Determination of annual heat losses from heat and steam pipeline networks and economic analysis of their thermomodernisation Tadeusz Kruczek * Institute of Thermal Technology, Silesian University of Technology, Konarskiego 22, 44-100 Gliwice, Poland article info Article history: Received 22 November 2012 Received in revised form 3 August 2013 Accepted 9 August 2013 Available online 10 September 2013 Keywords: Pipelines Thermal insulation Heat losses Infrared camera Thermomodernisation abstract The paper presents a method of evaluation and selective thermomodernisation of overhead thermal pipeline networks. The expression “thermomodernisation” is used for determination of all those activ- ities that deal with improvement of heat insulation features of the pipelines under consideration. The method is particularly useful for extensive and complex heat or steam pipelines. A novel method for the determination of annual heat losses from overhead pipelines into the environment has been developed in the work. The heat losses from the pipelines are generated during the whole year. The proposed method is based on the concept of one-off examination of the pipeline under consideration by means of a thermovision camera, performed in existing weather conditions. An example of an analysis has been carried out and results are presented for an existing industrial pipeline network. In this analysis the whole pipeline network was divided into segments characterised by identical technical features. To determine the annual heat loss, the operation of the considered pipeline during the whole year in different meteorological conditions was simulated numerically. Next, economic factors were calculated for each pipeline segment. Generally, the selection of line segments recommended for thermomoder- nisation was done on the basis of heat losses and SPBT (simple pay-back time) calculations. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Steam and hot water pipeline networks are widely applied in industrial plants as well as in district heating systems. Chemical and petrochemical plants, factories producing fertilisers, cellulose and textile plants have the most extended and complex pipeline systems. Steam is also used as a basic energy carrier in sugar and generally in food industry as well in heavy industry like non- ferrous and iron metallurgy. These energy carriers are always sent to consumers by piping systems. For practical reasons, overhead pipeline networks are usually built in industrial plants. During the distribution of the aforementioned energy carriers by means of pipelines, there is always a problem of energy losses which result in increasing economic costs. Diverse concepts, methods and algorithms are used for the determination of rational main technical parameters of heat pipe- line network, e.g. diameter of the pipes, thermal insulation thick- nesses and others. Objective functions used for the calculation of optimal values of technical parameters assumed to be decision variables [1e 7] are formulated in various ways. Work [1] presents the procedure for determination of optimal insulation thickness for multi-layer insulation of pipeline. The objective function and the restrictions are nonlinear in most of the insulation problems. A nonlinear optimisation method with con- straints was applied for the minimum cost determination of insu- lated pipelines. The objective function consists of the heat loss and the material costs of the insulating layers and the tube as well. To solve this problem, an algorithm with a penalty function was applied. The sample thicknesses of insulating layers and the mini- mum costs depending on the temperature of the surrounding air and transported substance were determined and presented. More general results of this topic analysis are included in work [2]. While the main objective of applying insulation in any plant is to achieve the minimum total cost during an assumed period (evaluation period), the appropriate insulation thickness is usually called the economic thickness. The general purpose was to find out for what insulation thickness further expenditure on insulation would not be justified by the additional financial savings on heat to be anticipated during the evaluation period. Although an increase in the amount of insulation applied will raise the initial installation cost, but it will reduce the rate of heat loss through the insulation. Therefore it is necessary to reduce the total cost during the evalu- ation period. In work [2], simple-to-use correlations, employing basic algebraic equations which are simpler than other available * Tel.: þ48 32 2372416; fax: þ48 32 2372872. E-mail address: tadeusz.kruczek@polsl.pl. Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy 0360-5442/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.energy.2013.08.019 Energy 62 (2013) 120e131