Principle analysis of monitoring system for cold and heat source equipment

Principle analysis of monitoring system for cold and heat source equipment

The building automation system is an integrated system platform, in which many subsystems have diverse functions and complex engineering. What is the principle of the cold and heat source equipment monitoring system as one of the many subsystems of the building automation system? The following editor will analyze the principle of the cold and heat source equipment monitoring system in detail with you.

　　Principle analysis of cold and heat source equipment monitoring system

　　 (1), the principle of cold source system monitoring

1. Water chiller: The working principle of the water-cooled heat pump unit under cooling conditions is exactly the same as that of the chiller, while the control of the air-cooled heat pump unit is simpler (there is no cooling water circulation system, and the outdoor unit of the air-cooled heat pump unit undertakes water cooling The cooling water circulation function of the heat pump unit, and the outdoor unit is controlled by the controller of the heat pump unit.

　　2. Chilled water cycle: The chilled water cycle of the building's air conditioning cold source system is shown in the left half. It sends the high-temperature chilled water circulating from the air treatment equipment on each floor to the chiller for cooling, and then supplies it to the air treatment equipment.

　　3. Cooling water circulation: the cooling water circulation of the building air conditioning cold source system is shown in the right half of the figure. Its main task is to release the heat absorbed by the chiller unit from the chilled water circulation to the outside.

　　4. Equipment linkage and group control of chillers: chillers are the core equipment of the entire building's air conditioning cold source system. The chilled water circulation and cooling water circulation are controlled according to the operating status of the chillers.

5. The frequency conversion control scheme of the secondary water pump of the chilled water circuit: As mentioned above, when the chilled water circuit adopts a constant flow pump, to balance the contradiction between the variable flow on the load side and the constant flow on the chiller side to prevent low load Under the situation (the load side coil water valve is closed at the same time) the impact of the water pump on the pipeline and the pump itself, a bypass circuit should be installed on the chilled water supply and return mains, and the pressure of the water pipe should be balanced by the opening of the bypass valve.

　　6. ​​Ice storage system: The basic idea of ​​ice storage is to use the low electricity price period at night to produce ice for cold storage, and to melt ice during the peak day for cold storage.

　　 chiller control:

　　1) Chiller start/stop control and status monitoring.

　　 2) The chiller fault alarm monitoring.

　　3) Hand/automatic control status monitoring of the chiller.

　　4) Chilled water outlet/return temperature monitoring, etc.

　　 Cooling tower control:

　　1) Cooling tower fan start/stop control and status monitoring.

　　 2) Cooling tower fan failure alarm monitoring.

　　3) Manual/automatic control status monitoring of cooling tower fan, etc.

　　1) Start/stop and status monitoring of the cooling water pump.

　　 2) Cooling water pump failure alarm monitoring.

　　3) Hand/automatic control status monitoring of cooling water pump, etc.

　　 chiller system control:

　　1) First, when an additional chiller needs to be started, it is necessary to determine which chiller to start. Similarly, it is the same when one needs to stop a chiller.

　　 2) Secondly, when a chiller needs to be started or stopped, first determine how many and which chilled water pumps, cooling water pumps and cooling towers should be added or stopped.

　　 (1) The refrigeration unit priority control strategy: Only the refrigeration unit is operated when the air conditioning load is less than the capacity of the refrigeration unit, and only when the air conditioning load is greater than the capacity of the refrigeration unit can the cold storage device supplement the insufficient part.

(2) Ice storage priority cooling control strategy: when the air-conditioning load is lower than the maximum ice-melting cooling capacity of the ice storage equipment, the ice-melting load is first assumed, and when the air-conditioning load is greater than the maximum ice-melting cooling capacity, then the refrigeration unit is put into operation to supplement .

　　(3) Fixed ratio cooling control strategy: This control strategy means that the ice storage device and the refrigeration unit output the cooling load in a fixed ratio to meet the demand of the building's air conditioning load.

(4) Optimized control strategy: This control strategy is based on the dynamic forecast of the load, under the constraints (including the maximum output cooling load of the refrigeration unit, the maximum cold storage capacity of the ice storage equipment, the maximum melting rate, etc.). Optimize multiple control objectives (including daily operating costs, air-conditioning load, remaining ice volume in a cycle, number of starts and stops of refrigeration units, etc.).

