JP2013032896A - Heating medium temperature control method and heating medium temperature control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating medium temperature control method capable of preventing freezing of a heating medium in a heat exchanger when a fixed or greater heat load is applied on the heat exchanger, during initial cooling from the cooling start of the heating medium until reaching a control temperature, or after the control temperature is reached to set a cooling maintaining state.SOLUTION: The heating medium control method includes: the first step of calculating the control setting value of a heating medium temperature at the exit side of a heat exchanger based on the entrance side actual measured value of the heat exchanger of the heating medium and the permitted temperature difference of the heat exchanger corresponding to the entrance side actual measured value; the second step of controlling the supply amount of low-temperature liquefied gas to the heat exchanger corresponding to a temperature difference between the exit side actual measured value of the heat exchanger of the heating medium and the control setting value; and the third step of calculating the value of a difference between the exit side actual measured value and the permitted temperature difference. When the value of the difference is compared with a control target temperature and the value of the difference is larger than the control target temperature, the first to third steps are repeated. When the value of the difference is equal to or smaller than the control target temperature, the first to third steps are repeated by using the control target temperature as a control setting value.

Description

  The present invention relates to an improvement in a heat medium temperature control method and a heat medium temperature control device.

  In chemical reaction processes such as organic synthesis and crystallization, highly accurate temperature control is required. For this reason, as a reaction tank used for a chemical reaction, a double-structured container having an independent tank (jacket) through which a heat medium (a heat medium; in the case of a cooling medium is referred to as “refrigerant”) is known. It has been. By supplying a temperature-controlled heating medium to the jacket, the reaction solution inside the reaction vessel is controlled to a constant temperature.

  Generally, a heat medium temperature control device (hereinafter simply referred to as “control device”) includes a heat medium circulation line and a circulation pump, and in the heat exchanger, a heat medium and a low-temperature liquefied gas such as liquefied nitrogen or the like. Heat exchange is performed with a cold source having a temperature lower than the freezing point of the heat medium. The jacket of the reaction tank is supplied with a low-temperature heat medium exchanged with a cold source by the control device.

  By the way, when heat exchange between the low-temperature liquefied gas that is a cold source and the heat medium in the heat exchanger, the temperature difference between the heat medium temperature on the outlet side of the heat exchanger and the control target temperature of the heat medium is measured. A feedback control method is known in which the flow rate of a low-temperature liquefied gas supplied to a heat exchanger is precisely controlled by a control valve or the like (Patent Document 1).

  However, in the conventional feedback control method disclosed in Patent Document 1, the low temperature liquefied gas supply line is provided during the initial cooling from the start of cooling of the heat medium until the heat medium reaches the set control target temperature. There was a problem that the control valve was almost fully opened, and low-temperature liquefied gas exceeding the allowable flow rate flowed to the heat exchanger. The boiling point of the low-temperature liquefied gas is sufficiently lower than the freezing point of the heat medium, and the amount of cold heat of the low-temperature liquefied gas is too large for the allowable heat of cooling of the heat medium, so in the process of cooling the heat medium from room temperature to the control target temperature There is a possibility that the heat medium is solidified inside the heat exchanger and the heat medium cannot be circulated. Further, in the cooling maintenance state, when a heat load of a certain level or more is applied to the heat exchanger, there is a possibility that the same problem occurs.

Japanese Utility Model Publication No. 6-022880

  The present invention has been made in view of the above circumstances, and during the initial cooling from the start of cooling of the heat medium until the heat medium reaches the set control temperature, or at the control temperature at which the heat medium is set. Heat medium temperature control method and heat medium temperature control device for preventing freezing of the heat medium in the heat exchanger when a heat load exceeding a certain level is applied to the heat exchanger after reaching the cooling maintenance state The purpose is to provide.

