CN102865702A

CN102865702A - Hot gas defrost process

Info

Publication number: CN102865702A
Application number: CN 201210423057
Authority: CN
Inventors: F.张; J.张
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2008-06-27
Filing date: 2009-06-26
Publication date: 2013-01-09
Also published as: CN102077039A; WO2009158612A3; EP2313712A2; WO2009158612A2

Abstract

A hot gas defrost process is disclosed for defrosting an evaporator of a refrigeration system. In an exemplary embodiment, the hot gas defrost process includes the step of flooding at least one evaporator to be defrosted with liquid refrigerant prior to supplying a hot refrigerant vapor to the liquid flooded evaporator. In an exemplary embodiment, the hot gas process includes the step of suctioning down the refrigeration pressure within the evaporator upon termination of the supplying of the hot refrigerant vapor to the evaporator being defrosted.

Description

Hot gas defrost process

The application is that the application number that proposed on June 26th, 2009 is that the 200980124367.1(international application no is PCT/US2009/048850), denomination of invention divides an application for the patent application of " hot gas defrost process ".

The cross reference of related application

This international patent application requires in priority and the rights and interests of the U.S. Provisional Application 61/076,236 of submission on June 27th, 2008.

Technical field

The present invention generally relates to refrigeration system, relates in particular to the hot gas defrost process for the evaporator defrost of giving business-use refrigrating system.

Background technology

Business-use refrigrating system, the central refrigerating system in the supermarket for example, comprise be positioned at central authorities provide a plurality of refrigerant vapor compression machines of cold-producing medium to a plurality of evaporimeters.Usually, evaporimeter can be arranged in shop and a plurality of refrigerator display cases and even can enter cooling chamber each position relevant with reach in freezer of people; Refrigerator display case is used for the display chilled products, for example commodity, fresh poultry, fish, meat product and family's product, or frozen product, for example freezing fish, poultry, meat product, ice cream, freezing candy or other frozen product.

This class refrigeration system comprises the following basic element of character: a plurality of refrigerant vapor compression machines, at least one condenser, a plurality of evaporimeter, above-mentioned compressor, condenser and evaporimeter are connected to each other in refrigerant loop, are associated to expansion gear and each evaporator operation.In the operation, the hot compression refrigerant vapour enters refrigerant loop from compressor, and by become the condenser of heat exchange relationship with cooling medium (being generally atmosphere).By condenser the time, refrigerant vapour is condensed into liquid.Then the high pressure liquid refrigerant of temperature is assigned to a plurality of evaporimeters.Before the evaporimeter that enters separately, the highly pressurised liquid of temperature passes steam or the liquid/vapor mixture that is expanded to lower pressure with the expansion gear that is associated to evaporator operation separately and experience.The liquid of this lower temperature lower pressure or liquid/vapor mixture then flow through evaporimeter, and from the absorption of air heat, thereby air turns cold, the cold-producing medium evaporation, and wherein evaporimeter becomes heat exchange relationship with the air of the refrigeration space that is associated with evaporimeter.Like this, the low-pressure steam that leaves evaporimeter returns the suction inlet of compressor or supplies the intake manifold of a plurality of compressors.

Along with the past of time, frost and/or ice have been accumulated at the separately heat exchange coil of each evaporimeter.If described accumulation is too much, because airflow path becomes more and more restricted, can reduces so flow through the air stream of evaporimeter so, thereby cause the refrigerating capacity loss.Therefore, usually carry out the defrosting of the heat exchange coil of each evaporimeter as required or every certain hour, with thawing be accumulated on the heat exchange coil the frost and ice.The known a kind of method that is commonly used to the defrosting of the heat exchange coil of evaporimeter is hot gas defrosting.

In hot gas defrost method, the hot refrigerant vapor refrigerant of discharging from compressor is redirected to the evaporimeter that will be defrosted, rather than passes through condenser.The hot refrigerant vapor refrigerant of this changed course is the evaporimeter heat exchange coil by being defrosted in opposite direction.The frost of accumulating on the heat exchange coil and/or ice-out, the hot refrigerant vapor refrigerant cooling also was condensed into liquid before leaving evaporimeter.

Summary of the invention

On the one hand, the present invention relates to a kind of hot gas defrost process of the refrigeration system be used to having the evaporimeter that will defrost, described technique is characterised in that, in the step of using liquid refrigerant to fill the described evaporimeter that will be defrosted before described evaporimeter supply hot refrigerant vapor refrigerant.

