Views:0 Author:Site Editor Publish Time: 2021-04-14 Origin:Site
The heat exchanger is a device that transfers part of the heat of the hot fluid to the cold fluid, also known as the heat exchanger. Heat exchangers are general equipment in chemical, petroleum, power, food and many other industrial sectors, and they occupy an important position in production. In chemical production, heat exchangers can be used as heaters, coolers, condensers, evaporators and reboilers, etc., and are more widely used.
Heat exchanger classification:
According to the heat transfer method, it can be divided into three categories: partition type, hybrid type, heat storage type (or heat recovery type); can be divided into compact type and non-compact type according to the compactness of its surface.
How does the heat exchanger perform heat exchange?
The heat exchange system usually conducts heat exchange in two ways: heat conduction and convection. Heat conduction is a common way of heat transfer in which the relative parts of the fluid do not occur during the process. Displacement; Convection is a process of heat transfer caused by the relative displacement of various parts of the fluid. Convection is divided into forced convection and natural convection. Forced convection is the use of mechanical energy (such as stirring) to convection the fluid and transfer heat.
Tube heat exchanger overall structure:
The tube heat exchanger is different from the plate heat exchanger in that it has no contact points on the product channel, so that it can process products containing certain particles. The maximum diameter of the particles depends on the diameter of the tube. In UHT processing, tube heat exchangers take longer to run than plate heat exchangers. From the point of view of heat transfer, tube heat exchangers have lower heat transfer efficiency than plate heat exchangers.
Tube heat exchanger working principle:
The commonly used multi-pipe tube heat exchange is based on the principle of the traditional tube-and-tube heat exchanger. The product flows through a set of parallel channels, and the supplied medium surrounds the tube and passes through the spiral on the tube and the shell. Corrugation, turbulent flow is generated, and effective heat transfer is realized.
Tubular heat exchanger specifications of different specifications/modes may be used in the same section: including the diameter of the outer casing-the diameter of the inner tube ~ the number of the inner tube-the total length mode: There are four common modes: ABCD, Mainly determined by the position of the medium inlet and outlet on the outer casing.
Necessity and design principle:
The correct heat treatment requires the milk to be kept at the sterilization temperature for a certain period of time, which can be achieved by an external holding tube. If the flow rate and the inner pipe diameter of the holding pipe are known, the appropriate pipe length that meets the holding time can be calculated.
Due to the uneven flow velocity distribution in the tube, the flow velocity of some milk particles is larger than the average. In order to ensure that the particles with the fastest flow rate can also be fully pasteurized, an efficiency factor must be used for correction. This coefficient depends on the design of the holding tube, usually between 0.8 and 0.9.