How to calculate the appropriate thickness of the heat exchange tubes

I. Calculation Principle of Heat Exchange Tube Thickness

How to calculate the thickness of the heat exchange tube? This is an important issue that needs to be addressed when designing heat exchange equipment. According to the theory of heat conduction, the relationship between heat flow density, heat conduction coefficient, surface temperature and thickness can be expressed by the following formula:

q = k × ΔT / δ

Where, q is the heat flow density per unit area per unit time, k is the heat conduction coefficient, ΔT is the temperature difference between the inside and outside of the heat exchange tube, and δ is the thickness of the heat exchange tube.

From the formula, it can be seen that there is a certain correlation among heat flow density, heat conduction coefficient, surface temperature and thickness. Therefore, when choosing and designing the heat exchange tube, these factors need to be comprehensively considered to determine the optimal thickness.

II. Factors Affecting Heat Exchange Tube Thickness

1. Surface Temperature of the Heat Exchange Tube

The surface temperature of the heat exchange tube is an important parameter that determines the heat conduction coefficient and heat flow density. The higher the surface temperature of the heat exchange tube, the greater the heat conduction coefficient and the greater the heat flow density, and a thicker tube wall is required to withstand greater pressure and thermal stress.

2. Heat Conduction Coefficient

The heat conduction coefficient is one of the important parameters in the calculation of heat exchange tube thickness. It is closely related to the material and surface condition of the heat exchange tube. The heat conduction coefficients vary greatly depending on the material and surface conditions, and specific analysis needs to be conducted accordingly.

3. Crack Factors

When there is a large temperature difference between the inside and outside of the heat exchange tube, the tube may undergo temperature deformation and even crack. Therefore, when choosing the thickness of the heat exchange tube, these factors need to be considered to ensure the long-term stable operation of the equipment.

III. Heat Exchange Tube Thickness Calculation Example

Given the temperature difference between the inside and outside of the heat exchange tube ΔT = 200℃, the pipe length L = 10m, the pipe diameter D = 100mm, the pipe material is stainless steel, and it is required to be able to reach a pressure of 1.6MPa under normal conditions, calculate the thickness of the heat exchange tube.

Based on the above parameters, we can first calculate the heat flow density q. Assuming the heat conduction coefficient k = 50W / (m·℃), then

q = k × ΔT / δ = 50 × 200 / δ

Since the design strength stress is not more than 160MPa, we can determine the pipe wall thickness through calculation. Assuming the elastic modulus E of stainless steel is 200GPa and the Poisson's ratio v is 0.3, then the pipe wall thickness can be expressed as t = DP / 2SE(1 - v^2)

Here, S represents the cross-sectional area of the pipe, E is the elastic modulus, and v is the Poisson's ratio.

By substituting specific parameters, the required wall thickness of the pipe can be calculated as:

t = 100 × 160 / (2 × 200 × 10^3 × 312.5 × (1 - 0.3^2))

t = 0.56mm

Through the above calculation, we can determine that the heat exchange pipe needs a minimum thickness of 0.56mm to meet the design requirements.

【Conclusion】

In summary, the calculation of the thickness of the heat exchange pipe involves many factors and requires comprehensive consideration to ensure the long-term stable operation of the equipment. When selecting and designing the heat exchange pipe, attention should be paid to factors such as heat flow density, heat conduction coefficient, surface temperature and thickness. Specific situations should be analyzed and calculated to select the appropriate thickness.