Thermal and economic analysis of preinsulated and twin-pipe heat network operation

Abstract

This study focuses on the economic analysis of the heating network modernization by using preinsulated pipes and twin-pipes. The cost analysis is based on different type, diameter, and technological diagrams of different heating network pipe variants (from DN25to DN100) and various types of insulation. Net present value (NPV) analysis comparing a five variants of the heating network pipes (Case 0: Pipes with insulation PUR standard; Case 1: Pipes with insulation PUR plus; Case 2: Pipes with insulation PEX standard; Case 3: Twin-Pipes with insulation PUR; Case 4: Twin-Pipes with insulation PEX). The value of NPV, which is the highest (NPV = 7000 €, DN65, case 2 and NPV = 5200 €, DN50, case 4) among presented variants is the best choose to consider during the investment. Despite the higher prices of Twin Pipe system, they are more profitable due to shallow heat transfer losses. Heat losses are calculated for various heating networks, including preinsulated and twin-pipe heating networks. The remaining heat loss calculation is based merely on temperature levels and thermal resistance factors (in the ground), determined using the pipe dimensions and materials. It is found that the most cost-effective from an economic point of view is the use of TwinPipe system. These pipes are more expensive, but the heat losses that occurs during their use are much smaller compared to preinsulated pipes. Short return time of such an investment (6–7 years) with 100 m of pipe installed and positive NPV causes that this type of pipes is the best investment in the case of district heating networks. The results shown that Case 3 (PEX insulation) is more economicaly beneficial than Case 4 (PUR insulation).