FI110823B - Method and apparatus for controlling the indoor temperature in a water heating system - Google Patents

Description

Method and Apparatus for Controlling Indoor Temperature in a Water Heating System A A P n r} v I ΐυύ / ίό

The invention relates to a method 5 for controlling the internal temperature in a water heating system according to the preamble of claim 1.

The invention also relates to an apparatus for controlling the internal temperature in a water heating system according to the preamble of claim 7.

Apparatus for adjusting the indoor temperature in a water heating system is known in the art where a temperature sensor is placed outside the space to be heated, such as a detached house, to measure the outdoor temperature and, based on this value, regulates the circulation water outlet temperature of the water heating system. There are also installations in which the heated interior is provided with a temperature sensor for measuring the indoor temperature and a setting unit for setting the desired indoor temperature. Figure 1 shows one such prior art apparatus for controlling the internal temperature. Figure 2 shows a control diagram stored in a control unit. The water central heating system comprises a heating element network 2 arranged in the space to be heated, which has a plurality of heating radiators 2a, 2b, 2c or the like and a closed circulating water circuit, i.e. a circulating . Further, the heating system comprises the actual heat source 6, such as an oil burner boiler, a wood boiler and a possible water heater or similar heat source, and a mixing valve 5 through which the heating source 6 is connected ·. closed circulating water system 3. The control system comprises a control unit 7, ul-. ; 25 temperature sensor 8, room unit 9, flow temperature sensor 10 and actuators; such as an electric motor for adjusting the mixing valve 5. The circulating water temperature sensor 10 is arranged to circulate the water supply network immediately after the mixing valve 5 in the direction of circulation of the water (indicated by arrows in Figure 1). The control unit 7 includes an electronic controller or microcontroller interface made up of analog components, v with its control units and memory circuits. The indoor temperature control is carried out in the control unit:: according to the following formula: • ♦ :: (1) Tmv + K! x ΔΤ = K2 x TU | co, '. in which formula: »* * * ♦ 2 I I u o l ό

Tmv = temperature (in ° C) of the supply water, ie the circulation water leaving the mixing valve,

Tis = indoor or room temperature (° C),

Offset = Indoor or room temperature setpoint (° C), ΔΤ = Inside - Offset eh room temperature setpoint deviation from room temperature setpoint (5 ° C) Offset (° C),

Outlet - outdoor temperature (° C),

Kj = coefficient of performance for indoor or room unit, K2 = coefficient of performance for outdoor temperature.

The outdoor temperature influence coefficient K2 is generally shown as a non-linear function between the outdoor temperature Tuiko and the flow temperature Tmv. The selectable control unit generally has a plurality of such almost infinitely adjustable / selectable functions a, b, c, d, as illustrated in Figure 2.

The above-described apparatus for controlling the indoor temperature in a water heating system operates as follows. The outdoor temperature Tuuco is measured with the outdoor temperature sensor 8 and 15 and the indoor temperature T 2, Function. ; tap P. Room unit 9 is set to the desired indoor temperature, or 'room temperature'. 20 Setpoint Adjustment · Based on the setpoint of the room unit 9, a directional curve such as curve b is made in the direction of the flow temperature axis Tmv as shown by the arrows in Figure 2. The control unit 7 gives the flow temperature Tmv. i depending on the control pulses for the actuator 11 controlling the mixing valve 5, depending on the temperature of the inlet water. If, for example, the flow temperature Tmv is higher than: 25 the temperature represented by the control curve at point P, control pulses are supplied from the control unit 7 to the actuator 11 of the mixing valve 5 so that the mixing valve 5 is closed. When the flow temperature Tmv corresponds to the weather • ·. The above condition is met and the position of the mixing valve 5 is kept constant. A resident or caregiver tries and looks for a fit; A 30-step, almost infinitely adjustable / selectable control curve, such as curve a, b, c, d, which corresponds to the desired temperature requirement over a range of possible outside temperature ranges.

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The problem with the known indoor temperature control arrangement described above is that finding a suitable control curve by trial is a time-consuming task, which most often fails the layman. This work requires someone familiar with the control system, which often results in expensive installation work.

