CN213746117U

CN213746117U - Efficient energy-saving heat exchange system based on LNG cold energy

Info

Publication number: CN213746117U
Application number: CN202022886073.9U
Authority: CN
Inventors: 郭文军; 葛晓成; 王国华
Original assignee: Chongqing Kairui Power Technology Co ltd; China Automotive Engineering Research Institute Co Ltd
Current assignee: Chongqing Kairui Power Technology Co ltd; China Automotive Engineering Research Institute Co Ltd
Priority date: 2020-12-04
Filing date: 2020-12-04
Publication date: 2021-07-20
Anticipated expiration: 2030-12-04

Abstract

The utility model discloses a high-efficiency energy-saving heat exchange system based on LNG cold energy, which comprises a refrigeration box, an LNG gas cylinder, a heat exchanger assembly, an engine application assembly, a controller and a measuring sensor assembly; the controller is used for receiving an engine rotating speed signal transmitted from the electronic control unit ECU, an air temperature signal in the refrigerating box transmitted by the first temperature sensor and an LNG temperature signal at the outlet position of the heat exchanger transmitted by the second temperature sensor, and converting the engine rotating speed signal into a rotating speed signal of the variable frequency fan to control the rotating speed of the variable frequency fan; when the temperature of the LNG outlet of the heat exchanger is higher than a set value A or the temperature of the air in the refrigerating box is lower than a set value B, the controller controls the variable frequency fan to stop running; when the controller controls the variable frequency fan to operate, the rotating speed of the variable frequency fan is increased along with the increase of the rotating speed of the natural gas engine. The system can reduce the energy consumption of the variable frequency fan, and efficiently and safely utilizes the LNG cold energy.

Description

Efficient energy-saving heat exchange system based on LNG cold energy

Technical Field

The utility model belongs to the technical field of the refrigerator car, concretely relates to energy-efficient heat transfer system based on LNG cold energy.

Background

With the development of social economy, the living standard of people is continuously improved, the food transportation amount is increased day by day, and the food refrigeration chain plays more and more remarkable roles in improving the living quality of people. Meat, poultry, aquatic products, fruits, vegetables, dairy products, cold drinks, health-care foods and the like can be transported by using the refrigerator car, so that the freshness and the rot resistance of the foods can be ensured, the health of people can be ensured, and the waste of the foods can be reduced. To lower the temperature of the refrigerator car to a temperature specified by the standard (about-18 ℃ to +5 ℃, which varies depending on the grade of the refrigerator car), an air conditioner is generally used. The air conditioner uses electric energy to refrigerate, and forces the heat in the refrigerating box to be transferred to the atmospheric environment, so that the temperature in the refrigerating box is reduced to reach the required temperature. The refrigeration of the refrigerator car by the air conditioner consumes energy, increases the fuel/energy consumption of the car, and increases the emission of carbon dioxide and harmful pollutants.

Energy conservation and emission reduction are common problems in the automobile field. The natural gas automobile belongs to a clean energy automobile, the emission of carbon dioxide and harmful pollutants is relatively less, and the natural gas automobile is a kind of automobile advocated and developed by the nation. LNG is a liquid fuel stored in insulated bottles with a minimum temperature of-162 ℃. When LNG is used as fuel on the refrigerator car, the liquid LNG needs to be heated to a gaseous state (for example, 0-20 ℃) for the use of a natural gas engine. In a refrigerator car, LNG in a liquid state is introduced into a vaporizer, and the LNG is heated by cooling water of an engine. The endothermic process of LNG can be divided into two stages: in the stage 1, LNG is changed from liquid state to low-temperature gas state to absorb latent heat of vaporization; in the 2 nd stage, the gas absorbs heat from the low-temperature gas state to the normal-temperature gas state. The cold energy released by the LNG per unit mass is about 750kJ/kg during the whole vaporization and heating process. The more power the engine is, the more LNG mass is consumed and the more cold energy is released by the LNG. The cold energy released by the LNG is not utilized and is wasted.

