A Simulation of the Thermal Performance of a Small Solar Chimney Already Installed in a Building

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
J. Arce ◽  
J. P. Xamán ◽  
G. Álvarez ◽  
M. J. Jiménez ◽  
R. Enríquez ◽  
...  
Keyword(s):  
Flow Rate ◽  
State Energy ◽  
Theoretical Study ◽  
Volumetric Flow Rate ◽  
Metallic Plate ◽  
Balance Equations ◽  
Solar Chimney ◽  
Concrete Wall ◽  
Glass Cover ◽  
Heat Absorber

In this paper we present a theoretical study of a small solar chimney. The dimensions of the solar chimney channel are 1.95 m high, 1.70 m wide, and 0.24 m deep. The channel of the solar chimney has in its backside a metallic plate as a solar heat absorber, and it is attached to a concrete wall, which acts as storage and thermal insulation. On the front part of the chimney a glass cover is used to decrease the heat losses to the exterior. For this theoretical study, the steady-state energy balance equations were solved numerically for each element of the solar chimney. The results showed the temperature profiles for the glass cover, the air inside the channel, and the metallic plate. Also, the air mass flow rate was determined. When solar irradiance increases from 100 to 700 W/m2, the maximum instantaneous efficiency of the system varies from 28% to 37%, and also, the volumetric flow rate increases from 61 to 147 m3/h.

A Simulation of the Thermal Performance of a Small Solar Chimney Already Installed in a Building

2010 ◽  
Author(s):  
J. Arce ◽  
J. P. Xama´n ◽  
G. Alvarez ◽  
M. J. Jime´nez ◽  
R. Enri´quez ◽  
...  
Keyword(s):  
State Energy ◽  
Theoretical Study ◽  
Glass Plate ◽  
Numerical Code ◽  
Metallic Plate ◽  
Balance Equations ◽  
Solar Chimney ◽  
Concrete Wall ◽  
Heated Air ◽  
Heat Absorber

In this paper we present the theoretical and experimental study of a small solar chimney. The dimensions of the solar Chimney channel are 1.95 m high, 1.70 m width and 0.24 m depth. The channel of the solar chimney has in its backside a metallic plate as a solar heat absorber, and it is attached to a concrete wall, which acts as a storage and thermal isolation. On the front part of the chimney there is a glass plate used to decrease the heat losses to the exterior. Because the metallic plate is heated, air circulates from the lower side to the top side of the chimney channel. For the theoretical study, the steady state energy balance equations were solved for each element of the solar chimney following the methodology proposed by Ong in 2003 [8]. A numerical code was developed and reduced to cases of literature in order to validate it (Ong and Chow in 2003 [12]). The results showed the temperature distributions of the glass, the air inside the channel and the metallic plate. Also, the air mass flow rate was determined. For an hourly Irradiance of 400 W/m2, the efficiency of the solar chimney decreased from 38 to 15% as the height of the chimney increased from 0.25 to 1.95 m.

Stack Effect Correlation for Rooftop Solar Chimneys

2011 ◽  
Author(s):  
Mohammad H. Naraghi ◽  
Romain Cellard du Sordet
Keyword(s):  
Energy Balance ◽  
Air Temperature ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Direct Influence ◽  
Balance Equations ◽  
Solar Chimney ◽  
Stack Effect ◽  
Rooftop Solar

A correlation for calculating flow rate of air in solar chimneys is developed. This correlation is based on the variables that have the most direct influence on the volume flow rate of air through a solar chimney. These variables include: the spacing between the absorbing wall and glass (chimney depth), absorbing wall temperature, inlet air temperature and height of chimney. The slope of the rooftop solar chimney, for the range of typical roofs (30°–60°) has very little influence on the flow rate. The solution of energy balance equations for various components of the solar chimney along with the newly developed correlation shows a significant improvement of the results compared to the existing stack effect correlation.

scholarly journals Theoretical Analysis of a New Design of a Concentration Based Solar Distiller

2021 ◽  
Vol 234 ◽  
pp. 00003
Author(s):  
Mokhtar Mohammed ◽  
Taha Janan Mourad
Keyword(s):  
Energy Balance ◽  
Theoretical Analysis ◽  
Brackish Water ◽  
Theoretical Study ◽  
Balance Equations ◽  
New Device ◽  
Numerical Resolution ◽  
Matlab Code ◽  
Glass Cover ◽  
Theoretical Performance

This paper includes a theoretical study of energy balance for all parts of new design of solar concentration distiller using a parabolic concentrator with a half-cylinder basin. Our goal is to analyze the thermal efficiency of the new device to use in the Morocco's Rabat-Sale-Kenitra region. The methodology concentrates on solving the thermal collector's energy balance equations whose components are the glass cover, the brackish water and half-cylinder absorber. Numerical resolution of the energy balance equations was performed using a MATLAB code based on the method of 4th order Runge-Kutta. The results show a good theoretical performance of the new device.

