Energianvändningen i världen ökar vilket medför en ökad belastning på miljön. Många industrier har idag ett överskott av värme som vid ett ökat nyttjande skulle kunna reducera andelen primärenergi och således belastningen på miljön samtidigt som ekonomiska besparingar kan erhållas. DIBO Produktionspartner AB är en verkstadsindustri i Katrineholm som bearbetar metall‐ och plastkomponenter i CNC‐maskiner. Maskinparken består av 14 CNC‐maskiner och en kompressor som förser maskinerna med tryckluft. Ventilationssystemet består av två delar, ett till‐ och frånluftssystem kopplat till verkstaden samt ett FTX‐system kopplat till den intilliggande kontorsbyggnaden. Företaget har idag ett värmeöverskott på grund av aktiviteten från de olika CNC‐ maskinerna och tryckluftskompressorn vilket medför höga temperaturer i verkstaden. I dagsläget öppnas en ytterport för att ventilera ut värmeöverskottet så att en lägre temperatur erhålls. Arbetet syftade till att kvantifiera mängden överskottsvärme tillgänglig i verkstaden för att därefter undersöka möjliga externa och interna användningsområden. Värmeöverskottet uppskattades genom att ställa upp en energibalans för verkstaden där tillskott och förluster av värmeenergi jämfördes. Både tillskotten och förlusterna av värmeenergin beräknades genom inventering av verkstadslokalerna, mätningar av el, temperatur och ventilation samt genom simuleringar av verkstadens inomhusklimat. Värmeöverskott i verkstaden förekommer under årets alla månader, även om det är starkt beroende av utomhustemperaturen och aktiviteten i verkstaden, och uppgår årligen till 137 MWh. Beträffande externa användningsområden studerades faktorer som påverkar ett spillvärmesamarbete, den teknik som skulle behövas för att leverera värme externt och möjligheten för DIBO att leverera värme till Katrineholms fjärrvärmenät. Det finns många faktorer som man bör ha i åtanke vid ett samarbete varav några är förtroendet mellan de båda parterna, investeringsuppdelning samt värdering av spillvärmen. För externa värmeleveranser varierar den utrustning som krävs beroende på de aktuella förhållandena, men generellt gäller att anslutningspunkter, en anslutningsledning och i en del fall en cirkulationspump samt en värmepump för uppgradering av värmen behövs. Som ett resultat av att tryckluftskompressorns effekt är förhållandevis låg och värmen luftburen har en värmepump av lämplig storlek ej hittats. Efter kontakt med Tekniska verken i Katrineholm framgick även att energimängden som skulle kunna levereras är för liten för att ett samarbete ska vara av intresse vilket medför att en leverans till fjärrvärmenätet inte är aktuellt i dagsläget. De interna åtgärderna som studerats finns listade i Tabell 1 där även besparingspotential och återbetalningstid framgår. / The Energy use is increasing throughout the world, which causes an increased load on the environment. Today, a lot of industries have unused waste heat, which by extended use would reduce the amount of primary energy sources and thus the environmental load together with economical savings that would apply for the industry. DIBO Produktionspartner AB is a manufacturing industry that processes metal‐ and plastic components in CNC‐machines. The machinery consists of 14 CNC‐machines and one compressor that provide the machines with compressed air. The ventilation system consists of two systems, one supply and exhaust air system for the workshop and one heat exchange system for the adjacent office building. Due to activity from the machines and compressor, the company has excess heat which causes high temperatures in the workshop. Today, a gate is opened in order to vent the excess heat and lower the temperature. This project’s aim was to quantify the amount of excess heat available in the workshop and afterwards investigate possible internal and external uses. The excess heat was estimated by setting up an energy balance for the workshop where heat energy contributions and losses were compared. Both the contributions and losses of heat energy were calculated by a workshop inventory, electricity, temperature and ventilation measurements and through simulations of the workshop’s indoor climate. Results show that excess heat occurs in the workshop every month of the year, largely dependent on the outdoor temperature and activity level in the workshop, and amounts to 137 MWh yearly. Regarding the external uses, factors that affect waste heat cooperation, technology to deliver heat and the possibility for DIBO to deliver heat to the district heating system in Katrineholm, was evaluated. Among all the factors to keep in mind in cooperation, trust between the parties, investment division and valuation of waste heat, are some. The technology needed to deliver heat varies, but common equipment includes connecting points and lines and in some cases a circulation pump as well as a heat pump for upgrading the heat. As a result of an air compressor with relatively low power and airborne heat, a suiting heat pump has not been found. Contact with Tekniska verken in Katrineholm showed that the potential amount of heat energy deliverable to the district heating system is too small to be of interest and therefor a delivery to the district heating network is today not relevant. The internal measures are listed in Table 1 along with their potential savings and payback time.

