A modeling tool was developed capable of evaluating the thermal performance of a commercial building, for the purpose of objectively quantifying the impacts of both operational changes and technological retrofits. The modeling tool was created using a steady state energy balance approach, discretized into half hour time steps to capture the time varying characteristics of the rate of heat transfer through the building envelope, the ventilation systems, appliance heat gains, heat generated by electricity consumption, solar energy transfer and space heating through exhaust gas energy recovery with the TEG POWER system. Several experimental facilities were used to validate the modeling tool, and to provide inputs to the case studies presented. Data from two separate commercial baking operations was collected, and was shown to be in agreement with the model predictions with a 7% error. Several energy conservation measures were simulated, including switching to idealized methods of exhaust ventilation, sealing and insulating appliances, shutting down appliances during unoccupied hours, and the inclusion of exhaust gas energy harvesting. Implementing all four conservation measures at a single restaurant had the effect of reducing electricity consumption by 14% or approximately 17,700 kWh (64 GJ), and reducing natural gas consumption by 60% or approximately 18,200 m3 (608 GJ) annually. In contrast, proceeding directly to the energy harvesting solution, and bypassing other conservation measures, only allowed for 20% of the total potential energy savings to be realized. If the concepts identified are implemented across 2000 comparable restaurants in Ontario, there is a potential to reduced electricity consumption by 44.4 million kWh and natural gas consumption by 33.7 million cubic meters annually. The measures would effectively eliminate 65,500 metric tonnes of CO2 emissions every year. / Thesis / Master of Applied Science (MASc)

The waste heat recovery technologies have become very relevant since many industrial plants continuously reject large amounts of thermal energy during normal operation which contributes to the increase of the production costs and also impacts the environment. The simulation programs used in industrial engineering enable development and optimization of the operational processes in a cost-effective way. The company Chematur Engineering AB, which supplies chemical plants in many different fields of use on a worldwide basis, was interested in the investigation of the possibilities for effective waste heat recovery from the hydrogenation of dinitrotoluene, which is a sub-process in the toluene diisocyanate manufacture plant. The project objective was to implement waste heat recovery by application of the Organic Rankine Cycle and the Absorption Refrigeration Cycle technologies. Modeling and design of the Organic Rankine Cycle and the Absorption Refrigeration Cycle systems was performed by using Aspen Plus® simulation software where the waste heat carrier was represented by hot water, coming from the internal cooling system in the hydrogenation process. Among the working fluids investigated were ammonia, butane, isobutane, propane, R-123, R-134a, R-227ea, R-245fa, and ammonia-water and LiBr-water working pairs. The simulations have been performed for different plant capacities with different temperatures of the hydrogenation process. The results show that the application of the Organic Rankine Cycle technology is the most feasible solution where the use of ammonia, R-123, R-245fa and butane as the working fluids is beneficial with regards to power production and pay-off time, while R-245fa and butane are the most sustainable choices considering the environment.

The purpose of this thesis is to examine possible waste heat recovery methods in data centers. Predictions indicate that in the next decade data center racks may dissipate 70kW of heat, up from the current levels of 10-15kW. Due to this increase, solutions must be found to increase the efficiency of data center cooling. This thesis will examine possible waste heat recovery technologies which will improve energy efficiency. Possible approaches include phase change materials, thermoelectrics, thermomagnetics, vapor compression cycles, absorbtion and adsorbtion systems. After a thorough evaluation of the possible waste heat engines, the use of an ejector heat pump was evaluated in detail. The principle behind an ejector heat pump is very similar to a vapor compression cycle. However, the compressor is replaced with a pump, boiler and an ejector. These three components require less moving parts and are more cost effective then a comparable compressor, despite a lower efficiency. This system will be examined under general operating conditions in a data center. The heat load is around 15-20kW and air temperatures near 85°C. A parametric study is conducted to determine the viability and cost effectiveness of this system in the data center. Included will be various environmentally friendly working fluids that satisfy the low temperature ranges found in a data center. It is determined that Ammonia presents the best option as a working fluid for this application. Using this system a Coefficient Of Performance of 1.538 at 50°C can be realized. This will result in an estimated 373,000 kW-hr saved over a year and a $36,425 reduction in annual cost. Finally, recommendations for implementation are considered to allow for future design and testing of this viable waste heat recovery device.

