Negative pressure at the return water vent of the high-position circulating water heat exchanger
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I have a high-mounted circulating water heat exchanger in my workshop, on a platform about 25 feet high. When the return pipe is vented and air starts to flow in, what’s causing that? All the return pipes in Shangshui are 1000 in diameter. Does drawing in air from the inside before draining water have an impact on heat exchange? Please advise, experts! ? ?
The water returns to the main circulating water pipe; the height difference creates negative pressure in the return pipe. This can cause the outlet valve of the heat exchanger to stick, and drainage before the valve will result in water flowing out
Well, these are basic concepts of fluid dynamics. Your question assumes that the pressure of water as it passes through the device at the higher point is 0 barg, or a slightly positive pressure. But at the current temperature, as long as the pressure is higher than the saturation pressure, fluidity can be maintained. Basic principles of chemical engineering show that the so-called air absorption you mentioned does not exist; air enters only when the manual valve is opened, and none enters if it is not opened. Pay attention to the logical order. However, if the pressure at the top of the heat exchanger is too low, it may cause vaporized water to form in the pipeline leading from the heat exchanger to the lower sections, resulting in water hammer effects. It depends on your pressure and the temperature of the water being replaced; in very rare cases with high-temperature outlet water (70°C), the water hammer phenomenon is quite severe. . . . .
The pressure of the circulating water supply is too low, so water cannot reach the higher areas. Increase the supply pressure or reduce the return valve setting
Water can of course go up; otherwise, how can heat exchange take place?