The cold energy released by LNG on the refrigerator car is used for reducing the temperature of air in the refrigerator car, the fuel consumption of an engine can be reduced, and the refrigerator car has obvious energy-saving and emission-reducing effects compared with an air conditioner for refrigeration. To utilize the cold energy of LNG, a heat exchanger is used to exchange heat between LNG and air. In order to obtain a good heat exchange effect, a frequency conversion fan needs to be used for forced heat exchange. The higher the rotating speed of the variable frequency fan is, the larger the air quantity is, the higher the air flow rate is, and the better the heat exchange effect is. However, the higher the rotating speed of the variable frequency fan is, the higher the consumed power is, which is not beneficial to energy conservation and emission reduction. Assuming that the power of the variable frequency fan is 150-200W, the energy consumed by the variable frequency fan in 1 hour is 540-720 kJ. Because the variable frequency fan is arranged in the refrigerating box, the consumed energy can be converted into heat and is left in the refrigerating box to become a heat source, a part of utilized cold energy is offset, the cooling speed of the refrigerating box is slowed, and the minimum temperature limit value which can be reached is increased. For example 1 refrigerator with a volume of 17 cubic meters, in which the air is lowered by 30 c (for example from 35 c to 5c) and requires approximately 856kJ of refrigeration. Therefore, the ratio of the energy consumed by the variable frequency fan to the cold quantity required by air cooling of the refrigerating box is calculated to be 63% -84%. Therefore, how to reduce the energy consumed by the variable frequency fan is an important problem worthy of research.

The heat exchanger is vertically arranged, so that water formed after frost on the heat exchanger is melted flows downwards and is drained, and the heat transfer effect is not influenced. In order to enhance the heat exchange effect and reduce the thickness of the frosting layer, a variable frequency fan and an air duct are adopted for forced ventilation, and the flow velocity of air is increased to increase the heat transfer coefficient of the heat exchanger. The flow rate of the air is related to the air quantity of the variable frequency fan, the larger the air quantity of the variable frequency fan is, the larger the flow rate of the air is, but the larger the power consumed by the variable frequency fan is. In the process of running the refrigerator car on the road, the rotating speed and the power of the engine are constantly changed, and the consumed LNG amount is also constantly changed. When the engine runs at a low speed, the consumed LNG amount is less, the available cold energy is less, and the rotating speed of the variable frequency fan is also lower; when the engine runs at a high speed, the consumed LNG amount is large, the available cold energy is large, and the rotating speed of the variable frequency fan is high.

In addition, because the star-shaped heat exchanger consists of a plurality of sections of U-shaped heat exchange tubes, the temperature distribution is extremely uneven on a pipeline between the inlet and the outlet of the heat exchanger. The temperature of the pipeline surface close to the LNG inlet part is low (the temperature of LNG in the pipeline is about-130 ℃ to-120 ℃), and the heat exchange with air is more; the surface of the pipeline near the LNG outlet part has a high temperature (for example, the temperature of LNG in the pipe is about 0 ℃), and heat exchange with air is small. When different pipeline parts of the heat exchanger are flushed by the same air quantity, the air quantity is insufficient for pipelines with lower temperature, and defrosting and draining on the surface of the heat exchanger are not facilitated; for pipelines with higher temperature, the air quantity is too much, and the energy consumption of the variable frequency fan is increased.

SUMMERY OF THE UTILITY MODEL

In order to overcome the defect that above-mentioned prior art exists, the utility model aims at providing a reduce frequency conversion fan energy consumption, high-efficient safe energy-efficient heat transfer system based on LNG cold energy.

Therefore, the utility model discloses the technical scheme who adopts does: an efficient energy-saving heat exchange system based on LNG cold energy comprises a refrigerating box, an LNG gas cylinder, a heat exchanger assembly and an engine application assembly, wherein the LNG gas cylinder and the engine application assembly are arranged outside the refrigerating box; the heat exchanger assembly comprises a heat exchanger, an air duct and a variable frequency fan, the heat exchanger is vertically arranged in the air duct, the variable frequency fan is arranged outside the upper part of the air duct, and the lower part of the air duct is provided with an air inlet;

the LNG gas cylinder, the manual stop valve, the heat exchanger, the pressure release valve, the pressure regulator, the common rail injection body and the natural gas engine are sequentially connected through an LNG pipeline; the measurement sensor assembly comprises a first temperature sensor for measuring the temperature of the air in the refrigeration container, and a second temperature sensor for measuring the temperature of the LNG at the outlet position of the heat exchanger;

the electronic control unit ECU is respectively connected with the natural gas engine, the common rail injection body and the controller through cables, the controller is respectively connected with the variable frequency fan, the first temperature sensor and the second temperature sensor through cables, and the controller is used for receiving an engine rotating speed signal transmitted from the electronic control unit ECU, an air temperature signal in the refrigerating box transmitted from the first temperature sensor and an LNG temperature signal at the outlet position of the heat exchanger transmitted from the second temperature sensor and converting the engine rotating speed signal, the air temperature signal and the LNG temperature signal into rotating speed signals of the variable frequency fan to control the rotating speed of the variable frequency fan; when the temperature of the LNG outlet of the heat exchanger is higher than a set value A or the temperature of the air in the refrigerating box is lower than a set value B, the controller controls the variable frequency fan to stop running; when the controller controls the variable frequency fan to operate, the rotating speed of the variable frequency fan is increased along with the increase of the rotating speed of the natural gas engine.

