Selection and Selection of Operation Mode of Ice Storage Process in Ice Storage Air Conditioning Ice storage process selection:

Selection and Selection of Operation Mode of Ice Storage Process in Ice Storage Air Conditioning Ice storage process selection:

　　 During the operation of the ice storage air conditioning system, the refrigerator can have two operating conditions, namely, ice storage conditions and cooling conditions. In the ice storage condition, the low-temperature glycol solution cooled by the refrigerator enters the ice storage heat exchanger of the ice storage tank to cool and freeze the still water in the ice storage tank into ice. When the ice storage process is completed, The water in the entire ice storage facility will basically freeze completely. When melting ice, the system refluxes warm glycol solution after heat exchange through the plate heat exchanger into the ice storage heat exchanger, reduces the temperature of the glycol solution, and sends it back to the load end to meet the needs of the air conditioning cooling load.

　　 There are two kinds of processes in the glycol solution system: parallel process and series process.

　　1. Parallel process:

　　 In this process, the refrigerator and the ice storage tank are in parallel in the system, and when z* is large, the cooling can be combined. At the same time, the process can store cold, store and supply cold, only melt ice for cold, and cooler directly provide cold, etc.

　　①、Refrigerator ice storage

During the time period when the air conditioning system is not running (such as at night), the refrigerator automatically switches to the ice storage mode: close the V2 and V4 valves, open the V1 and V3 valves, so that the glycol solution is between the refrigerator and the ice storage tank cycle. With the extension of the ice making time, the glycol temperature gradually decreases, and the required amount of ice is frozen outside the tube.

　　②, ice storage tank for cooling

　　 When the ice storage tank is required to provide cold capacity by melting ice, the refrigerator stops running, but it still serves as a pathway for the system. The glycol solution is sent to the ice storage tank through the glycol pump, and the cooled glycol solution enters the plate for heat exchange. Close the valve 3, in order to control the temperature of the glycol entering the board change, set the V2 and V1 valves to the regulating state.

　　③、Refrigerator for cooling

　　 In order to maintain a higher refrigeration efficiency, when the refrigerator needs to be directly added to the refrigeration, it will operate according to the air conditioning condition. The glycol solution circulates between the refrigerator and the plate changer, the system closes V1, V3, and V4, and opens the V2 valve. The chilled water after the plate change and cooling is used to provide cooling to the user.

　　④, refrigerator, ice storage tank combined cooling

　　 In order to meet the cooling capacity during the peak period of air conditioning, the glycol solution is cooled twice, that is, the glycol solution is first cooled by a refrigerator and then cooled by an ice storage tank for a second time. Therefore, the temperature difference of the ethylene glycol solution before and after the plate change reached 7°C. In order to control the temperature of the glycol solution entering the board changer, adjust the valves V2 and V1 to achieve the goal.

　　2, series process:

　　 means that the refrigerator and the ice storage tank are in series position in the process, and a set of circulating pumps are used to maintain the flow and pressure in the system to supply the basic load required by the air conditioner. The series process is equipped with appropriate automatic control, and can also realize the switching of various working conditions.

　　 Parallel process has a better balance in terms of exerting the cooling capacity of the refrigerator and the ice storage tank. It only needs to turn on the primary pump with lower power when storing the cold at night, which is more energy-efficient and flexible in operation. The series process system is relatively simple, and the cooling is constant, which is suitable for smaller projects and large temperature difference cooling systems.

　　The ice storage system can use the host upstream internal ice melting tandem system with a large temperature difference, and the ice storage device uses an ice storage tube. Due to the low temperature of the glycol aqueous solution, it can ensure that the plate heat exchanger provides 3.5°C effluent water for the system while having higher refrigeration efficiency and lower initial investment. On the typical design day, the air conditioning cooling load is shared by the refrigerator and the ice storage tube. On the atypical design day, optimized control is used to meet the cooling load demand and reduce system operating costs to a minimum. When the system is cooling, the glycol solution is first passed through the cooler to lower the temperature under air conditioning conditions to maintain efficient operation, and then cooled by the ice storage cylinder to further reduce the temperature of the glycol solution. The glycol solution can reach a large temperature difference, so that the flow rate of the glycol solution in the series system under the same load condition is small. Therefore, the glycol circulation pump of the series system is smaller than the parallel system under the same conditions, which makes the equipment investment of the series system And the operating cost is better than the parallel system, and the series pipeline is simple and reliable.

　　 Ice storage air conditioner selection:

　　 Except for air-conditioning and cooling, the rest of the day is used for cold storage, which can reduce the capacity of the host to a minimum.

The determination of the cold storage ratio is a very important link. In the program design, the typical values ​​(such as 30%, etc.) are generally selected initially. After the preliminary selection of equipment, the initial investment and operation are calculated according to the relevant local power policy. And consider other factors to finally select a better ratio value.

　　 Ice storage tank calculation:

　　Ice storage tank capacity: Q′=n2×q×T2

　　Plate heat exchanger selection: F=Q/(K×Δtm)

　　 In the formula, Q is the total heat transfer; K is the heat transfer coefficient; Δtm is the logarithmic average temperature difference;

　　Water pump:

In ice storage system, due to the high price of ethylene glycol, the sealing performance of the water pump is higher. It is generally recommended to use a water pump with a mechanical seal, which can reduce leakage or almost no leakage.

　　 Water pump selection:

　　According to the process, it is determined to meet the z* large resistance and flow rate under various working conditions; in order to achieve the purpose of energy saving, try to choose as many pumps as possible.

　　 The project adopts parallel process, primary pump flow=Q/C×Δt

　　Head P (estimated) = P host + P cold storage tank + P pipe + P valve

　　Head P=P heat exchanger+P cold storage tank+P pipe+P valve

　　 After selecting the pump type, it is necessary to cooperate with the automation professional to check the flow and resistance distribution under various working conditions, and whether the adjustment ability of the three-way valve can meet the requirements of the working conditions.

　　 Consider the following points:

　　① Adopting the series system upstream of the main engine, the upstream return water of the main engine flows through the main engine first, so that the main engine runs at a higher temperature, which improves the efficiency of the compressor and reduces energy consumption.

　　②. Standard ice storage tank for ice storage device. The standard ice storage tank has the following advantages:

　　A. While ensuring thermal conductivity, it completely eliminates potential corrosion hazards and is light in weight;

　　B. The incomplete freezing type is adopted, which can provide a stable low-temperature carrier refrigerant, reduce the flow rate of the circulating water pump and the pipe diameter of the corresponding pipeline, and reduce the initial investment;

　　C, external icing, no internal stress, long service life;

　　D, large heat transfer area, stable freezing and melting rate;

　　E, the icing thickness is thin, and the refrigeration host has high operating efficiency.

　　③. When designing combined cooling on the design day, the main engine priority mode is adopted, and the main engine has been running at full capacity, the unit utilization rate is high, the capacity of the main engine and the cold storage coil is the smallest, and the investment is the most economical.

　　④. All pumps are imported high-quality products with frequency conversion operation. During the entire cooling period, most of the time is part load, and the water pump has an obvious energy saving effect through stepless speed regulation, frequency conversion.