In an attempt to reduce the dependence on fossil fuels, a variety of research initiatives has focused on increasing the efficiency of conventional energy systems. One such approach is to use waste heat recovery to reclaim energy that is typically lost in the form of dissipative heat. An example of such reclamation is the use of waste heat recovery systems that take low-temperature heat and deliver cooling in space-conditioning applications. In this work, an ejector-based chiller driven by waste heat will be studied from the system to component to sub-component levels, with a specific focus on the ejector. The ejector is a passive device used to compress refrigerants in waste heat driven heat pumps without the use of high grade electricity or wear-prone complex moving parts. With such ejectors, the electrical input for the overall system can be reduced or eliminated entirely under certain conditions, and package sizes can be significantly reduced, allowing for a cooling system that can operate in off-grid, mobile, or remote applications. The performance of this system, measured typically as a coefficient of performance, is primarily dependent on the performance of the ejector pump. This work uses analytical and numerical modeling techniques combined with flow visualization to determine the exact mechanisms of ejector operation, and makes suggestions for ejector performance improvement. Specifically, forcing the presence of two-phase flow has been suggested as a potential tool for performance enhancement. This study determines the effect of two-phase flow on momentum transfer characteristics inside the ejector while operating with refrigerants R134a and R245fa. It is found that reducing the superheat at motive nozzle inlet results in a 12-13% increase in COP with a 14-16 K decrease in driving waste heat temperature. The mechanisms of this improvement are found to be a combination of two effects: the choice of operating fluid (wet vs. dry) and the effect of two-phase flow on the effectiveness of momentum transfer. It is recommended that ejector-based chillers be operated such that the motive nozzle inlet is near saturation, and environmentally friendly dry fluids such as R245fa be used to improve performance. This work provides critical methods for ejector modeling and validation through visualization, as well as guidance on measures to improve ejector design with commensurate beneficial effects on cooling system COP.

This thesis aims to examine energy demand within UK industry and assess the improvement potential available through efficiency measures. The techniques employed throughout the work have been mainly engineering based, drawing on thermodynamics. Alongside this approach, an assessment of drivers and barriers to the technical potential was undertaken. Data availability was a key challenge in the current work. The variety in energy uses meant the use of publically available datasets was limited. A database was constructed utilising site level emissions data, and employed a subsector disaggregation that facilitated energy analysis. The database was used for an analysis of waste heat recovery options. Opportunities were identified in low temperature recovery, heat-ta-power technology, and the transport of heat. Each of these options would require further research and support to be fully realised. It was found that splitting the industrial sector into an energy-intensive and non-energy- intensive subsector, where the grouping was based on the drivers to energy efficiency, allowed generalisations to be made regarding future improvement potential. Based on analysis of past trends, it was found that the energy-intensive subsector has limited potential for further efficiency gains through currently used processes. To make significant improvements radical changes in current processes will be required. A study of the energy-intensive Cement subsector concurred with these findings. Future efficiency improvements in this subsector are likely limited without a shift to alternative cement production. The non-energy-intensive subsector was thought to have relatively greater improvement potential through existing processes. The analysis of these processes is limited by lack of data however. An analysis of the non-energy-intensive Food and drink subsector therefore focussed on improvements in supplying low temperature heat, rather than the efficiency of specific processes. Opportunities through improving steam systems, increasing combined heat-and-power use, and the adoption of heat pumps were found to offer similar improvement potentials.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Rahmatallah Shoureshi. / Ph.D.

In order to keep a high level and to stay competitive in the world market in the future, it is important for the Swedish steel industry to improve their efficiencies continuously and to reduce the energy consumption. In order to realize these goals, the Swedish steel association Jernkotoret was found and by their initiative Triple Steelix was found in 2006 in Berglanden, a significant area for the steel industry. In 2009, the Clean Production Centre was found in Hofors in order to build a cluster of local steel manufacturers, factories and companies. One of those companies is Gästrike Härdverkstad, a small steal heat treatment industry with six employees and about 700.000 tons treated materials every year. The aim for this thesis is to suggest solutions for recovering waste heat and lowering the total energy consumption in furnaces for heat treatment in the case of Gästrike Härdverkstad. Some limitations were necessary to complete the analysis and to come to conclusions. The yearly treated material and energy prices were assumed to be constant and the yearly power consumption was estimated by an extrapolation of a one to five days measurement. Gästrike Härdverkstad is located in Uhrfors, the southern part of Åshammar, a village with 727 inhabitants. There are not any buildings with a possibility to supply heat and there is no district heating in the surroundings. The company has a power consumption of 1.40 GWh/year, of which 65.7% is consumed by the 12 main furnaces. The rest is used by eight seldom used furnaces, devices and auxiliary machines of the support process like fans, pumps, compressor, office heating, and some other. The efficiencies of the main furnaces are between 10% and 20%.The estimated energy consumption of the space heating is about 27 MWh/year, which completely can be covered by the material coolant and the combustion heat of the exhaust gases from the hardening furnaces. Since there are 10 different types of furnaces with different duties and efficiencies, the preheating furnace was taken as an example and compared with a new furnace. According to the needs of Gästrike Härdverkstad, the furnace VAW 60/100-650°C from the company Vötsch was chosen at the cost of 248,827 SEK. The payback time depends on the efficiency. With an efficiency of 40% the payback time would be about 13 years, see Figure 20. After the annealing and ageing, the finished products are cooled down in the building hall by the ambient air. In future, the possibility of preheating the material with the heat of the finished products should be considered. With an efficiency of 30.87%, one preheating furnace could bereplaced, and taken a payback time of 5 years into account; the price of the construction would be allowed to be up to 253,200 SEK.

