SU1576811A1 - Device for quick cooling - Google Patents

Abstract

The invention relates to refrigeration and can be used in rapid cooling systems. The purpose of the invention is to increase the reliability of the device. The device contains a circuit of a liquid intermediate refrigerant in which a pump is installed, a cooled object and an intermediate heat exchanger with a valve installed at the top of the intermediate heat exchanger, a first temperature sensor installed in the inlet pipe and connected to the first inlet of the first adder, the output of which is connected to the first the input of the first limiter and the first input of the second limiter, the integrator, the first input of which is connected to the output of the first limiter, and the output to the second input of the first differential amplifier, the first input of which is connected to the output of the second limiter, and the output to the second input of the second limiter, the second temperature sensor installed in the output pipeline and connected to the first input of the second adder, the output of which is connected to the second input of the integrator and the second differential input booster. In this case, a third adder is connected to the second input of the first adder and to the second input of the second adder, the first input of which is connected to the output of the integrator, the second input is connected to the output of the differential amplifier, and the output to the actuator. High reliability is provided by the fact that the control circuit uses an integrator and a differential amplifier with limited output signals, the level of which is determined by the temperature of the intermediate refrigerant at the inlet of the intermediate heat exchanger. At any time, the amount of nitrogen fed to it does not allow supercooling of the intermediate refrigerant. 3 il.

Description

The invention relates to refrigeration and can be used in rapid cooling systems.

The purpose of the invention is to increase the reliability of the device.

FIG. 1 shows a functional diagram of the proposed device; in fig. 2 is an integrator and limiter circuit; in fig. 3 - diagrams that show the operation of the device.

The device contains an intermediate heat exchanger 1, having in the upper part a valve 2 and connected by an inlet pipe 3 to a pump 4, which is connected

pipe 5 with a cooled object 6 connected by an output pipe 7 with an intermediate heat exchanger 1 In the inlet pipe 3 a first temperature sensor 8 is installed connected to the first input of the first adder 9, the output of which is connected to the first input of the first limiter 10 and the first input of the second limiter II, the output of the first limiter 10 is connected to the first input of the integrator 12, the output of which is connected to the second input by the first or rnnchitel 10 and the first input of the third adder 13, the second temperature sensor 14 is connected,

to the first input of the second adder 15, the output of which is connected to the second input of the integrator 12 and the second input of the differential amplifier 16, the first input of which is connected to the output of the second limiter 11, the second input of which is connected to the output of the differential amplifier 16 and the second input of the third adder 13, the output of which connected to an actuator 17, which is connected by the input line 18 for supplying liquid nitrogen to the supply system with liquid nitrogen (not shown) and the output line 19 to the nozzles 20 located in the lower part of full-time heat exchanger 1. In addition, FIG. 1, liquid intermediate refrigerant 21 and nitrogen gas 22 are indicated.

The integrator 12 contains an operational amplifier 23, whose direct input is grounded, and the inverse input through a resistor R is connected to the output of the second adder 15 and through a resistor RI to the output of limiter 10, which is the output of the analog switch 24. Between the output of the operational amplifier 23 and its output an integrated capacitor C is connected. The output of the differential amplifier 16 is connected to the second input of the first limiter 10, which is the first input of the differential amplifier 25, the second input of which is the first input of the first limit bodies 10. The output of the differential amplifier 25 is connected to the analog input of the analog switch 24 and the input of the null comparator 26, the output of which is connected to the control input of the analog switch 24.

The device works as follows.

The intermediate refrigerant 21, located in the cooling facility 6, is pumped by pump 4 via pipeline 5 and inlet pipeline 3 to intermediate heat exchanger 1.

The cooling object 6 may be a closed radiator for cooling the room or a container filled with intermediate refrigerant 21, into which cooled objects can be placed, etc.