On the one hand, the present invention relates to a kind of hot gas defrost process of the refrigeration system be used to having the evaporimeter that will be defrosted, described technology characteristics is, is stopping and then aspirating the step that reduces the refrigerant pressure in the described evaporimeter that will be defrosted after described evaporimeter supply hot refrigerant vapor refrigerant.

On the one hand, the present invention relates to a kind of hot gas defrost process for refrigeration system, described refrigeration system has condenser, at least one pair of compressor and at least one pair of evaporimeter that is arranged in the refrigerant loop, and described hot gas defrost process comprises the steps: to use liquid refrigerant to fill at least one evaporimeter that will be defrosted; To the evaporimeter supply hot refrigerant vapor refrigerant of being filled by liquid; Stopping after the evaporimeter supply hot refrigerant vapor refrigerant that will be defrosted, and then aspirating the refrigerant pressure that reduces in the evaporimeter; And refrigeration system reset to for the state with refrigerating mode operation.

On the one hand, the present invention relates to a kind of refrigeration system, comprise the condenser, at least one pair of compressor and at least one pair of evaporimeter that are arranged in the refrigerant loop, described refrigeration system can be optionally with cooling mode of operation and Defrost operation mode operation.Described refrigeration system comprises a plurality of flow control valves that are arranged in the described refrigerating circuit, and described flow control valve can optionally be positioned at open position and closed position.A layout in described a plurality of flow control valve with in the described compressor first the cold-producing medium aspiration and second cold-producing medium aspiration in the described compressor be interconnected in the refrigerant line of fluid flow communication.

In one aspect of the invention, a kind of refrigeration system, comprise the first compressor and the second compressor arranged with the parallel connection relation with respect to cold-producing medium stream, condenser, with respect to the first evaporimeter and the second evaporimeter that cold-producing medium stream is arranged with the parallel connection relation, described compressor, condenser and evaporimeter are connected in the refrigerant loop, the condenser fan that operatively is associated with condenser, with the first evaporator operation the first evaporator fan of being associated, with the second evaporator operation the second evaporator fan of being associated, with the first evaporator operation the first expansion gear of being associated and with the second evaporator operation the second expansion gear of being associated, and for the control system that refrigeration system is optionally moved with cooling mode of operation and evaporator defrost operational mode.Described control system comprises: first-class brake control valve, it is arranged in the refrigerant loop, be positioned at the first and second compressors cold-producing medium stream the downstream and be positioned at the upstream of the cold-producing medium stream of condenser; The second brake control valve, it is arranged in refrigerant loop a plurality of evaporimeters is interconnected in the first compressor suction pipeline of the first compressor suction; The 3rd flow control valve, it is arranged in such refrigerant line, and this refrigerant line extends with the position of the cold-producing medium stream upstream that be positioned at second brake control valve of parallel connection relation from the aspiration of the first compressor with respect to the cold-producing medium stream with first and second compressors; The 4th flow control valve, it is arranged in such refrigerant line, and the position of the second brake control valve upstream of this refrigerant line in the aspiration of the first compressor interconnects to the aspiration of the second compressor the aspiration of the first compressor.Described refrigeration system also comprises: the 5th flow control valve, it is arranged in the downstream of the cold-producing medium stream that is positioned at condenser and is positioned at the cold-producing medium stream of a plurality of evaporimeters in refrigerant loop upstream; The 6th flow control valve, it is arranged in the upstream of the cold-producing medium stream that is positioned at the first evaporimeter in the cold-producing medium branch line of walking around the first expansion gear; And the 7th flow control valve, it is arranged in the upstream of the cold-producing medium stream that is positioned at the second evaporimeter in the cold-producing medium branch line of walking around the second expansion gear.Described control system also comprises controller, controller function is with each opening and closing of control every flow brake control valve, control the operation of the first compressor and the second compressor, the operation of condenser fan, and control the operation of the first evaporator fan and the second evaporator fan.

