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M.Tech. (Metallurgical Engineering) / Please refer to full text to view abstract

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Film cooling is investigated on a flat plate both numerically and experimentally. Conical shaped film hole are investigated extensively and contribute to the current literature data, which is extremely rare in the open public domain. Both configuration of the cylindrical film holes, with and without a trench, are investigated in detail. Design of experiment technique was performed to find an optimum combination of both geometrical and fluid parameters to achieve the best film cooling performance. From this part of the study, it shows that film cooling performance can be enhanced up to 250% with the trenched film cooling versus non-trenched case provided the same amount of coolant. Since most of the relevant open literature is about film cooling on flat plate endwall cascade with linear extrusion airfoil, the purpose of the second part of this study is to examine the interaction of the secondary flow inside a 3D cascade and the injected film cooling jets. This is employed on the first stage of the aircraft gas turbine engine to protect the curvilinear (annular) endwall platform. The current study investigates the interaction between injected film jets and the secondary flow both experimentally and numerically at high Mach number (M=0.7). Validation shows good agreement between obtained data with the open literature. In general, it can be concluded that with an appropriate film coolant to mainstream blowing ratio, one can not only achieve the best film cooling effectiveness (FCE or η) on the downstream endwall but also maintain almost the same aerodynamic loss as in the un-cooled baseline case. Film performance acts nonlinearly with respect to blowing ratios as with film iv cooling on flat plate, in the other hand, with a right blowing ratio, film cooling performance is not affect much by secondary flow. In turn, film cooling jets do not increase pressure loss at the downstream wake area of the blades.

An absorption principal cooling system, currently proposed for installation and evaluation at the Florida Solar Energy Center (FSEC), is described as a system and modeled through use of "A Transient Simulation Program (TRNSYS)" developed by the University of Wisconsin. The system model included the FSEC building with its heat gains and losses due to insolation and conduction. System element and cooling load parameters are estimated and the basis of estimation is included to help identify adjustments required to fit the model to the final system installation as new or more complete data becomes available. Deficiencies noted in the current TRNSYS system are identified as potential improvement areas. An empirical model of the 25-Tom Arkla Absorption Water Chiller proposed for the FSEC system is developed front he factory performance test data and implemented through use of TRNSYS algebraic function modules. A simplified block diagram of the FSEC cooling system is described and the basic TRNSYS modules required to model the system are also indicated in block diagram form. The individual modules with parameter designations and values, input designations and initial values, and output designations are each included. Finally, the model listing and simulation output data for a seven day period, utilizing actual solar insolation and ambient temperature data, are provided to demonstrate the model and reasonableness of results. Validation of the baseline model requires careful insertion of actual system parameters, after final system installation, and comparison of system test results against model results obtained using the test period insolation and temperature data.

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Given the coinciding growth-trend in the production of consumer electronics and generation of data, the increase in server halls and data centers, as a means for hosting storage capacity for the generated data, has been prominent over the last decades. The establishment of data centers in already existing infrastructure can entail major changes in terms of energy system design. The activity of data processing and storage is power intensive and as the centers demonstrate substantial heat generation, one of the most important fractions of the energy use comes from the need to provide cooling. The study is a techno-economic analysis purposed for determining the feasibility of different cooling systems for a data center in Sweden. The investigated building currently hosts an industrial printing press hall in which paper printing has been conducted for the several decades. This press hall is subject to a refurbishment process to eventually be converted into a data center. In order to achieve the objectives, a data center building model is developed, designated for the estimation of the internal heat generation and demand for cooling. The design and energy requirements of a number of cooling solutions are then investigated and evaluated using a number of performance metrics: Power Usage Effectiveness (PUE), Capital Expenditure (CapEx), Operational Expenditure (OpEx) and Life Cycle Cost (LCC). More specifically the systems incorporate technologies for utilizing air-based free cooling, ground-source free cooling through borehole ground source heat exchangers (GHEs), mechanical cooling through compressor-driven machines as well as District Cooling (DC). The results of the study show that free cooling is a viable solution for covering the vast majority of the yearly cooling requirements, during sufficiently low outdoor temperatures. Free cooling, provided through borehole GHE’s, is feasible as a partial solution from a technical point of view, to provide cooling capacity during warmer periods. However, it can not alone act to provide a major part of the relatively high and constant cooling capacity requirements throughout the year. All of the investigated scenarios display a similar energy performance in terms of total PUE, at values well below the national average of 1.37. It is also seen, that the scenario that displays the lowest LCC includes a combination of free cooling and compressor-driven cooling. This holds for the studied sensitivity cases. It is found that a combined system incorporating borehole GHE’s and compressor cooling machines perform the best in terms of a low PUE. However, the relative difference in energy performance turns out to be lesser than the relative difference in LCC, when substituting the borehole GHE’s for additional cooling machine capacity. / I takt med digitaliseringen och en ökad global användningen- och produktionen av hemelektronik, vilket föranlett en ökad generering av data, har antalet datahallar blivit allt fler de senaste decennierna. Datahallens syfte är att hantera och bereda lagringskapacitet för den data som genereras vilket involverar en rad energikrävande processer. Upprättandet av datahallar i redan befintlig infrastruktur kan medföra förändringar när det kommer till utformningen av byggnadens energisystem. Att bedriva datalagring och informationsbehandling kräver påtagliga mängder elektricitet vilket medför stor intern värmealstring och därtill behov av aktiv kylning.  Denna studie, som valt att benämnas som en tekno-ekonomisk fallstudie, undersöker lämpligheten i implementeringen av olika kylsystem för ett byggnadskomplex i Stockholm. I byggnadens lokaler återfinns idag en industrihall där det sedan flera decennier bedrivits tryckeriverksamhet. Industrihallen är föremål för en konverteringsprocess för att på sikt bli en datahall. Studien är centrerad kring denna konverteringsprocess. För att utvärdera kylbehoven för den framtida datahallen har en modell utvecklats som uppskattar interna värmelaster samt reglerar inomhusklimatet efter rådande krav på inomhuskomfort. Därefter studeras utformning och energibehov för flera olika typer av kylsystemlösningar där en utvärdering av dessa system görs utifrån indikatorerna Power Usage Effectiveness (PUE), Capital Expenditure (CapEx),Operational Expenditure (OpEx) and Life Cycle Cost (LCC). Mer konkret undersöks kombinerade kylsystem som utnyttjar luftburen frikyla, geotermisk frikyla via bergvärmeväxlare (GHEs), mekanisk kyla via kompressordriven kylmaskin samt regional fjärrkyla. Resultaten från studien visar att frikyla från kylmedelskylare är en lämplig lösning för att täcka majoriteten av datahallens kylbehov över ett år, med undantag för årets varmare perioder. Geotermisk frikyla via borrhål är möjlig som partiell lösning ur ett tekniskt perspektiv, men kan inte enskild leverera en majoritet av effekt- eller energibehovet av kyla. Resultatet visar också att alla undersökta scenarier uppvisar en liknande energiprestanda i termer av total PUE, med värden som underskrider det nationella genomsnittet 1,37. Lägst LCC påvisades för ett system som kombinerar luftburen frikyla via kylmedleskylare och mekanisk kyla via kompressordrivna kylmaskiner. Denna låga LCC är signifikant vilket påvisas i utförd känslighetsanalys. Slutligen konstateras att ett system innefattande luftburen och geotermisk frikyla i kombination med kompressordrivna kylmaskiner resulterar i lägst PUE bland de undersökta scenarierna. Den relativa skillnaden i energiprestanda visar sig vara mindre än den relativa skillnaden i LCC, när geotermisk frikyla ersätts med ytterligare kapacitet från kylmaskiner.

