• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 139
  • 71
  • 22
  • 14
  • 10
  • 9
  • 6
  • 4
  • 3
  • 2
  • 1
  • 1
  • Tagged with
  • 326
  • 326
  • 128
  • 108
  • 84
  • 53
  • 52
  • 50
  • 50
  • 48
  • 47
  • 43
  • 42
  • 38
  • 32
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Design and performance of a small scale waste heat recovery unit

Ward, Christopher 05 December 2011 (has links)
A microchannel heat exchanger was designed for diesel waste heat recovery and its performance was evaluated. The 21x15x8 cm unit was constructed from diffusion brazed stainless steel lamina and weighed 11 kg. Operating from a 13.4 kW generator with an exhaust temperature of 500 °C the unit delivered 11.1 kW of thermal energy at the design point with an effectiveness of 0.87. If coupled with an organic Rankine bottoming cycle this has the potential of boosting system power output by 35%. Performance was found to be insensitive to cold side flow conditions. Soot accumulation was found to be problematic, which caused a steady exhaust pressure rise at the device but did not affect the thermal performance. / Graduation date: 2012
72

[pt] MODELAMENTO DO CONSUMO DE CAL NO PROCESSO DE DESSULFURAÇÃO DE GASES DE COMBUSTÃO DE UMA COQUERIA DO TIPO HEAT RECOVERY USANDO REDES NEURAIS ARTIFICIAIS / [en] MODELING LIME CONSUMPTION OF A DESULFURIZATION PROCESS FROM GASES OF A HEAT RECOVERY COKE PRODUCTION PLANT USING NEURAL NETWORK DEVELOPMENT

FREDERICO MADUREIRA MATOS ALMEIDA 26 February 2021 (has links)
[pt] A produção de coque metalúrgico em plantas do tipo heat recovery convertem todo o calor gerado da combustão de gases destilados durante a coqueificação em vapor e eletricidade, portanto eliminando a necessidade de processamento de sub-produtos químicos e rejeitos perigosos. Os gases, após a etapa de inertização no interior dos fornos, são direcionados à planta de dessulfuração denominada flue gas dessulfurization que utiliza lama de cal para abatimento de compostos SOx (SO2 e SO3) e filtros de mangas para remoção do resíduo gerado, cinzas de cal, precedente ao descarte para a atmosfera. Em virtude do alto custo da cal torna-se importante modelar o processo e avaliar quais são as principais variáveis que impactam no re-sultado, logo permitindo atuação no processo para torna-lo mais competitivo e am-bientalmente sustentável. A proposta deste trabalho foi elaborar um modelo matemático usando redes neurais artificiais para determinar as principais variáveis que impactam o consumo específico de cal no processo. A literatura existente revela que os principais parâmetros que impactam a eficiência de remoção de enxofre, logo a redução de consumo específico de cal, são temperatura de aproximação e relação Ca/S no processo. Este estudo indicou que o consumo está relacionado, principal-mente, aos parâmetros de temperatura dos gases na entrada e saída do SDA, além de concentração de oxigênio na chaminé principal e densidade da lama de cal utilizada de acordo com a análise de sensibilidade de rede neural feedfoward backpropagation com arquitetura MLP 14-19-2 e função de transferência tangente hiperbólica na ca-mada intermediária e logística na camada de saída. A avaliação reforçou o efeito do aumento da temperatura de saída dos gases no consumo específico de cal conforme literatura e adicionou parâmetros relevantes: temperatura de entrada dos gases, con-centração de O2(g) na chaminé e densidade da lama. / [en] The production of metallurgical coke in heat recovery coke production plants converts all heat generated from the combustion of distilled gases during coking pro-duction to steam and electricity, thus eliminating the need of processing hazardous by-products chemical substances. The gases, after inertization inside the ovens, are directed to the desulphurization plant called flue gas desulphurization (FGD) which uses lime slurry to remove SOx compounds (SO2 and SO3) and bag filters to remove the generated residue, lime ash. Due to the high cost of lime, it is important to model the process and evaluate which are the main variables that affects its result, thus allowing action in the process to make it more competitive and environmentally sus-tainable. The purpose of this work was to develop a mathematical model using arti-ficial neural networks to determine the main variables that affect lime consumption in the desulphurization process. Literature reveals that the main parameters that in-fluence sulfur removal efficiency, thus reducing specific lime consumption, are ap-proach to adiabatic saturation temperature and Ca/S ratio in the process. This study indicated that consumption is mainly related to the inlet and outlet SDA gas temper-atures, oxygen concentration in stack and lime slurry density according to the feed-foward backpropagation neural network sensitivity analysis. MLP 14-19-2 and hy-perbolic tangent transfer function in the intermediate layer and logistics in the output layer. Thus, the evaluation reinforced the effect of the increase of the gas outlet tem-perature on the specific lime consumption according to the literature, but also added new parameters: gas inlet temperature, O2 (g) concentration in the outlet of stack and lime slurry density.
73

