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1

An experimental study on the thermal efficiency of a passive solar air collector

Fiuk J. J., Dutkowski K., Piątkowski P.

Engineering Transactions

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2017

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Vol. 65, iss. 2

251--268

EN

This paper presents the results of an experimental investigation on a prototype flat passive solar air collector. The collector consists of an aluminum casing, transparent cover, air inlet and outlet channels and a flat absorber plate mounted inside the casing. The design is unique because the cover is made of transparent cellular polycarbonate sheet, a material whose application to passive solar collectors has not been extensively researched. The cover is 5 mm thick. The airflow through the collector is driven by natural convection. The study was performed on a laboratory set-up consisting of vertically mounted collector, external source of thermal radiation in the form of infrared lamps, measurement equipment and data acquisition system. The tests were performed for a range of irradiance G = 0–540 W/m2 . The following parameters were determined: absorber surface temperature, air temperature increase ∆T , collector heat output and efficiency. Comparing the obtained results to the available data on conventional glass-covered designs has shown that the optical performance of polycarbonate cover is lower. However, in terms of thermal efficiency this is compensated by good insulation. The measurements for the maximum attainable irradiance of Gmax = 540 W/m2 are as follows: the mean air velocity at inlet w = 1.1 m/s, the volumetric flow rate of air V˙ = 30 m3 /h, and the corresponding heat output and thermal efficiency Q = 386 W and η = 36%, respectively.

2

Experimental research on the impact of the application of fins on absorber surface on thermal efficiency of passive solar air collector

Dutkowski K., Fiuk J., Piątkowski P.

Polska Energetyka Słoneczna

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2016

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nr 1-4

32--36

EN

In this paper an experimental results on passive solar air collectors are presented. An impact of application of waveform fins on the absorber surface on thermal efficiency was investigated. The results were compared with experiment on passive solar air collector with flat absorber surface. The experiment was conducted under steady state artificial radiation conditions in a laboratory environment. This enabled the acquisition of differences in flow and thermal parameters of the two designs. At the experimental stand following parameters were measured: irradiance, air temperature at inlet and outlet to the collector, mean air velocity at the inlet duct of the collector. The impact of irradiance on temperature increase, volumetric flow rate and thermal efficiency is shown. It was established that thermal efficiency of the collector with expanded absorber surface in form of fins is 10-15% higher than the efficiency of flat absorber collector.

3

Brief literature review on air solar collectors

Dutkowski K., Fiuk J., Sikora M.

Instal

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2016

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nr 12

25--28

EN

In this paper a short literature review on the solar collectors has been presented. A classification has been made according to application areas: heating in industrial processes (i.e. drying of agricultural products, biomass drying) or in civil engineering (i.e. air conditioning, space heating). Solar collectors have been classified in regard to their design: cover material, direction and type of flow, means of heat transfer intensification. Direction of future research in the field of solar collectors has been briefly discussed in both experimental and numerical research. The most popular trends in development of solar air collectors aiming at making the technology more common were specified. The most notable is heat accumulation through the utilization of phase changing materials (PCM).

PL

W artykule przedstawiono przegląd aktualnego stanu wiedzy na temat powietrznych kolektorów słonecznych. Dokonano podziału kolektorów ze względu na ich przydatność do celów grzewczych w procesach przemysłowych (np.: suszenie produktów rolnych, suszenie biomasy energetycznej) czy w budownictwie (wentylacja i klimatyzacja pomieszczeń). Przedstawiono podział kolektorów ze względu na: rodzaj pokrycia kolektora, kierunek i sposób przepływu powietrza, sposób intensyfikacji wymiany ciepła poprzez wydłużenie drogi jaką pokonuje czynnik roboczy, czy rozwinięcie powierzchni wymiany ciepła. Opisano kierunki badań eksperymentalnych oraz analiz numerycznych z wykorzystaniem komputerowych programów z zakresu CFD. Wskazano proponowane kierunki rozwoju powietrznych kolektorów słonecznych zmierzające do ich upowszechnienia, w tym te, które pozwalają na akumulację ciepła poprzez wykorzystanie np.: materiałów zmiennofazowych (PCM).