Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
  • F24D19/00—Details
  • F24D19/10—Arrangement or mounting of control or safety devices
  • F24D19/1006—Arrangement or mounting of control or safety devices for water heating systems
  • F24D19/1066—Arrangement or mounting of control or safety devices for water heating systems for the combination of central heating and domestic hot water
  • F24D19/1069—Arrangement or mounting of control or safety devices for water heating systems for the combination of central heating and domestic hot water regulation in function of the temperature of the domestic hot water
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
  • F24D17/00—Domestic hot-water supply systems
  • F24D17/0078—Recirculation systems

Definitions

• the invention relates to a heating system with a storage vessel with inlet and outlet for a heated fluid and a feed arrangement for a carrier fluid with a feed line in which a valve is arranged, a temperature sensor that determines the temperature of the heated fluid and a control circuit that Valve actuated depending on a deviation in temperature from a specified value. Furthermore, the invention relates to a method for operating a heating system, in which the temperature of a heated fluid is determined and the supply of a heat transfer fluid is controlled in a control circuit as a function of a deviation of this temperature from a preset value.
• the invention is described below with reference to a system for providing hot domestic water. However, it can also be used for other heating systems in which radiators or underfloor heating are to be supplied with the aid of the fluid.
• An example of a heating system that even fulfills both purposes is known from DE 41 42 547 AI.
• the present invention is based on this disclosure. Control of the circulation pump in heating systems is known from DE 24 52 515 AI. Here too, a similar principle is assumed.
• the heat transfer fluid does not necessarily have to be water. It can also be heated air that feeds a room or a room arrangement. The heated fluid gets its heat from the heat transfer fluid.
• the heat transfer fluid can flow through a heat exchanger, on the other side of which the heated fluid is arranged. However, it is also possible for the heat transfer fluid to be heated directly by a heating source, for example a burner, and then to be mixed with the heated fluid.
• the temperature of the heated fluid does not necessarily have to be determined in the storage vessel. It is also possible to determine this temperature in the supply line from the storage vessel to the actual heating circuit. In extreme cases, the storage vessel itself can be relatively small or even be formed by the heating system itself.
• the invention has for its object to achieve a quick response of the heating system with a low mechanical load.
• control circuit has a cutoff frequency detector which detects vibrations in the temperature and reduces a loop gain in the control circuit when the frequency is too high and increases when the frequency is too low.
• the limit frequency detector preferably has a threshold value element and determines the frequency taking into account the output of the threshold value element. In other words, only those vibrations are determined in the frequency determination, the amplitude of which is greater than the threshold value. This creates a corridor around the default value, in which any vibrations can occur, without this being one
• the limit frequency detector therefore only detects vibrations that come out of this corridor.
• the limit frequency detector advantageously determines the oscillation in the temperature indirectly from actuation signals or from movements of the valve.
• the control loop should only operate the valve when it is necessary, in other words when the temperature deviates from the set value by a predetermined amount. If such a deviation has occurred, then this difference is already available. It then manifests itself in the movement of the valve or, which is easier to determine, in a signal which triggers the movement of the valve. So you use existing information in the control loop anyway.
• the object is achieved in a method of the type mentioned at the outset in that a frequency of Vibration of the temperature is determined and the loop gain is reduced if the frequency is too high, and is increased if the frequency is low enough.
• the loop gain is adapted adaptively, i.e. adapted exactly to the respective situation. It can therefore vary from plant to plant and from hour to hour in a plant.
• the frequency is determined only from such deviations that exceed a predetermined difference from the default value.
• a corridor is therefore created around the default value, in which vibrations with any frequency are permitted. These vibrations do not cause excessive stress on the actuators because the actuating movements that occur are very small. Even for a potential user who draws warm water, vibrations within this corridor are barely noticeable and therefore acceptable.
• the frequency is preferably determined indirectly on the basis of movements of the valve and / or control signals for the valve.
• the control signals and the resulting movements of the valve are a direct consequence of deviations in temperature from the specified value.
• the information about the deviation is therefore available and is expressed in relatively easy to understand sig- nalen. These can then be evaluated with relatively little effort.
• the number of changes in direction of the valve movement is advantageously determined in a predetermined period of time and the loop gain is reduced when the number exceeds a maximum value.
• the frequency determination can then be limited to simple counting, the counting of course having to take place in a predetermined time period. If one sets this predetermined period of time, for example, at 5 minutes, then a predetermined number of, for example, 3 to 10 changes of direction of the valve can be permitted without an instability being recognized. If there have been more changes of direction than intended, the system is considered unstable and the loop gain is reduced.