The working process of the system is as follows: when the system is operating properly, the liquefied LNG flows into the heat exchanger in the refrigeration case. The low-temperature LNG absorbs the heat of the air in the refrigerating box through the heat exchanger, completes vaporization and temperature rise, and then flows out of the heat exchanger. The variable frequency fan operates under the control of the controller, air flows into the air channel from the inlet of the air channel, flows upwards to perform forced heat exchange with LNG, heat is transferred to the LNG, and the air with the reduced temperature flows out from the outlet of the variable frequency fan at the upper part of the air channel to be mixed with the air in the refrigerating box. Under the effect of frequency conversion fan, air circulation flows, constantly gives LNG with heat transfer, and the temperature is reduced. The LNG (gas) flowing out of the heat exchanger flows into a pressure regulator to be pressurized, is regulated to a required operating pressure of the common rail injection body, and then flows into the common rail injection body. Under the control of an Electronic Control Unit (ECU), a plurality of nozzles in the common rail injection body sequentially work to inject a proper amount of natural gas, so that the requirements of a natural gas engine on power and air-fuel ratio are met. The controller receives an engine rotating speed signal transmitted from an electronic control unit ECU and converts the engine rotating speed signal into a control signal of the variable-frequency fan. When the natural gas engine runs at a high speed, the variable frequency fan runs at a high speed; when the natural gas engine runs at a low speed, the variable frequency fan runs at a low speed. Under the condition of ensuring sufficient heat exchange, the power consumption of the variable frequency fan and the heat productivity left in the refrigerating box are reduced, and the utilization effect of LNG cold energy and the cooling speed of the refrigerating box are improved.

Preferably, the lower portion of the air duct is provided with a variable cross-section air inlet, and the opening area from the LNG inlet side to the outlet side of the heat exchanger is gradually reduced. The heat exchanger is used for forcedly exchanging heat in different areas, reducing the air volume (power) of the fan, reasonably distributing the air volume, providing more air flow for the low-temperature area of the heat exchanger and less air flow for the high-temperature area, and realizing good heat exchange effect of the heat exchanger under the condition of using the small-air-volume variable frequency fan.

Preferably, the heat exchanger is formed by assembling a plurality of straight pipes and U-shaped connecting pipes, two adjacent parallel straight pipes are connected by the U-shaped connecting pipes, and a plurality of radiating fins which are uniformly distributed in a divergent manner are arranged on the outer wall of each straight pipe to form the star-shaped radiating straight pipe.

Preferably, the measuring sensor assembly further comprises a natural gas leakage sensor for measuring natural gas leakage in the refrigerating box, the controller is connected with the natural gas leakage sensor through a cable, and when natural gas in the refrigerating box leaks, the controller is linked with the alarm to give an alarm. A natural gas leakage sensor is arranged in the refrigerator, and natural gas leakage is monitored and an alarm is given; the pressure relief valve of installation on the LNG pipeline combines, and the pressure relief valve can be opened automatically when LNG pressure is too high, releases a small portion of natural gas in the atmosphere, makes pressure get back to the safe within range, guarantees that pipeline and each spare part do not receive the damage.

More preferably, the LNG pipeline from the outlet of the manual stop valve to the refrigerating box is wrapped with a heat insulating material layer.

Further preferably, the first temperature sensor and the natural gas leakage sensor are mounted at the geometric center of the top of the refrigerator.

The utility model has the advantages that:

energy-free refrigeration: the air temperature in the refrigerating box in the refrigerator car is reduced by utilizing the cold energy of the LNG, the energy of an engine is not consumed, the vaporized LNG is used as the fuel of the natural gas engine, and the purpose of dual utilization of the energy is achieved.

(II) reducing energy consumption and heat productivity of the fan: the variable frequency fan is adopted to be combined with the controller for control, the rotating speed of the variable frequency fan follows the rotating speed of the engine, the running time and the rotating speed of the variable frequency fan are reduced, the energy consumption of the variable frequency fan and the heat (remained in the refrigerating box) converted from the energy consumption are reduced, and the utilization effect of LNG cold energy and the cooling speed of the refrigerating box are improved.

