A full-flow countercurrent warming system and method for natural gas medium on LNG ships

Abstract

The present invention discloses a full-flow countercurrent natural gas heating system for LNG ships. The system includes a heating module, a natural gas hot pipeline, a volatile gas main, a liquid cargo main, and a natural gas cold pipeline. The heating module includes an HD heater, a first HD compressor, and a second HD compressor. The natural gas is heated by the heating module and enters the cargo hold from the top through the natural gas hot pipeline for heating. It then passes through the natural gas cold pipeline from the bottom of the cargo hold to the heating module for reheating, forming a natural gas circulation pipeline. By heating the cargo hold from the top, the present invention ensures that the natural gas flow rate during heating can reach the parallel connection of the HD compressors, even with a non-full-capacity HD heater and a non-full-size piping arrangement. This achieves full-flow natural gas heating, saving operation time and reducing ship operating costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of shipbuilding, and in particular relates to a full-flow countercurrent warming system and method for a natural gas medium of an LNG ship. Background Art

[0002] With the continuous advancement of LNG carrier technology and the growing market demand, the requirements for the economic efficiency and ease of maintenance of cryogenic equipment are becoming increasingly stringent. For example, HD heaters, the core equipment in the warm-up process, are rarely used for warm-up operations on LNG carriers, as they are only performed during dry dock maintenance, typically every five years, and when the cargo hold containment system is damaged. Furthermore, the heating capacity used in the ship's commonly used GCU free flow mode is far lower than the full capacity. Therefore, in recent years, the cost-effective, non-full-capacity HD heater and its associated non-full-size piping layout have become a mainstream trend favored by shipowners.

[0003] The traditional warming path is as follows: hot natural gas enters from the bottom of the cargo hold, cold natural gas is discharged from the top of the cargo hold to the inlet of the HD compressor, and after being pressurized by the compressor, the natural gas is heated by the HD heater in a circulation direction.

[0004] However, for LNG carriers equipped with non-full-capacity HD heaters or full-size associated piping, continuing to use the traditional warm-up path will cause surge in the HD compressors due to flow limiting, making parallel operation or high-flow parallel operation impossible. This will in turn lead to a situation where the warm-up medium flow is too small and the warm-up time is too long. According to actual ship operation data, the warm-up time will be extended by 1.5 times, increasing related operating time and various costs. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the above-mentioned prior art and provide a full-flow countercurrent tank warming system and method for LNG carriers. The system and method of the present invention warm the cargo hold from the top. In the case of a non-full-capacity HD heater and a non-full-size piping arrangement, the natural gas medium flow rate during tank warming can be guaranteed to reach the HD compressor parallel connection, thus achieving full-flow tank warming, saving operation time, and reducing ship operating costs.

[0006] In order to achieve the above invention purpose, the technical solution provided by the present invention is as follows:

[0007] A full-flow countercurrent heating system for natural gas medium on an LNG ship, the system includes a heating module, a natural gas hot pipeline, a volatile gas main, a liquid cargo main and a natural gas cold pipeline, the heating module includes an HD heater, a first HD compressor and a second HD compressor, the first HD compressor and the second HD compressor are connected in parallel and are respectively connected to the HD heater inlet and the volatile gas main, the HD heater outlet is connected to one end of the natural gas hot pipeline, the other end of the natural gas hot pipeline is connected to the volatile gas main, the first HD compressor and the second HD compressor are connected in parallel and are respectively connected to the HD heater inlet and the volatile gas main A forced return valve and a gravity return valve are provided on the pipeline connected to the volatile gas main pipe. The volatile gas main pipe is respectively connected to the double-way isolation valve on the top of the cargo hold. The inlets of the first HD compressor and the second HD compressor are connected to the natural gas cooling pipeline. The natural gas cooling pipeline is connected to the liquid cargo main pipe via a detachable pipe. The liquid cargo main pipe is respectively connected to the bottom of the cargo hold via the double-way isolation valve. The natural gas is heated by the heating module and enters the cargo hold from the top through the natural gas hot pipeline for cabin heating operation. Then, it is reheated by the heating module from the bottom of the cargo hold through the natural gas cooling pipeline, forming a natural gas circulation pipeline.

