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A computer model has been developed to analyze the flow of a dissociating gas through a porous metal matrix. The program predicts the transient temperature distributions through the coolant gas and matrix along with the pressure distribution and mass flow rate. The differential equations used in developing the program are documented in the literature of represent logical extensions of documented equations. The derivation of the finite difference equations is presented. Comparisons of experimental data with computer predictions are shown and indicate that the predictions fall within the experimental error in the data. A source listing of the computer program is contained in the Appendix.

Energibolaget Stockholm Exergi (SE) har satt upp målet att driva en klimatpositiv verksamhet till 2025. För att möta miljömålet planerar företaget att bygga en BECCS-anläggning (Bio Energy Carbon Capture and Storage) till kraftvärmeverket KVV8 där biogen koldioxid avskiljs med HPC-absorption (Hot Potasium Carbonates). Den avskilda koldioxiden ska därefter förvätskas, skeppas och lagras i en djuphavsbotten. I anslutning med BECCS-anläggningen byggs därför en kylanläggning för att förvätska och trycksätta den avskilda koldioxiden.  Förvätskningsanläggningen för koldioxid planeras inte vara i drift under sommarmånaderna juni till och med augusti då KVV8 är avstängd. Sommartid är högsäsong för fjärrkylaproduktionen på SE:s fjärrkylanät och under värmetopparna finns ett behov av extra redundans på nätet. Därför studeras möjligheten att nyttja förvätskningsanläggningen till fjärrkylaproduktion.  Utformningen av en förvätskningsanläggning med önskade slutvillkor om 7 bar och -50 ̊C är idag inte framtagen. Studien listar därför hur tre av de anläggningstyper som undersöks mest idag skulle kunna användas för fjärrkylaproduktion; dels en CO2-NH3-kaskadcykel (Fall 1), en NH3-extern cykel (Fall 2) och en CO2-intern cykel (Fall 3). Modellen för kaskadcykeln är framtagen i av Alabdulkarem et al. (2012) samt Dopazo och Fernández-Seara (2010). Modellerna för den NH3-externa och CO2-interna kylcyklerna är framtagna av Adhikari et al. (2014) och Øi et al. (2016). I det här arbetet har anläggningarna simulerats i Chemcad och anpassats till SE:s ingångs och produktvillkor på CO2-gasen. Enhetliga processvillkor har använts för simuleringarna av Fall 1-3. Därefter har förslag på hur Fall 1-3 kan nyttjats för fjärrkylaproduktion tagits fram och simulerats.  För Fall 1,2 och 3 framtogs kopplingsförslag som genererade kyleffekter till fjärrkylanätet om 22,2; 15,6 och 13,1 MW. COP för kylcyklerna beräknades till 4,6; 5,8 och 4,1.  Investeringsbehovet bedöms högt främst till följd av rördragning och markarbete för ett sjövattenledningspar som tillförser fjärrkylaanläggningens kylvattenbehov. Investeringsbehovet för Fall 1, 2 och 3 bedömdes till ungefär 52,7; 50,6 och 54,2 MSEK. Av det totala investeringsbehovet står sjövattenledningen för ungefär halva investeringsbehovet. I den här studien har höga påslagsfaktorer använts för bland annat oförutsedda kostnader eftersom att utredningen är i ett tidigt stadie.  Som alternativ till fjärrkylaproduktion med direkt anslutning mellan förvätskningsanläggningen och fjärrkylanätet diskuteras även användningen av en mellankrets (Fall 4). Ett förslag på hur mellankretsen kan utformas och dimensioneras har tagits fram av Energiingenjörspraktikant Nasim Rafieyan (2020) under handledning av Förbränningsingenjör Hans P. Larsson. Mellankretsen har tagits fram med tre olika köldbärare; etanol, metanol och en metanol/vattenlösning. / The energy company Stockholm Exergy (SE) has set the goal of running a climate positive business by 2025. To meet the environmental goal, the company plans to build a BECCS plant (Bio Energy Carbon Capture and Storage) for the combined heat and power plant KVV8. The carbon dioxide of the plants flue gases will then be separated with HPC absorption (Hot Potassium Carbonates). The separated carbon dioxide is then to be liquefied, shipped and stored in a deep sea bottom. To liquefy the separated carbon dioxide a cooling plant is being built in connection to the BECCS facility.  The liquefaction plant is expected to not be operating between the summer months of June through August. Summer time is also the when the demand on district cooling is at its highest. To increase the redundancy of cooling capacity during high demand periods the possibility of using the liquefaction plant for district cooling production has been investigated.  The design of a liquefaction plant with the final conditions of 7 bar and -50 ̊C is yet to be fully developed. The study therefore investigates how three of the most researched liquefaction types could be used for district cooling production which is a CO2-NH3 cascade cycle (Case 1), an NH3 external cycle (Case 2) and a CO2 internal cycle (Case 3). The model for the cascade cycle is developed in by Alabdulkarem et al. (2012) as well as Dopazo and Fernández-Seara (2010). The models for the NH3 external and CO2 internal cooling cycles has been developed by Adhikari et al. (2014) and Øi et al. (2016). The liquefaction plants have been simulated in Chemcad with uniform process conditions as well as SE’s CO2 input and product conditions. Subsequently, a proposal on how each of the three cases can be used for district cooling production were developed.  For proposals on district cooling production for Case 1-3 are expected to be generating a cooling effect of 22.2, 15.6 and 13.1 MW. The COP for the cooling cycles was calculated to be 4.6, 5.8 and 4.1.  The investment capital is expected to be high, mainly as a result of piping and ground work for a seawater pipeline to supply the district cooling plant with cooling water. The total investment capital for Case 1, 2 and 3 were estimated to be approximately 52.7, 50.6 and 54.2 MSEK. The sea water pipeline accounts for almost half of the total investment capital. Since the investment capital has been reviewed at an early stage typical percentages such as unforeseen costs were set high for the project.  As an alternative to district cooling production where the liquefaction plant and the district cooling network are directly connected, an intermediate circuit has also been reviewed (Case 4). A proposal on how the intermediate circuit could be designed and dimensioned has been developed by Energy Engineering trainee Nasim Rafieyan (2020) under the supervision of Combustion Engineer Hans P. Larsson (SE). The intermediate circuit has been dimensioned using three different refrigerants; ethanol, methanol and a methanol/water solution.

