SI9400457A - Measuring device for quantity of heat emitting from radiator - Google Patents

Abstract

The thermometer probes (7,8) communicate with the radiator (1) in a heat conducting connection. The amount of heat radiated from the radiator is computed from the measurement values of the two thermometer probes (7,8). The thermometer probes (7,8) are fitted in direct contact with the surface of the radiator. A curve is extrapolated from the probe values using a computer, which corresponds to the expected temp. profile of the radiator (1), and from which the amount of heat radiated from the radiator is computed.

Description

(57) The apparatus described for measuring the heat emitted by the heater through which the heating medium flows, according to the invention provides for at least two temperature sensors in a single frame, which are in direct contact with the surface of the heater. From the measured values of the temperature sensors, a curve corresponding to the expected temperature profile of the heater is computationally extrapolated. This results in high measurement accuracy, which is related to the compact structure of the device, uniquely for different types of heaters. If at least three sensors are provided, the resulting redundancy can be used to increase measurement reliability as an anti-tamper and so on.

Sl 9400457 A

Techem AG

A device for measuring the heat emitted by a heater

The invention relates to an apparatus for measuring the heat emitted by a heater through which a heating medium flows through the inlet port and the return port, provided that at least two temperature sensors spaced apart from each other are connected in a vertical manner to the heater. heat transfer, and the heat emitted by the heating circuit is calculated on the basis of their measurement values using the evaluation circuit.

The heaters on which the measurement is to be taken are physically a liquid-air heat exchanger, so that basically three paths are available for determining the heat output or the heat exchanger. power heater:

a) Enthalpy balance on the heating agent side

The enthalpy balance on the heat transfer medium gives, with a reasonable default of medium heat capacity c _p at constant pressure for the heating medium, the following equation:

Q = c. m. (t -1).

P \ V Γ '

By measuring the flow rate m of the heating medium and the flow or flow rate. return temperatures t _y oz. t can thus precisely determine the thermal power Q of the heater. This nozzle leads to a known process for a heat meter.

b) Enthalpy balance on the air side

The enthalpy balance on the air side does not lead to any practically useful process, since air is not flow-restricted and thus the definition or measurement of mass flows or pressures is generally not feasible.

c) Heat-exchange properties of the heater

Determining the power of the heater without directly determining the volume flows presupposes the determination or defaults on the heat-exchange properties of the heater on which the measurements are made.

A known nozzle is the calculation of the heater power from the standard heat output by the heater characteristic, namely by the power law:

where At is the temperature excess of the heating surface:

At = t. . -1. _ft heiz luft

Qn = standard heat output, Atn = standard temperature excess.

The heater characteristic describes well the conditions at (relative to the standard state) constant mass flow with different flow temperatures, that is, at relative temperature ranges that do not deviate significantly from the standard state.

In this area, the temperature flow across the heater is linear, so that the active temperature of the heating surface corresponds to the arithmetic mean of the temperature at the inlet and return ports.

Known electronic cost distributors for single sensor measurements measure the temperature of the heating surface with a single temperature sensor and calculate the heat output by default giving the room temperature equal to ί _χ = 20 ° C.

Measuring deviations arising from the deviant actual temperature of the room, the electronic distribution of heating expenses with two temperature sensors for measuring temperature _ΐ χ air in the room, preparing for two sensors escape.

However, with a stronger attenuation of the flow of the heating medium and with a larger temperature range, which originates below, the temperature course deviates from the linear distribution. Then one characteristic of the heater enters several characteristics of the heater with the flow of the heating medium as a parameter.

With known distributors of heating costs, there is a systematic measurement deviation here, since the flow of the heating medium or the system cannot be captured. temperature distribution takes place.

An example of preparation with two sensors is shown in published patent application DE 31 23 336 Al. Both temperature sensors are mounted there on the heater at the height of the supply line or. return line, apparently without any special cover. Due to the large distance of the two sensors from each other, it would also not be feasible to install the two sensors in one common housing, which should, however, extend over the entire height of the heater. However, the installation of the sensors is complicated because the two sensors must be attached separately from each other. They also need to be connected to a common unit of evaluation through their own lines, which is complex and complex. It should also be borne in mind that in one house, as a rule, many heaters must be properly equipped, at a low cost.

