ASME STP-PT-079:2016 pdf free download

ASME STP-PT-079:2016 pdf free download.LOCAL HEATING OF PIPING: THERMAL ANALYSIS.
The effect of contact resistance must be included to obtain the proper temperature distribution. In the case of the piping heating system. the contact resistance must he included between the heating layer and piping to obtain the physical temperature distribution.
Contact resistance (or conductance) is a function of the contact area between two bodies on a microscopic scale. For the piping system. this contact resistance is a function of the heating element size, element geometry, element layout (pattern), contact pressure (“tightness” of the wrap), pipe size, and pipe surface condition (including roughness and cleanliness). Unlike the pipe, the insulation blanket can conform easier to the heating elements, resulting in a different contact resistance.
When solving the CHT problem using CFD, the thermal contact resistance can be directly specified at a contact interface. Values of thermal contact resistance are difficult (or impossible) to determine analytically. and therefore are typically determined through experimental measurement. For this analysis, the themial contact resistance value was the “tuning” parameter used to match the computational solution to experimental measurements. Using thermal contact resistance as a tuning parameter allows the heating layer to be treated as uniform, rather than having to include detailed clement layouts in the models.
Note that since the actual temperature distribution is a function of the thermal contact resistance, which is a function of the particular heating elements used, the results are strictly valid only for the exact equipment used for the heat treating experiments. Other heat treating providers, alternative equipment. or alternative designs could impact the thermal resistance, and thus the resulting thermal distribution. ft is suggested that the heat treating experiments be repeated using alternate equipment or an alternate provider.
Heat flows from the heating element into the piping and to the insulation via conduction. Heat is then lost to the surroundings via natural convection and radiation. Heat is applied to the system through a prescribed power input governed by a series of temperature probes. These temperature probes correspond to thermocouples used for control zones during PWHT. The power input is then adjusted such that the temperature probes achieve the prescribed PWHT’ temperature. The boundary conditions for the system areshown below. The top boundary of the ambient domain was modeled as a pressure outlet so that air couldcirculate in and out of the model as needed without adding convection in the area of interest..