JPH08271348A - Liquid temperature measurement method - Google Patents

Abstract

PURPOSE: To precisely determine the representative temperature of a liquid in a tank at low cost with a small setting number of temperature sensors. CONSTITUTION: The temperatures of a plurality of temperature sensors 1-n are linearly approximated to determine the average temperature. On the other hand, from the temperature sensor 1 on the bottom part to a tank A bottom part, and from the temperature sensor (n) on the top part to the level, the temperature gradients with the temperature sensors situated on the upper part and the lower part from the bottom part temperature sensor 1 and the top part temperature sensor (n) are extended, respectively, to determine the average temperature. These average temperatures are weighed by the ratio of sensor interval to level height to calculate the representative temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid temperature measuring method for highly accurately measuring a liquid temperature used for measuring the liquid level in a cargo tank, for example.

[0002]

2. Description of the Related Art When measuring the liquid level height of a large tank such as a tanker, the temperature of the liquid has a great effect on the liquid density which determines the liquid level height. Therefore, conventionally, the temperature of the liquid in the tank is measured by using one temperature sensor, the density of the liquid is determined by using the temperature measured by the temperature sensor, and the density is utilized to determine the liquid level. I was looking for height.

However, for example, the temperature of the liquid in the tank whose depth is close to 50 meters has a large difference in temperature distribution between the upper and lower parts, and the liquid level height measured by the above-mentioned measuring method is significantly different from the actual value.

On the other hand, a plurality of temperature sensors are installed at positions having different heights in the tank, and a value obtained by averaging the measured values of these temperature sensors is used as a representative temperature. A method used for calculation has been proposed.

[0005]

However, in the liquid temperature measuring method in which the average value of the output values of the plurality of temperature sensors is obtained as the representative temperature, as many temperature sensors as possible are used for high precision measurement. Since it is necessary to install them, not only the cost of mounting instrumentation of these temperature sensors is high, but also there is a possibility that a temperature that is meaningless depending on the number of temperature sensors installed and the liquid level is a representative value. there were.

The present invention has been made by paying attention to the above-mentioned conventional problems, and it is possible to accurately and inexpensively obtain the representative temperature of the liquid in the tank with a small number of temperature sensors. The purpose is to obtain a measuring method.

[0007]

According to a liquid temperature measuring method of the present invention, a temperature between a plurality of temperature sensors is linearly approximated to obtain an average temperature. From the bottom temperature sensor and the top temperature sensor to the liquid surface, the average temperature is calculated by extending the temperature gradient between the temperature sensor at the bottom and the temperature sensor above and below the temperature sensor at the top, respectively. Then, the average temperature is weighted by the ratio of the sensor interval to the liquid surface height to calculate the representative temperature.

[0008]

In the liquid temperature measuring method according to the present invention, the average temperature obtained by linearly approximating the temperature between the temperature sensors and the respective temperatures below the lowermost temperature sensor and above the uppermost temperature sensor are measured. The average temperature obtained by extending the temperature gradient between the upper and lower parts of the sensor is multiplied by the ratio of the distances between the temperature sensors to obtain the average of the whole, and this is represented as the temperature of the liquid in the tank. To

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram showing a liquid temperature measuring system for carrying out the liquid temperature measuring method of the present invention. In FIG. 1, A is a large tank such as a cargo tank.

Further, 1, 2, 3 are a plurality of temperature sensors installed at different positions in the tank A, here three temperature sensors, 4 is the bottom portion of the tank A, and 5 is housed in the tank A. Liquid such as crude oil and 6 are liquid levels.

Further, 7 is each of the above temperature sensors 1, 2, 3
It is a microprocessor that calculates the representative temperature of the liquid based on the temperature data detected by and the height positions of the temperature sensors 1, 2, and 3.

Next, a method of measuring the temperature by the liquid temperature measuring system will be described. Now, the heights from the bottom portion 4 of the tank A to the temperature sensors 1, 2, 3 and the liquid level 6 are H ₁ , H ₂ , H ₃ and _HL , respectively.
Assuming that the temperatures detected by 2 and 3 are T ₁ , T ₂ and T ₃ , the liquid temperature T ₁₂ between the temperature sensors 1 and 2 is T ₁₂ = (T ₁ + T ₂ ) as an average value of these detected temperatures. It can be calculated by / 2.

