阅读说明：本技术 一种冷藏集装箱除霜系统及除霜方法 (Defrosting system and defrosting method for refrigerated container ) 是由 花开太 梁飞 于 2020-04-30 设计创作，主要内容包括：本发明属于冷藏集装箱除霜领域,涉及一种冷藏集装箱除霜系统及除霜方法。所述冷藏集装箱除霜系统包括箱体、蒸发器、热空气进口、热空气出口、箱内送风口、箱内回风口、控制系统以及开关执行元件,蒸发器设置于箱体顶部的内壁上且蒸发器处设置有风机,热空气进口和热空气出口分别设置于箱体后壁的上部和下部且分别位于蒸发器的两侧,箱内回风口和箱内送风口分别设置于箱体前壁的上部和下部且分别位于蒸发器的两侧,控制系统通过控制开关执行元件启动/解除除霜模式。本发明采用空气除霜技术,能够提高除霜效率,降低除霜能耗,减少冷藏集装箱箱内温度波动。(The invention belongs to the field of defrosting of refrigerated containers, and relates to a defrosting system and a defrosting method for a refrigerated container. The defrosting system of the refrigerated container comprises a box body, an evaporator, a hot air inlet, a hot air outlet, an in-box air supply outlet, an in-box air return inlet, a control system and a switch execution element, wherein the evaporator is arranged on the inner wall of the top of the box body, a fan is arranged at the position of the evaporator, the hot air inlet and the hot air outlet are respectively arranged at the upper part and the lower part of the rear wall of the box body and are respectively positioned at two sides of the evaporator, the in-box air return inlet and the in-box air supply outlet are respectively arranged at the upper part and the lower part of the front wall of the box body and are respectively positioned at two sides of the evaporator, and the. The invention adopts the air defrosting technology, can improve the defrosting efficiency, reduce the defrosting energy consumption and reduce the temperature fluctuation in the refrigerated container.)

1. The utility model provides a frozen products insulated container defrost system, its characterized in that, frozen products insulated container defrost system includes box, evaporimeter, hot-air inlet, hot-air outlet, incasement supply-air outlet, incasement return air inlet, control system and switch executive component, the evaporimeter sets up on the inner wall at box top and evaporimeter department is provided with the fan, hot-air inlet and hot-air outlet set up respectively in the upper portion and the lower part of box back wall and are located the both sides of evaporimeter respectively, incasement return air inlet and incasement supply-air outlet set up respectively in the upper portion and the lower part of box antetheca and are located the both sides of evaporimeter respectively, switch executive component is used for controlling opening and closing of hot-air inlet, hot-air outlet, incasement supply-air outlet and incasement return air inlet, control system starts/removes the defrost mode through control switch executive component.

2. A refrigerated container defrost system as recited in claim 1 further comprising an inlet air temperature sensor and an outlet air temperature sensor, said inlet air temperature sensor and said outlet air temperature sensor being disposed on a leeward side and a windward side of the evaporator respectively for monitoring a temperature difference across the evaporator, said temperature difference data being transmitted to the control system, said control system activating/deactivating the defrost mode by controlling the switch actuator based on the temperature difference data.

3. A refrigerated container defrost system as recited in claim 1 further comprising a pressure differential sensor for monitoring the pressure differential between the windward and leeward sides of the evaporator, the pressure differential data being transmitted to a control system which activates/deactivates the defrost mode by controlling the switch actuator based on the pressure differential data.

4. A refrigerated container defrost system as recited in claim 1 further comprising an inlet air temperature sensor and an outlet air temperature sensor disposed on a leeward side and a windward side of the evaporator respectively for monitoring a temperature difference across the evaporator and a pressure differential sensor for monitoring a pressure differential across the windward side and the leeward side of the evaporator; the temperature difference and pressure difference data are transmitted to a control system, and the control system controls a switch actuator to start/stop a defrosting mode according to the data of the two aspects.

5. A refrigerated container defrost system as claimed in any one of claims 1-4 wherein the opening heights of said hot air inlet and hot air outlet are substantially equal and the distance between them is at least 5 times the opening height.

6. A refrigerated container defrost system as claimed in claims 1-4 wherein the open and closed states of said hot air inlet, hot air outlet, in-box supply air outlet and in-box return air inlet are detected and fed back by a stop.

7. A method of defrosting using the refrigerated container defrosting system of any of claims 1 to 6.

8. The defrost method of claim 7 wherein when said refrigerated container defrost system further includes a pressure differential sensor for monitoring a pressure differential between a windward side and a leeward side of the evaporator, determining a pressure differential pressure to determine a defrost condition is based on: in a refrigeration mode, by measuring the air output of an air supply outlet in a refrigeration container, when the air output is reduced by 50% compared with that in a frostless state, recording the collected air pressure difference value as a calibration value for triggering refrigeration defrosting conditions; in the freezing mode, the air supply quantity of an air supply outlet in the refrigerated container is measured, and when the air supply quantity is reduced by 65% compared with that in a frost-free state, the collected air pressure difference value is recorded and used as a calibration value for triggering freezing and defrosting conditions.