The invention according to claim 1 is a heat medium temperature control method in which a heat medium that cools an object to be cooled and a low-temperature liquefied gas are heat-exchanged by a heat exchanger to cool and control the heat medium to a predetermined control target temperature. There,
From the measured value on the inlet side obtained by measuring the heat medium temperature on the inlet side of the heat exchanger, and the allowable temperature difference of the heat exchanger corresponding to the measured value on the inlet side, the value on the outlet side of the heat exchanger A first step of calculating a control setting value of the heating medium temperature;
Calculate the temperature difference between the actual measured value on the outlet side obtained by measuring the temperature of the heat medium on the outlet side of the heat exchanger and the control set value, and respond to the temperature difference to the heat exchanger of the low-temperature liquefied gas A second step of controlling the supply amount of
A third step of calculating a difference value between the measured value on the outlet side of the heat medium temperature and the allowable temperature difference, and
When the difference value is compared with the control target temperature and the difference value is larger than the control target temperature, the first to third steps are repeated,
When the difference value is equal to or lower than the control target temperature, the first to third steps are repeated using the control target temperature as the control set value for the outlet side heat medium temperature. It is a control method.

  The invention according to claim 2 is the heating medium temperature control method according to claim 1, wherein the flow rate of the heating medium supplied to the heat exchanger is constant.

In the invention according to claim 3, the allowable temperature difference is an absolute value of a difference between the measured value on the inlet side and the measured value on the outlet side of the heat medium temperature of the heat exchanger,
The heat medium temperature control method according to claim 1, wherein the heat medium temperature control method is calculated in advance according to the type of the heat medium.

The invention according to claim 4 is a heat exchange between the heat medium flow path through which the heat medium for cooling the object to be cooled circulates, the low-temperature liquefied gas flow path for supplying the low-temperature liquefied gas, and the heat medium and the low-temperature liquefied gas. A heat exchanger for cooling the heat medium, and a heat medium temperature control device comprising:
First temperature measuring means provided on an outlet side of the heat exchanger in the heat medium flow path;
Second temperature measuring means provided on the inlet side of the heat exchanger in the heat medium flow path;
Computing means electrically connected to the first and second temperature measuring means;
A heat medium temperature control apparatus comprising: a low-temperature liquefied gas supply amount control means provided in the low-temperature liquefied gas flow path and electrically connected to the calculation means.

  The invention according to claim 5 is the heat medium temperature control apparatus according to claim 4, wherein the heat medium flow path has a heat medium flow rate control means.

  According to the heat medium temperature control method and the heat medium temperature control apparatus of the present invention, when heat exchange is performed between the low-temperature liquefied gas that is a cold source and the heat medium in the heat exchanger, the heat medium temperature on the inlet side of the heat exchanger. The control set value of the heat medium temperature on the outlet side of the heat exchanger is calculated from the measured value of the heat exchanger and the allowable temperature difference of the corresponding heat exchanger, and the actual value of the heat medium temperature on the outlet side of the heat exchanger is calculated. And the supply amount of the low-temperature liquefied gas to the heat exchanger corresponding to the temperature difference between the control set value and the control set value. Also, the difference between the measured value on the outlet side of the heat medium temperature and the above-mentioned allowable temperature difference is compared with the control target temperature, and the control set value of the heat medium temperature on the outlet side of the heat exchanger is gradually set to the control target. It is configured to approach the temperature. As a result, during the initial cooling from the start of cooling of the heat medium until the heat medium reaches the set control temperature, or after the heat medium reaches the set control temperature and enters the cooling maintenance state, it exceeds a certain level. When the heat load is applied to the heat exchanger, the low-temperature liquefied gas is not supplied to the heat exchanger more than necessary, so that the heat medium in the heat exchanger can be prevented from freezing. Therefore, there is no fear that the heat medium is solidified inside the heat exchanger and the heat medium cannot be circulated.

It is a systematic diagram for demonstrating the heat-medium temperature control apparatus which is one Embodiment to which this invention is applied.