• the counting is interrupted each time it is exceeded and the period begins again. This enables you to reach a stable state even faster. The more unstable the system, the higher the frequency, i.e. the more often the valve changes its direction of movement. If you now make a correction when the criterion is met, you do not have to wait for the entire period to make a correction. This reduces the load on the mechanical components and enables a stable state to be reached much more quickly.
• the loop gain is preferably increased and the default value is changed. So you not only increase the loop gain, but you change the default value by determine whether the system, ie the control loop, then starts to vibrate. In the case of a non-oscillating system, the increase in the loop gain would not automatically lead to an oscillation either, so that one is not sure whether the loop gain fits. By changing the default value, you create a jump that provides the desired information.
• the value of the loop gain used before the increase is preferably used. So you feel your way to the "border". With the same load, one has the information at which loop gain the control loop is still stable and one has the information that the control loop is no longer stable with the next increase. You can then return to the previous loop gain without having to iterate again.
• the loop gain is specified as a function of the load on the system. This is another way of protecting the control system or the parts moving in it from being stressed by excessive movement. If the requirement of the system is small, for example only a little warm water is drawn, then a small controller gain is sufficient. A quick response is also not necessary. The same also applies if, for example, most of the radiator valves in a heating system are throttled during a night setback so that only little heat is "consumed” or dissipated. If, on the other hand, a need arises, for example, hot water is drawn or if the radiator valves are turned on, the system must react quickly. In this case you can switch to a higher loop gain. In this case, where the need is used as an additional criterion, one can skip part of the iterative procedure with several stages.
• the load on the system is preferably determined via the temperature of the heated fluid. This procedure is fast enough and does not require any additional components. If the system is loaded, for example by taking hot water, then the temperature in the storage vessel drops relatively quickly due to the addition of a corresponding amount of cold water. Accordingly, the loop gain can be set up relatively quickly without the risk of vibrations occurring directly. If vibrations occur after a certain time, you can assume that the load on the system has now ended and you can return to the "idle value of the loop gain".
• FIG. 1 is a schematic representation of a heating system for providing hot water
• Fig. 4 corresponding curves to show the increase in loop gain
• Fig. 5 is a schematic representation for explaining a system protection function.
• Fig. 1 shows schematically a heating system 1 for providing hot domestic water that can be removed by taps 2 or other taps.
• the taps 2 hang on a ring line 3 with a feed line 4 and a return line 5, which are connected to a storage vessel 6, for example a boiler.
• a circulation pump 7 is arranged in the ring line 3, which ensures that warm water is available at the taps 2 without any significant delays.
• the storage vessel 6 is designed as a heat exchanger, on the primary side 8 of which a supply line 9 and a drain line 10 are provided for a heat transfer fluid or, more generally, a heat transfer fluid.
• the heat transfer fluid can be water that is already switched on by a heating boiler. But it can also be a liquid that is used in a district heating system for heat transfer. The specific design of the heating of the heat transfer fluid does not play a major role.
• a valve 11 is arranged in the supply line 9 and can be opened or closed by means of a motor 12.
• the motor 12 is designed, for example, as a stepper motor, so that different opening voltage positions of the valve 11 can be adjusted.
• a temperature sensor 13 is arranged on the flow line 4 and determines the temperature of the warm water in the flow line 4.
• the temperature sensor 13 is connected to a control device 14, which in turn controls the motor 12.
• the control device 14 has an input 15 for presetting a preset value for the temperature in the storage vessel 6. This default value is also referred to as the "setpoint".
• control device 14 actuates the motor 12, which opens the valve 11.
• the above-mentioned parts thus together form a control circuit 18.
• the control device 14 forms the actual “controller” or a static one
• Gain Xp has. The reciprocal of this static gain Xp is called the loop gain V.
• control device 14 The detailed structure of the control device 14 is shown in FIG.
• control device 14 shown schematically.
• the inputs and outputs of the control device 14 are provided with the reference numerals of the elements to which the control device 14 in FIG. 1 is connected.
• the control device 14 initially has a differential amplifier 23, to which the predetermined value is applied the input 15 and the actual value of the temperature from the temperature sensor 13 is supplied. Depending on the difference between these two values, a corresponding adjustment signal for the motor 12 is generated. However, the static gain of this differential amplifier 23 is variable.
• a cut-off frequency detector 19 is used for the change. The cut-off frequency detector 19 first receives the same signals as the motor 12 receives. He also receives the actual temperature and the target temperature. These signals or values are fed to a processing device 20 which, as will be explained further below, generates a pulse under predetermined conditions and, among other things, has a threshold value element. The pulses are fed to a counter 21.
