Patent Application
20230417443
The present invention relates to a method of controlling thermal power transfer of a thermal energy exchanger of a Heating, Ventilating and Air Conditioning HVAC system. The present invention further relates to a controller controlling a thermal power transfer of a thermal energy exchanger of an HVAC system. The present invention further relates to a computer program product comprising instructions, which, when executed by a processor of a controller control a thermal power transfer of a thermal energy exchanger of an HVAC system.
By regulating the flow of fluid through a thermal energy exchanger of an HVAC system, it is possible to adjust the amount of energy (respectively the amount of energy per unit of time, power) transferred by the thermal energy exchanger. For example, the energy exchange or the power transfer, correspondingly, is adjusted by regulating the amount of energy delivered by the thermal energy exchanger to heat or cool a room in a building, or by regulating the amount of energy drawn by a chiller for cooling purposes. While the fluid transport through the fluid circuit of the HVAC system is driven by one or more pumps or fans, the flow is typically regulated by varying the orifice (opening) or position of valves, e.g. manually or by way of actuators.
The actual power transfer characteristics of thermal energy exchangers in an HVAC system depend on various environmental conditions such as temperature, humidity, etc. In stable/static scenarios, calculating of the power transfer Q≈ϕ·ΔT is sufficiently accurate for controlling the power transfer. However, in an HVAC system with numerous transient events and processes, e.g. frequently changing flow rates and temperature differentials ΔT, this basic calculation of power transfer Q≈ϕ·ΔT alone is often not sufficient for accurate control of power transfer.
According to a known method respectively control system for controlling energy transfer of a thermal energy exchanger of an HVAC system with numerous transient events and processes, a flow sensor measures the flow of fluid through the thermal energy exchanger, a first temperature sensor measures a supply temperature to a thermal energy exchanger, and a second temperature sensor measures a return temperature from the thermal energy exchanger. A control system determines flow-dependent model parameters for modelling performance of the thermal energy exchanger, using one or more measurement data sets, whereby each measurement data set includes for a respective measurement time a value of the measured flow of fluid, a value of the measured supply temperature of the fluid, and a value of the measured return temperature of the fluid. Using the flow-dependent model parameters, the control system calculates an estimated energy transfer of the thermal energy exchanger, and controls the energy transfer of the thermal energy exchanger by regulating the flow of fluid through the thermal energy exchanger, using the estimated energy transfer.
However, this solution requires several sensors to measure environmental variables, in particular at least a temperature sensor for the measurement of the supply temperature to a thermal energy exchanger, and a second temperature sensor for the measurement of the return temperature from the thermal energy exchanger.
It is an object of this invention to provide a method and a control system for controlling power transfer of a thermal energy exchanger of an HVAC system, which method and control system do not have at least some of the disadvantages of the prior art.
In particular, it is an object of the present invention to provide a method and a control system for controlling power transfer of a thermal energy exchanger of an HVAC system in dynamic environmental conditions with a reduced need for sensors.
According to the present invention, these objectives are addressed by a method of controlling a thermal power transfer of a thermal energy exchanger of an HVAC system. In a first step of the method according to the present invention, a setpoint thermal power transfer is received by a controller. In a further—subsequent or simultaneous step, a flow of fluid through the thermal energy exchanger at a current position of a valve of the HVAC system arranged for regulating a flow of a fluid through the thermal energy exchanger is measured by a flow sensor. Using the measured flow of fluid, the controller determines an estimated thermal power transfer based on a defined flow rate to delta-T mapping.
In particular, the flow rate to delta-T mapping is defined as a relation between a flow rate of fluid through the thermal energy exchanger and a temperature differential over the thermal energy exchanger. According to embodiments of the present disclosure, the flow rate to delta-T mapping is defined based on calculations, and/or mathematical models and/or measurements of flow rates and temperature differentials over thermal energy exchangers. According to embodiments of the present disclosure, the flow rate to delta-T mapping is calibrated and/or repeatedly refined based on measurements of flow rates and temperature differentials over thermal energy exchangers of the HVAC system or other HVAC systems.
Having determined the estimated thermal power transfer, the controller compares the setpoint thermal power transfer and the estimated thermal power transfer.