Hereinafter, a heating medium temperature control method according to an embodiment to which the present invention is applied will be described in detail with reference to the drawings together with a heating medium temperature control device.
In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

First, the structure of the heat medium temperature control apparatus which is one embodiment to which the present invention is applied will be described below. As shown in FIG. 1, a heat medium temperature control device (hereinafter referred to as “control device”) 1 of the present embodiment exchanges heat between a heat medium that cools an object to be cooled and a low-temperature liquefied gas that is a cold source. A device for cooling and controlling the heat medium to a predetermined control target temperature T ₀ , a heat medium flow path L1 through which the heat medium circulates, a low temperature liquefied gas flow path L2 for supplying a low temperature liquefied gas, and a heat medium And a heat exchanger 2 that cools the heat medium by exchanging heat with the low-temperature liquefied gas.

  More specifically, the control device 1 of the present embodiment includes a first temperature sensor (first temperature measuring means) 3 provided on the outlet side 2a of the heat exchanger 2 of the heat medium flow path L1, and a heat medium. A second temperature sensor (second temperature measuring means) 4 provided on the inlet side 2b of the heat exchanger 2 in the flow path L1, and an arithmetic unit electrically connected to the first and second temperature sensors 3 and 4. (Calculation means) 5 and a flow rate adjusting valve (control means) 6 provided in the low-temperature liquefied gas flow path L2.

  The heat exchanger 2 is not particularly limited as long as the heat medium and the low-temperature liquefied gas can be heat-exchanged to cool the heat medium. As such a heat exchanger, specifically, a double tube heat exchanger, a tank & coil heat exchanger, or the like can be used. The heat exchanger 2 includes a heat medium flow path L1 and a low-temperature liquefied gas flow path L2 inside.

  The heat medium (heat medium; referred to as “refrigerant” in the case of a cooling medium) is not particularly limited as long as it can maintain a constant fluidity without being solidified at a temperature in a cooling maintenance state. Absent. Specific examples of such a heat medium include methanol (freezing point—97.5 ° C.), ethanol (freezing point—114.1 ° C.), silicone oil (freezing point—84 ° C.), and the like.

  The low temperature liquefied gas is not particularly limited as long as its boiling point is lower than the freezing point of the heat medium. Examples of the low-temperature liquefied gas include liquid nitrogen, liquid oxygen, liquid argon, and liquid natural gas.

  The heat exchanger 2 has a specific cooling capacity, and is indicated as a heat exchanger load heat quantity Q. Specifically, it is shown in the following formula (1).

Heat exchanger load heat quantity Q (kcal / h) = | heat medium outlet side temperature−heat medium inlet side temperature | (° C.)
× Heat medium specific heat C (kcal / kg · ° C)
× Heat medium flow rate F (m ³ / h)
X Heat medium density D (kg / m ³ ) (1)

  The heat medium flow path L1 is a heat medium flow path, and is provided so that the heat medium circulates between the heat exchanger 2 and the low-temperature reaction tank 7 (in other words, the internal flow of the heat exchanger 2). The path and the internal flow path of the low-temperature reaction tank 7 constitute a heat medium flow path L1). As shown in FIG. 1, the heat medium flow path L <b> 1 is provided with first and second temperature sensors 3, 4, a flow meter 8, and a heat medium pump 9.

  The first temperature sensor 3 is configured to measure the temperature (exit side actual measurement value) T1 of the heat medium after being cooled by the heat exchanger 2, and the outlet side (secondary side) of the heat exchanger 2 in the heat medium flow path L1 ) 2a.

  The second temperature sensor 4 is provided on the inlet side (primary side) 2b of the heat exchanger 2 of the heat medium flow path L1 in order to measure the return temperature (measured on the inlet side) T2 of the heat medium. Here, the return temperature T2 of the heat medium means that the heat medium cooled by the heat exchanger 2 circulates in the heat medium flow path L1, and again exchanges heat through the low temperature reaction tank 7, the flow meter 8, and the heat medium pump 9. The temperature of the heat medium immediately before entering the vessel 2.

The low temperature reaction tank 7 is a reaction tank used for a chemical reaction or the like. Specifically, for example, it is a double-structure container including a reaction tank in which an object to be cooled is accommodated, and a tank (jacket) provided outside the reaction tank and capable of circulating a heat medium. By supplying a temperature-controlled heat medium to the jacket, the reaction liquid or the like (substance to be cooled) inside the reaction tank is controlled to a constant temperature (for example, control target temperature T ₀ ).

