Why in water coolers is the circulating water usually introduced at a low level and discharged at a high level?
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Are all cold flows low in entry and high in exit? Why? Are there any special circumstances?
Low inlet and high outlet pressure are used to ensure that the cold stream fills the heat exchanger, preventing gas from occupying space and affecting the heat exchange area
Cooling water enters at the lower level and exits at the higher level, which facilitates exhaust
From the perspective of molecular motion, the higher the temperature, the faster the molecules move. When molecules first enter the heat exchanger, their temperature is low and their movement speed is slow; as the heat exchange time increases, the temperature of the molecules rises and their movement speed accelerates. Molecules in the upper layer have a higher temperature and move faster, while those in the lower layer have a lower temperature and move more slowly. To prevent molecules from moving in the opposite direction and causing gas-liquid collisions, the cold flow always moves from low to high. This prevents the higher-layer molecules from moving too rapidly and turning into a gaseous state, thereby occupying space and affecting the heat exchange area. It can also be thorough heat exchange through cold flow. Hope this helps
It is related to the direction of heat flow, and is generally arranged in counterflow.
As a supplementary note, in terms of heat exchange efficiency, according to what the original poster said, the circulating water in the water cooler flows through the shell side, and it is usually a single-pass system. If the tube side also operates in a single-pass manner, there are two possible scenarios: if the water enters the tube side from above and exits from below, it constitutes a counter-current arrangement, which results in better cooling efficiency. However, if the water enters the tube side from below and exits from above, and the circulating cooling water still flows from low to high, this will affect the cooling efficiency； If the pipeline system has multiple processes, the flow direction of the circulating cooling water has little impact. Of course, it is also related to the placement of the devices within the system.