Thermal performance of building components. Dynamic thermal characteristics. Calculation methods

2008 ◽  
Keyword(s):  
Thermal Performance ◽  
Thermal Characteristics ◽  
Calculation Methods ◽  
Building Components

Total Solar Energy Transmittance vs. Dynamic Thermal Characteristics of Non-Transparent Building Components

2014 ◽  
Vol 899 ◽  
pp. 77-82
Author(s):  
Roman Rabenseifer
Keyword(s):  
Solar Radiation ◽  
Solar Energy ◽  
Thermal Performance ◽  
Thermal Characteristics ◽  
Heat Gain ◽  
Solar Heat ◽  
Interior Spaces ◽  
Building Components ◽  
Solar Heat Gain ◽  
The Difference

Occasionally, there are suggestions from professional public to use the total solar energy transmittance coefficient, g (solar factor), to describe not only transparent, but also opaque structures, particularly with regard to overheating of the under-roof spaces. The standard EN 410:1998 (Glass in building - Determination of luminous and solar characteristics of glazing) introduces the g-value as the sum of primary solar heat gain, g1, due to the transparency of the glazing and the secondary solar heat gain, g2, due to the absorption of solar radiation and its conversion into heat conduction and radiation over the total incident solar heat flux, φe. Nevertheless the value of g1 may have zero or nearly zero value, e.g. in case of non-transparent glass. In addition to it, the standard ISO 15099:2003 (Thermal performance of windows, doors and shading devices - Detailed calculations) introduces equation for calculation of the frame g-value (actually the frame total solar energy transmittance), where window frames are clearly opaque components. What is then the difference between glass and "standard" opaque wall or roof? Why is in the latter case always introduced zero and in the first one some value different from zero? Won't it be practical, especially in time of large existing opportunities of computer use, to implement the use of g-values also in case of ordinary opaque structures and express their resistance to the absorption and conversion of solar radiation and thus overheating the adjacent interior spaces? This paper attempts, using EN ISO 13786 (Thermal performance of building components - Dynamic thermal characteristics - Calculation methods) and computer-aided models of transient heat transfer, to explain why the suggestion of using of the g-value in case of opaque components is not entirely correct and, why priority should be given to the dynamic thermal characteristics specified in this standard.

An Investigation of the Thermal Performance of a Novel Axial Grooved Heat Pipe

2012 ◽  
Vol 580 ◽  
pp. 223-226
Author(s):  
K.M. Yang ◽  
N.H. Wang ◽  
C.H. Jiang ◽  
L. Cheng
Keyword(s):  
Surface Tension ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Thermal Characteristics ◽  
High Heat ◽  
Input Power ◽  
Thermal Coefficient ◽  
Total Thermal Resistance ◽  
High Heat Transfer ◽  
Axial Temperature

Heat pipes are devices capable of very high heat transfer and have been widely used in many thermal management applications. An experimental investigation of thermal characteristics of heat pipe with axial ‘‘Ω”-shaped grooves was presented in this paper. The effects of angle of inclination and input power on thermal performance of heat pipe were investigated, the surface tension and gravity both impacted the fluid flow in heat pipe, and which one was dominating was analyzed. Experimental results indicate that the working temperature of heat pipe, the axial temperature differences and the maximum axial temperature differences increase when increasing the input heat flux. The total thermal resistances become smaller with the input power increasing, but become bigger with the angle of inclination increasing. And the trend of the thermal coefficient of heat pipe reverses that of the total thermal resistance. The influence of gravity on thermal performance is weaker than that of the surface tension.

scholarly journals Thermal performance in a tubular heat exchanger with deltawinglets

2018 ◽  
Vol 192 ◽  
pp. 02062
Author(s):  
Pattarapan Tongyote ◽  
Pongjet Promvonge ◽  
Nattawoot Depaiwa ◽  
Withada Jedsadaratanachai
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Performance ◽  
Thermal Characteristics ◽  
Test Tube ◽  
Turbulent Regime ◽  
Airflow Rate ◽  
Tubular Heat Exchanger ◽  
Experimental Heat ◽  
Constant Wall Heat Flux

The paper presents an experimental heat transfer enhancement study in a tubular heat exchanger fitted with delta-winglets. The experimental work was conducted by varying the airflow rate in the test tube having a constant wall heat-flux for turbulent regime, Reynolds number (Re) from 5200 to 23,000. Effects of three pitch ratios (PR=P/D=1.5, 2.0 and 3.0) and two attack angles, α = 45° and 60°, of the winglets at a single blockage ratio (BR=b/D = 0.15) on thermal characteristics are examined. The experimental results show that the winglet-inserted tube yields, respectively, the heat transfer, friction factor and thermal performance in the form of TEF around 1.99–4.08, 4.9–14.3 times higher than the plain tube and 0.85–1.85, depending on the operating condition.

Analysis of dynamic thermal performance of the walls in residential buildings in Serbia

2020 ◽  
pp. 095440622094189
Author(s):  
Saša M Kalinović ◽  
Jelena M Djoković
Keyword(s):  
Thermal Performance ◽  
Residential Buildings ◽  
Thermal Characteristics ◽  
Optimal Solution ◽  
Temperature Oscillation ◽  
Thermal Capacity ◽  
Paper Analysis ◽  
Wall Structure ◽  
Total Thickness ◽  
External Temperature

In this paper, analysis of dynamic thermal performance of multilayer insulation wall in residential buildings in Serbia is performed. Considering that the final goal is to build a residential structure with the highest level of efficiency, that is, with the lowest energy consumption for heating and cooling, it is necessary to determine good thermal characteristics of a multilayer wall. The first type of walls, which were analyzed had the same structure with different thicknesses of individual layers. The second type of analyzed walls had the same structure, but the thermo-insulating layers occupied different positions. The third type of walls had different structures, but the same total thickness. Based on the results presented in the paper, it can be concluded that in walls with similar structures, the same total thickness and different thicknesses of individual layers, there are differences in the external temperature variation shift. The position of the thermal insulation layer for the same wall structure does not significantly affect the change in temperature oscillation caused by the change in the outside temperature. Changing the wall structure, however, has significant influence on the thermal capacity. This analysis offers the possibility to choose the optimal solution for the wall structure with the highest energy efficiency.

Experimental investigation on the thermal performance of Si micro-heat pipe with different cross-sections

2017 ◽  
Vol 31 (30) ◽  
pp. 1750279 ◽  
Author(s):  
Mohammad Hamidnia ◽  
Yi Luo ◽  
Xiaodong Wang ◽  
Congming Li
Keyword(s):  
Thermal Management ◽  
Thermal Performance ◽  
Cross Sections ◽  
Integrated Circuit ◽  
Thermal Characteristics ◽  
Cost Savings ◽  
Working Fluid ◽  
Cross Sectional ◽  
Si Substrates ◽  
Silicon Based

Increasing component densities of the integrated circuit (IC) and packaging levels has led to thermal management problems. Si substrates with embedded micro-heat pipes (MHPs) couple good thermal characteristics and cost savings associated with IC batch processing. The thermal performance of MHP is intimately related to the cross-sectional geometry. Different cross-sections are designed in order to enhance the backflow of working fluid. In this experimental study, three different Si MHPs with same hydraulic diameter and various cross-sections are fabricated by micro-fabrication methods and tested under different conditions of fluid charge ratios. The results show that the trapezoidal MHP associated with rectangular artery which is charged with 40% of vapor chamber’s volume has the best thermal performance. This silicon-based MHP is a passive approach for thermal management, which could widen applications in the commercial electronics industry and LED lightings.

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