  The flow meter 8 and the heat medium pump 9 are provided in the heat medium flow path L1 in order to circulate the heat medium in the flow path L1 while keeping the flow rate of the heat medium constant. The flow rate of the heat medium in the heat medium flow path L1 is implemented by controlling the heat medium pump 9 using an inverter. Specifically, the inverter frequency of the heat medium pump 9 is continuously changed so that the flow rate measured by the flow meter 8 follows the set flow rate value. On the other hand, the heat medium pump operated at a constant frequency is not preferable because the flow rate of the heat medium pump changes due to changes in density and viscosity due to temperature changes of the heat medium.

  In the present embodiment, the flow meter 8 and the heat medium pump 9 are provided on the downstream side (secondary side) of the low-temperature reaction tank 7, but the present invention is not limited to this.

  The low-temperature liquefied gas flow path L2 is a low-temperature liquefied gas flow path that is a cold source. A low temperature liquefied gas supply source (not shown) is connected to one end of the low temperature liquefied gas flow path L2, so that the low temperature liquefied gas can be supplied into the heat exchanger 2. The other end of the low-temperature liquefied gas flow path L2 serves as a discharge port for gas vaporized in the heat exchanger 2. In addition, a flow rate adjusting valve 6 is provided in the low temperature liquefied gas flow path L2 in order to control the supply amount of the low temperature liquefied gas to the heat exchanger 2.

The calculation unit 5 is, for example, a CPU (Central Processing Unit) to which a ROM, a RAM, an external input interface, and the like are connected, and the first and second temperature sensors 3 and 4 provided in the heat medium flow path L1. In addition to being electrically connected, it is also electrically connected to a flow rate adjusting valve 6 provided in the low-temperature liquefied gas flow path L2. The arithmetic unit 5 stores a program for cooling and controlling the heat medium to a predetermined control target temperature T ₀ , data (table) corresponding to the type of the heat medium, and the like. Further, the computing unit 5 is provided with input means (not shown) such as an input unit or operation buttons.

Next, the heating medium temperature control method of this embodiment using the control device 1 described above will be described. The heat medium temperature control method of the present embodiment includes an inlet side actual measurement value T2 obtained by measuring the heat medium temperature on the inlet side 2b of the heat exchanger 2, and the heat exchanger 2 corresponding to the inlet side actual measurement value T2. From the allowable temperature difference ΔT ₁ , the first step of calculating the control set value T ₀ ′ of the heat medium temperature on the outlet side 2a of the heat exchanger 2 and the heat medium temperature on the outlet side 2a of the heat exchanger 2 are calculated. A temperature difference ΔT ₂ between the actually measured outlet-side value T1 obtained by measurement and the control set value T ₀ ′ is calculated, and the supply amount of the low-temperature liquefied gas to the heat exchanger ₂ is calculated in accordance with the temperature difference ΔT _2. a second step of controlling includes a third step of calculating the difference between the value T3 of the outlet side measured value T1 and the allowable temperature difference [Delta] T ₁ of the heating medium temperature, the value T3 and the control of the difference It compares the target temperature T _0, when the value T3 of the difference is larger than the control target temperature T _0, the first to Repeat 3 steps, in the case of the value T3 of the difference is less control target temperature T ₀ is, by using the control target temperature T ₀ as a control setting value T _{0 'of} the heat medium temperature at the outlet side, first to It is characterized in that step 3 is repeated.

The case of cooling and controlling from −20 ° C. to −90 ° C. (control target temperature T ₀ ) using ethanol as a heat medium and liquid nitrogen as a low-temperature liquefied gas will be specifically described below.

First, the operator selects ethanol as the type of the heat medium from the input means of the calculation unit 5. As a result, a table corresponding to the cooling characteristics of the heat medium is selected as shown in Table 1 below, which is stored in the calculation unit 5. Next, the operator inputs and sets −90 ° C. as the control target temperature T ₀ of the heat medium.

