8 pp. / Published July 1991; Revised May 1994

No description available.

Temperature control is widely sought after in regards to optical systems as their optical parameters often show dependence on temperature. Examples include diode lasers, multiplexing systems, optical amplifiers, and filters all of whom have a high sensitivity to temperature. This thesis presents a temperature controlled environment chamber actuated by a thermoelectric cooler. The design of which provides a simple, multi-applicable solution for temperature control in optical devices. The final device is comprised of three sub-areas of design. Each subsystem was custom built and applied in the final assembly -- including a digitally implemented signal generator, an error correction controller, and the environment chamber heat sink structure. The signal generator is used as input for a switched-mode based Peltier driver found commercially. A feedback error controller compensates the driver for temperature control. Both systems are implemented with microcontroller units. The environment chamber heat sink assembly is designed specifically to handle the thermal energy generated by the thermoelectric cooler. All of the systems were tested collectively for functionality. The input signal generator achieved its design goals and is capable of creating specific profiles in the temperature response. Error controller performance was reasonable in set-point tracking for continuous input signals. Step input responses are tuned for minimal settling time and overshoot. Temperature resolution in the thermistor response is around 0.1•C after digital filtering. The thermal design achieved its goal of operating in an ambient environment up to 54°C. Low temperature ambient environment operation has been confirmed to 8°C. / Master of Science

It is well known that the seats in a parked vehicle become very hot and uncomfortable on warm days. A new self-powered thermoelectric car seat cooler is presented to solve this problem. This study details the design and optimization of such a device. The design relates to the high level layout of the major components and their relation to each other in typical operation. Optimization is achieved through the use of the ideal thermoelectric equations to determine the best compromise between power generation and cooling performance. This design is novel in that the same thermoelectric device is utilized for both power generation and for cooling. The first step is to construct a conceptual layout of the self-powered seat cooler. Using the ideal thermoelectric equations, an analytical model of the system is developed. The model is validated against experimental data and shows good correlation. Through a non-dimensional approach, the geometric sizing of the various components is optimized. With the optimal design found, the performance is evaluated using both the ideal equations and though use of the simulation software ANSYS. The final design consists of a flat absorber plate embedded into the car seat with a thermoelectric attached to the back. A finned heat sink is used to cool the thermoelectric. The device is shown to generate enough power to provide a reasonable temperature drop in the seat. / Master of Science

With on-going developments in the field of trans-critical carbon dioxide (R-744) vapour compression cycles, a need to effectively describe the heat transfer of supercritical carbon dioxide for application in larger diameter tube-in-tube heat exchangers was identified. This study focuses on the in-tube cooling of supercritical carbon dioxide for application in the gas cooler of a trans-critical heat pump. A literature study has revealed Nusselt number correlations specifically developed for the cooling of supercritical carbon dioxide. These correlations were proven to be accurate only for certain operating conditions and tube geometries. A shortcoming identified in the reviewed literature was a generic heat transfer correlation that can be applied over a wide range of fluid conditions for supercritical carbon dioxide cooling. The objective of this study was to compare experimental data obtained from a trans-critical heat pump with different Nusselt number correlations available in literature. The experimental tube diameter used for this study (16mm), was considerably larger than the validated tube diameters used by the researchers who developed Nusselt number correlations specifically for the supercritical cooling of carbon dioxide. The experimental Reynolds number (Re) ranges (350’000 - 680’000) were very high compared to the studies found in the literature (< 300’000), due to the test section from this study forming part of a complete heat pump cycle. Experimental results showed that correlations specifically developed for supercritical carbon dioxide cooling generally over-predicts experimental Nusselt numbers (Nuexp) with an average relative error of 62% to 458% and subsequently also over-predicts the convection heat transfer coefficient. Furthermore, generic heat transfer correlations were compared to the experimental results which over-predicted the Nuexp with an average relative error between 20% and 45% over the entire Re number range. More specifically, the correlation by Dittus & Boelter (1985) correlated with an average relative error of 9% for 350’000 < Re < 550’000. From the results of this study it was concluded that cooling heat transfer of supercritical carbon dioxide in larger tube diameters at higher Re numbers is more accurately predicted by the generic Dittus & Boelter (1985) and Gnielinski (1975) correlations mainly due to the absence of thermo-physical property ratios as seen in the CO2-specific correlations. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014