A further weakness of the known control system is that it requires a separate outdoor temperature sensor arranged outside the space to be heated. Such a sensor is expensive because it has to withstand the severe weather conditions in Finland and in the Nordic countries in general. In addition, the outdoor sensor is often connected to the actual control unit by a long cable, which itself may already be a source of interference, thus preventing a reliable ul-10 temperature measurement. Another problem is arranging a hole in the building for the outside sensor cable and sealing it after installation to prevent moisture from entering the structures.

The object of the invention is to eliminate the drawbacks associated with the above-known known internal temperature control system. It is also an object of the invention to provide a new method and apparatus for controlling the internal temperature in a central heating system.

The method for controlling the indoor temperature in a water-central heating system according to the invention is characterized by what is set forth in claim 1. Correspondingly, the apparatus according to the invention is characterized by what is set forth in claim 20. Preferred embodiments of the invention are disclosed in the dependent claims.

An advantage of the invention is that the temperature outside the space to be heated, i.e. the external heat. there is no need to measure the temperature at all. In this case, a separate outdoor temperature sensor is not required in the apparatus of the invention. According to the basic idea of the invention, ul. . The 25 temperature sensor is mathematically replaced by other parameters; with a dedicated virtual sensor.

:: The method and apparatus of the invention have the advantage that it automatically obtains a new operating point for adjusting the internal temperature when outside conditions. or other factors change. This eliminates the need to look for an appropriate adjustment during installation. 30 curves and the user can install the entire control system without the assistance of a specialist.

.: In addition, the invention has the advantages of being stable and reliable in its control properties. It makes it possible to compensate for the effect of solar radiation on the indoor temperature as well as the effect on the indoor temperature of other internal heat sources other than radiators or the like.

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Another advantage of the invention is the simple and compact construction of the apparatus. The control unit of the apparatus according to the invention can be adapted to a very small room unit.

An advantage of the invention is also the low cost of manufacturing the apparatus over conventional internal temperature control systems.

It is also an advantage of the invention that the method and the apparatus achieve the desired indoor temperature and at the same time the optimum thermal comfort in a simple and efficient manner. In principle, the control unit has only one control knob for setting the desired indoor temperature value. Thereafter, according to the invention, the adjustment process is performed completely automatically.

In the following, the invention will be described in detail with reference to the accompanying drawing, in which Fig. 1 shows a prior art apparatus for controlling an indoor temperature in a water heating system; Figure 2 illustrates almost infinitely selectable control curves for the outdoor temperature impact coefficient used in the prior art heating system and in particular in its control unit; Figure 3 illustrates an apparatus for controlling the indoor temperature in a water-central heating system according to the invention; and •: Fig. 4 is a block diagram of the apparatus control unit of Fig. 3; and: Figures 5 and 6 show a flow chart of a method according to the invention.

The state of the art equipment is described above in the preamble of the specification and: ", with reference to Figures 1 and 2.

One apparatus according to the invention for controlling the indoor temperature in a water heating system 25 is shown in Fig. 3. The same components are used in this apparatus. Apparatus according to the invention: Firstly, it differs from the prior art apparatus shown in Fig. 1. with respect to the fact that no temperature sensor outside the space to be heated is required: a sensor for measuring outdoor or ambient temperature and, secondly, that the control unit 12 is implemented in another way. The control unit 12 itself includes: preferably a microcontroller or similar data processing unit for its interface circuitry and its memory circuits. However, the internal structure of the control unit 12 is defined in a new way by the most advantageously programmatically implemented units. However, it will be clear to one skilled in the art that software units can also be implemented as circuit engineering solutions with physical electronic components and / or integrated circuits.

The method according to the invention is based on the idea that outdoor temperature fluctuations affect the flow temperature, whereby it is possible to determine from the flow temperature an auxiliary variable, i.e. a virtual outdoor temperature function, describing the outdoor temperature and its variation. For illustrative purposes this is represented mathematically by the following formula: 10 (2) Tmv + K1xAT = f (Tvu).

The starting point is the formula 1 presented above in the preamble of the description, whereby the flow temperature Tmv and the deviation of the indoor temperature from the setpoint ΔΤ are already defined, as well as the influence of the room unit Ki. The function f (Tvu) is a virtual outdoor temperature function. As can be seen, the outdoor temperature-15 function K2 x Tuik0 shown in formula 1 is now replaced by the virtual outdoor temperature function f (Tvu) · Formula 2 is written as: (3) Tmv - f (Tvu) + Kt x ΔΤ = 0 Let (4) Amv = Tmv - f (Tvu), •, · 20, which can be called the supply water temperature difference function, ie the mv difference function.