Yes / Polymerase chain reaction (PCR) has become a powerful tool for detecting various diseases due to its high sensitivity and specificity. However, the long thermocycling time and the bulky system have limited the application of PCR devices in Point-of-care testing. Herein, we have proposed an efficient, low-cost, and hand-hold PCR microdevice, mainly including a control module based on water-cooling technology and an amplification module fabricated by 3D printing. The whole device is tiny and can be easily hand-held with a size of about 110 mm × 100 mm × 40 mm and a weight of about 300 g at a low cost of about $170.83. Based on the water-cooling technology, the device can efficiently perform 30 thermal cycles within 46 min at a heating/cooling rate of 4.0/8.1 ℃/s. To test our instrument, plasmid DNA dilutions were amplified with this device; the results demonstrate successful nucleic acid amplification of the …

Cold spray is an additive manufacturing method in which powder particles are accelerated through a supersonic nozzle and impinged upon a nearby substrate, provided they reach their so-called critical velocity. True to its name, the cold spray process employs lower particle temperatures than other thermal spray processes while the particle velocities are comparably high. Because bonding occurs mostly in the solid state and at high speeds, cold spray deposits are distinguished for having low porosity and low residual stresses which nearly match those of the bulk material. One complication with the cold spray process is the tendency for nozzles to clog when spraying (in general) low-melting-point or dense metal powders. Clogging occurs when particles collide with the inner nozzle wall and bond to it rather than bouncing off and continuing downstream towards the substrate. The particles accumulate and eventually plug the nozzle passage. Clogging is inconvenient because it interrupts the spraying process, making it impossible to complete a task. Furthermore, when particle buildup occurs inside the nozzle, the working cross-sectional area decreases, which decreases the flow velocity and therefore the particle velocity, ultimately jeopardizing the particles’ ability to reach critical velocity at the substrate. In this work, computational fluid dynamics (CFD) is used to study various aspects of nozzle clogging. Nozzle cooling with supercritical CO2 as the refrigerant is investigated as a means to prevent clogging. The effects of nozzle cooling on both the driving gas and the particles are addressed. Simplified pressure oscillations at the nozzle inlet are imposed to determine whether such oscillations, if present, can cause clogging. Subsequently, more realistic and complicated flow oscillations are introduced to isolate a potential root cause of clogging. Finally, several novel nozzle internal geometries are evaluated for their effectiveness at preventing clogging. A recommendation is provided for a nozzle to be tested experimentally because it might completely prevent clogging.