Drawings

Fig. 1 is a schematic structural diagram of the present invention.

FIG. 2 is a front view of the heat exchanger assembly.

FIG. 3 is a side view of a heat exchanger assembly.

Fig. 4 is a schematic structural diagram of a heat exchanger.

Detailed Description

The invention will be further described by way of examples with reference to the accompanying drawings:

referring to fig. 1-3, the efficient energy-saving heat exchange system based on the LNG cold energy mainly comprises an LNG gas cylinder 1, a manual stop valve 2, a heat-insulating material layer 3, a refrigerator 4, a heat exchanger 5, an air duct 6, a variable frequency fan 7, a first temperature sensor 8, a natural gas leakage sensor 9, a second temperature sensor 10, a pressure release valve 11, a pressure regulator 12, a common rail injection body 13, a natural gas engine 14, an electronic control unit ECU 15 and a controller 16.

The LNG gas cylinder 1 and the engine application assembly are arranged outside the refrigerating box 4, and the heat exchanger assembly is arranged in the refrigerating box 4. The engine application assembly mainly comprises a pressure relief valve 11, a pressure regulator 12, a common rail injection body 13, a natural gas engine 14 and an electronic control unit ECU 15. The ECU 15 is used for control of the natural gas engine 14 and transmits a rotation speed signal of the natural gas engine 14 to the controller. The pressure regulator 12 is used to regulate the pressure of the natural gas to the working pressure required by the common rail injection body 13, and the common rail injection body 13 is used to control the flow rate of the natural gas required by the natural gas engine 14. The pressure relief valve 11 is installed outside the refrigeration box 4 and used for controlling the highest pressure of the LNG in the pipeline, when the pressure of the LNG in the pipeline exceeds the set highest pressure, the pressure relief valve 11 is opened to release a part of gas, so that the gas pressure is in a normal range, and related parts are protected from being damaged.

The heat exchanger assembly mainly comprises a heat exchanger 5, an air duct 6 and a variable frequency fan 7.

The heat exchanger 5 is vertically arranged in the air duct 6, the variable frequency fan 7 is arranged outside the upper part of the air duct 6, and the lower part of the air duct 6 is provided with an air inlet. The air duct 6 is a box-type thin-shell structure. Preferably, the lower part of the air duct 6 is provided with a variable cross-section air inlet, and the area of the opening from the LNG inlet side to the outlet side of the heat exchanger 5 is gradually reduced. The air inlet is of a variable cross-section structure, the part close to the low-temperature area of the heat exchanger is large in area and large in air inlet amount, and the flow velocity of air in the air channel is high, so that forced heat exchange between the air and LNG is facilitated; the part close to the high-temperature area has small area and less intake, and the air has low flow velocity in the air duct and corresponds to less heat exchange amount. Through the mode, the heat exchanger has a good heat exchange effect under the condition that the air quantity of the fan is small.

The LNG gas cylinder 1, the manual stop valve 2, the heat exchanger 5, the pressure release valve 11, the pressure regulator 12, the common rail injection body 13 and the natural gas engine 14 are sequentially connected through an LNG pipeline.

The measuring sensor assembly comprises a first temperature sensor 8, a second temperature sensor 10 and a natural gas leakage sensor 9. A first temperature sensor 8 is used to measure the temperature of the air in the refrigeration case 4 and a second temperature sensor 10 is used to measure the temperature of the LNG at the outlet of the heat exchanger 5. The natural gas leakage sensor 9 is used to measure whether there is a natural gas leakage in the refrigerator case 4.

The electronic control unit ECU 15 is connected to the natural gas engine 14, the common rail injection body 13, and the controller 16 via cables, respectively. The controller 16 is respectively connected with the variable frequency fan 7, the first temperature sensor 8, the second temperature sensor 10 and the natural gas leakage sensor 9 through cables.

The controller 16 is used for receiving an engine rotating speed signal transmitted from the electronic control unit ECU 15, an air temperature signal in the refrigerating box 4 transmitted from the first temperature sensor 8, and an LNG temperature signal at the outlet position of the heat exchanger 5 transmitted from the second temperature sensor 10, and converting the engine rotating speed signal into a rotating speed signal of the variable frequency fan 7 to control the rotating speed of the variable frequency fan 7; when the LNG outlet temperature of the heat exchanger 5 is higher than a set value A or the air temperature in the refrigerating box 4 is lower than a set value B, the controller 16 controls the variable frequency fan 7 to stop running; when the controller 16 controls the variable frequency fan 7 to operate, the rotating speed of the variable frequency fan 7 is increased along with the increasing of the rotating speed of the natural gas engine 14.

