Shandong Zhilin Environmental Protection Technology Co., Ltd.

Below is an introduction to the composition and working principle of the heating network heater

Release time:

2021-10-19 13:52

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Below is an introduction to the structure and working principle of the heating network heater. Structure of the heating network heater The heating network heater mainly includes the cylinder, heat exchange tube, circulating water inlet, circulating water outlet, steam inlet, condensate outlet, water-side vent, water-side safety valve, steam-side safety valve, steam-side vent, non-condensable gas inlet, manhole, water-side port, high-level condensate recirculation port, and steam-side drain port.

　　Below, we will introduce the composition and working principle of the heat network heater.

　　Heat network heater structure

Heat network heater

　　The heat network heater mainly includes the shell, heat exchange tubes, circulating water inlet, circulating water outlet, steam inlet, condensate outlet, water-side vent, water-side safety valve, steam-side safety valve, steam-side vent, non-condensable gas inlet, manhole, water-side opening, high-level condensate recirculation port, and steam-side drain port.

　　Heat network heater structure principle

　　The heat network heater in large power plants is a low-pressure condensing heat exchange equipment, equivalent to a condenser. Therefore, its structure should be similar to a condenser.

　　1. Sufficiently large steam passage

　　Including the passage into the steam inlet and piping system, please ensure there is a sufficiently large steam passage. Otherwise, the steam flow rate will be too high, causing impact on the heat transfer tubes, and increasing the flow resistance of the steam. When the flow resistance increases, the steam pressure in the heater will decrease, and the outlet temperature of the water supply will decrease. For example, large heat network heaters such as JR-1250 and JR-2600 have a large steam passage area, i.e., there is a large steam passage between the shell and the tube bundle, and between the tube bundles, equivalent to the steam passage of a condenser. The volume and weight of the condenser are very large, but the operation is stable, and there are issues.

　　2. The tube bundle needs reasonable support

　　Regarding the structure of the U-shaped tube, in addition to supporting it in the straight pipe section using baffles, please also install vertical support devices at the ends of the bends to prevent vibration and conduct vibration check calculations to prevent vibration. The theories for judging damage caused by heater vibration include the resonance theory, strength theory, and energy theory (or damping theory). Verification calculations are performed using three methods derived from these three theories, and all three must be satisfied. The Swiss BBC company's calculation only has 3 methods. This method sometimes cannot guarantee that the tube bundle will not vibrate.

　　3. The water flow volume should meet the requirements of a certain reserve.

　　According to the operating experience of heat network heaters in previous power plants, it is believed that a volume with a reserve of 2-3 minutes of flow rate should be set. Otherwise, the operation of the condensate system will become unstable. Therefore, the original design's water flow volume was small, and the condensate system was unstable, which was subsequently increased. The second-phase equipment introduced from Switzerland also increased the condensate volume and added a condensate well structure.

　　4. The form of the heat transfer tube

　　U-shaped tube heat exchangers compensate well for thermal expansion and do not need thermal expansion checks. However, it is inconvenient to clean and remove fouling from the tubes, and the tubes cannot be replaced; straight tubes facilitate cleaning and removal of fouling from the tube bundle, and any tube can be replaced arbitrarily. However, they lack thermal expansion compensation capability and require the installation of expansion devices on the shell, and calculations are performed through thermal expansion verification.

　　Based on these characteristics, fixed tube plates with straight tubes and shells with expansion joints are adopted, and a corrugated expansion joint is divided into two parts. The small ends of the two half-opened expansion joints are directly welded to the two end tube plates, and their large ends are welded to the shell with a larger diameter than the small end. The holes on the tube plate are equilateral triangles, leaving channels for steam to enter the tube bundle. The baffle is a circular supporting structure with claw-like teeth around it, fixed to the inner side of the outer shell by welding. This reflects the structural characteristics. Because there is a large annular space between the inner diameter of the shell and the outer diameter of the tube bundle, even if the steam enters the shell and flows longitudinally along the annular passage, due to the transverse passage of the tube bundle, the steam will also re-enter the tube bundle along the transverse passage; the entire circle of the baffle supports the tubes uniformly and evenly spaced (not an arched baffle); by welding the baffle and the inner side of the shell, the tube bundle and the shell are integrated, allowing the pipes to move longitudinally along the holes of the baffle; the pipe and the shell are integrated, allowing for relative movement, which can prevent vibration caused by pipe tightening and can also compensate for the thermal expansion difference between the shell and the tubes.

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Below is an explanation of the characteristics of the heating network heater