Summary
Stationary solar collector such as flat‐plate collector is a thermal device, which traps solar energy and converts it into heat that can be used in industrial and domestic applications such as water heating. Flat‐plate collector thermal performance enhancement is investigated in this research paper. Two cross‐sectional geometries of the tube in the heat exchanger were investigated; a normal circular tube and a twisted tube were used in the experiment. The aim of the twisted tube exchanger is to enhance the performance of heat transfer of the tubes and to reduce the shell pressure drop; flat‐plate solar collector is the used application to study the heat exchanger performance. Both twisted tubes heat exchanger and normal circular tubes heat exchanger were examined in the same location and conditions with the same solar collector, both were used in the heat exchanger to study their effect, with two different working fluids, which are distilled water and multiwalled carbon nanotube (MWCNT)/water nanofluid. The system shows an increase in the performance when twisted tubes were used in the system compared with the circular tubes in both distilled water and MWCNT/water nanofluid by 12.8% and 12.5%, respectively, with an improvement by 34% for twisted tubes with MWCNT compared with normal circular tubes with distilled water.
Summary
Fossil fuels demonstrate pollution effects and significant emissions on the atmosphere, which made the use of clean, renewable sources of energy a necessity. Renewable energy has many sources, but the most promising and cheapest energy source is solar energy, which has led to a focus on efficient solar energy harvesting to be cheaper for public use. Stationary solar collectors like evacuated tube and flat‐plate solar collectors are the most commonly used solar collectors for their simplicity of installation and maintenance. They are mostly used for domestic applications such as solar water heaters. Nanofluids can improve the thermal properties of the working fluid which can improve the performance of a collector. This review paper discussed the effect of different parameters on the stationary solar collector's performance, such as nanoparticle use, nanoparticle size, concentration, and the base fluid of the nanofluid. This review paper also aims to summarize previous studies performed on the use of different nanofluids on the two types of circulation that can be either thermosiphon or forced circulation for both collectors to investigate the energetic and exergetic efficiencies. The theoretical performance analysis equations of stationary solar collectors are provided too. From the reviewed results, it was concluded that a substantial improvement in both the energetic and exergetic efficiencies of both collectors had been obtained from the use of carbon‐based nanofluids compared to a significant number of different nanofluids. The paper also discusses the significant challenges of nanofluid use and how to overcome them in stationary solar collectors.
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