Reducing thermal imbalances and flow nonuniformity in solar collectors through the selection of free flow area ratio

Energy ◽  
2020 ◽  
Vol 194 ◽  
pp. 116897 ◽  
Author(s):  
Juan M. García-Guendulain ◽  
José M. Riesco-Ávila ◽  
Martín Picón-Núñez
Keyword(s):  
Area Ratio ◽  
Free Flow ◽  
Solar Collectors ◽  
Flow Area ◽  
Selection Of ◽  
Flow Nonuniformity

Recirculation in an Annular-Type Jet Pump

1994 ◽  
Vol 116 (4) ◽  
pp. 735-740 ◽  
Author(s):  
Donald F. Elger ◽  
Sam. J. Taylor ◽  
Chyr P. Liou
Keyword(s):  
Recirculation Zone ◽  
Area Ratio ◽  
Secondary Flows ◽  
Jet Pump ◽  
Flow Area ◽  
Pump Design ◽  
A Value

For some annular-type jet pump applications, it is important to avoid formation of a recirculation zone in the mixing region. The goals of this research were to find (i) when recirculation occurs and (ii) the size and location of the resulting recirculation zone. Experiments were performed using air in a straight-walled, annular-type, ducted jet. Area ratio Aj/As varied from 0.39 to 0.89; here, A is flow area, and j and s identify the jet and secondary flows, respectively. Data showed that recirculation correlates with J, where J ≈ Pj/(Pj + Ps), and P is rate of momentum. For the area ratios studied, recirculation begins when J exceeds a value ranging from 0.89 to 0.94. This paper also presents data showing the recirculation zone boundaries and presents a discussion of jet pump design.

Effects of competitor spacing in a new class of individual-tree indices of competition: semi-distance-independent indices computed for Bitterlich versus fixed-area plots

2008 ◽  
Vol 38 (4) ◽  
pp. 890-898 ◽  
Author(s):  
Albert R. Stage ◽  
Thomas Ledermann
Keyword(s):  
Basal Area ◽  
Area Ratio ◽  
Individual Tree ◽  
Competitive Effects ◽  
New Class ◽  
Distance Effects ◽  
Fixed Area ◽  
Tree Increment ◽  
Competition Indices ◽  
Selection Of

We illustrate effects of competitor spacing for a new class of individual-tree indices of competition that we call semi-distance-independent. This new class is similar to the class of distance-independent indices except that the index is computed independently at each subsampling plot surrounding a subject tree for which growth is to be modelled. We derive the effects of distance for this class as the expected value over independent samples containing a particular subject tree. In a previous paper, we illustrated distance effects implicit in eight indices of the distance-dependent class. Here, we present distance effects of four semi-distance-independent indices: density, sum of diameters, basal area, and tree-area ratio; each determined for small fixed-area plots of 0.04 ha and for Bitterlich samples of 6 m2·ha–1. We show that several members of this new class have distance effects very similar to the distance-dependent class and should, therefore, be equally effective in accounting for competitive effects in individual-tree increment models. The comparisons should inform selection of competition indices and sampling designs for growth modelling.

Optimization of performance of PV panels and selection of best site for solar park in Pakistan

2022 ◽  
Author(s):  
Muhammad Uzair ◽  
Syed Umair Hassan Kazmi ◽  
Muhammad Uzair Yousuf ◽  
Syed Asad Ali Zaidi
Keyword(s):  
Solar Energy ◽  
Tilt Angle ◽  
High Energy ◽  
Azimuth Angle ◽  
Low Energy ◽  
Solar Collectors ◽  
Maximum Value ◽  
Effects Of Temperature ◽  
Selection Of

To incorporate solar energy efficiently into a country, it is needed to know the optimal tilt and azimuth angle of the solar collectors' location. Also, to build a solar park, it is necessary to know the most suitable and high-energy generating place inside a country, thus saving time and money. This study analyzed collector geometry for Karachi in particular and Pakistan in general. Karachi has the potential of 339.36 kW-hr/m2/annum energy at an annually optimal fixed tilt of 26°. In case collector geometry had to be changed in Karachi, a range of 40° azimuth angle and 20° tilt angle from its maximum value is available. The power produced in this case would only have a difference of 1%. Optimal yearly and monthly tilt of most of the locations of Pakistan (300+) were calculated. Through them, it was revealed that the Optimal Tilt of Pakistan follows the value of latitude closely. Generally, changing the tilt angle monthly is recommended for areas that produce more energy, while fixed annual tilt could be suitable for low energy-producing regions. Effects of temperature were also incorporated while finding the energy produced by the photovoltaic (PV) panels.

