A high concentrating photovoltaic/thermal system based on a water spray cooling device has been investigated in this paper. The system uses point-focus Fresnel lens as a concentrator with a concentration ratio over 1000. Both of the numerical thermal and electrical models have been developed to investigate the performance of the system. Moreover, the spray cooling has been used to solve the problem of high heat flux transfer and get good temperature uniformity, which is considered as an efficient method to develop the electrical efficiency and thermal efficiency. The results show that the overall efficiency is mainly influenced by water mass flow.
This paper studies the frozen pork transportation in short and long
distances, the loss of cooling capacity and the energy consumption in the
cold chain transportation a reanalyzed experimentally and numerically. It finds
that the material for freezer insulation plays in important role in energy
consumption and energy saving during refrigerated transportation, an optimal
freezer can reduce temperature rise by 13.88%and the heat flow by
71.05%compared with the traditional ones. A fractal model is established to
reveal the thermal property of the freezer.
In this study, a closed-loop spray cooling system using R134a as the working
fluid was established. The heat transfer characteristics and influencing
mechanism of transient spray cooling were studied. The transient spray
cooling curve under quenching was built accurately. The results show that the
vapor film suppressed time tsup is the main period that the spray
cooling must pass through. The flow rate and the sub-cooling of R134a have
little effect on the cooling rate but the critical heat flux, which are
mainly affected by chamber pressure. The transient Jacob number Ja+ decreases
with the increases of chamber pressure. As Ja+ decreases, the growth of vapor
film is inhibited, then the tsup reduces in consequence. The surface
temperature drop point and critical heat flux increases with the rise of
chamber pressure. The maximum critical heat flux is 70.08 W/cm2in this
experiment.
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