US20130081799A1

US20130081799A1 - Method for setting the volumetric flow rate of a heating and/or cooling medium by means of room heat exchangers of a heating or cooling system

Info

Publication number: US20130081799A1
Application number: US13/702,699
Authority: US
Inventors: Maximilian Löblich; Bertram Hübner
Original assignee: Loeblich and Huebner Energie Effizienz und Haustechnik GmbH
Current assignee: LOBLICH & HUBNER ENERGIE-EFFIZIENZ und HAUSTECHNIK GmbH
Priority date: 2010-06-09
Filing date: 2011-06-09
Publication date: 2013-04-04
Also published as: RU2575961C2; CN103154842B; EP2580630B1; WO2011153572A1; AT509913B1; RU2012157565A; EP2580630A1; CN103154842A; AT509913A1

Abstract

Room heat exchangers of varying priority are provided by setting the volumetric flow rate of a medium by means of the room heat exchangers of a heating or cooling system. A target spread of the flow and return temperatures for each individual room heat exchanger(s) is set by fixably or adjustably limiting the respective room heat exchanger valve(s). A system-specific target spread for high-priority room heat exchangers is a basis to allow a lower target spread and a higher target spread is ensured given low-priority room heat exchangers. When operating in a high-priority room heat exchanger with a lower spread, the volumetric flow through at least one low-priority room heat exchanger with a higher spread is changed in such a way that a return temperature optimized for the heating device of the heating system is set by mixing the return medium from all room heat exchangers of the heating system.

