Thermal performance and moisture accumulation of fibrous mechanical pipe insulation systems operating at below-ambient temperature in wet conditions with moisture ingress

摘要

When pipes are used for chilled water, glycol brines, refrigerants, and other chilled fluids, energy must be spent to compensate for heat gains through the wall of the pipes. Higher fluid temperature at the point of use decreases the efficiency of the end-use heat exchangers and increases the parasitic energy consumption. Mechanical pipe insulation systems are often used to limit the heat gains and save energy in commercial buildings. Pipe insulation systems play an important role for the health of the occupied space. When a chilled pipe is uninsulated or inadequately insulated, condensation might occur and water will drip onto other building surfaces, possibly causing mold growth. The critical issue with cold pipes is that the temperature difference between the pipe and its surrounding ambient air drives water vapor into the insulation system, and condensation commonly occurs when the water vapor comes in contact with the chilled pipe surface. This article, as the first part, experimentally studied this issue for fibrous pipe insulation systems operating at below-ambient temperature. The moisture content and associated thermal conductivity of fiberglass pipe insulation systems were measured at various dry and wet condensing conditions with moisture ingress. Under dry conditions, the effect of cold pipe surface conditions and the presence of vapor jacket on the system thermal conductivity were compared and discussed in detail. Under wet conditions, accelerated type tests in the laboratory showed the propensity of moisture accumulation in several insulation systems due to the cylindrical configuration, split joints, and micro-imperfections in the jacketing system. The data in the present work showed that the thermal conductivity linearly varied with the insulation mean temperature and increased systematically when water vapor entered the pipe insulation system.