A turbine was investigated by various methods of calculating its efficiency. The project was based on an existing impulse turbine, a one-stage turbine set in an organic Rankine cycle with the working fluid being R245fa. Various methods of loss calculation were explored in the search for a method sufficiently accurate to make valid assumptions regarding the turbine performance, while simple enough to be time efficient for use in industrial research and development.  The calculations were primarily made in an isentropic manner, only taking into account losses due to the residual velocity present in the exit flow. Later, an incidence loss was incorporated in the isentropic calculations, resulting in additional losses at off-design conditions. Leaving the isentropic calculations, the work by Tournier, “Axial flow, multi-stage turbine and compressor models” was used. The work presents a method of calculating turbine losses separated into four components: profile, trailing edge, tip clearance and secondary losses. The losses applicable to the case were implemented into the model. Since the flow conditions of the present turbine are extreme, the results were not expected to coincide with the results of Tournier. In order to remedy this problem, the results were compared to results obtained through computational fluid dynamics (CFD) of the turbine. The equations purposed by Tournier were correlated in order to better match the present case. Despite that the equations by Tournier were correlated in order to adjust to the current conditions, the results of the losses calculated through the equations did not obtain results comparable to the ones of the available CFD simulations. More research within the subject is necessary, preferably using other software tools.

With the growth of energy consumption and the optimization of industrial processes worldwide, new energy sources have been explored and investigated. Waste heat is a potential source for the generation of electricity and heat. This heat can be reused at different stages of industrial processes by using absorption heat pumps, which transfer thermal energy from a location with a lower thermal potential to a location with a higher thermal potential. This research work is basically focused on the evaluation of different absorption heat pumps implemented in the SAKO Brno incineration plant. To carry out this purpose, a bibliographic review of this technology has been carried out worldwide, then the mass and energy balance in the compressor is presented, from which the waste heat to be recovered with the pump will be obtained. Using the EES software, the mass and energy balance of the selected pumps is performed, then the amount of heat and electrical energy generated by the plant when implementing each of the pumps is shown, and finally the economic analysis is presented The design and implementation of a heat exchanger in the system is also included as an essential part of improving operation. The best option arises from the highest operational efficiency at the lowest possible cost.

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.

