Heat transfer from a buried pipe has been a subject of great interest due to its many important engineering applications, which include the underground pipelines for oil and gas transport and the power cables. The problem considered in the present study has applications related to a radiant underfloor heating system in residence and industry. In the existing literature, heat transfer from a buried pipe has been considered for various heat transfer modes and configurations. For example, analytical solutions are readily available for heat conduction from one single cylindrical heat source or multiple heat sources, and the heat transfer results are often expressed in terms of the conduction shape factor. As for heat convection from an array of pipes, most of the existing studies have been focused on external crossflow with forced convection from a bundle of pipes with either aligned or staggered pipe arrangement. This area of research has received much attention due to its important industrial applications in the design of boilers and heat exchangers. On the other hand, studies involved natural convection from an array of pipes are relatively limited.

The problem considered in the present study is related to the simulation of underfloor piping systems suspended in the joist space beneath the subfloor. Natural convective heat transfer from a row of horizontal heated pipes embedded in a closed cavity filled with air has been numerically examined in this study. A two-dimensional steady-state model has been developed using ANSYS Fluent for the numerical simulation. A parametric study has been performed to investigate the effects of pipe spacing, pipe depth and pipe temperature on the flow patterns and heat transfer rates. The heat transfer mechanism from the heated pipes to the top surface of the air-filled cavity is revealed through the plots of streamlines and isotherms. The present numerical model has been developed and validated using a parallel experimental study. From the radiant underfloor heating application perspective, the results showed that a radiant heating system with pipes embedded at a shallow burial depth and placed closer together resulted with a more desired surface temperature distribution.

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