With on-going developments in the field of trans-critical carbon dioxide (R-744) vapour compression cycles, a need to effectively describe the heat transfer of supercritical carbon dioxide for application in larger diameter tube-in-tube heat exchangers was identified. This study focuses on the in-tube cooling of supercritical carbon dioxide for application in the gas cooler of a trans-critical heat pump. A literature study has revealed Nusselt number correlations specifically developed for the cooling of supercritical carbon dioxide. These correlations were proven to be accurate only for certain operating conditions and tube geometries. A shortcoming identified in the reviewed literature was a generic heat transfer correlation that can be applied over a wide range of fluid conditions for supercritical carbon dioxide cooling. The objective of this study was to compare experimental data obtained from a trans-critical heat pump with different Nusselt number correlations available in literature. The experimental tube diameter used for this study (16mm), was considerably larger than the validated tube diameters used by the researchers who developed Nusselt number correlations specifically for the supercritical cooling of carbon dioxide. The experimental Reynolds number (Re) ranges (350’000 - 680’000) were very high compared to the studies found in the literature (< 300’000), due to the test section from this study forming part of a complete heat pump cycle. Experimental results showed that correlations specifically developed for supercritical carbon dioxide cooling generally over-predicts experimental Nusselt numbers (Nuexp) with an average relative error of 62% to 458% and subsequently also over-predicts the convection heat transfer coefficient. Furthermore, generic heat transfer correlations were compared to the experimental results which over-predicted the Nuexp with an average relative error between 20% and 45% over the entire Re number range. More specifically, the correlation by Dittus & Boelter (1985) correlated with an average relative error of 9% for 350’000 < Re < 550’000. From the results of this study it was concluded that cooling heat transfer of supercritical carbon dioxide in larger tube diameters at higher Re numbers is more accurately predicted by the generic Dittus & Boelter (1985) and Gnielinski (1975) correlations mainly due to the absence of thermo-physical property ratios as seen in the CO2-specific correlations. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014

Last years have become very productive for the research, construction and development of new facilities devoted to the production of beams with exotic radioisotopes (Radioactive Ion Beams, RIB). These beams are later used for experiments in fields like nuclear physics, atomic physics, astrophysics or medicine, among others. Within this kind of facilities, the ISOL facilities stand out. They are based on the on-line separation of radioactive isotopes produced in nuclear reactions between a target and a high-energy proton beam. The ISOL method was the pioneer for these facilities and it has kept up to now the leadership of RIB facilities. The main reason is ISOLDE, an ISOL facility located at CERN, the largest accelerator complex in the world, where this doctoral thesis has been carried out.The first innovation which is described is the design of an ion trap for the cooling and bunching of RIB's for ISOLDE, the so-called ISCOOL (ISOLDE COOLer). It is an Radio Frequency Quadrupole ion Cooler and Buncher (RFQCB), device based on the Paul traps. In these traps, the ions are confined in the three dimensions by electric fields. The ions are confined on the transverse plane with the pseudopotential well created by the Radio Frequency Quadrupole (RFQ) and focused on the longitudinal axis. At the same time, a gas (normally helium) fills the chamber with a pressure between 10-3 and 10-2 mbar. The collisions between the atoms or molecules of the gas and the ions. In addition, to drive the ions to the extraction of the RFQCB, an axial electric field is created by segmented electrodes. Different voltages are applied to these electrodes in order to choose the shape of the field. The shape can be chosen to create a potential well close to the extraction from the RFQCB in which the ions are accumulated and extracted as bunches, by the fast-switch of the voltages applied to the axial electrodes.The new ISCOOL will be installed as a permanent device of the ISOLDE beam lines.

¡@¡@¡@¡@¡@¡@¡@¡@¡@¡@¡@¡@¡@Abstract This paper presents an integrated batch-produced (Bi, Sb)2Te3 micro thermoelectric cooler(£g-TEC) fabricated by electrochemical MEMS technology. To optimize the thermal conductivity of (Bi, Sb)2Te3 thin layers, a cathode with tunable rotary speed has been designed in the electroplating system to well control the thin film deposition rate and uniformity.The column-type micro thermoelectric thin films fabricated using electrochemical-deposited and patterned using photolithography processes. The thermoelectric thin films made of N-type Bi2Te3 and P-type Sb2Te3 with an average thickness of 5£gm, are connected using Cr/Au layers at the hot junctions and cold junctions. The measured Seebeck coefficient and electrical resistivity of the thermoelectric thin films,are -52£gV/K and 2.52¡Ñ10-5£[m(N-type, power factor of 0.11mW/K2m),and 71£gV/K and 1.91¡Ñ10-5£[m( P-type, power factor of 0.26mW/K2m) after annealing at 250¢J.Under the circumstances that voltage of 2-5 volts is driven, the upper and lower levels electrode shows tentatively that there is 0.7¢Jof difference in temperature.

