An experimental activity was performed to observe and study the effects of graphite dispersion and deposition on thermal hydraulic phenomena in a Reactor Cavity Cooling System (RCCS). The small scale RCCS experimental facility (16.5cm x 16.5cm x 30.4cm) used for this activity represents half of the reactor cavity with an electrically heated vessel. Water flowing through five vertical pipes removes the heat produced in the vessel and releases it in the environment by mixing with cold water in a large tank. PIV technique was used to study the velocity field of the air inside the cavity. A set of 52 thermocouples was installed in the facility to monitor the temperature profiles of the vessel and pipes walls and air. 10g of a fine graphite powder (particle size average 2 [mu]m) were injected into the cavity through a spraying nozzle placed at the bottom of the vessel. Temperatures and air velocity field were recorded and compared with the measurements obtained before the graphite dispersion, showing a decrease of the temperature surfaces which was related to an increase in their emissivity. The results contribute to the understanding of the RCCS capability in case of an accident scenario.

In this thesis, solar energy is utilized as the driving energy for an absorption cooling system, and a TRNSYS computer code is employed to simulate the operation of the system under Taiwan climate. Climate data in TMY2 form for several major cities of Taiwan are input to the simulation program. Also system operating parameters of solar collector area and the size of the system storage are varied to study there effects on the system performance. This research provides computer simulation data for the monthly solar fraction (f) as well as the seasonal solar fraction (F) for the absorption solar cooling system operated under the climate of the major cities in Taiwan. The data can provide the design needs.

De flesta industrier har någon typ av kylsystem som betjänar industriella processer och komfortkyla. Funktion och effektivitet på systemen varierar och när kylproblematik uppstår på anläggningen kan anledningarna vara flera. Kylproblematiken kan bero på bristande kylkapacitet, felaktigt injusterade köldbärarflöden eller underdimensionering av distributionssystem samt cirkulationspump. Detta examensarbete har utförts i samarbete med Stora Enso Skoghall och syftet med studien är att kartlägga och analysera deras kylsystems kapacitet, både sett till producerad kyleffekt och möjligheter till distribution på anläggningen. Genom en ökad kännedom av systemets funktion kan optimeringsförslag arbetas fram för att minska risken för kylproblematik och kostsam produktionsbegränsning. Då distributionssystemet är äldre och påbyggt i etapper finns misstankar om att det även finns möjligheter att med modern teknik få systemet att bli mer energieffektivt. Att effektivisera system gör att resurser kan sparas in vilket är ett viktigt steg mot en hållbar utveckling. För att få en överblick över systemets funktion och problematik har kyleffektsbehovet som ska betjänas kartlagts och jämförts med produktionskapacitet. Flödesmätningar har utförts på systemet för att kartlägga hur flödesbilden ser ut och jämföra verkliga flöden med de projekterade värdena för att avgöra hur väl injusterat systemet är. Undersökningen visade att det i dagsläget finns tillräckligt med kylproduktionskapacitet men att det förekommer relativt stora skillnader mellan projekterade och verkliga flöden. Det framkom också att cirkulationspumparna i dagsläget inte klarar av att leverera tillräckligt stort totalflöde för att tillfredsställa dimensionerande behov. För att undersöka hur en injustering kommer att påverka tryckfallen i systemet och för att avgöra hur pumparnas dimensionering skulle se ut vid drift av ett injusterat system har en beräkningsmodell över tryckfallen i systemet byggts upp med grund i mätdata från anläggning. För att lösa problematiken bör systemet injusteras. Genom att injustera systemet säkerställs att korrekta flöden betjänar respektive behov. Pumparna bör köras för att kunna tillgodose totalflödet vid dimensionerande fall, detta kan lösas med parallellkörning samt ökat varvtal på pumparna. Utredningen har dock visat att det finns en besparingspotential som motiverar att pumparna bör varvtalsregleras mot en proportionell tryckhållning för att minska att onödigt stora köldbärarflöden pumpas runt, vilket leder till onödigt höga driftkostnader för systemet. Studien har visat att det finns möjligheter till en rad åtgärder som skulle kunna minska elförbrukningen till pumparna under vissa perioder med upp till 75 %. / Most industries have some type of cooling system serves the industrial process and comfort cooling. Operation and efficiency of the systems varies and when cooling problem occurs, it can depend on several reasons. Cooling problems may be due to a lack of cooling capacity, improperly aligned water flow or under-sizing of the distribution system and circulation pump. This thesis has been carried out in cooperation with Stora Enso Skoghall and the purpose of the study is to investigate and analyze their cooling system properties, both in terms of produced cooling capacity and the opportunities for distribution on the facility. Through increased knowledge of system operation, proposals for optimization can be worked out to reduce the risk of cooling problems and costly production limitation. Because the distribution system is old, there are opportunities to use modern technology to get the system more energy efficient. When making the system more efficient it allows resources to be saved and this is an important step towards sustainable development. To get an overview of the problems in the system has the cooling effect been mapped and compared with the maximal production capacity. Flow measurements have been performed on the system to chart how the flows looks and the actual flow has been compared with the projected values to determine how well balanced the system is. In the current situation has the investigation showed that the system has enough production of cooling effect. But that there are relatively large differences between projected and actual flows. It also emerged that in the current situation the circulation pumps are not capable to supplying sufficient total flow to satisfy the designed requirements. To calculate how the adjustment will affect the pressure drops in the system and determine how the pumps design would look at the operation of a balanced system has a calculation-model of pressure drops in the system been built up with the data from the facility. To solve the problem, the system should be balanced so that the correct flow serving the respective needs. The pumps should be run so the overall flow is big enough to serve the total design flow. This can be solved by parallel operation and increased speed of the pumps. The investigation has shown that if the pumps would be speed-controlled against a proportional pressure limit, it can reduce the costs of pump energy and that leads to a potential for saving money. The study has shown that there are opportunities for a range of proceed that could reduce the electricity consumption of the pump at certain periods of up to 75%.

