This report describes the work of developing a specification of requirements for Waste Heat Recovery Units. The main part of the paper describes how the work with the specification of requirements has been performed. One specific question to be answered is: What are the customer’s demands in case of properties for the Waste Heat Recovery Units and how is that information collected as an order documentation to suit the business area Oil & Gas? The report begins with a description of the assignment and continues with the aim and background. A theoretical part describes the different areas and methods that have been important during the process. Work on the specification has been carried out on site at the company where interviews of staff and the study of internal documents has been a significant part of the implementation. The result is delivered to the company in the form of a specification of requirements for the Waste Heat Recovery Unit. This specification fulfills the requirements set initially and is a good starting point for the company to proceed with in contact with subcontractors. The conclusion of the work is that the establishment of a good specification of requirements is really important and that has been obvious during the work and progress of this project. The difficulty lied in getting the right information and to keep it simple and at same time durable.

A microchannel heat exchanger was designed for diesel waste heat recovery and its performance was evaluated. The 21x15x8 cm unit was constructed from diffusion brazed stainless steel lamina and weighed 11 kg. Operating from a 13.4 kW generator with an exhaust temperature of 500 °C the unit delivered 11.1 kW of thermal energy at the design point with an effectiveness of 0.87. If coupled with an organic Rankine bottoming cycle this has the potential of boosting system power output by 35%. Performance was found to be insensitive to cold side flow conditions. Soot accumulation was found to be problematic, which caused a steady exhaust pressure rise at the device but did not affect the thermal performance. / Graduation date: 2012

The diploma thesis is consisting of theoretic part, which deal with used ventilating systems, ways of waste heat recovery and describe basic types of air-conditioning systems. Following part attend to design of ventilating system and multi-split air-conditioning system for flat. Part of design of ventilation system is calculation of noise levels in rooms. Air-conditioner design is based on calculation of thermal stress. Annual demand of cold and heat demand are calculated using TRANSYS software. Design documentation is part of the diploma thesis.

Rapid growth of digitalization has urged Data Centres (DC) to be more energy efficient by recovering waste heat from server racks that would otherwise be wasted. This techno-economic study is focused on upgrading low temperature waste heat from typical Air-Cooled DC for District Heating Network (DHN) market in Stockholm region. The methodology is carried out by four system configurations that are experimented with different historical electricity data, impacts of climate change with simulated weather data, and variations in DHN temperature as the heat supply scenario development. The results show that DC configuration with combination of both free-cooling and waste heat recovery can foster techno-economic benefits by reducing cooling consumption by 55.6%, compared to DC configuration with free-cooling only; and further lowering Power Usage Effectiveness (PUE) from 1.95 to 1.52. Lifecycle Operational Expenditure (LCO) has also been used as the economic indicator to represent the maximum initial investment that data centre should accept when deciding to recover the waste heat to the DHN. Moreover, the new technical Key Performance Indicators (KPIs) were introduced to support the decision-making in the supply of recovered waste heat to DHN. The electricity price was further identified to have greater impact than the effect of climate change for the overall techno-economic performance. On one specific hand, heat supply with Price-Limit scenario concluded that 40.18% of available waste heat from DC is not profitable should it be injected to DHN in the case of low electricity price. In the case when the electricity price is high, the amount of waste heat not injected to DHN increases to 58.57%. / <p>The thesis defense presentation was held digitally on Zoom on June 19th 2023 at 09.00 CEST</p>

