- Author
-
Fang, J. B.
- Title
- Thermal Analysis of Directly Buried Conduit Heat Distribution Systems.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Sponsor
- Tri-Service Building Materials Committee, Washington, DC
Army Corps of Engineers, Washington, DC
Navy Naval Facilities Engineering, Alexandria, VA
Air Force, Bolling Air Force Base, DC
- Report
-
NISTIR 4365,
August 1990,
96 p.
- Distribution
- Available from National Technical Information Service
- Keywords
-
computer programs
|
direct burial
|
district heating and cooling
|
finite element method
|
heat loss
|
heat transfer
|
underground heat distribution system
|
thermal analysis
- Abstract
- The calculations of heat losses and temperature fields for directly buried conduit heat distribution systems were performed using finite element method. The finite element analysis solved two-dimensional, steady-state heat transfer problems involving two insulated parallel pipes which were encased in the same conduit casing and in separate casings, and the surrounding earth. Descriptions of the theoretical basis, computational scheme, and the data input and outputs of the developed computer programs are presented. Numerical calculations were carried out for predicting the temperature distribuitons within the existing high temperature hot water distribution system with two insulated pipes covered in the same metallic conduit and the surrounding soil. The predicted results generally agree with the experimental data obtained at the test site. The deviations between the predicted and measured values are found to range from 0 to 17 percent with an average of 6 percent. The rates of heat loss from two insulated pipes encased in separate conduits were calculated for different pipe sizes, fluid temperatures and insulation thickness. The results were compared with the predicitions from a steady-state, one-dimensional radiant heat conduction model. The discrepancies between finite element and radial conduction models in pipe heat loss values are discussed.