Desarrollo de un modelo de ciclo orgánico Rankine. Ejemplo de aplicación para análisis de fluidos de trabajo de bajo potencial de efecto invernadero

Treball Final de Màster Universitari en Enginyeria Industrial. Codi: SJA020. Curs acadèmic: 2016/2017En el contexto actual, de crisis y competitividad, resulta esencial establecer aspectos que marquen la diferencia; una buena opción, es la revalorización de fuentes de calor residual, tanto para aumentar la eficiencia energética de los procesos industriales, como para mejorar su impacto medioambiental. En gran parte de los procesos industriales se producen pérdidas de energía en forma de calor residual. Son pocos los procesos que reutilizan el calor residual de los mismos, siendo la mayor parte desaprovechado. La mayoría considera el calor como un recurso que desaparece luego de su utilización, pero claro está que la energía ni se crea ni se destruye, por tanto al no reutilizarla la estaríamos desperdiciando, con los recursos económicos que esto conlleva

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

Experimental exergy and energy analysis of a novel high-temperature heat pump with scroll compressor for waste heat recovery

The industrial sector demands novel sustainable energy systems to advance in its decarbonisation and meet the targets of the Paris Agreement for the climate change mitigation. High-Temperature Heat Pumps (HTHPs) are being investigated as a feasible energy conversion technology alternative to traditional fossil fuel boilers. This paper presents the first experimental results of an HTHP prototype equipped with a modified scroll compressor and internal heat exchanger (IHX). The elements of the main and secondary circuits are presented, as well as the test methodology and heat balances are exposed. The tests have been performed using HFC-245fa at heat source temperatures between 60 and 80 °C, and heat sink temperatures between 90 and 140 °C. The heating capacity and coefficient of performance (COP) varied between 10.9 and 17.5 kW and between 2.23 and 3.41, respectively. An exergetic analysis indicated that the expansion valve was the component with the worst second law efficiency and the compressor presented the highest potential improvement over the other cycle components. A computational analysis of low global warming potential (GWP) refrigerant alternatives was carried out, which confirmed the benefits of using an internal heat exchanger (IHX) and the good performances of the low-GWP refrigerants: HCFO-1224yd(Z), HCFO-1233zd(E), and HFO-1336mzz(Z). Finally, we proved that the proposed system can save up to 57% of the equivalent CO2 emissions of a natural gas boiler. This paper provides a reference for the high-temperature heat pump recovery of the low-grade waste heat from industrial energy processes

Thermodynamic analysis of low GWP alternatives to HFC-245fa in high-temperature heat pumps: HCFO-1224yd(Z), HCFO-1233zd(E) and HFO-1336mzz(Z)

This paper analyses the feasibility of HCFO-1224yd(Z), HCFO-1233zd(E) and HFO-1336mzz(Z), three low global warming potential (GWP) refrigerants, as alternatives to HFC-245fa in high-temperature heat pump (HTHP) systems for low-grade waste heat recovery. HTHPs are a sustainable technology that can help to mitigate climate change through the thermal valorisation of the industrial low-grade waste heat. Before presenting and analysing the results, mapping of the minimum superheat degree requirement in the operating range, and the influence of the Internal Heat Exchanger (IHX) on each alternative are studied. The simulations were carried out at condensing temperatures from 115 to 145 °C and evaporating temperatures from 45 to 75 °C, using a single-stage cycle with and without IHX. Finally, the Total Equivalent Warming Impact (TEWI) evaluation is performed to illustrate the environmental effect of each alternative. Attending to the results, HCFO-1233zd(E) improves the COP about 27% compared to HFC-245fa, whereas HFO-1336mzz(Z) and HCFO-1224yd(Z) show an improvement of approx. 21 and 17%, respectively. Although HCFO-1233zd(E) and HCFO-1224yd(Z) present similar suction volumetric flow rate to HFC-245fa, HFO-1336mzz(Z) shows a relative increment up to 80%, and therefore, higher compressor and installation size are expected for this refrigerant. Finally, the TEWI analysis presents a significant reduction of the equivalent CO2 emissions for each low GWP alternative, between 59 and 61%. HCFO-1233zd(E) shows the highest reduction in all the simulation cases, followed by HCFO-1224yd(Z) and HFO-1336mzz(Z)

