| TAZ-TFM-2020-027 |
Risk Assessment of Mildly Flammable Refrigerants with los GWP for Heat pump
Ciércoles Alloza,Inés
Bubbico, Roberto (dir.)
Sánchez Cebrián, José Luis (ponente)
Universidad de Zaragoza,
EINA,
2020
Ingeniería Química y Tecnologías del Medio Ambiente department, Ingeniería Química area
Máster Universitario en Ingeniería Química
Abstract: Given the growing demand for cooling, and taking into account the impact of global warming associated with cooling technologies the global climate commitment to reduce the impact of fluorinated gases and the regulations controlling their use in the European Union has increased . This thesis investigates new refrigerants that have been recently proposed to meet the demands of the heat pumps in the refrigeration industry, which must satisfy the legislative requirements of the F-gas Regulation and facilitate meeting the goals of Montreal and Kyoto Agreement.
The fluids R32, R1234ze, R1234yF, R452b and R454b have been theoretically analyzed in comparison with the commonly used fluorinated refrigerant in heat pump: R410A. To compare these refrigerants, an excel sheet has been used to calculate the COP for the different cases studied using the REFPROP computer program to know the thermodynamic data of each fluid. The cases studied are the three different heat pump applications : radiators, radiant floor and fan coil and it has been studied for an evaporator temperature range of -15 to 12 ºC, i.e. the COP has been calculated for eighteen different situations. For all of them, the same conclusion has been concluded: all these five proposed fluids have a higher COP than the fluid to be replaced, R410A. It based on this COP for all the cases studied, the best fluids are R454b and R1234Ze(E). Choosing the fluid R454b as the best alternative because its latent heat and vapour density are higher that R1234ze(E) and therefore the flow and size of the pump is smaller, which generally translates into economic savings.
However, this refrigerant shows flammability characteristics. For this reason, this paper is checked the fluid risk by a risk assessment. For this assessment two scenarios are analyzed by numerical model, Plume Model: outside and inside of 20 m2 scenario using a 50 kW heat pump. Concluding on the one hand, that in outside conditions a leak would not enter ignition due to the concentration obtained is less than the minimum necessary. In addition from 200 meters of distance the concentration of this fluid would be zero.
And that in the hypothetical case that a jet fire takes place is observed that from 10 meters of the leak there is no more radiation.
On the other hand, for the room scenario the calculated concentration would be 550 g/m3. This concentration is higher than the acute toxicity exposure limit (435 g/m3) so it is not safe for a human being to work in the situations described.
The fluids R32, R1234ze, R1234yF, R452b and R454b have been theoretically analyzed in comparison with the commonly used fluorinated refrigerant in heat pump: R410A. To compare these refrigerants, an excel sheet has been used to calculate the COP for the different cases studied using the REFPROP computer program to know the thermodynamic data of each fluid. The cases studied are the three different heat pump applications : radiators, radiant floor and fan coil and it has been studied for an evaporator temperature range of -15 to 12 ºC, i.e. the COP has been calculated for eighteen different situations. For all of them, the same conclusion has been concluded: all these five proposed fluids have a higher COP than the fluid to be replaced, R410A. It based on this COP for all the cases studied, the best fluids are R454b and R1234Ze(E). Choosing the fluid R454b as the best alternative because its latent heat and vapour density are higher that R1234ze(E) and therefore the flow and size of the pump is smaller, which generally translates into economic savings.
However, this refrigerant shows flammability characteristics. For this reason, this paper is checked the fluid risk by a risk assessment. For this assessment two scenarios are analyzed by numerical model, Plume Model: outside and inside of 20 m2 scenario using a 50 kW heat pump. Concluding on the one hand, that in outside conditions a leak would not enter ignition due to the concentration obtained is less than the minimum necessary. In addition from 200 meters of distance the concentration of this fluid would be zero.
And that in the hypothetical case that a jet fire takes place is observed that from 10 meters of the leak there is no more radiation.
On the other hand, for the room scenario the calculated concentration would be 550 g/m3. This concentration is higher than the acute toxicity exposure limit (435 g/m3) so it is not safe for a human being to work in the situations described.
Tipo de Trabajo Académico: Trabajo Fin de Master
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