Thereafter, the controller controls the flow of fluid through the thermal energy exchanger based on the comparing, in particular by generating a control signal based on the comparing in order to thereby control the thermal power transfer of the thermal energy exchanger.
According to a first embodiment of the present disclosure, the controller regulates the flow of the fluid through the thermal energy exchanger by generating a valve control signal for controlling an orifice of a valve of the HVAC system. The valve is arranged in a flow path of the thermal energy exchanger and energy source, e.g. a heating device (furnace, heat pump) or a cooling device (chiller) such as to regulate the flow of a fluid to and/or from the thermal energy exchanger. In particular, the vale is arranged in a fluid transport system for moving a (thermal transfer) fluid, for example a liquid, e.g. water and/or a refrigerant, or a gas, e.g. air, to and from the thermal energy exchanger. The fluid transport system may comprise fluid transport lines (pipes or ducts), for conducting a flow of fluid through the thermal energy exchanger.
According to a further embodiment of the present disclosure, the controller regulates the flow of the fluid through the thermal energy exchanger by generating a pressure control signal for controlling a supply pressure of the fluid. In particular, the supply pressure of the fluid is provided by a pump or fan, for driving and controlling the flow of the fluid through the thermal energy exchanger. Correspondingly, the pressure control signal is generated for controlling a pump or fan, for driving and controlling the flow of the fluid through the thermal energy exchanger. According to embodiments of the present disclosure, the pump or fan is comprised by or connected to the HVAC system.
According to embodiments disclosed herein, the controller controls the thermal power transfer by generating a control signal (valve control signal and/or pressure control signal) based on the comparing such as to minimize the difference between the setpoint thermal power transfer and the estimated thermal power transfer.
According to embodiments of the present disclosure, the flow rate to delta-T mapping is defined based on one or more of:
According to embodiments of the present disclosure, as part of determining the estimated thermal power transfer, the controller determines an estimated temperature differential over the thermal energy exchanger based on the measured flow of the fluid, wherein the controller determines the estimated thermal power transfer based on the measured flow of fluid and the estimated temperature differential.
According to embodiments of the present disclosure, a temperature of a secondary fluid through and/or around the thermal energy exchanger is measured by a temperature sensor. Alternatively, data indicative of the temperature of the secondary fluid is received by the controller (from a data source/sensor external to the HVAC system). The flow rate to delta-T mapping is defined and/or calibrated using the temperature of the secondary fluid.
For example, in a cooling operating mode of the thermal energy exchanger, for an assumed constant supply temperature (e.g. 6° C.) of the fluid, the flow rate to delta-T mapping is determined using extrapolation based on (empirical data):
Hence, the thermal power transfer can be estimated precisely even without the need for a temperature sensor of supply temperature or return temperature of the fluid. According to embodiments of the present disclosure, a supply temperature or a return temperature of the fluid is measured by a temperature sensor. Alternatively, data indicative of the supply temperature or return temperature of the fluid is received by the controller (from a data source/sensor external to the HVAC system). Thereafter, the flow rate to delta-T mapping is calibrated using the supply or return temperature of the fluid.
In order to control the orifice of the valve and thereby the flow of fluid through the thermal energy exchanger, embodiments of the present invention further comprise the steps of transmitting, by the controller, the valve control signal to an actuator mechanically coupled to the valve and actuating the valve, by the actuator, in accordance with the valve control signal.
In order to control the supply pressure and thereby the flow of fluid through the thermal energy exchanger, embodiments of the present invention further comprise the steps of transmitting, by the controller, the pressure control signal to a device for driving and controlling the flow of the fluid such as a pump or fan, and controlling the pump or fan in accordance with the pressure control signal.
The above-identified objectives are further addressed according to the present invention by a controller for controlling thermal power transfer of a thermal energy exchanger, the controller comprising a processor configured to carry out the method according to one of the embodiments disclosed herein.