9. The defrosting method according to claim 8, wherein when the defrosting system for the refrigerated container further comprises an inlet air temperature sensor and an outlet air temperature sensor respectively provided at a leeward side and a windward side of the evaporator, and a pressure difference sensor for monitoring a pressure difference between the windward side and the leeward side of the evaporator, the defrosting condition is determined according to the temperature difference and the pressure difference of the wind pressure according to the following conditions:

(1) and (3) defrosting control in a refrigeration mode:

the control system collects data of the air inlet temperature sensor, the air outlet temperature sensor and the pressure difference sensor in real time, and when the difference value of the air inlet temperature sensor and the air outlet temperature sensor is more than or equal to 4 ℃, the data are stabilized for 5-15 minutes and used as temperature difference to judge defrosting conditions; simultaneously setting real-time value P of differential pressure sensor_sAnd a determination value P required for defrosting operation_p50％Making a comparison when P_s≥P_p50％When the evaporator is frosted seriously, the defrosting operation needs to be started, and a dead zone needs to be designed in consideration of the stability of control, namely when P is_s≥P_p50％Stabilizing for 5-15 min to judge defrosting condition as wind pressure difference; when the temperature difference judgment defrosting condition and the wind pressure difference judgment defrosting condition are simultaneously met, starting a defrosting mode;

(2) freezing mode defrosting control:

the control system collects data of the air inlet temperature sensor, the air outlet temperature sensor and the pressure difference sensor in real time, and when the difference value of the air inlet temperature sensor and the air outlet temperature sensor is more than or equal to 6 ℃, the data are stabilized for 5-15 minutes and used as temperature difference to judge defrosting conditions; simultaneously setting real-time value P of differential pressure sensor_sAnd a determination value P required for defrosting operation_p65％Making a comparison when P_s≥P_p65％When the evaporator is frosted seriously, the defrosting operation needs to be started, and a dead zone needs to be designed in consideration of the stability of control, namely when P is_s≥P_p65％Stabilizing for 5-15 min to judge defrosting condition as wind pressure difference; and when the defrosting condition is judged by the temperature difference and the defrosting condition is judged by the air pressure difference, the defrosting mode is started.

10. The defrost method of any one of claims 7-9 wherein when the refrigerated container defrost system further includes an inlet air temperature sensor and an outlet air temperature sensor disposed on a leeward side and a windward side of the evaporator, respectively, and a pressure differential sensor for monitoring a pressure differential between the windward side and the leeward side of the evaporator, the exit defrost condition is determined based on the temperature differential and the pressure differential as follows:

(1) and (3) exiting the defrosting control in the refrigerating mode:

the control system collects data of the air inlet temperature sensor, the air outlet temperature sensor and the pressure difference sensor in real time, and when the difference value between the air inlet temperature sensor and the air outlet temperature sensor is less than or equal to 2 ℃, the data are stabilized for 4-6 minutes and used as temperature difference to judge whether the defrosting mode is exited; simultaneously setting real-time value P of differential pressure sensor_sThe value P of the pressure difference sensor in the frostless state of the evaporator_bMaking a comparison when P_b≤P_s≤1.05*P_bStabilizing for 4-6 min as the wind pressure difference to judge the condition of exiting the defrosting mode; when the condition of judging whether to exit the defrosting mode by the temperature difference and the condition of judging whether to exit the defrosting mode by the air pressure difference are simultaneously met, exiting the defrosting mode;

(2) and (3) exiting the defrosting control in the freezing mode:

the control system collects data of the air inlet temperature sensor, the air outlet temperature sensor and the pressure difference sensor in real time, and when the difference value between the air inlet temperature sensor and the air outlet temperature sensor is less than or equal to 2 ℃, the control system is used as temperature difference to judge whether the defrosting mode is exited; simultaneously setting real-time value P of differential pressure sensor_sThe value P of the pressure difference sensor in the frostless state of the evaporator_bMaking a comparison when P_b≤P_s≤1.05*P_bStabilizing for 4-6 min as the wind pressure difference to judge the condition of exiting the defrosting mode; and when the condition of judging whether to exit the defrosting mode by the temperature difference and the condition of judging whether to exit the defrosting mode by the air pressure difference are simultaneously met, exiting the defrosting mode.

Technical Field

The invention belongs to the field of defrosting of refrigerated containers, and particularly relates to a defrosting system and a defrosting method for a refrigerated container.