Further, the liquid temperature T ₂₃ between the temperature sensors 2 and 3
Becomes T ₂₃ = (T ₂ + T ₃ ) / 2, and the liquid temperature T ₁ ′ between the bottom 4 and the temperature sensor 1 is T ₁ ′ = {(T ₁ −
_{T 2) / (H 1 -H} 2)} × (H 1/2) + T 1 -
{(T ₁ −T ₂ ) / (H ₁ −H ₂ )} H ₁ .

Further, the liquid temperature T ₃ 'between the liquid surface 6 and the temperature sensor 3 is T ₃ ' = {(T ₂ -T ₃ ) / (H _2-
H ₃ )} × {( _HL + H ₃ ) / 2} + T ₃ − {(T ₂ −
The _{T 3) / (H 2 -H} 3)} H 3.

Therefore, the representative temperature of the liquid 5 in the tank A is {(H ₁ / _HL ) T ₁ '} + {(H ₂ -H ₁ ) / H
_{L} T 12 + {(H} 3 -H 2) / HL} T 23 + {(H L -
H ₃ ) / _HL } T ₃ ′, and the above arithmetic operation is executed by the microprocessor 7.

That is, the liquid temperature in the tank A is calculated by the microprocessor 7 based on the following calculation formula. Now, the temperature detected by each temperature sensor is T ₁ , T
₂ , ... T _n−1 , T _n, and the average temperature between the bottom portion 4 of the tank A, the temperature sensors 1 to n, and the liquid level 6 is T ₁ ′, T ₂ ′, ... ..Tn _-1 ', _Tn ',
Let T _L 'be the average temperature T ₁ ', T at this time
_{2 ', ··· T n-1} ', T n ', T L' is, T ₁ '=
_{{(T 2 -T 1) /} (H 2 -H 1)} (H 1/2) + T
_{1 - {(T 2 -T 1} ) / (H 2 -H 1)} H 1, T 2 '
= (T ₂ + T ₁ ) / 2, T _n '= (T _n + T _n-1 ) /
_{2, T L '= {(} T n -T n-1) / (H n -H n-1)}
_{{(H L + H n)} / 2} + T n - {(T n -T n-1) /
(H _n -H _n-1) becomes} H _n.

Therefore, the required temperature T of the liquid 5 in the tank A is T = {H ₁ · T ₁ ′ + (H ₂ −H ₁ ) T ₂ ′ + ·
_{·· + (H n -H n-} 1) T n '+ (H L -H n) T
_L '} / _HL (n + 1). This is each temperature sensor 1
The average temperature between n and n is divided by the ratio of the height of the liquid surface 6 and averaged.

Then, the density ρ of the liquid 5 is calculated from the temperature thus obtained, and the density ρ and the pressure of the liquid detected by a pressure sensor (not shown) installed at the height h in the liquid 5 are calculated. From PV, the height H of the liquid surface 6 is H = (PV /
ρ) + h.

The uppermost temperature sensor n and the liquid level 6
The average temperature T _L 'in the interval is obtained as follows by extending the temperature gradient with the temperature sensor located below it.

Now, when the temperature value for each temperature sensor position is sequentially obtained and plotted in a graph, the linear expression y as shown in FIG. 3 is obtained.
= Ax + b is obtained. Here, the temperature gradient a between the uppermost temperature sensor n below the liquid surface and the lower temperature sensor n-1
Is, a = a _{(T n -T n-1)} / (H n -H n-1).

Further, x = from a y = T _n when _{H n, y = {(T} n -T n-1) / (H n -H n-1)} x +
_{T 1 - {(T n -T} n-1) / (H n -H n-1)} becomes H _n.

[0022] Therefore, x = time of _{(H L -H n) / 2} T
_{If L} ', then T _L ' = {(T _n −T
_{n-1) / (H n} -H n-1)} {(H L + H n) / 2} +
A _{{(T n -T n-1} ) / (H n -H n-1)} H n - T n.