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The focus of this project was on the potential application of waste heat recovery and utilisation (WHR&U) systems in pebble bed modular reactor (PBMR) technology. The background theory provided in the literature survey showed that WHR&U systems have attracted the attention of many researchers over the past two decades, as using waste heat improves the system overall efficiency, notwithstanding the cost of extra plant. PBMR waste heat streams were identified and investigated based on the amount of heat rejected to the environment. WHR&U systems require specially designed heat recovery equipment, and as such the used and/or spent PBMR fuel tanks were considered by the way of example. An appropriately scaled system was designed, built and tested, to demonstrate the functioning of such a cooling system. Two separate and independent cooling lines, using natural circulation flow in a particular form of heat pipes called thermosyphon loops were used to ensure that the fuel tank is cooled when the power conversion unit has to be switched off for maintenance, or if it fails. A theoretical model that simulates the heat transfer process in the as-designed WHR&U system was developed. It is a one-dimensional flow model assuming quasi-static and incompressible liquid and vapour flow. An experimental investigation of the WHR&U system was performed in order to validate the theoretical model results. The experimental results were then used to modify the theoretical heat transfer coefficients so that they simulate the experiments more accurately. Three energy conversion devices, the dual-function absorption cycle (DFAC), the organic Rankine cycle (ORC) and the Stirling engine (SE), were identified as suitable for transforming the recovered heat into a useful form, depending on the source temperatures from 60 ºC to 800 ºC. This project focuses on a free-piston SE with emphasis on the thermo-dynamic performance of a SE heat exchanger. It was found that a heat exchanger with a copper woven wire mesh configuration has a relatively large gas-to-metal and metal-to-liquid heat transfer area. Tube-in-shell heat exchanger configurations were tested, with the working fluid flowing in ten copper inner pipes, while a coolant flows through the shell tube. A lumped parameter model was used to describe the thermo-fluid dynamic behaviour of the SE heat exchanger. In order to validate the theoretical results, a uni-directional flow experimental investigation was performed. The theoretical model was adjusted so that it simulated the SE heat exchanger. It was found that after this correction the theoretical model accurately predicts the experiment. Finally, a dynamic analysis of the SE heat exchanger experimental set-up was undertaken to show that, although vibrating, the heat exchanger setup assembly was indeed acceptable from a vibrational and fatigue point of view. / AFRIKAANSE OPSOMMING: Die hoofoogmerk met hierdie projek was die moontlike aanwending van afvalhitteherwinningen- benutting-(WHR&U-) stelsels in modulêre-gruisbedreaktor-(PBMR-) tegnologie. Agtergrondteorie in die literatuurondersoek toon dat WHR&U-stelsels al menige navorser se belangstelling geprikkel het, hetsy vanweë die moontlike ekonomiese voordele wat dit inhou óf vir besoedelingsvoorkoming, bo-en-behalwe die koste van bykomende toerusting. Die PBMRafvalhittestrome is ondersoek en bepaal op grond van die hoeveelheid hitte wat dit na die omgewing vrystel. Om in die prosesbehoeftes van WHR&U-stelsels te voorsien, moet goed ontwerpte, doelgemaakte hitteherwinningstoerusting in ʼn verkoelings- en/of verhittingsproses gebruik word, dus is die PBMR as voorbeeld gebruik vir die konsep. ʼn Toepaslik geskaleerde WHR&U-stelsel is dus ontwerp, gebou en getoets om die geldigheid van die stelselontwerp te toon. Twee onafhanklike verkoelingslyne, wat van natuurlike konveksie gebruik maak, in die vorm van hitte-pype of termoheuwel lusse, was gebruik om te verseker dat verkoeling verskaf word wanneer die hoof lus breek of instandhouding nodig hê. ʼn Teoretiese model is ontwikkel wat die hitteoordragproses in die ontwerpte WHR&U-stelsel simuleer. Dié model was ʼn eendimensionele vloeimodel wat kwasistatiese en onsamedrukbare vloeistof- en dampvloei in die WHR&U-stelsel-lusse veronderstel. ʼn Eksperimentele ondersoek is op die WHR&U-stelsel uitgevoer ten einde die teoretiese model se resultate te bevestig. Die eksperimentele resultate was dus geneem om die teoretiese hitteoordragkoëffisiënte aan te pas sodat dit die eksperimente kon simuleer. Drie energieomsettingstoestelle, naamlik die dubbel funksie absorpsie siklus (DFAC), die organiese Rankine siklus (ORC) en die Stirling enjin (SE), is as geskikte toestelle uitgewys om die herwonne hitte op grond van brontemperature tussen 60 ºC en 800 ºC in ʼn bruikbare vorm om te sit. Hierdie tesis het op vryesuier-SE’s gekonsentreer, met klem op die hitteruiler. Meer bepaald is die termodinamiese werkverrigting van ʼn SE-hitteruiler ondersoek. Daar is bevind dat ʼn hitteruiler met ʼn geweefde koperdraadmaas-samestelling oor ʼn betreklik groot gas-totmetaal- en metaal-tot-vloeistof-oordragoppervlakte beskik. Die verhitter en verkoeler is in ʼn buis-in-mantel-vorm ontwerp, met die werksvloeistof wat deur tien koperbinnepype vloei en ʼn koelmiddel deur die mantelbuis. ʼn Saamgevoegde-parameter-model is gebruik om die termodinamiese gedrag van die SEhitteruiler te beskryf. Ten einde die teoretiese resultate te bevestig, is ʼn eenrigtingvloeiproefondersoek uitgevoer. Die teoretiese model is aangepas sodat dit die SE-hitteruiler kon simuleer. Ná die nodige verstellings is daar bevind dat die teoretiese model die proefneming akkuraat voorspel. Laastens was ʼn dinamiese ontleding van die SE-hitteruiler ook onderneem om te toon dat, hoewel dit vibreer, die hitteruiler proef samestel inderdaad veilig is.

