When designing a finned tube heat sink, there is a thermal contact resistance between the tube and the fin flange, and the effect of this thermal contact resistance is not always negligible relative to the total heat transfer thermal resistance. heat. Especially in the mechanical expansion tube tube fin heat exchanger, the contact thermal resistance cannot be ignored, this type of heat exchanger is generally used in low pressure conditions, such as air conditioning and engine industry supercharged to cool the intake air heat exchanger. In the assembly process of the heat exchanger, the initial interference, the microhardness of the contact surface of the softer material, the contact area and the contact pressure are parameters that determine the contact thermal resistance. Choosing the correct size of the expansion core optimizes the degree of contact of the contact surface. Over the past three decades, researchers have developed the correct experimental method to measure thermal contact resistance. One of them, described by Nho et al., is an experiment to measure contact resistance in a vacuum. In a typical experiment, they found that the contact thermal resistance between the tube and the fin was 17.6% to 31.5% of the total resistance in a vacuum environment.
The fin tightly wrapped on the round tube by tension The circular fin tube is generally the aluminum fin is wound on the steel tube by tension, and the contact thermal resistance increases rapidly with the working temperature, so when Use the circular ring fin tube, the operating temperature is limited to less than 100 degree C, otherwise the stress will be reduced, resulting in loose fins, because aluminum has high thermal expansion. Integrally Laminated Finned Tubes For integrally laminated finned tubes, regardless of temperature and pressure, there are no problems related to thermal heat transfer resistance and tube integrity at the fin and tube junction. However, finned tubes for certain geometries can only be achieved through the expansion process.
General narrative; The contact thermal resistance of finned tube radiator is related to the temperature and fin processing technology.
