Thermal analysis of annular space of vacuum insulation in steel jacketed directly buried heating pipeline

摘要

Heating pipeline employs vacuum insulation to improve the insulating effect and reduce the corrosion, and hence, increase the heat transfer efficiency and reliability of heating network, further, the building energy efficiency. Experiments were performed to measure the heat transfer of vacuum layer of steel jacketed vacuum insulated heating pipelines, at inner steel cylinder of 200～300 ℃, at the vacuum of 10～1013mbar,respectively. Methods to calculate the heat transfers and equivalent thermal conductivities of vacuum layer were developed based on experimental data and theory of aerothermodynamic for rarefied air. Results shows agreement with the experimental data for the error is below 8.6%. The heat transfer by convection in vacuum insulation of steel jacketed heating pipeline is not neglectable. The pressure in vacuum insulation should be controlled below 20mbar to achieve desirable insulating effect. All these may be helpful to develop a perfect vacuum insulated heating pipeline product.