There has been renewed significance for innovative energy conversion technologies, particularly the heat recovery-to-power technologies for sustainable power generation from renewable energies and waste heat. This is due to the increasing concern over high demand for electricity, energy shortage, global warming and thermal pollution. Among the innovative heat recovery-to- power technologies, the proposed trilateral flash cycle (TFC) is a promising option, which presents a great potential for development. Unlike the Rankine cycles, the TFC starts the working fluid expansion from the saturated liquid condition rather than the saturated, superheated or supercritical vapour phase, bypassing the isothermal boiling phase. The challenges associated with the need to establish system design basis and facilitate system configuration design-supporting analysis from proof-of-concept towards a market-ready TFC technology are significant. Thus, there is a great need for research to improve the understanding of its operation, behaviour and performance. The objective of this study is to develop and establish simulation tools of the TFCs for improving the understanding of their operation, physics of performance metrics and to evaluate novel system configurations for low-grade heat recovery-to-power generation. This study examined modelling and process simulation of the TFC engines in order to evaluate their performance metrics, predictions for guiding system design and parameters estimations. A detailed thermodynamic analysis, performance optimization and parametric analysis of the cycles were conducted, and their optimized performance metrics compared. These were aimed at evaluating the effects of the key parameters on system performances and to improve the understanding of the performance behaviour. Four distinct system configurations of the TFC, comprising the simple TFC, TFC with IHE, reheat TFC and TFC with feed fluid-heating (or regenerative TFC) were examined. Steady-state steady-flow models of the TFC power plants, corresponding to their thermodynamic processes were thermodynamically modelled and implemented using engineering equation solver (ESS). These models were used to determine the optimum synthesis/ design parameters of the cycles and to evaluate their performance metrics, at the subcritical operating conditions and design criteria. Thus, they can be valuable tools in the preliminary prototype system design of the power plants. The results depict that the thermal efficiencies of the simple TFC, TFC with IHE, reheat TFC and regenerative TFC employing n-pentane are 11.85 - 21.97%, 12.32 - 23.91%, 11.86 - 22.07% and 12.01 - 22.9% respectively over the cycle high temperature limit of 393 - 473 K. These suggest that the integration of an IHE, fluid-feed heating and reheating in optimized design of the TFC engine enhanced the heat exchange efficiencies and system performances. The effects of varying the expander inlet pressure at the cycle high temperature and expander isentropic efficiency on performance metrics of the cycles were significant. They have assisted in selecting the optimum-operating limits for the maximum performance metrics. The thermal efficiencies of all the cycles increased as the inlet pressures increased from 2 - 3 MPa and increased as the expander isentropic efficiencies increased from 50 - 100%, while their exergy efficiencies increased. This is due to increased net work outputs that suggest optimal value of pressure ratios between the expander inlets and their outlets. A comprehensive evaluation depicted that the TFC with IHE attained the best performance metrics among the cycles. This is followed by the regenerative TFC whereas the simple TFC and reheat TFC have the lowest at the same subcritical operating conditions. The results presented show that the performance metrics of the cycles depend on the system configuration, and the operating conditions of the cycles, heat source and heat sink. The results also illustrate how system configuration design and sizing might be altered for improved performance and experimental measurements for preliminary prototype development.

