Two-stage cascade refrigeration thermostatic bath

Abstract

The utility model relates to a two-stage cascade refrigeration thermostatic bath which comprises a high-temperature refrigeration system and a low-temperature refrigeration system, the high-temperature refrigeration system is filled with a high-temperature refrigerant, a plate heat exchanger is cooled in advance, the plate heat exchanger serves as an evaporator of the high-temperature refrigeration system and also serves as a condenser of a medium-temperature refrigeration system, and a liquid storage tank stores the condensed high-temperature refrigerant in advance. The low-temperature system is filled with ultralow-temperature refrigerants, the high-temperature and high-pressure ultralow-temperature refrigerants sprayed out of the low-temperature-stage compressor pass through the oil separator, then enter the precooled plate heat exchanger to be condensed into a liquid state, enter the capillary tube to be depressurized and gasified after impurities and water are filtered out through the filter, and then enter the evaporator in the constant-temperature tank to be cooled. The evaporation temperature of the low-temperature refrigerant can reach-85 DEG C, in order to avoid liquid impact caused by the fact that the unevaporated liquid refrigerant enters a return pipe of the compressor, the expansion tank is installed for pre-liquefaction storage, and the system is easy and convenient to operate and capable of running continuously during working, and rapid cooling is achieved.

Description

Technical Field

[0001] The utility model relates to a thermostatic bath, in particular to a double-stage cascade refrigeration thermostatic bath. Background Art

[0002] The lower temperature limit of the thermostatic bath currently used in the market is mostly -40℃. The main principle (such as Figure 1 As shown in the figure): the compressor outlet is connected to the condenser inlet, the condenser outlet is connected to the filter inlet, the filter outlet is connected to the capillary (or throttle valve) inlet, the capillary (or throttle valve) outlet is connected to the evaporator inlet, and the evaporator outlet is connected to the compressor inlet. The high-temperature and high-pressure gaseous refrigerant ejected from the compressor is condensed into a high-pressure and medium-temperature liquid refrigerant through the condenser. When the refrigerant passes through the filter to the throttling device (throttle valve or capillary tube), the pressure is reduced, the liquid refrigerant is vaporized, and absorbs heat to achieve the purpose of cooling the evaporator (set in the constant temperature tank) and cooling the liquid in the constant temperature tank.

[0003] The disadvantages are:

[0004] The refrigerant in this refrigeration system is mostly a medium-low temperature refrigerant with a boiling point of about -45℃, plus a superheat of 5~10℃, so the lower limit of the low temperature is about -40℃. This constant temperature bath can detect temperature sensors of -40~100℃, but cannot meet the detection requirements of low temperature sensors of -40~-80℃. Since the low temperature refrigerant cannot be liquefied under the condenser at room temperature, the single-machine refrigeration system cannot gasify the low temperature refrigerant, and thus cannot reduce the temperature. Summary of the invention

[0005] In order to solve the above technical problems, the utility model is a two-stage cascade refrigeration thermostatic tank, and its technical solution is:

[0006] It includes a high-temperature refrigeration system, a plate heat exchanger and a low-temperature refrigeration system, wherein the plate heat exchanger is connected to the high-temperature refrigeration system and the low-temperature refrigeration system respectively;

[0007] The high-temperature refrigeration system includes a high-temperature compressor, a condenser, a liquid storage tank, a filter, a capillary tube and a solenoid valve connected on the pipeline, the outlet of the plate heat exchanger is connected to the inlet of the high-temperature compressor, the outlet of the high-temperature compressor is connected to the inlet of the condenser, the outlet of the condenser is connected to the inlet of the liquid storage tank, the outlet of the liquid storage tank is connected to the inlet of the filter, the outlet of the filter is connected to the inlet of the capillary tube, a 1.2-meter capillary tube controlled by a solenoid valve is installed in parallel on the capillary tube inlet pipeline, and the outlet of the capillary tube is connected to the inlet of the plate heat exchanger;

[0008] The low-temperature refrigeration system includes a filter, a capillary tube, a solenoid valve, an evaporator, an expansion tank, a low-temperature compressor and an oil separator connected on the pipeline. The outlet of the plate heat exchanger is connected to the inlet of the filter, the outlet of the filter is connected to the inlet of the capillary tube, a 1.2-meter capillary tube controlled by a solenoid valve is installed in parallel on the capillary tube inlet pipeline, the capillary tube outlet is connected to the inlet of the evaporator, the evaporator outlet is connected to the inlet of the expansion tank, the expansion tank outlet is connected to the inlet of the low-temperature compressor, the outlet of the low-temperature compressor is connected to the inlet of the oil separator, and the outlet of the oil separator is connected to the inlet of the plate heat exchanger.

[0009] Furthermore, the high-temperature compressor and the low-temperature compressor are 2-HP fixed-frequency compressors.

[0010] Furthermore, the high-temperature refrigeration system uses refrigerant R404A, and the low-temperature refrigeration system uses refrigerant R23.

