The current study has investigated two-phase refrigerant flow distribution in heat exchange manifolds. Experimental data have been acquired in a heat exchanger test rig specially made for measurement of mass flow rate and gas and liquid distribution in the manifolds of compact heat exchangers. Twelve different manifold designs were used in the experiments, and CO2 and HFC-134a were used as refrigerants.

Frequency and amplitude dependency of velocity distribution and head loss of oscillatory flow in a rectangular duct have been studied experimentally with a model tunnel system. Tests were carried out with the duct of both smooth and rough walls. The smooth wall was made of Plexiglas. Sand roughness was used for the rough wall. Velocity, pressure and differential pressure of stationary flow, pure oscillatory flow and combined oscillatory flow were measured. The combined oscillatory flow was classified as oscillation dominant flow, stationary dominant flow, and oscillation-and-stationary balanced flow. Various oscillating frequencies, amplitudes and steady flow percentages were tested for oscillatory flows. The oscillating frequencies tested were varied from 0.01 Hz to 1.00 Hz. Oscillatory amplitude and stationary part were varied from 10 to 100%. Velocity of the flow was measured with a 2D PIV (Particle Image Velocimetry) and a 2D LDV (Laser Doppler Velocimetry) respectively at different test stages. The maximum mainstream velocity was ranged from 0.05 m/s to 1.1 m/s. Data of pressure variations along the tunnel were collected with differential pressure sensors. Flow rate and instant wall pressures at multiple points along the test tunnel were measured simultaneously. The static pressure in the test tunnel was about 1.0 mWC. The differential pressure along the tunnel was less than 20 mmWC per meter. Examples of velocity distribution in the test rig from LDV measurement are presented, for both stationary flow and oscillatory flow. The dimensionless velocity distributions of stationary flow are in good agreement with the universal velocity distribution law. Deviations are obvious between the velocity distributions of oscillatory flow and the universal velocity distribution law, when the measured velocity is scaled to dimensionless by friction velocity from Clauser chart. Examples of PIV velocities of different flow regimes are presented in the forms of velocity profile and velocity waveform. Generally, the velocity distributions are in good agreement with the results from LDV, in agreement with the normal turbulent velocity distribution in a duct, if the velocity magnitude is not too small. Dimensionless velocity profiles at various phase angles of the same oscillatory flow regime have quite consistent distribution. The annular effect is observed in some cases. Its occurrence depends on the complex actions of oscillating frequency, amplitude and stationary flow percentage. The velocity waveform confirms the characteristics of mass oscillation of the flow. No significant phase shift is displayed between the velocity waveform of the boundary and centreline in most cases tested. The vertical velocity, which is normal to the mainstream, is quite small and has similar features to the mainstream velocity. The velocity profiles got from both LDV and PIV show that the flows in the test tunnel were typical turbulence, with typical velocity distribution of turbulence. No transition between laminar and turbulence is observed even at the turning point of oscillation. Pressure variations measured along the tunnel of different flow regimes are presented. The accelerative heads of oscillatory flow are calculated. The friction head losses along the tunnel are evaluated. The dependencies of pressure variation and friction head loss on oscillatory frequency and amplitude are investigated for both pure oscillatory flow and combined oscillatory flow. It is proven that the friction head loss of oscillatory flow increases along with the increase of frequency if the mean flow rate is kept constant. The peak friction head loss increases along with the increase of oscillatory amplitude. Comparison of pressure variation and friction head loss between stationary flow and oscillatory flow shows that the friction head loss of unsteady flow is much bigger than that of steady flow. This is in good agreement with the expectancy based on the experimental results of laminar flow. The head loss of pure oscillatory flow was greater than that of the stationary flow for dozens or more times for various flow regimes running at equivalent flow rate. The ratio of head loss of combined oscillatory flow to stationary flow running at equivalent flow rate is smaller than that of pure oscillatory flow to stationary flow, several times to dozen times. In general, the frequency dependency of head loss on oscillatory frequency and amplitude is clear, though the measuring length is only 9 metres and the absolute magnitude of pressure variation is less than 0.20 mWC.

Carbon dioxide (CO2, R-744) has been identified as a promising alternative to conventional working fluids in a number of applications due to its favourable environmental and thermophysical properties. Previous work on residential CO2 heat pumps has been dealing with systems for either space heating or hot water heating, and it was therefore considered interesting to carry out a theoretical and experimental study of residential CO2 heat pump systems for combined space heating and hot water heating – so-called integrated CO2 heat pump systems. The scope of this thesis is limited to brine-to-water and water-to-water heat pumps connected to low-temperature hydronic space heating systems..