There has been renewed significance for innovative energy conversion technologies, particularly the heat recovery-to-power technologies for sustainable power generation from renewable energies and waste heat. This is due to the increasing concern over high demand for electricity, energy shortage, global warming and thermal pollution. Among the innovative heat recovery-to- power technologies, the proposed trilateral flash cycle (TFC) is a promising option, which presents a great potential for development. Unlike the Rankine cycles, the TFC starts the working fluid expansion from the saturated liquid condition rather than the saturated, superheated or supercritical vapour phase, bypassing the isothermal boiling phase. The challenges associated with the need to establish system design basis and facilitate system configuration design-supporting analysis from proof-of-concept towards a market-ready TFC technology are significant. Thus, there is a great need for research to improve the understanding of its operation, behaviour and performance. The objective of this study is to develop and establish simulation tools of the TFCs for improving the understanding of their operation, physics of performance metrics and to evaluate novel system configurations for low-grade heat recovery-to-power generation. This study examined modelling and process simulation of the TFC engines in order to evaluate their performance metrics, predictions for guiding system design and parameters estimations. A detailed thermodynamic analysis, performance optimization and parametric analysis of the cycles were conducted, and their optimized performance metrics compared. These were aimed at evaluating the effects of the key parameters on system performances and to improve the understanding of the performance behaviour. Four distinct system configurations of the TFC, comprising the simple TFC, TFC with IHE, reheat TFC and TFC with feed fluid-heating (or regenerative TFC) were examined. Steady-state steady-flow models of the TFC power plants, corresponding to their thermodynamic processes were thermodynamically modelled and implemented using engineering equation solver (ESS). These models were used to determine the optimum synthesis/ design parameters of the cycles and to evaluate their performance metrics, at the subcritical operating conditions and design criteria. Thus, they can be valuable tools in the preliminary prototype system design of the power plants. The results depict that the thermal efficiencies of the simple TFC, TFC with IHE, reheat TFC and regenerative TFC employing n-pentane are 11.85 - 21.97%, 12.32 - 23.91%, 11.86 - 22.07% and 12.01 - 22.9% respectively over the cycle high temperature limit of 393 - 473 K. These suggest that the integration of an IHE, fluid-feed heating and reheating in optimized design of the TFC engine enhanced the heat exchange efficiencies and system performances. The effects of varying the expander inlet pressure at the cycle high temperature and expander isentropic efficiency on performance metrics of the cycles were significant. They have assisted in selecting the optimum-operating limits for the maximum performance metrics. The thermal efficiencies of all the cycles increased as the inlet pressures increased from 2 - 3 MPa and increased as the expander isentropic efficiencies increased from 50 - 100%, while their exergy efficiencies increased. This is due to increased net work outputs that suggest optimal value of pressure ratios between the expander inlets and their outlets. A comprehensive evaluation depicted that the TFC with IHE attained the best performance metrics among the cycles. This is followed by the regenerative TFC whereas the simple TFC and reheat TFC have the lowest at the same subcritical operating conditions. The results presented show that the performance metrics of the cycles depend on the system configuration, and the operating conditions of the cycles, heat source and heat sink. The results also illustrate how system configuration design and sizing might be altered for improved performance and experimental measurements for preliminary prototype development.

