U-tube Heat Exchanger Brief Introduction

U-tube heat exchanger is a kind of shell and tube heat exchanger, which is composed of tube plate, shell, tube bundle and other parts. each tube of U-tube heat exchanger is bent into U-shape, the import and export are installed on both sides of the same tube plate, the head is divided into two chambers with a partition plate, thus, each tube is free to expand and contract, and has nothing to do with other tubes and shells.

Advantages of U-tube heat exchangers

--- The tube bundle is free to float without consideration of temperature differential stresses and can be used in large temperature differential situations;

--- it has only one tube plate, a small number of flanges, few leak points and a simple structure;

--- U-tube heat exchanger is reliable in operation and low in cost.

Disadvantages of the U-tube heat exchanger

--- Cleaning inside the tube is more difficult. The utilisation rate of the tube plate is low as the tube needs to have a certain bending radius

--- The innermost layer of the tube bundle has a large tube spacing, and the shell course is easy to short-circuit. when the flow rate in the tube is too high, it will produce serious erosion of the U-shaped bend section, affecting its service life;

--- The inner layer of tubes cannot be replaced if damaged, thus the scrap rate is high.

Is the heat transfer efficiency of the U-shaped heat exchanger higher than that of the fixed tube and plate heat exchanger?

Not necessarily. Because the heat transfer efficiency of the heat exchanger is mainly determined by the k-value, and the shape of the heat exchanger has little to do with it.

1. affect the heat exchanger K value and heat transfer coefficient and thermal resistance of the heat exchanger tube material, such as ceramic, stainless steel, titanium, zirconium.

2. k value is also related to the heat transfer medium (such as air, water, steam, heat transfer oil, etc.) itself heat transfer capacity.

3. The heat transfer capacity of thermal convection is greater than that of heat conduction and radiation. In the operation of the heat exchanger, the three work together, mainly thermal convection. Forced convection between fluids is greater than natural convection, and turbulence is greater than laminar flow.

4. In a heat exchanger, for the same fluid, the phase change heat coefficient is greater than the non-phase change heat coefficient. For example, the coefficient of condensation of gas materials is higher than the coefficient of condensation of liquid materials.

5. heat exchanger tube bundle thickness also has an impact on the K value, heat exchanger tube wall every 0.1mm reduction, the total heat transfer coefficient increased 500-600w/(㎡ * K). Ltd. produces heat exchanger tube diameter of φ8, φ10, φ12, the thermal conductivity of the heat transfer interface is inversely proportional to the wall thickness of the heat transfer interface.

6. If the structure of the heat exchanger is reasonably designed, the cold and heat source can fully contact with the heat exchange surface, increasing the contact area, so that the material can quickly and reach the required temperature; on the contrary, if the structure of the heat exchanger is not reasonably designed, the structure tends to be high and easy to affect the k value.

7. heat exchanger cleaning maintenance is not appropriate, there will be a lot of scaling, thus affecting the heat transfer efficiency of the heat exchanger, we need to reduce the thickness of scaling, can improve the K value; heat exchanger easy to age and wear, the use of a long time will also affect the k value.