[0008] The inlet and outlet of the HD heater are provided with valves, and the outlet of the HD heater is also provided with a bypass valve, which connects the outlets of the first HD compressor and the second HD compressor with the natural gas heat pipeline.

[0009] The inlet and outlet of the first HD compressor and the second HD compressor are provided with valves, and the outlets of the first HD compressor and the second HD compressor are also provided with bypass valves, which connect the natural gas cold pipeline with the natural gas hot pipeline; multiple valves are provided on the natural gas hot pipeline.

[0010] The pipeline between the forced return valve and the gravity return valve is connected to the volatile gas return pipe, and a valve is provided on the volatile gas return pipe.

[0011] A liquid cargo pipe valve is provided on the pipeline connecting the above-mentioned detachable pipe inlet and the liquid cargo main pipe, the detachable pipe outlet is respectively connected to the natural gas hot pipeline and the natural gas cold pipeline, a compressor inlet valve is provided on the pipeline connecting the detachable pipe outlet and the natural gas cold pipeline, and a valve is provided on the pipeline connecting the detachable pipe outlet and the natural gas hot pipeline. The valve provided on the pipeline connecting the detachable pipe outlet and the natural gas hot pipeline is closed during the natural gas cabin heating process.

[0012] A method for counter-flowing the full flow of natural gas medium to a warm-up chamber on an LNG ship, the method specifically comprising the following steps:

[0013] The first step is to prepare a full-flow countercurrent heating system for natural gas medium on an LNG ship. The system includes a heating module, a natural gas hot pipeline, a volatile gas main, a liquid cargo main, and a natural gas cold pipeline. The heating module includes an HD heater, a first HD compressor and a second HD compressor. The first HD compressor and the second HD compressor are connected in parallel and are respectively connected to the HD heater inlet and the volatile gas main. The HD heater outlet is connected to one end of the natural gas hot pipeline, and the other end of the natural gas hot pipeline is connected to the volatile gas main. The first HD compressor and the second HD compressor are connected in parallel. A forced return valve and a gravity return valve are installed on the pipeline connected to the volatile gas main pipe. The volatile gas main pipe is respectively connected to the double-way isolation valve on the top of the cargo hold. The inlets of the first HD compressor and the second HD compressor are connected to the natural gas cooling pipeline. The natural gas cooling pipeline is connected to the liquid cargo main pipe via a detachable pipe. The liquid cargo main pipe is respectively connected to the bottom of the cargo hold via a double-way isolation valve. The natural gas is heated by the heating module and enters the cargo hold from the top through the natural gas hot pipeline for the cabin heating operation. Then, it is reheated by the heating module from the bottom of the cargo hold through the natural gas cooling pipeline, forming a natural gas circulation pipeline.

[0014] The second step is to install a detachable pipe between the liquid cargo pipe valve and the compressor inlet valve to connect the liquid cargo main pipe with the natural gas cooling pipeline;

[0015] The third step is to open the double-way isolation valve connecting the liquid cargo main pipe with the bottom of the cargo hold, the double-way isolation valve connecting the volatile gas main pipe with the top of the cargo hold, and the valves on the HD heater, the first HD compressor, the second HD compressor, and the natural gas heat pipe;

[0016] Step 4: Starting the HD heater, the first HD compressor, and the second HD compressor. The natural gas is compressed by the first HD compressor and the second HD compressor and then reaches the HD heater. The HD heater heats the natural gas and passes the natural gas heat pipe to the volatile gas main. The natural gas then enters the cargo hold from the top of the cargo hold through the volatile gas main to perform a cabin warming operation.

[0017] In the fifth step, after entering the cargo hold, the natural gas enters the liquid cargo main from the bottom of the cargo hold, then passes through the detachable pipe to reach the natural gas cooling pipeline, and then enters the first HD compressor and the second HD compressor through the natural gas cooling pipeline for recompression until the cargo hold reaches the set temperature, completing the cargo hold heating operation.

[0018] Before the HD heater, the first HD compressor and the second HD compressor are started, the forced return valve and the gravity return valve are opened, the forced return valve opening does not exceed 10%, and the gravity return valve opening does not exceed 60%.

