Optimization Of The Tube Pitch Of The Fin-Tube Heat Exchanger

The heat exchanger is the core equipment to realize the heat exchange. It plays a very important role in the power production system, metal smelting system, and petrochemical industry and so on. Compared with the plate and plate-fin heat exchanger, the tube- fin heat exchanger was used widely. At the same time, the fin-tube heat exchanger has the advantages of simple manufacture, low cost, easy assembly and so on. The fin-tube heat exchangers are used in air conditioning systems, usually, air flows in the fin side and water or refrigerant flow in the tubes. The air-side resistance comprises 70% of the total resistance of the fin-tube heat exchangers. The performance of the air-side determines the heat exchanger’s all performance. In the past, the research on improving the heat transfer performance is mainly focused on two parts. One method is trying to increase the area of the heat exchanger in the limited space, such as reducing the fin pitch. Another is enhancing the capability of heat transfer by different ways, such as adding vortex generators, using shaped tube and so on. When fluid flows through the heat exchanger, the larger the flow resistance is, the more energy is consumed. How to improve the heat transfer capacity and reduce the flow resistance at the same time is the main task of the heat transfer enhancement technology. The tube spacing is a parameter of the heat exchanger, no matter whatever type of fin is, tube spacing will have a great impact on the overall performance of the heat exchanger. The overall efficiency of the heat exchanger can be improved effectively by selecting appropriate pipe spacing with the same materials.In this paper, we select the numerical model to find the effects of the tube spacing of heat exchanger on heat transfer and flow resistance under the condition of uniform wall temperature. We chose four rows of tubes as the model and use the dimensionless parameters. By selecting different model parameters, we can find the influence of the tube spacing on the fluid flow and heat transfer characteristics, based on these characteristics the analysis of the optimum the tube spacing was carried out.The results show that different tube spacing can affect the flow field distribution in the channel of the heat exchanger, the Nu and f reduced with increasing the tube spacing. With increasing the tube spacing, the change tends become smooth, which means the influence of tube spacing on fluid flow and heat transfer decreases with further increase the tube spacing. At the same time, increasing the tube spacing can better improve the resistance performance of the heat exchanger. When the heat exchanger takes the same material cost, the heat exchanger has a better performance when the ratio of the transverse tube pitch and the longitudinal tube pitch is in the range of 1.5 to 1.7. Through studying of the heat exchanger with the actual size of 1800 mm × 88 mm × 2000 mm, we find the heat transfer coefficient K, the pressure drop ?p and the fin efficiency ηf reduced with increasing the tube spacing. The heat transfer capability and the heat transfer efficiency can be promoted by reducing the tube spacing regarding of the flow resistance constrains.