15 Heat Transfer and Insulating a Water Pipe

Protecting water pipes from freezing requires transient heat transfer calculations and extensive knowledge of the thermo physical properties of insulating materials. Under severe environmental conditions, insulating the water pipe alone might not be sufficient to prevent it from freezing. Other protections, such as running water in the pipe or heating tape around the pipe, might be necessary. In this heat transfer study, a long pipe with an insulation layer wrapped around it is considered. The interface between the pipe's outer surface and the insulation inner surface is assumed to be in good contact, with no air gaps or other imperfections to cause any contact resistance. The pipe is filled with stationary water, and is only exposed to the environment where there is convection heat transfer between the outer surface of the insulation and the environment. The time that it takes the water in the pipe to start freezing is analyzed, and its sensitivities to governing independent variables are investigated.