This master’s thesis is focused on the description and processing of the cell method, which is generally recommended for prediction of fluids temperature profiles in heat exchanger. In the thesis the basic equations for calculating heat transfer are presented and is also described the current situation in the field of computational prediction of fluids temperature profiles in heat exchangers. The cell method is solved by using the software Maple and is applied to the specific case of industrial heat exchangers. The results obtained by the cell method are compared with the results obtained by educational version of software HTRI Xchanger Suite. By this comparison explicitness of the cell method is assessed.

The master thesis deals with thermal hydraulic design and strength design of a heat exchanger with “U” tube bundle inside of a shell. The first chapter introduces general design issues of the heat exchangers. The following chapter describes thermal hydraulic design created in software Maple 16.0 by using Kern’s method and the method of Bell-Delaware. HTRI software was used for the control of thermal hydraulic design correctness. To check critical locations of fluid flow in space between the tubes, the CFD model was created at ANSYS Fluent 14.0 software. Accuracy of strength design was verifying by Sant’ Ambrogio software in accordance with ČSN EN 13 445 standards. The last chapter concerns with FEM analysis. According to standards ČSN EN 13 445 the design by analysis namely method based on stress categories were used for the strength analysis of nozzle.

Shell and tube heat exchangers (STHEs) are the most common type of heat exchanger in preheat trains (PHT) of oil refineries and in chemical process plants. Most commercial design software tools for STHE assume uniform distribution over all tubes of a tube bundle. This leads to various challenges in the operation of the affected devices. Flow maldistribution reduces heat duty of STHE in many applications and supports fouling buildup in fluids that tend to particle, bio, and crystallization fouling (Verein Deutscher Ingenieure, ed., 2010, Heat Atlas, 2nd ed., VDI-Buch., Springer-Verlag). In this article, a fluid mechanics study about tube side flow distribution of crude oil and related hydrocarbons in two-pass PHT heat exchangers is described. It is shown that the amount of flow maldistribution varies significantly between the different STHE designs. Therefore, a parameter study was conducted to investigate reasons for maldistribution. For instance, the nozzles diameter, type, and orientation were identified as crucial parameters. In consequence, simple design suggestions for reducing tube side flow maldistribution are proposed.

