engleski

Solar concrete collectors for heating of domestic hot water

In this paper, the performance of a domestic hot water heating system with solar concrete collector is studied. The principal components of this system are a serpentine pipe, a storage tank and an auxiliary heating source, e.g. a gas burner or an electric resistance heater. The serpentine pipe can be placed inside roof slabs, concrete pavements or walls. A numerical code based on the finite volume method has been developed in order to solve transient three-dimensional heat conduction in the concrete element with the serpentine pipe inside. Heat transfer at the exposed surface of the concrete element is described with a mixed convection-radiation boundary condition. The numerical simulations gave the following results: water temperatures throughout the serpentine pipe, storage tank temperatures and efficiency of the solar concrete collector heating system. It has been seen that the serpentine pipe can heat water up to 40-50 °C while the heat storage tank reaches temperatures of 30-40 °C during the summer period. The average May to September efficiency (i.e. solar fraction) is 50-70% in Rijeka (Croatia), meaning that less than half the energy demand is supplied by the auxiliary heating source. Several parameters influencing the efficiency of solar concrete collector systems are studied: pipe spacing, pipe length, pipe depth, solar absorptance and tilt angle of the concrete element. For example, the spacing between pipe bends should be at least 15 cm to avoid pipe-to-pipe thermal influence.

Solar concrete collector; Solar energy; Domestic hot water; Finite volume method

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