Description of drawings

Fig. 1 illustrates the schematic diagram that is equipped with according to the exemplary embodiment of the refrigeration system of hot gas defrosting of the present invention system;

Fig. 2 illustrates in the refrigeration system shown in Fig. 1 each valve and other parts at the form of the state of each step of hot gas defrost process of the present invention;

Fig. 3 is the schematic diagram of the exemplary embodiment of refrigeration system shown in Fig. 1, shows the state of each valve and other parts in refrigerating mode run duration refrigeration system;

Fig. 4 is the schematic diagram of the exemplary embodiment of refrigeration system shown in Fig. 1, shows the state of each valve and other parts in the operating period of defrosting mode first step refrigeration system;

Fig. 5 is the schematic diagram of the exemplary embodiment of refrigeration system shown in Fig. 1, shows the state of each valve and other parts in the operating period of defrosting mode second step refrigeration system;

Fig. 6 is the schematic diagram of the exemplary embodiment of refrigeration system shown in Fig. 1, shows the state of each valve and other parts in the operating period of defrosting mode third step refrigeration system; And

Fig. 7 is the schematic diagram of the exemplary embodiment of refrigeration system shown in Fig. 1, shows the state of each valve and other parts in the operating period of defrosting mode the 4th step refrigeration system.

The specific embodiment

At first with reference to figure 1, show the exemplary embodiment of refrigeration system 100, comprise a pair of refrigerant

vapor compression machine

101 and 102, condenser 120 and a plurality of evaporimeter 131,132 and 133, compressor, condenser and evaporimeter are connected in the refrigerating circuit in a conventional manner.In traditional practice, each evaporimeter 131,132,133 operatively is associated with expansion gear 151,152,153 respectively.Be schematic and non-limiting purpose, each expansion gear 151,152,153 can be traditional thermostatic expansion valve.Each evaporimeter 131,132,133 also operatively is associated with evaporator fan 141,142,143 respectively, so that make to be cooled and to be supplied to climate controlled the space air by with this fan evaporimeter that becomes heat exchange relationship with cold-producing medium refrigerant loop that be associated, the space of climate controlled is such as being show area of goods showing cabinet or refrigerating chamber etc., air is cooled thus, and cold-producing medium is evaporated.The one or more condenser fans that operatively are associated with condenser 120 are set, be used for making surrounding air by with the condenser that becomes heat exchange relationship from compressor 101, the 102 thermal high cold-producing mediums of discharging, the thermal high cold-producing medium is cooled thus, and is condensed into highly pressurised liquid.

Refrigeration system 100 also comprises a plurality of

flow control valves

10,20,30,40,50,60-1 and the 60-2 that is arranged in a plurality of positions in the refrigerating circuit, in order to optionally to open or close cold-producing medium from the selected branch of its refrigerant loop that flows through.First-class brake control valve 10 is arranged in the refrigerant line 2 of refrigerant loop, be in the downstream of the cold-producing medium stream of the cold-producing medium stream point that flows out with respect to the outlet from the first compressor 101 and the second compressor 102, and be in the upstream with respect to the cold-producing medium stream of condenser 120.Second brake control valve 20 is arranged in the cold-producing medium aspiration 5, is in the upstream with respect to the cold-producing medium stream of the suction inlet of the first compressor 101.The 3rd flow control valve 30 is arranged in the refrigerant vapour pipeline 8.As shown in fig. 1, refrigerant vapour pipeline 8 extends with the position of the cold-producing medium stream upstream that be positioned at second brake control valve 20 of parallel connection relation from the aspiration 5 of the first compressor 101 with respect to the cold-producing medium stream with first and second compressors.The 4th flow control valve 40 is arranged in and flows in the aspiration 5 interconnected aspiration 6 that are communicated with the first compressor 101, aspiration 6 with follow the second compressor 102 mobile aspiration 7 fluid flow communications that are communicated with.The 5th flow control valve 50 be arranged in the interconnected refrigerant line 4 of the refrigerant outlet of condenser 120 in, the refrigerant inlet refrigerant flow communication separately of refrigerant line 4 and evaporimeter 131 and 132.The 6th flow control valve 60-1 is arranged among the 4-1 of refrigerant line branch of the 5th flow control valve 50 and evaporimeter 131 centres.The 7th flow control valve 60-2 is arranged among the 4-2 of refrigerant line branch of the 5th flow control valve 50 and evaporimeter 132 centres.Refrigerant line branch 4-1 provide the flow path of walking around expansion valve 151, and refrigerant line branch 4-2 provide the flow path of walking around expansion valve 152.Other flow control valve 80 can be arranged among the cold-producing medium branch line 4-3 of expansion valve 153 upstreams.Each aforementioned

flow control valve

10,20,30,40,50,60-1,60-2 and 80 can comprise have fluid can can't be by the closed position of valve by open position and the fluid of valve.

