阅读说明：本技术 陈列柜制冷系统及其控制方法 (Showcase refrigeration system and control method thereof ) 是由 叶梓健 于 2019-12-10 设计创作，主要内容包括：本发明公开了一种陈列柜制冷系统及其控制方法。所述的陈列柜制冷系统包括冷凝机组、节流阀和至少两个并联的陈列柜,其中,在节流阀和陈列柜之间的连通管道上设有一用于调节陈列柜负荷的载冷装置。所述载冷装置包括水箱和换热器,所述水箱和所述换热器之间通过管道连通,所述管道上设有循环泵。本发明解决了超市内冷凝机组选型偏大机组频繁开停、陈列柜温度控制精度低、运行不节能的问题。(The invention discloses a showcase refrigerating system and a control method thereof. The showcase refrigerating system comprises a condensing unit, a throttle valve and at least two showcases connected in parallel, wherein a cold carrying device for adjusting the load of the showcases is arranged on a communication pipeline between the throttle valve and the showcases. The cold carrying device comprises a water tank and a heat exchanger, the water tank is communicated with the heat exchanger through a pipeline, and a circulating pump is arranged on the pipeline. The invention solves the problems of frequent start and stop of the large-size refrigerating unit in the supermarket, low temperature control precision of the display cabinet and energy-saving operation.)

1. A refrigerating system for showcase is composed of condensing unit, throttle valve and at least two parallelly-connected showcases, and features that a cold carrier for regulating the load of showcase is arranged in the pipeline between throttle valve and showcase.

2. The refrigeration system as recited in claim 1 wherein said cold carrier comprises a water tank and a heat exchanger, said water tank and said heat exchanger being in communication via a conduit, said conduit having a variable frequency circulation pump.

3. The refrigeration system of claim 2, wherein the heat exchanger of the cold carrier is of a double pipe construction, with an inner pipe carrying the coolant and an outer pipe carrying the coolant.

4. A refrigeration system according to claim 3, wherein said coolant is ethylene glycol.

5. The refrigeration system according to claim 2 wherein the tank contains water and the coolant exchanges heat with the water through the wall of the conduit, the tank having a chilled water outlet switch.

6. A control method for a display case refrigeration system, comprising the steps of:

when all the opened showcases reach the target temperature, the operation of the cold carrying device is started;

and calculating the difference value of the actual temperature of the display cabinet and the saturated steam temperature of the refrigerant corresponding to the suction pressure of the compressor, and controlling the rotating speed of the circulating pump according to the difference value.

7. The control method of claim 6, wherein the circulation pump is operated at a set minimum rotational speed when the cooling carrier is activated.

8. The control method according to claim 6, wherein when a plurality of showcases are opened, the difference is calculated with a lowest actual temperature value among all the showcases.

9. The control method according to claim 6, characterized in that the rotation speed of the circulation pump is reduced when the difference is less than a set threshold C; when the difference is larger than the set threshold value C, the rotating speed of the circulating pump is increased; when the difference is equal to the set threshold C, the circulation pump speed is kept constant.

10. The control method according to claim 9, wherein the threshold C is 10 ℃.

Technical Field

The invention relates to the technical field of refrigeration, in particular to a showcase refrigeration system for a shopping mall and a control method thereof.

Background

Malls and convenience stores are generally provided with display cabinets with refrigeration equipment. At present, a fixed-frequency compressor unit is generally adopted for the showcase, a plurality of showcases are arranged, the selection of the type is carried out according to the cooling load required by the opening of all the showcases, and the operation of the compressor unit and the showcases are mutually independently controlled and cannot be accurately controlled. In summary, the following problems exist in the prior art:

1. when only one or more show cabinets are used, the phenomenon of 'large horse-drawn trolley' that the outer machine is larger and the inner machine is smaller can occur, and finally the condensation unit is frequently started and stopped, and energy is wasted;

2. the condensing unit and the display cabinet run independently, and the unit control system cannot accurately control the temperature of the display cabinet.

