Thermal performance and functional sustainability limit of working fluids in a low-heat regenerative organic Rankine cycle at varying evaporator heat input
- Country : Nigeria
- Subject : Mechanical
Keywords : Thermal, functional sustainability, regenerative, evaporator, exergy
Abstract
Thermal and functional sustainability limit (FSL) or exergetic sustainability limit (ESL) of refrigerants in a regenerative organic Rankine cycle (RORC) is presented. The objective is to determine the limit where a particular refrigerant can be more eco-friendly at some thermodynamic inputs. Three refrigerants R113, R141b and R245fa were considered at different evaporator heat inputs (EHI). The FSL for the refrigerants were calculated at 1.10 for 247.92 kW, 0.92 for 191.88 kW and 1.025 for 240.11kW using R245fa, R113 and R141b respectively. Also, the environmental effect factor (EEF) at FSLs of the refrigerants were estimated at 0.00958, 0.01076 and 0.00958 in the same order. The environmental damage at EHI range between 180≤EHI≤320kW was 0.35 % for R245fa, 12.25 % for R113 and 0.991 % for R141b. R245fa was more sustainable than other refrigerants. However, comparing the thermodynamic approximated values of the refrigerants with the ODP and GWP classifications the two were reasonably associated. Conversely, the study concluded that refrigerants have a limit of optimal performance where they function with less environmental impact. The latter is described as the functional sustainability limit. Thus, the design and optimisation of systems to operate on such optimal limits will enhance performance and reduce environmental complications.
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