The above-identified objectives are further addressed according to the present invention by an HVAC system comprising: a thermal energy exchanger; a controller communicatively connected to the actuator; and a flow sensor configured for measuring a flow of fluid through the thermal energy exchanger. The controller is configured to: determine an estimated thermal power transfer, using the measured flow of fluid and a defined flow rate to delta-T mapping;
According to embodiments of the present disclosure, the HVAC system (1) further comprises a valve (40) having an orifice and an actuator (20) mechanically coupled to the valve (40). The control signal, generated by the controller (10), comprises a valve control signal for controlling an orifice of the valve (40) of the HVAC system (1). The controller (10) is further configured to transmit the valve control signal to the actuator (20), the actuator being configured to actuate the valve controlling the orifice such as to regulate the flow of a fluid through a thermal energy exchanger in accordance with the valve control signal.
According to further embodiments of the present disclosure, the HVAC system further comprises a pump (100) for driving the fluid (W) through the thermal energy exchanger (90). Correspondingly, the control signal, generated by the controller (10), comprises a pressure control signal for controlling a supply pressure of the fluid (W). The controller (10) is further configured to transmit the pressure control signal to the pump (90), the pump (90) being configured drive the fluid (W) through a thermal energy exchanger (80) at a supply pressure in accordance with the pressure control signal.
Known particular application of HVAC systems comprises a 2- or 3-way flow regulator arranged in a flow path of a heat exchanger and fluid source(s), the flow regulator allowing regulating the flow of fluid by actuation between an opened and closed position.
A further known particular application of HVAC systems comprises a 6-way flow regulator arranged between a heat exchanger and a fluid source of a first temperature and a fluid source of a second temperature. In particular, 6-way flow regulators are used in applications when the same heat exchanger is being used for both heating and cooling, the 6-way flow regulator being arranged to switch the heat exchanger's fluid input and return between a first respectively a second fluid circuit. 6-way flow regulators comprise a first fluid input; a second fluid input; a fluid output; a fluid return input; a first fluid return output; and a second fluid return output. Known 6-way flow regulators may be operated in a first operating mode, a second operating mode and a third operating mode. In the first operating mode, the 6-way flow regulator enables a flow of fluid from the first fluid input towards the fluid output and a flow of fluid from the fluid return input towards the first fluid return output. In the second operating mode, the 6-way flow regulator enables a flow of fluid from the second fluid input towards the fluid output and a flow of fluid from the fluid return input towards the second fluid return output. In the third operating mode, the 6-way flow regulator prevents passage of fluid between any of the first fluid input; the second fluid input; the fluid output; the fluid return input; the first fluid return output and the second fluid return output.
It is an object of further embodiments of the present invention to enable an HVAC system comprising a 6-way flow regulator to operate in view of environmental conditions while avoiding at least part of the disadvantages associated with known solutions. According to embodiments of the present disclosure this further objective is addressed by an HVAC system having a 6-way flow regulator wherein the actuator is configured to control the 6-way flow regulator in the first operating mode and second operating mode in accordance with the valve control signal. In the first operating mode, controlling the orifice of the 6-way flow regulator enables: regulating the flow of fluid from the first fluid input towards the fluid output; and regulating the flow of fluid from the fluid return input towards the first fluid return output. In the second operating mode, controlling the orifice of the 6-way flow regulator enables regulating the flow of fluid from the second fluid input towards the fluid output; and regulating the flow of fluid from the fluid return input towards the second fluid return output.
The above-identified objectives are further addressed according to the present invention by a computer program product comprising instructions, which, when executed by a processor of a controller of an HVAC system comprising a thermal energy exchanger and a flow sensor cause the HVAC system to carry out the method of controlling a thermal power transfer of a thermal energy exchanger according to one of the embodiments disclosed herein.
It is to be understood that both the foregoing general description and the following detailed description present embodiments, and are intended to provide an overview or framework for understanding the nature and character of the disclosure. The accompanying drawings are included to provide a further understanding, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments, and together with the description serve to explain the principles and operation of the concepts disclosed.
The herein described disclosure will be more fully understood from the detailed description given herein below and the accompanying drawings which should not be considered limiting to the disclosure described in the appended claims. The drawings which show:
Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all features are shown. Indeed, embodiments disclosed herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numbers will be used to refer to like components or parts.