Head recovery at submerged abrupt conduit outlets

1988 ◽  
Vol 15 (2) ◽  
pp. 272-274 ◽  
Author(s):  
James A. Kells ◽  
C. D. Smith
Keyword(s):  
Pipe Flow ◽  
Open Channel ◽  
Classical Problem ◽  
Head Loss ◽  
Area Ratio ◽  
Shape Effect ◽  
Velocity Head ◽  
Flow Area ◽  
Downstream Flow ◽  
Primary Variable

The question of an abrupt expansion in a pipeline from one diameter to a larger diameter is a classical problem dealt with in most undergraduate fluid mechanics texts. A problem not dealt with, but which is far more common in practice, is the abrupt expansion at the terminal end of a pipe where the flow expands into an open channel downstream. It is often assumed that the entire velocity head for the pipe flow is lost. This is not necessarily true. In this paper, the experimental study of an abrupt expansion into an open channel is reported. Several different channel shapes are used in an attempt to determine shape effect, if any. It is concluded that the primary variable affecting the head loss is the ratio of the upstream to downstream flow area, called the area ratio. Key words: abrupt expansion, conduit outlet, head recovery, head loss, area ratio.

scholarly journals A Non-Dimensional Conceptual Design Procedure for the Vaneless Volutes of Radial Inflow Turbines

1991 ◽  
Author(s):  
A. Whitfield ◽  
A. B. Mohd Noor
Keyword(s):  
Mach Number ◽  
Conceptual Design ◽  
Swirling Flow ◽  
Design Procedure ◽  
Area Ratio ◽  
Working Fluid ◽  
Flow Area ◽  
Cross Sectional ◽  
The Absolute ◽  
Inlet Conditions

The requirements for the volute of a radial inflow turbine are that it should collect the working fluid, deliver it to the turbine rotor as efficiently as possible and provide the desired rotor inlet conditions. The overall performance requirements of the turbine leads to the rotor design and the identification of the desired flow conditions at rotor inlet in terms of the magnitude and direction of the absolute Mach number, see Whitfield (1990). The volute must then be designed to ensure that the desired rotor inlet conditions are attained. A non-dimensional conceptual design procedure for a vaneless turbine volute is described. Based on a knowledge of the magnitude and direction of the absolute Mach number at rotor inlet the overall dimensions of the volute in terms of the radius ratio and flow area ratio are first established. The overall design is then developed to provide the variation of the volute centroid radius and area ratio with azimuth angle. A trapezoidal cross-sectional shape is then used to establish the outer dimensions of the volute. The non-dimensional design procedure assumes a one-dimensional compressible flow and as such relies on the empirical specification of the dissipation of angular momentum, the dissipation of energy, and the deviation of the swirling flow from that of a free vortex. The effect of the uncertainties associated with the empirical data on the volute design geometry is assessed.

Selection of materials for flat plate solar collectors

1980 ◽  
Vol 2 (1) ◽  
pp. 65-82 ◽  
Author(s):  
H. J. Mcqueen ◽  
M. M. Shapiro ◽  
D. Feldman
Keyword(s):  
Flat Plate ◽  
Solar Collectors ◽  
Selection Of

GUIDANCE ON AREA OF CREATED TEARS FOR AORTIC FENESTRATION TREATMENT BASED ON COMPUTATIONAL FLUID DYNAMICS

2021 ◽  
pp. 2150037
Author(s):  
XIAOXI HOU ◽  
CHUBIN OU ◽  
KAZUHIKO HANZAWA ◽  
XILEI DAI ◽  
YI QIAN
Keyword(s):  
Fluid Dynamics ◽  
Risk Factor ◽  
Acute Aortic Dissection ◽  
Fluid Dynamic ◽  
False Lumen ◽  
Area Ratio ◽  
Dynamic Approach ◽  
Ideal Case ◽  
Blood Flows ◽  
Selection Of

Aortic fenestration (AF) uses puncture and a dilation balloon to create a tear in the intimal flap, which can directly relieve ischemia syndrome and reduce hypertension in the false lumen. The selection of a dilation balloon as well as the area of the created tear applied in reality depend on clinical experience, so we aim to provide a quantitative guidance and reference for doctors to better plan the treatment of aortic fenestration. In this study, the area of the created tear was virtually enlarged to at least 10 different values for four cases including one ideal case, and a computational fluid dynamic approach was applied to simulate blood flows in the aorta. The area ratio (AR) between the created tear and entry tear was introduced to express the enlargement of the created tear. The quantitative hemodynamic results indicate that the AR should be controlled to be larger than 7.0, but not too big to obtain the best treatment for acute aortic dissection (AD) case. Additionally, we assessed that AR might also be a risk factor for the prediction of dissection propagation.

ALGORITHM FOR THE CONJUGATION OF TWO-DIMENSIONAL IN THE PLAN OF UNIFORM AND RADIAL FLOWS

2020 ◽  
pp. 18-21
Author(s):  
Victor Kokhanenko
Keyword(s):  
Flow Model ◽  
Theoretical Method ◽  
Free Flow ◽  
Two Dimensional ◽  
Flow Area ◽  
Simple Waves ◽  
Experimental Parameters ◽  
Calculation Results ◽  
Hodograph Plane ◽  
Two Dimensional Flow

The algorithm of the theoretical method proposed by the authors using the speed hodograph plane and simple waves for solving the problem of coupling a two-dimensional flow in terms of flow is considered. This technique allows you to determine the boundaries of the free flow of a turbulent flow and its parameters in the flow area. it is revealed that using both planes physical OXYZ and hodograph G (,) it is possible to solve the problem uniquely analytically. All verification calculations were performed in the MathCad package. The calculation results showed a satisfactory convergence of model and experimental parameters in the free flow model, which does not exceed 10 % by error before the flow expansion within  = 7;  = B/b.

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