Background

At present, the mainstream brand refrigerated container manufacturers (such as us keli, kaiwang, japan gold, danish marsky starcool, and the like) in the market adopt the defrosting technology which is more traditional, and generally use the defrosting technology of electric heating defrosting and hot air defrosting. The defrosting technology is usually slow in defrosting speed in the actual work of the refrigerated container, a complete defrosting process generally needs 40-60 minutes or even longer (according to the frosting degree), the defrosting energy consumption is high, and a high-power electric heating rod needs to be equipped. If the electric heating defrosting and the hot gas defrosting are combined for use, a defrosting system is more complex, a related defrosting auxiliary valve needs to be additionally arranged, a refrigerating unit needs to be started to operate during defrosting, a compressor operates in a hot gas defrosting mode, the risk of wet stroke is increased, a liquid impact phenomenon can be caused when the compressor is serious, and great potential safety hazards are caused to the compressor. Meanwhile, during defrosting, the system is high in energy consumption, and energy required by defrosting is completely driven and converted through electric energy. The existing defrosting system of the refrigerated container has long defrosting time, and a boundary part between the evaporator and the goods storage of the refrigerated container does not adopt a heat insulation material, so that part of heat for defrosting is also transferred to the goods in radiation, convection and other modes, and the temperature of the goods is increased. Therefore, under the combined action of external environment heat infiltration, the self-breathing heat capacity of the goods and partial defrosting heat, the temperature in the box fluctuates greatly in a long defrosting time, and the transported goods are also seriously damaged. Additionally, from a defrost control perspective, refrigerated containers currently on the market commonly employ temperature-time or time controlled defrost. The method for defrosting by adopting temperature-time control comprises the steps of arranging a temperature sensor on the tube wall of an outlet of an evaporator, entering a defrosting mode after refrigerating/freezing for a period of time (usually 4-5 hours), detecting the temperature on the tube wall of the outlet of the evaporator by the temperature sensor in the defrosting process, indicating that defrosting is finished when the temperature is reduced to about 15 ℃, and switching back to the refrigerating/freezing mode again. And the method of using time control defrosting is to automatically enter a defrosting mode after a fixed time (usually 4-5 hours) of refrigeration/freezing and switch back to the refrigeration/freezing mode again after defrosting is completed (usually 40-60 minutes). However, the phenomena of wrong defrosting and frequent defrosting often occur by adopting the two modes to control defrosting, so that the energy consumption of the refrigerating unit of the refrigerated container is increased, and the service life of the refrigerating unit is also shortened. The statistical data for the failure of 4318 refrigerated containers in 5 year operation, as tracked by the Shanghai refrigerated container carrier, shows: the defrost failure rate of the evaporator is ranked first.

Disclosure of Invention

The invention aims to solve the problem of high defrosting energy consumption when the conventional refrigerated container is used for defrosting by arranging an electric heating rod, and provides a refrigerated container defrosting system and a defrosting method with low defrosting energy consumption.

The defrosting system comprises a box body, an evaporator, a hot air inlet, a hot air outlet, an in-box air supply outlet, an in-box air return opening, a control system and a switch execution element, wherein the evaporator is arranged on the inner wall of the top of the box body, a fan is arranged at the evaporator, the hot air inlet and the hot air outlet are respectively arranged at the upper part and the lower part of the rear wall of the box body and are respectively positioned at two sides of the evaporator, the in-box air return opening and the in-box air supply outlet are respectively arranged at the upper part and the lower part of the front wall of the box body and are respectively positioned at two sides of the evaporator, the switch execution element is used for controlling the opening and closing of the hot air inlet, the hot air outlet, the in-box air supply outlet and the in-box air return opening, and the control system is started/released from a defrosting mode.

Furthermore, the defrosting system of the refrigerated container further comprises an air inlet temperature sensor and an air outlet temperature sensor, wherein the air inlet temperature sensor and the air outlet temperature sensor are respectively arranged on the leeward side and the windward side of the evaporator and used for monitoring the temperature difference between the two sides of the evaporator, the temperature difference data are transmitted to the control system, and the control system starts/releases the defrosting mode through a control switch execution element according to the temperature difference data.

Furthermore, the defrosting system of the refrigerated container also comprises a differential pressure sensor used for monitoring the pressure difference between the windward side and the leeward side of the evaporator, the pressure difference data is transmitted to a control system, and the control system starts/releases a defrosting mode through a control switch execution element according to the pressure difference data.

The defrosting system of the refrigerated container further comprises an air inlet temperature sensor, an air outlet temperature sensor and a pressure difference sensor, wherein the air inlet temperature sensor and the air outlet temperature sensor are respectively arranged on the leeward side and the windward side of the evaporator and used for monitoring the temperature difference between the two sides of the evaporator, and the pressure difference sensor is used for monitoring the pressure difference between the windward side and the leeward side of the evaporator; the temperature difference and pressure difference data are transmitted to a control system, and the control system controls a switch actuator to start/stop a defrosting mode according to the data of the two aspects.

