Optimising the location of a district-cooling pipeline in a rectangular trench

Steady-state rates of heat transfer to a cold horizontal pipeline within an atmospheric pressure, air-filled, horizontal rectangular cavity with relatively hot isothermal walls, have been determined experikentally. The optimal geometrical arrangement, i.e. that for which the least rate of heat is gained by the supply pipeline, occurs with a displacement ratio approximately equal to 0·67, the pipe being in the lower half of the cavity and midway between the vertical walls. The use of this configuration leads to significant energy savings (relative to employing the traditional arrangement with the pipe placed at half depth in the trench), without incurring any additional insulation costs.