[0019] After the first and second HD compressors are started, the flow rates of natural gas processed by the first and second HD compressors are gradually increased based on the surge point locations of the first and second HD compressors. When current limiting occurs with the HD heater, the openings of the forced return valve and the gravity return valve are increased by 3%. Natural gas that cannot be processed by the HD heater enters the volatile gas main through the forced return valve and the gravity return valve.

[0020] The heating temperature of the HD heater is set not to exceed 80°C, and the cargo hold warm-up temperature is set not to exceed 60°C.

[0021] Based on the above technical solution, the present invention's patented full-flow countercurrent warming system and method for LNG carriers has achieved the following technical advantages through practical application:

[0022] 1. The present invention provides a full-flow countercurrent natural gas medium tank heating system and method for LNG ships. By heating the cargo hold from the top, the system ensures that the natural gas medium flow rate during tank heating can reach that of HD compressors in parallel when a non-full-capacity HD heater and a non-full-size associated piping arrangement are used. This achieves full-flow natural gas medium tank heating, saves operation time, shortens cargo hold warm-up time, and reduces ship operating costs.

[0023] 2. Compared with the existing technology, the full-flow countercurrent warming system and method of natural gas medium for LNG carriers of the present invention is realized through the existing warming pipeline, without adding additional pipeline settings and production costs. It improves the natural gas medium flow rate during warming of LNG carriers with non-full-capacity HD heaters and non-full-size corresponding piping arrangements. The HD compressors can be connected in parallel, achieving full-flow natural gas medium warming, reducing production costs and improving economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a distribution diagram of the warming tank pipelines in a full-flow countercurrent warming tank system of a natural gas medium on an LNG ship according to the present invention. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of the present invention more clearly apparent, the present invention is described below using specific examples shown in the accompanying drawings. However, it should be understood that these descriptions are merely illustrative and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0026] like Figure 1The present invention relates to a full-flow countercurrent heating system for natural gas medium of an LNG ship, which includes a heating module 1, a natural gas heat pipe 2, a volatile gas main pipe 3, a liquid cargo main pipe 4 and a natural gas cold pipe 5. The heating module 1 includes an HD heater 11, a first HD compressor 12 and a second HD compressor 13. The first HD compressor 12 and the second HD compressor 13 are connected in parallel and are respectively connected to the inlet of the HD heater 11 and the volatile gas main pipe 3. The outlet of the HD heater 11 is connected to one end of the natural gas heat pipe 2, and the other end of the natural gas heat pipe 2 is connected to the volatile gas main pipe 3. The first HD compressor 12 and the second HD compressor 13 are connected in parallel. A forced return valve 14 and a gravity return valve 15 are provided on the pipeline connected to the volatile gas main 3. The volatile gas main 3 is respectively connected to the two-way isolation valve 6 at the top of the cargo hold 7. The inlets of the first HD compressor 12 and the second HD compressor 13 are connected to the natural gas cooling pipeline 5. The natural gas cooling pipeline 5 is connected to the liquid cargo main 4 via a detachable pipe 51. The liquid cargo main 4 is respectively connected to the bottom of the cargo hold 7 via the two-way isolation valve 6. The natural gas is heated by the heating module 1 and enters the cargo hold 7 from the top through the natural gas hot pipeline 2 for the cabin heating operation. Then, it is reheated by the natural gas cooling pipeline 5 from the bottom of the cargo hold 7 to the heating module 1, forming a natural gas circulation pipeline.

[0027] The HD heater 11 is provided with valves at its inlet and outlet, and a bypass valve is also provided at its outlet. The bypass valve connects the outlets of the first and second HD compressors 12 and 13 to the natural gas heat pipe 2. When the temperature in the cargo hold 7 gradually rises and approaches the set cabin heating temperature, the opening of the bypass valve of the HD heater 11 gradually increases, and the flow of natural gas entering the HD heater 11 decreases, thereby preventing the temperature of the cargo hold 7 from exceeding the set temperature due to natural gas heating. This also saves heating costs. During operation, the valves and bypass valve provided at the inlet and outlet of the HD heater 11 automatically control the opening of the valves and bypass valve provided at the inlet and outlet of the HD heater 11 according to the temperature of the natural gas flowing to the inlet of the HD heater 11.