Into the intermediate heat exchanger 1 through the inlet line 18 through the actuator 17, which regulates the flow of nitrogen, and the outlet line 19 enters liquid nitrogen from the refrigerant supply system. In the intermediate heat exchanger 1, liquid nitrogen is bubbled through the nozzles 20 into the intermediate refrigerant 21, making intensive heat removal from it. Nitrogen gas 22 accumulates in the upper part of the intermediate heat exchanger 1 and when a certain pressure is reached, it is released through valve 2 to the atmosphere. Under the pressure of nitrogen gas 22, the intermediate refrigerant 21 from the intermediate heat exchanger 1 goes through the outlet pipe 7 to the facility

6 cooling. The pressure value is set by adjusting valve 2.

From the second temperature sensor 14, a signal proportional to the temperature of the intermediate refrigerant Guyh at the output of the intermediate heat exchanger 1 is fed to the first input of the second adder 15, the second input of which receives a signal proportional to the set temperature 7Y The temperature Tc should not be lower than the freezing temperature of the intermediate refrigerant (for example for water, 0 ° C; for an aqueous solution of L / aC / 2, 23 ° C; for an aqueous solution of CaCh, 53 ° C).

Simultaneously with the first sensor. 8, the signal is proportional to the temperature of the GWH at the input of the intermediate heat exchanger 1, is fed to the first input of the first adder 9, to the second input of which a signal is proportional to the specified temperature. The difference signal, proportional (Fig. 36), from the output of the first adder 9 is fed to the first input of the first limiter 10 and the first input of the second limiter 11, determines the level of limiting signals U, Ui, respectively, at the outputs of the integrator 12 and the differential amplifier 16.

At a fixed temperature Tz (for example, close to the freezing temperature), the limitation level U0 is determined by the coolant temperature TV at the inlet of the intermediate heat exchanger 1. Thus,

0 the lower the temperature 7X the lower the level of limiting the LJ0 signals at the outputs of the integrator 12 and the differential amplifier 16.

The difference signal, proportional to Tvyh-Ts (Fig. 3A), from the output of the second sum 5 of the mater 15 arrives at the second input of the integrator 12 and the second input of the differential amplifier 16 and is amplified by it K. time. Signals from temperature sensors and set temperature as voltage

0 have, respectively, the magnitude of OGvh, Ogvykh, OGz, where G is the conversion factor, V / deg.

However, the f / 2 signal at its output at any level at its input cannot exceed the limit level. Coefficient

5 gain Q, the differential amplifier 16 is chosen so that for a given error ODS signal

U2 Ku GbT3

U)

must be equal to the limit signal 170 "max at the highest temperature of the GWH at the outlet of the intermediate heat exchanger 1.

In this way

55 (G3-Tyo) -A,

(2)

where A is a dimensionless coefficient, which is determined experimentally for the most unfavorable conditions (DHG at Gvkh is maximum);

the temperature of the intermediate refrigerant at the inlet of the intermediate heat exchanger 1 at the initial time t0.

and (2) it follows that

„

Gz-T .. LT3

BUT.

Since at time t0 (Tz-Guvyh) it is many times larger than DGz, the signal Uz at the output of the differential amplifier 16 is 6 / 0max (Fig. 3g). The signal 1/2 is fed to the second input of the third adder 13. At the same time, the first input of the third adder 13 receives the signal U (Fig. 3Sv), defined by the ratio

f /,) o Ј

where TI is the integrator time constant.

At the initial time t0, and the signal 1 / C at the output of the third adder 15, controlling the operation of the actuator 17, is equal to f / 3 o "utE Amount of nitrogen Ma (Fig. Ze) entering the intermediate heat exchanger 1 per unit time through the actuator 17, is determined by

(Ј / i + /,),

where oc is a coefficient equal to the amount of nitrogen per unit control signal.

From the ratios it follows that the amount of nitrogen required to cool the intermediate refrigerant from temperature Gin to temperature TA is

.-WITH;

/with

where M is the mass of water flowing through the intermediate heat exchanger 1;

Sv - heat capacity of water;

K - the amount of thermal energy taken by the unit of mass of nitrogen when it is heated to a temperature

Ex.