Sustainable building ventilation solutions with heat recovery from waste heat

Nourozi, Behrouz January 2019 (has links)
The energy used by building sector accounts for approximately 40% of the total energy usage. In residential buildings, 30-60% of this energy is used for space heating which is mainly wasted by transmission heat losses. A share of 20-30% is lost by the discarded residential wastewater and the rest is devoted to ventilation heat loss.   The main objective of this work was to evaluate the thermal potential of residential wastewater for improving the performance of mechanical ventilation with heat recovery (MVHR) systems during the coldest periods of year. The recovered heat from wastewater was used to preheat the incoming cold outdoor air to the MVHR in order to avoid frost formation on the heat exchanger surface.   Dynamic simulations using TRNSYS were used to evaluate the performance of the suggested air preheating systems as well as the impact of air preheating on the entire system. Temperature control systems were suggested based on the identified frost thresholds in order to optimally use the limited thermal capacity of wastewater and maintain high temperature efficiency of MVHR. Two configurations of air preheating systems with temperature stratified and unstratified tanks were designed and compared. A life cycle cost analysis further investigated the cost effectiveness of the studied systems.   The results obtained by this research work indicated that residential wastewater had the sufficient thermal potential to reduce the defrosting need of MVHR systems (equipped with a plate heat exchanger) in central Swedish cities to 25%. For colder regions in northern Sweden, the defrosting time was decreased by 50%. The temperature control systems could assure MVHR temperature efficiencies of more than 80% for most of the heating season while frosting period was minimized. LCC analysis revealed that wastewater air preheating systems equipped with temperature stratified and unstratified storage tanks could pay off their costs in 17 and 8 years, respectively. / <p>QC 20190830</p>
74

The geometric characterization and thermal performance of a microchannel heat exchanger for diesel engine waste heat recovery

Yih, James S. 29 November 2011 (has links)
Rising energy demands and the continual push to find more energy efficient technologies have been the impetus for the investigation of waste heat recovery techniques. Diesel engine exhaust heat utilization has the potential to significantly reduce the consumption of fossil fuels and reduce the release of greenhouse gases, because diesel engines are ubiquitous in industry and transportation. The exhaust energy can used to provide refrigeration by implementing an organic Rankine cycle coupled with a vapor-compression cycle. A critical component in this system, and in any waste heat recovery system, is the heat exchanger that extracts the heat from the exhaust. In this study, a cross-flow microchannel heat exchanger was geometrically examined and thermally tested under laboratory conditions. The heat exchanger, referred to as the Heat Recovery Unit (HRU), was designed to transfer diesel exhaust energy to a heat transfer oil. Two methods were developed to measure the geometry of the microchannels. The first was based on image processing of microscope photographs, and the second involved an analysis of profilometer measurements. Both methods revealed that the exhaust channels (air channels) were, on average, smaller in cross-sectional area by 11% when compared to the design. The cross-sectional area of the oil channels were 8% smaller than their design. The hydraulic diameters for both channel geometries were close to their design. Hot air was used to simulate diesel engine exhaust. Thermal testing of the heat exchanger included measurements of heat transfer, effectiveness, air pressure drop, and oil pressure drop. The experimental results for the heat transfer and effectiveness agreed well with the model predictions. However, the measured air pressure drop and oil pressure drop were significantly higher than the model. The discrepancy was attributed to the model's ideal representation of the channel areas. Additionally, since the model did not account for the complex flow path of the oil stream, the measured oil pressure drop was much higher than the predicted pressure drop. The highest duty of the Heat Recovery Unit observed during the experimental tests was 12.3 kW and the highest effectiveness was 97.8%. To examine the flow distribution through the air channels, velocity measurements were collected at the outlet of the Heat Recovery Unit using a hot film anemometer. For unheated air flow, the profile measurements indicated that there was flow maldistribution. A temperature profile was measured and analyzed for a thermally loaded condition. / Graduation date: 2012
75