According to the state table of listing in the form shown in Fig. 2, selective location by a plurality of

valves

10,20,30,40,50,60-1 and 60-2 and the first compressor 101, the second compressor 102, evaporator fan 141 and 142 and the selective operation of one or more condenser fan 122, the operation of refrigeration system 100 can be transformed to defrosting mode from refrigerating mode, in refrigerating mode,

evaporimeter

131 and 132 coolings are supplied to the air in controlled temperature space, in defrosting mode, hot gas is used for to

evaporimeter

131 and 132 defrostings.Refrigeration system 100 can comprise with other parts of each aforementioned valve and system (comprise the first compressor 101 and the second compressor 102, evaporator fan 141,142 and 143 and condenser 122) controller 200 that operatively is associated, microprocessor controller for example, with the mode of operation of the location of optionally controlling each valve and each system unit, thereby implement hot gas defrost process based on the processing of the signal of the defrosting sensor 105 that operatively is associated with

corresponding evaporator

131 and 132.

In form shown in Figure 2, be to be understood that: " Comp 1 " refers to the first compressor 101; " Comp 2 " refer to the second compressor 102; " Y1 " refers to first-class brake control valve 10; " Y2 " refers to second brake control valve 20; " Y3 " refers to the 3rd flow control valve 30; " Y4 " refers to the 4th flow control valve 40; " Y5 " refers to the 5th flow control valve 50; " Y6-1 " refers to the 6th flow control valve 60-1; " Y6-2 " refers to the 7th flow control valve 60-2; " Cond Fan " refers to one or more condenser fans 122; " Evap Fan " refers to the evaporator fan 141 and 142 that is associated with

evaporimeter

131 and 132 respectively.In addition, in Fig. 3-7, the Reference numeral shown in it refers to those respective drawings and be marked at the same parts that refers among Fig. 1 and describe with reference to figure 1 in preamble.Employed in form and the whole application as shown in Figure 2, " the ON(unlatching) " mean that target component is in operation; " OFF(is closed down) " mean that target component is not in operation; " OPEN(opens) " mean that target valve is positioned to allow fluid to flow through from it; " CLOSED(closes) " mean that target valve is positioned to stop fluid to flow through from it.

Now with particular reference to Fig. 2 and 3, (moment t0 among Fig. 2) in service in the refrigeration system 100 that is in refrigerating mode, the first compressor 101 and the second compressor 102 are all opened, one or more cooler fans 122 are opened, evaporator fan 141,142 is opened,

flow control valve

10,20,50 is opened, and

flow control valve

30,40,60-1,60-2 are closed.Because flow control valve 10 is opened with flow control valve 30 and closed, pass through condenser from the first and second compressors 101, the 102 thermal high refrigerant vapours of discharging via refrigerant line 2.Because flow control valve 4 closes, the first compressor 101 is supplied flash-pot 131,132 swabbing pressure cold-producing medium by aspiration 5, and the second compressor 102 is supplied the swabbing pressure cold-producing medium of flash-pot 133 by aspiration 7.Therefore, in refrigerating mode, compressor 101,102 is disposed to the condenser 120 that shares refrigerant line 2 and share, wherein the first compressor 101, cold doubtful device 120 and evaporimeter 131,132 are connected to refrigerant flow communication in the first refrigerant circulation, and the second compressor 102, condenser 120 and evaporimeter 133 are connected to refrigerant flow communication in the second refrigerant circulation.

Now with particular reference to Fig. 2 and 4, moment t1 in step 1(Fig. 2 that refrigeration system 10 is moved with defrosting mode) in, the first compressor 101 is closed down, the second compressor 102 is opened, evaporator fan 141 and 142 is closed down, condenser fan 122 is opened, and

flow control valve

10,50,60-1,60-2 open, and

flow control valve

20,30,40 is closed.In this pattern, evaporimeter 131,132 is filled the 4-1 of branch that flows through refrigerant line 4 and walk around

expansion valve

151 and 152 and the liquid refrigerant from condenser 120 of 4-2, and flow control valve 50,60-1 and 60-2 are in its open position.

