scholarly journals Analysis of the influence of the ambient temperature on the energy efficiency of solar modules by application of empirical correlations for natural convection

2021 ◽  
Vol 19 (2) ◽  
pp. 540
Author(s):  
Shahir Fleyeh Nawaf ◽  
Mohammad Omar Salih ◽  
Younis Nather Younis
Keyword(s):  
Energy Efficiency ◽  
Natural Convection ◽  
Ambient Temperature ◽  
Empirical Correlations

scholarly journals An empirical correlation of ambient temperature impact on PV module considering natural convection

2020 ◽  
Vol 19 (2) ◽  
pp. 627
Author(s):  
Kamil Jadu Ali ◽  
Ahmed Hasan Mohammad ◽  
Ghanim Thiab Hasan
Keyword(s):  
Natural Convection ◽  
Solar Radiation ◽  
Ambient Temperature ◽  
Analytical Model ◽  
Incident Angle ◽  
Tracking System ◽  
Empirical Correlations ◽  
Pv Module ◽  
Pv Modules ◽  
Temperature Impact

<p><span>In this paper, the effect of the ambient temperature on the PV modules for different angles of inclinations and different intensities of the solar radiation on the surface of the PV module is considered by using empirical correlations for natural convection. An analytical model based on the energy balance equilibrium between the PV module and the environment conditions has been used. Also an expression for calculating the electric power of silicon PV modules in a function of the ambient temperature, the intensity of the solar radiation, the incident angle of the solar radiation to the surface of the PV module and the efficiency of the PV modules at STC conditions have been used. By comparing the obtained both results, it can be seen that the largest deviation between the power values obtained by the analytical model and expression is about (5 %). The results obtained indicates that in the case of a small number of PV modules corresponding to the required number for an average household, it is more economical to invest additional resources in increasing the PV module's surface area than in case of the PV module with sun tracking system. </span></p>

scholarly journals Analysis of operating conditions of a cooling installation with carbon dioxide

2019 ◽  
Vol 100 ◽  
pp. 00005
Author(s):  
Artur Bieniek ◽  
Łukasz Mika ◽  
Jan Kuchmacz
Keyword(s):  
Carbon Dioxide ◽  
Energy Efficiency ◽  
High Pressure ◽  
Thermodynamic Properties ◽  
Ambient Temperature ◽  
Air Temperature ◽  
Operating Conditions ◽  
Efficiency Ratio ◽  
Summer Period ◽  
International Regulations

In response to international regulations, natural refrigerants such as carbon dioxide are more and more frequently used in the refrigeration industry. Due to thermodynamic properties, R-744 is used in the transcritical cycle as an individual refrigerant. In the hereby article, high pressure of CO2 and air temperature values were analysed. The measurements were conducted on the gas cooler side and involved external air temperature values in the summer period between 1 June to 30 September 2018. The “Booster” installation was used in one of Polish supermarkets. Correlations required to determine the optimal pressure of carbon dioxide depending on ambient temperature were presented in the article. The equations presented hereby allowed to maximize the energy efficiency ratio. An optimal high pressure for one of the correlations from literature was calculated on the basis of the measurement of ambient temperature. Actual and optimal pressure values of carbon dioxide were compared in the analysed period of time.

Natural Convection in a Horizontal Cylinder with Partial Heating: Energy Efficiency Analysis

2020 ◽  
Vol 29 (6) ◽  
pp. 1531-1550
Author(s):  
Akram Mazgar ◽  
Khouloud Jarray ◽  
Fadhila Hajji ◽  
Fayçal Ben Nejma
Keyword(s):  
Energy Efficiency ◽  
Natural Convection ◽  
Horizontal Cylinder ◽  
Efficiency Analysis ◽  
Partial Heating ◽  
Energy Efficiency Analysis

scholarly journals Some flow patterns within ventilation strategy coupled to energy efficiency

2019 ◽  
Vol 88 (1) ◽  
pp. 10902
Author(s):  
Souad Morsli ◽  
Rachid Bennacer ◽  
Mohammed El Ganaoui ◽  
Harry Ramenah ◽  
Alain Carmasol
Keyword(s):  
Energy Efficiency ◽  
Natural Convection ◽  
Air Quality ◽  
Thermal Comfort ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Forced Flow ◽  
Cooling Power ◽  
Moderate Reynolds Number ◽  
Mixing Ability

Energy and buildings are increasingly becoming subjects for investigations, especially for the indoor air quality domain coupled to energy demand. The physics of fluids flowing inside enclosures bring basic models to understand and build better schemes. This paper is devoted to studying ventilation strategies in regards to Indoor Air Quality (IAQ) and energy efficiency in floor refreshing houses. A room model is considered in a simplified level, as a cavity heated on the external sidewall and cooled on the bottom ground surface. The external air injector is at variable positions and interacting with the needed cooling power; the air quality (mixing ability) and thermal comfort are also studied. The cooling efficiency inside the considered volume and the average air temperature are analyzed for a given temperature difference characterizing the natural convection level (Rayleigh number, Ra = 106) and a horizontal ventilation (moderate Reynolds number Re = 102). An obtained complex flow structure indicates that the natural convection and the forced flow (ventilation) act directly on the resulting patterns, mixing ability, heat exchange which in a straight line affect the thermal comfort and in fine the energy cost (cooling requirement).