In addition, the controller 16 is also used for receiving a natural gas leakage signal transmitted from the natural gas leakage sensor 9, and when the natural gas in the refrigerating box 4 leaks, the controller 16 is linked with the alarm to give an alarm.

The LNG pipeline from the outlet of the manual stop valve 2 to the refrigerating box 4 is preferably wrapped with a thermal insulation material layer 3.

The first temperature sensor 8 and the natural gas leakage sensor 9 are preferably installed at the geometric center of the top of the refrigerating case 4. Natural gas has a lower density than air and the leaking natural gas tends to collect at higher locations. When the concentration of the leaked natural gas reaches a set value (lower than the lower limit of the flammable concentration), the controller 16 may issue an audible or visual alarm. The staff accessible closes manual stop valve 2 and cuts off the air supply, opens 4 doors of fridge and ventilates measures such as processing, prevents to take place the incident.

As shown in fig. 4, the heat exchanger 5 is assembled from a plurality of straight pipes 5a and U-shaped connection pipes 5 b. Two adjacent straight pipes 5a arranged in parallel are connected by a U-shaped connecting pipe 5b, and a plurality of radiating fins 5c which are uniformly distributed in a radiating shape are arranged on the outer wall of each straight pipe 5a to form a star-shaped radiating straight pipe, so that the heat exchange effect is better.

In this system, LNG gas cylinder 1: for storing LNG fuel;

and 2, manual stop valve 2: for controlling the flow of LNG;

thermal insulation material layer 3: the LNG pipeline heat insulation device is used for heat insulation of the LNG pipeline and preventing external heat from being transferred to LNG;

the refrigerating box 4: a closed refrigeration space for forming heat preservation;

a heat exchanger component: the LNG refrigeration system is used for exchanging heat between LNG and air in the refrigeration box;

a measurement sensor assembly: for measuring the temperature of the gas and the leakage of natural gas;

an engine application component: the LNG fuel is consumed by an engine;

the controller 16: the device is used for measuring and displaying the temperature of gas, measuring the leakage of natural gas, giving an alarm and controlling the rotating speed of the variable frequency fan.

After the liquefied LNG (the minimum temperature is usually-162 ℃) flows out of the LNG cylinder 1, the flow thereof is controlled by a manual shutoff valve 2. Wrap up heat preservation thermal insulation material layer 3 on the LNG pipeline after manual stop valve 2, prevent that external heat from transmitting for the LNG pipeline, avoid usable LNG cold energy to reduce.

When the variable frequency fan 7 operates, air in the refrigerating box 4 flows into the air duct 6 from the air inlet, then flows upwards along the star-shaped heat dissipation straight pipe, exchanges heat with LNG through the heat exchanger, and transfers heat to the LNG. The temperature of the air is reduced after heat exchange, and then the air flows out through the outlet of the variable frequency fan 7 and is mixed with the air (with higher temperature) in the refrigerating box 4. By this repeated circulation, the temperature of the air in the refrigerating box 4 is lowered.

The LNG flowing out of the heat exchanger 5 is changed into gas, flows into the pressure regulator 12, is pressure-regulated, and then flows into the common rail injector 13. Under the control of the electronic control unit ECU 15, the plurality of nozzles in the common rail injection body 13 sequentially work to inject a proper amount of natural gas, so as to meet the requirements of the natural gas engine 14 on power and air-fuel ratio.

The controller 16 is connected to the electronic control unit ECU 15 and the sensors via cables. The controller 16 receives the signal of the first temperature sensor 8, measures and displays the temperature of the air in the refrigerating box 4, and when the air temperature reaches a set value B, the variable frequency fan 7 stops running (namely, the engine runs); the controller 16 receives the signal of the second temperature sensor 10, measures and displays the temperature of the LNG, and when the temperature of the LNG is higher than a set value a (e.g., the set value a is 0 ℃), the variable frequency fan 7 is not operated (i.e., the engine is operated); the controller 16 receives the signal of the natural gas leakage sensor 9, and gives out sound and light alarm when the leakage amount exceeds a set limit value C; the controller 16 receives the rotation speed signal of the natural gas engine 14 transmitted by the electronic control unit ECU 15 and converts the rotation speed signal into a rotation speed signal for controlling the variable frequency fan 7. When the controller 16 controls the variable frequency fan 7 to operate and the natural gas engine 14 operates at a high speed, the variable frequency fan 7 operates at a high speed; when the natural gas engine 14 runs at a low speed, the variable frequency fan 7 runs at a low speed; when the natural gas engine 14 does not operate, the variable frequency fan 7 does not operate, and energy consumption is reduced.