Further, the control system adopts a P L C controller.

Further, the opening heights of the hot air inlet and the hot air outlet are substantially equal, and the distance between the two is at least 5 times the opening height.

Further, the evaporator is arranged in an inclined mode, and the inclination angle is 30-60 degrees.

Furthermore, the opening and closing states of the hot air inlet, the hot air outlet, the in-box air supply outlet and the in-box air return inlet are detected and fed back through the limiting device.

The invention also provides a defrosting method by adopting the defrosting system for the refrigerated container.

Further, when the defrosting system of the refrigerated container further comprises a pressure difference sensor for monitoring the pressure difference between the windward side and the leeward side of the evaporator, the defrosting condition is judged by determining the pressure difference of the wind pressure according to the following modes: in a refrigeration mode, by measuring the air output of an air supply outlet in a refrigeration container, when the air output is reduced by 50% compared with that in a frostless state, recording the collected air pressure difference value as a calibration value for triggering refrigeration defrosting conditions; in the freezing mode, the air supply quantity of an air supply outlet in the refrigerated container is measured, and when the air supply quantity is reduced by 65% compared with that in a frost-free state, the collected air pressure difference value is recorded and used as a calibration value for triggering freezing and defrosting conditions.

Further, work as the refrigerated container defrost system is still including setting up respectively in the air inlet temperature sensor and the air-out temperature sensor of the leeward side and the windward side of evaporimeter to and be used for monitoring the evaporimeter windward side and during the differential pressure sensor of leeward side differential pressure, confirm the difference in temperature and the judgement defrosting condition of wind pressure differential pressure according to following condition:

(1) and (3) defrosting control in a refrigeration mode:

the control system collects data of the air inlet temperature sensor, the air outlet temperature sensor and the pressure difference sensor in real time, and the data are used as the air inlet temperature sensor and the air outlet temperature sensorWhen the difference value is more than or equal to 4 ℃, stabilizing for 5-15 minutes, and judging defrosting conditions as temperature difference; simultaneously setting real-time value P of differential pressure sensor_sAnd a determination value P required for defrosting operation_p50％Making a comparison when P_s≥P_p50％When the evaporator is frosted seriously, the defrosting operation needs to be started, and a dead zone needs to be designed in consideration of the stability of control, namely when P is_s≥P_p50％Stabilizing for 5-15 min to judge defrosting condition as wind pressure difference; when the temperature difference judgment defrosting condition and the wind pressure difference judgment defrosting condition are simultaneously met, starting a defrosting mode;

(2) freezing mode defrosting control:

the control system collects data of the air inlet temperature sensor, the air outlet temperature sensor and the pressure difference sensor in real time, and when the difference value of the air inlet temperature sensor and the air outlet temperature sensor is more than or equal to 6 ℃, the data are stabilized for 5-15 minutes and used as temperature difference to judge defrosting conditions; simultaneously setting real-time value P of differential pressure sensor_sAnd a determination value P required for defrosting operation_p65％Making a comparison when P_s≥P_p65％When the evaporator is frosted seriously, the defrosting operation needs to be started, and a dead zone needs to be designed in consideration of the stability of control, namely when P is_s≥P_p65％Stabilizing for 5-15 min to judge defrosting condition as wind pressure difference; and when the defrosting condition is judged by the temperature difference and the defrosting condition is judged by the air pressure difference, the defrosting mode is started.

Further, when the refrigerated container defrosting system further comprises an air inlet temperature sensor and an air outlet temperature sensor which are respectively arranged on the leeward side and the windward side of the evaporator, and a pressure difference sensor for monitoring the pressure difference between the windward side and the leeward side of the evaporator, the defrosting condition is determined to be exited according to the following conditions:

(1) and (3) exiting the defrosting control in the refrigerating mode:

the control system collects data of the air inlet temperature sensor, the air outlet temperature sensor and the pressure difference sensor in real time, and when the difference value between the air inlet temperature sensor and the air outlet temperature sensor is less than or equal to 2 ℃, the data are stabilized for 4-6 minutes and used as temperature difference to judge whether the defrosting mode is exited; while sensing differential pressureReal-time value P of device_sThe value P of the pressure difference sensor in the frostless state of the evaporator_bMaking a comparison when P_b≤P_s≤1.05*P_bStabilizing for 4-6 min as the wind pressure difference to judge the condition of exiting the defrosting mode; when the condition of judging whether to exit the defrosting mode by the temperature difference and the condition of judging whether to exit the defrosting mode by the air pressure difference are simultaneously met, exiting the defrosting mode;

