Taiyuan Coca-Cola Beverage Company uses the ammonia compressor unit as a cooling source for the cooling of carbonated beverages. It consists of two Danish SABROE SMC 108S piston compressors, a common condenser, an evaporator and corresponding valve piping, as shown in Figure 1. .
After the refrigerant (aqueous glycol solution) in the horizontal evaporator exchanges heat with the working medium (ammonia), it is cooled to a set temperature of 20 ° C, and is sent to the production line for cooling by a refrigerant circulation pump.
The complete system is controlled by PLC. After being put into operation, in the automatic state, the system can adjust the operation mode of the compressor according to the change of the refrigerant temperature at the outlet of the evaporator, including automatic shifting of four gears of 25%, 50%, 75% and 100%. Automatically shut down and use two compressors in the set priority order. At the same time, the system sets the inspiratory, exhaust pressure protection, refrigerant freezing point protection, and restarts the Zui small delay and other automatic protection programs, thus ensuring the safe operation of the long-cycle unattended state. Since the system was put into use in 1998, the refrigeration effect is good. In particular, the operating state of the machine can be automatically adjusted according to the production requirements of different varieties, so that the evaporator outlet refrigerant temperature is at the set value of 2 0C+1 0C. It not only guarantees production, but also saves energy to a large extent.
During the peak season of production in the summer of 2004, it was found that the refrigerant temperature of the system evaporator was out of the set value, and the positive deviation was observed. After the compressor is lowered, the compressor starts and stops, the shift is frequent, and the temperature difference of the refrigerant fluctuates more. It is impossible to obviously remove the peak temperature above 4.2 °C.
After careful analysis, the cause of the fault is determined as follows: When the production has a downtime, the refrigeration system also stops according to the setting. At this time, the refrigerant that is stationary in the plate heat exchanger will have a local "high temperature". After the system is restarted, since the flux in the refrigerant pipeline is basically the same, the entire system does not flow relatively during the cycle, so a segmented temperature difference occurs in the refrigerant pipe. The source of the system's start and stop is the temperature of the refrigerant at the evaporator outlet. There is a segmental temperature difference that will cause the feedback signal to be distorted. When the system automatically stops according to the low temperature segment signal, the high temperature segment just enters the evaporator. In order to avoid equipment damage, the system sets a protection program that the compressor can automatically restart after 5 minutes of shutdown. At this time, the system water temperature will be seriously out of tolerance. This phenomenon is more noticeable due to the frequent occurrence of downtime. The temperature difference of the segment seriously interferes with the system's visual control system, and even the refrigerant circulation will still exist after the week. The refrigeration system is subject to fluctuations, and the product quality defects are caused by the Zui.
Therefore, in October 2004, the overhaul was used to add a refrigerant homogenized water tank at the end of the refrigerant circulation line (as shown in the double-dotted line in Figure 1), and the set capacity was double that of the original system. Allow the refrigerant to enter the homogenized water tank before entering the evaporator for energy storage and homogenization. The temperature difference of the evaporator inlet refrigerant is reduced from 6 to 14 0C to within 30 °C. After half a year of operation, the practice proves that by controlling the inlet temperature difference of the evaporator, not only the defect of the system cooling temperature instability is successfully solved, but also the frequency of the compressor start-stop shift is greatly reduced, and the power-saving effect is also very clear. From January to May 2005, the ammonia compressor saved 21,000 kW·h compared with the same period in 2004.
After the refrigerant (aqueous glycol solution) in the horizontal evaporator exchanges heat with the working medium (ammonia), it is cooled to a set temperature of 20 ° C, and is sent to the production line for cooling by a refrigerant circulation pump.
The complete system is controlled by PLC. After being put into operation, in the automatic state, the system can adjust the operation mode of the compressor according to the change of the refrigerant temperature at the outlet of the evaporator, including automatic shifting of four gears of 25%, 50%, 75% and 100%. Automatically shut down and use two compressors in the set priority order. At the same time, the system sets the inspiratory, exhaust pressure protection, refrigerant freezing point protection, and restarts the Zui small delay and other automatic protection programs, thus ensuring the safe operation of the long-cycle unattended state. Since the system was put into use in 1998, the refrigeration effect is good. In particular, the operating state of the machine can be automatically adjusted according to the production requirements of different varieties, so that the evaporator outlet refrigerant temperature is at the set value of 2 0C+1 0C. It not only guarantees production, but also saves energy to a large extent.
During the peak season of production in the summer of 2004, it was found that the refrigerant temperature of the system evaporator was out of the set value, and the positive deviation was observed. After the compressor is lowered, the compressor starts and stops, the shift is frequent, and the temperature difference of the refrigerant fluctuates more. It is impossible to obviously remove the peak temperature above 4.2 °C.
After careful analysis, the cause of the fault is determined as follows: When the production has a downtime, the refrigeration system also stops according to the setting. At this time, the refrigerant that is stationary in the plate heat exchanger will have a local "high temperature". After the system is restarted, since the flux in the refrigerant pipeline is basically the same, the entire system does not flow relatively during the cycle, so a segmented temperature difference occurs in the refrigerant pipe. The source of the system's start and stop is the temperature of the refrigerant at the evaporator outlet. There is a segmental temperature difference that will cause the feedback signal to be distorted. When the system automatically stops according to the low temperature segment signal, the high temperature segment just enters the evaporator. In order to avoid equipment damage, the system sets a protection program that the compressor can automatically restart after 5 minutes of shutdown. At this time, the system water temperature will be seriously out of tolerance. This phenomenon is more noticeable due to the frequent occurrence of downtime. The temperature difference of the segment seriously interferes with the system's visual control system, and even the refrigerant circulation will still exist after the week. The refrigeration system is subject to fluctuations, and the product quality defects are caused by the Zui.
Therefore, in October 2004, the overhaul was used to add a refrigerant homogenized water tank at the end of the refrigerant circulation line (as shown in the double-dotted line in Figure 1), and the set capacity was double that of the original system. Allow the refrigerant to enter the homogenized water tank before entering the evaporator for energy storage and homogenization. The temperature difference of the evaporator inlet refrigerant is reduced from 6 to 14 0C to within 30 °C. After half a year of operation, the practice proves that by controlling the inlet temperature difference of the evaporator, not only the defect of the system cooling temperature instability is successfully solved, but also the frequency of the compressor start-stop shift is greatly reduced, and the power-saving effect is also very clear. From January to May 2005, the ammonia compressor saved 21,000 kW·h compared with the same period in 2004.
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