Now with particular reference to Fig. 2 and 5, in refrigeration system 10 with the moment t2 among step 2(Fig. 2 of defrosting mode operation) in, hot gas, namely from the hot refrigerant vapor refrigerant of the second compressor 102 along in the other direction by evaporimeter 131,132.In this step of defrosting mode, the first compressor 101 keeps closing down, and the second compressor 102 is opened, and one or more condenser fans 122 and evaporator fan 141,142 are all closed down,

flow control valve

10,20,40 is closed, and

flow control valve

30,50,60-1 and 60-2 open.Because flow control valve 10 is closed with flow control valve 30 and is opened, the hot refrigerant vapor refrigerant of discharging from the second compressor 102 is by refrigerant vapour pipeline 8 with by separately heat exchange surface in the evaporimeter 131,132, is accumulated in frost and ice on the evaporimeter heat exchange surface with thawing.In this step, first-class brake control valve 10 is as pressure valve.When the temperature of defrosting sensor 105 sensings that are associated with evaporimeter 131 reaches final temperature, flow control valve 60-1 will close.Similarly, when the temperature of defrosting sensor 105 sensings that are associated with evaporimeter 132 reaches final temperature, flow control valve 60-2 will close.

Now with particular reference to Fig. 2 and 6, in refrigeration system 10 with the moment t3 among step 3(Fig. 2 of defrosting mode operation) in, stop flowing of hot gas by flow control valve 30 being positioned at the closed position.In addition, flow control valve 10 and flow control valve 40 all are positioned at its open position separately.The first compressor 101 keeps closing down, and the second compressor is opened, and one or more condenser fans 122 are unlocked, and evaporator fan 141,142 keeps closing down.In this step of defrosting technique,

flow control valve

10,40,60-1,60-2 open, and

flow control valve

20,30,50 is closed.Construct like this by refrigeration system 100, the second compressor 102 extracts cold-producing medium from all evaporimeter, comprise evaporimeter 131,132 and the flow control valve 50 of closing and the refrigerant line 4 between the evaporimeter 131,132 in residual ownership cryogen.

Now with particular reference to Fig. 2 and 7, in refrigeration system 10 with the moment t4 among step 4(Fig. 2 of defrosting mode operation) in, refrigeration system 100 converts back refrigerating mode from the hot gas defrosting pattern.In this step, the second compressor 102 is held open, and the first compressor 101 becomes unlatching again.One or more condenser fans are opened.Keep closing down in the first few minutes of evaporator fan 141,142 during step 4, then become unlatching again, so that evaporimeter 131,132 moves with refrigerating mode.

Flow control valve

10,20 is opened, and

flow control valve

30,40,60-1,60-2 close.Remain on its closed position in the first few minutes of flow control valve 50 during step 4, then when evaporator fan 141,142 is opened, return its open position.When this switch process finished, the defrosting process cycles was finished, and refrigeration system 100 is returned refrigerating mode, and the positioning states of flow control valve and the mode of operation of other system unit are all reset, and move with refrigerating mode in order to refrigeration system 100.

Therefore, hot gas defrost process comprises four steps: step 1 is for to fill one or more evaporimeters that will be defrosted with liquid; Step 2 is that hot gas (hot refrigerant vapor refrigerant) is discharged to one or more evaporimeters that will be defrosted; Step 3 is drop time and the Pressure Drop swabbing pressure to the one or more evaporimeters that defrosted; Restart for refrigerating mode with step 4.The liquid of one or more evaporimeters that will be defrosted when defrosting technique begins is filled the one or more heat exchange coils that use warm refrigerant liquid to fill one or more evaporimeters that will be defrosted, and enters those coils in order to hot refrigerant vapor refrigerant.When the refrigerant line temperature of defrosting sensor 105 sensings reaches final temperature, stop hot refrigerant vapor refrigerant is discharged to one or more heat exchange coils of one or more evaporimeters that will be defrosted.At this moment, cold-producing medium is sucked out the one or more evaporimeters that defrosted, and wherein refrigerant pressure is back to swabbing pressure, and when refrigeration system 100 is returned operation in the refrigerating mode, allows liquid refrigerant to drip to guarantee not moist operation.