Description

The invention relates to a method for setting the volumetric flow rate of a heating and/or cooling medium by means of room heat exchangers of a heating or cooling system, in which the target spread of the flow and return temperatures for the individual room heat exchangers is in each case set by limiting the respective room heat exchanger valve in an adjustable and/or fixable manner.
As a rule, such methods are used in heating systems to limit the maximum flow through the individual room heat exchangers that the user can set with the room heat exchanger valve, so that, when the valves have been completely opened, all room heat exchangers are supplied with heating medium in such a way that the identical spread arises at all room heat exchangers (hydraulic balancing). The differences in heating medium supply are rooted in the relatively strong variability of the hydraulic resistances of the pump that stem from the differing tube dimensions and lengths, as well as from changes in direction.
In conjunction with the present invention, room heat exchangers are understood to be heating elements or radiators as well as cooling elements, for example air conditioning systems, in which the indoor air is heated or cooled. In the technical field in question, the spread is understood as the difference between the flow and return temperature of the heating medium, which arises when the heating medium flows through the room heat exchanger, and releases heat to the room to be heated or cooled in the process. For the sake of simplicity, reference is most often made to heating in the present specification, although instances of cooling a room are also always conceivable and intended.
Among other things, the spread on the one hand depends on the ambient temperature of the room heat exchanger, but on the other hand also depends primarily on how fast the heating medium flows through the room heat exchanger on the other, since obviously the medium cools to a relatively little extent given a high flow rate, i.e., a short retention time in the room heat exchanger, while a relatively rapid cooling takes place in the room heat exchanger given low flow rate, i.e., given a long retention time. Given a high flow rate through a room heat exchanger, which is tantamount to a low spread, the room heat exchanger is operated at a high heat output, since the entire heating surface of the room heat exchanger is used, so that a lot of heat is released into the environment.
In order to operate a heating system in an energy-efficient manner, the goal is to achieve both a specific return temperature for the heating medium to the heater, and in general the lowest possible temperature level, depending on the heating unit. Only in the case of steel boilers is a return temperature of under 35° C. disadvantageous, since the condensation of water vapor from the exhaust gas can then lead to corrosion problems. In modern condensing boilers, however, a low return temperature is in turn required so the moisture contained in the exhaust gas can be condensed on corresponding heat exchangers, and the condensation heat obtained in the process can be utilized for warming up the heating medium.
The hydraulic balancing to a spread identical for all room heat exchangers of a heating system mentioned at the outset is only beneficial in terms of energy if each room or area of the building to be heated is actually equipped with respective optimally dimensioned room heat exchangers. However, this is virtually never the case in practice, since not only is suitability in terms of energy engineering taken into account during the installation of room heat exchangers; aesthetic aspects and their actual availability at the desired time of installation also play a role, in particular in the concluding phase of a construction project. In addition, room heat exchangers are not continuously available for each operating level. As a result, the room heat exchangers are in practical terms only very rarely optimally dimensioned in a room or area, so that a hydraulic balancing according to prior art to an identical spread for all room heat exchangers will not satisfy the actual energy requirements. Beyond that, heating systems are as a rule not operated with a focus on energy engineering above all in the private areas, with the user instead briefly regulating the room heat exchanger valves or thermostatic heads based on a subjective sensitivity to cold, so that an unfavorably high heat output is often demanded of individual room heat exchangers, while very low temperatures are selected in other areas as a presumed cost-cutting measure. However, especially low temperatures in rooms next to rooms with a high temperature result in a loss of heat in the high-temperature rooms (in particular when doors are left open), so that the room heat exchangers must in turn be operated at a very high heat output level in order to maintain the temperature required in these rooms, which increases the return temperature of the system overall, and hence lowers the efficiency of the heating system.
Therefore, the object of the present invention is to set or hydraulically balance the room heat exchangers of a heating system in such a way as to take stock of undersizing or oversizing, or user requirements that are unfavorable from an energy standpoint, while at the same time keeping the return temperature of the entire system at a favorable level.
This object is achieved by further developing a method of the kind mentioned at the outset according to the invention in such a way that room heat exchangers of varying priority are defined, wherein a system-specific target spread for high-priority room heat exchangers is used as the basis to allow a lower target spread, and a higher target spread is ensured given low-priority room heat exchangers, and that, during the operation of a high-priority room heat exchanger with a lower spread, the volumetric flow through at least one low-priority room heat exchanger with a higher spread is changed in such a way that a return temperature optimized for the heating device of the heating system is set by mixing the return medium from all room heat exchangers of the heating system.
As a consequence, the method according to the invention defines high-priority room heat exchangers as room heat exchangers which are constantly or temporarily required to exhibit a heat output lying above the heat output that can be achieved when complying with the system-specific target spread. For example, this is the case when the room heat exchangers in a room or area are themselves undersized in terms of providing the thermal output necessary there, or if a user wants to quickly heat up the environment for a brief time, and therefore widely opens the room heat exchanger valve. In order to compensate for the excess amount of heat fed into the return flow from room heat exchangers operated in this manner so as to achieve an optimized return temperature for the heating system, the method according to the invention provides that certain room heat exchangers be defined as low-priority room heat exchangers, wherein a very high spread intended to exceed the system-specific target spread is ensured for such room heat exchangers. For example, such room heat exchangers are room heat exchangers in rooms or areas that are oversized for the heat needed there, or room heat exchangers in areas where high heat-up dynamics are not required or only a certain basic supply of heat is to be ensured. Meant in this conjunction are basements and dens, heated garages, workout rooms, secondary rooms and similar areas in buildings. In such areas, very high spreads can be accommodated, since no rapid heating is normally required there, and it is sufficient to supply a certain amount of heat at a specific time of day, so as to prevent the area from cooling down completely. Operating low-priority room heat exchangers at a high spread, i.e., with very low return temperatures, makes a relatively cool return medium available, which mixes with the hot heating medium from the high-priority room heat exchangers in the return flow of the heating system, so that a temperature balancing takes place, an acceptably low return temperature is achieved overall, and the system can be efficiently operated despite the individual room heat exchangers being oversized and undersized. As a consequence, the invention deviates from the concept of hydraulic balancing described at the outset in that different spreads are deliberately set, and can also be fixed by suitable limiters, so that the portrayed deviations from the system-specific target spread in the room heat exchangers of the heating system are balanced out using all heating surfaces of the heating system, as a result of which even heating systems without an optimal design, for example those often encountered in old buildings, can be enhanced to exhibit a satisfactory energy efficiency level.