Performance of a thermally activated cooling system and design of a microchannel heat recovery unit

Seward, Ryan 09 March 2012 (has links)
The performance of a combined vapor-compression cycle/ORC is evaluated using waste-heat from a diesel generator. A flat plate microchannel heat exchanger is employed to provide energy exchange between the diesel exhaust stream and an oil loop, which provides energy to a boiler. This study finds an increased diesel duty corresponds with an increased cooling capacity, for a maximum of 5 kW of cooling (with 13.5 kWe diesel load). System COP is reduced with a higher input power due to limitations in the cooling cycle. A number of solutions are identified to increase the COP and cooling capacity. A new microchannel heat exchanger to recovery heat is designed to increase performance compared to the previous version. / Graduation date: 2012
76

Att ta fram underlag för val av luftbehandlingssystem med återvinningssystem i Förvaltarens fastigheter / To provide data for the selection of HVAC systems with recycling systems in the Förvaltarens properties

Mohamed, Mahamud, Long, Xianyun January 2014 (has links)
Sverige och EU har man som mål att halvera energianvändningen fram till 2050 och det arbetet måste starta nu. Det är 15 miljoner kvm byggyta som måste halvera sin energianvändning varje år och i 40 år framåt. Redan idag är 70 % av alla hus till 2050 byggda, vilket innebär att även om vi skulle bygga passivhus fram tills dess skulle det inte räcka för att nå målet. Det är alltså en stor utmaning att halvera energianvändningen till 2050. En jämförelsestudie har genomförts mellan två värmeåtervinningssystem. Frånluftssystem med värmeåtervinning och från- och tilluftssystem med värmeåtervinning. Med hjälp av resultaten av genomförda projekt från två olika fastighetsägare har slutsatser kunnat dras. Slutsatserna är underlag till parametrar som påverkar valet av värmeåtervinningssystem. För att veta vad som är lämpligt har intervjuer genomförts med sakkunniga personer, fastighetsbolags energiansvariga, leverantörer samt konsulter.  Utifrån de intervjuer som genomfördes har uppfattning uppkommit om att alla har olika synpunkter och värderingar vid val av ventilationssystem samt att det är många faktorer som spelar roll vid val av ventilationssystem. I rapporten intervjuas två av Stockholms största fastighetsbolag: Stockholms Hem och Svenska Bostäder. Både fastighetsbolagen genomförde ett ”pilotprojekt” där man utfört prövning och utveckling av nya tekniska system. Syftet med pilotprojektet var att göra ett underlag för framtida projekt. De båda fastighetsbolagens val av ventilationssystem var situationsanpassade. Stockholms hem valde att använda sig av FX pga. affärsmässiga skäl samt utformningen av fastigheterna. Svenska Bostäder utförde större projekt där man totalrenoverade fastigheter, och därmed använde sig av FTX pga. klimatmässiga skäl. / Sweden has alongside with EU set a up goal to reduce the usage of energy with 50 % by 2050, a goal that Sweden to start working towards today/now. It is 15 million square meters of building space that needs to decrease its use of energy every year in 40 years. 70 % of all the buildings that are meant to be build in Sweden by 2050 are already made today, this strongly implicates that we will not be able to reach the goal even if the remaining 30% are strictly passive houses. It will be a demanding challenge to reduce the energy usage to half of its current state. A comparison has been made between two studies on waste heat recovery system, specifically the exhaust system with heat recovery and exhaust and supply air with heat recovery. A conclusion has be drawn from results of the two studies that were made. The conclusions are the main source for the parameters affecting the choice of waste heat recovery system. In order to know what was suitable for the goal, Interviews were made with experienced staffs, a property company, energy managers, contractors and consultants. Based on the interviews made, we concluded that all the parties had different views and standards when selecting a ventilation system, since there are many factors that play major roles in different areas. “Stockholms Hem” and “Svenska Bostäder” which is Two of Stockholm’s leading real estate companies were interviewed for this report. The two companies conducted a “pilot project” where they performed the investigation and development of new established technical systems. The pilot project was meant to be a base for future projects. The company’s choice of ventilation system was adapted after the situation. “Stockholms hem” chaose to use the an exhaust air heat pump due to business related reason and the design of the building, whereas “Svenska bostäder “ implemented major projects that renovated properties thus they chose an exhaust supply air heat exchange system due to climate reasons.
77

