24 June 2014

ANALYSIS OF PIPELINE TRANSMISSION LOSSES OF THERMAL PACKETS IN AN URBAN THERMAL GRID


An urban thermal energy grid will allow buildings to meet thermal energy demand by taking advantage of more optimal heat sources installed in surrounding buildings such as
waste heat or unused heat generation capacity. Energy can be transferred on demand in the form of “thermal packets” of hot or cold water through a grid of pipelines. Short-term transient
heat losses as the pipes are heated or cooled and diffusion along the packet length must be accounted for in control and evaluation of the system.
The efficiency of transferring thermal energy in insulated water pipelines of various materials is evaluated through simulation and experiment. The temperature of the packet as a whole
degrades as it travels through the pipes. Initial results indicate the degradation of the packets can occur at the front and tail ends as “blunting” or the packet may retain a “sharper” shape but the temperature of the entire packet including its “core” tending to drop. Small scale
experiments over 25m pipe lengths reveal that heat transfer with system components can be significant. Large scale experiments are set to begin in summer 2014.