utilidors will have a significant effect on the temperature distribution and will
result in lower predicted heat transfer rates.
The use of an effective conductivity for air in a numerical conduction analysis
will produce reasonably good temperature distributions on interior surfaces. How-
ever, the air temperature distribution will be in error. The procedure is relatively
insensitive to the effective conductivity, the pipe, and enclosure insulation domi-
nating the heat loss, at least for the cases investigated in this work.
A more efficient and robust numerical modeling approach is required. Two pos-
sible improvements are to (1) convert the solution procedure to a "segregated
method" where each of the governing equations are solved individually and a Pois-
son equation is substituted for the continuity equation, or to (2) incorporate an
upwinding scheme such as the Petrov-Galerkin method into the element quadra-
Some temperature data from actual utilidors are available; comparisons with
these data and numerical modeling of the entire soil mass should be done. Addi-
tionally, comparisons with an effective conductivity correlation in a transient
conduction model, including the soil mass, and compared with field data, may
also produce some interesting results.
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