The respective actually achieved target spread clearly depends on how many heating elements of a system are even operated after adjustment, since when a user closes room heat exchanger valves, the volumetric flow rate, and hence the flow pressure in the still operating room heat exchangers, rises, so that the target spread can in turn be dipped below. This effect can be countered by variably controlling the feed pump of the heating system. However, in the simplest case, the balancing desired according to the invention is also achieved by ensuring the target spread in the respective heating elements for a case in which all room heat exchanger valves are opened.
In a preferred embodiment of the present invention, the spread selected for low-priority room heat exchangers is so high that the return temperature is set in such a way as to achieve the system-specific target spread. At the system-specific target spread, the respective heating devices, e.g., gas and oil burners, wood chip heaters, but also other thermal sources like district heating, can be operated at their energy optimum, enabling the best possible utilization of the employed energy source.
Implementation of the method according to the invention is facilitated when taking into account operating parameters for all room heat exchangers or heating surfaces of a building, wherein, in order to achieve the effect desired according to the invention, specifically to obtain a return temperature optimized for the respectively used heat generator, the amounts of heat can be acquired or determined, and the thermal loads, i.e., the excess amounts of heat from high-priority room heat exchangers, can be economized accordingly in low-priority room heat exchangers, for example. So as to be able to quickly and controllably implement this approach in practice, the method according to the invention is preferably developed further so as to acquire the supply and return temperatures of the individual room heat exchanger and transmit them to a central processing unit, which determines control values for the adjustable and/or fixable limitation of all room heat exchanger valves, and transmits them as a control signal to in particular removable actuators on the room heat exchanger valves. For this purpose, temperature sensors are secured to the room heat exchangers at the supply and return points of the room heat exchanger, which relay the measured values to the central processing unit in a wireless or tethered manner. The values are there compared with the desired values, and the commands for the next switching step are sent after a corresponding waiting period. As an alternative, the amounts of heat released by individual room heat exchangers into the return flow are calculated in the central processing unit in a known manner, wherein a corresponding adjustment of the adjustable and/or fixable limitation is introduced on the room heat exchanger valves or thermostatic heads by means of actuators or motor units. After the system has been balanced using the method according to the invention, the control values can either be fixed manually via mechanical stops, or the control values can be stored in the actuator units. Once the control values that limit the flow through the room heat exchanger valves have been set, the motor units can either be removed, or be left on the room heat exchangers. The data can be stored in the central processing unit, and be used to calculate heating costs, for example. The data can here be read remotely in an especially advantageous way.
As already mentioned, a room heat exchanger can be categorized as a high or low-priority room heat exchanger, based on the consideration of whether the respective room heat exchanger is oversized or undersized for the respective area. However, prioritization can also take place dynamically, wherein the preferred procedure is to use a measured value for the outside temperature to calculate the control value of at least one high or low-priority room heat exchanger.
If the aforementioned actuators or motor units remain on the room heat exchangers, an especially favorable adaptive mode of operation can be achieved for the heating system, which makes it possible to also respond to temporary user requirements placed on individual room heat exchangers in individual rooms or areas. For example, the method can preferably be implemented in such a way that, given a temporary operational requirement on a room heat exchanger that leads to a decrease in the spread on the room heat exchanger in question, this room heat exchanger is subjected to prioritization, whereupon the volumetric flow rate of heating medium through at least one low-priority room heat exchanger is lowered to balance the return temperature of the heating system. As a consequence, this dynamic change in priorities of the individual room heat exchangers makes it possible to diminish the volumetric flow rate through the room heat exchangers in certain areas of a building, so that the resultantly increasing spread on these room heat exchangers yields a cool return medium. Since the return flow amounts of room heat exchangers operated with a high spread, i.e., at a low flow rate, are clearly comparatively slight, balancing the excess amounts of heat fed into the return flow from a room heat exchanger operated with too low a spread as a rule requires that several room heat exchangers be operated with a high spread, so as to provide for a sufficiently cool return flow medium.
For example, given an unexpected heating requirement on the part of a user in a phase where a building is not being heated all that much, for example to quickly heat up a workroom in the night hours, a very low spread in turn results on the corresponding room heat exchanger. In this case, the method according to the invention can preferably be implemented in such a way that, given a temporary operating requirement on a room heat exchanger that results in a diminished spread on the room heat exchanger in question, this room heat exchanger is subjected to a prioritization, whereupon the return temperature of the heating system is balanced by increasing the flow rate of heating medium through at least one low-priority room heat exchanger. While this measure clearly leads to a resultantly decreased spread in these low-priority room heat exchangers, increasing the flow rate makes it possible to obtain a cool return flow medium from these room heat exchangers, which benefits the overall efficiency of the heating system. Therefore, at least one room heat exchanger is again operated with a high spread in such a way as to yield an optimized return temperature. This also represents a dynamic definition of priorities, and is introduced by the central processing unit. As a consequence, the central processing unit assigns a high priority to the room heat exchanger from which a high heat output is required, and correspondingly activates the actuators to permit a low spread, and hence a high heat output on the room heat exchanger in question. This room heat exchanger subsequently supplies unfavorably hot return medium in the return flow of the heating system, whereupon an elevated flow through one or more low-priority room heat exchangers takes place in the preferred method. A low-priority room heat exchanger is here in turn a room heat exchanger in a room in which a specific heat output is not directly required, but the flow rate through such low-priority room heat exchangers is elevated to increase the overall efficiency of the system, so that having the return medium obtained from these areas cool the return point raises the efficiency of the heat exchanger in the heat generator. The preferred method can here even be implemented in such a way as to not just increase an already existing flow rate in a low-priority room heat exchanger, but to start up a room heat exchanger that had itself not been operational at the time in question, which in turn is accomplished by sending a corresponding control signal from the central processing unit to the actuators or motor units in question.
A preferred embodiment of the method according to the invention here involves a process in which a temporary user requirement is issued by inputting a desired value for the ambient temperature, the desired value is sent to the central processing unit, and control values for the room heat exchanger(s) situated in the respective room are calculated in the central processing unit and transmitted as a control signal to the actuators on the room heat exchanger valves.

