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Experimental Study on Heat Transfer Characteristics of Nanorefrigerant in Copper Tube

Author: YangDi
Tutor: SunBin
School: Tohoku Electric Power University
Course: Heating,Gas Supply, Ventilation and Air Conditioning Engineering
Keywords: nanorefrigerant heat transfer enhancement stability internal threadcopper tube corrugated pipe
CLC: TB611
Type: Master's thesis
Year: 2014
Downloads: 20
Quote: 0
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Abstract


Based on the concept of nanofluids, the concept of nanorefrigerants has beenproposed, and the main difference between them lies in the base fluid, thenanorefrigerants use refrigerants as its base fluid. According to certain mass fraction,we add the nano particles into the refrigerants, preparing a new and efficient heattransfer working medium. The thermal conductivity of nanorefrigerants is high, thestability is good, and the abrasion to the equipment is small, too, which puts forwarda new direction for the development of applied to nanorefrigerant heat exchanger.Based on these, in this thesis, we study the stability of five nanorefrigerents and theboiling transfer characteristics of those five nanorefrigerents in three different tubes.In this thesis, nanorefrigerants are prepared by physical and chemical dispersionmethods. First, the refrigerant is directly mixed with the nanoparticles. Second, thesurface dispersants are added, and the mixture is shaken for30min in an ultrasonicshaker. We use the visual method and contrasting transmission method to evaluate thestability of the nano refrigerants. We have found that when the concentration is at thesame time, the stability of nanorefrigerants adding the surface dispersant has so littledifference; while, the stability of the nanorefrigerant without surface dispersant isvery bad, and the stability and the density are inversely proportional.The flow boiling heat transfer experiment results of nanorefrigerats had shownthat at the same mass flow, the heat transfer coefficient of nanorefrigerantsremarkably changes and the relationship of growth with the nanoparticle massfraction is substantially linear with increased mass fraction of nanoparticles. The massfraction of nanoparticles is the main factor affecting the heat transfer enhancement ofthe nanorefrigerants; different nanoparticles have different effects on the heat transferperformance of nanorefrigerants. A higher thermal conductivity of nanoparticlesresults in higher heat transfer performance of the corresponding nanorefrigerant; with increased quality, the heat transfer coefficient of the nanorefrigerants increases andreaches the maximum when x=0.5–0.6.

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CLC: > Industrial Technology > General industrial technology > Refrigeration Engineering > Refrigeration theory > Refrigeration thermodynamics, heat transfer , mass transfer , fluid mechanics
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