. ·. This is placed in formula 3 to give the following simple formula: (5) Amv + Ki x ΔΤ = 0. '. With reference to formulas 4 and 5, the indoor temperature control according to the invention is implemented in a central heating system as follows. A first control circuit 13, 25 of FIG. 4, is arranged to implement formula 5 and a second control circuit 14 is provided to implement formula 4.

The first control circuit 13 includes an adder 15, an integration 16, and a comparator 17.

Thus, the first control circuit 13 is formed as an ΡΙ-regulator. Adding 15 feeds

subtract Δ sisäl of the indoor temperature 30 multiplied by the factor K1 of the room unit and the output signal from the other control circuit 14, i.e. the value of the mv difference function Amv. The integrator 16 calculates the function S = Amv + K (xAT

110823 6 is integral with time ES and is compared in comparator 17 with preset thresholds Rail and Ral2, of which one of the limits Ral2 is greater than the first Rail. If the calculated integral ZS is lower than the first threshold Rail, the flow temperature Tmv is adjusted higher than before, and if 5 ES is lower than the first threshold Rail, the flow temperature Tmv is lowered than before. If the value of the integral ZS is between the limits, no control action is taken. It should be noted that the temperature of the flow water is carefully adjusted. After the comparison step, the integrator 16 is reset and, after a time delay, the new indoor temperature deviation value ΔΤ and the output signal from the second control circuit 14, i.e. the value of the mv difference function Ämv through the multiplier 18 and adder 15 are read to the integrator 16. The output control signal 13 of the first control circuit 13 is applied to the actuator 11 and thereafter to the mixing valve 5. The temperature Tmv of the supply water from the mixing valve 5 of the circulation mains is thus affected. The feedback is accomplished via the supply water temperature Tmv 15 and the second control circuit 14. The first control circuit 13 is a relatively fast control circuit.

The second control circuit 14 is a closed control loop, preferably also implemented by means of a PI controller. The second control circuit 14 minimizes the value of the mv difference function Amv and determines a new virtual outdoor temperature f (Tvu) n) i (n = positive integer 20) based on the difference between the measured flow temperature Tmv and the previously set / adjusted virtual outdoor temperature f (Tvu) n. The second control circuit 14 includes an adder 19 for generating said difference, a first integrator 20 for integrating the difference value Tmv - f (Tvu) over time, a comparator 21 integr. . a scaling unit 22 for proportioning the comparator output signal and a second integrator 23 for integrating the proportional result. The output signal of the second integrator 23 represents a new "value f (Tvu) n + i" of the virtual outdoor temperature function f (Tvu), which is input to the second input 19b of the summing 19 inverted as a negative value. The first input 19a of the adder 19, in turn, is supplied with: a flow temperature value Tmv from the flow temperature sensor 10.

30 When starting the adjustment process, such as after installation or a power failure, the initial value of the virtual outdoor temperature f (Tw) is set to the measured flow temperature; '; 'Is a value dependent on Tmv. Most preferably, the value of the virtual outdoor temperature f (Tvu) al is set to the measured temperature Tmv of the flow water when the measured indoor temperature. The deviation ΔΤ between the temperature i and the set indoor temperature does not exceed a predetermined negative • · 35 threshold, ie the indoor temperature has not yet significantly decreased.

The actual indoor temperature is then lowered relative to the set indoor temperature value.,. , -. ....,,., * i-u up to a few degrees (° C), eg 2 ° C. However, if the indoor temperature has fallen significantly relative to the set indoor temperature, i.e. the deviation of the indoor temperature ΔΤ exceeds a predetermined negative threshold, the initial value of the virtual outdoor temperature f (Tvu) is set at a predetermined increment of the measured flow temperature Tmv 5. This elevated temperature value is preferably a few degrees higher than the measured flow temperature. Here, the control unit 12, in particular the second control circuit 14, comprises means for setting an initial value of the virtual outdoor temperature (f (Tvu)) so that it is dependent on the measured flow temperature (Tmv) of the flow water as described above.

