JP6937787B2 - Wet-bulb temperature calculation device, wet-bulb temperature calculation method - Google Patents

Description

The present invention relates to a technique for calculating a wet-bulb temperature.

The wet-bulb temperature can be measured using a wet-bulb thermometer. However, since the wet-bulb thermometer needs to keep the temperature-sensitive part wet at all times, it is troublesome to handle and expensive. The following Patent Document 1 discloses the following regarding a method for approximately predicting wet-bulb temperature. Using the wet-bulb humidity meter formula, numerically calculate the wet-bulb temperature with relative humidity and temperature as variables, and perform function fitting by polynomial approximation using the least squares method to create an approximate prediction formula for the wet-bulb temperature. By substituting the measured values of relative humidity and air temperature into the approximate prediction formula, the wet-bulb temperature is approximately predicted.

Japanese Unexamined Patent Publication No. 2010-266318

The wet-bulb temperature prediction method described in Patent Document 1 uses a high-order polynomial approximation formula. Therefore, the calculation is complicated and an advanced calculation function is required.

An object of the present invention is to calculate the wet-bulb temperature by a simple calculation using only a first-order approximation formula.

The wet-bulb temperature calculation device uses a linear approximation formula showing the relationship between the relative humidity x and the dry-wet temperature difference ΔT for each dry-bulb temperature Ta from the measurement data of the dry-bulb temperature Ta and the relative humidity x. Calculate Tb. In this way, the wet-bulb temperature can be calculated by a simple calculation using only the first-order approximation formula.

The arithmetic unit uses the first-order approximate straight line Lp showing the relationship between the first-order term P of the first-order approximation formula for each dry-bulb temperature Ta and each dry-bulb temperature Ta, and the first-order with respect to the measured value of the dry-bulb temperature Ta. The first-order term P of the approximation formula is calculated, and the first-order approximation straight line Lq showing the relationship between the constant term Q of the first-order approximation formula and each dry-bulb temperature Ta for each dry-bulb temperature Ta is used to obtain the dry-bulb temperature Ta. The constant term Q of the first-order approximation formula for the measured value may be calculated.

The calculation device has a first calculation unit that calculates the primary term P of the linear approximation formula for the dry-bulb temperature Ta from the measured value of the dry-bulb temperature Ta, and the dry-bulb temperature Ta from the measured value of the dry-bulb temperature Ta. a second calculator for calculating a constant term Q of the first-order approximation equation, the measured value of the relative humidity x, the 1 and the next section P computed by the first computing unit, constants calculated by the second arithmetic unit The wet ball temperature Tb is calculated from the third calculation unit that calculates the dry-bulb temperature difference ΔTab from the item Q, the measured value of the dry-bulb temperature Ta, and the dry-bulb temperature difference ΔTab calculated by the third calculation unit. It may include 4 arithmetic units.

This technology can be applied to the calculation method of wet-bulb temperature.

Wet-bulb temperature can be calculated by a simple calculation using only the first-order approximation formula.

Graph showing the relationship between relative humidity and dry-bulb temperature difference with respect to dry-bulb temperature Chart of linear and constant terms for wet-bulb temperature when first-order approximated A graph showing the relationship between the dry-bulb temperature and the linear term, and the relationship between the dry-bulb temperature and the constant term. Block diagram of arithmetic unit The figure which shows the other embodiment of the arithmetic unit

<Embodiment 1>
1. 1. Calculation principle of wet-bulb temperature FIG. 1 is a graph showing the relationship between the relative humidity x and the dry-wet temperature difference ΔTab with respect to the dry-bulb temperature Ta. ]. The dry-wet temperature difference ΔTab is a value obtained by subtracting the wet-bulb temperature Tb from the dry-bulb temperature (atmospheric temperature) Ta.

ΔTab = Ta-Tb ... (1)

L1 to L7 shown in FIG. 1 are approximate straight lines showing the relationship between the relative humidity x and the dry-wet temperature difference ΔTab for each dry-bulb temperature of 5 ° C. to 35 ° C. Each approximate straight line L1 to L7 can be represented by the following linear approximation formula.

ΔTab = Px + Q ... (2) Equation P is the linear term (slope of a straight line) of the approximate straight line L, Q is the constant term of the approximate straight line, and x is the relative humidity.

From the equations (1) and (2), the wet-bulb temperature Tb can be calculated by the following equation (3).
Tb = Ta-ΔTab = Ta- (Px + Q) ... (3)

FIG. 2 is a chart summarizing the primary term P and the constant term Q of the linear approximate expression ΔTab for each dry-bulb temperature Ta. The primary term P is a negative value, and the magnitude (absolute value) increases as the dry-bulb temperature Ta increases. Further, the constant term Q is a positive value, and the magnitude (absolute value) becomes smaller as the dry-bulb temperature Ta increases.

FIG. 3 is a graph showing the relationship between the dry-bulb temperature Ta and the primary term P, and the relationship between the dry-bulb temperature Ta and the constant term Q. The horizontal axis is the relative humidity x [%], and the right vertical axis is the primary term P [° C. /%], The left vertical axis is the constant term Q [° C].

