Cylindrical Trough Research Articles

Numerical analysis of tubular solar still with rectangular and cylindrical troughs for water production under vacuum

This study compares and contrasts the desalination efficiency of tubular solar still using cylindrical and rectangular troughs when operating under a vacuum. For this, a two-dimensional code was created using the Comsol Multiphysics. The mass and heat transfer, inside the tubular solar still with the two different types of troughs, was simulated parametrically. The effect of the radius of the cylindrical trough, the square rib of the rectangular trough and the vertical elevation of the trough on heat and mass transfer were investigated at the same volume of seawater introduced initially. The numerical results revealed that the efficiency of the water productivity using cylindrical trough is significantly better than with rectangular trough when it is placed in the middle of the tubular shell. The opposite case of the 2 types of troughs is established when the trough advances towards the upper side of the glass cover where the condensation occurs.

Factors affecting the performance enhancement of a parabolic trough collector utilizing mono and hybrid nanofluids: A mini review of recent progress and prospects

Utilizing solar power has become more common in most regions among several renewable energy sources that are currently available, including geothermal, wind, biomass, and tidal etc. Hence, researchers are turning their attention to solar energy studies. Solar thermal collectors have the ability to capture solar energy. Various solar collectors have already been modelled, designed, built, and tested to perform in a variety of temperature ranges, including low temperature collectors (compound parabolic collectors 60-240°C, evacuated tube collectors 50-200°C, and flat plates 30-80°C), medium temperature collectors (parabolic trough 40-400°C, cylindrical trough collector 60-300°C, and linear Fresnel reflectors 60-250°C), and high temperature collectors (heliostat field collector 150–2000°C and parabolic dish reflector 100–1500°C). The parabolic trough collectors (PTCs) have been discovered to be the most popular between the various solar collectors in applications such as the steam generation, the delivery of process heat, and desalination. Since about three decades ago, various theoretical and experimental research studies have been carried out in order to improve the thermal and optical efficiency of the PTC system. This review studies the parameters influencing the PTC thermal performance and the enhancements to improve the design modification, optical, and thermal properties used in PTC.

Experimental and theoretical analyses of a double-cylindrical trough solar concentrator

Parabolic trough, Fresnel, heliostat mirror, or dish-type collectors are used to obtain high temperature in solar thermal applications. The operation of this system is similar to that of a Fresnel collector, except for its reflective mirror, which is cylindrical and not flat. The experiments were carried out in the solar energy system manufactured for producing hot water, superheated water, and steam in the cylindrical trough solar concentrator. According to the test results, the thermal power of the system and the average thermal efficiency of the collector were a maximum of 15 kW and approximately 35 %, respectively.

Increase the heating capacity of solar water heaters through two conditions of placing paraffin in copper tubes

Nowadays, Energy is an essential requirement for daily activities. Indonesians use solar energy for various activities such as electricity, water heaters, and dryers. Solar collectors are devices that absorb solar energy and convert it into heat energy. Solar energy heats copper pipes and water passes through heat tubes induces an increase in water temperature. The increase in heating capacity in this experiment was carried out by adding paraffin (as thermal storage material) into a tube in a solar collector. Solar water heaters equipped with solar collectors (called cylindrical trough collectors) have been developed in this experiment. Paraffin placed in the copper tube with two conditions. They are called Collector A and Collector B. The effect of two conditions of placing paraffin in copper tubes on the water-out temperature has been studied in this experiment. The result shows that the highest water temperature found with 56°C in collector A. It is due to the highest solar radiation intensity also record at 1,289 W/m2 (1:00 PM). While Collector B only produces the water-out temperature of 52°C at 1:00 PM. The conclusion shows that the position of paraffin in tubes with Collector A can increase the water-out temperature in the solar water heating system if compared with the collector.

