scholarly journals Mathematical Model for Analyzing Heat Transfer Characteristics of Ablative Thermal Insulating Material

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Junjie Gao ◽  
Haitao Han ◽  
Daiying Deng ◽  
Jijun Yu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mathematical Model ◽  
Size Distribution ◽  
Distribution Area ◽  
Heat Transfer Characteristics ◽  
Equivalent Thermal Conductivity ◽  
Insulating Material ◽  
Transfer Characteristics ◽  
Thermal Insulating

A mathematical model based on minimal thermal resistance and equal law of specific equivalent thermal conductivity is developed to discuss the heat transfer characteristics of ablative thermal insulating material from the mesoscopic scale. Based on the statistical results of mesoscopic parameters, the microstructure unit cell model was established to analyze the influence rule of mesoscopic parameterization which includes the size, distribution, and positional relation of microsphere and fiber. The results show that the equivalent thermal conductivity decreases with the density, size, distribution area, and distance of microsphere and the space distance and volume fraction of fiber decreasing. Besides, the equivalent thermal conductivity will become larger when more quality of heat transfers along the fiber direction. Exploring the relationship between the macroscopic heat transfer process and the microstructure is meaningful for exploring the heat transfer behavior of thermal insulating material and improvement of the processing technology.

Maximizing Heat Transfer Through Joint Fin Systems

2005 ◽  
Vol 128 (2) ◽  
pp. 203-206 ◽  
Author(s):  
A.-R. A. Khaled
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Performance ◽  
Critical Length ◽  
The Other ◽  
Rigid Fixation ◽  
Convection Coefficient ◽  
Heat Transfer Characteristics ◽  
Cold Side ◽  
Transfer Characteristics

Heat transfer through joint fins is modeled and analyzed analytically in this work. The terminology “joint fin systems” is used to refer to extending surfaces that are exposed to two different convective media from its both ends. It is found that heat transfer through joint fins is maximized at certain critical lengths of each portion (the receiver fin portion which faces the hot side and the sender fin portion that faces the cold side of the convective media). The critical length of each portion of joint fins is increased as the convection coefficient of the other fin portion increases. At a certain value of the thermal conductivity of the sender fin portion, the critical length for the receiver fin portion may be reduced while heat transfer is maximized. This value depends on the convection coefficient for both fin portions. Thermal performance of joint fins is increased as both thermal conductivity of the sender fin portion or its convection coefficient increases. This work shows that the design of machine components such as bolts, screws, and others can be improved to achieve favorable heat transfer characteristics in addition to its main functions such as rigid fixation properties.

Pool Boiling Characteristics of Metallic Nanofluids

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
K. Hari Krishna ◽  
Harish Ganapathy ◽  
G. Sateesh ◽  
Sarit K. Das
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Boiling Heat Transfer ◽  
Volume Fraction ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Solid Particles ◽  
Heater Surface ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Nanofluids, solid-liquid suspensions with solid particles of size of the order of few nanometers, have created interest in many researchers because of their enhancement in thermal conductivity and convective heat transfer characteristics. Many studies have been done on the pool boiling characteristics of nanofluids, most of which have been with nanofluids containing oxide nanoparticles owing to the ease in their preparation. Deterioration in boiling heat transfer was observed in some studies. Metallic nanofluids having metal nanoparticles, which are known for their good heat transfer characteristics in bulk regime, reported drastic enhancement in thermal conductivity. The present paper investigates into the pool boiling characteristics of metallic nanofluids, in particular of Cu-H2O nanofluids, on flat copper heater surface. The results indicate that at comparatively low heat fluxes, there is deterioration in boiling heat transfer with very low particle volume fraction of 0.01%, and it increases with volume fraction and shows enhancement with 0.1%. However, the behavior is the other way around at high heat fluxes. The enhancement at low heat fluxes is due to the fact that the effect of formation of thin sorption layer of nanoparticles on heater surface, which causes deterioration by trapping the nucleation sites, is overshadowed by the increase in microlayer evaporation, which is due to enhancement in thermal conductivity. Same trend has been observed with variation in the surface roughness of the heater as well.

Experimental Convective Heat Transfer With Nanofluids

2008 ◽  
Author(s):  
S. Kabelac ◽  
K. B. Anoop
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Turbulent Regime ◽  
Heat Transfer Characteristics ◽  
Forced Convective Heat Transfer ◽  
Transfer Characteristics

Nanofluids are colloidal suspensions with nano-sized particles (<100nm) dispersed in a base fluid. From literature it is seen that these fluids exhibit better heat transfer characteristics. In our present work, thermal conductivity and the forced convective heat transfer coefficient of an alumina-water nanofluid is investigated. Thermal conductivity is measured by a steady state method using a Guarded Hot Plate apparatus customized for liquids. Forced convective heat transfer characteristics are evaluated with help of a test loop under constant heat flux condition. Controlled experiments under turbulent flow regime are carried out using two particle concentrations (0.5vol% and 1vol %). Experimental results show that, thermal conductivity of nanofluids increases with concentration, but the heat transfer coefficient in the turbulent regime does not exhibit any remarkable increase above measurement uncertainty.

Heat Transfer and Flame Retardant Properties of Silicone Elastomers

2017 ◽  
Vol 44 (1) ◽  
pp. 1-8
Author(s):  
K. Lehmann ◽  
A. Nawracala
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Flame Retardant ◽  
Heat Transfer Characteristics ◽  
Flame Resistance ◽  
Silicone Elastomers ◽  
Transfer Characteristics ◽  
Ul 94 ◽  
Flame Retardant Properties

The following article discusses the use of novel compounds from the Tegosil series which are intended to significantly increase the thermal conductivity of HCR- and even LSR-based silicone elastomers or to provide a simple way of improving their flame retardant properties by adding these compounds. Heat transfer characteristics from hot disc testing are presented and the reduced burn time in the UL 94 test demonstrates the improved flame resistance of the resulting elastomer formulations.

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