Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates

O estudo teve como objetivo analisar o desempenho dos serviços de saúde que executam a Terapia Diretamente Observada (DOT) no domicílio para o controle da tuberculose. Foram estudados quatro Programas de Controle da Tuberculose nomeados como A, B, C e D a partir dos seguintes indicadores: aproveitamento dos recursos; agilidade do desempenho; monitoração da administração da medicação; tempo gasto por visita domiciliar. Os dados foram coletados durante a visita a 47 doentes em DOT no domicílio. Observou-se que o aproveitamento dos recursos foi maior no programa B (91,3%); maior agilidade (5,8) e maior porcentagem de visitas com monitoração da administração da medicação (77,4%) no programa A; maior tempo gasto por visita no programa C (14,7 minutos) e menor no programa A (10,4 minutos). O maior ou menor desempenho expressa numericamente a forma como os recursos estão sendo utilizados e se a observação da ingestão medicamentosa está sendo alcançada.La finalidad del estudio fue analizar el desempeño de los servicios de salud que brindan Tratamientos por observación en domicilio para el control de la tuberculosis. Se estudiaron cuatro Programas de Controle da Tuberculosis identificados como A, B, C y D a partir de los indicadores de Aprovechamiento de recursos; Agilidad en el desempeño; Supervisión de la administración del medicamento y Tiempo utilizado por visita domiciliaria. Los datos fueron recolectados durante la visita a 47 enfermos. Se observó que el aprovechamiento de recursos fue mayor en el programa B (91,3%); en el programa A fue observada mayor agilidad (5,8) y mayor porcentaje de visitas con supervisión en la administración del medicamento (77,4%); en el programa C fue mayor el tiempo utilizado por visita (14,7 minutos), siendo este menor para el programa A (10,4 minutos). El mayor o menor desempeño expresa numéricamente la forma cómo los recursos están siendo utilizados, así como el alcance de las metas al respecto de la observación durante la ingestión de medicamentos.The study had the objective to analyze the performance of the health services that implement the Directly Observed Therapy at home for tuberculosis control. This study analyzed four Tuberculosis Control Programs, referred to as A, B, C, and D, using the following indicators: Resource use; Performance quickness; Monitoring medication administration; Time spent per home visit. Data were collected during visits to 47 patients receiving DOT at home. Resource use was higher in program B (91.3%); program A showed quicker performance (5.8) and more visits during which medication administration was monitored (77.4%); program C had the longest time spent per home visit (14.7 minutes) and program A the shortest (10.4 minutes). The best or worst performance numerically expresses how resources are being used and whether the observation of medication intake is being achieved

Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates

<jats:title>Abstract</jats:title><jats:p>Previous studies optimized the dimensions of coaxial heat exchangers using constant mass flow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar flow types. In contrast, in this study, flow conditions in the circular ring are kept constant (a set of fixed Reynolds numbers) during optimization. This approach ensures fixed flow conditions and prevents inappropriately high or low mass flow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic effort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass flow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellström’s borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefficients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy difference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy flux and hydraulic effort. The Reynolds number in the circular ring is instead of the mass flow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54% of the outer pipe radius for laminar flow and 60% for turbulent flow scenarios. Net-exergetic optimization shows a predominant influence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth’s thermal properties and the flow type. Conclusively, coaxial geothermal probes’ design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics.</jats:p&gt