The table shown in Table 1 shows an inlet side actual measurement value T2 obtained by measuring the heat medium temperature on the inlet side 2b of the heat exchanger 2, and an allowable temperature difference of the heat exchanger 2 corresponding to the inlet side actual measurement value T2. This represents the correspondence with ΔT ₁ . Specifically, as shown in Table 1, the temperature range of the measured value T2 on the inlet side of the heat medium is divided, for example, every 5 ° C., and the amount of heat (allowable temperature difference) that the heat exchanger 2 can cool in each temperature range. ΔT ₁ ) is set.

Here, the allowable temperature difference ΔT ₁ in the present embodiment is the absolute value of the difference between the measured value T2 on the inlet side and the measured value T1 on the outlet side of the heat medium temperature of the heat exchanger 2 (ie, ΔT ₁ = | T1− T2 | (° C.) ”, which corresponds to“ | heat medium outlet side temperature−heat medium inlet side temperature | (° C.) ”shown in the above formula (1).

  The table shown in Table 1 is prepared for each type of heat medium. Specifically, it is calculated in advance according to the cooling characteristics of the heat medium (that is, the type of the heat medium) confirmed in advance by a demonstration device or the like, and is stored in the calculation unit 5.

  The reason why a table corresponding to the cooling characteristics can be created for each heating medium is as follows. That is, the amount of heat by which the heat medium is cooled by the supply of the low-temperature liquefied gas can be calculated by the heat medium temperature difference between the inlet and outlet of the heat exchanger, the heat medium flow rate, and the heat medium specific heat (see the above formula (1)). And, since the specific heat and density of the heating medium are within about 5% in the low temperature range of about -60 ° C to -100 ° C, if the temperature is considered constant, the temperature difference and flow rate of the heating medium are measured. This is based on the fact that the approximate load heat quantity Q applied to the heat exchanger can be calculated. Therefore, it should be noted that the flow rate of the heat medium supplied to the heat exchanger 2 is constant in the heat medium temperature control method of the present embodiment.

  When the input and setting by the operator are completed, the cooling and control program stored in the calculation unit 5 is executed, and cooling of the heat medium is started. As a result, as shown in FIG. 1, the heat medium is circulated in the heat medium flow path L <b> 1 while the heat medium flow rate is controlled to be constant by the flow meter 8 and the heat medium pump 9. Further, the flow rate control valve 6 is opened, and liquid nitrogen is supplied from the low-temperature liquefied gas passage L2 to the heat exchanger 2.

(First step)
In the first step, first, an actually measured value on the inlet side (return temperature of the heating medium) T2 is measured by the second temperature sensor 4 (for example, T2 = −20 ° C.). The measured actual value T2 on the inlet side is transmitted to the calculation unit 5.

Next, the computing unit 5 reads the allowable temperature difference ΔT ₁ corresponding to the inlet side actual measurement value T2 with reference to the table shown in Table 1 above. For example, when the measured value T2 on the inlet side is −20 ° C., the allowable temperature difference ΔT ₁ is 60 ° C.

Then, with the inlet side Found T2, the allowable temperature difference [Delta] T ₁ of the heat exchanger 2 for this inlet side Found T2, the control set value of the temperature of the heating medium outlet side 2a of the heat exchanger 2 Calculate T ₀ ′. Specifically, it is calculated as control set value T ₀ ′ = T 2 −ΔT ₁ . For example, when the inlet side actual measurement value T2 is −20 ° C. and the allowable temperature difference ΔT ₁ is 60 ° C., the control set value T ₀ ′ = −20−60 = −80 (° C.).

In this way, in the first step, the control set value T ₀ ′ of the heat medium temperature on the outlet side 2a of the heat exchanger 2 is calculated. By the way, although the control target temperature T ₀ of the heat medium is −90 ° C. as described above, in the heat medium temperature control method of this embodiment, the control set value T ₀ ′ in the heat exchanger 2 is set to set the heat medium. Will be cooled.