[0028] Valves are provided at the inlet and outlet of the first HD compressor 12 and the second HD compressor 13. Bypass valves are also provided at the outlets of the first HD compressor 12 and the second HD compressor 13. The bypass valves connect the natural gas cold pipeline 5 with the natural gas hot pipeline 2. Multiple valves are provided on the natural gas hot pipeline 2.

[0029] The pipeline between the forced return valve 14 and the self-flow return valve 15 is connected to the volatile gas return pipe, and a valve is provided on the volatile gas return pipe.

[0030] A liquid cargo pipe valve 52 is provided on the pipeline connecting the inlet of the detachable pipe 51 and the liquid cargo main pipe 4. The outlet of the detachable pipe 51 is respectively connected to the natural gas hot pipeline 2 and the natural gas cold pipeline 5. A compressor inlet valve 53 is provided on the pipeline connecting the outlet of the detachable pipe 51 and the natural gas cold pipeline 5. A valve is provided on the pipeline connecting the outlet of the detachable pipe 51 and the natural gas hot pipeline 2. The valve provided on the pipeline connecting the outlet of the detachable pipe 51 and the natural gas hot pipeline 2 is closed during the natural gas heating process.

[0031] A method for counter-flowing the full flow of natural gas medium to a warm-up chamber on an LNG ship, the method specifically comprising the following steps:

[0032] The first step is to prepare a full-flow countercurrent heating system for natural gas medium on an LNG ship. The system includes a heating module 1, a natural gas heat pipe 2, a volatile gas main pipe 3, a liquid cargo main pipe 4 and a natural gas cold pipe 5. The heating module 1 includes an HD heater 11, a first HD compressor 12 and a second HD compressor 13. The first HD compressor 12 and the second HD compressor 13 are connected in parallel and are respectively connected to the inlet of the HD heater 11 and the volatile gas main pipe 3. The outlet of the HD heater 11 is connected to one end of the natural gas heat pipe 2, and the other end of the natural gas heat pipe 2 is connected to the volatile gas main pipe 3. The first HD compressor 12 and the second HD compressor 13 are connected in parallel. A forced return valve 14 and a gravity return valve 15 are then installed on the pipeline connected to the volatile gas main pipe 3. The volatile gas main pipe 3 is respectively connected to the dual-way isolation valve 6 at the top of the cargo hold 7. The inlets of the first HD compressor 12 and the second HD compressor 13 are connected to the natural gas cooling pipeline 5. The natural gas cooling pipeline 5 is connected to the liquid cargo main pipe 4 via a detachable pipe 51. The liquid cargo main pipe 4 is respectively connected to the bottom of the cargo hold 7 via the dual-way isolation valve 6. The natural gas is heated by the heating module 1 and enters the cargo hold 7 from the top through the natural gas heat pipeline 2 for the cabin heating operation. Then, it is reheated by the natural gas cooling pipeline 5 from the bottom of the cargo hold 7 to the heating module 1, forming a natural gas circulation pipeline.

[0033] The second step is to install the detachable pipe 51 between the liquid cargo pipe valve 52 and the compressor inlet valve 53 to connect the liquid cargo main pipe 4 with the natural gas cooling pipeline 5;

[0034] The third step is to open the dual-way isolation valve 6 connecting the liquid cargo main pipe 4 with the bottom of the cargo hold 7, the dual-way isolation valve 6 connecting the volatile gas main pipe 3 with the top of the cargo hold 7, and the valves on the HD heater 11, the first HD compressor 12, the second HD compressor 13, and the natural gas heat pipe 2;

[0035] In the fourth step, the HD heater 11, the first HD compressor 12, and the second HD compressor 13 are started. Natural gas is compressed by the first HD compressor 12 and the second HD compressor 13 and then reaches the HD heater 11. The HD heater 11 heats the natural gas and passes it through the natural gas heat pipeline 2 to the volatile gas main 3. The natural gas then enters the cargo hold 7 from the top through the volatile gas main 3 for heating. When multiple cargo holds 7 are heated simultaneously, the temperature of each heated hold is monitored in real time. The opening of the dual-way isolation valve 6 is adjusted according to the temperature of the cargo hold 7 to control the flow of natural gas entering the cargo hold 7. The opening of the dual-way isolation valve 6 of the cargo hold 7 with lower temperature is increased, while the opening of the dual-way isolation valve 6 of the cargo hold 7 with higher temperature is decreased. This improves the uniformity of temperature increase during heating of multiple cargo holds 7 and improves the efficiency of natural gas heating.