It can be seen that increasing the flow rate ϕ increases the thermal power transfer. However, the behavior is nonlinear. As the flow rate ϕ continues to increase, the commensurate increase in thermal power transfer Q steadily reduces. In fact, a levelling off can be seen such that at high flow rates ϕ, increasing the flow rate ϕ further results in little increase in the thermal power transfer Q. The thermal energy exchanger 80 is said to be operating at saturation once the levelling off occurs. Saturation occurs when the thermal energy exchanger 80 has reached a state such that further increasing the flow rate ϕ does not result in significantly greater thermal power transfer Q. Depending on the embodiment, the point at which saturation occurs is defined differently. For instance, the saturation point SAT can be calculated as a percentage of the thermal power transferred by the thermal energy exchanger 80 at a maximum flow rate ϕ.
For illustrative purposes, in the scatter plot of
In general, little or no additional heat can be transferred by operating the thermal energy exchanger 80 above the saturation point SAT, the additional energy by the pump to drive the fluid through the pipes and the thermal energy exchanger 80 results in a lowered overall efficiency of the HVAC System 1.
Turning now to
The controller 10 shall be described below in greater detail reference to
The thermal energy exchanger 80 is a device configured to transfer thermal energy between a fluid W to its environment, in particular by means of a secondary fluid A, e.g. air. Depending on the application and configuration, the thermal energy exchanger 80 comprises a heat exchanger or a chiller, for example. The secondary fluid A is air used for heating and/or cooling a building, in particular a room of the building. According to embodiments, the secondary fluid A may be driven through the thermal energy exchanger 80 by a fan. In an embodiment, the secondary fluid A moves through the thermal energy exchanger 80 passively, i.e. due to wind or convective forces. The thermal energy exchanger 80 provides energy to the secondary fluid A, if the temperature of the fluid W is greater than the temperature of the secondary fluid A and in this case acts as a heater. The thermal energy exchanger 80 draws energy from the secondary fluid A if the temperature of the fluid W is less than the temperature of the secondary fluid A and in this case acts as a cooler.
The valve 40 is a device for regulating the flow of fluid W by means of an orifice. Arranged between an energy source and a heat exchanger 80, the valve 40 is configured to regulate the flow of fluid W to and from heat exchanger 80.
The HVAC system a may further comprise a fluid transport system 60 for moving a (thermal transfer) fluid, for example a liquid, e.g. water and/or a refrigerant, or a gas, e.g. air, to and from the thermal energy exchanger 80. The fluid transport system 60 may comprise fluid transport lines (pipes or ducts), for conducting a flow of fluid through the thermal energy exchanger 80 and the valve 40.
Figure g shows an illustrative view of a controller 10 connected to an actuator 20 mechanically coupled to a valve 40 according to the present invention, the valve 40 being arranged to regulate the flow of fluid W through a fluid transport system 60.
In the following paragraphs, described with reference to
In a further—subsequent or simultaneous step S20, a flow of fluid ϕact through the thermal energy exchanger 80 is measured by a flow sensor 52.
In a step S30, using the measured flow of fluid ϕact, the controller 10 determines an estimated thermal power transfer Power EST based on a defined flow rate to delta-T mapping. According to embodiments of the present disclosure, step S30 comprises determining, by the controller 10, an estimated temperature differential ΔT over the thermal energy exchanger 80 based on the measured flow ϕact of the fluid W, wherein the controller 10 determines the estimated thermal power transfer Power EST based on the measured flow of fluid ϕact and the estimated temperature differential ΔT.
Having determined the estimated thermal power transfer Power EST, in a step S40, the controller 10 compares the setpoint thermal power transfer Power SP and the estimated thermal power transfer Power EST.
In a subsequent step S50, the controller 10 controls the flow ϕact of fluid W by generating a control signal based on the comparing. According to embodiments disclosed herein, the controller 10 controls the flow ϕact of fluid W by generating a control signal based on the comparing such as to minimize the difference between the setpoint thermal power transfer Power SP and the estimated thermal power transfer Power EST.
According to embodiments of the present disclosure, the flow rate to delta-T mapping is defined based on calculations, and/or mathematical models and/or measurements of flow rates and temperature differentials over thermal energy exchangers.
Thereafter, in a step S28, the flow rate to delta-T mapping is calibrated using the measured return temperature TIN of the fluid W.
| Number | Date | Country | Kind |
|---|---|---|---|
| 01653/20 | Dec 2020 | CH | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/081362 | 11/11/2021 | WO |