Det här arbetets syfte är att ge förslag på ny kyllösning i en kommersiell fastighet. Den nuvarande lösningen innebär att kylan kommer ifrån tappkallvatten som spolas in i en värmeväxlare, den här lösningen är både dyr och har en negativ påverkan på vår miljö, fastighetsägaren är inte nöjd med detta och vill göra om systemet. Då det inte finns några direkta mätvärden från systemet förutom vattenförbrukningen så är effekt-och energibehovet en osäkerhet. Två driftfall har tagits fram där driftfall 1 och driftfall 2 har ett effektbehov på 80 kW respektive 130 kW. Utifrån driftfallen har effekt- och energiprofil tagits fram. Med hjälp av profilerna har en ny lösning tagits fram men med fyra olika metoder. Undersökningen tar upp lösningar med fjärrkyla, bergkyla, absorptionskyla och kompressorkyla. Fjärrkylan är idag inte ett möjligt alternativ då det fortfarande inte finns ett fjärrkylanät men diskussionerna pågår om ett sådant nät och på grund av detta är fjärrkyla med som en möjlig framtida lösning. Undersökningen visar att fjärrkyla inte är ett lönsamt alternativ, detta eftersom man behöver behålla nuvarande lösning fram till dess. Absorptionskyla är inte heller ett bra alternativ och det beror på det höga fjärrvärmepriset. Det visar sig att lösningen med bergkyla eller kompressorkyla är de bästa alternativen där en kompressordriven kylmaskin ses som den mest lönsammaste men ur en miljöaspekt är den det mindre bra även om den kylmaskin som används i denna undersökning använder sig av ett köldmedium med förhållandevis lågt GWP-värde. / This study’s purpose is to give suggestions of a new cooling system in a commercial building. The current system implies that the cooling come from tap cold water that flushes into a heat exchanger, this solution is both expensive and have a bad impact on the environment. The property owner isn’t satisfied with this and want to remake the system. There isn`t many measurement values that I can use to calculate the effect and energy needs for the building except the water consumption in the cooling system. Because of this uncertainty two cases have been used in this study. The first has an effect need of 80 kW and the other have an effect around 130 kW. From these two cases has an effect and energy profile been made from each of the two cases. With the profiles made, can a new solution be presented and in this study we have four different methods for the cooling system. An investigation has been made on district cooling, ground cooling, absorption cooling and compressor cooling. The district cooling isn`t possible today because it doesn’t exist but the local energy company having discussions about it and because of this, district cooling is a possible future solution. The study shows that to wait for a district cooling isn´t a profitable solution, neither is the solution with the absorption cooler, the absorption machine is being driven by district heat and the price is too high in Bollnäs. This study shows that ground cooling or compressor cooling are the best options in this case. The compressor cooling is the most profitable, but it has a downside in the environment perspective. All energy is based on electricity energy, and the refrigerant can affect the environment in a bad way if it´s a leak. But I should say that the cooling machine used in this study uses a refrigerant that has a relatively low GWP-value.