[0036] In the fifth step, after entering the cargo hold 7, the natural gas enters the liquid cargo main pipe 4 from the bottom of the cargo hold 7, then passes through the detachable pipe 51 to reach the natural gas cooling pipeline 5, and then enters the first HD compressor 12 and the second HD compressor 13 through the natural gas cooling pipeline 5 for recompression until the cargo hold 7 warms up to the set temperature, completing the cargo hold 7 warming operation.

[0037] Before the HD heater 11, the first HD compressor 12 and the second HD compressor 13 are started, the forced return valve 14 and the gravity return valve 15 are opened, the opening degree of the forced return valve 14 does not exceed 10%, and the opening degree of the gravity return valve 15 does not exceed 60%.

[0038] After the first HD compressor 12 and the second HD compressor 13 are started, the flow rate of the natural gas processed by the first HD compressor 12 and the second HD compressor 13 is gradually increased according to the surge point position of the first HD compressor 12 and the second HD compressor 13. When the HD heater 11 has a flow limiting phenomenon, the opening of the forced return valve 14 and the opening of the gravity return valve 15 are increased by 3%. The natural gas that cannot be processed by the HD heater 11 enters the volatile gas main pipe 3 through the opening of the forced return valve 14 and the gravity return valve 15.

[0039] The heating temperature of the HD heater 11 is set not to exceed 80°C, and the warm cabin temperature of the cargo hold 7 is set not to exceed 60°C.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solutions of the present invention. They should all be included in the scope of the technical solutions claimed for protection by the present invention.

Claims

1. A full-flow countercurrent warming system for natural gas medium on an LNG carrier, characterized in that: The system includes a heating module, a natural gas hot pipeline, a volatile gas main, a liquid cargo main, and a natural gas cold pipeline. The heating module includes an HD heater, a first HD compressor, and a second HD compressor. The first and second HD compressors are connected in parallel and are respectively connected to the HD heater inlet and the volatile gas main. The HD heater outlet is connected to one end of the natural gas hot pipeline, and the other end of the natural gas hot pipeline is connected to the volatile gas main. A forced return valve and a gravity return valve are provided on the pipelines connecting the first and second HD compressors to the volatile gas main after they are connected in parallel. The volatile gas main is respectively connected to a two-way isolation valve at the top of the cargo hold. The inlets of the first and second HD compressors are connected to the natural gas cold pipeline. The natural gas cold pipeline is connected to the liquid cargo main via a detachable pipe. The liquid cargo main is respectively connected to the bottom of the cargo hold via a two-way isolation valve. The natural gas is heated by the heating module and enters the cargo hold from the top through the natural gas hot pipeline for warming. It then flows from the bottom of the cargo hold through the natural gas cold pipeline to the heating module for reheating, forming a natural gas circulation pipeline. A liquid cargo pipe valve is provided on the pipeline connecting the detachable pipe inlet and the liquid cargo main pipe, the detachable pipe outlet is respectively connected to the natural gas hot pipeline and the natural gas cold pipeline, a compressor inlet valve is provided on the pipeline connecting the detachable pipe outlet and the natural gas cold pipeline, and a valve is provided on the pipeline connecting the detachable pipe outlet and the natural gas hot pipeline. The valve provided on the pipeline connecting the detachable pipe outlet and the natural gas hot pipeline is closed during the natural gas cabin heating process.

2. The LNG carrier natural gas medium full flow countercurrent warming system according to claim 1 is characterized in that: Valves are provided at the inlet and outlet of the HD heater, and a bypass valve is further provided at the outlet of the HD heater. The bypass valve connects the outlets of the first and second HD compressors with the natural gas heat pipeline.