Programa computacional em Matlab-Simulink para simular o comportamento do sistema de arrefecimento de veículos comerciais (vans, ônibus e caminhões) equipados com motores diesel. O programa está embasado em uma modelagem matemática que visa caracterizar o funcionamento dos componentes principais do sistema: motor, radiador, termostato, by-pass e bomba d\'água. Tendo como entrada dados característicos do veículo em estudo, o programa computacional fornece a distribuição de temperatura ao longo do tempo para o líquido de arrefecimento - parâmetro preponderante em uma análise do sistema. Os resultados da simulação permitem aos projetistas prever a atuação do sistema de arrefecimento em diversas condições, o que possibilita a realização de um número menor de testes de pista. Os benefícios de um sistema de arrefecimento projetado adequadamente podem ser notados em relação à economia de combustível, ao aumento de desempenho e à redução do desgaste de determinadas peças do motor e da emissão de poluentes. / A software was developed having Matlab-Simulink as basis and it simulates the behavior of the cooling system in commercial vehicles (vans, bus and trucks) equipped with diesel engines. The program is based on mathematical models to describe the main components of the system: engine, radiator, thermostat, by-pass and water pump. Having as input data the features of the vehicle in studied, the software supplies the cooling fluid temperature distribution during certain time - preponderant parameter in the analysis of the system. The results of the simulation allow the designers to foresee the cooling system performance in several conditions, decreasing the number of track tests. The benefits of an adequate designed cooling system project can be noticed considering fuel economy, performance improvement and decrease of wearing of specific parts in the engine as well as pollutant emissions.

