DE2521008B2 - METHOD OF COUNTING HEAT QUANTITIES AND HEAT QUANTITY COUNTERS - Google Patents

Description

The invention relates to a method for counting amounts of heat and a heat meter to carry out this procedure.

In most known heat meters, apart from the temperature difference between the pre- and Return of the medium emitting the heat and the amount of this medium, for example hot water, Steam, heated air or the like measured. To determine the amount of heat consumed, then the product from; these two measured quantities formed. the

Product formation of these two measurands takes place 'For example via differential gears or other similar mechanical or electrical devices.

Mauiteilig of these known devices is Met others their high construction costs and, rfbrderiiche frequent maintenance so that they could find only limited application.
Also known are heat meters which are fastened between the ribs of radiators in, for example, centrally heated apartments and which contain a measuring tube filled with a liquid. However, these devices based on the evaporation of the liquid are extremely imprecise.

It is also a continuous display meter the amount of heat released between the flow and return is known, at which this is done without measurement the amount of the heat-releasing medium with the help of in thermally conductive bridges between the flow and return thermocouples used and possibly further additional thermocouples takes place in the forward and backward movement Characteristic curves for the formation of a linear characteristic curve from them required, because of the in the measurement more detailed. Dependence of some perceived temperatures on the flow velocity of the medium a relatively narrow flow velocity range and also requires constant heat transfer between the flow medium and the metallic contact surfaces in the flow medium the heat-conducting bridges, which is often not achievable, for example in heating systems because of the polluted water circulating. For the counting of the amount of heat a Integrator for integrating the measured value over time must also be available.

It is the object of the invention to provide a method for counting amounts of heat that is simple and is reliable and measures reasonably accurately.

This object is achieved according to the invention by the method specified in claim 1.

This method is characterized by its simplicity and reliability and enables high measurement accuracy.

According to the invention, a heat meter according to claim 2 is required to carry out this method intended.

This heat meter is structurally simple to produce, is operationally reliable and robust, and has a high Measurement accuracy, is easy to adjust and is also suitable for circulating, heat-emitting media that are in the Pollute over time, like heating water, and requires little maintenance. Because its regulating device If a two-point controller is expedient, particularly simple and inexpensive controllers can also be used come.

The cross-sections of the bypasses are expediently much smaller than the supply and return lines.

In a preferred embodiment it is provided that means for rapidly mixing the in the Mixing chamber inflowing medium are provided with the medium located in the mixing chamber. This can be done in a variety of ways, for example by means of one arranged outside the mixing chamber Circulation pump that constantly sucks the medium out of the mixing chamber and returns it to it. Or a rotating vane can be provided in the mixing chamber, or others can also be used

Measures to accelerate the mixing process can be provided with the aim of reducing the temperature in the Constantly equalize the mixing chamber. In many cases, however, it is sufficient to start the mixing process in not forcibly flowing into the mixing chamber.

In order to increase the flow rates of the bypasses and also in the most precise possible manner as a function of to bring the flow rates in the flow and return, ka. ^ n be provided that the flow and Return lines have constrictions in their areas arranged parallel to the relevant bypass. The constriction can advantageously be designed as a diaphragm. It can also be beneficial to use the constriction as a nozzle to train.

To get an immediate reading of the amount of heat counted, the number of switchings can be made or a counting device that visibly displays a certain fraction of this number, as is also the case with electricity and gas meters in households. It is usually sufficient if only a certain fraction of the switchings that have occurred is displayed.

The invention is described in more detail with reference to the exemplary embodiments shown in the drawing and explained. It shows

F i g. 1 a heat meter according to a first embodiment of the invention,

FIG. 2 is a diagram showing an example of the temporal change in the medium temperature in the mixing chamber of the device according to FIG. 1 to the respective setpoint shows and

3a and 3b each show a setpoint / actual temperature comparison device according to a second exemplary embodiment of the invention.

