Because plate heat exchangers have superior performance and low cost compared with shell-and-tube heat exchangers, they have been widely used in food industry, chemical reaction process and other industries. Plate heat exchangers have been used in the field of air conditioning as condensers and evaporators, which have led to great development.What is the reason for the large pressure drop of the plate heat exchanger?
(1)The running system piping is not properly purged.In the newly installed system piping, many dirt (such as welding slag) enters the interior of the plate heat exchanger.Due to the narrow cross-sectional area of the plate heat exchanger, sediments and suspended solids in the heat exchanger accumulate in the corner holes and the diversion zone, resulting in a large reduction in the flow passage area and a major pressure loss.
(2) The area of the plate heat exchanger is small when it is selected. The flow rate between the plates is too high and the pressure drop is too large. In 2010, our factory provided BH100M plate heat exchanger for users, which is used for central heating system of water-water heat exchange. The design temperature of primary water supply is 130 °C.When designing the heat exchanger, the heat transfer coefficient is high, close to 6300w/(m2·K), and the practical application is 4500w/(m2·K).At the same time, the design unit has a large flow margin when selecting the pump, which causes the flow rate between the dielectric plates on the secondary side of the heat exchanger to exceed 1.5m/s, and the actual operating pressure drop is 0.2-0.3 MPa, which makes the secondary network water pressure balance imbalance.
(3) After the plate heat exchanger is operated for a period of time, the surface fouling of the plate causes excessive pressure drop.The plate heat exchanger is a heat exchange system in which water is used as a heat carrier. When the temperature rises, the salt in the water will crystallize out from the water and adhere to the surface of the heat exchange tube to form scale. When the pH of the water is high, scale precipitation can also occur.In the initial stage, the scale will be relatively soft, but as the thickness and hardness of the scale increase, it will adhere firmly to the surface of the heat exchanger, resulting in a decrease in heat transfer efficiency, a decrease in flow rate, and an increase in energy consumption.