Sweden’s energy consumption is divided into three major sectors. One of them is the industry sector. One third of Sweden’s energy consumption is converted in the industries. The chemical industry is one of those industries with great energy needs. This thesis looks into energy efficiency in industry, in particular the plastics manufacturing industry. Efficiency concerning heat exchangers, their fouling resistance and also pumps. This thesis also relates to the industry in the big picture as heat exchangers and pumps are widely used and these has a great energy and environmental efficiency. This thesis presents an algorithm especially developed for this issue. The thesis has been written by dividing the work into measurements and data, implementation and analysis. The result of this thesis is an Excel-sheet that may be used to calculate the fouling resistance in a plate heat exchanger. / Sveriges energianvändning är uppdelad i tre stora sektorer. Ett av dem är industrin. En tredjedel av Sveriges energiförbrukning omvandlas inom industrierna. Kemiindustrin är av dem industrier som har stort energibehov. Detta examensarbete tar upp effektivisering inom industrin, närmre sett plasttillverkningsindustrin. Effektiviseringen berör värmeväxlare och dess foulingresistans och även pumpar. Examensarbetet kan spegla industrin i den stora bilden då värmeväxlare och pumpar finns väldigt utspritt och effektiviseras dessa har en stor energi och miljöeffektivisering gjorts. För att energieffektivisera inom detta examensarbete har en beräkningsalgoritm tagits fram. Arbetet har delats upp i mätvärden, beräkningar genomförande och analys. Resultatet blev en Excel-ark som kan användas för att beräkna foulingresistansen i en plattvärmeväxlare.

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

The goal of this research was to design, build and test a small burner and heat exchanger system that could be used as a source of heat for thermoelectric modules (TEMs) for the purpose of generating portable electric power for soldiers in the field. The project was conducted as a subcontract to Marlow Industries Inc. which was under contract from the U.S. Army. The scale of the burner thermal output was to be in the approximate range of 2 kW of heat production and it was to be able to operate on a liquid fuel, specifically JP8. The first burner investigated was a custom burner designed and built at UT. It was tested with various fuel and air delivery systems. Different methods to start it, with the goal of developing an electrical starting system, were also investigated. It was capable of operating at outputs over 1 kW, but was difficult to start reliably and fuel vaporization characteristics were sensitive to operating conditions. Two commercial burners were also studied, each with somewhat different designs. One of those burners, manufactured by MSR, was chosen to be further tested in conjunction with a heat exchanger and thermoelectric modules. The performance of the thermoelectric modules used in this study was determined to be very dependent on an attached resistive load, with a peak power output occurring at approximately 3 ohms. Power output was also determined to increase linearly with increasing temperature difference between the hot and cold sides of the module. Power output followed similar trends as open circuit voltage. The temperatures of the heat exchanger across its width were very uniform, but the accuracy in centering the heat exchanger over the burner could significantly affect temperatures. The time to reach steady state temperatures was relatively insensitive to the length of the heat exchanger. The presence of attached thermoelectric modules reduced the temperature of the heat exchangers and exhaust gas slightly. Reducing the heat exchanger length resulted in higher metal temperatures. Without cooling the cold side of the thermoelectric modules, performance increased while the system was heating up, but then dropped after reaching a peak. Cold side cooling improved thermoelectric performance by increasing its temperature difference. Active cooling with a blower and heat sink provided even better performance than passive cooling using just a heat sink at the expense of a larger parasitic load. The TEMs on the 5 inch long heat exchanger could generate 6.32 W with passive cooling, but active cooling would produce no net power. The 11 inch long heat exchanger could generate 12.8 W with passive cooling, and 16 W net could be generated with active cooling. A heat exchanger efficiency calculation showed that the 16, 11 and 5 inch long heat exchangers were about 94.4%, 93.4%, and 90.7% efficient respectively. This efficiency was defined as the ratio of the heat transferred to the heat exchanger to the heat released in the flame. / text