A 3D Numerical Simulation of a Cylindrical Towel Heater With Symmetric and Asymmetric Heating

2011 ◽  
Author(s):  
Daniel Murray ◽  
Jose´ L. Lage
Keyword(s):  
Natural Convection ◽  
Prandtl Number ◽  
Ambient Temperature ◽  
Ambient Air ◽  
Three Dimensions ◽  
Bottom Surface ◽  
Heating Process ◽  
Cylinder Wall ◽  
Symmetric Heating ◽  
Asymmetric Heating

In this study a cylindrical towel heater filled with air is simulated numerically in three-dimensions, with the cylinder being heated electrically from the side. The objective is to investigate the efficiency of the heating process as to maintain the towel at a certain temperature, higher than the ambient temperature (ambient temperature outside the heating cylinder), with the heating being symmetric or asymmetric. The process is modeled analytically assuming the towel as a homogeneous and isotropic porous medium, saturated with air, and enclosed by the cylinder. The cylinder wall is heated with a constant, symmetric or asymmetric heat flux, with the bottom surface assumed adiabatic and the top isothermal in equilibrium with the ambient air. The porous-continuum mass, momentum and energy equations for the natural convection inside the cylinder, derived through volume averaging the continuum equations with appropriate closure equations, are written in nondimensional form and solved numerically using the finite-volume method. A parametric study is then performed, after identifying suitable ranges for the parameters involved, to identify the effects of the several controlling parameters, namely the cylinder heating strength (the Rayleigh number), the towel permeability (the Darcy number), form coefficient (the dimensionless form coefficient), and thermal diffusivity (modified Prandtl number). The results, in terms of volume-averaged and surface-averaged temperatures and Nusselt numbers, indicate that the Darcy and Rayleigh numbers have a predominant effect on the natural convection process inside the cylinder, with the inertia coefficient and the modified Prandtl number having lesser influence on the results. For the asymmetric heating configuration, the resulting Nusselt number is higher while the volume-averaged temperature is lower, as compared to the symmetric heating. Hence, a symmetric heating is preferable if a high average towel temperature is the objective of the heater. If a more efficient heating process is sought, on the other hand, than the asymmetric option should be the best alternative.

scholarly journals Comparative investigation of performance of gas dryer and two other types of domestic clothes dryers

2020 ◽  
Author(s):  
Xiao-Mei Huang ◽  
Lian-Sen Xiong ◽  
Yan-Wen Zheng ◽  
Hui-Qing Liu ◽  
Yi-Zhen Xu ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Energy Consumption ◽  
Ambient Temperature ◽  
Heat Pump ◽  
Thermal Energy ◽  
Dry Mass ◽  
Primary Energy ◽  
Comparative Investigation ◽  
Ambient Temperatures ◽  
Moisture Extraction

Abstract The moisture extraction rate (MER) and energy efficiency of domestic gas clothes dryers, heat-pump clothes dryers and electric clothes dryers were assessed. The assessment was performed with regard to five indices: the MER, specific MER, specific thermal energy consumption for dehumidification (mSPC), energy efficiency (ηt) and primary energy efficiency (η1). The effects of the dry mass of clothes (mBD) and the ambient temperature on the performance of the clothes dryers were evaluated. The experiments were divided into two parts. In the first part, the ambient temperature was 20°C, and mBD was set as 1.5, 2.5, 3.5, 4.5 and 6 kg. In the second part, mBD was 3.5 kg, and the performance of the dryers was tested at ambient temperatures of 5, 7.5, 10, 12.5, 15 and 20°C. The experimental results indicated that the gas dryer had the highest MER the heat-pump dryer had the best performance with regard to energy conservation and all three types of dryers had a higher MER and energy efficiency when the ambient temperature increased. The performance of the gas dryer was lower than that of heat-pump dryer when the temperature was 20°C. But when the temperature was &lt; 9.5°C, the primary energy efficiency of the gas dryer was higher than that of the heat-pump dryer.

Prediction of Thermal Performance of Wire-Bonded Plastic Ball Grid Array Package for Underhood Automotive Applications

2003 ◽  
Vol 125 (3) ◽  
pp. 447-455 ◽  
Author(s):  
K. Ramakrishna ◽  
J. R. Trent
Keyword(s):  
Thermal Conductivity ◽  
Natural Convection ◽  
Ambient Temperature ◽  
Thermal Performance ◽  
Ball Grid Array ◽  
Automotive Applications ◽  
Molding Compound ◽  
Wide Range ◽  
Plastic Ball ◽  
Plastic Ball Grid Array

Thermal performance of a three chip, overmolded wire-bonded plastic ball grid array (WB-PBGA) package with four layer substrate attached to a 1.52-mm-thick, four-layer (2s2p), FR4 printed wiring board (PWB) has been evaluated under horizontal natural convection conditions for underhood automotive applications as a function of ambient temperature, package design parameters, and thermophysical properties of the package and PWB materials. A two-tier modeling approach, which accurately accounts for multidimensional heat transfer effects caused by substrate features such as vias and C5 solder joints, has been developed and implemented. In this methodology, the effect of small features is first characterized using a detailed micromodel from which an effective thermal conductivity is computed. The effective thermal conductivity is implemented in the global model thereby excluding the small features in the global model. The actual stackups of the package and PWB have been used in the computations to accurately determine the in-plane heat spreading. Using this methodology for automotive underhood applications, a parametric study of thermal performance of the WB-PBGA package has been carried out. This study shows that: 1. The maximum junction temperature rise above ambient, ΔT, decreases with increase in ambient temperature by 30% as the ambient temperature increases from 23 to 125°C. 2. ΔT decreases by 20% as the emissivity of the molding compound and the PWB surfaces increases from 0 (no radiative loss) to 0.8 under natural convection conditions. 3. The decrease in ΔT is small (∼7%) as the thermal conductivity of the die attach material varies over a wide range. 4. ΔT decreases by 30% as the thermal conductivity of the molding compound is varied over a wide range. 5. ΔT decreases by 45% as the thermal conductivity of the substrate increases (i.e., as the number of vias in the substrate increase) from no vias case to densely populated vias.

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