A combustion engine generates a lot of heat which need to be cooled to prevent damages to the engine and the surrounding parts. If the cooling system can not provide enough cooling to keep the engine in a well defined range of temperatures performance and durability will decrease and emissions increase. It is also important that the cooling system do not over-cool the engine, since this may result in rough running, increased engine friction and an overall negative performance. The aim of this thesis work is to create a complete 3D digital model of the cooling system for the first generation VED4 HP with CFD in STAR-CCM+. The simulated results are compared to available experimental data for validation. Today the entire system is being modeled with 1D CFD. One of the selected components in the cooling system being model in 3D at Volvo Cars is the water jacket. The 3D CFD model depends on the 1D CFD model for the boundary conditions which is an ineffective and time consuming process, sending data back and forth between the models when making changes. A 3D CFD model is not only more accurate than the 1D CFD model, since it capture the 3D flow phenomenas but it also allows parts or areas to be studied in detail. A study of four different turbulence models is conducted on the water jacket and on an arbitrary pipe in the cooling system. A mesh study is carried on the water jacket, the same arbitrary pipe and on the thermostat, both for the opened and closed thermostat. These studies are done with regard to pressure drop only. The study yields a low Reynolds model with the k-ε v2f turbulence model gave the best results. There is a discrepancy between the simulated results and the experiments. Main reasons to this may be the difference in the geometry used in this thesis for the digital model and the geometry used for the experiments together with the inaccuracies in the experimental data. The overall deviation is larger for a case with closed thermostat than for a case with an open thermostat. With the correct geometry and more accurate experimental data the simulations should be a close representation of reality.

This report is the result of a master’s thesis project which covers the cooling system in Volvo Cars’ fuel cell test vehicle. The purpose is to investigate if the existing cooling system in the fuel cell test vehicle works with the current fuel cell system of the vehicle, in terms of sufficient heat rejection and thus sustaining acceptable temperature levels for the fuel cell system. The project also aims to investigate if it is possible to implement a more powerful fuel cell system in the vehicle and keep the existing cooling system, with only a few necessary modifications. If improvements in the cooling system are needed, the goal is to suggest improvements on how a suitable cooling system can be accomplished. This was carried out by modeling the cooling system in the simulation software GT-Suite. Then both steady state and transient simulations were performed. It was found that the cooling system is capable of providing sufficient heat rejection for the current fuel cell system, even at demanding driving conditions up to ambient temperatures of at least 45°C. Further, for the more powerful fuel cell system the cooling system can only sustain sufficient heat rejection for less demanding driving conditions, hence it was concluded that improvements were needed. The following improvements are suggested: Increase air mass flow rate through the radiator, increase pump performance and remove the heat exchanger in the cooling system. If these improvements were combined it was found that the cooling system could sustain sufficient heat rejection, for the more powerful fuel cell system, up to the ambient temperature of 32°C.

In this report, which is written for Halmstad University and on behalf of Semcon, a mechanical design process was implemented to evaluate the possibility of executing a low-cost cooling system for one of the battery company’s products. The report started from the background of former studies to clarify the problem and finding existing solutions in the first step and following up with developing concepts based on gathered information from the literature study. The battery company provides a high-performance battery based on customer requirements because of the flexible lithium battery technology. There are two similar conditions in the operating period of the battery. One in the high performance usage of the battery and two in the charging period by adding power to the battery cells. Both of these actions generate heat which is the result of resistance of the material in the cells and the chemical reaction of the cells. The battery company wants to decrease the time of charging period in order to reach the operative condition as fast as possible by enabling fast charging. According to the battery management system (BMS), at high temperatures the efficiency of charging rate decreases and also it has a negative influence on the battery cells performance and lifetime. A cooling system is required in order to fulfil the requirement of having high performance and making fast charging possible for the battery. The goal of this thesis is to develop a cooling system based on literature study with consideration of applying to the lithium battery in order to reduce charging time by decreasing temperature in the modules during the operating period. This report contains the whole developing conceptual design process of the cooling system by starting a wide range of information gathering in the purpose of determining the main variables which have an influence on different cooling techniques. In specific, after deciding about the type of cooling method for the product, the study has been focused on the fluid dynamics and heat transfer by forced convection with airflow. The concept generation executed on the information which was gathered through the information retrieval. The final developed concept has been introduced in this thesis work which has the potential of fulfilling the requirement of designing a cooling system to decrease the temperature of the battery’s modules without making any serious changes in the product. The final concept has been developed by various changes in its components and evaluating those changes by executing simulation for each change. The final concept contains twelve similar heat sinks which have been installed over connectors to provide more surface in the purpose of exchanging heat through the airflow provided by three high-speed fans. In order to force the airflow over the heat sinks, a cover has been designed.

No description available.