This paper presents an integrated column-type micro thermoelectric cooler (£g-TEC) constructed with serial connected p-type antimony-tellurium (Sb2Te3) and n-type bismuth-tellurium (Bi2Te3) micro pillars deposited by electrochemical deposited technology. To optimize the power factor, density and uniformity of the TE films and to enhance the reproducibility of £g-TEC device, a cathode with tunable rotary speed and with accurate current controller has been designed in the electroplating system of this research. The electroplating deposited Bi2Te3 and Sb2Te3 with an average thickness of 8 £gm, are connected using Cr/Au layers at the hot junctions and cold junctions. The measured Seebeck coefficient and electrical resistivity are -86 £gV/K and 16 £g£[-m for Bi2Te3 films after annealed at 250¢XC, and are 68 £gV/K and 30 £g£[-m for Sb2Te3 films after annealed at 200¢XC. The optimized power factors of the n-type (2.64¡Ñ10-4 W/K2m) and p-type (2.64¡Ñ10-4 W/K2m) telluride compounds have been demonstrated in this paper. Under 5 volts driven, the integrated £g-TEC device shows average cooling achieved is about 1.3 ¢XC.

Orientador: Frederico Ozanam Papa / Resumo: O pênis é o órgão copulador e no garanhão é classificado como sendo músculo cavernoso, em que os espaços cavernosos são preenchidos de sangue durante a ereção. Nos testículos que ocorre a produção espermática, que são transportados pela rete testis até o epidídimo, onde sofrerão maturação, capacidade fertilizante e armazenados até a ejaculação. As glândulas sexuais acessórias são responsáveis pelos fluidos expelidos durante a ejaculação, denominado de plasma seminal, que se misturam às células espermáticas e formam o ejaculado. Cada uma dessas glândulas são responsáveis por uma determinada secreção que vai direcionar o ejaculado equino a ser dividido em três distintas frações: fração pré-espermática, produzida pelas glândulas bulbouretrais e próstata; fração rica em espermatozoides, produzida pelas secreções do epidídimo e por líquidos das ampolas dos ductos deferentes; fração pós-espermática ou fração pobre, formada por espermatozoides remanescentes no canal uretral e líquidos produzidos pelas vesículas seminais, o gel. Durante o processo fisiológico de cópula, ocorrem vários eventos denominados de ereção, em que o garanhão se excita por estímulos, emissão que caracteriza-se pela liberação de espermatozoides dentro da uretra pélvica, seguido da ejaculação com a expulsão do sêmen, o relaxamento e recolhimento do pênis. Normalmente, as colheitas de sêmen equino são realizadas de forma convencional, com vagina artificial fechada, em que todas as frações se misturam. Cada garanh... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The penis is the copulatory organ and in the stallion it is classified as cavernous muscle and the cavernous spaces are filled with blood during erection. In the testicles occurs sperm production, that are transported through the rete testis to the epididymis, where they will suffer maturation, fertilizer capacity and will be stored until ejaculation. The accessory sex glands are responsible for the expelled fluids during ejaculation, named seminal plasma that are mixed with sperm cells and form the ejaculate. Each of these glands are responsible for a certain secretion that will divide equine semen into three distinct fractions: pre-sperm fraction, produced by the prostate and bulbourethral glands; rich fraction in sperm, produced by epididymal secretions and liquids from ampoules of the vas deferens; post-sperm fraction or poor fraction, consisting of sperm remaining in the urethral canal and liquids produced by the seminal vesicles, the gel. During the physiological process of mating, several events occur named erection, in which the stud is excited by stimuli emission which is characterized by the release of sperm into the pelvic urethra followed by ejaculation with the expulsion of semen, relaxation and gathering the penis. Typically, horse semen collections are performed in the conventional way, with a closed artificial vagina, where all the fractions are mixed. Each stud has individual characteristics related to the maintenance of sperm cells during the cryopreservatio... (Complete abstract click electronic access below) / Mestre