(2) and (3) exiting the defrosting control in the freezing mode:

the control system collects data of the air inlet temperature sensor, the air outlet temperature sensor and the pressure difference sensor in real time, and when the difference value between the air inlet temperature sensor and the air outlet temperature sensor is less than or equal to 2 ℃, the control system is used as temperature difference to judge whether the defrosting mode is exited; simultaneously setting real-time value P of differential pressure sensor_sThe value P of the pressure difference sensor in the frostless state of the evaporator_bMaking a comparison when P_b≤P_s≤1.05*P_bStabilizing for 4-6 min as the wind pressure difference to judge the condition of exiting the defrosting mode; and when the condition of judging whether to exit the defrosting mode by the temperature difference and the condition of judging whether to exit the defrosting mode by the air pressure difference are simultaneously met, exiting the defrosting mode.

The invention adopts the air defrosting technology, improves partial structure of the existing refrigerated container, and is additionally provided with the hot air inlet and the hot air outlet to realize air defrosting, only a fan needs to operate (with low power) during defrosting, a compressor and other equipment do not need to be started, the defrosting energy consumption is low, a free heat source contained in high-temperature air in the environment can be fully utilized, the heat source is stable, the fan has large discharge capacity, the defrosting speed is high, the efficiency is high, and meanwhile, the temperature fluctuation in the refrigerated container can be reduced. On the basis, a defrosting control method matched with the temperature difference value and the air pressure difference value is preferably further designed, the problem of wrong defrosting of the refrigerated container is solved in a mode of mutually coupling the temperature difference value and the air pressure difference value, and intelligent defrosting is realized.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a front view of a refrigerated container defrost system;

FIG. 2 is a side view of a refrigerated container defrost system;

fig. 3 is a circuit diagram of a refrigerated container defrost system.

Description of the reference numerals

1-a box body; 2-an evaporator; 3, a fan; 4-hot air inlet; 5-hot air outlet; 6-an air supply outlet in the box; 7-an in-box air return port; 8-differential pressure sensor; 9-air intake temperature sensor; 10-return air temperature sensor.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

In the present invention, unless otherwise specified, the use of directional terms such as "top, bottom, front and rear" generally refer to the orientation of the refrigerated container defrost system of the present invention under operating conditions, i.e., as shown in the drawings.

As shown in fig. 1 and 2, the defrosting system for a refrigerated container according to the present invention comprises a box body 1, an evaporator 2, a hot air inlet 4, a hot air outlet 5, an in-box supply air outlet 6, an in-box return air inlet 7, a control system and a switch actuator, wherein the evaporator 2 is disposed on an inner wall of a top of the box body 1, a fan 3 is disposed at the evaporator 2, the hot air inlet 4 and the hot air outlet 5 are disposed at an upper portion and a lower portion of a rear wall of the box body 1, respectively, and are disposed at both sides of the evaporator 2, the in-box return air inlet 7 and the in-box supply air outlet 6 are disposed at an upper portion and a lower portion of a front wall of the box body 1, respectively, and are disposed at both sides of the evaporator 2, the switch actuator is used for controlling opening and closing of the hot air inlet 4, the hot air outlet 5, the in-box supply air outlet 6, and the in-box return air inlet 7, and the control system is activated/deactivated in a defrosting mode by controlling the switch actuator, wherein the control system preferably employs.

According to a preferred embodiment of the invention, the hot air inlet 4 and the hot air outlet 5 are substantially equal in opening height and are at least 5 times as long as the opening height, in which case short-circuiting of the air flow in the external environment is prevented.

The refrigeration container refrigeration system can be operated in two modes, one mode being a refrigeration mode and the other mode being a defrost mode. When the refrigerating unit of the refrigerated container is in a refrigerating mode, the hot air inlet 4 and the hot air outlet 5 of the defrosting system of the refrigerated container are in a closed state, the air supply outlet 6 in the refrigerator and the air return inlet 7 in the refrigerator are in an open state, and the refrigerating unit carries out refrigerating operation according to the refrigerating mode. When the refrigerating unit of the refrigerated container is in a defrosting mode, a hot air inlet 4 and a hot air outlet 5 of the defrosting system of the refrigerated container are in an opening state, an in-box air supply outlet 6 and an in-box air return inlet 7 are in a closing state, and the refrigerating unit carries out defrosting operation according to the defrosting mode. The defrosting principle of the refrigerated container defrosting system is that high-temperature air in an introduced environment flows through the refrigerated container evaporator, and the air after heat exchange is discharged from the hot air outlet, so that the heat exchange is carried out on the surface, the inside and the back of the evaporator of the refrigerated container, the temperature of the evaporator rises, and a frost layer on the surface of the evaporator melts.