(Second step)
In the second step, first, the first temperature sensor 3 measures the outlet side actual measured value (temperature of the heat medium after cooling by the heat exchanger 2) T1 (for example, T1 = −40 ° C.). The measured outlet-side actual measurement value T1 is transmitted to the calculation unit 5.

Next, the calculation unit 5 calculates a temperature difference ΔT ₂ between the outlet side actual measurement value T1 and the control set value T ₀ ′. For example, when the outlet side actual measurement value T1 is −40 ° C. and the control set value T ₀ ′ is −80 ° C., the temperature difference ΔT ₂ = −40 − (− 80) = 40 (° C.). Then, in response to this temperature difference ΔT ₂ , a valve opening signal is transmitted from the calculation unit 5 to the flow rate adjustment valve 6. In this way, in the second step, the supply amount of liquid nitrogen to the heat exchanger 2 is controlled according to the temperature difference ΔT ₂ between the outlet side actual measurement value T1 and the control set value T ₀ ′.

(Third step)
In a third step, first, the calculating unit 5 calculates the value T3 of the difference between the outlet side measured value T1 and the allowable temperature difference [Delta] T _1. For example, when the outlet side measured value T1 is −40 ° C. and the allowable temperature difference ΔT ₁ is 60 ° C., the difference value T3 = −40−60 = −100 (° C.).

The heat medium temperature control method of this embodiment, after the first to third steps described above, the calculating unit 5 compares the value T3 of the difference and the control target temperature T _0. Then, if the value T3 of the difference is larger than the control target temperature T ₀ and repeats the first to third steps. On the other hand, if the value T3 of the difference is less control target temperature T ₀ is, by using the control target temperature T ₀ as a control setting value T ₀ of the heat medium temperature at the outlet side _', the first to third step repeat. For example, when the difference value T3 is −100 ° C., the control target temperature T ₀ is −90 ° C. or less. Therefore, the control setting value T ₀ ′ of the heat exchanger 2 is set to −90 degrees, and the first The third step will be repeated.

Thus, the heating medium control method of this embodiment, in the initial cooling until reaching the control target temperature T ₀ from the start of cooling of the heating medium, separately from the control target temperature T ₀ of the heat medium, embossing according to the cooling step A control set value T ₀ ′ that changes every moment is set, and the flow rate of the low-temperature liquefied gas to the heat exchanger 2 is controlled by the control set value T ₀ ′. Further, the control device 1 of the present embodiment has a function of dividing the return temperature region of the heat medium every 5 ° C., for example, and setting the amount of heat (allowable temperature difference ΔT ₁ ) that can be cooled in each temperature region. Since the control set value T ₀ ′ can be set in accordance with the cooling characteristics of the heat medium confirmed in advance by a demonstration device or the like, cooling in the shortest time is possible without freezing the heat medium.

In addition, after the heat medium reaches the set control target temperature T ₀ and enters the cooling maintenance state, when a heat load exceeding a certain level is applied to the heat exchanger, the heat medium is not frozen. The cooling can be continued.

As described above, according to the heat medium temperature control method and the heat medium temperature control apparatus 1 of the present embodiment, when heat is exchanged between the low-temperature liquefied gas that is a cold source and the heat medium in the heat exchanger 2, and the measured value T2 of the temperature of the heating medium in the exchanger 2 inlet side 2b, the allowable temperature difference [Delta] T ₁ Tokyo heat exchanger 2 corresponding thereto, the control set value of the temperature of the heating medium outlet side 2a of the heat exchanger 2 T ₀ ′ is calculated, and the valve opening degree of the flow rate control valve 6 is set in accordance with the temperature difference ΔT ₂ between the measured value T 1 of the heat medium temperature on the outlet side 2 a of the heat exchanger 2 and the control set value T ₀ ′. The supply amount of the low-temperature liquefied gas to the heat exchanger 2 is controlled by adjustment.

Also, the heat medium temperature difference values T3 and the outlet side measured value T1 and the allowable temperature difference [Delta] T _1, is compared with the control target temperature T _0, of the heat exchanger 2 of the heat medium temperature at the outlet side 2a The control set value T ₀ ′ is gradually brought closer to the control target temperature T ₀ .

