The vapor compression refrigerating system with throttle control of the refrigerant flow

 

(57) Abstract:

Usage: in refrigeration. The invention: the proposed cooling unit consists of a main capillary tube, an additional capillary tube 2, heat exchanger 3, a low-power heater 4, a control unit 5, resistance thermometers 6, 7, an evaporator 8, a capacitor 9, the compressor 10. One cavity of the heat exchanger 3 is made in the form of coil main capillary tube connecting the evaporator 8 and the capacitor 9, and the other cavity is included in the circuit between the output of the additional capillary tube 2 and the suction line of the compressor 10. Sign in additional capillary tube 2 is connected to the output of the capacitor 9, and the additional capillary tube 2 is installed in thermal contact with the heater 4. In steady state the value of superheat at the exit of the evaporator 8, the measured resistance thermometers 6, 7, coincides with the set. When changing the operating conditions, the control unit 5 according to the difference of boiling points and vapor at the exit of the evaporator 8 outputs a signal for changing the capacity of the heater 4, as a result changes the resistance of the additional capillary t the th in the evaporation chamber, leads to a change in cooling the main thread, drosselweg in the main capillary tube, and respectively flow in the loop, resulting in vostanavlivatsya normal filling of the evaporator 8 (set point superheat). At maximum condensing pressure main capillary tube 1 is fully ensures the normal filling of the evaporator 8 halon. In this mode, the heater 4 provides a complete locking of the steam tube additional capillary 2. If necessary, the maximum flow rate of refrigerant in the cycle the heater 4 is turned off. 1 C.p. f-crystals, 4 Il.

The invention relates to refrigeration and can be used in vapor compression refrigeration systems (PHU) for various purposes to regulate the flow of liquid refrigerant in the cycle with simultaneous throttling.

Known vapor compression refrigeration systems, in which as a throttle control device is applied capillary tube of constant cross-section. The capillary tube is placed in the refrigerant circuit between the condenser and the evaporator. The principle of operation of these controllers is based on the well-known property of the capillary t is as before the throttle (in the condenser). Use as a flow control capillary tube allows you to ensure the full integrity of the refrigerant circuit, substantially improves the reliability of the refrigeration installation.

However, existing designs of refrigeration systems with capillary tube as a throttle device is not fully meet the requirements in him. The most significant disadvantage is that the capillary tube ensures efficient operation of the refrigeration unit only in a limited interval of thermal load on the evaporator and the temperature of the medium, cooling the condenser. When significant deviations of operating conditions from optimal, through capillary tube flows insufficient or excessive amount of HFC. In the first case is sharply reduced efficiency PHU, the second creates the possibility of breakdown of the compressor. The disadvantages PHU with capillary tubes also include high sensitivity to the amount of refrigerant in the system, which complicates the manufacturing process and maintenance, reduces reliability.

The closest to the technical nature of the claimed invention is the control of the refrigerant flow. In Dan is their source of heat (electric heater).

The flow regulator of the refrigerant installed in the refrigerant circuit between the condenser and the evaporator (see Fig.1), consists of the capillary tube 1, heater 2, the pulse-phase controller 3 c temperature sensor capillary 4, switch 5, block 6. The heater 2 is induction and consists of sections 7-8.

The flow regulator operates as follows.

Depending on the value of the cooling capacity and the laws of its changes, the output of block 6 serves a combination of signals that control the switch 5, in accordance with which is engaged in work a different number of sections of the heater 2. The temperature of the capillary tube 1 is measured by the sensor 4 and is supported by a pulse-phase controller 3 at a given level, the change in the heat capacity connected to the switch 5 sections of the heater 7-8, than reaches the desired level locking capillary steam tube and is provided with the desired value of the flow rate of refrigerant in the cycle and cooling system.

An important advantage of the known device is the ability to provide the required flow rate of refrigerant in the cycle in W is the presence of an additional heater increases power consumption and reduces the efficiency of PHU;

in the regulatory process heats the entire stream flowing through the capillary tube, which causes the need for heater high power.

The aim of the invention is the reduction of energy consumption, improving the efficiency of refrigeration systems by providing the required flow rate in the loop by changing the degree of cooling of the main thread, drosselweg in the main capillary tube, the flow control bypass flow, drosselweg additional capillary tube, by changing the power of the electric heater mounted in thermal contact with an additional capillary tube.

This objective is achieved in that the refrigerating unit, containing combined in a circuit of the compressor, the condenser, the evaporator, the main capillary tube, heater, characterized in that, with the aim of reducing energy consumption and increasing the efficiency of the refrigeration cycle, it is equipped with an additional capillary tube and double chamber heat exchanger, a cavity is made in the form of a primary coil capillary tube, and a second cavity connected to the circuit between the output of the additional capillary aprovada with the outlet of the condenser and has a greater hydraulic resistance, what is the main capillary tube, and the heater is used to heat the additional capillary tube, the surface of the primary and secondary inductors has the form of a hollow sleeve with a screw thread on the outer surface that is installed in the cylindrical housing and formed with last closed capillary channels of arbitrary profile.

Distinctive features of the proposed vapor compression refrigeration systems with throttle control flow of refrigerant from the prototype is the presence of a double chamber of the heat exchanger and additional capillary tube, and a single cavity double chamber of the heat exchanger is made in the form of coil main capillary tube connecting the evaporator and the condenser, and the other cavity is included in the circuit between the output of the additional capillary tube having a greater hydraulic resistance than the main, and the suction line of the compressor. Additional capillary tube mounted in thermal contact with the heater, and the entrance is connected to the outlet of the condenser.