10 The comparator 21 following the first integrator 20 of the second control circuit 14 compares the integration result with the set third and fourth limit values Ra21 and Ra22, of which the fourth limit value Ra22 is greater than the third Ra21. When the integration result falls outside of the limits Ra22, Ra21, i.e. greater than or less than the limits, a suitable output signal, preferably a voltage pulse 15 or the like, is provided to the scaling unit 22 while resetting the integrator 20.

The output signal from the first integrator 20 is stored in the tracking register 22a belonging to the scaling unit 22 and multiplied by the multiplier 22b with a preset constant factor Ks. The standard factor Ks is selectable and case-specific. The output signal from the scaling unit 22 defines a tracking rate z, i.e., the rate at which the second control circuit 14 operates and generates a new virtual outdoor temperature value. The second control circuit 14 is a significantly slower control circuit than the first control circuit 13, and in addition its speed can be controlled by a scaling unit.

The second integrator 23 integrates the tracking monitor from the scaling unit 22. : a value of z relative to time. The output signal from integrator 23 corresponds to a modified virtual outdoor temperature value f (Tvu) n + i, which is added to add 19 negative • * '; or inverting input 19b.

The integral of the Mv difference function Amv over time is always calculated in the first:: 30 integrator 20. When the integral has reached either of the two predetermined thresholds Ra21 or Ra22, the integrator is reset and simultaneously. transmitting from the comparator 21 pulses forward. The pulse is positive when the lower limit Ra21 is reached or below, and the negative when the higher limit Ra22 is reached or exceeded. This pulse train from comparator 21 is proportional to the scaling unit 22 and has a preset constant Ks as the scaling factor.

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The scaling unit 22 then generates a new function, i.e. the tracking rate z = Κ / Γ, where T is the time interval of the pulses of the pulse train obtained from the first integrator. The value of the tracking rate z may then be positive or negative depending on the sign of the reached limit Ra2. With the tracking speed z, the content of the associated memory unit is increased or decreased by predetermined units by means of the second integrator 23. The contents of the memory is the value of the second integrator 23, i.e. the time integral of the tracking rate z.

In adder 19, after one control cycle of the second control circuit 14, a new mv difference function Amv is obtained which is used in the next control circuit 10 of the second control circuit and is sent to the first control circuit 13 and in this case to the second input of adder 15.

As a result of the operation of the first and second control circuits 13, 14, the mv separation function Amv acts in the manner described above so that the virtual outdoor temperature function f (Tvu) asymptotically approaches the flow water temperature Tmv. When Tmv = f (Tvu) is the tracking-speed z = 0 and the control system has accomplished its function and is then in a stable state.

Kim formula 5 is written in a new form: (6) Δ T = -Amv / Ki, we see that while the control system adjusts the mv difference function Amv to zero 20, the room temperature deviation AT = 0. This means that the prevailing indoor. The temperature, that is, the room temperature, is about the set value and the flow temperature corresponds to the ever-present outdoor temperature and the need for heat. The step response of this:: type of control system is known to be exponential.

•. The process steps of the method according to the invention are schematically illustrated in Flow1. 5 and 6. The flow chart is already briefly described above in connection with the structure of the control system. Let us first consider the operation of the first control circuit 13. In the first step 51, the constant coefficients Ki, See. These can be defined when installing a 1 »system. At the same time, set the virtual outdoor temperature function I · 30 f (Tvu) = D, where D = initial value, such as a suitable constant value, or most preferably flow temperature ·: as a function of temperature as described above. In the second stage 52 rooms: ·; Unit 9 reads room temperature deviation from setpoint AT and flow '. temperature sensor 10 flow temperature Tmv. In the next step 53, the mv difference function Amv is calculated according to formula 4. Thereafter, in step 54, 9,110,823 is calculated

Si = Amv + Κι x ΔΤ. In the next step 55, the integration with the integrator 16 is performed, i.e. the values calculated so far Σ Si (where i = 1, 2, 3, ...) are stored in the memory.