Thesis (M.E.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references (leaves 106-109). Also available via the World Wide Web.

An analytical transport/reaction model was developed to simulate the catalytic performance of ZnO nanowires as a catalyst support. ZnO nanowires were chosen because they have easily characterized, controllable features and a spatially uniform morphology. The analytical model couples convection in the catalyst flow channel with reaction and diffusion in the porous substrate material; it was developed to show that a simple analytical model with physics-based mass transport and empirical kinetics can be used to capture the essential physics involved in catalytic conversion of hydrocarbons. The model was effective at predicting species conversion efficiency over a range of temperature and flow rate. The model clarifies the relationship between advection, bulk diffusion, pore diffusion, and kinetics. The model was used to optimize the geometry of the experimental catalyst for which it predicted that maximum species conversion density for fixed catalyst surface occurred at a channel height of 520 [mu]m. A modeling study of thermoelectric (TE) vehicle waste heat recovery was conducted based on abundant and inexpensive Mg₂ Si[subscript 0.5] Sn[subscript 0.5] and MnSi[subscript 1.75] TE materials with consideration of performance at the system and TE device levels. The modeling study identified a critical TE design space of fill fraction, leg length, n-/p-type leg area ratio, and current; these parameters needed to be optimized simultaneously for positive TE power output. The TE power output was sensitive to this design space, and the optimal design point was sensitive to engine operating conditions. The maximum net TE power for a 29.5 L strip fin heat exchanger with an 800 K exhaust flow at 7.9 kg/min was 2.25 kW. This work also includes two generations of TE waste heat recovery systems that were built and tested in the exhaust system of a Cummins 6.7 L turbo Diesel engine. The first generation was a small scale heat exchanger intended for concept validation, and the second generation was a full scale heat exchanger that used the entire exhaust flow at high speed and torque. The second generation heat exchanger showed that the model could accurately predict heat transfer, and the maximum experimental heat transfer rate was 15.3 kW for exhaust flow at 7.0 kg/min and 740 K. / text

This study is centered on modeling and experimental efforts to simulate and optimize the performance of thermoelectric generators (TEGs) for waste heat recovery systems for use in motor vehicles. TEGs are being studied and developed for applications in which waste heat, for example, from the exhaust of motor vehicles is converted into usable electricity. TEGs consisting of TE elements integrated with an exhaust heat exchanger require optimization to produce the maximum possible power output. Important optimization parameters include TE element leg length, fill fraction, leg area ratio between n- and p-type legs, and load resistance. A finite difference model was developed to study the interdependencies among these optimization parameters for thermoelectric elements integrated with an exhaust gas heat exchanger. The present study was carried out for TE devices made from n-type Mg₂Si and p-type MnSi[subscript 1.8] based silicides, which are promising TE materials for use at high temperatures associated with some exhaust heat recovery systems. The model uses specified convection boundary conditions instead of specified temperature boundary conditions to duplicate realistic operating conditions for a waste heat recovery system installed in the exhaust of a vehicle. A numerical model for a new waste heat recovery system configuration was proposed which showed an improvement of 40% in net power output over the conventional systems while using approximately 60% more TEG modules. The 1st generation, and an improved 2nd generation TEG module using n-type Mg₂Si and p-type MnSi[subscritp 1.8] based silicides were fabricated and tested to compare and correlate TE power generation with the numerical model. Important results include parameter values for maximum power output per unit area and the interdependencies among those parameters. Heat transfer through the void areas was neglected in the numerical model. When thermal contact resistance between the TE element and the heat exchangers is considered negligible, the numerical model predicts that any volume of TE material can produce the same power per unit area, given the parameters are accurately optimized. Incorporating the thermal contact resistance, the numerical model predicts that the peak power output is greater for longer TE elements with larger leg areas. The optimization results present strategies to improve the performance of TEG modules used for waste heat recovery systems. / text

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Dr. Yogendra Joshi; Committee Member: Dr. S. Mostafa Ghiaasiaan; Committee Member: Dr. Sheldon Jeter. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Dr. Srinivas Garimella; Committee Member: Dr. Samuel Graham; Committee Member: Dr. Sheldon Jeter. Part of the SMARTech Electronic Thesis and Dissertation Collection.