Thereby, during the initial cooling from the start of cooling of the heat medium until the heat medium reaches the control target temperature T ₀ , and after the heat medium reaches the set control target temperature T ₀ and enters the cooling maintenance state. When a heat load exceeding a certain level is applied to the heat exchanger, the low-temperature liquefied gas is not supplied to the heat exchanger 2 more than necessary, so that the heat medium in the heat exchanger 2 is prevented from freezing. can do. Therefore, there is no fear that the heat medium is solidified inside the heat exchanger 2 and the heat medium cannot be circulated.

1. Control device (heat medium temperature control device)
DESCRIPTION OF SYMBOLS 2 ... Heat exchanger 2a ... Outlet side of heat exchanger 2b ... Inlet side of heat exchanger 3 ... 1st temperature sensor (1st temperature measurement means)
4. Second temperature sensor (second temperature measuring means)
5. Calculation unit (calculation means)
6 ... Flow control valve (control means)
7 ... low temperature reaction vessel 8 ... flowmeter 9 ... refrigerant pump L1 ... heat medium passage L2 ... low-temperature liquefied gas passage T ₀ ... control target temperature T ₀ '· ·・ Control set value T1 ・ ・ ・ Measured value on the outlet side T2 ・ ・ ・ Measured value on the inlet side ΔT ₁・ ・ ・ Allowable temperature difference ΔT ₂・ ・ ・ Temperature difference between the measured value on the outlet side and the control set value T3 ・ ・ ・ Exit Of the difference between the actual measured value and the allowable temperature difference

Claims (5)

A heat medium temperature control method in which a heat medium for cooling an object to be cooled and a low-temperature liquefied gas are heat-exchanged by a heat exchanger to cool and control the heat medium to a predetermined control target temperature,
From the measured value on the inlet side obtained by measuring the heat medium temperature on the inlet side of the heat exchanger, and the allowable temperature difference of the heat exchanger corresponding to the measured value on the inlet side, the value on the outlet side of the heat exchanger A first step of calculating a control setting value of the heating medium temperature;
Calculate the temperature difference between the actual measured value on the outlet side obtained by measuring the temperature of the heat medium on the outlet side of the heat exchanger and the control set value, and respond to the temperature difference to the heat exchanger of the low-temperature liquefied gas A second step of controlling the supply amount of
A third step of calculating a difference value between the measured value on the outlet side of the heat medium temperature and the allowable temperature difference, and
When the difference value is compared with the control target temperature and the difference value is larger than the control target temperature, the first to third steps are repeated,
When the difference value is equal to or lower than the control target temperature, the first to third steps are repeated using the control target temperature as the control set value for the outlet side heat medium temperature. Control method.   The heating medium temperature control method according to claim 1, wherein a flow rate of the heating medium supplied to the heat exchanger is constant. The allowable temperature difference is an absolute value of a difference between the measured value on the inlet side and the measured value on the outlet side of the heat medium temperature of the heat exchanger,
The heat medium temperature control method according to claim 1, wherein the heat medium temperature control method is calculated in advance according to the type of the heat medium. A heat medium flow path through which a heat medium for cooling an object to be cooled circulates, a low-temperature liquefied gas flow path for supplying a low-temperature liquefied gas, and heat exchange between the heat medium and the low-temperature liquefied gas to cool the heat medium A heat medium temperature control device comprising a heat exchanger,
First temperature measuring means provided on an outlet side of the heat exchanger in the heat medium flow path;
Second temperature measuring means provided on the inlet side of the heat exchanger in the heat medium flow path;
Computing means electrically connected to the first and second temperature measuring means;
A heat medium temperature control apparatus comprising: a low temperature liquefied gas supply amount control means provided in the low temperature liquefied gas flow path and electrically connected to the calculation means.   The heat medium temperature control apparatus according to claim 4, further comprising a heat medium flow rate control unit in the heat medium flow path.