Abstract
In the present article, the heat transfer and fluid flow of the air in a compact microchannel gas heater (MCGH) was experimentally quantified. To understand the effect of heat flux value (HFV), and inlet velocity on the heat transfer coefficient (HTC), wall temperature, friction factor, Nusselt number, average pressure-drop value (PDV) and performance index (PI), a microchannel gas heater was constructed and tested with pressurized air. The results showed that the HTC was 20 W/(sqmK) to 70 W/(sqmK), corresponding to inlet velocities 6.7 m/s and 16.7 m/s, respectively within HFV < 1 kW/m2. Also, the highest PI was 1.19 meaning that the HT rate can be increased by 19% at u = 15 m/s in comparison with the reference case (at u = 13.3 m/s). Likewise, the HTC was intensified once the inlet velocity is increased. It was also identified that increasing the HFV has a strong effect on wall temperature, however, slightly changes the HTC. By increasing the heat flux value from 200 W/sqm to 1000 W/sqm, the HTC increased only by 4.7% which was associated with the poor thermophysical properties of air flowing inside MCGH. Two main mechanisms of wall slip and viscous heating were identified as main contributors to the heat transfer enhancement in MCGH.
Highlights
While molten salt is a promising heat transfer fluid, corrosion and technical challenges associated with storage, pumping, and handling molten salts are barriers and limitations that require further research and development
Two domains can be identified: In domain I, the wall temperature suddenly increases at the inlet region and linearly region closeuptoreaching the outlet the microchannel
To evaluate the performance of the microchannel gas heater, a series of experiments were To designed andthe conducted to investigate the values of heat transfer coefficient (HTC), pressure-drop value (PDV), atavarious operating evaluate performance of the microchannel gas heater, series of experiments conditions
Summary
The heat transfer and fluid flow of the air in a compact microchannel gas heater (MCGH) was experimentally quantified. To understand the effect of heat flux value (HFV), and inlet velocity on the heat transfer coefficient (HTC), wall temperature, friction factor, Nusselt number, average pressure-drop value (PDV) and performance index (PI), a microchannel gas heater was constructed and tested with pressurized air. The solar power is transferred into the heat in the working fluid such as molten salt, oil, steam and air, which drives turbines to generate electricity. The utilisation of air as heat transfer fluid can potentially eliminate pipe clogging and temperature limitation of conventional receivers while addressing technical challenges associated with molten salts
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