Thermal and economic performance evaluation of a novel sCO2 recompression Brayton–steam Rankine–absorption cooling system based on solar energy

Together with the developing nano technology, nano-fluids and nano-particles are used as working fluid in energy applications. It is foreseen that nanoparticles have high heat conduction coefficient and it will increase system performance by using as a working fluid in energy systems. Many studies in the literature show that nano fluids increase the heat transfer rate by improving heat transfer. In this study, a performance analysis of an absorption cooling system using solar energy was performed as numerically. LiBr-Al2O3/water nano-fluid has been used in the cooling system as working fluid. The thermodynamic values and calculations used in the analyses were performed with Engineering Equation Solver program. Heat load necessary for the generator is provided with a flat plate solar collector. For different operation condition, the variation of COP values was determined depend on Al2O3/water nanoparticle concentration ratio. When the Al2O3/water nanoparticle concentrations are changed as 0%, 0.5% and 0.1%, it was determined that the COP values increased. Nanoparticles added to the refrigerant at certain concentration values affects the COP values positively of cooling systems. Maximum COP value is 0.86 for 85?C generator temperature and 0.1% Al2O3/water nanoparticle concentration. The lowest COP value was obtained for the 75 oC generator temperature. When the Al2O3/water nanoparticle concentration was increased together with the generator temperature, COP values also increased. When the nanoparticle concentration of the working fluid increases, the viscosity of the nanofluid can be increases. Due to, increased viscosity increases the pressure drop in the flow channel and the pump power required for the flow. Thus, 'minimum viscosity with maximum thermal conductivity' optimisation in applications is very important.

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Operational evaluation of the performance of a solar powered absorption system in Pretoria

Journal of Energy in Southern Africa ◽

10.17159/2413-3051/2013/v24i3a3139 ◽

2013 ◽

Vol 24 (3) ◽

pp. 26-32 ◽

Cited By ~ 2

Author(s):

Tatenda J. Bvumbe ◽

Freddie L. Inambao

Keyword(s):

Economic Performance ◽

Cooling System ◽

Maximum Power ◽

Absorption System ◽

Absorption Cooling ◽

Standard Design ◽

Solar Powered ◽

Absorption Cooling System

A 35kW pilot solar powered absorption cooling system was designed and constructed at Moot Hospital in Pretoria to investigate the technical and economic performance of the technology. Technically, the system produced an estimated 43.938MWh of cooling energy per year and reached a maximum power of 31kW and operated with an average COP of 0.63, which compares favourably with the 0.7 given by the manufacturer. This system has since been decommissioned. Unfortunately, due to a lack of standard design and operation information, the system was overdesigned. As a result, the economic performance of this technology could not be accurately determined.

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