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Ideas and measures to improve energy station energy efficiency and system energy efficiency-Part 4
System Efficiency Improvement Measures
1. Heat source and hot water distribution
The heating energy consumption of buildings in hot summer and cold winter regions accounts for more than 30% of the annual energy consumption of HVAC systems. Therefore, energy conservation in heating conditions should also be paid attention to. The design improves energy utilization efficiency from the heat source side and hot water transmission and distribution.
1) The heat source of the air conditioner adopts a condensing boiler, which recovers and utilizes the sensible heat in the combustion flue gas and the latent heat of water vapor to improve the thermal efficiency of the boiler.
2) In terms of hot water transmission and distribution, compare and select the two methods shown in Figure 6 for the heating method and the temperature difference between supply and return water.
The factors that determine the superiority of mode 1 and mode 2 in terms of energy consumption mainly lie in the distance of transportation and the pressure drop of the plate heat exchanger. The length of the pipe network from the energy station to the service area of this project is relatively long. Even under the conservative assumption that the pressure drop on the primary side of the plate heat exchanger is 70 kPa and the pressure drop on the secondary side is 100 kPa, the water system transportation energy consumption of mode 1 is 18% lower than that of mode 2. When the pressure drop of the plate heat exchanger is less than the input value, the actual energy saving rate is higher. Mode 1 was adopted for this project.
The air-conditioning hot water and high-temperature cold water in this project share pipes. Since the hot water adopts a large temperature difference, the flow rate of the hot water is less than that of the high-temperature cold water, the specific friction resistance of the pipeline is small under the heating condition, and the pressure drop of the pipe network is only 25 kPa. The energy consumption of pipeline network transmission and distribution that can be reduced by using the secondary pump method for hot water transportation is quite limited, and the installation of the secondary pump will also bring about 30 kPa of additional valve parts and pipeline resistance in the machine room. Therefore, the hot water transmission and distribution adopts the first-stage pump method, which simplifies operation and reduces initial investment.
2. Low resistance design
Water system pressure drop is an important factor affecting energy consumption in transmission and distribution. System design should be based on the principle of reasonably reducing system resistance. Take corresponding measures in all aspects. For large-scale energy stations, the connection pipeline is complicated, and it is especially important to consciously reduce resistance. The project carried out refined design from two aspects of adopting low-resistance equipment and valves and optimizing pipelines.
1) Use low-resistance equipment and valves.
Combined with the selection parameters of various brands of chillers, reasonable guiding restrictions are placed on the pressure drop of the evaporator and condenser to avoid purchasing high-pressure drop equipment. Optimize the selection of valve parts, for example, the water pump inlet uses a T-shaped diversion filter to connect horizontal pipes and vertical pipes. This type of filter has a large effective cross-sectional area, and there are flow-stabilizing blades at the outlet. Compared with the conventional filter with the same function and an elbow, the pressure drop is reduced by 46%. The pipeline design adopts low-resistance pipe fittings such as long-radius elbows (elbows with a radius of curvature equal to 1.5 times the pipe diameter), downstream tees, etc.
2) Pipeline optimization.
Arrange the piping reasonably to reduce unnecessary pressure drop. Taking the layout of the first-stage pump as an example, the unit and the water pump are arranged in one-to-one correspondence and connected directly in and out, reducing the up and down elbows of the conventional design. Based on refined design, the whole process of the construction site is controlled, the interface elevation of the ordered equipment, the requirements of the vibration isolation counterweight of the pump are comprehensively coordinated, and the requirements of the floor elevation, foundation height, and vibration-damping pedestal height are coordinated, and the water pump and the main engine are realized. "One" layout. After optimization, the pipeline resistance in this section drops from 33.5 kPa to 10.6 kPa, which is a considerable drop.
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