The present study has focused on the use of coil heat exchangers (CHEs) with microencapsulated phase change material (MPCM) slurries to understand if CHEs can yield greater rates of heat transfer. An experimental study was conducted using a counterflow CHE consisting of 3 helical coils. Two separate tests were conducted, one where water was used as heat transfer fluid (HTF) on the coil and shell sides, respectively; while the second one made use of MPCM slurry and water on the coil and shell sides, respectively. The NTU-effectiveness relationship of the CHE when MPCM fluid is used approaches that of a heat exchanger with a heat capacity ratio of zero. The heat transfer results have shown that when using a MPCM slurry, an increase in heat transfer rate can be obtained when compared to heat transfer results obtained using straight heat transfer sections. It has been concluded that the increased specific heat of the slurry as well as the fluid dynamics in helical coil pipes are the main contributors to the increased heat transfer.

The development of high temperature heat exchangers will play a vital part in the success of High Temperature Nuclear Reactors (HTRs). Manufacturing such heat exchangers from metals is becoming increasingly difficult as the operating temperatures keep rising. Above 1000'C most metals loose their strength and have high creep rates, while certain ceramic materials (including graphite, in the absence of oxygen) are able to operate at these temperatures. A literature study was done in order to identify the major problems regarding the use of graphite for heat exchanger construction as well as to investigate to what extent graphite has been used for heat exchanger construction in the past. Following from the literature survey, it was decided to design and manufacture a Printed Circuit Heat Exchanger (PCHE) from isotropic graphite to gain experience regarding the use of graphite as a heat exchanger material. This heat exchanger was then tested in order to learn about the operation of a graphite heat exchanger and to determine its effectiveness. A model ofthe heat exchanger was also constructed in order to determine what the performance of such a heat exchanger should theoretically be. It was found that the single greatest hurdle standing in the way ofgraphite being used as a heat exchanger material is its high gas permeability. This causes mixing between the two fluid streams as well as leakages to the environment, which have a negative effect on the heat exchanger's heat transfer capability. The methods used to establish a seal between the consecutive plates of the PCHE are also affected by the permeability of the graphite. Coatings on the surface of the graphite might be able to reduce its permeability and can also inhibit the high temperature degradation of graphite in the presence of oxygen. Manufacturing very small flow channels for the PCHE is limited by the availability of small enough end mills. Alternative manufucturing techniques is needed to economically construct a graphite PCHE. It was also found that the heat transfer effectiveness of the heat exchanger is influenced negatively by heat losses to the environment through the outer surface ofthe heat exchanger. Effective insulation around the heat exchanger or a graphite material :vith higher heat conductivity perpendicular to the flow direction might solve this problem. This study concluded that if diffusion bonding techniques, effective coatings and a graphite material with increased heat conductivity perpendicular to the flow direction are used, manufacturing a printed circuit heat exchanger from graphite is feasible. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2010

This thesis examines the development of a high efficiency heat pump system using thermoelectric (TE) and reticulated metal foam (RMF) technologies to power a vehicle`s battery thermal management system. The focus is split into two areas: first a review of TE???s sourcing or removing heat, second an examination of compact heat exchanger (HX) design. Five TE suppliers were investigated to understand the performance and limitations of their TE modules. Testing showed the Kyrotherm product to be superior so it was used as a design basis. RMF???s are known to be an effective means to improve the performance of compact heat exchangers, thus HX???s were evaluated with RMF foams compressed to varying densities in order to understand their potential in conjunction with thermoelectric devices. Experimental results showed performance was limited due to adequate bonding, yet still on par with the highest efficiency technologies currently on the market.