Concentrating Solar Power (CSP) is one of the most promising renewable energybased electricity generation technologies to deal with the increasing demand of power consumption and environmental sustainability. With the aim of achieving the 2020 SunShot cost target for CSP of 60 USD/MWh, the United States Department of Energy presented, in May 2018, the Gen3 CSP initiative. In particular, the CSP Gen3 Liquid-Phase Pathway proposes to design a CSP system adopting liquid sodium as Heat Transfer Fluid (HTF) in the receiver, advanced high-temperature molten chloride salt as storage fluid and supercritical CO2 (sCO2) Brayton cycle as power cycle. Within this framework, the aim of this master thesis was to design the sodium-chloride salt Heat Exchanger (HX) by developing both a heat exchanger model and a sodiumsalt-sCO2 system model. To pursue these purposes, a completely new Modelica-based HX model was developed and added to the SolarTherm library. Furthermore, as an extension of earlier models, the sodium-salt-sCO2 CSP system (NaSaltsCO2System) was implemented in SolarTherm, by incorporating the HX model and linking it with other new and existing component models. As for the HX, a general model was developed for shell and tube heat exchangers, based on the TEMA guidelines, with the possibility of being customized in terms of media adopted, constraints, boundary conditions, and correlations. The model performs an optimization in order to select the internal geometry configuration that optimizes a user-defined objective-function. By employing the implemented HX model in the NaSaltsCO2System, the sodium-salt heat exchanger was designed aiming at minimizing the Levelized Cost of Electricity (LCOE), providing a complete geometry description, and an estimation of the performances and costs. The resulting NaSaltsCO2System model was found to be robust and able to perform annual simulations that allowed to estimate the energy performances of the CSP plant, as well as the LCOE. Considering the sodium-salt-sCO2 CSP system characterized by a receiver capacity of 543 MWth, 12 hours of Thermal Energy Storage (TES), and a 100 MWe power block, the LCOE resulted equal to 72.66 USD/MWh. The sodium-salt HX design that minimizes the LCOE resulted in a single-shell/single tube pass configuration, with vertical alignment, characterized by an overall height of 15 m, and a shell diameter of 1.8 m. It represents the 3.2% of the total capital cost of the plant. An interesting system-level optimization was then carried out on the combined receiver-heat exchanger block. It regarded the variation of the Log Mean Temperature Difference (LMTD) of the HX and highlighted the possibility to drop the LCOE down to 68.54 USD/MWh. The techno-economic investigations and the sensitivity analysis showed the flexibility and robustness of the HX model, as well as the importance of the NaSaltsCO2System. The latter lays the groundwork to explore potential improvements of this new generation of CSP systems, which can play a fundamental role in the future global energy mix. / Termisk solkraft (CSP) är en av de mest lovande elproduktionsteknologierna baserade på förnybar energi. Den kan bidra till hanteringen av den ökande efterfrågan på energi och miljömässig hållbarhet. I syfte att uppnå 2020 SunShot-kostnadsmålet för CSP på 60 USD/MWh presenterade USA:s energidepartement Gen3 CSPinitiativet. I synnerhet föreslår CSP Gen Liquid-Phase Pathway att utforma ett CSPsystem som använder flytande natrium som värmeöverföringsvätska i mottagaren, smält kloridsalt med hög temperatur som lagringsvätska, samt superkritisk CO2 (sCO2) Brayton-cykel som kraftcykel. Syftet för detta examensarbete var att utforma natriumkloridsaltets primära värmeväxlare genom att utveckla både en värmeväxlarmodell (HX) modell och en natriumsalt-sCO2-systemmodell. För att fullfölja dessa syften utvecklades HX-modellen först, sedan implementerades natriumsalt-sCO2 CSP-systemet NaSaltsCO2System. Båda verktygen utvecklades med hjälp av Modelica som programmeringsspråk. De finns nu tillgängliga i det öppna SolarTherm-biblioteket. När det gäller HX utvecklades en allmän modell för skal- och rörvärmeväxlare med möjligheten att anpassas när det gäller antagna medium, begränsningar, gränsvillkor och korrelationer. Dessutom utförde modellen en optimering för att välja den interna geometri-konfigurationen som optimerar en användardefinierad objektiv-funktion. Genom att använda den implementerade HX-modellen i NaSaltsCO2System designades natriumsalt-värmeväxlaren, vilket gav en fullständig konfiguration-beskrivning och en uppskattning av prestanda och kostnader. Den utvecklade NaSaltsCO2System-modellen visade sig vara robust och kapabel till att utföra simuleringar på årsbasis. Detta gjorde det möjligt att uppskatta CSP-anläggningens energiprestanda samt LCOE. Det utvecklade natriumsalt-sCO2 CSP-systemet som känneteckna des av en mottagarkapacitet på 543 MWth, 12 timmars TES och ett 100 MWe power block, resulterade i en LCOE på 72.66 USD/MWh. Natrium-salt HX-konstruktionen som minimerade LCOE resulterade i en enskalig/enkel rörpassningskonfiguration, med vertikal inriktning, kännetecknad av en total höjd av 15 m och en skaldiameter på 1.8 m. Det motsvarade 3.2% av anläggningens totala kapitalkostnad. Den mest intressanta systemoptimeringen genomfördes på det kombinerade blocket bestående av mottagare och värmeväxlare. Den behandlade variationen av HX:s LMTD och framhöll möjligheten att sänka LCOE till 68.54 USD/MWh. De teknisk-ekonomiska undersökningarna och känslighetsanalysen visade flexibiliteten och robustheten i HX-modellen, liksom vikten av NaSaltsCO2Systemet. Den senare lägger grunden för att utforska potentiella förbättringar av denna nya generation av CSP-system, som kan spela en grundläggande roll i den framtida globala energimixen.

The aim of this diploma thesis is to get acquainted with modern technological elements currently used in shell-and-tube heat exchanger in the shell-side and tube-side, thermal-hydraulic calculation of selected elements and comparison of thermal-hydraulic properties with classically used competing technological elements. The work deals mainly with EM baffle in the tube-side and tube inserts like the twisted tape type (and its modifications) and coiled wire in the tube-side. The theoretical part is focused on acquaintance with classical technological elements in shell-and-tube heat exchanger and with basic thermal-hydraulic calculations, practical part then on acquaintance with modern elements and thermal-hydraulic calculation of selected elements. These calculations are then compared with the results of the thermo-hydraulic calculation of similar elements.