Lp shown in FIG. 3 is a first-order approximate straight line showing the relationship between the dry-bulb temperature Ta and the first-order term P, and Lq is a first-order approximate straight line showing the relationship between the dry-bulb temperature Ta and the constant term Q. Equation (4) is a mathematical expression of the first-order approximate straight line Lp, and equation (5) is a mathematical expression of the first-order approximate straight line Lq.

P = -0.0034Ta-0.05 ... (4) Equation Q = 0.3398Ta + 4.9253 ... (5) Equation P is a linear term, Q is a constant term, and Ta is a dry-bulb temperature.

The linear term P of Eq. (2) can be obtained by using the linear approximate straight line Lp shown in FIG. Further, the constant term Q of Eq. (2) can be obtained by using the first-order approximate straight line Lq shown in FIG.

The correlation coefficient ^{R 2} of the first-order approximate line Lp, the correlation coefficient ^{R 2} of 0.9995,1 order approximation straight line Lq As an example, a 0.9997 As an example, two approximate lines Lp, Lq both , Very high correlation.

The calculation example of the wet-bulb temperature Tb using the equation (3) is shown below.

When the dry-bulb temperature Ta is 25 ° C. and the relative humidity x is 54%, the primary term P and the constant term Q corresponding to the dry-bulb temperature Ta can be obtained from the equations (4) and (5).

P = -0.0034 x 25-0.05 = -0.135
Q = 0.3398 × 25 + 4.9253 = 13.4203

Then, the wet-bulb temperature Tb can be calculated by substituting the obtained primary term P, constant term Q, dry-bulb temperature Ta, and relative humidity x into the equation (3).
Tb = 25- (-0.135 x 54 + 13.4203) = 18.8697 ° C.

When the dry-bulb temperature Ta is 25 ° C and the relative humidity x is 54%, the wet-bulb temperature Tb calculated using the psychrometer humidity table is 19 ° C, and the error rate ε is -0.69%, which is extremely high. small.

ε = 100 × (Tb1-Tb2) / Tb2
Tb1 is a wet-bulb temperature calculated using the two first-order approximate straight lines Lp and Lq shown in FIG. 3, and Tb2 is a wet-bulb temperature calculated using a humidity table for a psychrometer.

2. Description of the Wet-bulb Temperature Tb Arithmetic Logic Unit FIG. 4 is a block diagram of the arithmetic unit 50. The arithmetic unit 50 includes a first arithmetic unit 51, a second arithmetic unit 53, a third arithmetic unit 55, and a fourth arithmetic unit 57.

The first calculation unit 51 calculates the primary term P from the measured value of the dry-bulb temperature Ta by the dry-bulb thermometer. The first calculation unit 51 can be composed of, for example, a proportional device 51a, a difference device 51b, and a signal generator 51c. The proportional device 51a outputs an output proportional to the dry-bulb temperature Ta. The proportionality constant is the proportionality constant of the approximate expression of (4), that is, −0.0034. The signal generator 51c outputs a constant. The constant is the constant of the approximate expression of (4), that is, 0.05.

The difference device 51b subtracts the output of the signal generator 51c from the output of the proportional device 51a, and outputs the result as the primary term P.

The second calculation unit 53 calculates the constant term Q from the measured value of the dry-bulb temperature Ta by the dry-bulb thermometer. The second calculation unit 53 can be composed of, for example, a proportional device 53a, an adder 53b, and a signal generator 53c.

The proportional device 53a outputs an output proportional to the dry-bulb temperature Ta. The proportionality constant is the proportionality constant of the approximate expression of (5), that is, 0.3398. The signal generator 53c outputs a constant. The constant is the constant of the approximate expression of (5), that is, 4.9253.

The adder 53b adds the output of the signal generator 53c to the output of the proportional device 53a, and outputs the result as a constant term Q.

The third calculation unit 55 is a dry / wet temperature difference from the measured value of the relative humidity x by the relative hygrometer, the primary term P calculated by the first calculation unit 51, and the constant term Q calculated by the second calculation unit 53. Calculate ΔTab. The third calculation unit 55 can be composed of, for example, a multiplier 55a and an adder 55b. The multiplier 55a multiplies the relative humidity x by the linear term P calculated by the first calculation unit 51 and outputs the result. The adder 55b adds the constant term Q calculated by the second calculation unit 53 to the output of the multiplier 55a to calculate the wet / dry temperature difference ΔTab.

The fourth calculation unit 57 calculates the wet-bulb temperature Tb from the measured value of the dry-bulb temperature Ta and the dry-bulb temperature difference ΔTab calculated by the third calculation unit 55. The fourth calculation unit 57 can be configured by, for example, a diff. The difference device 57 calculates the wet-bulb temperature Tb by subtracting the dry-bulb temperature difference ΔTab calculated by the third calculation unit 55 from the measured value of the dry-bulb temperature Ta by the dry-bulb thermometer.