The coefficient a is chosen so that, at the control signal, the intermediate refrigerant is cooled to the temperature DG | determined by the inequality

ъ-Т А № p 12

Wherein

.W.

1l.ZK

Thus, from the moment of time t0, the temperature Guyh begins to fall with a speed determined by the inertia of the heat exchange process. It is believed that T "does not change in this case). At the same time, the signal U (fig. Sv) at the output of integrator 12 begins to increase, and, as a result, the C / C signal (fig. Zd) and the flow rate of nitrogen Ma (fig. Ze).

By the time t (Gz-T) it becomes equal to DGs and the differential amplifier 16 leaves the limiting mode. At the same time, the signal Ј / 1 continues to increase at the output of integrator 12. By the time point 3, the signal is limiting.

U and set some signal 1/2 at the output of the differential amplifier 16. The time constant n of the integrator is chosen longer than the time of inertia of heat exchange.

5 If at time point C3 the temperature GWH decreases (Fig. 36), then the limit signal U0 and, consequently, the signals U, U2, Uz and the flow rate Ma also decrease (respectively Fig. S, d, e, e).

If at time tn occurs

0 the accidental lowering of the temperature Guyh is less than Tc, the signal L / 2 at the output of the differential amplifier 16 changes its sign (Fig. 3g) and, as a result, the control signal Us is immediately changed (Fig. Back) and so5 the nitrogen flow rate Ma ( Fig. Ze), which prevents the intermediate refrigerant from freezing.

The circuit of the limiter 10, which is located in the feedback circuit of the integrator 12 (Fig. 2), works as follows. A signal proportional to (Ts-Guvyh), in the form of a voltage from the output of the second adder 15, is converted into a current by a resistor R, which charges the capacitor C, and the voltage U at the output of the integrator 12 also increases.

5 This voltage goes to the first input of the differential amplifier 25. At this time, the second input receives a reference signal (G3-Gin), while at its output the polarity of the signal is such that the null comparator 26 closes the analog switch 24,

0 prohibits the passage through it of a signal to the resistor. At the time when the voltage U of the reference signal (Gz-Gvh) is exceeded, the output of the differential amplifier 25 causes an error signal, the polarity of which is such that the null comparator 26 turns on the analog switch 24 and the output signal of the differential amplifier 25 is fed through an inverse resistor the input of the operational amplifier 23, to compensate the input current supplied through the resistor. Thus, it is stabilized

5 signal U at the reference level (Gz-Gvh). This stops the charge of the capacitor C.

The device is highly reliable and allows fast

55 cooling of objects (e.g., at times of peak heat influx) due to the use of liquid nitrogen, in which case a separation of gaseous nitrogen and intermediate refrigerant outside the cooling facility occurs.

High reliability is ensured by the fact that the control circuit uses an integrator and a differential amplifier with limited output signals, and the level of limitation is determined by the temperature of the intermediate refrigerant at the inlet of the intermediate heat exchanger and, as a result, the amount of nitrogen supplied to it is not allows subcooling of intermediate refrigerant.

Claims (1)

Invention Formula A rapid cooling device comprising a circuit of a liquid intermediate refrigerant, made in the form of a closed pipeline system, in which a pump, a cooled object and an intermediate heat exchanger connected to the liquid refrigerant supply line are installed, characterized in that in order to increase the reliability of the device in it - but a valve installed at the top of the intermediate heat exchanger, and connected in series the first temperature sensor installed at the inlet of the intermediate heat exchanger, the first adder, the first limiter, the integrator, the output of which is connected to the second input of the first limiter, and the second temperature sensor connected in series, installed at the outlet of the intermediate heat exchanger, second adder, -differential amplifier and the second limiter, the output of which is connected to the second input of the differential amplifier, as well as the third adder connected in series and An integral mechanism is installed on the liquid refrigerant supply line, the first input of the third adder is connected to the integrator output, and the second input is connected to the output of the differential amplifier, the second input of the second adder is connected to the second input of the first adder, the output of which is connected to the second input of the second limiter, and the output of the second adder to the second input of the integrator. Ma t, t2 tt Fig 3