The average temperature T ₁ 'between the temperature sensor 1 and the bottom of the tank A is the same as the above-mentioned T.
_It is calculated by the formula of ₁ '.

FIG. 4 shows a calculation procedure for obtaining the temperature according to the liquid level by the microprocessor 7 when three temperature sensors are installed in the tank A. To describe this, first, it is determined whether or not the lower temperature sensor 1 is below the liquid level 6 (step ST1), and if it is determined that it is the same as the liquid level 6 or above the liquid level 6, It is determined that the inside of the tank A is empty (from) (step ST2).

When it is determined that the lower temperature sensor 1 is below the liquid level 6, then it is determined whether the middle temperature sensor 2 is below the liquid level 6 (step ST3). ), If it is determined that the liquid 5 is not below the liquid level 6, the temperature T of the liquid 5 to be obtained is set to the temperature T ₁ detected by the temperature sensor 1 in the lower part (step ST4).

Furthermore, the temperature sensor 3 on the upper side is below the liquid level 6.
(Step ST5), the liquid level 6
If it is determined that the temperature of the liquid 5 is not
To T _B = {H₁ ・ T₁ ’+ (H₂ -H₁ ) T₂ ’+
(H_L -H₂ ) T_L ′} / H_L ・ 3 (Step S)
T6).

On the other hand, when the upper temperature sensor 3 is below the liquid level 6, the temperature T of the liquid 5 to be obtained is T _A
= {H ₁ · T ₁ ′ + (H ₂ −H ₁ ) T ₂ ′ + (H ₃ −H
_{2) T 3 '+ (H} L -H 3) T L' and} / H _L · 4.

The average temperatures T ₁ 'and T ₂ ' between the bottom 4, each temperature sensor 1, 2, 3 and the liquid surface 6 used here,
The values of the above-mentioned expressions are used for T ₃ 'and _TL '.

By doing so, when the liquid level (liquid level) 6 is lowered and the liquid level 6 is just positioned below one of the temperature sensors, it is possible to avoid using the output of the temperature sensor. Therefore, it is possible to prevent the temperature calculation result from being accompanied by an error, and it is possible to obtain an accurate representative temperature value.

[0030]

As described above, according to the present invention, the temperature between a plurality of temperature sensors is linearly approximated to obtain an average temperature, and in parallel therewith, from the temperature sensor at the bottom to the bottom of the tank, From the temperature sensor at the top to the liquid surface, the temperature gradient between the temperature sensor at the bottom and the temperature sensor at the top and bottom of the temperature sensor at the bottom is extended to obtain the average temperature. Since the representative temperature is calculated by weighting the average temperature with the ratio of the sensor interval to the liquid level height, the representative temperature of the liquid in the tank can be accurately and inexpensively obtained with a small number of temperature sensors installed. There is an effect that can be obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a liquid temperature measuring system for implementing a liquid temperature measuring method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a liquid temperature calculation method for liquid temperature measurement according to the present invention.

FIG. 3 is an explanatory diagram showing a method of obtaining an average temperature between the uppermost temperature sensor and the liquid surface according to the present invention.

FIG. 4 is a flowchart showing a procedure for calculating a representative temperature in a tank with three temperature sensors according to the present invention.

[Explanation of symbols]

 A tank 1-n temperature sensor 5 liquid 7 microprocessor

Claims (1)

[Claims] 1. An average temperature is obtained by installing three or more temperature sensors at different heights in a tank containing a liquid and linearly approximating the temperature between the temperature sensors by a microprocessor. On the other hand, from the temperature sensor at the bottom to the bottom of the tank and from the temperature sensor at the top to the liquid surface, the temperature with the temperature sensors above and below the temperature sensor at the bottom and the temperature sensor at the top, respectively. A liquid temperature measuring method in which a gradient is extended to obtain an average temperature, and then these average temperatures are weighted by a ratio of a sensor interval to a liquid surface height to obtain a representative temperature.