[0011] Furthermore, the evaporator is arranged inside the thermostatic tank and is coiled with a refrigeration copper tube, and a heater is placed at the center of the refrigeration copper tube.

[0012] Furthermore, a pressure switch is connected to the oil distribution pipeline of the low-temperature refrigeration system.

[0013] The beneficial effects of the utility model are as follows: the utility model is a two-stage cascade refrigeration thermostatic bath. Compared with the prior art, the utility model is optimized on the basis of a single compressor, including a high-temperature refrigeration system and a low-temperature refrigeration system. The high-temperature system is filled with high-temperature refrigerant. When the system is running, the system runs in advance, and the function is to pre-cool the plate heat exchanger. The exchanger is the evaporator of the high-temperature system and the condenser of the medium-temperature system. It is the connecting component of the whole system. The system uses a liquid storage tank for the purpose of pre-storing the condensed high-temperature refrigerant to ensure sufficient usage. The low-temperature system is filled with ultra-low temperature refrigerant. The high-temperature and high-pressure ultra-low temperature refrigerant sprayed by the low-temperature compressor passes through the oil separator and enters the pre-cooled plate heat exchanger to condense into liquid. After filtering impurities and moisture through the filter, it enters the capillary tube to reduce pressure and then gasifies, and then enters the evaporator in the thermostatic bath to cool down. The evaporation temperature of this low-temperature refrigerant can reach -85°C. In order to avoid the unevaporated liquid refrigerant entering the compressor return pipe to cause liquid hammer, an expansion tank is installed for pre-liquefaction storage to achieve the purpose of cooling the liquid in the thermostatic bath. The utility model system is easy to operate and can run continuously during operation to achieve rapid cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic block diagram of the prior art structure;

[0015] Figure 2 It is a schematic diagram of the structure of the utility model. DETAILED DESCRIPTION

[0016] This patent is based on the original single compressor refrigeration technology of the thermostatic tank. After optimization and expansion, a two-stage cascade compressor refrigeration technology was developed. A second refrigeration system was added to the original high-temperature refrigeration system, and the overall device is shown in the figure.

[0017] The utility model is a two-stage cascade refrigeration thermostatic bath, comprising a high-temperature refrigeration system (using refrigerant R404A), a plate heat exchanger and a low-temperature refrigeration system (using refrigerant R23), wherein the plate heat exchanger is connected to the high-temperature refrigeration system and the low-temperature refrigeration system respectively;

[0018] The high-temperature refrigeration system includes a high-temperature compressor, a condenser, a liquid storage tank, a filter, a capillary tube and a solenoid valve connected on the pipeline, the outlet of the plate heat exchanger is connected to the inlet of the high-temperature compressor, the outlet of the high-temperature compressor is connected to the inlet of the condenser, the outlet of the condenser is connected to the inlet of the liquid storage tank, the outlet of the liquid storage tank is connected to the inlet of the filter, the outlet of the filter is connected to the inlet of the capillary tube, and a solenoid valve is installed on the capillary tube outlet pipeline and connected to the inlet of the plate heat exchanger;

[0019] The low-temperature refrigeration system includes a filter, a capillary tube, a solenoid valve, an evaporator, an expansion tank, a low-temperature compressor and an oil separator connected on the pipeline. The outlet of the plate heat exchanger is connected to the inlet of the filter, the outlet of the filter is connected to the inlet of the capillary tube, a solenoid valve is installed on the capillary tube outlet pipeline and is connected to the inlet of the evaporator, the outlet of the evaporator is connected to the inlet of the expansion tank, the outlet of the expansion tank is connected to the inlet of the low-temperature compressor, the outlet of the low-temperature compressor is connected to the inlet of the oil separator, and the outlet of the oil separator is connected to the inlet of the plate heat exchanger.

[0020] Furthermore, the high-temperature compressor and the low-temperature compressor are 2-HP fixed-frequency compressors.

[0021] Furthermore, the evaporator is arranged inside the thermostatic tank and is coiled with a refrigeration copper tube, and a heater is placed at the center of the refrigeration copper tube.

[0022] The working process of the utility model is as follows:

