Sensitivity Analysis of Optimum Insulation Thickness for Pipe Diameters in Pipe Insulation with Air Gap for City Pipelines

Abstract

The use of effective insulation methods to reduce heat loss and minimize its economic and environmental effects in city piping systems is an important topic globally. This study uses a new method for insulation of city piping systems of an air gap around pipelines and optimizes the thickness of insulation for the pipe. With this aim, a mathematical model based on heat degree days and life cycle cost analysis is used. Thus, according to the insulation thickness, air gap and pipe diameter values, the objective functions of optimum insulation thickness, energy cost savings, and payback period are comparatively assessed. The results indicate that using an air gap causes an 89% and 57% fall in optimum insulation thickness values for small and large diameter pipes, respectively. Additionally, sensitivity analysis was completed for the objective functions in terms of parameters such as interest rate, discount rate, life span, unit cost of fuel, cost of insulation material per unit volume, heat degree day, and air gap values. Based on the study methodology, life span, air gap, and unit fuel cost parameters were shown to have a significant effect on the objective functions. When insulation with air gap is applied, together with reducing the optimum insulation thickness at least 72% (from 0.009 to 0.031 m), it increases energy cost savings at 74% (from 5.47 to 21 $/m-yr) for large diameter pipes and reduces the payback period at 78% (from 0.1 to 0.04 yr-m) for small diameter pipes. (c) 2019 American Institute of Chemical Engineers Environ Prog, 38:e13146, 2019