Analysis of the COED process and optimization of flue gas heat recovery from a second law perspective

Unruh, Terry Lee. January 1979 (has links)
Call number: LD2668 .T4 1979 U57 / Master of Science
78

The Effect of Non-condensable Gases Removal on Air Gap Membrane Distillation: Experimental and Simulation Studies

Alsaadi, Ahmad S. 04 1900 (has links)
In the kingdom of Saudi Arabia (KSA), the current seawater desalination technologies are completely relying on burning unsustainable crude oil as their main energy driver. Saudi authorities have realized that the KSA is not going to be protected from the future global energy crisis and have started to set up a plan to diversify its energy resources. Membrane Distillation (MD) has emerged as an attractive alternative desalination process. It combines advantages from both thermal and membrane-based technologies and holds the potential of being a cost-effective separation process that can utilize low-grade waste heat or renewable energy. MD has four different configurations; among them is Air Gap Membrane Distillation (AGMD) which is the second most commonly tested and the most commercially available pilot-plant design. AGMD has a stagnant thin layer of air between the membrane and the condensation surface. This layer introduces a mass transfer resistance that makes the process require a large membrane surface area if a large quantity of fresh water is desired. This dissertation reports on experimental and theoretical work conducted to enhance the AGMD flux by removing non-condensable gases from the module and replacing it with either vacuum, liquid water or porous materials. At first, a mathematical model for AGMD was developed and validated experimentally to create a baseline for improvements that could be achieved after the removal of non-condensable gases. The mathematical model was then modified to simulate the process under vacuum where it showed a flux enhancement that reached 286%. The Water Gap Membrane Distillation (WGMD) configuration improved the flux by almost the same percentage. Since enhancing the flux is expected to increase temperature polarization effects, a theoretical study was conducted on the effect of temperature polarization in a Vacuum Membrane Distillation (VMD) configuration. The study showed that the effect of temperature polarization at small temperature difference (3-7) degree Celsius between the bulk feed and coolant temperatures is significantly high. This may indicate the importance of mitigating the effect of temperature polarization in large scale modules operating at small temperature difference across the membrane. The dissertation concluded with some recommendations for future work.
79

