Experimental Thermal Efficiency Research Articles

Design and experiment of a new solar air heating collector

This paper presents the design and experiment of a CTAH (Concentrating Transpired Air Heating) system. A newly designed solar air heating collector comprised of an inverted perforated absorber and an asymmetric compound parabolic concentrator was applied to increase the intensity of solar radiation incident on the perforated absorber. An extensive literature review was carried out to find the vital factors to improve optical and thermal efficiency of solar air heating systems. A stationary optical concentrator has been designed and experimented. Experimental thermal efficiency remained high at higher air flow rates. The average thermal efficiency was found to be approximately 55%–65% with average radiation above 400 W/m2 for flow rates in the range of 0.03 kg/s/m2 to 0.09 kg/s/m2. Experimental results at air flow rates of 0.03 kg/s/m2 and 0.09 kg/s/m2 showed temperature rise of 38 °C and 19.6 °C respectively at a solar radiation intensity of 1000 W/m2. A comparative performance study shows the thermal performance of CTAH. As the absorber of the CTAH facing downward, it avoids radiation loss and the perforated absorber with tertiary concentrator reduces thermal losses from the system.

Experimental and Numerical Characterization of Ceramic and Metallic Absorbers under Lab-scale Conditions

Volumetric receiver technology has a huge potential for increase in the receiver and power block efficiencies by reducing the radiative thermal losses and increasing the temperature of the heat transfer fluid. With the aim of improving the thermal behavior of these types of receivers, CIEMAT-PSA is working at lab-scale on different configurations and geometries to optimize absorber behaviors. Furthermore, simplifiedComputational Fluid Dynamics (CFD)modelshave been developed to determine their feasibility for the prediction of the receiver experimental behavior and to analyze the heat transfer and thermal losses produced. As part of this work, experimental results ofboth a SiC absorber and an alloy-601 onetested under lab-scale conditions,under similar outlet receiver temperatures, were assessed. Moreover, the numerical results obtained froma two dimensional (2D) CFD model, which considers thermal equilibrium between solid and fluid phases, have been presented for the selected experimental data. The deviation between the experimental thermal efficiency and the numerical one was lower than 10%, showing a good agreement for a first-approach CFD model. The average thermal efficiency reached under lab-scale conditions was around 90% in both cases.

Thermal performance of a Stirling engine powered by a solar simulator

In this study, the performance of a beta type Stirling engine which works at relatively lower temperatures was investigated using 400 W and 1000 W halogen lamps as a heat source and helium as the working fluid. The working fluid was charged into the engine block and the pressure of the working fluid was ranged from 1 to 5 bars with 1 bar increments. The halogen lamps were placed into a cavity adjacent to the hot end of the displacer cylinder, which is made of aluminum alloy. In the experiments conducted with 400 W halogen lamp, the temperature of the cavity was 623 ± 10 K. The power, torque and thermal efficiency of the engine were determined to be 37.08 W, 1.68 Nm and 9.27%, at 5 bar charge pressure. For the 1000 W halogen lamp, the temperature of the cavity was determined to be 873 ± 10 K. The power, torque and thermal efficiency of the engine were determined to be 127.17 W, 3.4 Nm and 12.85%, at the same charge pressure. The experimental thermal efficiencies of the engine were also compared with thermodynamic nodal analysis.

Theoretical and experimental investigation on a liquid-gas ejector power cycle using ammonia-water

The purpose of this paper is to investigate a novel power cycle using low-temperature heat sources such as oceanic-thermal, biomass as well as industrial waste heat. Both a reheater and a liquid-gas ejector are used in this ammonia-water based cycle. Energy analysis and parametric analysis are performed to guide the theoretical performance and experimental investigation is done to verify the theoretical results. The results show that the generator pressure, heating source temperature and turbine outlet depressurization made by the ejector can affect the cycle performances. Besides, the experimental thermal efficiency is much lower than the theoretical one on account of the heat losses and irreversibility. Moreover, the performance of liquid-gas ejector is affected by primary flow pressure and temperature.

Experimental and Theoretical Study of a Parabolic Trough Solar Collector

An experimental and theoretical study has been conducted to determine the thermal efficiency of a parabolic trough solar collector. The experiments have been performed during winter and summer at Tikrit-Iraq. The solar radiation of Tikrit University was calculated theoretically and a theoretical study was performed by using FORTRAN 90 program. The dimensions and specifications of the collector were entered to the program to determine the theoretical thermal efficiency. It has been found the experimental thermal efficiency of collector is less than the theoretical one in percentage between (7-15) .So the increase in water mass flow rate leads to an increase in the thermal efficiency, and there is no significant change in thermal efficiency when the water mass flow rate becomes more than forty kilograms per hour.

Improving a conventional greenhouse solar still using sun tracking system to increase clean water yield

In this paper the performance of active sustainable solar still was studied. A conventional greenhouse solar still coupled with a flat-plate solar collector and photovoltaic (PV) system was built and tested. The sun tracking system was designed for the solar collector to track the sun position and to heat up the water flowing through the collector. This helps to further increase the water temperature in solar still basin and increase the daily yield of distilled water. The system consists of a solar still, a flat-plate collector, and a PV module to provide power supply to all the electrical components in the control system. Two-axis tracking was built to control the direction of the solar collector. The system was tested in Kuching (01°33′ N, 110°25′ E), (Sarawak, Malaysia) in different weather conditions. The obtained results show that there is a significant growth in the experimental thermal efficiency of the active solar still with sun-tracking (38.55%) as compared to the passive one (22.70%). Its efficiency is even higher as compared to active the non-sun-tracking solar stills (34.70%). This proves that solar collector with sun-tracking can indeed improve the performance of a solar still. In addition there is a small increase of 3.98% in the still efficiency for active solar still with sun-tracking (38.55%) as compared to the non-sun-tracking (34.70%). Comparisons between theoretical and experimental results are also presented.

A water-trickle solar collector

A trapezoidally corrugated aluminium water-trickle solar collector was constructed and tested under the climatic conditions of Ankara, Turkey (39° 57′N, 32° 53′E). Experimental thermal efficiency curves were constructed for both closed- and open-hole cases. For the open-hole case, a theoretical performance model was developed, which calculates iteratively the energy flows and temperature distributions. Effects of mass flow rate, ambient temperature, solar radiation intensity, and wind velocity on the calculated efficiency of the collector were studied. The major findings were discussed and the problems associated with the design and operation of the system were pointed out.

Thermal performance of the distributed flow, subatmospheric pressure, flat plate solar collector

Experimental thermal efficiencies for the distributed flow, subatmospheric pressure, flat plate solar collector are reported for a wide range of environmental and operational conditions, and for corrugated Filon and glass covers. Efficiencies for near normal solar incidence are correlated with a parameter formed from the difference between inlet fluid and air temperatures divided by incident solar energy. A mathematical model based on heat transfer concepts applicable to the collector yielded efficiencies which are in close agreement with the corresponding experimental efficiencies when the experimental measurements are inserted into the model.