta-T control valves 19 are designed as pressure-independent control valves (PICV) 19 but other types of control valves can also be used. By means of a power control valve 20 the heat transfer between inlet-air and waste-air heat exchangers can be controlled centrally in partial load operation.
By means of the ΔT values, an operating state (for example, heating operation or cooling operation) can initially be determined. According to the determined operating state, target values for ΔT for the delta-T control valves of the inlet-air and waste-air heat exchangers 11, 12 can then be set.
The operation of the heat exchangers 13 and 14 for dehumidifying cold recovery of the waste air can then be optimized according to one embodiment whereby the temperature difference, ΔT value, between flow temperature and return temperature is also determined for these heat exchangers. Thus, the media flow through the heat exchangers 13 and 14 can be set such that the respective ΔT value is regulated to an EKR target value for the respective EKR heat exchanger. This regulation of the media flow can be accomplished by speed regulation of the pump and/or by regulating the degree of opening of delta-T control valves of the EKR heat exchanger.
According to one exemplary embodiment, during an energy/heat recovery release (WRG release) the KVS starts in the last stored operating state. During initial operation or after a fairly long down time, a neutral operating state (N) is set. The automatic operating state recognition of the heating or cooling operation (H/K) is then carried out according to the ΔT values determined for each heat exchanger 11, 12 and functions according to the majority principle. For each heat exchanger an operating state is determined with reference to the ΔT value, as specified in Table 1 below and then it is counted in which operating state the majority of heat exchangers are located. Heat exchangers not in the neutral (N) operating state are not entitled to vote. In the case of 50/50 disagreement, the ΔT value with the most significant amplitude wins the operating state vote and dictates whether the system should be in H or K operation.
In the event of a supply of energy by means of the heat/cold feed module 16 during a WRG operation, two control circuits—one for heating and one for cooling operation—have the task of regulating the WRG demand to, for example, 75%. Only one of these control circuits is active per operating state (H/K) and acts on the respective supply of heating or cooling power. The more energy is supplied, the closer the temperature of the medium at the flow of the inlet-air heat exchanger and therefore the inlet-air temperature moves towards the desired value, whereby the WRG demand decreases again. Without any supply, two ΔT target values are required per inlet-air delta-T control valve (one target value for the operating state heating, one for the operating state cooling). Respectively one additional ΔT value is required per feed. In the case of H and K feeds, therefore four ΔT target values (H; H2/K; K2) are required. During feeding the absolute ΔT target value for the inlet-air heat exchanger(s) 12 is greater than the ΔT target value without feeding. This should avoid the supplied energy being supplied to the waste-air heat exchangers 11 via the return. In order to avoid heated or cooled medium arriving at the return of the inlet-air heat exchanger 12 due to the feed and flowing to the waste-air heat exchangers 11, whereby the supplied energy would be lost, the media flow through the waste-air heat exchanger 12 is regulated in such a manner that the return temperature of the inlet-air heat exchanger 12 is held at a 5K difference in the correct direction from the return temperature of the waste-air heat exchanger medium by throttling the feed (heating operation: T inlet-air medium<T waste-air medium; cooling operation: T inlet-air medium>T waste-air medium). The function of this control circuit can be switched off.
In order to prevent any feed unintentionally influencing the operating state recognition, it can be provided that the switching of the operating state (H/N/K) only takes place after a time of the order of minutes has elapsed after a cold or heat feed.
As shown in Table 1 above, the operating states also comprise the operating state of dehumidifying cold recovery (EKR). In this case, the inlet air is cooled by the dehumidifying heat exchanger 13 to reduce the moisture content of the inlet air whereby water vapour contained in the inlet air is condensed out during cooling and thermal energy is again supplied to the inlet air by means of the downstream heat exchanger 14, wherein the two heat exchangers 13, 14 are connected via a common media circuit. Since EKR is a particularly energy-efficient method to dehumidify and pre-temperature control the inlet air stream, in this example the EKR is operated with priority over the energy recovery.
The EKR demand in this case functions as a demand for afterheating. The EKR delta-T control valve is released from an EKR demand of 10% and is blocked again at 0% (separation afterheater). The pumps 18 adjust in EKR operation and also in WRG operation to the pressure increase. The target value of the pressure increase is limited upwards via the EKR demand and downwards via the widest opening of the EKR and delta-T control valves. The widest opening of the delta-T control valves is held in EKR operation via the continuous adjustment of the pressure increase to, for example, 75%. The WRG demand does not play any part for the target value of the pressure increase in EKR.
The WRG delta-T control valves separates the waste-air heat exchanger 11 when the return temperature of the inlet-air heat exchanger 12 in the KVS station is lower than the return temperature of the waste-air heat exchanger 11. In this case, the release is withdrawn from the waste-air heat exchangers 11 and they close completely. This state can be cyclically temporarily cancelled and re-examined. This examination is based on the automatic recognition of the operation of inlet-air and waste-air heat exchangers 11, 12 and is started immediately.
In cooling operation it can furthermore be appropriate to perform an adiabatic cooling of the waste-air stream. If the calculated wet bulb temperature upstream of the humidifier is at least 2K below the measured waste-air temperature there, the release of a waste-air humidifier for adiabatic cooling is appropriate. For dehumidifying operation it holds that: if the calculated wet bulb temperature upstream of the humidifier is at least 2K below the measured waste-air temperature there, the release of a waste-air humidifier for adiabatic cooling is appropriate when it is a further 2K below the return temperature measured in the KVS station 10 to the waste-air heat exchangers 11.
