Flat Plate Absorber Research Articles

Thermal performance of a simple design solar air heater with built-in thermal energy storage system

The thermal performance of a simple design solar air heater is presented. The conventional flatplate absorber is replaced by a set of tubes filled with a thermal-energy storage material. The proposed integrated system heat-transfer area and heat-transfer coefficient are increased and the heat loss is reduced. Based on a simple transient analysis, explicit expressions for the heater absorber and glass cover temperatures, effective heat gained, outlet air temperature, and the heater efficiency have been developed as a function of time. The integrated system performance curves are presented and a marked improvement in system performance is noticed over the conventional flat-plate heater system.

Thermal performance of a simple design solar air heater with built-in thermal energy storage system

The thermal performance of a simple design solar air heater is presented. The conventional flat plate absorber is replaced by a set of tubes filled with a thermal energy storage material. The proposed integrated system heat transfer area and heat transfer coefficient are increased, and the heat loss is reduced. Based on a simple transient analysis, explicit expressions for the heater absorber and glass cover temperatures, effective heat gained, outlet air temperature, and the heater efficiency have been developed as a function of time. The integrated system performance curves are presented, and a marked improvement on the system performance is noticed over the conventional flat plate heater system.

Performance of an intermittently tracked cylindrical parabolic trough

The distribution of local concentration ratios over a flat plate absorber used with an intermittently tracked cylindrical parabolic trough is studied for two values of the rim angle. The amount of energy collected by an intermittently tracked solar concentrator, oriented in various tracking modes, at different times of the year, for two typical latitudes, is also calculated. The results are presented graphically and discussed.

A study on thermosyphon solar water heater with parallel flat-plate collector

The performance of a thermosyphon solar water heater with parallel flat-plate absorber has been studied both theoretically and experimentally. The overall system thermal efficiency obtained with a parallel-plate is higher than for a tube-in-sheet absorber type. Theoretical values are in agreement with experimental data.

Heat Transfer Characteristics of a Back-Corrugated Absorber Surface for Solar Air Collectors

Current literature on solar air collectors emphasizes satisfactory heat transfer between the absorber and the flowing air as a major factor in overall performance. Heat transfer in the airflow passages, usually in or near the transitional flow range, is also influenced by entrance effects. The present study experimentally examines a back-corrugated absorber-convector composed of a rectangularly corrugated plate attached to the back side of a flat absorber plate with a high-temperature, high-strength adhesive. The upper surface is subjected to a heat flux from a blanket-type electric heater which simulates solar irradiation. The corrugated-plate configuration creates two parallel airflow channel types. The two channels have different geometries and, therefore, may have different heat transfer characteristics. An apparatus was designed to determine the local convective heat transfer coefficients along each of the channels. The results show that the back-corrugated absorber-convector has much better thermal performance than the simple flat-plate absorber-convector, primarily because of the increased convective heat transfer area.

An air-cooled solar collector using all-cylindrical elements in a low-loss body

A novel IX air-cooled solar collector has a phenolic polymer structural foam body, a black painted fiberglass mat absorber and a coplanar, parallel, close-packed array of evacuated cylindrical glass tubes for a cover. Modeling suggests, and measurements confirm, high efficiency performance as well as a substantial dispersion of performance characteristic arranged so that the specific temperature difference increases as the radiant intensity decreases. This dispersion suggests greatly improved cloudy weather performance. In a steady state simulation at full sun under northern midwinter conditions this collector can deliver a minimum of 1.9 times more heat per day to Glauber's Salt storage than can a IX double glazed water-cooled collector with a non-selective black flat absorber plate. Under cloudy conditions this advantage ratio rises to 12.1 at 5 13 sun. Effective heat collection continues at intensities as low as 3 13 sun. Under summertime conditions the collector can operate an absorption air conditioner at 6 13 sun.

Optimization of Flow Passage Geometry for Air-Heating, Plate-Type Solar Collectors

The effect of the choice of shape and dimensions of the air flow passages in plate-type, air-heating solar collectors is assessed. Particularly examined is their effect on the overall heat transfer coefficient Upf between the air stream and the plate, which has an important effect on collector efficiency. It is emphasized in this study that in comparing various designs of flow passage, they should be compared for the same pressure drop Δp suffered by the air in passing through the collector, and for the same mass flow rate m per unit of collector area. On the basis of this type of comparison, two main conclusions are drawn. First, when the length of the air flow passage L is made less than about 1 m, Upf increases dramatically with decreasing values of L. Second, outside the transition regime, the value of Upf for a V-corrugated absorber plate is from 47 to 300 percent higher than that for a flat absorber plate, depending on whether the flow is laminar or turbulent, and on whether the V-corrugated plate is thermally bonded to the back plate. The first conclusion has led to a proposal for a novel air-heating solar collector design, called the “short-path” design.