Disclosure of Invention

The invention provides a market display cabinet refrigerating system and a control method thereof, which aim to solve the problems that in the prior art, the load of a condensing unit cannot be adjusted according to the number of opened display cabinets, so that the condensing unit is frequently started and stopped, and the display cabinets cannot be accurately controlled.

In order to solve the technical problem, the invention provides a showcase refrigerating system which comprises a condensing unit, a throttle valve and at least two showcases connected in parallel, wherein a refrigerating device for adjusting the load of the showcases is arranged on a communication pipeline between the throttle valve and the showcases.

The cold carrying device comprises a water tank and a heat exchanger, the water tank is communicated with the heat exchanger through a pipeline, and a variable frequency circulating pump is arranged on the pipeline.

Preferably, the heat exchanger of the cold carrying device adopts a sleeve structure, the inner pipe carries the refrigerant, and the outer pipe carries the refrigerant.

Preferably, the refrigerating medium adopts ethylene glycol.

Preferably, the water tank is filled with water, the secondary refrigerant exchanges heat with the water through the pipe wall, and the water tank is provided with a chilled water outlet switch.

The invention also provides a control method for the showcase refrigeration system, which comprises the following steps:

when all the opened showcases reach the target temperature, the operation of the cold carrying device is started; at the moment, the circulating pump is started at the set lowest rotating speed;

and calculating the difference value of the actual temperature of the display cabinet and the saturated steam temperature of the refrigerant corresponding to the suction pressure of the compressor, and controlling the rotating speed of the circulating pump according to the difference value.

When a plurality of showcases are opened, the difference is calculated by the lowest actual temperature value among all the showcases.

When the difference is smaller than a set threshold value C, the rotating speed of the circulating pump is reduced; when the difference is larger than the set threshold value C, the rotating speed of the circulating pump is increased; when the difference is equal to the set threshold C, the circulation pump speed is kept constant.

Preferably, the threshold value C is 10 ℃.

Compared with the prior art, the invention has the following beneficial effects:

1. the problem that the unit cannot be normally returned to the oil compressor and burnt out due to frequent start of the unit caused by large type selection of the condensing unit when the number of the overtime showcases is small is solved.

2. The control of the condensing unit and the display cabinet are mutually related and are adjusted through the cold carrying device, so that the temperature control precision of the display cabinet is improved.

Drawings

Fig. 1 is a schematic view of a refrigeration system according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings and examples. It should be understood that the following specific examples are only for illustrating the present invention and are not to be construed as limiting the present invention.

Supermarkets have a large number of refrigerated display cases for holding perishable foods. The showcase needs the refrigeration of the condensing unit to provide cold. When the showcase is fully opened, a refrigerant enters the compressor and is compressed into high-temperature and high-pressure gas, the gas is exhausted and then enters the condenser for cooling, the condensed high-pressure liquid enters the throttle valve for pressure reduction, the reduced low-temperature and low-pressure liquid enters the heat exchanger in the showcase to exchange heat with the air in the showcase, and then the low-temperature and low-pressure liquid returns to the compressor through the air suction pipe for circulation. Because of the existence of a plurality of show cases, the liquid pressure after throttling needs to ensure long-distance liquid supply.

Because the condensing unit adopts a mode of driving a plurality of units, although a part of the display cabinets can be closed under certain conditions and cold energy does not need to be provided, the unit type selection must be selected according to the cold energy needed when a plurality of display cabinets are fully opened. When only a part of the showcase needs to be opened, energy waste is caused, and the frequent opening and closing of the unit has a bad effect on the operation of the unit.

As shown in fig. 1, the present invention provides a market showcase refrigerating system, which comprises a condensing unit consisting of a compressor 11, a four-way valve 12 and a condenser 13; the throttle valve 2 can adopt electronic expansion valves, thermal expansion valves or capillary tubes and other throttle components; and a plurality of showcases 3 connected in parallel (5 showcases 31 to 35 in this embodiment); a cold carrier for adjusting the load of the showcase is arranged between the throttle valve and the showcase. The cold carrying device comprises a water tank 5 and a heat exchanger, the water tank and the heat exchanger are communicated through a pipeline 6, and a circulating pump 7 is arranged on the pipeline.

