Issues with instrument electric heating
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This post was last edited by zhoudingshengs on 2024-1-29 at 13:30. Discussion: 1. A steam pressure measurement pipeline with a length of 15 m and an outer diameter of 14 mm; the temperature of the fluid inside the pipeline ranges from 20 to 80°C, while the lowest ambient temperature is -30°C. The insulation material used is ultra-fine glass wool, with a thermal conductivity of 0.033 W/(m·K), and the thickness of the insulation layer is 25 mm. Which type of electric heating tape should be used? What should be the heat dissipation rate of the pipeline?
When selecting an electric heat tracing cable, it is necessary to consider ensuring that the pipeline does not freeze and meeting the requirements regarding the temperature of the medium. The basic steps for calculating the heat dissipation of a pipe are as follows: 1. Calculate the thermal resistance from the pipe wall to the environment: \ where \( h_o \) and \( h_i \) are the convective heat transfer coefficients on the outside and inside of the pipe, respectively; \( d_o \) and \( d_i \) are the outer diameter after insulation and the original outer diameter, respectively; \( k \) is the thermal conductivity of the insulating material. 2. Calculate the heat dissipation: \ where \( \Delta T \) is the difference between the temperature of the fluid in the pipe and the ambient temperature. 3. Select an appropriate electric heating tape based on the actual operating conditions of the pipeline. On this basis, the specific calculation method is provided: – Determine the difference between the temperature of the medium inside the pipe and the lowest ambient temperature: \( \Delta T = T_{medium} - t_{0} = 80℃ - (-30℃) = 110℃ \). - Calculate the outer diameter of the pipe after insulation: \( d_o = d + 2 \cdot \text{insulation thickness} = 14mm + 2 \cdot 25mm = 64mm \). - Assuming the convective heat transfer coefficient \( h_o = 10 W/(m^2 \cdot K) \) (external natural convection), since the convective coefficient of the fluid flowing inside the tube is usually high, the \( h_i \) term can be neglected. - Calculate thermal resistance: \ \ - Calculate heat dissipation: \ where L is the length of the pipe. By following the above steps, it is possible to calculate the required power for the electric heating tape as well as the heat dissipation of the pipeline. It should be noted, however, that these calculations are simplified; when selecting an electric heating tape in practice, factors such as its maximum maintainable temperature, maximum usable length, and safety factor also need to be taken into account. Under normal circumstances, a professional manufacturer should be consulted for detailed design. .
For this item, it’s sufficient to loosely wrap it with a regular electric heating wire, or tie it directly to the pipe wall, and then cover it with insulation material. For reference.
It can’t be calculated; a heating strip needs to be installed, as the pipes become very hot during drainage and exhaust, so a high-temperature strip is required to prevent damage
1. Choose a constant-power single-phase belt. 2. The heat dissipation rate is approximately: 11W/m
Basic knowledge----Instrument heating knowledge.
I majored in process engineering; it was calculated that a low-temperature type electric heating tape should be used, with a heat loss of 13.8 W/m. The calculations were carried out in accordance with HG/T20549
I first wrap a layer of insulation material, then cover it with heat-shrink tubing, and depending on the operating conditions, I add more layers of insulation material to prevent the heat-shrink tubing from being damaged.
The construction work in our company is outsourced; for any insulation that requires heat tracing, heat tracing tape must be applied first, and then the insulation is installed. If we ask the construction team to apply heat tracing along with the insulation, they refuse to do it...