3. 3. Explanation of effect According to the present embodiment, the wet-bulb temperature Tb can be obtained by calculation from the measured value of the dry-bulb temperature Ta and the measured value of the relative humidity x. Therefore, there is no need for a wet-bulb thermometer, which is expensive and time-consuming to maintain.

Further, since the wet-bulb temperature Tb is calculated by a simple calculation using only the first-order approximation formula, the arithmetic unit 50 can be configured by a circuit having only four rules (first arithmetic unit 51 to fourth arithmetic unit 57). It is possible. Therefore, it can be applied to PLC (programmable logic controller) and DCS (distributed digital controller).
<Other Embodiments>
The present invention is not limited to the embodiments described in the above description and drawings, and for example, the following embodiments are also included in the technical scope of the present invention.

(1) In the first embodiment, the linear term P and the constant term Q of the equation (2) are obtained from the measured values of the dry-bulb temperature Ta and the relative humidity x by using the relationship of FIG. Although the wet-bulb temperature Tb was calculated by substituting into equation 3), the wet-bulb temperature may be calculated using the relationship shown in FIG.

(2) In the first embodiment, an example in which the arithmetic unit 50 is composed of four arithmetic units 51 to 57 is shown. As shown in FIG. 5, the arithmetic unit 150 may be composed of the CPU 151 and the memory 153, and may calculate the wet-bulb temperature Tb by digital processing. That is, the data of the two first-order approximate straight lines Lp and Lq shown in FIG. 3 are stored in the memory 153, and the CPU 151 stores the two first-order approximate straight lines Lp and Lq to the first-order term P and the constant term. Q may be obtained for each, and the wet-bulb temperature Tb may be obtained from Eq. (3).

Further, the data stored in the memory 153 is not limited to the data of the two first-order approximate straight lines Lp and Lq, and may be the first-order approximate straight lines L1 to L7 shown in FIG. In this case, the wet-bulb temperature Tb may be obtained from the data of the relative humidity x with reference to the first-order approximate straight lines L1 to L7 corresponding to the dry-bulb temperature Ta.

50 Arithmetic logic unit 51 1st arithmetic unit 53 2nd arithmetic unit 55 3rd arithmetic unit 57 4th arithmetic unit

Claims (3)

Using first-order approximate expression indicating the relationship between relative humidity x and wet and dry temperature difference ΔTab for each dry-bulb temperature Ta, it calculates a wet-bulb temperature Tb from the measured data of the dry-bulb temperature Ta and the relative humidity x, computing device met hand,
Using the first-order approximate straight line Lp showing the relationship between the first-order term P of the first-order approximation formula for each dry-bulb temperature Ta and each dry-bulb temperature Ta, 1 of the first-order approximation formula for the measured value of the dry-bulb temperature Ta. Calculate the next term P,
Using the first-order approximate straight line Lq showing the relationship between the constant term Q of the first-order approximation formula for each dry-bulb temperature Ta and each dry-bulb temperature Ta, the constant of the first-order approximation formula for the measured value of the dry-bulb temperature Ta. A computing device that computes the term Q. Using first-order approximate expression indicating the relationship between relative humidity x and wet and dry temperature difference ΔTab for each dry-bulb temperature Ta, it calculates a wet-bulb temperature Tb from the measured data of the dry-bulb temperature Ta and the relative humidity x, computing device met hand,
A first calculation unit that calculates the first-order term P of the first-order approximation formula for the dry-bulb temperature Ta from the measured value of the dry-bulb temperature Ta, and
A second calculation unit that calculates the constant term Q of the first-order approximation formula with respect to the dry-bulb temperature Ta from the measured value of the dry-bulb temperature Ta, and
A third calculation unit that calculates the dry / wet temperature difference ΔTab from the measured value of the relative humidity x, the primary term P calculated by the first calculation unit, and the constant term Q calculated by the second calculation unit.
An arithmetic unit including a fourth arithmetic unit for calculating a wet-bulb temperature Tb from a measured value of a dry-bulb temperature Ta and a dry-wet temperature difference ΔTab calculated by the third arithmetic unit. Using first-order approximate expression indicating the relationship between relative humidity x and wet and dry temperature difference ΔTab for each dry-bulb temperature Ta, calculates a wet-bulb temperature Tb from the measured data of the dry-bulb temperature Ta and the relative humidity x, met calculation method hand,
Using the first-order approximate straight line Lp showing the relationship between the first-order term P of the first-order approximation formula for each dry-bulb temperature Ta and each dry-bulb temperature Ta, 1 of the first-order approximation formula for the measured value of the dry-bulb temperature Ta. Calculate the next term P,
Using the first-order approximate straight line Lq showing the relationship between the constant term Q of the first-order approximation formula for each dry-bulb temperature Ta and each dry-bulb temperature Ta, the constant of the first-order approximation formula for the measured value of the dry-bulb temperature Ta. A calculation method for calculating the term Q.

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