Regenerative heat exchangers are established as a means of heat recovery in many industrial applications. The fixed-bed regenerators are mostly used to transfer heat from hot flue gas to cold air. In this work, several mathematical models of regenerators and several calculation methods were compared, while the preferred method is Willmott’s open method from 1964. Analysis of the influence of geometrical and operational parameters was carried out for the linear regenerator model.

The aim of the thesis is to design a heat exchanger for heating natural gas in the mining process and subsequent treatment. The first part describes natural gas itself, its origin, mining and ways of treatment. There are described technologies used for finding the deposits itself or processes by which water, sulfur and solid particles are removed from the extracted gas. The next section deals with the types of heat exchangers most commonly used in industry. There are also described basic relations for heat-hydraulic calculation of heat exchanger. In the practical part the heat exchanger itself was designed. World-wide HTRI software was used for the heat-hydraulic calculation and for strength calculation according to the standard ČSN EN 13445 was used sofware Sant´ Ambrogio.

This graduation thesis is concerned with a thermal exchange unit issue whereof one working substance complies with a two-phase mode of a flow. This unit is made for the steam generation. The thesis is supposed to solve operation problems causes of the given unit and to make a proposal of an appropriate solution that is supported by performed calculations. Part of the the work is strength calculation. This work also introduces the thermal-hydraulic processes issue of the steam generation equipment. There are also performed thermal-hydraulic control calculations in consideration of newly set-up operation parameters of the given equipment‘s working substances.

This diploma thesis focuses on strength design of steam condenser. The goal of the thesis is to make strength calculations for the specific operation conditions, introduce possible solutions, provide recommendations and refer to weak points of such calculation procedures. First, thermal-hydraulic design in HTRI software is performed. Strength calculations respect ČSN EN 13445 standard. Strength calculation with imported temperature field is performed in ANSYS Workbench software. In the next step, another strength calculation is realized in Sant´ Ambrogio software. Results are evaluated in conclusion chapter, including recommendations for the possible following work.

This thesis is focused on the thermal-hydraulic and construction design of heat exchanger with floating head. The introductory part is dedicated to the design of heat exchangers. Next part is focused on the thermal-hydraulic design created in HTRI software (module Xist. The next section is the strength calculation of selected components of the heat exchanger according to EN 13445 in software Sant'Ambrogio. The following part describes each of the analysis in software Ansys Workbench. The final part contains complete manufacturing documentation of heat exchanger.

