A heat exchanger is a device used to transfer thermal energy between two or more fluids, at different temperatures in thermal contact. They are widely used in aerospace, chemical industries, power plants, refineries, HVAC refrigeration, and in many industries. The optimal design and efficient operation of the heat exchanger and heat transfer network plays an important role in industry in improving efficiencies and to reduce production cost and energy consumption. In this paper, significance of shape of inner pipe of double pipe heat exchanger was analyzed with respect to triangular, hexagonal and octagonal shaped inner pipes. The performance of double pipe heat exchangers was investigated with and without dent pattern using CFD analysis in ANSYS and efficient heat transfer results are identified from CFD outputs. On basis of literature review, few factors influencing the efficiency of heat exchanger and method to improve the efficiency are discussed.

The mechanical and thermal properties of natural short latania fiber (SLF)-reinforced poly(propylene)/ethylene-propylene-diene-monomer (SLF/PP/EPDM) bio-composites reinforced with nano-clays (NCs), pistachio shell powders (PSPs), and/or date seed particles (DSPs) were studied using experiments and machine learning (ML) predictions. This dissertation embraces three related investigations: (1) an assessment of maleated polypropylene (MAPP) coupling agent on mechanical and thermal behavior of SLF/PP/EPDM composites, (2) heat deflection temperature (HDT) of bio-nano-composites using experiments and ML predictions, and (3) fracture toughness ML predictions of short fiber, nano- and micro-particle reinforced composites. The first project (Chapter 2) investigates the influence of MAPP on tensile, bending, Charpy impact and HDT of SLF/PP/EPDM composites containing various SLF contents. The second project (Chapter 3) introduces two new bio-powderditives (DSP and PSP) and characterizes the HDT of PP/EPDM composites using experiments and K-Nearest Neighbor Regressor (KNNR) ML predictions. The composites contain various contents of SLF (0, 5, 10, 20, and 30wt%), NCs (0, 1, 3, 5wt%), micro-sized PSPs (0, 1, 3, 5wt%) and micro-sized DSPs (0, 1, 3, 5wt%). The third project (Chapter 4) characterizes the fracture toughness of the same composite series used in the second project, by applying Charpy impact tests, finite element analysis, and a ML approach using the Decision Tree Regressor (DTR) and Adaptive Boosting Regressor (ABR). 2wt% MAPP addition enhanced the composite tensile/flexural moduli and strength up to 9% compared with the composites with zero MAPP. In addition, energy impact absorption was profoundly increased (up to78%) and HDT (up to 4 Co) was improved upon MAPP addition to the composites. SLF, NC, DSP and PSP could separately and conjointly increase HDT and fracture toughness values. The KNNR ML approach could accurately predict the composite’s HDT values and, Decision Tree Regressor (DTR) and Adaptive Boosting Regressor ML algorithms worked well with fracture toughness predictions. Pictures taken through a transmission electron microscope, scanning electron microscope and X-Ray proved the NC dispersion and exfoliation as one of the factors in HDT and fracture toughness improvements.

<p> Flexible manufacturing systems and lean production philosophies are in increasing industrial demand. Multiple manufacturing processes integrated into stand alone automated equipment can be utilized to greatly reduce operation costs. New technologies are continually being developed that can be easily combined with related manufacturing processes. Flexible machining and surface hardening operations can be realized in a single set-up by integrating a high-power diode laser (HPDL) within a machine tool structure.</p> <p> The following research presents the concept of integrated laser surface hardening within a machine tool environment. Experimental work was performed using a HPDL for transformation hardening of AISI 4140 steel.</p> <p> Both quasi-steady analytical and transient finite element heat transfer models have been developed. Solutions of the models are compared, which show that the more sophisticated finite element modeling is necessary only if accuracy of peak surface temperature is important. Otherwise, the simpler but faster analytical model can be used to describe the temperature profiles during laser heating.</p> <p> A novel approach using temperature indicating lacquers was shown to be a simple and reliable tool for temperature measurement. The analytical model was further used to find a best fit with the experimental measurements to estimate the fraction of laser power absorbed by the workpiece surface. With the aid of the model, it was shown that the austenite transformation temperature is highly dependent on the scanning speed. For slower speeds, the transform temperature was closer to the A3 temperature given by the iron-iron carbide phase diagram. Tests performed at faster scanning speeds indicated transformation temperatures as high as 1230 °C.</p> <p> Experiments were divided into three series. The first series was performed at slow scanning speeds (200-1000 mm/min) and low laser powers (200-500 W). Hardening was executed on flat workpieces with the laser scanning along a linear path. The second and third test series were performed at fast scanning speeds (2000-8000 mm/min) and higher laser powers (1000-2000 W) with hardening done on rotating cylindrical workpieces. The third tests series consisted of two laser passes in an attempt to increase the penetration depth of the hardened layer. These tests resulted in severe distortion due to melting that would require nearly the entire hardened layer to be machined away post heat treatment. However, if the melting temperature is not significantly exceeded multiple laser passes could be used to increase the thickness of the hardened layer.</p> <p> Higher case depths were realized for the slow tests since these tests have a greater laser-work interaction time. During laser treatment, the uncoated workpieces were left exposed to allow for oxidation and melting in order to increase the fraction of absorbed laser power. The absorptivity is shown to be as high as 85% for these tests.</p> <p> Results are presented in a form useful in selection of laser power and scanning speed to obtain the desired level of hardening, without having to resort to complex analytical or numerical models. Investigations into in-process monitoring show that measurement of surface temperature using an infrared thermometer could be used to control the generated hardened layer reducing process scrap.</p> / Thesis / Master of Applied Science (MASc)