The development of high temperature heat exchangers will play a vital part in the success of High Temperature Nuclear Reactors (HTRs). Manufacturing such heat exchangers from metals is becoming increasingly difficult as the operating temperatures keep rising. Above 1000'C most metals loose their strength and have high creep rates, while certain ceramic materials (including graphite, in the absence of oxygen) are able to operate at these temperatures. A literature study was done in order to identify the major problems regarding the use of graphite for heat exchanger construction as well as to investigate to what extent graphite has been used for heat exchanger construction in the past. Following from the literature survey, it was decided to design and manufacture a Printed Circuit Heat Exchanger (PCHE) from isotropic graphite to gain experience regarding the use of graphite as a heat exchanger material. This heat exchanger was then tested in order to learn about the operation of a graphite heat exchanger and to determine its effectiveness. A model ofthe heat exchanger was also constructed in order to determine what the performance of such a heat exchanger should theoretically be. It was found that the single greatest hurdle standing in the way ofgraphite being used as a heat exchanger material is its high gas permeability. This causes mixing between the two fluid streams as well as leakages to the environment, which have a negative effect on the heat exchanger's heat transfer capability. The methods used to establish a seal between the consecutive plates of the PCHE are also affected by the permeability of the graphite. Coatings on the surface of the graphite might be able to reduce its permeability and can also inhibit the high temperature degradation of graphite in the presence of oxygen. Manufacturing very small flow channels for the PCHE is limited by the availability of small enough end mills. Alternative manufucturing techniques is needed to economically construct a graphite PCHE. It was also found that the heat transfer effectiveness of the heat exchanger is influenced negatively by heat losses to the environment through the outer surface ofthe heat exchanger. Effective insulation around the heat exchanger or a graphite material :vith higher heat conductivity perpendicular to the flow direction might solve this problem. This study concluded that if diffusion bonding techniques, effective coatings and a graphite material with increased heat conductivity perpendicular to the flow direction are used, manufacturing a printed circuit heat exchanger from graphite is feasible. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2010

abstract: While much effort in Stirling engine development is placed on making the high-temperature region of the Stirling engine warmer, this research explores methods to lower the temperature of the cold region by improving heat transfer in the cooler. This paper presents heat transfer coefficients obtained for a Stirling engine heat exchanger with oscillatory flow. The effects of oscillating frequency and input heat rate on the heat transfer coefficients are evaluated and details on the design and development of the heat exchanger test apparatus are also explained. Featured results include the relationship between overall heat transfer coefficients and oscillation frequency which increase from 21.5 to 46.1 Wm-2K-1 as the oscillation frequency increases from 6.0 to 19.3 Hz. A correlation for the Nusselt number on the inside of the heat exchange tubes in oscillatory flow is presented in a concise, dimensionless form in terms of the kinetic Reynolds number as a result of a statistical analysis. The test apparatus design is proven to be successful throughout its implementation due to the usefulness of data and clear trends observed. The author is not aware of any other publicly-available research on a Stirling engine cooler to the extent presented in this paper. Therefore, the present results are analyzed on a part-by-part basis and compared to segments of other research; however, strong correlations with data from other studies are not expected. The data presented in this paper are part of a continuing effort to better understand heat transfer properties in Stirling engines as well as other oscillating flow applications. / Dissertation/Thesis / M.S. Mechanical Engineering 2011

The operation of large industrial scale combustion systems, such as furnaces and boilers is increasingly dictated by emission legislation and requirements for improved efficiency. However, it can be exceedingly difficult and time consuming to gather the information required to improve original designs. Mathematical modelling techniques have led to the development of sophisticated furnace representations that are capable of representing combustion parameters. Whilst such data is ideal for design purposes, the current power of computing systems tends to generate simulation times that are too great to embed the models into online control strategies. The work presented in this thesis offers the possibility of replacing such mathematical models with suitably trained Artificial Neural Networks (ANNs) since they can compute the same outputs at a fraction of the model's speed, suggesting they could provide an ideal alternative in online control strategies. Furthermore, artificial neural networks have the ability to approximate and extrapolate making them extremely robust when encountering conditions not met previously. In addition to improving operational procedures, another approach to increasing furnace system efficiency is to minimise the waste heat energy produced during the combustion process. One very successful method involves the implementation of a heat exchanger system in the exiting gas flue stream, since this is predominantly the main source of heat loss. It can be exceptionally difficult to determine which heat exchanger is best suited for a particular application and it can prove an even more arduous task to control it effectively. Furthermore, there are many factors that alter the performance characteristics of a heat exchanger throughout the duration of its operational life, such as fouling or unexpected systematic faults. This thesis investigates the modelling of an experimental heat exchanger system via artificial neural networks with a view to aiding the design and selection process. Moreover, the work presented offers a means to control heat exchangers subject to varying operating conditions more effectively, thus promoting savings in both waste energy and time.