Stainless steel heat exchange tube has the following advantages: using 0.5-0.8mm thin wall pipe heat exchange tube, improve the overall heat transfer performance, under the same heat transfer area, the overall heat transfer coefficient is 2.121 and 8.408% higher than copper. Using high quality SUS 304 stainless steel, it makes a high hardness, the stiffness is also obvious enhanced. Therefore, it has a strong shock resistance and vibration resistance.
Due to the smooth inner surface of stainless steel tube, the boundary laminar layer thickness becomes thin, which not only enhance the heat transfer, and also improve the performance of anti fouling. In order to eliminate the welding stress, do the heat treatment with 1050 ℃ in the shielding gas. And adopts differential pressure leak test, pressure test to 10 mpa, 5 minutes without pressure drop.
1. Thermal conductivity. Copper tube thermal conductivity is 100W/m℃, stainless steel tube is 13W/m℃, which will affect the overall heat transfer coefficient. However, the wall thickness of stainless steel pipe can be reduced by 0.5~0.8mm, while copper pipe cannot be less than 1.2mm because of the strength, erosion wear and other reasons.
The inside and outside wall of copper tube is rougher than stainless steel, it is easier to scale, thus increased the heat resistance, which narrow the heat transfer coefficient gap of copper and stainless steel tube.
2. Convection heat transfer. Using stainless steel tube or copper tube, the tube flow rate is turbulent.
The biggest factor affecting convective heat release is the thickness of the bottom layer of laminar flow, because the heat transfer in the bottom layer of laminar flow is thermal conductivity, while the thermal conductivity of water is very low. Under the same flow state, the thickness of the bottom layer depends on the roughness of the inner wall.
There is oxide on the surface of copper, thus its roughness in inner surface is much larger than the stainless steel tube. The thickness of the copper tube laminar flow layer is thicker than the stainless steel tube, this makes the convection heat transfer coefficient ratio of the stainless steel tube larger than copper tube.
3. Long-term economics. As the operating time increases, the oxide layer of the copper pipe will become thicker and the heat transfer effect will become worse and worse. However, stainless steel is basically not oxidized, the oxidation rate is very slow. If the stainless steel tube heat exchanger and the copper tube heat exchanger are put into operation at the same time, the longer the running time, the economic efficiency of the stainless steel tube heat exchanger will be better and better than the copper tube. At the same time, the absorption capacity of copper pipes for impurities in the cooling water is much stronger than that of stainless steel pipes, which greatly reduces the economic efficiency of the equipment.