09-02-07 Topic — Classification of convective heat exchangers (prizes for participation)
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Let’s discuss the classification of convective heat exchangers, based on the shape and structure of the heat transfer surfaces, as well as the criteria for selection and factors to consider in design! Note: This topic was provided by a member of Gekiju wa Fukkō. The provider is requested to pay close attention and provide the correct answer or a summary within 24 hours. This post was last edited by Lan Meng on 2009-2-7 08:37.]
Based on shape and structure, they can be classified as: (1) shell-and-tube heat exchangers. Cannular, shell-and-tube, submerged, spray, finned. (2) Plate heat exchanger. Jacketed, flat-plate, plate-type, spiral-plate, finned-plate, shell-and-plate. (3) Heat pipe heat exchanger. Multi-chamber rotary, centrifugal, gravity heat pipe, and centrifugal heat pipe types – Selection criteria: 1. It is necessary to meet the requirements of the process conditions. The material and structural type of the heat exchanger are determined by taking into account various process factors such as pressure, temperature, physicochemical properties, and corrosivity. 2. High heat transfer efficiency: To improve heat transfer efficiency, heat exchangers must increase the heat transfer coefficient of the fluid and reduce thermal resistance. This issue must be fully considered when determining the structural type of the heat exchanger. If the heat transfer coefficients of the two fluids involved are similar and the temperature difference is not large, a shell-and-tube heat exchanger can be chosen ； If the temperature difference is large, a shell-and-tube heat exchanger equipped with expansion joints should be selected ； If the temperature difference is large, a floating-head heat exchanger should be chosen ； If the heat transfer coefficients of the two fluids differ significantly, and one of the fluids is a gas, a finned tube heat exchanger should be selected ； If both fluids are gases and their heat transfer coefficients are low, a plate-fin heat exchanger should be selected. 3. The fluid resistance loss should be low. The level of fluid resistance loss in a heat exchanger is directly related to the amount of energy consumed. Although increasing the flow velocity can improve the heat transfer coefficient, the high energy consumption required by the pumps or fans used to move the fluid makes it uneconomical. Therefore, the flow velocity of the fluid should be appropriate; relevant design manuals can be consulted to determine a suitable flow velocity. This post was last edited by jannes on 2009-2-7 11:58.]
The main modes of heat transfer include thermal conduction, convective heat transfer, and radiative heat transfer. Most heat exchangers transfer heat through thermal conduction; aside from the convective heat transfer in air-cooling fans and the convection chambers of heating furnaces, there are few other forms of convective heat transfer. I’m not sure whether these methods are similar to the convective heat exchangers mentioned by the moderator, and I hope we can continue this discussion!
Most heat exchangers are of the convective type. Convection mainly refers to an object separating the fluids on both sides. Heat is transferred across the two sides by convective heat exchange. Conventional shell-and-tube heat exchangers (including various configurations), plate heat exchangers, and air coolers. They are all types of convective heat exchangers; to distinguish them, here are a few examples of heat exchangers that are not convective: heat pipe heat exchangers, regenerative heat exchangers, direct contact heat exchangers, and radiant heat exchangers.
Convection refers to the mode of flow of fluids within a heat exchanger. This type of heat transfer is used in most heat exchangers in order to facilitate efficient heat exchange and achieve heat transfer with a small temperature difference
We use coiled tube and plate-fin heat exchangers