Claims

1. The utility model provides an energy-efficient heat transfer system based on LNG cold energy, includes fridge (4), LNG gas cylinder (1), heat exchanger subassembly, engine application assembly, LNG gas cylinder (1), engine application assembly set up outside fridge (4), and heat exchanger subassembly sets up in fridge (4), engine application assembly includes relief valve (11), pressure regulator (12), common rail injection body (13), natural gas engine (14) and electronic control unit ECU (15), its characterized in that: further comprising a controller (16) and a measurement sensor assembly; the heat exchanger assembly comprises a heat exchanger (5), an air duct (6) and a variable frequency fan (7), the heat exchanger (5) is vertically arranged in the air duct (6), the variable frequency fan (7) is arranged outside the upper part of the air duct (6), and the lower part of the air duct (6) is provided with an air inlet;

the LNG cylinder (1), the manual stop valve (2), the heat exchanger (5), the pressure release valve (11), the pressure regulator (12), the common rail injection body (13) and the natural gas engine (14) are sequentially connected through an LNG pipeline; the measuring sensor assembly comprises a first temperature sensor (8) for measuring the temperature of the air in the refrigeration container (4), a second temperature sensor (10) for measuring the temperature of the LNG at the outlet position of the heat exchanger (5);

the electronic control unit ECU (15) is respectively connected with the natural gas engine (14), the common rail injection body (13) and the controller (16) through cables, the controller (16) is respectively connected with the variable frequency fan (7), the first temperature sensor (8) and the second temperature sensor (10) through cables, and the controller (16) is used for receiving an engine rotating speed signal transmitted from the electronic control unit ECU (15), an air temperature signal in the refrigerating box (4) transmitted from the first temperature sensor (8) and an LNG temperature signal at the outlet position of the heat exchanger (5) transmitted from the second temperature sensor (10) and converting the engine rotating speed signal into a rotating speed signal of the variable frequency fan (7) to control the rotating speed of the variable frequency fan (7); when the temperature of the LNG outlet of the heat exchanger (5) is higher than a set value A or the temperature of the air in the refrigerating box (4) is lower than a set value B, the controller (16) controls the variable frequency fan (7) to stop running; when the controller (16) controls the variable frequency fan (7) to operate, the rotating speed of the variable frequency fan (7) is increased along with the increase of the rotating speed of the natural gas engine (14).

2. The LNG cold energy-based efficient and energy-saving heat exchange system according to claim 1, wherein: the lower part of the air duct (6) is provided with a variable-section air inlet, and the opening area from the LNG inlet side to the outlet side of the heat exchanger (5) is gradually reduced.

3. The LNG cold energy-based efficient and energy-saving heat exchange system according to claim 1, wherein: the heat exchanger (5) is formed by assembling a plurality of straight pipes (5a) and U-shaped connecting pipes (5b), two adjacent parallel straight pipes (5a) are connected by the U-shaped connecting pipes (5b), and a plurality of radiating fins (5c) which are uniformly distributed in a radiating manner are arranged on the outer wall of each straight pipe (5a) to form a star-shaped radiating straight pipe.

4. The LNG cold energy-based efficient and energy-saving heat exchange system according to claim 1, wherein: the measuring sensor assembly further comprises a natural gas leakage sensor (9) used for measuring natural gas leakage in the refrigerating box (4), the controller (16) is connected with the natural gas leakage sensor (9) through a cable, and when natural gas in the refrigerating box (4) leaks, the controller (16) is linked with the alarm to give an alarm.

5. The LNG cold energy-based efficient and energy-saving heat exchange system according to claim 1, wherein: and an LNG pipeline from the outlet of the manual stop valve (2) to the refrigerating box (4) is wrapped with a heat-insulating material layer (3).

6. The LNG cold energy-based efficient and energy-saving heat exchange system according to claim 4, wherein: the first temperature sensor (8) and the natural gas leakage sensor (9) are arranged at the geometric center of the top of the refrigerating box (4).