Multi-objective optimization of a novel reversible High-Temperature Heat Pump-Organic Rankine Cycle (HTHP-ORC) for industrial low-grade waste heat recovery

Nowadays, a high amount of industrial thermal energy is still lost due to the lack of competitive solutions for energy revalorization. Facing this challenge, this paper presents a novel technology, based on a reversible High-Temperature Heat Pump (HTHP) and Organic Rankine Cycle (ORC). The proposed system recovers low-grade waste heat to generate electricity or useful heat in accordance with consumer demand. Compressor and expander semi-empirical models have been considered for the reversible system computational simulation, being HFC-245fa the working fluid selected. The built-in volume ratio and Internal Heat Exchanger (IHX) effectiveness have been optimized to reach the maximum energy efficiency in each operating condition. Although HFC-245fa exhibits energy performance attributes, its high Global Warming Potential (GWP) is an issue for climate change mitigation. Hence, multi-objective optimisation of the environmentally friendly working fluids Butane, Pentane, HFO-1336mzz(Z), R-514A, HCFO-1233zd(E) and HCFO-1224yd(Z) has been carried out. The results show that the system proposed, working with HFC-245fa, achieves a Coefficient of Performance (COP) of 2.44 for condensing temperature of 140 °C, operating in HTHP mode, whereas the ORC mode provides a net electrical efficiency of 8.7% at condensing temperature of 40 °C. Besides, HCFO-1233zd(E) and HCFO-1224yd(Z) are both appropriate alternatives for the HFC-245fa replacement. These working fluids provide a COP improvement of 9.7% and 5.8% and electrical net efficiency improvement of 2.1% and 0.8%, respectively, compared to HFC-245fa. This paper provides a reference study for further designs and developments of reversible HTHP-ORC systems used for industrial low-grade waste heat recovery

Micro-generation and micro combined heat and power generation using “free” low temperature heat sources through Organic Rankine Cycles

Ponencia presentada en International Conference on Renewable Energies and Power Quality (ICREPQ’13) celebrada en Bilbao del 20 al 22 de marzo de 2013.The Organic Rankine Cycle (ORC) technology is an efficient way for small-scale generation. It offers great benefits from low temperature heat sources, recovering waste heat and revaluing renewable thermal energy. This paper presents the use of ORC for power and combined heat and power generation from low temperature heat sources. Specifically, two recent applications successfully implemented in Spain are reported, based on Rank® technology: a micro generation for waste heat recovery in a ceramic industry using HT-20 kWe and a micro combined heat and power generation using solar heat with HT-C 5 kWe. Experimental data have been evaluated to check economical and technical ORC feasibility. From waste heat recovery, now up to 23 kWe are generated, 336 MWt of primary energy are saved and 44 tonnes of CO2 emissions are avoided, with a suitable payback lower than 5 years. From renewable thermal energy, now 37 MWt of primary energy are saved, 5 tonnes of CO2 emissions are avoided with a payback lower than 8 years

Experimental study of an Organic Rankine Cycle with HFO-1336mzz-Z as a low global warming potential working fluid for micro-scale low temperature applications

An experimental evaluation of HFO-1336mzz-Z as a low global warming potential working fluid for ORC systems in micro-scale low temperature applications has been conducted. The energy performance in a fully monitored ORC module has been analyzed varying the heat source temperatures between 140 °C and 160 °C and heat sink temperatures between 25 °C and 40 °C. The ORC module uses a regenerative configuration allowing heat recovery not only from the heat source but also from the expanded vapor, thus improving the cycle thermal and electrical efficiency. The maximum gross electrical power generated was 1100 W, while the net electrical efficiency ranged from 5.5% to 8.3%. The volumetric expander performance was analyzed by means of the filling factor, while deviations of expander operation from ideal performance were evaluated by means of the isentropic and overall expander-generator efficiency. Net electrical efficiency, isentropic expander efficiency and volumetric expander performance obtained with HFO-1336mzz-Z in this work are higher than those obtained with HFC-245fa in a previous work using the same experimental facility

Experimental evaluation of system modifications to increase R1234ze(E) cooling capacity

The GWP limitations are being progressively introduced in Europe through Regulation EU No 517/201, phasing out R134a in most of its refrigeration and air conditioning applications. Pure hydrofluoroolefins are proposed to substitute this fluid, however generally system modifications are needed to achieve a good performance. In the case of R1234ze(E), the cooling capacity is always much below that of R134a in drop-in or light retrofit substitutions. This work performs an experimental comparison using R1234ze(E) and R134a under different refrigeration operating conditions. R1234ze(E) is tested considering the use or not of an internal heat exchanger, and R134a at the same or lower compressor rotation speed. Results show that the use of R1234ze(E) with an open-type compressor 43% larger and an internal heat exchanger of 25% effectiveness, leads to a cooling capacity augmentation, enough to reach R134a cooling capacity in the different conditions tested. For R450A, it is sufficient only with the IHX activation