Solar Energy and Hydrogen (energy carrier) are possible replacement options for fossil fuel and its associated problems of availability and high prices which are devastating small, developing, oil-importing economies. But a major drawback to the full implementation of solar energy, in particular photovoltaic (PV), is the lowering of conversion efficiency of PV cells due to elevated cell temperatures while in operation. Also, hydrogen as an energy carrier must be produced in gaseous or liquid form before it can be used as fuel; but its‟ present major conversion process produces an abundance of carbon dioxide which is harming the environment through global warming. In search of resolutions to these issues, this research investigated the application of Thermal Management to Photovoltaic (PV) modules in an attempt to reverse the effects of elevated cell temperature. The investigation also examined the effects of coupling the thermally managed PV modules to a proton exchange membrane (PEM) Hydrogen Generator for the production of hydrogen gas in an environmentally friendly and renewable way. The research took place in Kingston, Jamaica. The thermal management involved the application of two cooling systems which are Gravity-Fed Cooling (GFC) and Solar-Powered Adsorption Cooling (SPAC) systems. In both systems Mathematical Models were developed as predictive tools for critical aspects of the systems. The models were validated by the results of experiments. The results of the investigation showed that both cooling systems stopped the cells temperatures from rising, reversed the negative effects on conversion efficiency, and increased the power output of the module by as much as 39%. The results also showed that the thermally managed PV module when coupled to the hydrogen generator impacted positively with an appreciably increase of up to 32% in hydrogen gas production. The results of this work can be applied to the equatorial belt but also to other regions with suitable solar irradiation. The research has contributed to the wider community by the development of practical, environmentally friendly, cost effective Thermal Management Systems that guarantee improvement in photovoltaic power output, by introducing a novel way to use renewable energy that has potential to be used by individual household and/or as cottage industry, and by the development of Mathematical Tools to aid in photovoltaic power systems designs.

The automotive industry is currently traversing through the electrification wave. Numerous manufacturers are directing focus to electrify their lineup and reduce emissions. In the frontier of heavy duty diesel trucks, electrification of auxiliary units remains an unexplored potential. An optimized cooling system functioning in sync with a controllable electric coolant pump attempts to reduce parasitic losses and emissions. The cooling flow requirements in challenging conditions may also be fulfilled. Although electric coolant pumps are found increasingly in passenger cars, the implication of independently operating them in a heavy duty diesel truck is an important objective to be explored. The purpose of this project is to generate different cooling system layouts coupled with electrical coolant pumps. The performance of these layouts is compared with the volume flows in a standard cooling system. Refined layouts which fulfill the cooling system requirements are chosen for verification. 1-D Simulation is used to correlate and verify the trends of the test rig data. The results show an adequate gain in the total volume flow across distinct layouts with the electric coolant pumps. However, numerous challenges are required to be overcome. / Bilindustrin befinner sig mitt i en våg av elektrifiering. Flertalet tillverkare fokuserar på att elektrifiera sitt produktutbud och att minska utsläppen. Inom forskningen kring tunga transporter med dieseldrivna lastbilar, är elektrifiering av kylsystemet ett outforskat område. Ett optimerat kylsystem som är reglerbart med en elektrisk kylvätskepump skulle potentiellt kunna minska energiförluster och utsläpp. Kravet på flödet av kylvätska vid utmanande driftsfall skulle också kunna bli bättre uppfyllda än för dagens system. Trots att det blir allt vanligare att personbilar har elektriska kylvätskepumpar, så har det inte utforskats vad det innebär att ha reglerbara elektriska kylvätskepumpar i dieseldriva lastbilar. Därför är detta ett viktigt område att utforska. Målet med detta projekt är att skapa olika kylsystemskoncept, där den elektriska kylvätskepumpen är en systemkomponent. Prestandan hos dessa principlösningar jämförs sedan med volymflödet i ett standard kylvätskesystem. Koncept som uppfyller kraven för kylvätskesystemet kommer att bli utvalda för vidare verifiering. 1-D simuleringar används för att hitta samband och verifiera mot trenderna som hittas i resultat från en testrigg. Resultaten visar en förbättring i det totala volymflödet för flera av lösningarna, som har en elektrisk kylvätskepump. Men det finns fortfarande flera utmaningar som behöver övervinnas.