An experimental investigation of a parabolic concentrator solar tracking system integrated with a tubular solar still

This study describes the performance of three different experiments under the climatic conditions of Hail city (27.5°N, 41.7°E) in Saudi Arabia by using a tubular solar still (TSS) with a rectangular trough filled with a black cloth and saturated by raw water in the first experiment; a TSS with a half cylindrical trough without clothing in the second experiment, while in the third experiment TSS of the second experiment was integrated with a parabolic concentrator-solar tracking system (PCST-TSS). Results show a high potential of using PCST-TSS compared to conventional TSS. The obtained yields were 0.28, 0.214 and 1.66L/day for 0.059m2 TSS area (4.71, 3.6 and 3.53L/m2day) for the three experiments with daily efficiencies of 36.5%, 30.5% and 28.5% respectively. The PCST-TSS yield was increased by 676% with 45.5% cost reduction per liter (CPL). This promising technique is suitable for house roofs and small communities located in remote areas.

Design and Fabrication of Solar Cylindrical Trough Collector with Parabolic Shape

Design and Fabrication of Solar Cylindrical Trough Collector with Parabolic Shape

Numerical Investigation of Wind Flow around a Cylindrical Trough Solar Collector

The goal of this study is to model the effects of wind on Cylindrical Trough Collectors (CTCs). Two major areas are discussed in this paper: 1) heat losses due to wind flow over receiver pipe and 2) average forces applied on the collector’s body. To accomplish these goals a 2D modeling of CTC was carried out using commercial codes with various wind velocities and collector orientations. Ambient temperature was assumed to be constant at 300 K and for specific geometries different meshing methods and boundary conditions were used in various runs. Validation was done by comparing the simulation results for a horizontal collector with empirical data. It was observed that maximum force of 509.1 Newton per Meter occurs at +60 degrees. Nusselt number is almost the constant for positive angles while at negative angles it varies considerably with the collector’s orientation.

Comparison of optical performances of sea-shell trough solar concentrators

An investigated sea-shell solar concentrator is non-imaging, asymmetric, stationary and has long trough. This concentrator consists of a parabolic, cylindrical trough reflector, a flat double-sided flat absorber (for heat production), and a flat aperture. Three concentrators of such design were investigated by specular solar ray tracing with the software CATIA. They differ in the location of the absorber inside the concentrator. The optical efficiency of direct solar ray transfer inside these concentrators was investigated for different solar ray altitudes at the concentrator aperture for the concentrators installed in Kragujevac, Serbia. For the solar ray altitudes between 50° and 69.75°, the highest optical efficiency was obtained at the solar concentrator where the absorber contains the focus line of the parabola reflector. For the solar ray altitudes between 21° and 50°, the highest optical efficiency was obtained by the solar concentrator where the absorber contains the vertex line of the parabola reflector.

Solar ray transfer inside sea-shell stationary trough solar concentrator

A sea-shell stationary trough solar concentrator for heat production consists of a parabolic, cylindrical trough reflector, a flat double-sided absorber, and a flat aperture. By ray tracing with the software catia, the optical efficiency (the efficiency of solar ray transfer inside the concentrator) is investigated for different solar ray altitudes at the concentrator aperture and different kinds of reflector shells. For the concentrator installed in Kragujevac, Serbia, the highest optical efficiency is obtained for the solar ray altitudes between 45° and 69.75°.

Exergy analysis of the solar cylindrical-parabolic cooker

For the first time the simple solar parabolic cooker (SPC), of the cylindrical trough shape, is analysed from the exergy viewpoint. The paper presents the methodology of detailed exergy analysis of the SPC, the distribution of the exergy losses, and, on the example of the cooker surfaces, explains the general problem of how the exergy loss on any radiating surface, should be determined, if the surface absorbs many radiation fluxes of different temperatures. An imagined surface was used in the considerations to close the system of the cooker surfaces. It was shown that optimization is needed, to increase the energy and exergy efficiencies of the cooker. Equations for heat transfer between the three surfaces: cooking pot, reflector and imagined surface making up the system, were derived. The model allowed for theoretical estimation of the energy and exergy losses: unabsorbed insolation, convective and radiative heat transfer to the ambient, and additionally, for the exergy losses: the radiative irreversibilities on the surfaces, and the irreversibility of the useful heat transferred to the water. The exergy efficiency of the SPC, was found to be relatively very low (∼1%), and to be about 10 times smaller than the respective energy efficiency which is in agreement with experimental data from the literature. The influence of the input parameters (geometrical configuration, emissivities of the surfaces, heat transfer coefficients and temperatures of water and ambience) was determined on the output parameters, the distribution of the energy and exergy losses and the respective efficiencies.

