Factors affecting the heat transfer coefficient of wastewater evaporators

  The heat transfer coefficient of different types of wastewater evaporators varies. Even for the same wastewater evaporator, its heat transfer coefficient varies with the temperature, flow rate, and surface cleanliness of the cooled medium. In summary, there are several factors that affect the heat transfer coefficient, including: ① the heat transfer temperature difference between the refrigerant and the cooled object; ② The method of supplying liquid to the evaporator tube; ③ The cooled medium; ④ The fluid velocity passing through the surface of the coil and the flow velocity of the refrigerant inside the tube, ⑤ the relative clearance degree on both sides of the heat transfer surface.

When refrigerant vapor is completely condensed into liquid by cooling water or air in the condenser, the liquid at this time is a saturated liquid. If the saturated liquid is further cooled in the condenser (or subcooler), the temperature will be lower than the saturation temperature It becomes a supercooled liquid. The difference between saturation temperature and subcooling temperature is called subcooling, and the subcooling of a refrigerant is generally around 5 ℃. The supercooling of refrigerants is very beneficial for improving the refrigeration coefficient.

It can also reduce throttling losses when passing through throttling components and improve the refrigeration coefficient. In order to supercool the refrigerant, in addition to ensuring the maximum flow and pressure of the cooling water, it is also necessary to use cooling water with lower temperature as much as possible; For air-cooled condensers, it is necessary to ensure air flow velocity and flow rate, and use air at lower temperatures as much as possible.