　　 (two), the principle of heat source system monitoring

1. Heat pump system heating working condition monitoring principle: The working principle and monitoring content of the heat source system corresponding to the heat pump unit is similar to its working principle and monitoring content in the cooling state, except that the position of the condenser and evaporator inside the heat pump unit can be passed through the four-way The valves are interchanged.

　　2. Principle of boiler system monitoring: boiler system equipment includes three parts: boiler unit, heat exchanger and hot water circulation.

　　 1) Monitor the operating status of the boiler and alarm for faults.

　　2) Monitor the flue temperature and boiler pressure of the boiler.

　　3) Monitor the alarm signal of the high and low liquid level of the make-up tank.

　　4) Real-time detection of boiler fuel consumption or gas consumption.

　　5) Monitor the operation status of the primary side water pump of the boiler, the pressure difference and the opening of the bypass valve.

　　6) The supply and return temperature of the boiler primary water.

1) Monitor the secondary water outlet temperature and return water temperature of each heat exchanger, adjust the primary hot water (or steam) regulating valve according to the outlet water temperature to ensure that the outlet water temperature is stable within the set value range, and alarm when the temperature exceeds the limit; conditional Detect the water flow on the secondary side to estimate the air conditioning load in winter.

　　2) Monitor the running status and fault signal of the hot water circulating pump, alarm when faults occur, and accumulate running time.

　　 water chiller:

　　Using compressors, condensers, evaporators and other equipment, artificially control the refrigerant gas-liquid state conversion, and the cycle is repeated, the refrigerant will continuously cool the chilled water, and at the same time, release the absorbed heat into the cooling water cycle.

　　 Water chiller monitoring content:

　　 Chiller start/stop control and status monitoring.

　　 Water chiller failure alarm monitoring.

　　 Hand/automatic control status monitoring of chiller.

　　 Chilled water outlet/return water temperature monitoring, etc.

　　 Chilled water system:

　　 The chilled water cycle of the building air conditioning cold source system, it will send the high-temperature chilled water circulated from the air treatment equipment on each floor to the chiller for cooling, and then supply the air treatment equipment. The monitoring content of this loop mainly includes the monitoring of the chilled water pump, the monitoring of various parameters of chilled water supply/return water and the control of the bypass water valve.

　　 Air conditioners, fresh air fans, and coil refrigerants are chilled water.

　　 Chilled water system monitoring content:

　　 The start/stop and status monitoring of the chilled water pump.

　　 Chilled water pump fault alarm monitoring.

　　 Hand/automatic control status monitoring of chilled water pump, etc.

　　 Chilled water supply/return water temperature monitoring.

　　 Chilled water supply/return main pressure monitoring.

　　 Chilled water circulation flow monitoring, etc.

　　Cooling water circulation:

　　 The cooling water cycle of the building air conditioning cold source system. Its main task is to release the heat absorbed by the chiller from the chilled water cycle to the outside. The monitoring content of this loop mainly includes cooling tower monitoring, cooling water pump monitoring, and cooling water inlet and return water parameters.

　　 Cooling water monitoring content:

　　 Cooling tower fan start/stop control and status monitoring.

　　 Cooling tower fan failure alarm monitoring.

　　 Hand/automatic control status monitoring of cooling tower fan, etc.

　　 Cooling water pump start/stop and status monitoring.

　　 Cooling water pump failure alarm monitoring.

　　 Hand/automatic control status monitoring of cooling water pump, etc.

　　 Linkage between equipment and group control of chillers

　　The chiller is the core equipment of the air-conditioning cold source system of the entire building. The chilled water circulation and cooling water circulation are controlled according to the operating status of the chiller.

　　 When starting the chiller, start the cooling tower, the cooling water circulation system, and the chilled water circulation system. When it is determined that the chilled water and the cooling water circulation system have been started, the chiller can be started.

　　 When the chiller is stopped, the stopping sequence is exactly the opposite of the starting sequence. Stop the chiller, stop the chilled water circulation system, stop the cooling water circulation system, and finally the cooling tower.

　　 The main heat source equipment of the building air conditioning system includes two kinds of heat pump units and boiler systems.

　　The working principle of water-cooled heat pump unit under cooling conditions is exactly the same as that of chiller.

　　The control of the air-cooled heat pump unit is simpler. There is no cooling water circulation system. The outdoor unit of the air-cooled heat pump unit assumes the function of cooling water circulation of the water-cooled heat pump unit.