Conformational instability of the lowest triplet state of the benzene nucleus. II. p-Xylene, the influence of substituents

A calculation of the potential-energy surface of the lowest triplet state of p-xylene as a function of the S8(ρ,φ) distortion coordinate of the benzene skeleton has been made to learn more about the influence of substituents on the vibronically induced distortion of benzene in its metastable triplet state.The results show the hexagonal conformation of the benzene nucleus in p-xylene to be unstable with respect to distortions along S8(ρ,φ). In contrast with benzene, for which a flat, virtually cylindrical trough was calculated, the lowest triplet state of p-xylene shows a preference for quinoidal conformations. The variation in energy with the position of the methyl groups in the quinoidal structure is insignificant within the accuracy of the calculation.

Conformational instability of the lowest triplet state of the benzene nucleus. I. The unsubstituted molecule

Experiments on benzene have established that its lowest triplet state (3B1u) is conformationally unstable owing to vibronic coupling with the next higher state (3E1u). This instability was found to be critically dependent on the influence of a crystal field. An analogous vibronic coupling is to be expected in the singlet manifold, but here no direct evidence is available for a conformational instability. The distortion behavior of benzene is of importance for the interpretation of its photophysical and photochemical properties. We have therefore determined the potential-energy surfaces of the 1,3B1u and 1,3E1u states along the two-dimensional distortion coordinate S8(ρ,φ) using ab initio multireference single and double excitation-configuration-interaction calculations. The results show that for both B1u states the hexagonal conformation is unstable and lies 800 cm−1 above a wide, virtually cylindrical trough. A calculation of the vibrational spacing in the 3B1u state yields good agreement with the experimentally observed frequency. The calculation of intensities in the absorption and emission spectrum for this state qualitatively agrees with the experiment. An estimate is made of the interaction of the excited molecule with neighboring molecules in a crystal, which indicates that the crystal-field induced energy variations in the trough should be of the order of 10 cm−1. Combination of our calculations with experimental data shows that the vibronic coupling in the B1u states of benzene should not be looked upon as a static coupling in which the molecule is permanently distorted to one conformation but as a dynamic one in which the molecule makes excursions over the entire potential-energy surface.

A note on drag reduction in separated Stokes flows

The slow linear shear flow past a cylindrical trough can lead to separation. Here we show that a reduction in the total drag experienced by the flow is possible because of the separation, though the magnitude is very small.

Analysis of a Concentrating Solar Collector for Heating Air

ABSTRACT PERFORMANCE test results and a theoretical model are presented for a concentrating solar collector used for heating air. The collector has a cylindrical trough reflector with a linear receiver, and is capable of two axis tracking. Measured instantaneous and day-long efficiencies for heating ambient air are presented for serveral tracking modes; they range up to 45% and depend on air flow rate.

New spreader for the preparation of gradient layers in thin-layer chromatography

The preparation of gradient layers with reproducible separating properties suffers from various difficulties, so the Desaga gradient spreader, which has been known since 1964, has been redesigned. The new spreader allows the suspension to be passed directly through a special dividing wall into the cylindrical trough where mixing takes place. The layers thus prepared are highly sensitive and yield reproducible results. If chromatography is carried out transverse to the gradient (T-gradient), sensitive and substance-specific curves are obtained; chromatography parallel to the gradient improves separations to give selective focusing.

The capacity and field of a cylindrical trough with a plane conductor in the axial plane of symmetry

The transformation z = b cn (Kw/U) is taken as basic, and from this the complex potential, field and capacity of a condenser, consisting of an infinite cylindrical trough and an infinite plane conductor of finite width situated in the axial plane of symmetry, are obtained by the method of inversion.