Une grande quantité d’énergie est rejetée par l’industrie à bas niveau de température, en dessous de 200 °C. Afin d’améliorer le rendement énergétique global des procédés utilisés, il est envisageable de valoriser cette chaleur perdue appelée chaleur fatale. Cependant cette valorisation est souvent rendue difficile par la présence d’un décalage temporel entre le moment où l’énergie est rejetée et le moment auquel cette énergie pourrait être de nouveau utilisée. Associant de fortes capacités de stockage ainsi qu’une possible restitution d’énergie à température constante, la solution du stockage de l’énergie thermique par des Matériaux à Changement de Phase, appelés MCP, apparaît comme particulièrement attractive. Cependant, la mise en œuvre de ces systèmes de stockage se heurte à des verrous scientifiques et technologiques tant au niveau du matériau de stockage que du système mais également de son contrôle commande et de son insertion dans les procédés industriels.L’objectif de la thèse est de mettre au point un système de stockage par MCP solide-liquide dans deux gammes de température : 70-85 °C et 120-155 °C. La première correspond aux températures des réseaux de chaleurs ou des chauffages domestiques alors que la deuxième s’applique au préchauffage des procédés industriels déjà existants. La thèse vise à démontrer la faisabilité technique du système de stockage. Le travail s’articule autour de différentes tâches allant de la sélection et la caractérisation des MCP jusqu’à leur mise en œuvre dans un organe de stockage et la simulation numérique de la solution de stockage.Les MCP recensés dans la bibliographie à ces niveaux de températures ont été caractérisés finement par calorimétrie (DSC) afin de déterminer leurs propriétés thermo-physiques sur des échantillons de grade laboratoire. L’acide stéarique pour la gamme 70-85 °C et l’acide sébacique pour la gamme 120-155 °C ont été sélectionnés. Des analyses calorimétriques plus poussées sur le grade industriel de ces matériaux ont été réalisées avec notamment des analyses de vieillissement et de compatibilité avec leur encapsulation respective au sein d’un banc expérimental. Le prototype expérimental de stockage thermique a été dimensionné et conçu pour répondre aux sollicitations simulant les rejets et les demandes d’un procédé industriel. Ce banc d’essais est composé principalement de deux organes de stockage que sont une cuve cylindrique et un échangeur multitubulaire et d’un thermorégulateur servant à simuler le fonctionnement du procédé industriel. Dans l’échangeur multitubulaire, le MCP occupe toute le volume de la calandre tandis que le fluide caloporteur circule dans les tubes. La cuve, quant à elle, contient des capsules sphériques en polyoléfines dans lesquelles le MCP est confiné. Elle est traversée par le fluide caloporteur procédant aux échanges thermiques. Ces capsules sphériques appelées nodules ne peuvent supporter plus de 100 °C et sont exclusivement réservées pour la gamme basse température. Ainsi, l’acide stéarique a été confiné dans les nodules afin de remplir la cuve de stockage. L’acide sébacique a lui été intégré dans la calandre de l’échangeur multitubulaire. Les campagnes expérimentales réalisées ont montré la faisabilité de ces types de stockage. Enfin, un modèle numérique simulant les performances du module de stockage utilisant les MCP encapsulés a été réalisé. Il constitue la première étape d’un outil de simulation complet intégrant les briques technologiques du stockage latent. / A large amount of energy is rejected by the industry at low temperature level, below a temperature of 200 °C. In order to improve the overall energy efficiency of industrial processes, it is possible to re-use this waste heat. However, this energy recovery is often made difficult because of the time difference between the process step at which the energy is lost and the process step at which this energy could be reused. Combining high energy storage capabilities and a possible energy recovery at constant temperature, thermal storage solution by phase change materials (PCM) is particularly attractive. However, this storage systems implementation faces scientific and technologic obstacles concerning both the storage material and system but also its command system and its integration into industrial processes.This thesis aims to develop a thermal energy storage system using a solid-liquid PCM technology in two temperature ranges: 70-85 °C and 120-155 °C. The first one corresponds to temperatures of heating networks or domestic heating systems, while the second one could directly preheat existing industrial processes. The thesis aims to demonstrate the technical feasibility of the storage system. The purpose is divided into different tasks such as PCMs selection and characterization, PCM implementation in a storage system but also numerical simulation of the storage solution.PCM documented in the literature at those temperature ranges were characterized by Differential Scanning Calorimetry (DSC) in order to determine thermo physical properties on laboratory grade samples. Stearic acid for the 70-85 °C temperature range and sebacic acid for the 120-155 °C temperature range were selected. Deeper differential scanning calorimetry analyses were carried out on those industrial grade materials including material ageing process analyses and their compliance with their respective encapsulation within an experimental test bench.Thermal storage experimental prototype was designed in order to meet the demands simulating the rejects and needs of industrial processes. The test bench is mainly composed of two storage systems : a cylindrical tank, a multitubular exchanger and a thermoregulator used to simulate industrial process functioning. The PCM, while in the multitubular exchanger, fills up the whole volume of the shell whereas the heat transfer fluid flows in tubes. The tank, for its part, contains polyolefin spherical capsules in which the PCM is contained. The tank is crossed by the heat transfer fluid conducting heat exchanges. Those spherical capsules called nodules cannot be exposed to temperatures exceeding 100 °C and are exclusively reserved for the low temperatures range. Thus, stearic acid was confined in nodules so as to fill the storage tank. The sebacic acid was incorporated in the multitubular exchanger shell. Experimental campaigns carried out have demonstrated the feasibility of those storage types.