Development of a range of air-to-air heat pipe heat recovery heat exchangers

Meyer, Meyer 12 1900 (has links)
Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: As the demand for less expensive energy is increasing world-wide, energy conservation is becoming a more-and-more important economic consideration. In light of this, means to recover energy from waste fluid streams is also becoming more-and-more important. An efficient and cost effective means of conserving energy is to recover heat from a low temperature waste fluid stream and use this heat to preheat another process stream. Heat pipe heat exchangers (HPHEs) are devices capable of cost effectively salvaging wasted energy in this way. HPHEs are liquid-coupled indirect transfer type heat exchangers except that the HPHE employs heat pipes or thermosyphons as the major heat transfer mechanism from the high temperature to the low-temperature fluid. The primary advantage of using a HPHE is that it does not require an external pump to circulate the coupling fluid. The hot and cold streams can also be completely isolated preventing cross-contamination of the fluids. In addition, the HPHE has no moving parts. In this thesis, the development of a range of air-to-air HPHEs is investigated. Such an investigation involved the theoretical modelling of HPHEs such that a demonstration unit could be designed, installed in a practical industrial application and then evaluated by considering various financial aspects such as initial costs, running costs and energy savings. To develop the HPHE theoretical model, inside heat transfer coefficients for the evaporator and condenser sections of thermosyphons were investigated with R134a and Butane as two separate working fluids. The experiments on the thermosyphons were undertaken at vertical and at an inclination angle of 45° to the horizontal. Different diameters were considered and evaporator to condenser length ratios kept constant. The results showed that R134a provided for larger heat transfer rates than the Butane operated thermosyphons for similar temperature differences despite the fact that the latent heat of vaporization for Butane is higher than that of R134a. As an example, a R134a charged thermosyphon yielded heat transfer rates in the region of 1160 W whilst the same thermosyphon charged with Butane yielded heat transfer rates in the region of 730 W at 23 °C . Results also showed that higher heat transfer rates were possible when the thermosyphons operated at 45°. Typically, for a thermosyphon with a diameter of 31.9 mm and an evaporator to condenser length ratio of 0.24, an increase in the heat transfer rate of 24 % could be achieved. Theoretical inside heat transfer coefficients were also formulated which were found to correlate reasonably well with most proposed correlations. However, an understanding of the detailed two-phase flow and heat transfer behaviour of the working fluid inside thermosyphons is difficult to model. Correlations proposing this behaviour were formulated and include the use of R134a and Butane as the working fluids. The correlations were formulated from thermosyphons of diameters of 14.99 mm, 17.272 mm, 22.225 mm and 31.9 mm. The evaporator to condenser length ratio for the 31.9 mm diameter thermosyphon was 0.24 whilst the other thermosyphons had ratios of 1. The heat fluxes ranged from 1800-43500 W/m2. The following theoretical inside heat transfer coefficients were proposed for vertical and inclined operations (READ CORRECT FORMULA IN FULL TEXT ABSTRACT) φ = 90° ei h = 3.4516x105Ja−0.855Ku1.344 φ = 45° ei h = 1.4796x105Ja−0.993Ku1.3 φ = 90° l l l ci l l v h x k g 1/ 3 2.05 2 4.61561 109Re 0.364 ν ρ ρ ρ − ⎡ ⎡ ⎛ ⎞⎤ ⎤ = ⎢ ⎢ ⎜ ⎟⎥ ⎥ ⎢ ⎢ ⎜ − ⎟⎥ ⎥ ⎣ ⎣ ⎝ ⎠⎦ ⎦ φ = 45° l l l ci l l v h x k g 1/ 3 1.916 2 3.7233 10 5Re 0.136 ν ρ ρ ρ − ⎡ ⎡ ⎛ ⎞⎤ ⎤ = ⎢ ⎢ ⎜ ⎟⎥ ⎥ ⎢ ⎢ ⎜ − ⎟⎥ ⎥ ⎣ ⎣ ⎝ ⎠⎦ ⎦ The theoretically modelled demonstration HPHE was installed into an existing air drier system. Heat recoveries of approximately 8.8 kW could be recovered for the hot waste stream with a hot air mass flow rate of 0.55 kg/s at an inlet temperature of 51.64 °C and outlet temperature of 35.9 °C in an environment of 20 °C. Based on this recovery, energy savings of 32.18 % could be achieved and a payback period for the HPHE was calculated in the region of 3.3 years. It is recommended that not withstanding the accuracies of roughly 25 % achieved by the theoretically predicted correlations to that of the experimental work, performance parameters such as the liquid fill charge ratios, the evaporator to condenser length ratios and the orientation angles should be further