Optimisation of high-temperature heat pump cascades with internal heat exchangers using refrigerants with low global warming potential

High-temperature heat pumps (HTHPs) based on vapour compression can be used for industrial low-grade waste heat valorisation, which can aid in mitigating climate change. Currently, the performance of HTHPs operating at high-temperatures lifts is limited; therefore, advanced configurations become an opportunity for their utilization. This paper presents an HTHP cascade with configurations of internal heat exchangers (IHXs) that uses low GWP refrigerants in both high-stage (HS) (HCFO-1233zd(E), HFO-1336mzz(Z), HCFO-1224yd(Z), and pentane) and low- stage (LS) (HFO-1234yf, HFO-1234ze(E), butane, isobutane, and propane) cycles. Prior to the analysis and presentation of results, an optimisation of the operating conditions is performed based on intermediate temperature and IHX effectiveness in both stage cycles. Results indicate that butane and isobutane appear to be the most convenient working LS fluids from the point of view of coefficient of performance (COP). The highest system performance is obtained using pentane and HFO-1336mzz(Z) in the HS cycle. Compared to third-generation refrigerants (HFC- 245fa/HFC-134a), a slight COP improvement is obtained using HCFO-1233zd(E), and HCFO- 1224yd(Z). A comparable or even lower volumetric flow rate at the HS compression suction is also observed. The use of pentane/butane achieved maximum COP (3.15), which is a 13% improvement compared to COP obtained when HFC-245fa/HFC-134a is employed

Search for low global warming potential working fluids for low-temperature and small-scale organic Rankine cycles. An analysis of HCFO-1224yd(Z) as potential candidate

Esta tesis se centra en encontrar un fluido de bajo potencial calentamiento atmosférico (PCA) capaz de trabajar en instalaciones ORC de pequeña escala y baja temperatura previamente diseñadas para el uso de HFC-245fa. Para ello, además de revisar el estado en el que se encuentra esta tecnología, se realiza un estudio teórico y experimental. El estudio teórico compara el comportamiento del HFC-245fa con el de sus principales alternativas de bajo PCA: HCFO-1224yd(Z), HFO-1336mzz(Z), HCFO-1233zd(E), HFO-1234ze(Z), HFO-1336mzz(E) y R-514-A. Debido a sus similares resultados en cuanto a potencia y eficiencias y a su similar tamaño de expansor, el HCFO-1224yd(Z) destaca como principal candidato. Por ello, el HCFO-1224yd(Z) se prueba experimentalmente en dos instalaciones diferentes. Se obtienen unos resultados muy similares en cuanto a eficiencia neta pero una potencia neta menor a la del fluido de referencia, no obstante, ésta sería susceptible de mejora mediante pequeñas modificaciones en el ciclo.The present thesis proposes finding a low global warming potential fluid suitable to work in small-scale, low-temperature organic Rankine cicles, previously designed for using HFC-245fa. The theoretical study shows how HCFO-1224yd(Z) stands out as the main candidate to substitute the HFC-245fa, due to its similar results in terms of power, efficiencies, and volumetric flow at the expander inlet. The experimental analysis proves the suitability of using HCFO-1224yd(Z) as a direct replacement. Besides offering a net power lower compare with the reference fluid, it offers very similar results in terms of net efficiency. For certain operating points, when the temperature of the heat source is high, the HCFO-1224yd(Z) offers higher net efficiency. In addition, the results obtained could be even improve with small cycle modifications.Programa de Doctorat en Tecnologies Industrials i Material

