Multipole Method to Compute Heat Losses from District Heating Pipes

• The district heating industry is currently searching for new installation fashions for district heat distribution networks in order to decrease the cost of installation. The heat losses cause a large part of the lifetime cost and environmental impacts of district heating networks. This paper presents how the multipole method can be used for quick and accurate determination of heat losses from different installation alternatives of one or more insulated pipes in the ground. The multipole method utilises the cylinder geometry and the fact that real and imaginary parts of analytic functions satisfy Laplace equation to solve steady state heat conduction problems around pipes. The problem is solved in complex coordinates by using line sources and multipoles at the pipes. An equation system for the strengths of the line sources and multipoles is obtained. The equation system may be implemented in Mathcad or similar. Within negligible computer time a result of very high accuracy is obtained. As an example heat losses from two pipes in the ground are calculated. Two laying alternatives are studied: side-by-side and one pipe placed on top of the other. As heat is lost through the ground surface the total heat loss will increase slightly for shallower laying of the pipes and for the supply pipe put on top of the return pipe. Influences of the input parameters are studied for the side-by-side laying case.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Samhällsbyggnadsteknik -- Husbyggnad (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Civil Engineering -- Building Technologies (hsv//eng)

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