[0023] The high temperature system is filled with high temperature refrigerant, and its main components are as follows Figure 2In the left half, the system runs for 5 minutes in advance during operation. Its function is to pre-cool the plate heat exchanger. This exchanger is the evaporator of the high-temperature system and the condenser of the medium-temperature system. It is the connecting part of the whole system. Compared with the original system, the high-temperature system has an additional liquid storage tank. The purpose is to pre-store the condensed high-temperature refrigerant to ensure sufficient usage. The right half is the low-temperature system, which is filled with ultra-low-temperature refrigerant. The high-temperature and high-pressure ultra-low-temperature refrigerant sprayed by the No. 2 compressor passes through the oil separator (referred to as oil separator, which is used to return the compressor oil to the compressor) and enters the pre-cooling (low temperature can reach -30~-40℃) plate heat exchanger to condense into liquid. After filtering impurities and moisture through the filter, it enters the capillary tube to reduce pressure and then gasifies, and then enters the evaporator in the constant temperature tank to cool down. The evaporation temperature of this low-temperature refrigerant can reach -85℃. In order to prevent the unevaporated liquid refrigerant from entering the compressor return pipe and causing liquid hammer, an expansion tank is installed for pre-liquefaction storage. At the same time, due to the high filling and operating pressure of ultra-low temperature refrigerant, in order to protect the normal operation of the system, a pressure switch is connected to the oil distribution pipeline of the low temperature system, and the system will stop running when the pressure is too high. At the same time, this patent sets manually controlled solenoid valve switches in the two-stage system. If normal cooling is required, only the normally closed end high temperature level 0.5 meter capillary and the low temperature level 1.8 meter capillary are used. If the temperature is cooled quickly, the 1.2 meter capillaries controlled by the normally open end solenoid valve can be opened. At this time, the normally closed end and the normally open end will work at the same time to achieve the purpose of cooling at the fastest speed.

[0024] Low-temperature refrigerants are different from commonly used high-temperature refrigerants such as air conditioners. They require a lower condensation temperature. This patent adopts two refrigeration systems, which are connected by plate heat exchangers to effectively solve this problem. The system is easy to operate and can run continuously. With two compressors with a cooling capacity of 2 HP, 20L of anhydrous ethanol can be cooled to -80℃ within 2 hours.

[0025] Used in this utility model:

[0026] The high-temperature compressor and the low-temperature compressor use 2-horsepower fixed-frequency compressors;

[0027] The condenser adopts air-cooled condenser FNH-2.9 / 8;

[0028] The filter adopts filter 083S / 9.52;

[0029] The capillary tubes are 3mm in diameter, including 0.5m high-temperature capillary tubes and 1.8m low-temperature capillary tubes.

[0030] The solenoid valve uses SV28-2 (6.35mm1 / 4 welding 220V) connected to φ6mm copper tube;

[0031] The reservoir uses 3 12.7mm tubes;

[0032] The expansion tank uses a Sihongmei liquid storage tank of 6 liters and 5HP;

[0033] The oil separator uses the AIMENDE S-4004S non-detachable oil separator;

[0034] The evaporator is made of a 10mm diameter copper tube.

[0035] The above is only a specific embodiment of the utility model, but the protection scope of the utility model is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the utility model should be included in the protection scope of the utility model. The protection scope of the utility model shall be based on the protection scope of the claims.

Claims

1. A two-stage cascade refrigeration thermostatic bath, comprising a high-temperature refrigeration system, a plate heat exchanger and a low-temperature refrigeration system, characterized in that: The plate heat exchanger is connected to the high-temperature refrigeration system and the low-temperature refrigeration system respectively; The high-temperature refrigeration system includes a high-temperature compressor, a condenser, a liquid storage tank, a filter, a capillary tube and a solenoid valve connected on the pipeline, the outlet of the plate heat exchanger is connected to the inlet of the high-temperature compressor, the outlet of the high-temperature compressor is connected to the inlet of the condenser, the outlet of the condenser is connected to the inlet of the liquid storage tank, the outlet of the liquid storage tank is connected to the inlet of the filter, the outlet of the filter is connected to the inlet of the capillary tube, a 1.2-meter capillary tube controlled by a solenoid valve is installed in parallel on the capillary tube inlet pipeline, and the outlet of the capillary tube is connected to the inlet of the plate heat exchanger; The low-temperature refrigeration system includes a filter, a capillary tube, a solenoid valve, an evaporator, an expansion tank, a low-temperature compressor and an oil separator connected on the pipeline. The outlet of the plate heat exchanger is connected to the inlet of the filter, the outlet of the filter is connected to the inlet of the capillary tube, a 1.2-meter capillary tube controlled by a solenoid valve is installed in parallel on the capillary tube inlet pipeline, the capillary tube outlet is connected to the inlet of the evaporator, the evaporator outlet is connected to the inlet of the expansion tank, the expansion tank outlet is connected to the inlet of the low-temperature compressor, the outlet of the low-temperature compressor is connected to the inlet of the oil separator, and the outlet of the oil separator is connected to the inlet of the plate heat exchanger.

2. A two-stage cascade refrigeration constant temperature bath as claimed in claim 1, characterized in that: The high-temperature compressor and the low-temperature compressor are 2-horsepower fixed-frequency compressors.

3. A two-stage cascade refrigeration constant temperature bath as claimed in claim 1, characterized in that: The high-temperature refrigeration system uses refrigerant R404A, and the low-temperature refrigeration system uses refrigerant R23.

4. A two-stage cascade refrigeration constant temperature bath as claimed in claim 1, characterized in that: The evaporator is arranged inside the constant temperature bath, and is coiled by a refrigeration copper tube, and a heater is placed at the center of the refrigeration copper tube.

5. A two-stage cascade refrigeration constant temperature bath as claimed in claim 1, characterized in that: Connect a pressure switch to the oil distribution pipeline of the low-temperature refrigeration system.

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