Performance Of Flat Plate Research Articles

Consideration of fouling by scaling in the sizing of flat plate solar collector networks

In this work, the effects of fouling on the performance of flat plate solar collector networks that operate with water as the thermal fluid are studied, and design considerations are put forward to be used in the sizing of these systems from the thermal and hydraulic points of view. The quantification of the effects produced by scaling is carried out through a mathematical model that predicts the deposition on the walls of the tubes. The model considers that CaCO3 is the only compound present in the fouling layer. Results indicate that for a volumetric flow rate of 3.78 l/min and assuming a CaCO3 concentration of 250 ppm, in a period of six months, the maximum outlet temperature that can be obtained in a day falls 1.5 °C and the pressure drop increases four times. It is shown that it is advisable to design a network of solar collectors considering scaling. The case study indicates that to supply a total flow rate of 48 l/min at a temperature of 70 °C, the design considering scaling requires 220 collectors and a volumetric flow rate of 4.8 l/min per line with a total annualized operating cost of $343,300 Mx.

Basic Understanding of Airfoil Characteristics at Low Reynolds Numbers ()

A computational study has been conducted on various airfoils to simulate flows at Reynolds numbers () primarily between and to provide understanding and guidance for MAV and other low-Reynolds-number designs. The computational fluid dynamics tool used in this study is a Reynolds-averaged Navier–Stokes solver with a Spalart–Allmaras turbulence model and a correlation-based laminar–turbulent boundary-layer transition model. The airfoils investigated in this study include NACA 0009, NACA 0012 (conventional and reversed configuration), Clark-Y, flat plate airfoils (1, 3, and 5% thickness), and thin cambered plates (3, 6, and 9% camber). Airfoils were examined for lift and drag performance as well as surface pressure and flow field characteristics. In general, it is observed that below the Reynolds number of , lift and drag characteristics for most airfoils cannot be assumed to be constant with the Reynolds number. Below the Reynolds number of , cambered plate airfoils are shown to have better lift and drag characteristics than thick conventional airfoils with rounded-leading edges. Flat plate performance is generally invariant to the Reynolds number, but performance improves as thickness is decreased for a given Reynolds number.

Performance of Flat-Plate and Compound Parabolic Concentrating Solar Collectors in Underfloor Heating Systems

There is a growing interest in using solar energy in underfloor heating systems. However, the large areas required for the installation of solar thermal collector's array can be discouraging, especially in the apartment buildings where the apartment's roof is a common area. The objective of this study is to investigate the possibility of using compound parabolic concentrating (CPC) solar collectors instead of the commonly used flat-plate collectors (FPCs) in such systems. It is aimed to explore the feasibility of area reduction required by the collectors. Second, the temperature profiles of circulating water loop and the concrete slabs are sought to be examined. The system consists of solar thermal collectors, a storage tank, and circulation of water to transport the heat to four similar floor slabs. The CPC collector outlet fluid's temperature can reach a maximum of 95 °C, compared to 70 °C obtained from the FPCs. The results from the simulations show that a 2 m2 CPC collector array can perform satisfactorily to match the job of an 8 m2 FPC array, obtaining the same required circulating water's temperature in the slabs.

Development and Validation of a Mathematical Model for Ice Storages with Heat Exchangers that can be De-iced

The development and validation of a mathematical model of an ice storage tank with heat exchangers that can be de-iced is presented. The ice storage model was developed for heating applications using combined solar thermal and heat pump systems. The influence of a growing ice layer on the performance of flat plate and coil type heat exchangers was theoretically analyzed. Experiments were conducted with a laboratory scale ice storage of 1 m3. Several operating modes were investigated in order to validate the model under all conditions of interest. The model predicted successfully most of the operating modes for the main variables such as heat exchanger outlet temperature and energy transferred, mass of ice produced and melted, and time of ice formation. However, the melting of ice showed a great dependency on uncertain model parameters used for the calculation.

Reshoring effects on deflections of multi-shored flat plate systems under construction

RC flat plates that have no flexural stiffness by boundary beams may be governed by a serviceability as well as a strength condition. A construction sequence and its impact on the distributions of construction loads among slabs tied by shores are decisive factors influencing immediate and long term performances of flat plate. Over-loading and tensile cracking in early-aged slabs significantly increase the deflection of a flat plate system under construction. A reshoring work may be helpful in reducing slab deflections by controlling the vertical distributions of construction loads in a multi-shored flat plate system. In this study, a change of construction loads by reshoring works and its effects on deflections of flat plate systems under construction are analyzed. The slab construction loads with various reshoring schemes are defined by a simplified method, and the practical calculation of slab deflections with considering construction sequences and concrete cracking effects is applied. From parametric studies, the reshoring works are verified to reduce construction loads and slab deflections.

Comparative study of the performances of four photovoltaic/thermal solar air collectors

An extensive investigation of the thermal, electrical, hydraulic and overall performances of flat plate photovoltaic/thermal (PV/T) air collectors has been made. Four popular designs are considered with the air flowing either over the absorber (Model I) or under it (Model II) and on both sides of the absorber in a single pass (Model III) or in a double pass fashion (Model IV). Heat balance equations are written for each model and are numerically solved, incorporating measured climate data. The effects of air specific flow rate and the selectivity of the absorber plate and PV cells on the performances have been examined. It is found that under similar operational conditions, the Model I collector has the lowest performance, while the other models exhibit comparable thermal and electrical output gains. Nevertheless, the Model III collector demands the least fan power, followed by Models IV and II. It is also shown that selective properties are inappropriate for these PV/T collectors due to the resultant reduction in the generated PV energy, especially at low flow rates. The study provides valuable information regarding the design and operation of such types of PV/T air collectors.

A Novel Low-Cost Diffuser for High-Performance Centrifugal Compressors

A novel, low-cost diffuser based upon discrete pipe drillings has been developed for high-performance centrifugal compressors. These discrete drillings are arranged in symmetrical array to mutually intersect in a radial plane so that a gradual transition from the open vaneless space at rotor tip to the individual throats of each pipe is implicitly defined. To draw a comparison, alternate cambered-vane and flat-plate diffusers were defined using the best available yet practical thinking. With a nominal 5:1 stage pressure ratio, rotor, 81.8 percent efficiency was obtained with the “pipe” diffuser at 5.42 pressure ratio. This efficiency level exceeded the best cambered-vane and flat-plate performance by 6.8 and 8.8 percent, respectively. Further testing with a second rotor yielded 81.3 percent efficiency at 6:1 pressure ratio for the pipe diffuser and 73 percent efficiency at 6:1 for the cambered-vane diffuser.