This thesis focuses on three main areas within the field of SOFC/GT-technology: • Development of a dynamic SOFC/GT model • Model calibration and sensitivity study • Assessment of the dynamic properties of a SOFC/GT power plant The SOFC/GT model developed in this thesis describes a pressurised tubular Siemens Westinghouse-type SOFC, which is integrated in a gas turbine cycle. The process further includes a plate-fin recuperator for stack air preheating, a prereformer, an anode exhaust gas recycling loop for steam/carbon-ratio control, an afterburner and a shell-tube heat exchanger for air preheating. The fuel cell tube, the recuperator and the shell-tube heat exchanger are spatially distributed models. The SOFC model is further thermally integrated with the prereformer. The compressor and turbine models are based on performance maps as a general representation of the characteristics. In addition, a shaft model which incorporates moment of inertia is included to account for gas turbine transients. The SOFC model is calibrated against experimentally obtained data from a single-cell experiment performed on a Siemens Westinghouse tubular SOFC. The agreement between the model and the experimental results is good. The sensitivity study revealed that the degree of prereforming is of great importance with respect to the axial temperature distribution of the fuel cell. Types of malfunctions are discussed prior to the dynamic behaviour study. The dynamic study of the SOFC/GT process is performed by simulating small and large load changes according to three different strategies; • Load change at constant mean fuel cell temperature • Load change at constant turbine inlet temperature • Load change at constant shaft speed Of these three strategies, the constant mean fuel cell temperature strategy appears to be the most rapid load change method. Furthermore, this strategy implies the lowest degree of thermal cycling, the smoothest fuel cell temperature distribution and the lowest current density at part-load. Thus, this strategy represents the overall lowest risk with respect to system malfunctions and degradation. In addition, the constant mean fuel cell temperature strategy facilitates high efficiency part-load operation. The constant turbine inlet temperature strategy proved to lead to unstable operation at low load, and thus it is considered to be the least adequate method for load change. For both the constant mean fuel cell temperature strategy and the constant TIT strategy, surge might be a problem for very large load reductions. The slowest response to load changes was found for the constant shaft speed strategy. Furthermore, this strategy leads to very low fuel cell temperatures at low loads. This in combination with a possible higher degradation rate makes the constant shaft speed strategy unsuited for large load variations. Nevertheless, operation at constant shaft speed may be facilitated by air bypass, VIGV or compressor blow off. / Paper I is published with kind permission of Elsevier, Sciencedirect.com

The main reason for doing this kind ofproject was to find out if it was possible to make a relatively advanced application with user friendly tools. We tested the software MIT App Inventor, and the ability to create a useful application for people who wants to get an overview of their energy intake. During the process we found out that it was possible, but minor setbacks occurred. The main idea of our vision; to make a calculator and a registry with different kinds of food and their amount of calories, was completed quite easily. Later on, design alternatives and more advanced functions were not possible for us to make. This might have been because of the short amount of time the project was given, but also, and more likely, because the software did not contain that kind of advanced functions. Even if there were factors that held creativity back, the basic idea was possible to form.