Silicon Carbide (SiC) has the potential to significantly improve electronics. As a material, it can conduct heat better, carry larger currents and can give faster responses compared to today’s technologies. One way to produce SiC for use in electronics is by growing a thin layer in a CVD-reactor (chemical vapour deposition). A CVD-reactor leads a carrier gas with small parts of active gas into a heated chamber (susceptor). The gas is then rapidly heated to high temperatures and chemical reactions occur. These new chemical substances can then deposit on the substrate surface and grow a SiC layer. This thesis investigates the effect of different opening angles on a susceptor inlet in a SiC horizontal hot-walled CVD-reactor at Linköping University. The susceptor inlet affects both the flow and heat transfer and therefore has an impact on the conditions over the substrate. A fast temperature rise in the gas as close to the substrate as possible is desired. Even temperaturegradients vertically over the substrate and laminar flow is desired. The CVD-reactor is modeled with conjugate heat transfer using CFD simulations for three different angles of the inlet. The results show that the opening angle mainly affects the temperature gradient over the substrate and that a wider opening angle will cause a greater gradient. The opening angle will have little effect on the temperature of the satellite and substrate.

A probe for measuring the specific heat of superconductors at low temperatures and in high magnetic fields has been built and commissioned. The probe has been tested using the relaxation method on samples of copper and the accuracy of the data is 1.3 % between 5 K and 30 K, data taken using the long range pulse method has a resolution of 10 mK. Specific heat measurements have been performed on members of the series (Pb(_1)-(_x))Cu(_1.8x)Mo(_6)S(_8), (Sn(_1-x))Eu(_x)Mo(_6)S(_8) and (Pb(_1-x)M(_x))Mo(_6)S(_8) where M = Gd and Eu, from 3 K up to 30 K and in magnetic fields up to 15 T. Additional results from resistivity, susceptibility, magnetisation. X-ray diffraction, transmission electron microscopy and electron dispersive-ray measurements are also presented. These data have been compared to results from other authors and are analysed in terms of the BCS and GLAG theories of superconductivity and the magnetic properties of these materials. The mean field model has been used to calculate numerically the magnetic contribution to the specific heat (cm) of both ferromagnetic and antiferromagnetic systems as a function of temperature and applied field both above and below the ordering temperature. In addition an approximate analytic form for the magnetisation has been used to calculate Cm above the ordering temperature. Expressions have been derived for the saturation value of the peak in C(_m): C(^sat)(_m) = 1.1245n(_cell)RJI(J+1) and the temperature dependence of the peak with applied field ȡ(μ(_o)H(_ext))/ȡT(_peak)=6.540/g(_J)(J+1). They allow the simple calculation of the values of J and g(_J)(J + 1) from specific heat data. The magnetic contribution to the specific heat of the samples (Sn(_0.65)Eu(0.35)Mo(_6)S(_8)) and (Sn(0.50)Eu(_0.50)Mo(_6)S(_8)) have been modelled using these calculations and excellent agreement is found by considering the magnetic ions as free ions. The sample is accurately modelled by including an additional minority phase (Gd(_2)S(_3)). The approximate expressions have also been used to analyse data on high temperature superconductors producing values of J and g(_J)}{J + 1) consistent with a doublet ground state. The properties of Chevrel phase materials have been determined as a function of doping level. The critical temperature is degraded by doping but an increase in the critical current density is observed in the series (Pb(_1-x)Cu(_1-8x)Mo(_6)S(_8) for very low levels of doping. Increases of up to 28 % in the upper critical field, that are probably due to the compensation effect and an increase in the normal state resistivity, are also observed in the series (Sn(_1-x)Eu(_x)Mo(_6)S(_8)) at high levels of doping and in the series (Pb(_1-x)Gd(_x)Mo(_6)s(_8) for low levels of doping.