The in F i g. 1 is installed, for example, in a hot water heating system of a building, between the flow line 12 leading to a heat consumer 14 and the return line 13 in order to measure and count the amount of heat given off. Such consumers can be, for example, the radiators of an apartment, a floor, several floors, a house or the like. An amount of heat ρ · time unit Qv flows to the consumer 14, and a remaining residual amount of heat per time unit Qr flows from the consumer 14 through the return 13, for example to a boiler (not shown), in which the War nwassei is reheated to its flow temperature. The difference between Qv and Qf corresponds to the amount of heat Q emitted per unit of time . This amount of heat Q wire emitted is measured and integrated, ie counted, over a longer time interval, for example a heating period.

According to FIG. 1, a mixing chamber 16 is connected to the flow 12 and the return 13 by means of lines 1 ' connected to 20, which has a certain volume. In lines 17 to 20, the cross-sections of which are significant smaller than the cross sections of the lines 12 and i; are, shut-off valves 21 to 24 are arranged. Both in the flow 12 and in the return 13 is in respective area between the connections of the lines 17, 118 and 19, 20 respectively a diaphragm 26 and 2 respectively used, which a narrowing of the flow 1: or return 13 for the purpose of generating de Flow rate dependent pressure differences cause zen, so that when the valves 21, 22 de Flow bypasses 28 or the valves 23, 24 de return bypasses 29 are open, each one of de

the respective pressure difference and thus the amount of water flowing in the supply or return flow, depending on the significantly smaller amount of water flowing through the relevant bypass.

A temperature sensor 31 and 32 is installed in the flow 12 and in the return 13. The two temperature sensors 31 and 32 are connected to a first averaging device 33, which ^{feeds the prevailing average temperature 1} JTw as a setpoint value to a two-point controller 34, with

'wed 2

is. In the mixing chamber 16 are in this embodiment for the purpose of the most accurate possible determination of the respective mean temperature (mixed temperature) temperature sensors at four points apart 36 to 39 arranged, the measured variables of which are fed to a second averaging unit 41, which The arithmetic mean is formed from these four temperature values and the two-point controller is used as the actual value 34 feeds. It goes without saying that in some cases it can also be useful in the mixing chamber 16 more or less temperature sensors, possibly a single temperature sensor, to be provided, too can be arranged in other places than shown. The mixing in the mixing chamber 16 can compulsorily, for example with the help of a circulating pump not shown or a driven one Impeller done or it can only be provided self-mixing.

The two-point controller 34 is connected to the valves 21, 22 in the flow bypass 28 via a first electrical control line 42 and to the valves 23, 24 in the return bypass 29 via a second control line 43. The two valves 21, 22 and 23, 24 of the bypass 28 and 29 are each opened and closed simultaneously. In this embodiment, the valves 21, 22 are always opened at the same time when the valves 23, 24 are closed and vice versa, so that the mixing chamber is alternately flowed through by flow or return liquid. The frequency at which the two bypasses 28, 29 are opened and closed by means of the valves 21 to 24 is determined by the two-point controller 34 and is proportional to the respective temporal amount of heat Q emitted, as will be shown mathematically below.

The individual symbols indicate the following:

Qv, Qr = the amount of heat flowing through the flow or return flow per unit of time,

Q _n , = temporal change in the amount of heat in the Mixing chamber,

M ■■ = the amount of water flowing through per unit of time,

Cv, Cr and C _n , - the specific heat of the

Water in flow, return or mixing chamber,

ϋ · ν, ür and O ^ _n , = the water temperature in the flow or return or average temperature in the

Mixing chamber,

ρ / η = the density of the water in the mixing chamber and

V · = - the volume of the mixing chamber.

Hs pilt:

Q ₁ MC, - H ₁

Qr = Af · C _R · I) _H

Q, "=

dl

(3a)

Q _n = -b- Mic _m I) _n ,

(3

Equations (3a) and (3b) apply, since the bypasses 28 and 29 allow the amount of water to flow per unit of time a · Mb or b · M, where a and / are constant.