Värnamo Elnät owns and operates a ripple control system which is used to control loadsespecially when the grid is heavily loaded and for control of street lighting. This report aims atclarifying technical and economic aspects of the ripple control system’s future. The system wasinstalled from 1975 and onwards and its use was greater in those days when the controllableloads where greater then today, the current controllable load level is about 3 MW. The reporthighlights three different aspects of the ripple control system’s future – retain the currentsystem, reinvest in a newer system or discontinue the system.In the report the author also discusses relevant connections to Smart Grids and future meteringsystems and tariffs. The author senses a will from the company to discontinue the system on along term, but also a will to be able to control loads on the grid. Therefore the author suggeststhat the system should remain in operation for another 5 to 10 years, under the condition ofanother investigation of the remaining customer base. / I Värnamo Elnäts infrastruktur finns ett system för rundstyrning installerat. Systemet används iförsta hand för att styra laster på elnätet vid höglast, men även för styrning av gatljus. Det ärframförallt hushåll och företag med direktverkande el eller en större elpanna som har ettrundstyrningsabonnemang och det ger abonnenten en något lägre överföringskostnad per kWh.Eftersom Värnamo Elnät är beroende av ett överliggande nät i form av E.ON:s regionnät däreffekt köps in på spänningsnivån 50 kV är det av intresse att kunna styra laster på elnätet.Rundstyrningen installerades redan 1975 då underlaget av styrbar effekt var väsentligt högre änidag, det beror till stora delar på energieffektiviseringar och byte av uppvärmningssystem ifastigheter.Sedan 2008 är det inte längre möjligt att teckna sig för ett rundstyrningsabonnemang iVärnamo Elnät, och kundunderlaget har minskat med cirka 400 abonnenter de senaste 10 åren– likaså har den styrbara lasten minskat från 6 MW till 3 MW. Rapportens syfte är att klarläggatekniska och ekonomiska aspekter kring rundstyrningssystemets framtid och utreda tre olikascenarion – behålla, reinvestera eller avveckla. I rapporten diskuteras även relevanta kopplingartill Smart Grids och framtida tariffsystem. Det finns en vilja att avveckla systemet på lång sikt,men även en önskan att fortsatt kunna styra last – därför bör ytterligare en studie göras i vilkaexakta effekter som är möjliga att styra idag samt att göra en kundinventering och kartläggavilka som inte uppfyller villkoren för rundstyrning – det vill säga har styrbar last.Författaren anser att rundstyrningssystemet bör behållas i drift i några år till eftersom detmöjliggör styrning av effekt och minskar behovet av inköpt energi – det kan också med fördelanvändas för att styra mot höga elspotpriser vilket skapar en förtjänst både för Värnamo Energiselhandel med också för abonnenterna. Författaren bedömer att driften av systemet kan fortsättaytterligare 5 till 10 år.

Detta arbete har utförts på Skellefteå Kommuns fastighetsavdelning under hösten 2012 och även under början på 2013. Fastighetsavdelningen är ansvariga för bl.a. driften hos Skellefteå Kommuns byggnader och därmed också ansvariga för att minska energianvändningen hos dessa. Till år 2016 har Skellefteå Kommun som mål att åstadkomma en energieffektivisering på 20 % jämfört med utgångsåret 2009. Detta projekt har utförts som en del av detta energieffektiviseringsarbete.  Projektet omfattar två olika mätperioder, under den andra av dessa mätperioder installerades visualiseringsskärmar hos de två berörda objekt som utvalts till detta projekt. På visualiseringsskärmarna visades sedan den momentana energiförbrukningen för att brukarna skulle kunna hålla koll på om förbrukningen ökade eller minskade sett till den senaste veckan. Två informationsträffar, en för varje arbetsplats, hölls också för att informera om projektet samt att ge tips på tänkbara förändringar i arbetsmetoderna som skulle kunna medföra minskad energiförbrukning och därigenom ett positiv resultat. Resultatet av detta projekt blev en mängd mätdata som har sammanställts och analyserats för att slutligen resultera i ett utfall i form av att det ena objektet minskade sin energiförbrukning med 1,7 % och det andra objektet med hela 24,2 %. Slutsatsen har därmed blivit att visualisering samt kommunikation kan vara ett tänkbart alternativ till att åstadkomma en minskad energianvändning och motivera brukare av lokaler att bli engagerade och bidra själva.

