Thread Content
This post was last edited by slll611 on 2016-6-24 at 20:50. Plate heat exchangers are being used more and more frequently these days, which makes it increasingly important to know how to select the right type. Below are some points to consider when choosing a plate heat exchanger: 1. Selection of plate type – The type of plate, whether it be flat or corrugated, should be determined based on the actual requirements of the heat exchange application. For situations with high flow rates and a tolerance for low pressure drops, a plate type with low resistance should be selected; conversely, a plate type with high resistance should be chosen. Based on the fluid pressure and temperature conditions, determine whether to choose a detachable or brazed type. When determining the plate layout, it is not advisable to choose plates with too small a surface area, as this may result in an excessive number of plates, lower flow velocities between them, and consequently a lower heat transfer coefficient. This issue is particularly important to consider in larger heat exchangers. 2 Selection of flow paths and channels A flow path refers to a set of parallel channels within a plate heat exchanger unit in which the fluid flows in the same direction, while a channel is the flow path for the fluid formed by two adjacent plates within a plate heat exchanger. Generally, several flow channels are connected in parallel or series to form various combinations of cold and hot medium pathways. The process combination form should be determined based on heat transfer and fluid resistance calculations, while meeting the requirements of the process conditions. Try to make the convective heat transfer coefficients in the cold and hot water channels equal or similar, thereby achieving the best heat transfer performance. Because the heat transfer coefficient attains a higher value when the convective heat transfer coefficients on both sides of the heat transfer surface are equal or similar. Although the flow velocities between the plates of a plate heat exchanger vary, the average flow velocity is still used in the calculations for heat transfer and fluid resistance. Since the nozzles of the single \"U\"-shaped process are all fixed on the pressing plate, they are easy to install and remove. 3 Pressure drop verification When designing and selecting plate heat exchanger units, certain requirements are generally imposed on the pressure drop; therefore, it is necessary to conduct a verification. If the verified pressure drop exceeds the allowable value, redesign and selection calculations must be carried out again until the process requirements are met.