When inflow of the component stream a ■ M from the IS flow 12 into the mixing chamber 16 there is a temporal change of the average temperature in the mixing chamber 16, if it is ensured that the effluent from the mixing chamber water temperature · &"has, of :

u ■ M

d;

C _1n

""

and when the partial flow rate flows from the return line 13 into the mixing chamber 16, one from

d I) _n ,
d /

h ■ M

C "

■ V

(C _K 'V- C _n -I) J. (5)

It is now assumed for the calculation example that these two changes over time of the middle Temperature in the mixing chamber 16 under the same conditions are each equal in terms of amount. Puts .15 if equations (4) and (5) are the same, after forming:

" ₌

(a I h)

If you insert equation (6) into equations (4) or (5), you get after transformation:

J K

German

h ■ M

■ I '■ (i / 4 h)

(c,

and

d //, "
df

a- h- M

V- la + h)

R "K>

If one carries these two equations (7) and (8) for the case in the in FIG. 2 shows that the two-point controller opens valves 23,24 at temperatures around * + ' / 2Δϋ · _ζ and closes valves 21, 22 and at # _mj -

the valves 21,22 opens

and the valves 23, 24 closes, then, taking into account the alternating opening and closing of the two bypasses 28 and 29, the results shown in FIG. 2 curve shown. If # _m ., Changes, the displayed area Δ &, moves up and down accordingly.

From r = 0 to f = ^ only the bypass 28 is open,

fts resulting in a temperature rise in the mixing chamber 16

causes and it is during the time from ^ to T only the

Bypass 29 opened, resulting in a decrease in the

mean temperature, i.e. the actual value in the mixing chamber. Δ $, is the temperature difference set on the controller based on the respective mean value ¹ Ov, formed in element 33, when the controller switches over valves 21-24 when it is reached. Aft? is taken appropriately, for example, Δϋι can be less than I ⁰ C.
Integrate equation (7) over time from 0

until ^ it results:

I i). =

a + h

If one sets the frequency f for 1 / T, one obtains by transforming equation (9).

from M- (C _1. -O _1. -C ₁

^(l0)

If one equates the two factors a and b, one obtains:

(10a)

From these equations (10) and (10a) it can be seen that the frequency f of the two-point controller 34 is proportional to the change in the amount of heat Q _{m over time} in the mixing chamber 16 and thus the amount of heat Q emitted per unit of time at the consumer and thus a measure of the amount of heat consumed is, so that by means of a counter 44 counting the switchings of the valves 21-24 effected by the two-position controller, the amount of heat given off in the relevant period is counted. The counter 44 can also be arranged spatially far away if it is electrically controlled.

The above calculation was carried out under particularly simple assumptions that can also be realized structurally, but it goes without saying that measures deviating from this can also be taken without departing from the concept of the invention, for example the factors a, b and the diaphragms 26, 27 can be made differently. Or one does not find Δ & Ζ constant, but, for example, proportionally depending on # _m s. With each switchover process depending on # _ms, the counter is incremented differently, for example different numbers of counting pulses are sent to it, etc.

Also, Δ θ · · _ζ be made for the purpose, depending on ft ™, _n to the temperature-dependent changes of C, and Q _n, by changing Au _x in their effect to compensate the measurement result.

If necessary, ΔΦ _{Ζ can} also be made dependent on one or more other variables, with the aim of increasing the measurement accuracy.