investigated. / AFRIKAANSE OPSOMMING: As gevolg van die groeiende aanvraag na goedkoper energie, word die behoud van energie ‘n al hoe belangriker ekonomiese oorweging. Dus word die maniere om energie te herwin van afval-vloeierstrome al hoe meer intensief ondersoek. Een effektiewe manier om energie te herwin, is om die lae-temperatuur-afval-vloeierstroom (wat sou verlore gaan) se hitte te gebruik om ‘n ander vloeierstroom mee te verhit. Hier dien dit dan as voorverhitting van die ander, kouer, vloeierstroom. Hittepyp hitteruilers (HPHR’s) is laekoste toestelle wat gebruik kan word vir hierdie doel. ‘n HPHR is ‘n vloeistof-gekoppelde indirekte-oordrag hitteruiler, behalwe vir die feit dat dié hitteruiler gebruik maak van hittepype (of hittebuise) wat die grootste deel van sy hitteoordragsmeganisme uitmaak. Die primêre voordele van ‘n HPHR is dat dit geen bewegende dele het nie, die koue- en warmstrome totaal geïsoleer bly van mekaar en geen eksterne pomp benodig word om die werkvloeier mee te sirkuleer nie. In hierdie tesis word ‘n ondersoek gedoen oor die ontwikkeling van ‘n bestek van lug-totlug HPHR’s. Hierdie ondersoek het die teoretiese modellering van so ‘n HPHR geverg, sodat ‘n demonstrasie eenheid ontwerp kon word. Hierdie demonstrasie eenheid is geïnstalleer in ‘n praktiese industriële toepassing waar dit geïvalueer is deur na aspekte soos finansiële voordele en energie-besparings te kyk. Om die teoretiese HPHR model te kon ontwikkel, moes daar gekyk word na die binnehitteoordragskoëffisiënte van die verdamper- en kondensordeursneë, asook R134a en Butaan as onderskeie werksvloeiers. Die eksperimente met die hittebuise is gedoen in die vertikale en 45° (gemeet vanaf die horisontaal) posisies. Verskillende diameters is ook ondersoek, maar met die verdamper- en kondensor-lengteverhouding wat konstant gehou is. Die resultate wys dat R134a as werksvloeier in die hittebuise voorsiening maak vir groter hitteoordragstempo’s in vergelyking met Butaan as werksvloeier by min of meer dieselfde temperatuur verskil – dít ten spyte van die feit dat Butaan ‘n hoër latente-hittetydens- verdampings eienskap het. As voorbeeld gee ‘n R134a-gelaaide hittebuis ‘n hitteoordragstempo van omtrent 1160 W terwyl dieselfde hittebuis wat met Butaan gelaai is, slegs ongeveer 730 W lewer by 23 °C. Die resultate wys ook duidelik dat hoër hitteoordragstempo’s verkry word indien die hittebuis bedryf word teen ‘n hoek van 45°. ‘n Tipiese toename in hitteoordragstempo is ongeveer 24 % vir ‘n hittebuis met ‘n diameter van 31.9 mm en ‘n verdamper- tot kondensor-lengteverhouding van 0.24. Teoretiese binne-hitteoordragskoëffisiënte is ook geformuleer. Dié waardes stem redelik goed ooreen met die meeste voorgestelde korrelasies. Nieteenstaande die feit dat gedetailleerde twee-fase-vloei en die hitteoordragsgedrag van die werksvloeier binne hittebuise nog nie goed deur die wetenskaplike wêreld verstaan word nie. Korrelasies wat hierdie gedrag voorstel is geformuleer en sluit weereens die gebruik van R134a en Butaan as werksvloeiers in. Die korrelasies is geformuleer vanaf hittebuise met diameters van onderskeidelik 14.99 mm, 17.272 mm, 22.225 mm en 31.9 mm. Die verdamper- tot kondensor-lengteverhoudings vir die 31.9 mm deursnit hittebuis was 0.24 terwyl die ander hittebuise ‘n verhouding van 1 gehad het. Die hitte-vloede het gewissel van 1800-45300 W/m2. Die volgende teoretiese geformuleerde binne-hitteoordragskoëffisiënte word voorgestel vir beide vertikale sowel as nie-vertikale toepassing (LEES KORREKTE FORMULE IN VOLTEKS OPSOMMING) φ = 90° ei h = 3.4516x105Ja−0.855Ku1.344 φ = 45° ei h = 1.4796x105Ja−0.993Ku1.3 φ = 90° l l l ci l l v h x k g 1/ 3 2.05 2 4.61561 109Re 0.364 ν ρ ρ ρ − ⎡ ⎡ ⎛ ⎞⎤ ⎤ = ⎢ ⎢ ⎜ ⎟⎥ ⎥ ⎢ ⎢ ⎜ − ⎟⎥ ⎥ ⎣ ⎣ ⎝ ⎠⎦ ⎦ φ = 45° l l l ci l l v h x k g 1/ 3 1.916 2 3.7233 10 5Re 0.136 ν ρ ρ ρ − ⎡ ⎡ ⎛ ⎞⎤ ⎤ = ⎢ ⎢ ⎜ ⎟⎥ ⎥ ⎢ ⎢ ⎜ − ⎟⎥ ⎥ ⎣ ⎣ ⎝ ⎠⎦ ⎦ Die wiskundig-gemodelleerde demostrasie HPHR is geïnstalleer binne ‘n bestaande lugdroër-sisteem. Drywing van om en by 8.8 kW kon herwin word vanaf die warm-afvalvloeierstroom met ‘n massa vloei van 0.55 kg/s teen ‘n inlaattemperatuur van 51.64 °C en ‘n uitlaattemperatuur van 35.9 °C binne ‘n omgewing van 20 °C. Na aanleiding van hierdie herwinning, kan energiebesparings van tot 32.18 % verkry word. Die HPHR se installasiekoste kan binne ‘n berekende tydperk van ongeveer 3.3 jaar gedelg word deur hierdie besparing. Verdamper- tot kondensator-lengteverhouding, vloeistofvulverhouding en die oriëntasiehoek vereis verdere ondersoek, aangesien daar slegs ‘n akkuraatheid van 25 % verkry is tussen teoretiese voorspellings en praktiese metings.
80