Nowadays, one of the solutions considered in order to face the issue of global warming and to move towards a carbon neutral society relies on the use of solar energy as a renewable and bountiful primary source. And, if photovoltaic technologies account for a large part in the solar energy market, recent years have witnessed the growth of non-concentrated and concentrated solar thermal technologies. Among them, concentrated solar power technology (CSP) which uses the optical concentration of direct solar irradiation to generate high pressure and high temperature steam in the absorber tubes of the plant, has become a promising approach reaching 4.9 GWe of installed capacity by the end of 2015 [1]. However, one of the main challenges faced by CSP technology concerns the variability of solar energy related for example to sunrise, sunset, passing clouds… In addition to that, when it comes to direct steam generation, the presence of a two-phase flow regime inside the absorber tubes leads to a strong dynamic behavior of the steam generation. It is consequently necessary to be able to simulate this dynamic behavior in order to better handle the design and operation of CSP plants. Such simulation tools can then be used for the implementation and the test of reliable control systems aimed at maintaining desired operating conditions in spite of changes in solar irradiation. In this context, the National Institute for Solar Energy (INES), part of the French Alternative Energies and Atomic Energy Commission (CEA) wishes to upgrade their dynamic simulation tool that would enable its teams to reproduce the behavior of a prototype based on the Fresnel solar field technology including direct steam generation which was built and commissioned at Cadarache, Aix-en-Provence. This Master thesis work takes place within this framework and aims at developing a multi-domain dynamic model of the aforementioned prototype. To do so, three models respectively in the thermalhydraulic, the optical and the control-command domains are built and combined using a co-simulation approach relying on an in-house simulation platform called PEGASE. More specifically the development of the following models has been addressed:  a thermal-hydraulic model of the two-phase flow circulating inside the vaporizer field of the prototype and realized with the thermal-hydraulic code CATHARE [2] (Advanced ThermalHydraulic Code for Water Reactor Accidents) applied to solar thermal biphasic issues,  an optical model of the receiver programmed using the Modelica language and the Dymola (Dynamic Modelling Laboratory) simulation software,  control-command models (PID controller, control architecture…) adapted and built upon blocks taken from a modelling library included in the PEGASE platform. Each model was first developed and tested on a standalone basis. These models were then coupled using the PEGASE co-simulation platform. A sunny day was simulated using the multi-domain model and the controllability of the plant was analyzed. At this stage, the study focused on the steam separator level regulation. A thermal-hydraulic study also focused on potential instabilities in the vaporizer that can occur under certain circumstances of water temperature at vaporizer inlet and solar heat flux. This analysis was carried out with a CATHARE standalone model. Perspectives of the present work include a complete validation of the developed models from future experimental data and further developments should aim to extend the modelling scope of the numerical simulator towards a representation of all the hydraulic parts of the CSP prototype. Control schemes and regulation tools would have to be extended as well in order to move towards a more representative control architecture of the prototype. Particularly, the steam quality at vaporizer outlet is an important variable to regulate. Indeed, this parameter is usually kept between 60% and 80% [3]. It must be high enough to limit the power consumption of the recirculation pump but not too high in order to prevent absorber dry-out. / Solenergi, som är en förnybar och riklig primärkälla, är en av de lösningarna som anses kunna lösa problemet med global uppvärmning och bidrar i omvandlingen till ett kolneutralt samhälle. Andelen fotovoltaiska teknologier på energimarknaden är övervägande, men andelen koncentrerad och ickekoncentrerad solterminsteknik har ökat under de senaste åren. Bland solterminsteknikerna är koncentrerad solenergiteknik (CSP), som använder den optiska koncentrationen av direkt strålning för att generera högtrycks- och högtemperaturånga i anläggningens absorberarrör, ett lovande tillvägagångssätt som har nått 4.9 GWe installerad kapacitet i slutet av 2015 [1]. En av de största utmaningarna med CSP-tekniken är solenergins variation vid till exempel soluppgång, solnedgång och passerande moln, vilket beror på varierad tillgång av solljus. Det finns också utmaningar med direkt ånggenerering via tvåfasflödes regimer inuti absorberarrören eftersom det leder till ett starkt dynamiskt beteende vid ånggenereringen. Det är följaktligen nödvändigt att kunna simulera detta dynamiska beteende för att bättre hantera design och drift av CSP-anläggningar. Sådana simuleringsverktyg kan sedan användas för att genomföra tester för att erhålla tillförlitliga styrsystem som upprätthåller önskade driftsförhållanden trots förändringar i solstrålningen I detta sammanhang vill National Institute for Solar Energy (INES), som är en del av den franska alternativa energikommissionen och atomenergi kommissionen (CEA), förbättra dess dynamiskt simuleringsverktyg som skulle möjliggöra för sina team att reproducera beteendet hos en prototyp baserad på Fresnel solfältsteknik inklusive direkt ånggenerering som byggts och beställts vid Cadarache, Aix-enProvence. Denna masteruppsats sker inom ramen för detta och syftar till att utveckla en dynamisk modell med flera domäner av den ovan nämnda prototypen. Tre modeller i termisk-hydraulisk, optisk och kontrollkommando domäner har byggts och kombinerats med hjälp av en co-simuleringsmetod som bygger på en intern simuleringsplattform som heter PEGASE. Mer specifikt om utvecklingen av modellerna enligt nedan:  En termisk-hydraulisk modell av tvåfasflöde som cirkulerar inuti förångarens fält på prototypen har realiserats med termisk-hydraulisk kod CATHARE [2] (Advanced Thermal-Hydraulic Code for Water Reactor Accidents) som appliceras på soltermisk bifasiska frågeställningar.  En optisk modell av mottagaren har programmerats med hjälp av Modelica-språket och simuleringsprogrammet Dymola (Dynamic Modeling Laboratory).  Modeller av kontrollkommandon (PID-kontroller, kontrollarkitektur ...) har byggts och anpassats i moduler som hämtats från modelleringsbibliotek som ingår i PEGASE-plattformen. Varje modell utvecklades och testades på fristående basis. Modellerna kopplades sedan samman i PEGASE-co-simuleringsplattformen. En solig dag simulerades därefter med en flerdomänmodell och styrningsförmågan av anläggningen analyserades. Vid detta stadium fokuserade studien på att reglera nivån av ångseparerande. En termisk-hydraulisk studie fokuserade sedan på potentiella instabiliteter i förångaren som kan uppstå under vissa omständigheter av vatteninloppstemperatur och solvärmeflöde. Denna analys genomfördes med en CATHARE fristående modell. Perspektiven för det aktuella arbetet omfattar en fullständig validering av de utvecklade modellerna med hjälp av framtida experimentella data. Vid en vidareutveckling bör inriktningen vara att utvidga modellernas omfattning av den numeriska simulatorn till att representera alla hydrauliska delar av CSP prototypen. Styrsystem och regleringsverktyg skulle också behöva förbättras för att få en mer representativ kontroll arkitektur av prototypen. I synnerhet är ångkvaliteten vid förångarens utlopp en viktig variabel att reglera. Faktum är att den här parametern vanligtvis hålls mellan 60% och 80% [3]. Det måste vara tillräckligt högt för att begränsa recirkulationspumpens elförbrukning men inte för hög för att förhindra att absorberen torkar ut.