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The process industry is facing the green transition from conventional to renewable energy sources. Executing it in a cost-effective manner will require increased energy efficiency, electrification, and clear overall strategy from the beginning. A prerequisite to strong strategy is an energy mapping which describes the energy use within an industrial facility, and often very expensive and time consuming. The primary goal of the proposed process mapping methodology is to effectively obtain production and energy data from industrial plants in a short time that can be analyzed to provide a generic, holistic, and flexible model. The model is a step to creating a software tool to generate energy flow mappings for industrial end users to make decisions with energy optimization in mind. In addition to the documentation of energy flows, the tool supports the continuous improvement of the energy mapping itself and the actual energy use. The required data is collected by reviewing existing specifications of production facilities, complemented with interviews with personnel working in the production lines as well as other on-site investigations. The information is then entered into the developed model with energy flow mapping as an output. The model's output can then be used to get an overview of the primary energy used and identify the future opportunities for energy optimization, electrification and decarbonization of industrial sites. A couple of industry use cases have been shown to successfully illustrate the performance of the model.

Electricity and power produced from waste heat is particularly relevant in shipping because fuel expenses constitute the majority of the cost of operating the ships; however, the cost-benefit aspect limits the widespread implementation of waste heat recovery power units on ships. This paper presents the thermodynamic analysis of a concept that aims at reducing the cost of an organic Rankine cycle unit by using one of the cylinders in a large diesel engine as expansion device. Numerical models were used to optimise the process parameters and thereby determine the power potential for this concept. The evaluation of 104 working fluids points to cyclopropane, R245fa and R1234ze(z) as the most promising. The results suggest that the power produced by the organic Rankine cycle cylinder is at least equivalent to that of the cylinders operating with the diesel process. This enables potential fuel savings and emissions reductions of about 8.3% in the studied scenario.

In recent years the interest in small capacity organic Rankine cycle (ORC) power systems for harvesting low qualitywaste thermal energy from industrial processes has been steadily growing. Micro ORC systems are normally equippedwith brazed plate heat exchangers which allows for efficient heat transfer with a compact design. An accurate prediction of the heat transfer process characterizing these devices is required from the design phase to the development of modelbased control strategies. The current literature is lacking experimental data and validated correlations for vaporization of organic fluids at typical working conditions of ORC systems for low temperature waste heat recovery (WHR) applications. Based on these premises, a novel testrig has been recently designed and built at the Technical University of Denmark to simulate the evaporating condition occurring in a small capacity ORC power unit. In this contribution the preliminary experimental results obtained from the first experimental campaign carried out on the rig are reported. HFC-134a was selected as working fluid. The experiments were carried out at saturation temperature of 60, 70 and 80 °C and inlet and outlet qualities ranging between 0.1-0.4 and 0.6-0.95 respectively. The heat flux ranged between 19.4 and 43.1 kWm−2. The results are presented in terms of refrigerant side heat transfer coefficient and pressure drop.The heat transfer coefficient showed significant sensitivity to the saturation temperature and was characterized by a decreasing trend with respect to the mean evaporator quality.The frictional pressure drop showed a linear dependence on the mean quality value and increased as the saturation temperature decreased. The experimental heat transfer coefficients were compared with a well-known correlation for nucleate boiling which significantly underestimated the founded values

Much attention is focused on increasing the energy efficiency to decrease fuel costs and CO2 emissions throughout industrial sectors. The ORC (organic Rankine cycle) is a relatively simple but efficient process that can be used for this purpose by converting low and medium temperature waste heat to power. In this study we propose four linear regression models to predict the maximum obtainable thermal efficiency for simple and recuperated ORCs. A previously derived methodology is able to determine the maximum thermal efficiency among many combinations of fluids and processes, given the boundary conditions of the process. Hundreds of optimised cases with varied design parameters are used as observations in four multiple regression analyses. We analyse the model assumptions, prediction abilities and extrapolations, and compare the results with recent studies in the literature. The models are in agreement with the literature, and they present an opportunity for accurate prediction of the potential of an ORC to convert heat sources with temperatures from 80 to 360 C, without detailed knowledge or need for simulation of the process. © 2013 Elsevier Ltd. All rights reserved

This paper presents developments and new features added to the simulation tool Dynamic Network Analysis. This open-source software is the result of ongoing development at the Department of Mechanical Engineering, Technical University of Denmark since 1988. Ever since, it has been employed to model dynamic and steady-state energy systems and is now available for the most common operating systems (Windows, Mac OS and Linux). Emerging interest in novel plant technologies, high-temperature heat pumps, refrigeration absorption modules, and in energy system optimization has stressed the necessity to extend the capabilities of the software, while at the same time decreasing computational time. Dynamic Network Analysis can now solve non-convex optimization problems by virtue of the fully-embedded genetic algorithm. Moreover, the thermophysical fluid property library has been extended with more than 110 fluids by interfacing CoolProp, a high-accuracy open-source property package for pure and pseudo-pure fluids, as well as humid air. Furthermore, the use as time integrator for other tools is demonstrated. The new features are unveiled in two case studies. The first example covers the optimization of an air bottoming cycle unit recuperating the exhaust heat from an offshore power system. Subsequently, the control of a compressed air energy storage plant is modelled by interfacing with Matlab. Both cases take advantage of CoolProp’s table-based property interpolation scheme

This paper presents the results of an on-going project to develop ThermoCycle, an open Modelica library for the simulation of low-capacity thermodynamic cycles and thermal systems. Special attention is paid to robustness and simulation speed since dynamic simulations are often limited by numerical constraints and failures, either during initialization or during integration. Furthermore, the use of complex equations of state (EOS) to compute thermodynamic properties significantly decreases the simulation speed. In this paper, the approach adopted in the library to overcome these challenges is presented and discussed.

Over the last few decades, researchers have developed a number of empirical and theoretical models for the correlation and prediction of the thermophysical properties of pure fluids and mixtures treated as pseudo-pure fluids. In this paper, a survey of all the state-of-the-art formulations of thermophysical properties is presented. The most-accurate thermodynamic properties are obtained from multiparameter Helmholtz-energy-explicit-type formulations. For the transport properties, a wider range of methods has been employed, including the extended corresponding states method. All of the thermophysical property correlations described here have been implemented into CoolProp, an open-source thermophysical property library. This library is written in C++, with wrappers available for the majority of programming languages and platforms of technical interest. As of publication, 110 pure and pseudo-pure fluids are included in the library, as well as properties of 40 incompressible fluids and humid air. The source code for the CoolProp library is included as an electronic annex.

Power cycles for the efficient use of low temperature heat sources experience increasing attention. This paper describes an alternative cycle design that offers potential advantages in terms of heat source exploitation. A concept for a reciprocating expander is presented that performs both, work extraction and heat addition. Heated by thermal oil, evaporation takes place in two expansion chambers with a transfer of the working fluid at an intermediate pressure level. Using saturated liquid as feed leads to an expansion in the two-phase domain. A dynamic model of this expander is used to determine the state of the working fluid during the process. Based on this model, a first optimisation by means of changed valve timing is conducted and the results of this scenario are shown in this paper. The heat transfer during expansion is investigated and used to establish a representation of the dynamic calculation results for use with a steady state cycle evaluation. An organic Rankine cycle model is developed and used for a comparison. The performance of the expander itself and the different requirements regarding heat source and temperature levels are studied.