Furthermore, in the KVS station 10 shown in
As a further optional addition to the previously described method, an automatic detection of the operation of inlet-air and waste-air heat exchangers 11, 12 can be carried out. In this case, during WRG release all the delta-T control valves 19 firstly receive their release for delta-T control. If the ΔT value of a delta-T control valve 19 remains almost zero for a certain time (e.g. ±2K) or even has a reversed-direction sign, the relevant heat exchanger makes no contribution to the WRG or its use and the corresponding room air technology device on the waste-air or inlet-air side is presumably not active. The release is then withdrawn from the delta-T control valve 19 whereby it closes completely.
This state can be cyclically temporarily cancelled per delta-T control valve 19 and re-examined if, for example, one or more of the following conditions are satisfied:
All the options listed above can be parametrized and selected or deselected. If none of the options is selected, the delta-T control valves receive the release of the WRG without further restrictions.
If a humidifier for adiabatic cooling should be provided, the air-conditioning or ventilation system can release this for cooling (in good time before the testing) if appropriate. The operating state recognition automatics takes into account the cooling potential thereby provided during testing.
In general, for example, a digital signal for WRG release, an optional analog WRG demand with an external temperature control or external temperature target value specification with a temperature control by the KVS station 10, an optional analog EKR demand with external temperature control, an analog temperature target value which can be received at the same input as the WRG demand and which is optional with a temperature regulation by the KVS station 10, an optional analog value of the waste-air temperature for determination of the dew point and/or an optional analog vale for the waste-air humidity can be received at the KVS station 10 as input quantities for a method according to one embodiment. In particular, the temperature and moisture values can be measured with the required sensors at the KVS station 10.
For example, in this embodiment an energy recovery can be performed in such a manner that after release of the KVS station one of the pumps 18 starts from a WRG demand of 10% (switch-off hysteresis—10%). Between 0% and 10% WRG demand the WRG power valve 20 opens from 0% to 100%. Via the WRG demand the difference pressure target value of the pumps is interpolated linearly between minimum and maximum. The difference pressure is limited (throttled) upwards by a control circuit which controls the delta-T between flow and return of the waste-air heat exchanger 11. As a result, the pump speed is optimized as required which reduces the average energy requirement.
The delta-T target values for the heating and cooling case can be calculated in the planning process for each delta-T control valve 19 and predefined as fixed values. The same applies to the minimal and nominal flow rates per valve which can be individually configured during commissioning for each plant. Within these limits the respective delta-T control valve 19 can run in an independently continuously operated manner to keep the temperature difference ΔT at its target value.
After release of the KVS station, one of the pumps 18 starts from a WRG demand of, for example, 10% (switch-on hysteresis-5%). Between 0% and 10% WRG demand, the WRG power valve opens from 0% to 100%. Via the WRG demand the difference pressure target value of the pumps is interpolated linearly between minimum and maximum as shown schematically in
The pressure difference is limited upwards (throttled) by a control circuit which limits the largest valve opening of the delta-T control valves 19 (maximum of yzmax and yamax=xFmax)) downwards to for example 75%. As a result, the pump speed is optimized as required, which reduces the average energy requirement.
In the case of a thermal nonequilibrium between inlet-air and waste-air heat exchangers at least one delta-T control valve 19 in the inlet- and waste-air opens in the direction of 100%. In order to promote the automatic hydraulic compensation in this scenario and therefore optimize the WRG power, the air side with the widest valve opening requires more media flow than the opposite air side. This is achieved with an additional control circuit which is responsible for limiting the maximum valve opening of the inlet-air and waste-air heat exchanger to, for example, 85% opening. The control signal of this control circuit acts on the opening of the frost protection valve 21 when the relevant valve is located on the waste-air side and on the bypass via the WRG power valve 20 when it is located on the waste-air side. The frost protection valve has priority here. Whilst the frost protection valve 21 is open, the bypass of the WRG power valve 20 remains closed. It cannot occur that the bypass of the WRG power valve 20 and the frost protection valve 21 are open at the same time.
According to one embodiment, the software for implementing the previously described method can be constructed in a layer model, wherein in a first phase the hydraulic control is carried out whereby as described previously, an energy-efficient pump operation and an efficient use of supplied energy is achieved by delta-T management and optionally by supplying heat and/or cold to the medium. In a second phase, regulation of the air temperature takes place which involves regulation of the waste air and/or inlet air and optionally an adiabatic cooling and/or dehumidifying cold recovery. In a third phase optimization functions are then implemented which, for example, enable a more rapid settling of the control circuits by calculated starting and limiting values for control signals.
Furthermore an automatic compensation is carried out (S5), wherein the flow through the heat exchangers can be compensated via the power valve 20. A frost protection control (S6) prevents any formation of frost by controlled opening of the frost protection valve 21.
Finally external supplies of heat and cold can be taken into account (S7, S8) wherein the WRG demand is adapted accordingly to efficiently use the supplied energy.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102023133443.3 | Nov 2023 | DE | national |
