scholarly journals Heat insulation effect in solar radiation of polyurethane powder coating nanocomposite

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ali Akbar Azemati ◽  
Seyed Saeid Rahimian Koloor ◽  
Hossain Khorasanizadeh ◽  
Michal Petrů ◽  
Ghanbar Ali Sheikhzadeh ◽  
...  
Keyword(s):  
Zirconium Oxide ◽  
Heat Insulation ◽  
Radiation Heat Transfer ◽  
Weight Percent ◽  
Powder Coating ◽  
Transfer Coefficients ◽  
Aluminum Oxide Nanoparticles ◽  
Heat Transfer Coefficients ◽  
Insulation Effect ◽  
Emissivity Coefficient

AbstractThis study aims to improve polyurethane-based coating by modified zirconium oxide and aluminum oxide nanoparticles for preparing thin polymeric heat insulation coatings. In the first step, the nanoparticles were chemically modified with the silane coupling agent. Then, three different weight percent of modified nanoparticles (1, 3, and 5% w/w) were mixed with polyurethane, to prepare the nanocomposites, which were coated on metallic plate samples. Then, these plates are used to measure the radiation heat transfer coefficients, absorption coefficient in a region of short wavelengths (UV/VIS/NIR), the emissivity coefficient, and thermography of the samples in a region of long wavelengths (IR). Results showed that by adding the modified nanoparticles to the polyurethane matrix, absorption was decreased and the emissivity coefficient was increased. According to the thermography results, it was observed that the surface temperature of both samples with 3% w/w of nanoparticles had the minimum temperature compare to others. Minimum heat surface observed for 3% w/w of modified nano zirconium oxide.

Study on Radiation Properties of Polyurethane/Nano Zirconium Oxide Nanocomposite Coatings

2017 ◽  
Vol 894 ◽  
pp. 109-112 ◽  
Author(s):  
Ali Akbar Azemati ◽  
Hossein Khorasanizadeh ◽  
Behzad Shirkavand Hadavand ◽  
Ghanbar Ali Sheikhzadeh
Keyword(s):  
Heat Transfer ◽  
Zirconium Oxide ◽  
Radiation Heat Transfer ◽  
Polymeric Coatings ◽  
Transfer Coefficients ◽  
Weight Percentage ◽  
Heat Transfer Coefficients ◽  
Polyurethane Resin ◽  
Three Samples ◽  
Emissivity Coefficient

The present research studies on the effect of nanoparticles on polymeric coatings and heat transfer in them. For this purpose, three different weight percentage of nanozirconium oxide (1, 3 and 5%) were added to polyurethane resin and applied on metallic plates. To determine the radiation heat transfer coefficients, emissivity coefficient and thermography of the samples along a region of long wavelengths (IR) were measured. The results showed that by adding zirconium oxide nanoparticles to the polyurethane resin, the absorption and emissivity coefficient of coating in all three samples were improved compared to the coating without nanoparticles.

Effect of Insulated/Uninsulated Channel Walls on Heat Transfer From a Horizontal Finned Tube in a Vertical Channel

1987 ◽  
Vol 109 (2) ◽  
pp. 388-391 ◽  
Author(s):  
E. M. Sparrow ◽  
M. A. Ansari
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Vertical Channel ◽  
Finned Tube ◽  
Radiation Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Metallic Sheet ◽  
Rayleigh Numbers ◽  
Metal Wall

Measurements were made of the combined natural convection and radiation heat transfer from a horizontal finned tube situated in a vertical channel open at the top and bottom. In one set of experiments, both walls of the channel were heavily insulated, while in a second set of experiments, one of the insulated walls was replaced by an uninsulated metallic sheet. In general, the heat transfer coefficients were found to be lower with the metal wall in place, but only moderately. With the finned tube situated at the bottom of the channel, the differences in the heat transfer coefficients corresponding to the two types of walls were only a few percent. When the tube was positioned at the mid-height of the channel, larger differences were encountered, but in the practical range of Rayleigh numbers, the differences did not exceed 5 percent.