A comparison of the proposed technical solutions to the prototype allowed us to establish compliance with a criterion, N is the receiver, installed between the evaporator and the condenser, the flow control occurs due to a change in hydraulic resistance depending on the cooling or steam content of the refrigerant upstream of the throttle.

We offer the throttle device for a vapor compression refrigerating machines due to the described design implementation acquires other property that is not inherent in the known solutions.

This ensures efficient operation of refrigeration systems in a wide range of heat loads on the evaporator and the temperature of the medium, a cooling condenser, and excluded the possibility of the vapor in the evaporator.

The study of other technical solutions, it was found that the claimed technical solution has features that distinguish it from known solutions, and therefore meets the criterion of "Inventive step".

In Bauman Moscow state technical N. E. Bauman made a prototype of the flow regulator of the refrigerant from the primary and secondary capillary tubes. A prototype is a double chamber heat exchanger with a diameter of 50 mm and a length of 150 mm, inside which is placed in the form of coil 5 metres in length and internal diamanta and the outer surface of the coil remains a gap = 2 mm, forming evaporative cavity of the heat exchanger. Additional capillary tube length of 40 mm and an inner diameter of 0.7 mm welded throughout its length to the heater 200 watt. When testing the prototype provided the change in the flow rate of the refrigerant from 80 kg/h up to 142 kg/h when changing power of the heater from 0 to 150 watts. Due to the high cost of thermostatic expansion valves (I. R. C.), currently used as the primary regulator of the refrigerant flow, of the companies producing refrigeration unit (Odessaprodmash, Melitopolprodmash), you can use the invention as a replacement, T. D. C.

Based on the foregoing, we can conclude that the proposed solution meets the criterion of "Industrial applicability".

In Fig.1 shows a structural diagram of the prototype of Fig.2 is a structural diagram of a refrigeration unit with a flow regulator of the refrigerant, General view; Fig.3 - control the flow of refrigerant from the primary and secondary capillary tubes; Fig.4 is a variant of the design of the regulating device.

The vapor compression refrigerating system with throttle regulator R is labmedica 3, low-power heater 4, a control unit 5, resistance thermometers 6, 7, an evaporator 8, a capacitor 9, the compressor 10. One cavity of the heat exchanger 3 is made in the form of coil main capillary tube 1, which connects the evaporator 8 and the capacitor 9, and the other cavity is included in the circuit between the output of the additional capillary tube 2 and the suction line of the compressor 10. Sign in additional capillary tube 2 is connected to the output of the capacitor 9, and the additional capillary tube 2 is installed in thermal contact with the heater 4.

The proposed device operates as follows.

In steady state the value of superheat at the exit of the evaporator 8, the measured resistance thermometers 6, 7 or any other device, coincides with the set. When conditions change (change in heat load on the evaporator 8, the change in the condensing pressure), the control unit 5 according to the difference of boiling points and vapor at the exit of the evaporator 8 outputs a signal for changing the capacity of the heater 4, resulting in changes to the additional resistance of the capillary tube 2 and the refrigerant flow in the evaporator cavity, Teploobmen the main thread drosselweg in the main capillary tube 1 and respectively flow in the cycle, resulting in restored normal filling of the evaporator 8 (set point superheat). As shown by the authors ' calculations for controlling the flow of refrigerant in the cycle PHU from 50 to 100% (control range, T. D. C.), it is necessary to provide a change in the flow rate through additional capillary tube 2 in the range from 0 to 10% of the flow direct flow, which reduces the power of the heater 4 in comparison with the prototype in 10 times.

At maximum condensing pressure main capillary tube 1 is fully ensures the normal filling of the evaporator 8 halon. In this mode, the heater 4 provides a complete locking of the steam tube additional capillary 2. The mass flow rate of steam through additional capillary tube 2 in case of its full locking is negligible due to its high hydraulic resistance. If necessary, the maximum flow rate of refrigerant in the cycle, for example with the minimum condensing pressure or the maximum heat load on the evaporator 8, the heater 4 is turned off. In this mode obessively scheme has the following advantages:

significant (up to 10 times) in comparison with the prototype reducing the power consumed by the heater in the regulation;

small geometrical dimensions, weight, intensity of the heat exchanger, which provides a high heat transfer coefficient, as by boiling in the evaporator of the refrigerant, and the flow of refrigerant, drosselweg in the main capillary tube, and also due to a larger temperature difference in the heat exchanger;

the preventing steam from the evaporation cavity of the heat exchanger in the evaporator, which prevents the reduction efficiency PHU.

Instead of the primary and secondary capillary tubes can be used throttle device shown in Fig.4. It consists of thin-walled cylindrical body 1, inside of which fits the inserted hollow sleeve 2, the outer surface of which forms with the housing closed capillary channels 3 any profile. Changing the pitch and depth of thread, you can get practically any characteristic of the throttle device.

Thus, the proposed controller refrigerant flow in comparison with the known can significantly reduce energy consumption the TORUS FLOW of the REFRIGERANT, merged in the circuit of the compressor, the condenser, the evaporator, the main capillary tube, a heater, wherein the plant is equipped with an additional capillary tube with a water resistance greater than in the main capillary tube, and double chamber heat exchanger, a cavity is made in the form of a primary coil capillary tube, and the other cavity is included in the circuit between the output of the additional capillary tube and the suction line of the compressor, and an additional capillary tube connected to a liquid pipe with the outlet of the condenser and the heater is used to heat the additional capillary tube.

2. Installation under item 1, characterized in that the surface of the primary and secondary throttle channel has the form of a hollow sleeve with a screw thread on the outer surface, installed with an interference fit in the cylindrical housing and forming with the latter a closed capillary channels of arbitrary profile.

 

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