Development and validation of a scale to assess social entrepreneurship competency in Higher Education

This paper proposes an instrument to assess social entrepreneurship competency in higher education (SECS). 19 Features of social entrepreneurship competency were identified. The pilot test (n = 497) confirmed the validity and reliability of the SECS. Exploratory factor analysis proposed a set of categories consistent with the initial approach. Confirmatory factor analysis showed acceptable relationships among the scale categories and items, while the fit indices suggested that the data fit adequately to the default model. Pearson's test verified significant, positive correlations among the revised categories in all cases. Therefore, the scale carries the potential to contribute to social entrepreneurship research

Experimental evaluation of HCFO-1233zd-e as HFC-245fa replacement in an organic rankine cycle system for low temperature heat sources

[EN] In this work an experimental evaluation of the working fluid HCFO-1233zd-E as HFC-245fa replacement in ORC systems for low temperature heat sources has been conducted. A fully monitored ORC module has been used to test both working fluids at different operating conditions. Due to the different densities of the working fluids, the mass flow rate for HCFO-1233zd-E is approximately 20% lower than for HFC-245fa. This causes thermal and electrical powers to be lower for HCF0-1233zd-E than for HFC245fa. However, net electrical efficiency is similar for both working fluids, ranging from 5% to 9.7% in the tested operating conditions. Regarding the expander performance, various performance indicators are addressed. The expander isentropic performance has a maximum value of 75%, with higher values for HCFO-1233zd-E than for HFC-245fa. The overall efficiency of the expander, similar for both working fluids, ranges from 44% to 57% in the experimental test range. (C) 2016 Elsevier Ltd. All rights reserved.The authors thankfully acknowledge the cooperation of Rank (R) for its support in this project.Molés-Ribera, F.; Navarro Esbri, J.; Peris-Pérez, B.; Mota-Babiloni, A. (2016). Experimental evaluation of HCFO-1233zd-e as HFC-245fa replacement in an organic rankine cycle system for low temperature heat sources. Applied Thermal Engineering. 98:954-961. doi:10.1016/j.applthermaleng.2016.01.011S9549619

Antibiotic residues in milk and cheeses after the off-label use of macrolides in dairy goats

[EN] The limited availability of drugs registered for dairy goats makes veterinarians prescribe off-label treatments with a legally established minimum safety period of seven days. The aim of this work was to verify if the exceptional use of macrolide antibiotics in dairy goats generates residues in milk and cheeses within that period. Hence, three macrolide drugs (erythromycin, tylosin and spiramycin) were administred in an in vivo experiment in dairy goats. Ripened cheeses were made from bulk milk obtained before drug administration, 24¿h after treatment, and at the end of the recommended withdrawal period. Residual amounts of erythromycin (234.9¿±¿52.7¿¿g/kg), tylosin (198.7¿±¿57.8¿¿g/kg) and spiramycin (1539.8¿±¿469.4¿¿g/kg), widely exceeding their legal maximum residue limits (MRLs) established, were detected in milk collected 24¿h after treatment, making the cheese production in most cases impossible. After the seven-day period, only spiramycin was detected in goat¿s milk (79.6¿±¿19.2¿¿g/kg) although no antibiotic residues were found in the cheeses. A withdrawal time of seven days seems suitable to guarantee milk safety after the administration of erythromycin and tylosin without any negative effects neither on the milk nor on the and cheese properties. However, given the rapid elimination of these substances, a shorter withdrawal period might be considered. For spiramycin, persisting in milk for a longer period, further studies on its pharmacokinetics in dairy goats would be recommendable to avoid a potential risk to consumer health.This work is part of the AGL-2013-45147-R funded by Ministerio de Ciencia e Innovacion (Madrid. Spain). The authors thank the 'Program of Support for Research and Development' (PAID-2014, UPV) for support P. Quintanilla PhD studies at Universitat Politecnica de Valencia.Quintanilla-Vázquez, PG.; Beltrán Martínez, MC.; Peris Palau, B.; Rodríguez Garcia, M.; Molina Pons, MP. (2018). Antibiotic residues in milk and cheeses after the off-label use of macrolides in dairy goats. Small Ruminant Research. 167:55-60. https://doi.org/10.1016/j.smallrumres.2018.08.008S556016