• the counter 21 is connected to a timer 22 which indicates to the counter 21 the beginning and the end of a predetermined period of time.
• the output of the counter 21 is connected to a reset input of the timer 22.
• the output of the counter 21 is connected to the differential amplifier 23, more precisely to an input at which the gain factor, ie the static gain, can be adjusted.
• control circuit 18 The operation of the control circuit 18 will now be described with reference to FIG. 3.
• FIG. 3a shows a curve St , ie the temperature curve in the flow line 4.
• the default value T SET ie the setpoint of the temperature
• T SET ie the setpoint of the temperature
• Nz is shown on both sides of the setpoint T SET .
• the differential amplifier 23 generates pulses for actuating the motor 12 at predetermined time intervals, which are shown in FIG. 3b.
• the motor is operated in one direction (on +). If the situation is reversed, the motor is operated in the other direction (on-).
• This representation is of course only an example. Other ways of adjusting the valve 11 are of course also possible.
• an adjustment direction course is derived from the individual pulses that are shown in FIG. 3b, which is shown in FIG. 3c.
• 3d now shows the initial value of the counter 21, which is increased by the value 1 with each change of direction.
• the timer 22 now specifies a predetermined time period, which is also entered in FIG. 3a.
• the time periods ZI, Z2, Z3 are initially basically all of the same length.
• the amplification factor Xp of the differential amplifier 23 is first increased and thus the loop gain V is reduced. At the same time, the counter 21 is reset to zero and the
• Timer 22 reset. Accordingly, the second counting period Z2 begins before the first counting period ZI has completely expired.
• 3e shows that the loop gain V is reduced each time the counter 21 has reached a predetermined count value within a counting period z, in the present case the value 3. It can be seen that two corrections are necessary before the loop gain V has become so small that the actual temperature T £ ⁇ t is still oscillating, but the amplitude of this oscillation is mostly still within the neutral zone. In this case, only two changes of direction occurred within the counting period Z3. Otherwise, the actual temperature i st met the condition
• T SET - 0.5 Nz ⁇ T is ⁇ 0.5 Nz + T SET .
• the loop gain V corresponds to the reciprocal of the static gain Xp of the differential amplifier 23.
• the cutoff frequency detector 19 After the increase in the static gain Xp, which corresponds to a decrease in the loop gain V, the cutoff frequency detector 19 is started. If the cutoff frequency detector detects an instability, for example a number of 3 or more changes in direction within a counting period ZI, Z2,... Zn, then the static gain Xp is increased once more, as described above. If the count of the direction changes does not reach the critical value, it is assumed that a stable state has been reached and this static gain is maintained. Basically, the process is divided into two phases. In the first phase it is determined whether there are "critical" vibrations and at the output of the first phase the loop gain is changed according to the result. In the second phase, stability is monitored.
• the first phase it is determined whether there are "critical" vibrations and at the output of the first phase the loop gain is changed according to the result.
• stability In the second phase, stability is monitored.
• Fig. 4 shows the procedure for increasing the loop gain.
• the static gain Xp is first reduced, for example by setting
• ⁇ can be the same value as ⁇ , but it will usually be a different value.
• TsET ⁇ SET + ⁇ sp.
• ⁇ sp - ⁇ sp.
• the change in the setpoint T SET causes a jump that should trigger an oscillation. Without such an oscillation, instability could not be determined even by changing the loop gain V.
• a delay time ⁇ t is waited for. Then the cut-off frequency detector 19 is started. If and as long as the limit frequency detector determines a stable behavior of the control circuit 18, this procedure is repeated, ie the loop gain V is increased.
• the value of the loop gain V is thus reset to the value that allowed the last stable state.
• loop gain V shows a further possibility of how the loop gain V can be changed. So that can implement a system protection function in which one can also avoid vibrations at low loads near idling.
• the high loop gain V which is referred to as VI in FIG. 5, is in operation when the heating system 1 is under normal load.
• This loop reinforcement VI can have been found, for example, by the automatic adjustment procedure described above. Means, not shown, can be provided to store this gain factor.
• the small loop gain V2 is used at idle.
• the cut-off frequency detector 19 is now used to determine when consumption has ended.
• the high loop gain VI leads to an oscillation with too large an amplitude and too high frequency. If such a vibration is detected after a previous increase in the loop gain, the gain is switched from the high value VI to the lower value V2, after which the system stabilizes again.
• the change in temperature that occurs during the change is used to determine the change from idling to consumption. This is the case, for example, at time t2 in FIG. 5.
• the removal takes place between times t2 and t3.
• a burden in In the present case a water withdrawal is determined when the actual temperature falls by a value Dz below the target temperature T SET .
• the loop gain is increased to the value VI. This gives the controller the necessary speed for normal consumption.
• the removal is complete at time t3. Since the loop gain is too high, an oscillation now takes place in the counting period Z2. This is recognized by the cutoff frequency detector and the loop gain is reset to the value V2 at time t4.
• the loop gain V2 in turn may have been found by a corresponding iteration when increasing the loop gain.