ABSTRACT THE EFFECTS OF TEXTBOOK STYLE AND READING STRATEGY ON STUDENTS&rsquo / ACHIEVEMENTS AND ATTITUDES TOWARDS HEAT AND TEMPERATURE Aky&uuml / z, Volkan M.S., Department of Secondary Science and Mathematics Education Supervisor: Assist. Prof. Dr. Ali Eryilmaz July 2004, 96 pages The aim of this study is to investigate the effect of textbook style and reading strategy on 9th grade students&rsquo / achievement and attitude towards heat and temperature at Eregli district of Zonguldak. Textbook style was means that whether textbook written in conceptual style or traditional style. The reading strategy was taken as K-W-L vs. reading without K-W-L. The study uses factorial design to investigate partial and combined effects of these methodologies. In the study convenience sampling was used. The participants were 123 9th grade students at Zonguldak Eregli Super High School in four different classes. Then selected classes were randomly assigned into four groups. The groups were conceptual physics text with K-W-L reading strategy, conceptual physics text with reading without K-W-L, traditional physics text with K-W-L reading strategy and traditional physics text with reading without K-W-L. Achievement and attitude tests were administered before and after the treatment. The data was analyzed by Multiple Analysis of Covariance (MANCOVA) to find out individual and combined effects of conceptual physics texts and K-W-L reading strategy. The results has shown that conceptual physics texts were effective in increasing students&rsquo / attitude, K-W-L was effective in increasing achievement, and their combination was effective in increasing both achievement and attitude of the students.

Tato diplomová práce se zabývá předehřevem spalovacího vzduchu a jeho vlivem na parametry spalovacího procesu. V teoretické části je zpracován přehled nejčastějších znečišťujících látek z průmyslového spalování. Je popsána aktuálně platná relevantní legislativa v Evropské unii a jsou porovnány její implementace do národní legislativy v České republice a v Německu. Dále je provedena klasifikace hořáků z hlediska různých kritérií a rešerše předchozí práce v oblasti předehřevu spalovacího vzduchu. Na zkušebně hořáků byla provedena experimentální studie dvou různých hořáků na zemní plyn při konstantním tepelném příkonu 750 kW se spalovacím vzduchem předehřátým až na 250 °C. Výsledky odhalily pozitivní vliv předehřevu na účinnost spalování. Množství emisí NOx a CO naopak rostlo s teplotou spalovacího vzduchu.

The main goal of doctoral thesis is optimization cooling of the synchronous machine. Problem is solved based on the finite element method with use of ANSYS software. Work is built up from theoretical part where is comparison of base equations for heat transfer and simulations for several models. Next part shows us two methods how simulate free and force convection. Depends on the better method from the previous two methods is used for next calculations with several algorithm which are used for find of best parameters for synchronous machine. Our control parameter is mass flow rate.

In this article a Novikov engine with fluctuating hot heat bath temperature is presented. Based on this model, the performance measure maximum expected power as well as the corresponding efficiency and entropy production rate is investigated for four different stationary distributions: continuous uniform, normal, triangle, quadratic, and Pareto. It is found that the performance measures increase monotonously with increasing expectation value and increasing standard deviation of the distributions. Additionally, we show that the distribution has only little influence on the performance measures for small standard deviations. For larger values of the standard deviation, the performance measures in the case of the Pareto distribution are significantly different compared to the other distributions. These observations are explained by a comparison of the Taylor expansions in terms of the distributions’ standard deviations. For the considered symmetric distributions, an extension of the well known Curzon–Ahlborn efficiency to a stochastic Novikov engine is given.

This diploma thesis is about thermomechanics of passenger car tires. The research part dealing with existing tire models is followed by the practical part. The practical part is based on the designs of thermomechanical models. The first model determines a dependence of temperature on the air pressure inside a tire when a temperature changes. The second thermomechanical model captures all the heat fluxes which affect a tire while a vehicle is in motion. The third thermomechanical model calculates temperatures of parts of the tire during driving tests. All models are programmed in MATLAB.