Evaluación teórica de fluidos de trabajo con bajo potencial de efecto invernadero como alternativas al HFC-245fa en ciclos orgánicos Rankine

Debido a la preocupación por el medioambiente, los sistemas de cogeneración y ciclos de cola para recuperación de calor residual han recibido una atención considerable durante las últimas décadas. Multitud de ciclos de potencia han sido propuestos para la recuperación de calor a baja temperatura, entre los que destaca el ciclo orgánico Rankine (ORC). Los sistemas ORC pueden ser utilizados para la recuperación de calor residual a nivel industrial, en motores de combustión interna, o para convertir en electricidad fuentes de energía renovables, como solar, biomasa y geotérmica. El HFC-245fa se utiliza comúnmente como fluido de trabajo en instalaciones ORC comerciales, principalmente para recuperación de calor residual a baja temperatura. El HFC-245fa tiene un potencial de agotamiento de la capa de ozono (ODP) nulo. Sin embargo, el impacto medioambiental de un fluido de trabajo cuando se escapa a la atmósfera no se limita solo al agotamiento de la capa de ozono. En realidad, a pesar de que todos los HFCs tienen un ODP nulo, algunos tienen valores altos de potencial de efecto invernadero (GWP) y pueden contribuir de forma significativa al cambio climático en caso de su liberación. En este aspecto, el HFC-245fa presenta un valor de GWP de 858. En el presente trabajo se realiza una evaluación teórica de fluidos de trabajo con bajo potencial de efecto invernadero como alternativas al HFC-245fa en ciclos orgánicos Rankine. Para ello se han considerado dos configuraciones del ciclo, el ciclo básico y el regenerativo. Se ha desarrollado un modelo termodinámico para cada configuración que permita calcular los parámetros que determinan el desempeño del sistema, como son la potencia generada por el expansor, la potencia consumida por la bomba, la eficiencia neta del sistema y parámetros de tamaño para evaluar el tamaño y coste de diferentes tipologías de expansor. Se ha utilizado este modelo para llevar a cabo un análisis termodinámico del sistema ORC variando la temperatura de evaporación y la temperatura de condensación para los distintos fluidos de trabajo estudiados, comparando los resultados con los obtenidos con el HFC-245fa

La legislación en bienestar del ganado ovino y caprino (I)

[ES] En este artículo se señalan los diferentes textos legislativos sobre bienestar animal en pequeños rumiantes actualmente en vigor en Europa, esbozando su contenido y explicando las razones y los fundamentos científicos que motivaron estas normasPeris Palau, B.; Beltrán De Heredia, I.; Alcalde, MJ.; Ruiz, R. (2016). La legislación en bienestar del ganado ovino y caprino (I). Albéitar. (201):18-19. http://hdl.handle.net/10251/89657S181920

Estilos docentes de los profesores universitarios. La percepción de los alumnos de los buenos profesores

Evaluamos los estilos de docencia y evaluación de 323 profesores universitarios mediante el cuestionario CEMEDEPU. Usando análisis jerárquico de conglomerados encontramos cuatro estilos de docencia y evaluación: el primero, centrado en el aprendizaje, constructivista, y con habilidades docentes y de evaluación; el segundo, más centrado en la enseñanza que en el aprendizaje –tradicional-, y con habilidades de docencia y evaluación menores que en el primero; el tercero, centrado en el aprendizaje y con menos habilidades de docencia y evaluación que el primer grupo; y el cuarto, más tradicional que el segundo y con menos habilidades docentes y de evaluación que aquél. Posteriormente, entrevistamos a 50 estudiantes de los mismos profesores, para precisar las características del buen profesor desde su perspectiva. Según los estudiantes, el buen profesor es el que ayuda a establecer relaciones entre los conceptos, fomenta el aprendizaje significativo, es motivador, conecta la teoría con la práctica, fomenta la participación, utiliza metodologías variadas y complementarias, en función de las necesidades, usa el método socrático construyendo el conocimiento junto con sus alumnos y reduce la lección magistral a lo imprescindible. También proporciona a los estudiantes materiales adecuados, apuntes de calidad, etc. Utiliza procedimientos de evaluación formativa y continua y exige razonamiento y aprendizaje significativo. Sus alumnos conocen los criterios y procedimientos de evaluación, que es flexible y justa. Este perfil de buen profesor coincide en lo sustancial con el de los profesores del primer grupo, centrado en el aprendizaje y con habilidades docentes