In the next step 57, it is checked whether the value of the integral Σ Si is less than or equal to 5 than the first set limit Rail. If the Rail limit is reached and / or below, the mixing valve 5 is adjusted (e.g. in direction +, Fig. 3) by the actuator 11 in a small step such that the circulation water temperature (i.e. the flow temperature Tmv) rises slightly (step 59). If the value of the integral Σ Si is greater than the first set limit value Rail, then step 58 is taken. In this step 58, it is checked whether the value of the integral Σ Si is greater than or equal to the second set limit value Ral2. If the threshold Ral2 has been reached and / or exceeded, the mixing valve 5 is adjusted (e.g. in the direction -) by the actuator 11 in a small step so that the circulation water temperature (i.e. the flow temperature Tmv) decreases (step 60). If the value of the integral Σ Si lies between the set limit values Rail, Ral2, after a short pre-set-time delay 56, it proceeds to the beginning again, i.e. step 52, and reads the new measured values ΔΤ, Tmv.

After the evaluation and adjustment steps 57, 58, 59 and 60, in step 61 the integrator 16 is reset, i.e. e.g., the initial value of the integral ra Si = E is set, where E = constant, most preferably a positive integer. Thereafter, the weather-20 operation steps are initiated after a slight delay from 56 vessels by reading the measured values ΔΤ and Tmv in step 52.

Above, the value of the mv difference function Amv in step 53 was calculated. This step itself is part of the second control circuit 14. The result, i.e. the initial value of the mv difference function 14, is also fed to the first integrator 20 of the second control circuit 14. value, ie summing up the ar- vot Σ Amv; (, where i = 1, 2, 3, ...) and stored in memory. The result is compared in the following steps 63a, 63b with the preset thresholds Ra21 and Ra22; if the integral value is Σ Διην; is between the said limits Ra21, Ra22, after a slight delay, step 56, reset, and in step 52 again measure ΔΤ and Tmv 30 and restart the calculations. If the integral of the mv separation function is Σ Διην; • · is less than or equal to the third cut-off value Ra21, a positive pulse or a corresponding message is forwarded. If the integral of the mv separation function is Σ Διην; is ·, · greater than or equal to the fourth cut-off value Ra22, a negative pulse or equivalent message is passed. The tracking rate z = Ks / T is calculated based on the pulses or messages received in step 64, 35. In the next step 65, the second integrator 23 calculates the integral of the tracking rate z, i.e. summing up the values calculated so far Σ z; (, where i = 1, 2, 3, ...) and stored in memory.

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Depending on which third Ra21 or fourth Ra22 limit is reached, the tracking speed z will increase or decrease. The integral of the tracking rate z represents the virtual external temperature function f (Tvu), which is taken into account in the next step 53 of the calculation of the mv difference function Amv. The first integration 20 is reset in step 66, i.e. the value of the integral is most preferably set to positive constant F and, after calculating and integrating the tracking rate 64, 65, returning to step 62, i.e., starting to compute the mv-10 difference function and its integral with new initial values in steps 53 and 62.

The invention is not limited solely to the above exemplary embodiment, but many modifications are possible within the scope of the inventive idea defined by the claims.

Claims (10)

