Compression resorption heat pumps (CRHP) are a promising option to upgrade waste heat from industry. One way to optimize a CRHP is by minimizing the entropy production rate of the heat pump; that is to minimize the lost work of the system. In this paper a CRHP operating with an ammonia-water mixture is analysed based on an application case from the chemical industry. First, a global approach is used to analyse the entropy production rate of each of the components in the heat pump cycle. Based on the result from the global approach the component with the maximum energy dissipation in the heat pump is identified, in this case the resorber. The resorber is therefore further analysed with a detailed thermodynamic state model and entropy production is calculated using the theory of non-equilibrium thermodynamics. Measures to reduce the non-uniformity of the entropy production are then proposed based on the theory of equipartition. @en

This paper discusses a case study in which the waste heat from a refinery is used to heat up district heating water for a local district heating (DH) network. The potential of using heat pumps in order to recover heat from low temperature process water streams for DH is to be analyzed. The heat pump will have to extract heat from a source at 37°C and add it to the DH water to increase its temperature as much as possible with reasonable values of the coefficient of performance (COP). The process water is presently cooled down using cooling towers. Extracting heat from the process water serves two purposes – waste heat recovery for DH and reduction in the load sent to the
cooling towers.@en

Upgrading waste heat by compression resorption heat pumps (CRHP) has the potential to make a strong impact in industry. The efficiency of CRHP can be further improved by using alternative working fluids. In this work, the addition of carbon dioxide to aqueous ammonia solutions for application in CRHP is investigated. The previously published thermodynamic models for the ternary mixture are evaluated by comparing their results with experimental thermodynamic data, and checking their advantages and disadvantages. Then the models are used to investigate the impact of adding CO₂ to NH₃-H₂O in wet compression resorption heat pump applications. For an application where a waste stream is heated from 60 to 105 °C, a COP increase of up to 5% can be attained by adding CO₂ to the ammonia-water mixture, without any risk of salt formation. Additional advantages of adding CO₂ to the ammonia-water mixture in that case are decreased pressure ratio, as well as an increase in the lower pressure level. When practical pressure restrictions are considered the benefits of the added CO₂ become even larger or around 25% increase in the COP. Nonetheless, when the waste stream was considered to be additionally cooled down, no significant benefits were observed.

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As the chemical process industry is among the most energy demanding sectors, chemical engineers are endeavoring to contribute towards sustainable future. Due to the limitation of fossil fuels, the need for energy independence, as well as the environmental problem of the greenhouse gas effect, there is a large increasing interest in the research and development of chemical processes that require less capital investment and reduced operating costs and lead to high eco-efficiency. The use of heat pumps is a hot topic due to many advantages, such as low energy requirements as well as an increasing number of industrial applications. Therefore, in the current book, authors are focusing on use of heat pumps in the chemical industry, providing an overview of heat pump technology as applied in the chemical process industry, covering both theoretical and practical aspects: working principle, applied thermodynamics, theoretical background, numerical examples and case studies, as well as practical applications. The worked-out examples have been included to instruct students, engineers and process designers about how to design various heat pumps used in the industry. Reader friendly resources namely relevant equations, diagrams, figures and references that reflect the current and upcoming heat pump technologies, will be of great help to all readers from the chemical and petrochemical industry, biorefineries and other related areas.@en