Insulation is provided in HVAC and Refrigeration systems on pipes, ducts, walls and roofs. The primary purpose of the insulation is to limit heat transfer. For example, in chilled water pipes, insulation is provided to limit heat transfer to the chilled water and to keep the water cold. In hot air ducts, insulation is provided to limit heat loss to the surrounding areas.
Insulation is characterized by its ability to conduct heat transfer and is rated by either a k-value, U-factor or an R-value. K-values are often used when rating pipe, duct or equipment insulation where R-values and U-factors are typically used to describe roof and wall insulation. Please refer to the Heat Transfer section for more detail on insulation for roofs and walls. This section primarily deals with insulation for pipes and ducts, specifically being able to determine the insulation requirements for a pipe or duct, in order to (1) Control Surface Temperature.
Controlling Surface Temperature: One important skill that the professional engineer must attain is to be able to determine the insulation required to keep the surface temperature of a pipe, duct, wall, roof or other piece of equipment within a set range. A common problem encountered in the HVAC and Refrigeration field is determining the required insulation for a chilled water pipe in order to stop condensation from forming on the surface.
The governing equation for this problem is that the heat transfer from the chilled water pipe through the insulation and to the outer surface is equal to the heat transfer from the outer surface to the ambient air.