In a preferred embodiment, the heat exchanger adopts a sleeve structure, a sleeve 8 is arranged at the position of the refrigerant communication pipeline 4 between the throttle valve and the display cabinet, the inner pipe carries the refrigerant, the outer pipe carries the secondary refrigerant, and the secondary refrigerant exchanges heat with the refrigerant through the wall of the inner pipe.

Because the condensing unit adopts a one-driving-more mode, and a part of display cabinets can be closed under certain conditions, and refrigeration is not started, the maximum type selection is carried out according to a plurality of display cabinets in a single machine during the type selection. The showcase number is set on the showcase display panel, 1, 2, 3, and 4 … … are set for each showcase from small to large, and a desired target temperature value is set (for example, the target temperature of the showcase is 4 ℃). The air suction port of the compressor is provided with a low-pressure sensor for detecting the air suction pressure. The pipeline from the outlet of the throttle valve 2 to the showcase 3 adopts a pipe sleeve mode, a refrigerant of a refrigeration system is led in a small pipe, and a secondary refrigerant such as ethylene glycol is led in a large pipe. The water tank 5 is filled with water, and the secondary refrigerant exchanges heat with the water in the water tank through the wall of the pipeline. The circulating pump 7 adopts a variable frequency pump, when one or a few showcases are opened, the suction pressure is detected, and the rotating speed of the circulating pump is controlled by the difference value of the actual temperature of the refrigerant in the showcases and the saturated steam temperature of the refrigerant corresponding to the suction pressure of the compressor.

When the cold quantity is excessive, the cold carrying device is started, the cold medium exchanges heat with the secondary cold medium flowing into the large pipe from the water tank in advance before entering the showcase heat exchanger through the copper pipe wall, a part of cold quantity is stored, the load required by the condensing unit and the showcase can reach a matching state at any time, and the phenomenon that the condensing unit stops due to the fact that the cold quantity of the condensing unit is too large and the showcase reaches the set target temperature is avoided.

The water tank 5 can be provided with a water outlet switch to introduce chilled water into a required place for use, such as using cold energy for indoor cooling through a fan coil, or other places requiring cold energy.

In the invention, the control method of the cold carrying device is as follows:

step 1, at the initial stage of opening the showcase, the cold carrying device does not operate. When all the opened showcases reach the set target temperature, the operation of the cold carrying device is started, and at the moment, the circulating pump is started at the set lowest rotating speed;

and 2, detecting the actual temperature in the display cabinet in real time, calculating the difference value between the actual temperature of the display cabinet and the refrigerant saturated steam temperature corresponding to the suction pressure of the compressor, and controlling the rotating speed of the circulating pump according to the difference value. When a plurality of showcases are opened, the difference is calculated by the lowest actual temperature value among all the showcases.

When the difference is smaller than a set threshold value C (for example, 10 ℃), the heat exchange temperature difference is small, the refrigerant is completely evaporated and begins to overheat in the display cabinet, and at the moment, the cold quantity is insufficient, the rotating speed of the circulating pump needs to be reduced, so that the quantity of the secondary refrigerant exchanging heat with the refrigerant in the large pipe is reduced; when the difference value is larger than the set threshold value C, the heat exchange temperature difference is large, the refrigerant does not completely exchange heat in the display cabinet, and the refrigerant still flows in a gas-liquid two-phase flow at the outlet, so that the surplus of cold energy is shown, the rotating speed of the coolant pump needs to be increased, and the quantity of the coolant exchanging heat with the refrigerant in the large pipe is increased; when the difference is equal to the set threshold value C, the cold quantity is matched with the load in the display cabinet, and the rotating speed of the circulating pump is kept unchanged.

If the display cases are all on at the same time, the circulation pump need not be turned on.

The technical scheme provided by the invention solves the problems that a condensing unit is frequently started and stopped when the supermarket display cabinet is not fully opened, the temperature control precision is low, and the operation is not energy-saving.

The foregoing is considered as illustrative only of the embodiments of the invention. It should be understood that any modifications, equivalents and changes made within the spirit and framework of the inventive concept are intended to be included within the scope of the present invention.