From Elektronik und Maschinenbau, 97, no. 3 (1980), p. 125 - 128, the idea is to describe the temperature of the heater as a function of the temperature range between the inlet line and the return line.

The field of temperature distribution characteristics can then be translated into one characteristic in a familiar way if a logarithmic temperature excess is inserted into the power law instead of the arithmetic one.

4t _log = tv - tr_.

This corresponds to the link given by Grashoff for the mean temperature difference in heat exchangers and is also empirically confirmed for heaters - compare DIN / 4703.

This nozzle uses the familiar three-sensor procedure. By measuring the flow temperature, return line and room temperature, the logarithmic temperature excess of the heater and the heat delivered at all mass flows and temperature ranges are calculated.

When preparing for the three sensors, the drawback is in the complex structure with temperature sensors that must be installed at a great distance from each other and at the appropriate cost in connection with the cables. The temperature measuring points of the heating means are determined at the vertical height of the inlet connection and the return connection, so that a uniform and compact structure of the preparation for the different heaters is not feasible - compare the previously mentioned published patent application DE 31 23 336 Al. Another disadvantage is the strong dependence of measurement quality on the accuracy of measurement in the air in the room and the resulting sources of error and the risk of tampering.

Accordingly, it is an object of the invention to propose a process whereby, with a small installation effort, it is possible to capture the power of the heater at all operating conditions with high precision and insensitivity at a low assembly effort by means of a compactly built and for different heater single unit heating cost. external influences.

According to the invention, the task is solved in the preparation with the features of the introductory part of claim 1, in that the vertical distance of the two temperature sensors housed in the common housing is significantly smaller than the vertical distance of the inlet line and return line.

Thus, according to the invention, it is possible to extrapolate from the measured values a curve corresponding to the expected temperature profile of the heater and from which the heat emitted by the heater is calculated, with the help of only two sensors installed in the common casing - preparation for two sensors , both sensors being in direct contact with the surface of the heater under consideration.

With the help of these measured values, it can then be deduced from the whole course of the temperature of the heating surface, so that all operating conditions can be captured equally.

The process of the invention takes advantage of the fact that the operating condition of the heater is precisely determined by a certain course of surface temperature. If, by appropriate measuring procedure, considering the temperature field on the surface, the power of the heater can be accurately determined without direct inference to the status of the heating medium.

The measures of the invention thus avoid the labor-demanding connection of the three temperature sensors to the wires in the previously described known preparation for the three sensors. In addition, it is no longer necessary to insert the temperature sensor each time into the supply line or. into the return line, which is just as demanding in hardware and work as was the case with the prior art. Alternatively, the temperature sensor can be adjusted directly to the surface of the heater at any location, and a much smaller distance between the temperature sensors can be predicted, as in the prior art corresponds to the distance between the supply line and the return line. Even at a shorter distance, the curve can be extrapolated from the measurement values with sufficient accuracy. For this reason, all temperature sensors in direct contact with the surface of the heater can be installed in a single enclosure.

An important embodiment of the process of the invention is that at least three temperature sensors are provided. If the third temperature sensor is also brought into direct contact with the surface of the heater under consideration, then the extrapolation of the corresponding curve is more accurate and thus the result of the measurement. Alternatively, the third temperature sensor can also be designed as an air sensor, thereby obtaining redundancy, which can be e.g. used to control events. Thus, a fourth sensor can be provided whereby three sensors are mounted on the heater and the fourth is implemented as a temperature sensor that measures the temperature in the room, and so on.

As a third parameter, for two temperature sensors per heater, the height of both sensors per heater can also be used.

The invention is further explained in more detail by way of an embodiment which gives rise to further essential features. The figure schematically shows a view of the heater by means of temperature profiles and by the installation of a device according to the invention with two sensors.

The considerations that are relevant to the present invention should first be explained.

