New nanofluids, based on clay minerals, as promising heat carriers for energetics

ABSTRACTIn an automated installation powered by direct current (DC), the boiling curves and heat-transfer-coefficient (HTC) dependencies on the superheat values (ΔT) under free convection conditions for the water nanodispersions of clay minerals – illite, montmorillonite, palygorskite and genetic mixtures of the latter two – were obtained. The effects of some factors on pool boiling heat transfer were also studied.A significant influence of the shape and anisotropy of nanoparticles (NPs) on the heat-transfer parameters of nanofluids (NFs) was detected. A significant critical heat flux (CHF) enhancement (up to 200–300%) at boiling of the nanofluids studied was established, which is due to nanoparticle deposition on the heater surface during nanofluid boiling. The structure of the nanomaterials deposited is important in the enhancement of heat transfer at boiling of nanofluids and in avoiding boiling crises.The present study showed the effectiveness of clay-mineral nanofluids for extra emergency cooling of overheated surfaces of powerful equipment in the event of the sudden onset of a boiling crisis.

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Наножидкости для энергетики: механизм влияния диспергентов на тепловые параметры и кризисные явления при кипении

Журнал технической физики ◽

10.21883/jtf.2020.02.48806.221-19 ◽

2020 ◽

Vol 90 (2) ◽

pp. 175

Author(s):

В.Н. Морару ◽

Б.И. Бондаренко ◽

С.В. Сидоренко ◽

Д.В. Комыш

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Critical Heat Flux ◽

Direct Current ◽

Sedimentation Stability ◽

Boiling Crisis ◽

Transfer Parameters ◽

The Heat Transfer Coefficient

Abstract: The effect of dispersants organic (CTAB) and inorganic nature (sodium pyrophosphate and sodium silicate) on the critical heat flux (CHF) and heat-transfer coefficient (HTC) of boiling various aqueous nanofluids (NFs) under conditions of free convection is studied. It has been established that the addition of ionic dispersants to aluminosilicate NFs, increasing their aggregative and sedimentation stability, as a rule, worsens their heat-transfer parameters during boiling, causing a sudden pre-crisis heater burnout in a test unit powered by direct current. The mechanism of the phenomenon is revealed. On the contrary, the addition of dispersants and surfactants to carbon-containing NFs with high thermal conductivity, improving their stability, at the same time increases the heat transfer coefficient during boiling of NFs, but also cause pre-crisis heater burnout in the case of direct current heating. The effect of dispersants on crisis phenomena during boiling of water and NFs is analyzed and the causes of sudden pre-crisis heater burnout have been elucidated. Several mechanisms have been proposed for interpreting the observed effects, from which the expediency of using alternating heating current and non-ionic, non-foaming surfactants and dispersants to avoid an early onset of the boiling crisis in order to achieve higher values of the critical heat flux and the heat transfer coefficient during the NFs boiling.

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