The defrosting system of the refrigerated container provided by the invention is mainly improved in that the existing electric heating rod electric heating defrosting is replaced by air heat exchange defrosting, only a fan is started, a compressor and other equipment are closed in the defrosting process, and the defrosting condition judgment mode can be the same as that of the prior art, for example, time control defrosting can be adopted. And automatically entering a defrosting mode after refrigerating/freezing for 4-5 hours, automatically exiting the defrosting mode after defrosting for 40-60 minutes, and switching back to the refrigerating/freezing mode.

The air channel is blocked due to frosting of the evaporator 2, the air channel is more and more seriously blocked along with the increase of a frost layer, the temperature of an air inlet of the evaporator is gradually increased, if the air outlet temperature is controlled by the controller to be stable near the set temperature in a refrigeration mode of the refrigerated container, the air return temperature is controlled by the controller to be stable near the set temperature in a refrigeration mode, and the air outlet temperature is further reduced. The difference in the inlet and outlet temperatures of the hot air in the evaporator 2 will be continuously increased. Furthermore, an increase in the thickness of the frost layer reduces the flow of air through the evaporator 2, resulting in an increase in the pressure difference across the windward and windward sides of the evaporator 2. Therefore, the severity of the evaporator frost layer can be evaluated in terms of both the temperature difference and the wind pressure difference as trigger conditions for start/defrost release.

According to a preferred embodiment of the present invention, the defrosting system for the refrigerated container further comprises an inlet air temperature sensor 9 and an outlet air temperature sensor 10, wherein the inlet air temperature sensor 9 and the outlet air temperature sensor 10 are respectively disposed on the leeward side and the windward side of the evaporator 2 for monitoring the temperature difference between the two sides of the evaporator 2, the temperature difference data is transmitted to a control system, and the control system starts/releases the defrosting mode through a control switch execution element according to the temperature data; or, the refrigerated container defrosting system also comprises a differential pressure sensor 8 for monitoring the pressure difference between the windward side and the leeward side of the evaporator 2, the differential pressure data is transmitted to a control system, and the control system starts/releases the defrosting mode through a control switch execution element according to the pressure data.

According to the most preferred embodiment of the present invention, the defrosting system for a refrigerated container further comprises an inlet air temperature sensor 9, an outlet air temperature sensor 10 and a pressure difference sensor 8, wherein the inlet air temperature sensor 9 and the outlet air temperature sensor 10 are respectively disposed on the leeward side and the windward side of the evaporator 2 for monitoring the temperature difference between the windward side and the leeward side of the evaporator 2, the pressure difference sensor 8 is used for monitoring the pressure difference between the windward side and the leeward side of the evaporator 2, the temperature difference and the pressure difference data are transmitted to a control system, and the control system controls the switch actuator to start/release the defrosting mode according to the data of the two aspects, at this time, the dynamic monitoring of the pressure difference between the windward side and the leeward side of the evaporator and the inlet air temperature and outlet temperature difference of the evaporator is adopted, the air pressure difference and the temperature difference are mutually coupled through the air pressure difference and the temperature difference, the accuracy of the evaporator defrosting thickness evaluation is improved, the problem that the temperature sensor and the pressure difference sensor itself and the influence of the cargo loading mode on the air flow resistance are prevented from misjudgment is caused by the air flow is adopted, the hot air inlet 4, the hot air outlet 5, the in the container, the hot air outlet 6 and the container is controlled by the heat sensor 2, the air outlet, the air inlet of the refrigeration system is controlled by the refrigeration system to be closed, the refrigeration system is controlled by the cooling control circuit 3, the refrigeration system is controlled by the refrigeration system, the refrigeration system is controlled by the refrigeration system by.

In the working process of the defrosting mode of the refrigerated container defrosting system, the pressure difference sensor 8, the air inlet temperature sensor 9 and the air outlet temperature sensor 10 are cooperatively responsible for monitoring the frosting degree of the evaporator, before the refrigerated container is put into use, the evaporator is in a frostless state, the air pressure difference value of the windward space and the leeward space of the evaporator is collected by the P L C controller to be used as the reference value of the frostless state of the evaporator, and after the refrigerated container runs normally, the possible filth blockage influence of the evaporator is considered, the maintenance and correction can be carried out regularly, and the pressure difference sensor 8 can be ensured to truly and accurately reflect the filth blockage state of the evaporator 2.