The following distributions follow from the temperature distribution at the heater.

The temperature is always strictly monotonous from the supply line to the return line. With standard mass flow and temperature changes in the supply line, linear trajectories occur with a reduced slope at supply line temperatures that become lower.

With a constant constant flow temperature and a change in the mass flow, with a decrease in the mass flow, the slope is initially higher, with increasing damping, then with non-linear runs, where the temperature gradient towards the return line becomes smaller.

Each operating state of the heater thus corresponds to a well-defined course of the temperature in the heater. If this is given, the thermal power is also determined.

Since the operating condition of the heater is related to a certain temperature distribution, ideally when the temperature distribution across the surface is known exactly, the room temperature is not required for the calculation because the active temperature excess is represented by the flow. This redundancy can be exploited in various ways.

The figure schematically shows a view of heater 1. This has a supply line 2, after which hot water at e.g. 90 ° C flows into the heater in the direction of the arrow, just like the return line 3, after which the water leaves the heater in the direction of the arrow and cooled, e.g. to a temperature of 70 ° C.

Above the heater is applied the temperature t, which is expressed in ° C, and to the right next to the heater its height H, which is expressed as a percentage.

It has already been mentioned that, when the heating medium is not flowing, a flat temperature profile is presented, which is represented here by curve 4, which explains that the temperature determined in the upper region of the heater, i.e. near 100% height, and e.g. is 90 ° C, decreasing linearly to the temperature in the lower region of the heater, i.e. at an altitude of H close to 0%, in this case at 70 ° C.

However, the damping flow of the heating medium results in a belly curve 5, which shows that the temperature drop is no longer linear, but in the upper region the temperature drop is very strong and then becomes slower.

The course of the considered curve, which is present at the current operating conditions, is now measured according to the invention by means of the measuring device indicated at position 6.

It has at least two temperature sensors 7, 8 and preferably three temperature sensors.

A further temperature sensor, i.e. then a third or fourth temperature sensor can be predicted as an air sensor - not shown.

With the help of at least two temperature sensors 7, 8, the temperature distribution existing in the operating conditions in question can be called, i.e., a curve of 4 or. 5, calculates and thus obtains the required heat emitted by the heater.

Ί

A preferred embodiment of the process is that certain surface temperatures can be used to extrapolate to the temperature of the medium in the inlet line and in the return line. From these, the logarithmic temperature excess and the thermal power are calculated together with the measured temperature in the room. According to the known three-sensor procedure, the advantage here is that the disassembled mounting method is not i

necessary and that the process is representative of a compact heating cost manifold.

The measurement of the air in the room can also be compensated by deducing from the temperature course and by using a numerically determined temperature in the room.

Alternatively, the measured temperatures cannot be used to extrapolate to the flow temperature and the return flow temperature, but the logarithmic temperature excess is directly calculated from the measured temperatures. This can be done by modifying the calculation equation, applying the adjustment factors or introducing a suitable empirical set-up. Since the logarithmic temperature excess is an empirical function of the temperatures in the supply line and return line, the equivalent magnitude can also be composed of other temperatures.

Measurement in the air in the room can also be replaced by deducing from the flow of temperature and the use of numerically determined temperatures in the room.

Alternatively, measurement of the air in the room, together with certain temperatures on the surface, is used to numerically determine the flow of the heating medium. From the flow temperature, the return flow temperature and the flow rate, the heat output is determined.

This procedure can also be used to directly determine the heat output on the heating medium side from the measured values and the room air.

A further embodiment of the process is not to calculate the quantities of a heating medium but to a certain temperature according to a adjusted heating curve, in which the exponent and / or correction factors depend on the nonlinearity of the temperature distribution.

The redundancy achieved by additional measurement in the air in the room can be used to verify the measurement in the air in the room in terms of persuasiveness, to increase the reliability of the device in terms of adaptation. However, the redundancy can be used to correct the measurement in the air in the room to increase the accuracy of the measurement device. Or, redundancy can be used to verify room airborne measurements in terms of persuasiveness to increase the accuracy of the device start-up threshold.