The goal of a gas turbine engine designer is to reduce the amount of coolant used to cool the critical turbine surfaces, while at the same time extracting more benefit from the coolant flow that is used. Fan-shaped holes offer this opportunity, reducing the normal jet momentum and spreading the coolant in the lateral direction providing better surface coverage. The main drawback of fan-shaped cooling holes is the added manufacturing cost from the need for electrical discharge machining instead of the laser drilling used for cylindrical holes. This research focused on examining the performance of fan-shaped holes on two critical turbine surfaces; the vane and endwall. This research was the first to offer a complete characterization of film-cooling on a turbine vane surface, both in single and multiple row configurations. Infrared thermography was used to measure adiabatic wall temperatures, and a unique rigorous image transformation routine was developed to unwrap the surface images. Film-cooling computations were also done comparing the performance of two popular turbulence models, the RNG-kε and the v2-f model, in predicting film-cooling effectiveness. Results showed that the RNG-kε offered the closest prediction in terms of averaged effectiveness along the vane surface. The v2-f model more accurately predicted the separated flow at the leading edge and on the suction side, but did not predict the lateral jet spreading well, which led to an over-prediction in film-cooling effectiveness. The intent for the endwall surface was to directly compare the cooling and aerodynamic performance of cylindrical holes to fan-shaped holes. This was the first direct comparison of the two geometries on the endwall. The effect of upstream injection and elevated inlet freestream turbulence was also investigated for both hole geometries. Results indicated that fan-shaped film-cooling holes provided an increase in film-cooling effectiveness of 75% on average above cylindrical film-cooling holes, while at the same time producing less total pressure losses through the passage. The effect of upstream injection was to saturate the near wall flow with coolant, increasing effectiveness levels in the downstream passage, while high freestream turbulence generally lowered effectiveness levels on the endwall. / Ph. D.

This work presents direct and large eddy simulations of a wide range of heat augmentation surfaces roughened by modified dimples/protrusions. The dissertation is composed of two main parts: Part I (Chapters 2-4) for compact heat exchangers and Part II (Chapter 5) for internal cooling of rotating turbine blades. Part I consists of three phases: Phase I (Chapter 2) investigates flow structure and heat transfer distribution in a channel with dimples/protrusions; Phase II (Chapter 3) studies the application of dimples as surface roughness on plain fins; and Phase III (Chapter 4) considers a new fin shape, the split-dimple fin, that is based on modifying the conventional dimple shape. Chapter 2 presents direct and large eddy simulations conducted of a fin bank over a wide range of Reynolds numbers, ReH=200-15,000, covering the laminar to fully turbulent flow regimes and using two channel height geometries. While the smaller fin pitch channel has better performance in the low to medium Reynolds number range, both channel heights show similar trends in the fully turbulent regime. Moreover, analysis of the results shows that vortices generated in the dimple cavity and at the dimple rim contribute substantially to heat transfer from the dimpled surface, whereas flow impingement and acceleration between protrusions contribute substantially on the protrusion side. Chapter 3 considers applying dimples as surface roughness on plain fin surfaces to further enhance heat transfer from the fin. Three fin geometries that consider dimple imprint diameter effect and perforation effect are considered. The dimple imprint diameter has a minimal effect on the flow and heat transfer of the fin. However, the introduction of perforation in the dimple significantly changes the flow structure and heat transfer on the dimple side of the fin by eliminating recirculation regions in the dimple and generating higher intensity vortical structures. Chapter 4 presents a novel fin shape, the split-dimple fin, which consists of half a dimple and half a protrusion with an opening between them. The split dimple provides an additional mechanism for augmenting heat transfer by perturbing continuous boundary layer formation on the fin surface and generating energetic shear layers. While the protruding geometry of the split dimple augments heat transfer profoundly, it also increase pressure drop. The split dimple fin results in heat conductance that is 60–175% higher than a plain fin, but at a cost of 4–8 times the frictional losses. Chapter 5 studies the employment of dimples/protrusions on opposite sides for internal cooling of rotating turbine blades. Two geometries with two dimple/protrusion depths are investigated over a wide range of rotation numbers, Rob=-0.77 to 1.10. Results show that the dimple side is more sensitive to the destabilizing forces on the trailing surface, while both react similarly to the stabilizing effect on the leading side. It is concluded that placing the protrusion on the trailing side for low rotation number, |Rob|<0.2, provides better performance, while it is more beneficial to place the dimple side on the trailing side for higher rotation numbers. / Ph. D.