According to a preferred embodiment of the present invention, the determination value of the wind pressure difference at the time of defrosting is determined as follows: because the refrigerated containers are generally produced in batches and the design of the evaporators of the refrigerated containers is the same, the defrosting air pressure difference value can be calibrated in a laboratory. The specific method comprises the following steps: in the refrigeration mode, the evaporator fan runs at a high speed, and when the air output of the air supply outlet in the refrigeration container box is reduced by 50% compared with the air output in a frost-free state by measuring the air output, the collected air pressure difference value is recorded and used as a calibration value for triggering refrigeration and defrosting conditions. In the freezing mode, the evaporator fan runs at a low speed, and the collected air pressure difference value is recorded as a calibration value for triggering the refrigerating and defrosting conditions by measuring the air output of an air supply outlet in the refrigerating container and when the air output is reduced by 65% compared with the air output in a frost-free state. For convenience sakeDescribing, the value of the wind pressure differential pressure sensor under the running condition of the fan and the frostless state of the evaporator is assumed to be P_b(reference value), and the determination value for the need of defrosting operation is P_p50％、P_p65％(represents the defrosting judgment values of the refrigerating mode and the freezing mode respectively).

When a refrigeration unit of a refrigerated container is in a low-temperature refrigeration state, the moisture of goods in the refrigerated container is evaporated, the air circulated in the refrigerated container is brought to an evaporator, because the temperature of the evaporator is generally lower than the temperature of a goods space in the refrigerated container (certain temperature difference is required for heat transfer of the air in the evaporator), the saturation of water in the air is reduced, and water vapor is condensed on fins and a coil pipe of the evaporator in a water droplet mode; on the other hand, the heat transfer efficiency of the evaporator can be increased at the initial frosting stage, and the energy conservation of the refrigerating unit is facilitated. However, the frost layer is too thick, which causes the heat transfer effect of the evaporator to be sharply reduced, the refrigerating capacity of the refrigerating unit to be reduced, the vapor temperature to be reduced, the compression ratio to be increased, the compressor power to be reduced (the compressor power is faster than the refrigerating capacity to be reduced), the COP of the refrigerating unit to be reduced and the energy consumption to be increased. On the other hand, when the surface of the evaporator is frosted seriously, the air flow passage of the evaporator is blocked by the frost layer, the air quantity flowing through the evaporator is reduced sharply, the air quantity supplied to the air supply opening is also reduced, but the power of the fan is increased, and the energy consumption and the heat productivity are increased. If defrosting is not carried out, the temperature in the refrigerator cannot be controlled within a required range, and in severe cases, goods damage can be caused.

The refrigerated container is for improving the quality of the refrigerated refrigeration of goods, and the working condition of refrigeration operation is divided into two modes of a refrigeration mode and a freezing mode, so that the goods transported in the refrigeration mode are generally sensitive to temperature, and the too low temperature can cause the goods to be damaged due to the cold damage phenomenon, so that the air supply temperature can not exceed the set temperature. Under the cold-stored mode, in order to strengthen the heat transfer effect of evaporimeter, the evaporimeter fan generally adopts high-speed gear operation. Goods transported in a freezing mode are weak in low-temperature sensitivity, return air temperature control is generally adopted in order to control the temperature in the box to meet the requirement of set temperature, and a fan of the evaporator runs at a low-speed gear. In view of the difference between the refrigeration mode and the freezing mode of the refrigerated container, in order to improve the pertinence and the accuracy of the operation of the defrosting system, the defrosting control is divided into two working conditions of refrigeration mode defrosting control and freezing mode defrosting control.

(1) And (3) defrosting control in a refrigeration mode:

the control system collects data of the differential pressure sensor, the air inlet temperature sensor and the air outlet temperature sensor in real time and simultaneously collects real-time values P of the differential pressure sensor_sAnd a determination value P required for defrosting operation_p50％Making a comparison when P_s≥P_p50％When the evaporator is frosted seriously, the defrosting operation needs to be started, and a dead zone needs to be designed in consideration of the stability of control, namely when P is_s≥P_p50％And stabilizing for 5-15 min (preferably 10 min) to judge defrosting condition as wind pressure difference. In addition, in order to improve the reliability of frost layer judgment and prevent the self problem of the wind pressure differential pressure sensor and the error problem caused by the influence of a cargo loading mode on the air flow resistance, a temperature difference judgment condition is added. Namely, when the difference value of the inlet air temperature (collected by the inlet air temperature sensor) minus the outlet air temperature (collected by the outlet air temperature sensor) is more than or equal to 4 ℃, the temperature is stabilized for 5 to 15 minutes (preferably 10 minutes) and used as the temperature difference to judge the defrosting condition. When the air pressure difference and the temperature difference meet the conditions at the same time, the defrosting mode is started, and the refrigerated container enters the refrigerating defrosting mode.

