Eventos Anais de eventos
CONEM 2022
XI Congresso Nacional de Engenharia Mecânica - CONEM 2022
A methodology to estimate pipe length in heat exchanger networks at the design stage
Submission Author:
Valter Bravim Junior , ES
Co-Authors:
Valter Bravim Junior, Roger Josef Zemp
Presenter: Valter Bravim Junior
doi://10.26678/ABCM.CONEM2022.CON22-0097
Abstract
Heat exchanger networks (HEN) are widely used in industrial processes to reduce energy consumption. HEN synthesis procedures both for initial screening of possible options and for designing the network structure are well known, available in the open literature and in commercial software. Most commonly, utility and heat exchanger costs are the main consideration for HEN design. However, at the process implementation stage, piping and pumping material is needed to transport streams through the equipment as well as the heat exchangers. Piping and pumping costs may influence the HEN topology depending on how equipment is arranged in the process plant layout. Thus, the match-selection stage should be carried out taking these costs into account. This paper presents an improved methodology to estimate the pipe length required for the process streams to exchange heat, which can then be used to estimate piping and pumping costs. In an industrial site, process streams run through one piece of equipment to another, such as tanks, reactors, separators, etc. The heat exchangers of the HEN are located between these pieces of equipment for the streams to achieve their thermal requirements. Existing methods for piping length estimate use the physical coordinates of the equipment that is located at the starting point of the process streams, leading to a rather conservative pipe-length value. We show that by including both the starting point and the endpoint of the process streams, a better estimate can be obtained. These methods only require knowledge of the equipment location and are thus very simple to implement. We then proceed to improve the methodology by considering the entire routes of the process streams and the deviations to reach the desired heat exchanger. This approach, called Shortest Length Method (SLM), results in a linear programming model, albeit slightly more complex to solve than the previous methods, it presents a much better estimate of the actual pipe length required for the network. A case study was used to test the methodologies. For a process with seven process streams and six integrated exchangers, the estimated pipe lengths were 470, 286, and 228 length units for the methods: traditional, improved and SLM, respectively. The proposed methodology enables the attribution of a pipe length value to each potential match prior to the HEN synthesis as well as the estimation of pipe length incurred from the heat exchanges in an already designed HEN.
Keywords
plant layout, heat exchanger network, pipe length, piping