Claims

1. refrigeration system, comprise the condenser that is arranged in the refrigerant loop, at least one pair of compressor and at least one pair of evaporimeter, described refrigeration system can be optionally with cooling mode of operation and Defrost operation mode operation, described refrigeration system comprises a plurality of flow control valves that are arranged in the described refrigerant loop, described flow control valve can optionally be positioned at open position and closed position, described refrigeration system is characterised in that, be disposed in one of in described a plurality of flow control valves with in described at least one pair of compressor first the cold-producing medium aspiration and second cold-producing medium aspiration in described at least one pair of compressor be interconnected in the refrigerant line of fluid flow communication.

2. refrigeration system, comprise the first compressor and the second compressor arranged with the parallel connection relation with respect to cold-producing medium stream, condenser, with respect to first evaporimeter and second evaporimeter of cold-producing medium stream with parallel connection relation layout, described compressor, condenser and evaporimeter are connected in the refrigerant loop, the condenser fan that operatively is associated with condenser, with the first evaporator operation the first evaporator fan of being associated, with the second evaporator operation the second evaporator fan of being associated, with the first evaporator operation the first expansion gear of being associated and with the second evaporator operation the second expansion gear of being associated, and for the control system that refrigeration system is optionally moved with cooling mode of operation and evaporator defrost operational mode, it is characterized in that described control system comprises:

First-class brake control valve, it is arranged in the refrigerant loop, be in the first and second compressors cold-producing medium stream the downstream and be in the upstream of the cold-producing medium stream of condenser;

The second brake control valve, it is arranged in refrigerant loop a plurality of evaporimeters is interconnected in the first compressor suction pipeline of the first compressor suction;

The 3rd flow control valve, it is arranged in such refrigerant line, and this refrigerant line extends with the parallel connection relation is positioned at the cold-producing medium stream upstream of second brake control valve from the aspiration of the first compressor position with respect to the cold-producing medium stream with first and second compressors;

The 4th flow control valve, it is arranged in such refrigerant line, and this refrigerant line is positioned at second brake control valve upstream in the aspiration of the first compressor position interconnects to the aspiration of the second compressor the aspiration of the first compressor.

3. refrigeration system as claimed in claim 2 is characterized in that described control system also comprises:

The 5th flow control valve, it is arranged in the refrigerant loop, be positioned at condenser cold-producing medium stream the downstream and be positioned at the upstream of the cold-producing medium stream of a plurality of evaporimeters;

The 6th flow control valve, it is arranged in the upstream of the cold-producing medium stream that is positioned at the first evaporimeter in the cold-producing medium branch line of walking around the first expansion gear; And

The 7th flow control valve, it is arranged in the upstream of the cold-producing medium stream that is positioned at the second evaporimeter in the cold-producing medium branch line of walking around the second expansion gear.

4. refrigeration system as claimed in claim 3, it is characterized in that described control system also comprises controller, this controller function with control the first, second, third, fourth, the 5th, the 6th and the 7th flow control valve each opening and closing, control the first compressor and the second compressor operation, control condenser fan operation and control the first evaporator fan and the operation of the second evaporator fan.

5. refrigeration system as claimed in claim 4, wherein when refrigeration system is moved with refrigerating mode, described controller function is to drive the first compressor and the second compressor, condenser fan, the first and second evaporator fans, open first, second and the 5th flow control valve, and close the 3rd, the 4th, the 6th and the 7th flow control valve.

6. refrigeration system as claimed in claim 4, wherein when refrigeration system is transformed into defrosting mode from refrigerating mode, described controller function is to close down the first compressor and the first and second evaporator fans, drive the second compressor and condenser fan, open the first, the 5th, the 6th and the 7th flow control valve, and close second, third and the 4th flow control valve, thereby the first and second evaporimeters are filled liquid refrigerant.

7. refrigeration system as claimed in claim 4, wherein when refrigeration system is moved with defrosting mode, described controller function is to drive the second compressor, close down the first compressor, condenser fan and the first and second evaporator fans, open the 3rd, the 5th, the 6th and the 7th flow control valve, and close first, second and the 4th flow control valve, thereby be conducted through the first and second evaporimeters from the hot gas of the second compressor.

8. refrigeration system as claimed in claim 4, wherein when refrigeration system is moved with defrosting mode, described controller function is to drive the second compressor and condenser fan, close down the first compressor and the first and second evaporator fans, open the first, the 4th, the 6th and the 7th flow control valve, and close second, third and the 5th flow control valve, thereby be terminated to the thermal current of the first and second evaporimeters, and extract cold-producing medium out with the refrigerant pressure suction reduction the first and second evaporimeters from the first and second evaporimeters.