Heat Transfer and Flow Characteristics of Porous Matrices With Radiation as a Heat Source

1966 ◽  
Vol 88 (1) ◽  
pp. 69-76 ◽  
Author(s):  
J. P. Chiou ◽  
M. M. El-Wakil
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Radiation Heat Transfer ◽  
Flow Characteristics ◽  
Incident Radiation ◽  
High Porosity ◽  
Transfer Coefficients ◽  
Space Applications ◽  
Pressure Drops ◽  
Heat Transfer Coefficients

A theoretical and experimental study of the heat transfer and flow friction characteristics of matrices of high porosity, with incident radiation from one side resulting in an exponential heat source, and with air as a coolant, is reported. In the theory, a transient solution of simultaneous convection and radiation heat transfer equations has been worked out. Used with experimental data taken in the unsteady state, it resulted in the calculation of volumetric heat transfer coefficients by convection in the matrices. Correlations with Reynolds numbers, based on a characteristic length obtained by equating pressure drops to the sum of viscous and inertia resistance terms, were obtained. Using the more familiar hydraulic radius did not result in reducing the relationships to a unified form. The matrices used in the experiments were formed from slit-and-expanded aluminum foils, blackened to high radiant absorptivity. The results of the investigation are believed useful in many solar, nuclear, and space applications.

scholarly journals Experimental and Theoretical Study on the Heat Transfer Coefficients of Building External Surfaces in the Tropical Island Region

2019 ◽  
Vol 9 (6) ◽  
pp. 1063
Author(s):  
Yaping Cui ◽  
Jingchao Xie ◽  
Jiaping Liu ◽  
Peng Xue
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Vital Role ◽  
Calculation Model ◽  
Transfer Coefficients ◽  
Island Region ◽  
Tropical Island ◽  
Heat Transfer Coefficients ◽  
Low Energy Buildings ◽  
The Difference

China is actively promoting ocean territory construction, and how to design low-energy buildings to fit the unique climate of tropical island regions has received much attention. The heat transfer coefficient of a building external surface plays a vital role in calculating air-conditioning load accurately. To obtain reasonable heat transfer coefficients in the tropical island region, this study introduced a naphthalene sublimation experiment to conduct full-scale measurements on convective heat transfer coefficients (CHTCs) in the tropical island region, and proposed a simplified calculation model of evaporative heat transfer coefficients (EHTCs). Results indicated that the function expression between CHTC and wind speed was CHTC = 5.56 + 4.48u (R2 = 0.94), and it was validated to be reliable. Furthermore, compared with CHTCs and radiation heat transfer coefficients (RHTCs), the EHTC had a wider changing range, owing to rainfall effects. Moreover, whether evaporation was considered or not, the difference of total heat transfer coefficients (THTCs) on building external surfaces was 5.2 W/(m2·K) for the whole year, so evaporation cannot be ignored directly. Additionally, THTCs with consideration of evaporation in winter and summer were 33.4 W/(m2·K) and 38.9 W/(m2·K) severally, which are much larger than the recommended values in the Chinese standard. This study would make up for the lack of surface heat transfer coefficients in energy conservation design of tropical island buildings.

Exergy and sensibility analysis of each individual effect in a kraft multiple effect evaporator

TAPPI Journal ◽  
2019 ◽  
Vol 18 (10) ◽  
pp. 607-618
Author(s):  
JÉSSICA MOREIRA ◽  
BRUNO LACERDA DE OLIVEIRA CAMPOS ◽  
ESLY FERREIRA DA COSTA JUNIOR ◽  
ANDRÉA OLIVEIRA SOUZA DA COSTA
Keyword(s):  
Optimization Problem ◽  
Real Data ◽  
Kraft Pulping ◽  
Steam Temperature ◽  
Input Flow ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Multiple Effect ◽  
Sensibility Analysis ◽  
Exergetic Analysis

The multiple effect evaporator (MEE) is an energy intensive step in the kraft pulping process. The exergetic analysis can be useful for locating irreversibilities in the process and pointing out which equipment is less efficient, and it could also be the object of optimization studies. In the present work, each evaporator of a real kraft system has been individually described using mass balance and thermodynamics principles (the first and the second laws). Real data from a kraft MEE were collected from a Brazilian plant and were used for the estimation of heat transfer coefficients in a nonlinear optimization problem, as well as for the validation of the model. An exergetic analysis was made for each effect individually, which resulted in effects 1A and 1B being the least efficient, and therefore having the greatest potential for improvement. A sensibility analysis was also performed, showing that steam temperature and liquor input flow rate are sensible parameters.

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