3. The LNG carrier natural gas medium full flow countercurrent warming system according to claim 2 is characterized in that: The inlet and outlet of the first HD compressor and the second HD compressor are provided with valves, and the outlets of the first HD compressor and the second HD compressor are also provided with bypass valves, which connect the natural gas cold pipeline with the natural gas hot pipeline; multiple valves are provided on the natural gas hot pipeline.

4. The LNG carrier natural gas medium full flow countercurrent warming system according to claim 1 is characterized in that: The pipeline between the forced return valve and the gravity return valve is connected to the volatile gas return pipe, and a valve is provided on the volatile gas return pipe.

5. A method for warming the cabin of an LNG ship by counter-flowing the full flow of natural gas medium, characterized in that: The method specifically comprises the following steps: The first step is to prepare a full-flow countercurrent heating system for natural gas medium on an LNG ship, which includes a heating module, a natural gas hot pipeline, a volatile gas main, a liquid cargo main, and a natural gas cold pipeline. The heating module includes an HD heater, a first HD compressor and a second HD compressor. The first HD compressor and the second HD compressor are connected in parallel and are respectively connected to the HD heater inlet and the volatile gas main. The HD heater outlet is connected to one end of the natural gas hot pipeline, and the other end of the natural gas hot pipeline is connected to the volatile gas main. The first HD compressor and the second HD compressor are connected in parallel. A forced return valve and a gravity return valve are provided on the pipeline connected to the volatile gas main. The volatile gas main is respectively connected to the dual-way isolation valve at the top of the cargo hold. The inlets of the first and second HD compressors are connected to the natural gas cooling pipeline. The natural gas cooling pipeline is connected to the liquid cargo main via a detachable pipe. The liquid cargo main is respectively connected to the bottom of the cargo hold via a dual-way isolation valve. The natural gas is heated by the heating module and enters the cargo hold from the top through the natural gas hot pipeline for warming. It then flows from the bottom of the cargo hold through the natural gas cooling pipeline to the heating module for reheating, forming a natural gas circulation pipeline. The second step is to install a detachable pipe between the liquid cargo pipe valve and the compressor inlet valve to connect the liquid cargo main pipe with the natural gas cooling pipeline; The third step is to open the double-way isolation valve connecting the liquid cargo main pipe with the bottom of the cargo hold, the double-way isolation valve connecting the volatile gas main pipe with the top of the cargo hold, and the valves on the HD heater, the first HD compressor, the second HD compressor, and the natural gas heat pipe; Step 4: Starting the HD heater, the first HD compressor, and the second HD compressor. The natural gas is compressed by the first HD compressor and the second HD compressor and then reaches the HD heater. The HD heater heats the natural gas and passes the natural gas heat pipe to the volatile gas main. The natural gas then enters the cargo hold from the top of the cargo hold through the volatile gas main to perform a cabin warming operation. In the fifth step, after entering the cargo hold, the natural gas enters the liquid cargo main from the bottom of the cargo hold, then passes through the detachable pipe to reach the natural gas cooling pipeline, and then enters the first HD compressor and the second HD compressor through the natural gas cooling pipeline for recompression until the cargo hold reaches the set temperature, completing the cargo hold heating operation.

6. The method for counter-flowing the full flow of natural gas medium to warm the cabin of an LNG ship according to claim 5, characterized in that: Before the HD heater, the first HD compressor and the second HD compressor are started, the forced return valve and the gravity return valve are opened, the forced return valve opening does not exceed 10%, and the gravity return valve opening does not exceed 60%.

7. The method for warming the cabin of an LNG carrier by countercurrent flow of natural gas medium at full flow rate according to claim 6, characterized in that: After the first and second HD compressors are started, the flow rates of natural gas processed by the first and second HD compressors are gradually increased based on the surge point positions of the first and second HD compressors. When current limiting occurs with the HD heater, the openings of the forced return valve and the gravity return valve are increased by 3%. Natural gas that cannot be processed by the HD heater enters the volatile gas main pipe through the forced return valve opening and the gravity return valve.

8. The method for warming the cabin of an LNG carrier by countercurrent flow of natural gas at full flow rate according to claim 5, characterized in that: The heating temperature of the HD heater is set not to exceed 80°C, and the cargo hold warm-up temperature is set not to exceed 60°C.

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