Ce travail de recherche est motivé par les contraintes environnementales qui imposent une réduction des émissions de gaz à effet de serre. L'objectif de cette thèse est d'explorer les possibilités de réduction de consommation des moteurs à combustion interne en les munissant d'un dispositif de récupération de chaleur. Cette étude est focalisée sur la valorisation des rejets thermiques d'installations de faible puissance. Le cycle de Rankine est la technologie qui a été sélectionnée. Une installation d'essais a été construite. Un générateur de gaz chaud simule le moteur thermique ; une part de cette chaleur est collectée par le système de récupération de chaleur et partiellement convertie en énergie mécanique. L'échangeur de chaleur a été conçu et construit en interne ainsi que la machine de détente à piston. Un modèle numérique statique validé expérimentalement pour l'évaporateur a été développé. Celui-ci permet d'explorer les performances du cycle de Rankine sur un large champ de fonctionnement. Avec des hypothèses restrictives le modèle numérique fait apparaître qu'un gain de consommation de l'ordre de 3 % à 4 % sur un tracteur agricole serait possible. Un modèle dynamique de moteur à piston adapté aux cycles de Rankine de faibles puissances a été développé pour aider à son dimensionnement. Ce modèle a permis de mettre au point un concept de machine de détente à piston avec un mécanisme de distribution simplifié. Bien qu'offrant des performances en retrait sur les machines de détente à piston à distribution commandée ce concept est à approfondir pour les systèmes de faible puissance nécessitant une simplicité de construction et un faible coût. / This research was motivated by environmental constraints which impose a reduction in greenhouse gas emissions. The aim of the thesis was to explore the possibility of reducing the consumption of an internal combustion engine using a bottom waste heat recovery system. The study focused on waste heat recovery for low power installations. The Rankine cycle technology was selected to exploit the heat source. An experimental test bench was designed and set up. A hot gas generator simulates an internal combustion engine. Part of the thermal power is absorbed by the evaporator and partially converted into mechanical power. The heat exchanger and piston expander were designed and built in-house. A numerical static model with experimental validation of the evaporator was developed. The model was used to explore the performances of the Rankine cycle over a large operating range. Under restrictive hypotheses, the numerical model showed that is possible to reduce the consumption of a tractor by about 3 to 4 %. A piston expander dynamic model was developed to assist in sizing the expander. The model was used to define a piston expander concept with a simple distribution mechanism. Although a classical distribution mechanism offers better performances, this concept is promising for systems that are simple, small-scale and low-cost.

A l'heure actuelle, l'industrie représente environ le tiers de la consommation énergétique et des émissions de CO2. Des opportunités substantielles existent pour faire face aux enjeux environnementaux et économiques, passant par l'efficacité énergétique en général et l'utilisation de l'énergie, en particulier dans les parcs industriels. Les Systèmes à Energie Distribuée (SED) correspondent en ce sens à une solution courante et prometteuse. Nous avons donc entrepris une démarche d'approche globale de site, incluant l'agrégation de l'ensemble des variables énergétiques, économiques, environnementales et managériales influentes dans une installation de ce type. Une mise en application sur une installation pilote et sa validation ont permis d'identifier les verrous scientifiques et techniques et de mesurer pertinence et efficacité des éléments et modes opératoires des systèmes en mode stationnaire. Cette étude offre une méthode d'utilisation coopérative des indicateurs des domaines impactés et ouvre également des perspectives sur des développements en mode dynamique à des fins d'aide à la conduite optimale. / Nowadays, industry accounts for about one third of energy consumption and CO2 emissions. Substantial opportunities exist to address environmental and economic challenges, including energy efficiency in general and the use of energy, especially in industrial parks. Distributed Energy Systems (DES) correspond in this sense to a common and promising solution. We have therefore undertaken a global site approach, including the aggregation of all influential energy, economic, environmental and managerial variables in an installation of this type. Implementation on a pilot plant and its validation have made it possible to identify the scientific and technical locks and to measure the relevance and efficiency of the elements and stationary operating modes of the systems. This study offers a method of cooperative use of the indicators of impacted domains and also opens perspectives on developments in dynamic mode for the purposes of optimum driving assistance.