Preferably, the apparatus, as shown in the figure, is positioned somehow in the upper third of the heater, which also increases the measurement accuracy.

In the following, the following are illustrated to illustrate the invention:

temperature in the inlet line ti _R temperature in the return line

-θ, ϋ ₂ , ϋ ₃ , the temperature of the heating surface at the measuring point 1, 2, 3 χ, χ, x ₃ relative bavpical distance of the measuring points from the inlet connection • θ air temperature •

Q power was heating up

K _p K _? , Kp K ₄ constant characteristic of the heater

K ₅ constant characteristic for the heater and dependent on the mounting height.

1) Interpolation of inlet temperature and return line temperature! N (V _L ) - ζ

I) + e '2

II) = (Vi) ' ^{e +} ' L iii) Φ = κ ₁ · ln

From the measured values -§ _L , - & ₂ , the temperature -θ _ν in the supply line and the temperature ti _R in the return line are calculated.

From there, the power of Q heater is calculated.

2) Direct calculation of the power of the heater by means of two arbitrary temperatures of the heating surface and air temperature.

Option 1

-χ, ^χ 2- ^χ 1

In ln

Q = k,

1- e ^x 2 ~ ^x l

In

Option 2 = K, ^x 2 ^X 1

\ ¹ ln -v ^x l t

1- e

The measured values are $, $ Φ _{2 each} .

3) Direct calculation of the power of the heater by means of two temperatures on the heating surface without measuring the air temperature.

Xi

K.

^X 1 ^x 2 = k.

K.

^X 1 ^x 2 ^X 1 ^x 2 ^Χ Γ ^Χ 2

K ₄ constant characteristic of the heater _}

K ₅ constant depending on the heater and relative mounting height.

4. Corrective or. the comparative value for the measured air temperature of the electronic distributor of the heating cost according to I) by means of the third temperature of the heating surface (measured θ _ρ ΰ ₂ , $ _L ; dot is calculated fl _v , -fr _R and dotod Q).

The correction value of Δ _ρ for the measured temperature · θ _{ρ of} air is calculated using θ ₃ :

When measuring the air temperature O _L correctly, Δ _ρ = 0. This e.g. it serves for obvious verification.

5. Corrective or. the comparative value for the measured air temperature of the electronic distributor of the heating charges after II) by means of the third temperature of the heating surface (measured · 0 _ρ - &₂; hence Q is calculated).

The correction value Δ _ρ for the measured temperature -fr _{L of} air is calculated using

When measuring the air temperature · θ _Ε correctly, Δ _ρ = 0.

For

Techem AG:

PATENT OFFICE

LJUBLJANA / U,

Claims (6)

PATENT APPLICATIONS A device for measuring the heat emitted by a heater (1) through which the heating medium flows through the inlet port (2) of the return port (3), provided that at least two temperature sensors (7, spaced apart from one another) are provided in a vertical direction. 8), which are connected to the heat transfer (1), and from the measured values of these, the heat emitted by the heat transfer device (1) is calculated by means of an evaluation circuit, characterized in that the vertical distance of the two is in the total the housing (6) of the mounted temperature sensors (7, 8) is significantly smaller than the vertical distance (H) between the inlet port (2) and the return port (3). Device according to claim 1, characterized in that three or more temperature sensors (7, 8) are provided. Device according to claim 1 or 2, characterized in that at least one of the temperature sensors (7, 8) is in direct contact with the surface of the heater (1). Device according to claim 2 or 3, characterized in that one of the additional temperature sensors measures the ambient temperature. Device according to one of Claims 1 to 4, characterized in that the evaluation circuit is made by extrapolating from the measured values of the temperature sensors (7, 8) a curve (4, 5) corresponding to the respective flow of the heating medium through the heater (1) to the expected temperature profile of the heater (1). Device according to one of Claims 1 to 5, characterized in that the housing (6) with temperature sensors (7, 8) is mounted on the heater (1) in the upper third of the heater (1). For Techem AG: LJUBLJANA / 24566-xii-94-mn