11 ViUCzö A method for adjusting the internal temperature in a water heating system, wherein the mixing valve between the circulating water and the heat source is adjusted to adjust the initial temperature of the circulating water, i.e. the flow temperature, to the desired internal temperature, characterized in that of the function S = Amv + K | x ΔΤ by a suitable controller, such as a PI controller, with a constant K | is a preset value and the measured values are 10 indoor temperature deviations from the indoor temperature setpoint ΔΤ and the flow temperature Tmv and where the mv difference function Amv is defined as the difference between the flow temperature (Tmv) and the virtual outdoor temperature (f (Tvu)) (Tvu)) by minimizing the value of the mv difference function (Amv) by means of a suitable controller such as a P1 controller. A method according to claim 1, characterized in that the first control circuit (13) is arranged to operate rapidly and the second control circuit (14) is considerably slower in relation thereto. Method according to claim 1 or 2, characterized in that the first 20-pin control circuit (13) calculates the integral of the function S = Amv + KixAT over time (ES) and compares it with preset thresholds (Ral 1, Ra 12). ), of which one of the limit values (Ral2) is higher than the first (Rail) and if the calculated integral (ES) value is lower than the first limit value (Ral 1), the flow temperature (Tmv) is adjusted higher than before; if, on the other hand, the calculated integral (ES) value is lower than the first threshold (Rail), the flow temperature (Tmv) is lowered than before. A method according to any one of the preceding claims, characterized in that: -:. in the second control circuit, the following steps are carried out: ,,,, · a) calculating the value of the mv difference function Amv from the difference between the measured flow temperature Tmv and the virtual outdoor temperature f (Tvu); .... b) integrating the mv-resolution function (Amv) over time, i.e. summing the calculated value of the mv-resolution function to its previous value; 12 Λ i Π 0 '0 I i U u c. 0 c) comparing the result of the integration, i.e. the sum function, with the predetermined thresholds (Ra21 and Ra22), one of which is greater than the first (Ra21), by comparison; cl) if the value of the integral (Σ AmVj) is within the range of said limits (Ra21, Ra22), it returns to step a, i.e. reads a new temperature measurement (Tmv) of the temperature of the flow water; c2) if the value of the integral (Σ Amv,) is less than or equal to the first threshold value (Ra21), a positive pulse or a corresponding message is forwarded; c3) if the value of the integral (v Amvj) is greater than or equal to the second limit value (Ra22), a negative pulse or a corresponding message is forwarded; c4) resetting the mv difference function value (Amv) when the integral value (Σ Amy) has reached either of the two preset thresholds (Ra21, Ra22); d) generating the tracking rate value (z) 15 based on the successive messages by scaling it with a suitable constant Ks; e) integrating the tracking rate (z) over time, i.e. summing up the successive tracking rate values; f) determining the integrated tracking rate (z) as the virtual outdoor temperature function f (Tvu) and setting the integrated tracking rate value to the new virtual outdoor temperature value of the outdoor temperature function (f (Tvu) n + 1); and g) returning to step a. Method according to one of the preceding claims, characterized in that, when the control process is started, the initial value of the virtual outdoor temperature f (Tvu) is set to a value dependent on the measured temperature value Tmv of the flow water. A method according to claim 5, characterized in that the initial value of the virtual outdoor temperature f (Tvu) is set to: the measured temperature value Tmv of the flow water when the deviation ΔΤ of the measured indoor temperature and the set indoor temperature does not exceed a predetermined negative threshold; and a predetermined elevated temperature value relative to the measured flow temperature value Tmv when the deviation Δ mit of the measured indoor temperature and the set indoor temperature exceeds a predetermined negative threshold. 13 j i ϋ ο ''. ό 7. Apparatus for controlling the indoor temperature in a water heating system, wherein 5 apparatus for adjusting the mixing valve between the circulating circuit and the heat source by means of a control unit for adjusting the starting or flow temperature of the circulating water to the desired indoor temperature, characterized in that , 16, 17) for controlling the flow temperature (Tmv) of the flow water 10 by means of the room temperature offset (ΔΤ), the flow temperature (Tn, v) and the virtual outdoor temperature (f (Tv)) supplied to the control circuit; and a second control circuit (14) defining a new virtual outdoor temperature value (f (Tvu) n + 1) based on the difference between the flow temperature (Tmv) and the previously set / adjusted virtual 15 outdoor temperature value (f (Tvu) n), the control circuit including an adder (19) for generating said difference, a first integrator (20) for integrating the difference value, a scaling unit (22) for a first integrator (20),. and a second integrator (23) for integrating the proportional result, the output signal of the integrator (23) representing a new virtual outdoor temperature value input to the adder (19), and the adder output signal from the first control circuit (13). Apparatus according to claim 7, characterized in that the second control circuit (14) comprises means for setting the initial value of the virtual outdoor temperature (f (Tvu)) so that it is dependent on the measured temperature (Tmv) of the flow water. Apparatus according to Claim 7 or 8, characterized in that the first integrator (20) of the second control circuit (14) includes a comparator (21) for comparing the integration result with two set thresholds (Ra21. Ra22) which the comparator (21) by providing a suitable output signal, preferably a voltage pulse or the like, when either threshold is reached and both are exceeded or respectively lowered and the integrator (20) is reset. Apparatus according to claim 7, 8 or 9, characterized in that the scaling unit (22) comprises a multiplier (22b) in which the output signal from the first integrator (20) is multiplied by a predetermined constant coefficient (Ks). (z) to determine the value and its integral, that is, the new virtual outdoor temperature value.