The above calculations were valid for the case that the water _{flows out of the mixing chamber at the temperature # m.} The invention is not limited to this

For example, the temperature of the respective flowing water in the pipes 18 and 20 to measure and werlcs take this into account by appropriate modification of Δϋ · _ζ or by changing the count provided in the subsequent switching on deviation from ¹ O- ". If necessary, you can continuously make further corrections depending on at least one variable to be measured, be it by changing Aft? or by influencing the count output in the wake of the subsequent switchover, which influences the count of the counter 44 directly or after intermediate addition in an intermediate counter (not shown). Since the heat quantity count always takes place over very long periods of time

ίο takes place, for example over a heating period or at least over a month, an intermediate counter can easily be provided which only ever the counter 44

is advanced.

Instead of providing a constant count value or a count value dependent on at least one measured variable for counting the amount of heat for each bypass switchover made by the controller, as described above, in many cases it can also be expediently provided that only the switchovers on one of the two Limits of Aft trigger counting values to be added to the already counted amount of heat for the amount of heat to be counted, as this also enables the amount of heat to be counted over a longer period of time with the same accuracy.

A counter value is a quantity that increases the content of a counter or intermediate counter, For example, a count from one, several or many impulses can be mechanical steps or the like exist and represent or symbolize an unencrypted or encrypted number etc.

According to a second exemplary embodiment of the present invention, the setpoint value and the actual value of the mean temperature are not fed separately to the two-point controller 34 via the mean value formers 33 and 41 , but it is instead, according to FIGS. 3a and 3b an electrical voltage u is fed to the two-point controller 34 via an amplifier 49, which voltage is proportional to the sum of the temperatures in the flow 12 and in the return 13 minus the temperature in the mixing chamber 16.

Based on the F i g. 3a the basic circuit diagram is explained. A welding point V of a first thermocouple 46 is arranged at a suitable location on the forecourt 12 and the welding location R of a second thermocouple 47 is arranged at a suitable location on the return 13. Dung steep connects m of the thermocouples 46 and 47 are at appropriate for averaging points in d <r mixing chamber 16 arranged Welds V, R and m are thus the temperatures & _v, # λ # _m of the water in the flow pipe 12, the return 13 or exposed in the mixing chamber 16 The two free connection points m of the two thermocouples 46 and 47 are connected via connecting lines to an electrical operational amplifier 49, which is connected to the two-point controller 34. At the input of the

Amplifier 49 is thus a thermal voltage u, for which, assuming that it is a linear function of the temperature difference over a sufficiently large range:

Ar = constant proportionality factor. The two-point controller 34 now has the task of alternately opening and closing the valves 21 and

709524/114

22 or the valves 23 and 24 to regulate the mean temperature $ _m in the mixing chamber 16 so that the voltage at the amplifier 49 fluctuates between predetermined limits corresponding to Δϋ · _ζ , where u = 0 corresponds to the mean value of the voltage change at the amplifier 49- For u = 0, the relationship results from equation (11)

'Vv

(12)

Thus, the condition is met that the mean temperature & ■ "in the mixing chamber 16 is equal to the arithmetic mean from the intake temperature # the return temperature is around #r; The setpoint and actual value are then the same.

As in FIG. The first exemplary embodiment shown in FIG. 1 is the number of switchings of the bypasses 28,29, which the two-position controller 34 executes, a measure for

10

the temporal amount of heat Q released in consumer 14.

If the temperature distribution in the mixing chamber K is not uniform, which can be the case, for example, with self-mixing, then according to FIG. 31 use a thermal battery 48 which has several, in the exemplary embodiment three first thermocouples 46, 46 '46 "and three second thermocouples 47, 47', 47 'each, which have a correspondingly larger number of welding points V or R and m . Di" welding points m can be arranged evenly distributed in the mixing chamber If, which is indicated schematically in FIG. 3t.

For reasons of corrosion resistance and the temperature linearity of the thermal voltage u, nickel-chromium-nickel thermocouples can preferably be used for the thermocouples 46, 46 ', 46 "and 47, 47', 47 '.