The company Olofsfors AB manufactures drive belts for forest machinery, known as ECO-Tracks, and abrasion-resistant steel and cutting edges for graders, excavators and tractors, known as Bruxite and SharqEdges. Manufacturing these products requires the steel to be heated and molded, then submerged in water and hardened. The water used in the hardening of steel is pumped to the process from pits below the floor and then pumped back to the pit after it’s been used. Since the temperature of this water rises after being used to harden the steel the temperature of the pumping pit needs to be adjusted to maintain its setpoint of 21°C. This is done by disposal of hot water from the pit to the river outside while new, cold water, from the river is pumped into the pit. The hot water that is being disposed of contains energy that has not at all been utilized, this has led to the purpose of this report which is to examine the possibility to utilize parts of the energy in the water.   Two possible outlets for the energy at the plant has been selected as especially interesting: • Heating of ventilation supply air in two units with low thermal efficiency and relatively high airflows where the supply air temperature is to be increased from 9 °C to 15 °C. • Fan heaters installed with electric batteries of approximately 200 kW capacity, which heats the premises and serves as an air barrier at the intake ports for metal.   Calculations of power available in one of the factory pump pits during the heating season from October to May and the power required for deposition areas were made. The result obtained is illustrated by means of duration charts from which required and available energy is deduced.   The result of this: Pump pit                             887 MWh / October to May Ventilation                          642 MWh / year Fan heaters                         515 MWh / year   A draft measure has been developed in which two heat pumps delivers hot water for heating of both the ventilation supply air and liquid batteries in air fan heaters. This measure proposal means a cost saving of approximately 390 000 SEK / year where pay-off time of the investment is approximately 5 years. / Olofsfors AB tillverkar bland annat drivband för skogsmaskiner, inom sitt område välkända som ECO-Tracks, samt slitstål och vägstål till bland annat väghyvlar, grävmaskiner och traktorer vilka går under varumärkena Bruxite och SharqEdges. Vid tillverkning av dessa metallprodukter behöver stålet först värmas och formas, för att sedan doppas i vatten och härdas. Vattnet som används vid härdning av stålet pumpas från pumpgropar under golvet, ut till processen för att sedan pumpas tillbaka till pumpgropen efter att ha använts. Eftersom vattnet efter användning i processen har värmts så behöver temperaturen i pumpgropen justeras för att hålla sitt börvärde på 21°C. Detta görs genom att varmt vatten pumpas ut ur pumpgropen samtidigt som kallt vatten från Leduån som rinner utanför fabriken pumpas in i gropen. Det varma vattnet som pumpas ut ur pumpgropen innehåller energi som inte tillvaratas, detta har gett upphov till syftet för detta arbete vilket är att se över möjligheten att tillvarata delar av energin i vattnet.   Två möjliga avsättningsområden för energi på fabriken har valts ut som extra intressanta: Eftervärme av ventilationens tilluft för två aggregat med låg temperaturverkningsgrad samt relativt höga flöden där tillufttemperaturen skall ökas från 9°C till 15°C. Fläktluftvärmare med en total installerad effekt på elbatterier om ca 200 kW som värmer lokaler samt fungerar som luftbarriär vid intagsportar för metall utifrån.   Beräkningar av tillgänglig effekt i en av fabrikens pumpgropar under uppvärmningssäsongen oktober till maj samt effektbehov för möjliga avsättningsområden har genomförts. Resultatet av beräkningarna har åskådliggjorts med hjälp av varaktighetsdiagram. Från varaktighetsdiagrammen kan sedan energibehov och tillgänglig energi utläsas.   Resultatet av detta: Pumpgrop                           887 MWh/oktober-maj Ventilation                          642 MWh/år Fläktluftvärmare                 515 MWh/år   Ett åtgärdsförslag har tagits fram där två värmepumpar levererar varmt vatten för värme av både ventilationens tilluft och vätskebatterier i fläktluftvärmarna. Detta åtgärdsförslag innebär en kostnadsbesparing på ca 390 000 kr/år där pay-off tiden för investeringen är ca 5 år.

This thesis examines different methods for the cooling of data centers. Several means of cooling with the refrigeration cycle have been studied, as well as the feasibility of using free cooling in different parts of Sweden. In addition, the possibilities of transferring excess heat to a nearby district heating system were investigated. It was found that in all investigated cases except two, the data center could be cooled solely with free cooling for at least 300 days a year when only the outside air temperature was considered as a constraining factor. The limit was then set to 20 °C. The vast majority of all district heating systems in Sweden get little to none of their heat from other excess heat sources. It is therefore unlikely that this would hinder the possibility for owners of data centers to sell the heat produced by the servers to district heating systems. The data center belonging to the Swedish Energy Agency was especially examined. Experiments showed that when the cooling system temperature was set to 20 °C or below, the power consumption increased by 1 kW. No upper limit was found. Images taken with an IR-camera indicated that some mixing of hot and cold air takes place near the end of the aisle. Moreover, the difference in temperature between the upper and lower parts of the rack increased when the cooling system was set to higher temperatures, indicating further mixing of air.

This thesis has been written with our society’s current energy-situation in mind. Although it only deals with one particular block of buildings, the solutions and suggestions presented herein are quite applicable on other objects of the same type. This thesis is intended to be used as a guideline for energy-preserving projects in general, with an eye to buildings erected during the Swedish “million-programme” in the sixties and seventies. The paper starts with the acquiring of all necessary blueprints and technical specifications. It then moves on to a thorough description of the buildings in question, and their heating- and ventilation-systems. Followed by this the reader is guided through the successive stages of energy-perseverance measures that are available, and possible. Reasoning around the economic factors concerning all measures is also held. The paper ends with conclusion, and a discussion concerning the delicate issue of the higher return-temperatures possibly reaching the district-heating plant.