Computational and theoretical research of the injector block function

2020 ◽  
pp. 123-126
Author(s):  
В.В. Кожемякин ◽  
Р.А. Иванов ◽  
Е.С. Игнатьева
Keyword(s):  
Hydraulic Resistance ◽  
Cross Section ◽  
Flow Rate ◽  
Pressure Dependence ◽  
Theoretical Study ◽  
Water Jet ◽  
Theoretical Research ◽  
Sudden Expansion ◽  
Operating Modes ◽  
Coefficient Of Hydraulic Resistance

Работа посвящена расчетно-теоретическому исследованию работы блока инжекторов. Рассмотрен пароводяной струйный аппарат, который применяется в качестве средства циркуляции теплоносителя первого контура. Подвод дополнительного потока осуществляется на цилиндрическом участке с внезапным расширением сечения через перемычку. Для достижения поставленной цели разработана программа для ЭМВ, в которой смоделирована зависимость давления от нагрузки в контуре, а также проведено расчетно-теоретическое исследование влияние гидравлического сопротивления на расход перемычки. В данной работе рассмотрены только рабочие режимы, т.е. все инжекторы работают как насосы. В ходе работы было установлено, что при нагрузке в 30% увеличиваются коэффициенты инжекции пароводяного струйного аппарата, но характер работы перемычек не меняется. Так же было установлено, что расход через перемычку меняется не пропорционально коэффициенту гидравлического сопротивления перемычки. The paper is devoted to the computational and theoretical study of the injector block operation. A steam-water jet apparatus is considered, which is used as a means of circulating the primary circle coolant. The additional flow is supplied on the cylindrical section with a sudden expansion of the cross-section through the bridge. To achieve this goal, a computer program was developed that modeled the pressure dependence on the load in the circuit, and also a theoretical study of the influence of hydraulic resistance on the flow of the jumper was conducted. In this paper, only operating modes are considered, i.e. all the injectors function as pumps. In the process of the research, it was found that at a load of 30%, the injection coefficients of the steam-water jet apparatus increase, but the nature of the work of the jumpers does not change. It was also found out that the flow rate through the jumper does not change in proportion to the coefficient of hydraulic resistance of the jumper.

The pumping characteristics of screw rotors. I. The theory of calculation of the pumping capacity of screw rotors

1987 ◽  
Vol 52 (2) ◽  
pp. 357-371 ◽  
Author(s):  
František Rieger
Keyword(s):  
Present State ◽  
Flow Rate ◽  
Volumetric Flow Rate ◽  
Screw Rotor ◽  
Screw Rotors

This paper summarizes the present state of the theory of calculation of the pumping capacity of screw rotors. The calculation starts from the equation for the volumetric flow rate of the flow between two unconfined plates modified by correction coefficients obtained from the relationships for the flow rate in simpler geometrical configurations to which the screw rotor may be, under certain circumstances, reduced.

Thermal Performance Analysis of a Rectangular Longitudinal Finned Solar Air Heater With Semicircular Absorber Plate

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Satyender Singh ◽  
Prashant Dhiman
Keyword(s):  
Thermal Performance ◽  
Numerical Solutions ◽  
Solar Air Heater ◽  
Duct Flow ◽  
Balance Equations ◽  
Absorber Plate ◽  
Ansys Fluent ◽  
Air Heater ◽  
Glass Cover ◽  
Good Agreement

Thermal performance of a single-pass single-glass cover solar air heater consisting of semicircular absorber plate finned with rectangular longitudinal fins is investigated. The analysis is carried out for different hydraulic diameters, which were obtained by varying the diameter of the duct from 0.3–0.5 m. One to five numbers of fins are considered. Reynolds number ranges from 1600–4300. Analytical solutions for energy balance equations of different elements and duct flow of the solar air heater are presented; results are compared with finite-volume methodology based numerical solutions obtained from ansys fluent commercial software, and a fairly good agreement is achieved. Moreover, analysis is extended to check the effect of double-glass cover and the recycle of the exiting air. Results revealed that the use of double-glass cover and recycle operation improves the thermal performance of solar air heater.

POLARON IN A QUANTUM DOT UNDER AN ELECTRIC FIELD

2007 ◽  
Vol 21 (24) ◽  
pp. 1635-1642
Author(s):  
MIAN LIU ◽  
WENDONG MA ◽  
ZIJUN LI
Keyword(s):  
Quantum Dot ◽  
Electric Field ◽  
Field Intensity ◽  
Ground State Energy ◽  
Ground State ◽  
Electric Field Intensity ◽  
State Energy ◽  
Theoretical Study ◽  
The Moment ◽  
Transformation Methods

We conducted a theoretical study on the properties of a polaron with electron-LO phonon strong-coupling in a cylindrical quantum dot under an electric field using linear combination operator and unitary transformation methods. The changing relations between the ground state energy of the polaron in the quantum dot and the electric field intensity, restricted intensity, and cylindrical height were derived. The numerical results show that the polar of the quantum dot is enlarged with increasing restricted intensity and decreasing cylindrical height, and with cylindrical height at 0 ~ 5 nm , the polar of the quantum dot is strongest. The ground state energy decreases with increasing electric field intensity, and at the moment of just adding electric field, quantum polarization is strongest.

Pahoehoe and aa in Hawaii: volumetric flow rate controls the lava structure

1990 ◽  
Vol 52 (8) ◽  
pp. 615-628 ◽  
Author(s):  
Scott K Rowland ◽  
George PL Walker
Keyword(s):  
Flow Rate ◽  
Volumetric Flow Rate
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