Selection of finned radiator tube spacing and fin spacing
Under normal circumstances, the spacing and height of the finned tube heat exchanger mainly affect the fining ratio, which has a great relationship with the film heat transfer coefficient of the medium inside and outside the tube. If the heat transfer coefficients of the inner and outer films of the tube differ greatly, a finned tube with a larger fin ratio should be selected, such as steam heating air. When there is a phase change in one side of the medium, the difference in heat transfer coefficient will be greater, such as the exchange of hot and cold air. When the hot air drops below the dew point, a finned tube heat exchanger can be used. In the case of heat exchange between air and air without phase change, or heat exchange between water and water, bare tubes are usually more suitable. Of course, a low-finned tube can also be used, because at this time it is a weak heat supply coefficient, and strengthening either side of it has a certain effect. However, the effect of too large finning ratio is not obvious, and the best tube inner and outer contact area is strengthened at the same time, and threaded tube or fluted tube can be used.
The pitch of the fins is mainly to consider factors such as dust accumulation, dust formation, easy cleaning, etc., and at the same time, it must strictly comply with the equipment's pressure drop requirements. When arranging, the distance between the tube and the tube is not easy to be too large, generally> 1mm or more suitable for tube layout. In the process of heat exchange, when air flows through the finned tube heat exchanger, the front and back sides of the fin are mainly involved in heat exchange. There is only a small amount of radiant heat transfer in the middle of the two finned tubes, and the heat transfer effect is not obvious. Since this part has no fins and resistance, the air is easy to penetrate. In the process of air heating, the unheated cold air will neutralize the heated hot air passing through the middle of the fins, which reduces the heat exchange effect. Compared with foreign finned tube heat exchangers, tubes The spacing is only 0.5mm larger than the outer diameter of the fins, which shows the importance of the tube spacing when the fin tubes are arranged.