The invention will be explained in greater detail below based on an exemplary embodiment shown on the drawing. In the latter, FIG. 1 presents a schematic depiction of a heating system for implementing the method according to the invention.

A heating system is denoted by 1 on FIG. 1. The heating system 1 exhibits a heating device 2 and a series of room heat exchangers 3 and 4. The room heat exchangers 3 and 4 are connected in parallel between a supply line 5 and a return line 6. A pump for conveying the heating medium is marked 7. The room heat exchanger valves 8 of the room heat exchangers 3 and 4 are adjusted using actuators or motor units 9, and can be limited in each position by stops. The actuators 9 are wirelessly connected or tethered to the central processing unit 10, which receives and processes the data that are acquired by the temperature sensors 11 at the supply point and the temperature sensors 12 at the return point of the individual room heat exchangers, and measured by ambient temperature sensors in the room. The central processor unit ideally also has data relating to the supply temperature on the heating device, the pumping rotation speed and outside temperature, as well as the temperature in the respective rooms or areas to be heated.
For example, room heat exchanger 3 is now defined as the high-priority room heat exchanger, and room heat exchanger 4 is defined as the low-priority room heat exchanger during implementation of the method according to the invention. As already described, this can be the result of oversizing or undersizing, or caused by temporary heat requirements on the part of the user. If the room heat exchangers 3 are for the reasons cited now operated with a low spread, i.e., at a high return temperature, relatively hot heating medium gets into the return line 6, and would lead to an unfavorably high return temperature in the heating device 2. In order to counter this, at least one of the room heat exchangers 4, i.e., a low-priority room heat exchanger, is now operated with a very high spread, so as to convey a certain quantity of cool heating medium into the return line 6, thereby correspondingly lowering the return temperature in the heating device 2.
The spread on the individual room heat exchangers is set by controlling the flow rate, wherein this setting takes place based on the control signals transmitted by the central processing unit 10 to the actuators or motor units 9.
If the user now additionally operates one or more of the room heat exchangers 3 at an even greater heat output, i.e., with an even lower spread, this can be balanced out with the system according to the invention, for example by using the actuators to reduce the flow rate through one or more of the room heat exchangers 4, so that the return to the heating unit 2 can in turn be kept at the desired temperature level.
In a less complicated approach, the removable actuators are only used to set the maximum flow rate through the individual room heat exchangers one time, whereupon the set positions calculated by the central processing unit are limited with mechanical stops, the actuators are again removed, and conventional thermostatic heads are secured.

Claims

1. A method for setting the volumetric flow rate of a heating and/or cooling medium by means of room heat exchangers of a heating or cooling system, in which the target spread of the flow and return temperatures for the individual room heat exchangers is in each case set by limiting the respective room heat exchanger valve in an adjustable and/or fixable manner, characterized in that room heat exchangers of varying priority are defined, wherein a system-specific target spread for high-priority room heat exchangers is used as the basis to allow a lower target spread, and a higher target spread is ensured given low-priority room heat exchangers, and that, during the operation of a high-priority room heat exchanger with a lower spread, the volumetric flow through at least one low-priority room heat exchanger with a higher spread is changed in such a way that a return temperature optimized for the heating device of the heating system is set by mixing the return medium from all room heat exchangers of the heating system.

2. The method according to claim 1, characterized in that the return temperature is set in such a way as to achieve the system-specific target spread.

3. The method according to claim 1, characterized in that the supply and return temperatures of the individual room heat exchangers are acquired and transmitted to a central processing unit, which determines control values for the adjustable and/or fixable limitation of all room heat exchanger valves, and transmits them as a control signal to in particular removable actuators on the room heat exchanger valves.

4. The method according to claim 1, characterized in that the amounts of heat released by the respective room heat exchangers into the return flow are determined to calculate the control values, and the elevated amounts of heat arising on high-priority room heat exchangers due to a low spread are balanced out by setting at least one low-priority room heat exchanger to a high spread.

5. The method according to claim 1, characterized in that a measured value for the outside temperature is drawn upon to calculate the control value for at least one high or low-priority room heat exchanger.

6. The method according to claim 1, characterized in that, given a temporary operational requirement on a room heat exchanger that leads to a decrease in the spread on the room heat exchanger in question, this room heat exchanger is subjected to prioritization, whereupon the volumetric flow rate of heating medium through at least one low-priority room heat exchanger is lowered to balance the return temperature of the heating system.

7. The method according to claim 1, characterized in that, given a temporary operational requirement on a room heat exchanger that leads to a decrease in the spread on the room heat exchanger in question, this room heat exchanger is subjected to prioritization, whereupon the volumetric flow rate of heating medium through at least one low-priority room heat exchanger is raised to balance the return temperature of the heating system.

8. The method according to claim 1, characterized in that a temporary user requirement is issued by inputting a desired value for the ambient temperature, the desired value is sent to the central processing unit, and control values for the room heat exchanger(s) situated in the respective room are calculated in the central processing unit and transmitted as a control signal to the actuators on the room heat exchanger valves.