Idag ställs stora krav på företag att vara miljömedvetna och resurseffektiva i sin verksamhet. Vid mjukpapperstillverkning används stora energimängder och inom industrin har det under många år funnits en strävan att energieffektivisera processer och att tillvarata spillenergi, bland annat genom värmeåtervinning. Valmet Tissue Technology Center i Karlstad har idag en pilotmaskinen utan värmeåtervinningssystem. Den här undersökningen gjordes i syfte att ta reda på hur stor återvinningspotentialen är för värmeväxling i pilotmaskinens torkpartier, bestående av Yankeekåpan och TAD-cylindrarna. Tre maskinkoncept undersöktes: DCT®, NTT™ och TAD. Entalpi och effekt i utgående torkluft bestämdes utifrån dess massflöde, temperatur och fukthalt för respektive koncept och torkparti. För att beräkna återvinningspotential i luftflödena undersöktes effektbehov för avsättningsalternativ bestående av förvärmning av förbränningsluft och make-up air, uppvärmning av radiatorvatten samt ånggenerering med Waste Heat Steam Generator. Effekt- och energimässig återvinningspotential beräknades dels teoretiskt och dels reellt med simuleringsprogram för befintliga produkter. Ekonomisk besparing från minskad energianvändning samt investeringskostnad för respektive avsättningsalternativ och torkparti beräknades. Paybacktid användes som mått på ekonomisk lönsamhet. Utöver ovanstående undersöktes om det finns ett samband mellan aktivitet på pilotmaskinen och effekttopparna för fjärrvärmeanvändning i den aktuella byggnaden. Störst entalpi har utgående torkluftsflöden från Yankeekåpan vid DCT-körning följt av NTT-körning. Den största effektmässiga återvinningspotentialen för luftförvärmning finns i TAD-cylinder 1 men betydande tryckfall uppstår i värmeväxlaren på grund av stora luftflöden. Waste Heat Steam Generator kan inte användas ihop med pilotmaskinen på grund av för låg entalpi och effekt i utgående torkluft. Generellt är den reella återvinningspotentialen vid luftförvärmning mindre än den teoretiskt beräknade. Totalt innebär värmeväxling från Yankeekåpan den största årliga energibesparingen vid luftförvärmning. Reell energibesparing vid luftförvärmning i Yankeekåpan är 55 MWh per år vilket motsvarar 4 300 kg gasol. För uppvärmning av radiatorvatten finns den största effekt- och energimässiga återvinningspotentialen vid värmeväxling i Yankeekåpan under DCT-körning följt av NTT-körning. TAD-körning innebär en mindre återvinningspotential vid värmeväxling både i Yankeekåpan och TAD-cylindrarna. Totalt innebär värmeväxling från Yankeekåpan den största årliga energibesparingen vid uppvärmning av radiatorvatten. Reell energibesparing vid uppvärmning av radiatorvatten med torkluft från Yankeekåpan är 153 MWh fjärrvärme per år. Årlig kostnadsbesparing vid luftförvärmning är 43 000 SEK och vid uppvärmning av radiatorvatten 63 400 SEK. Paybacktid för investering i luftförvärmning är 2,6 år och för uppvärmning av radiatorvatten 4,4 år. Ett samband mellan att pilotmaskinen körs och hög fjärrvärmeförbrukning finns, dock är det rutinförändringar kring lokalventilering under körning som främst kan bidra till att sänka de högsta effekttopparna. / There are great demands on industrial companies today to be environmentally responsible and resource-efficient. Within the paper and tissue industry a lot of energy is being used in the processes and since many years there’s been a development towards a more efficient energy use, for example by recovery of waste heat. Valmet Tissue Technology Center in Karlstad, Sweden, has a pilot tissue machine without a waste heat recovery system. This thesis was carried out to investigate the waste heat recovery potential of the pilot machine’s drying sections, being the Yankee hood and TAD cylinders. Three different concepts of the machine were studied: DCT®, NTT™ and TAD. The enthalpy and heat flows of the exhaust air from the drying sections were calculated by the air’s mass flow, temperature and humidity. To calculate the heat recovery potential the heat demand for pre-heating combustion and make-up air, heating radiator water and generating steam by using a Waste Heat Steam Generator was investigated. The heat recovery potential was calculated theoretically but also simulated using programs for real heat exchangers. Economic savings from reduced energy use and investment costs was used to calculate the payback time for each investment alternative. As a separate task the maximum district heating loads in the facility of the pilot machine was cross checked with the pilot machine activity, to clarify any relationship between them. The largest enthalpy was found to be in the exhaust air from the Yankee hood when running the DCT concept followed by the NTT concept. However, the largest heat flow is in the exhaust air from the first TAD cylinder. The air from the first TAD cylinder meant the largest heat recovery potential but caused big pressure drops in the heat exchanger. The Waste Heat Steam Generator cannot be used together with the pilot machine due to too low enthalpy and heat flow in the exhaust air from the drying sections. In general the real heat recovery potential when pre-heating combustion and make-up air is smaller than the theoretical potential. In total, heat exchange using exhaust air from the Yankee hood means the largest energy saving when pre-heating air. The real energy saving when pre-heating air using outgoing air from the Yankee hood is 55 MWh per year, meaning 4 300 kg of propane. The largest potential for heating radiator water occurs when using exhaust air from the Yankee hood when running the DCT concept followed by the NTT concept. The TAD concept means smaller heat recovery potential regardless of air from the Yankee hood or TAD cylinders is being used. In total, heat exchange using outgoing air from the Yankee hood means the largest yearly energy saving when heating radiator water, the real energy saving in district heating being 153 MWh per year. The economic saving when pre-heating air is 43 000 SEK per year and when heating radiator water 63 400 SEK per year. The payback time when investing in pre-heating air is 2,6 years and when heating radiator water 4,4 years. A relationship between running the pilot machine and big loads of district heating use can be seen. However, changing the routines of ventilation in the machine hall during trial days would probably be the easiest way to reduce the maximum loads.

Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Civil Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography : leaves 231-234. / Ph.D.

In the face of the internationally tightened requirements and regulations for CO2 emissions from the transportation sector, waste heat recovery using a thermoelectric generator (TEG) has become the most significant research interest. A vehicular TEG, converting otherwise wasted thermal energy from engines to electricity directly for use in the vehicle systems, is a promising approach for vehicle original equipment manufacturers (OEMs) to reduce fuel consumption and lower CO2 emissions. This thesis aims to explore the main challenges to be faced in the commercialization of TEGs. Based on a review of the literature, four research gaps have been identified, which are respectively: * Translating the material improvements into TEG Performance, * Transient behaviors of vehicular TEGs under driving cycles, * Fuel saving percentage and cost-benefit estimation of TEG, * Bidirectional characteristic of TEM and bifunctional vehicular TEG. To directly address these research gaps, a quasi-static TEM model, a dynamic TEG model, a semi-empirical vehicular TEG model, and a dual-model TEM model have been respectively developed and validated through experiments on both TEM test rigs and TEG engine test benches. These developed models are used as tools to investigate the performance of TEG, parameters sensitivity, and integration effects. Model-based TEG control, TEG cost benefit ratio and feasibility of a bifunctional TEG are also explored based on the developed models. The simulation results show that TEG power generation is highly sensitive to the heat transfer coefficient of hot side heat exchanger and thermal contact resistance. The TEG installation position is identified as the most important integration effect. It has been found by the simulation result that the fuel saving with TEG installed upstream of the three-way catalyst (TWC) is 50% higher than the fuel saving with TEG installed downstream of the TWC. The fuel saving percentage for a skutterudite vehicular TEG, which can generate around 400-600W in constant speed 120km/h, is 0.5-3.6% depending on the integration position in the exhaust line. A 3-minute faster warm-up effect of engine oil can be obtained when the bifunctional TEG works in engine warm-up mode with electrical current applied.

Transport Membrane Condenser (TMC) is an innovative technology based on the property of a nano-scale porous material which can extract both waste heat and water from exhaust gases. This technology tremendously improves the efficiency of boilers and gas/coal combustors by lowering waste heat and increasing water recovery. Contaminants in the flue gases, such as CO2, O2, NOx, and SO2 are inhibited from passing through the membrane by the membrane’s high selectivity. The condensed water through these tubes is highly pure and can be used as the makeup water for many industrial applications. The goal of this research is to investigate the heat transfer, condensation rate, pressure drop and overall performance of crossflow heat exchangers. In this research, a numerical model has been developed to predict condensation of water vapor over and inside of nano-porous layers. Both capillary condensation inside the nanoscale porous structure of the TMC and the surface condensation were considered in the proposed method using a semi-empirical model. The transport of the water vapor and the latent heat of condensation were applied in the numerical model using the pertinent mass, momentum, turbulence and energy equations. By using the proposed model and simulation procedure, the effect of various inlet parameters such as inlet mass flow rate, inlet temperature, and water vapor content of the inlet flow on the performance of the cross-flow TMC heat exchanger was studied to obtain the optimum performance of the heat exchangers at different working conditions. The performance of the TMC heat exchangers for inlet flue gas rate 40 to 120 kg/h, inlet water rate 60 to 140 kg/h, inlet flue gas relative humidity 20 to 90%, and tube pitch ratio 0.25 to 2.25 has been studied. The obtained results show that the water condensation flux continuously increases with the increase of the inlet flue-gas flow rate, water flow rate, and the flue-gas humidity. The total heat flux also follows the same trend due to the pronounced effect of the latent heat transfer from the condensation process. The water condensation flux and the overall heat transfer increase at the beginning for small values of the tube pitches and then decreases as the tube pitch increases furthermore. In addition to the cross-flow TMC heat exchangers, the performance of a shell and tube TMC heat exchanger for high pressure and temperature oxy-combustion applications has been investigated. The performance analysis for a 6-heat exchanger TMC unit shows that heat transfer of the 2-stage TMC unit is higher than the 2-stage with the same number of the heat exchanger in each unit.