Landscapes

• Engineering & Computer Science (AREA)
• Thermal Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Control Of Temperature (AREA)
• Heating, Cooling, Or Curing Plastics Or The Like In General (AREA)
• Steam Or Hot-Water Central Heating Systems (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Resistance Heating (AREA)
• Electrodes For Cathode-Ray Tubes (AREA)
• Mounting, Exchange, And Manufacturing Of Dies (AREA)
• Control Of High-Frequency Heating Circuits (AREA)
• Control Of Resistance Heating (AREA)
• Vehicle Body Suspensions (AREA)
• General Induction Heating (AREA)

Priority Applications (10)

Applications Claiming Priority (2)

Publications (2)

Family

ID=7900864

Family Applications (1)

Country Status (15)

Cited By (1)

Families Citing this family (1)

Citations (1)

Family Cites Families (1)

• 1999
  • 1999-03-15 DE DE19911237A patent/DE19911237C2/de not_active Expired - Lifetime
• 2000
  • 2000-03-10 RU RU2001124831/28A patent/RU2240592C2/ru active
  • 2000-03-10 PL PL00350239A patent/PL194443B1/pl unknown
  • 2000-03-10 CZ CZ20013296A patent/CZ20013296A3/cs unknown
  • 2000-03-10 EE EEP200100427A patent/EE200100427A/xx unknown
  • 2000-03-10 SK SK1275-2001A patent/SK12752001A3/sk unknown
  • 2000-03-10 EP EP00909063A patent/EP1161711B1/de not_active Expired - Lifetime
  • 2000-03-10 DK DK00909063T patent/DK1161711T3/da active
  • 2000-03-10 WO PCT/DK2000/000098 patent/WO2000055545A2/de active IP Right Grant
  • 2000-03-10 DE DE50000314T patent/DE50000314D1/de not_active Expired - Lifetime
  • 2000-03-10 YU YU60901A patent/YU60901A/sh unknown
  • 2000-03-10 HU HU0200360A patent/HUP0200360A2/hu unknown
  • 2000-03-10 AT AT00909063T patent/ATE221220T1/de not_active IP Right Cessation
  • 2000-03-10 AU AU31473/00A patent/AU3147300A/en not_active Abandoned
  • 2000-10-03 UA UA2001075373A patent/UA57871C2/uk unknown
• 2001
  • 2001-08-15 BG BG105819A patent/BG105819A/xx unknown

Patent Citations (1)

Also Published As

Similar Documents

Legal Events