For this purpose 2 sheets of drawings

Claims (13)

Patent claims: 1. Method for counting amounts of heat in heating, cooling or air conditioning systems, in which the The temperature difference between the flow and return of the medium emitting the heat is sensed, characterized in that flow medium and return medium alternately through a Flow bypass or return bypass passed through be, these bypass media correspondingly alternating a common mixing space flow through that the temperature deviation of the mixing chamber temperature from a mean temperature felt between the respective flow and return temperature and when a predetermined one is reached positive temperature deviation from the flow medium flowing through the mixing chamber switched to its flow through return medium and the one that takes place afterwards Reaching a predetermined negative temperature deviation again on flow through the mixing space is switched by the flow medium and that in the wake of the switchovers at at least one of the two temperature deviation limits Counting values for counting the amount of heat to be determined triggered and with each other can be summed up. 2. Heat meter for heating, cooling or air conditioning devices or systems, with a device to measure the temperature difference between the flow and return of the heat emitting Medium for carrying out the method according to claim Ί, characterized in that one discontinuous control device (34) is provided which has a bypass (28) of the flow line (12) of the Medium and a bypass (29) of the return line (13) alternately opens and closes, the two bypasses (28, 29) lead through a common mixing chamber (16) that temperature sensor (31,32,33) for generating a variable, a mean temperature between the respective pre- and Return temperature of the medium corresponding setpoint provided for the control device are that at least one temperature sensor (36 to 39) for sensing the measured in the mixing chamber Mixing temperature is provided as an actual value for the control device that the control device (34) is coupled to valves (21-24), which each time a predetermined positive Temperature deviation from the setpoint opens the bypass (29) lower temperature and the closing of the bypass (28) causes a higher temperature and when a specified negative temperature deviation from the setpoint the opening of the bypass higher Temperature and the closing of the bypass causes lower temperature and that the Control device (34) is connected to a counting device (44) so that each switchover of the bypasses at least one of the two temperature deviation limits to be added count values for the Counting the amount of heat to be determined triggers. 3. Heat meter according to claim 2, characterized in that the cross sections of the bypasses f> 5 (28, 29) are much smaller than those of the supply and return lines (12,13). 4. wärmemenKeiUähler according to claim 2 or 3, characterized in that the two bypasses (28, 29) have the same flow resistance. 5. Heat meter according to one of claims 2 to 4, characterized in that the pre and return lines (12, 13) in their areas parallel to the relevant bypass (28, 29) Have constrictions (26,27). 6. Heat meter according to one of claims 2 to 5, characterized in that the Setpoint from the arithmetic mean of the medium temperatures in the supply and return lines (12, 13) is formed 7. heat meter according to one of claims 2 to 6, characterized in that the Control device (34) on the density and / or the specific heat of the medium used as temperature-dependent variable isL 8. heat meter according to one of claims 2 to 7, characterized in that means for rapid mixing of the medium flowing into the mixing chamber with that in the mixing chamber located medium are provided. 9. Heat meter according to one of claims 2 to 8, characterized in that an even number of thermocouples (46, 46 ', 46 "; 47, 47', 47") in series for immediate sensing of the difference between Soüwert and actual value of the mixed temperature are connected that half the number of connection points (V) of the two wires of the thermocouples of the temperature of the flow (12), the remaining connection points (R) of the two wires of the thermocouples of the temperature of the return (13) and the connection points influencing the thermal voltages ( m) the thermocouples and the connection points of the row of thermocouples are exposed to the temperature of the mixing chamber (16). 10. Heat meter according to claim 9, characterized in that nickel-chrome Niekel thermocouples are provided. 11. Heat meter according to one of claims 7 to 10, characterized in that the positive and negative temperature deviation from the setpoint value can be changed automatically in a predetermined way as a function of the setpoint value 12. Heat meter according to one of the claims 2 to 11, characterized in that only effected by the controller for each next but one Switching the bypasses a count is added to the content of the counting device (44). 13. Heat meter according to one of the claims 2 to 12, characterized in that all count values triggered in the wake of switchings are the same size.