Cusp mirror—Heat pipe evacuated tubular solar thermal collector

A solar thermal collector was constructed based on an internal 1.15X cusp concentrator, thermal insulation involving a vacuum and selective absorber, and thermal transfer to a manifold via heat-pipe action. Performance of the collector was compared with that of an evacuated, selectively coated, flat-plate absorber equipped with flow-through heat transfer. It was shown that with single collector tubes, mirror losses lowered the optical efficiency of the cusp, heat-pipe collector below that of the flat plate, while the smaller absorber area of the heat pipe reduced thermal losses at absorber temperatures above ambient. Thus, a crossover in efficiency occurred such that the flat plate was more efficient at low ΔT H while the cusp-heat pipe was more efficient at high ΔT H . Testing of modules showed that manifold losses and gains could dominate these collector effects when the collector area approximately equaled the manifold area.

Numerical Analysis for Thermal Design of a Paraboloidal Solar Concentrating Collector

A paraboloidal solar concentrating collector in a non-planar configuration using reflecting materials of reflectance is 0.7 has been thermally designed and developed and at a 1metre focal distance in conjunction with a reverse flat plate absorber with black board paint (both selective and non selective coating) theoretically. To study optical and thermal performance tests like stagnation temperature (Tps), water temperature (Tw), plate temperature (Tp), thermal efficiency test (Xc), optical efficiency test (Xo), Heat transfer coefficient from surface to water (U), geometrical concentration ratio (C) and overall heat loss coefficient (U2) has been studied. The concentrator is placed such that all incident parallel rays of light intercepted by the concentrator aperture are reflected to a common focus. In this case the concentrator parabolic in shape. This communication presents the thermal design analysis of a CR- system. The results of some typical numerical calculations are shown graphically and their significance is discussed.Key words: Concentrating collector; mass flow rate; solar and thermal conversion.DOI: http://dx.doi.org/10.3329/ijns.v1i3.8824International Journal of Natural Sciences (2011), 1(3):68-74

The flat-plate absorber as a solar energy collector : Morse, R. N. and Czarnecki, J. T., Paper presented at the A.N.Z.A.A.S. Congress Solar Energy Symposium, Adelaide, Australia, Aug. 25, 1958. 10+ p. Illus.

The poor toughness of polylactic acid (PLA) has led to imposing certain restrictions on its use in various applications. In similar cases, introducing nanostructures is known to be a practical strategy for tailoring the mechanical features of polymeric materials. Herein, the contributory impacts of the presence of pristine and surface-treated boron nitride nanosheets on the mechanical behavior of PLA were explored through molecular dynamics simulations. Comparatively, it was observed that embedding 3 wt% untreated boron nitride nanosheet (BNNS) improved Young’s modulus and toughness of the polymer by 24.5% and 42%, respectively. Both chemical and physical surface treatments resulted in significantly lower polymer chains mobility during the deformation by intensifying interfacial interactions. Moreover, the obtained findings illustrated that applying either of chemical hydroxyl functional groups or PLA chains onto BNNS would contribute to the enhancement of PLA toughness. Among all the analyzed systems, approximately 5% functionalized nanosheets indicated the best toughening role by increasing PLA absorbed energy per unit volume by 131% on average although the enhancing role of chemically functionalized nanofiller was slightly better. The present findings could give a deeper insight into obtaining more efficacious designs for tailoring mechanical properties of polymer-based nanocomposites.

Pneumatic barker cuts log waste: ( Compressed Air Magazine, Vol. 53, No. 3)

This chapter provides an overview of solar power, and its advantages and disadvantages. Solar power has the general advantage of being a daily renewable source of power but the disadvantages of being erratic because of cloud cover, discontinuous because of the night and the seasons, and diffuse. It is collected in a number of ways. Flat-plate collectors are black absorbers through which a cooling medium (usually water) flows. For low-temperature operations (swimming-pool heaters), the absorber is usually bare, but for higher temperatures (domestic hot water or water distillation), the absorber is usually covered in glass at the front end and with insulation underneath. The energy absorbing is given by the Hottel–Whillier equation. Flat-plate absorbers are normally made of black plastic, for low-temperature use, or of copper or aluminum for high-temperature use. The latter are usually covered with a single layer of glass (double glazing is marginal because of the greater reflection) and backed with a weather-proof plastic. The front surface is usually painted with a special coating.