The refrigerated container enters a refrigeration defrosting mode, the control system sends out an instruction of closing the liquid supply valve to recover the refrigerant in the evaporator, and when the suction pressure reaches 1.2 times of a low-pressure alarm value, the refrigeration system is stopped. At the moment, the control system sends out an instruction of closing the in-box air supply outlet 6 and the in-box air return inlet 7, detects whether feedback is completed or not through the limiting stopper, sends out an instruction of opening the hot air inlet 4 and the hot air outlet 5, detects whether feedback is completed or not through the limiting stopper, and starts the fan to run by using a high-speed gear. The high temperature air in the environment is sucked by the fan through the hot air inlet 4 and is pressurized and sent to the evaporator 2, the heat exchange is carried out on the surface, the inside and the back of the evaporator 2, and the high temperature air flows out from the hot air outlet 5 after the heat exchange is finished.

As the source of hot air is continuously supplied, the frost layer of the evaporator 2 gradually melts, becoming water which collects from the water collection tray of the steamer 2 and drains out of the tank. At this time, the wind pressure difference value of the windward side and the leeward side of the evaporator 2 and the wind pressure difference sensor value P of the frostless state of the evaporator 2 are compared_bIn comparison, considering that the refrigerated container may be dirty and blocked on the surface of the evaporator 2 during the actual operation process, thereby affecting the value P of the wind pressure differential pressure sensor_sIs difficult to be combined with P_bEqual, therefore, to improve stability and reliability of the control system, P is_bThe numerical values are amplified by 5% to form a range rather than a specific judgment value, i.e., 100% -105%. When the value P of the wind pressure differential pressure sensor_b≤P_s≤1.05*P_bStable for 4-6 minutes (preferably 5 minutes); and meanwhile, when the difference between the air inlet temperature (acquired by the air inlet temperature sensor) and the air outlet temperature (acquired by the air outlet temperature sensor) is less than or equal to 2 ℃, the temperature is stabilized for 4-6 minutes (preferably for 5 minutes), and then the defrosting is considered to be finished. At the moment, the fan is stopped, the hot air inlet 4 and the hot air outlet 5 are closed, the refrigerating unit is started to cool the evaporator 2, when the temperature of the air supply outlet in the refrigerator reaches the temperature in the refrigerator, the air supply outlet 6 in the refrigerator and the air return opening 7 in the refrigerator are opened, and the fan is started to enter the refrigerating mode.

(2) Freezing mode defrosting control:

the defrosting operation in the freezing mode is mainly different from the defrosting operation in the refrigerating mode in that it judges the condition for defrosting. That is, when condition 1: p_s≥P_p65％When the evaporator is frosted seriously, the defrosting operation needs to be started, and a dead zone needs to be designed in consideration of the stability of control, namely when P is_s≥P_p65％Then, the reaction is stabilized for 5 to 15 minutes (preferably 10 minutes). Condition 2: the difference between the inlet air temperature (acquired by the inlet air temperature sensor) and the outlet air temperature (acquired by the outlet air temperature sensor) is not less than 6Stable at 5-15 min (preferably 10 min). Both conditions are satisfied simultaneously, i.e. defrost operation is entered.

The refrigerated container enters a refrigeration defrosting mode, the control system sends out an instruction of closing the liquid supply valve to recover the refrigerant in the evaporator, and when the suction pressure reaches 1.2 times of a low-pressure alarm value, the refrigeration system is stopped. At the moment, the control system sends out an instruction of closing the in-box air supply outlet 6 and the in-box air return inlet 7, detects whether feedback is completed or not through the limiting stopper, sends out an instruction of opening the hot air inlet 4 and the hot air outlet 5, detects whether feedback is completed or not through the limiting stopper, and starts the fan to run by using a high-speed gear. The high temperature air in the environment is sucked by the fan through the hot air inlet 4 and is pressurized and sent to the evaporator 2, the heat exchange is carried out on the surface, the inside and the back of the evaporator 2, and the high temperature air flows out from the hot air outlet 5 after the heat exchange is finished.

Condition 1 of exit from the defrost mode: wind pressure differential pressure sensor value P_b≤P_s≤1.05*P_bStable for 4-6 minutes (preferably 5 minutes); condition 2: the difference between the inlet air temperature (acquired by the inlet air temperature sensor) and the outlet air temperature (acquired by the outlet air temperature sensor) is less than or equal to 2 ℃. If both conditions are satisfied, the defrosting is considered to be completed. At the moment, the fan is stopped, the hot air inlet 4 and the hot air outlet 5 are closed, the refrigerating unit is started to cool the evaporator 2, when the temperature of the air supply outlet in the refrigerator reaches the temperature in the refrigerator, the air supply outlet 6 in the refrigerator and the air return opening 7 in the refrigerator are opened, and the fan is started to enter the refrigeration working condition of the refrigeration mode.

In addition, the air pressure difference value and the temperature difference value are specifically quantized in the above mode, the defrosting starting judgment condition and the defrosting ending judgment condition are determined, intelligent defrosting can be realized, and the problems of frequent defrosting and wrong defrosting of the refrigerated container are perfectly solved.

The present invention will be described in detail below with reference to examples.