Utilising a high pressure, cross flow, stainless steel fintube heat exchanger for direct steam generation from recovered waste heat

Wipplinger, Karl Paul Martin January 2004 (has links)
Thesis (MScEng) -- Stellenbosch University, 2004. / ENGLISH ABSTRACT: Around the world the implementation of heat recovery systems is playing an increasingly important role in the engineering inqustry. The recovered energy is utilised in the plants and saves companies millions in expenses per year. Not only is this seen on the grand scale of industry, but also in everyday life, where for instance turbochargers are used to boost the performance of automobiles by utilising the wasted energy expelled along with exhaust gasses. The aim of this project is to investigate a small scale waste heat recovery system, and to determine the optimum method by which to convert the recovered energy into electrical energy, which can be used as a secondary energy source. The research contained in this thesis, centres on the main components and theory needed for the construction of a small scale waste heat recovery system. Also included, is a theoretical analysis concerning the design and construction of the system, utilising researched theory and a simulation program of the recovery system. The simulation is control volume-based and generates property data on the fluid and exhaust gas throughout the heat exchanger. The final design included a finite element stress analysis of certain parts of the system to ensure safe testing at high pressures and temperatures. The final design resulted in a high pressure, cross flow, stainless steel fintube heat exchanger that, by using a continuous combustion unit as energy source and water as the working fluid, reached efficiencies of up to 74% in direct steam generation testing. The tube-side of the heat exchanger was designed to withstand pressures of up to 2MPa (20bar), which is imperative for the implementation of the next phase, where a turbocharger will be connected to the heat exchanger. The completion of this part of the project has paved the way for further development and implementation of the heat recovery system. / AFRIKAANSE OPSOMMING: Die herwinning van energie begin 'n toenemend belangrike rol in die ingenieurs industrie speel. Die herwonne energie word in fabrieke ben ut en spaar maatskappye milj oene aan uitgawes per jaar. Hierdie beginsel word nie net in die grootskaalse nywerhede toegepas nie, maar ook in die allerdaagse lewe, soos byvoorbeeld in voertuie waar turbo-aanjaers gebruik word om die energie-uitset van enjins te verhoog deur bloot gebruik te maak van die verlore energie wat saam met die uitlaatgasse in die atmosfeer gepomp word. Die doel van hierdie projek is om 'n kleinskaalse energieherwinningstelsel te ondersoek en die mees effektiewe metode te vind om die herwinde energie na elektriese energie om te skakel wat as 'n sekondere energiebron gebruik kan word. Die navorsing bevat in die tesis, kyk na al die hoofkomponente en teoretiese kennis wat nodig is vir die konstruksie van 'n kleinskaalse hitteherwinningstelsel. Ook ingesluit is 'n teoretiese analise ten opsigte van die ontwerp en konstruksie van die sisteem. Dit behels die gebruik van nagevorsde teorie saam met 'n simulasie program van die herwinnings stelsel. Die simulasie program is op kontrole volumes gebasseet en genereer uitlaatgas- en water eienskappe soos dit deur die hitteruiler vloei. Die finale ontwerp bevat 'n eindige element spannmgs analise van sekere kritiese komponente in die stelsel om die veilige gebruik van die sisteem by hoe drukke en temperature te verseker. Die finale ontwerp was 'n hoedruk, kruisvloei, vlekvrye staal finbuis hitteruiler. Deur 'n konstante verbrandingseenheid as energiebron te gebruik saam met water as werksvloeier, het die hitteruiler effektiwiteite van tot 74% in direkte stoomgenerasie-toetse bereik. Die hitteruiler is ontwerp om hoe drukke van tot 2MPa (20bar) te hanteer wat baie belangrik is vir die implementasie van die volgende fase van die projek waar 'n turbo-aanjaer aan die stelsel gekoppel sal. Die suksesvolle voltooiing van hierdie fase van die projek het die weg gebaan vir die verdere ontwikkeling en implimentasie van die energieherwinningsstelsel.

Page generated in 0.0578 seconds