Estudio y optimización del funcionamiento de un mezclador por cavitación

Treball Final de Grau en Enginyeria Mecànica. Codi: EM1047. Curs acadèmic: 2014-201

Évaluation théorique de différentes configurations de pompes à chaleur à haute température pour la récupération de chaleur résiduelle à basse température

The introduction of high-temperature heat pumps for waste heat recovery with low GWP refrigerants can reduce the greenhouse gas emissions in the industrial sector. This article evaluates the energy performance and the volumetric heating capacity of five vapour compression system configurations using n-Pentane, Butane, HCFO-1233zd(E) and HFO-1336mzz(Z) as HFC-245fa low GWP alternative fluids for heating production at temperatures of 110, 130 and 150°C and different temperature lifts. The selected architectures and the equations are presented, and the most appropriate method to calculate the intermediate pressure is selected. The results of the simulation show that single-stage cycle with an internal heat exchanger (IHX) becomes the most efficient configuration at lower temperature lifts whereas two-stage cycle with IHX at higher lifts. While n-Pentane provides the highest energy performance values, Butane (only up to 130°C) and HCFO-1233zd(E) highlight in the heating volumetric capacities. HFO-1336mzz(Z) provides intermediate values in both parameters. Consequently, the working fluid selection is highly dependent on the specifications and the energetic and installation costs

Évaluation théorique de différentes configurations de pompes à chaleur à haute température pour la récupération de chaleur résiduelle à basse température

The introduction of high-temperature heat pumps for waste heat recovery with low GWP refrigerants can reduce the greenhouse gas emissions in the industrial sector. This article evaluates the energy performance and the volumetric heating capacity of five vapour compression system configurations using n-Pentane, Butane, HCFO-1233zd(E) and HFO-1336mzz(Z) as HFC-245fa low GWP alternative fluids for heating production at temperatures of 110, 130 and 150°C and different temperature lifts. The selected architectures and the equations are presented, and the most appropriate method to calculate the intermediate pressure is selected. The results of the simulation show that single-stage cycle with an internal heat exchanger (IHX) becomes the most efficient configuration at lower temperature lifts whereas two-stage cycle with IHX at higher lifts. While n-Pentane provides the highest energy performance values, Butane (only up to 130°C) and HCFO-1233zd(E) highlight in the heating volumetric capacities. HFO-1336mzz(Z) provides intermediate values in both parameters. Consequently, the working fluid selection is highly dependent on the specifications and the energetic and installation costs

Systèmes frigorifiques à ultra-basse température : configurations et frigorigènes permettant de réduire l’impact environnemental

Several environmental protection policies have been enforced restricting working fluids with high global warming potential (GWP) values used in many types of refrigeration and heat pump systems. However, ultralow-temperature (ULT) refrigeration has not been included, which commonly uses refrigerants with very high GWP values (such as R23 and R508B). Therefore, publicly available research programs seeking low GWP alternative refrigerants do not cover this application and the transition to more environmentally friendly fluids is slowed down. This work presents a comprehensive review that summarizes and discusses the available studies about ULT refrigeration systems. The current status of the technology, system architectures and refrigerants are analyzed. Moreover, the transition towards low GWP refrigerants is proposed, presenting the most promising low GWP alternatives. The most commonly used architectures for ULT refrigeration are the two-stage cascade and auto-cascade, in which the use of ejector has recently been considered in research papers. R170 and R1150 are the available natural refrigerants suitable for ULT, but they have not yet been included in many flammability and risk assessment studies. The A2 hydrofluoroolefin R1132a has been recently proposed as a blend component to avoid problems of stability. However, more information is still necessary to start with simulation and experimental studies. R41 could be an alternative due to its low GWP and suitable normal boiling point, but it has not been thoroughly investigated yet. Overall, there is a gap in the literature in terms of developing alternative refrigerants for ULT refrigeration. This study aims at shedding light on this gap to direct future research in this field towards reliable, environmentally friendly and marketable alternative refrigerants