scholarly journals A Transient Thermography Method to Separate Heat Loss Mechanisms in Parabolic Trough Receivers

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Marc Röger ◽  
Peter Potzel ◽  
Johannes Pernpeintner ◽  
Simon Caron
Keyword(s):  
Heat Loss ◽  
Temperature Measurements ◽  
Thermal Excitation ◽  
Transient Method ◽  
Parabolic Trough ◽  
Selective Coating ◽  
Transient Thermography ◽  
Energy Balances ◽  
Glass Envelope ◽  
Loss Mechanisms

This paper describes a transient thermography method to measure the heat loss of parabolic trough receivers and separate their heat loss mechanisms. This method is complementary to existing stationary techniques, which use either energy balances or glass envelope temperature measurements to derive overall heat losses. It is shown that the receiver heat loss can be calculated by applying a thermal excitation on the absorber tube and measuring both absorber tube and glass envelope temperature signals. Additionally, the emittance of the absorber selective coating and the vacuum quality of the annulus can be derived. The benefits and the limits of the transient method are presented and compared to the established stationary method based on glass envelope temperature measurements. Simulation studies and first validation experiments are described. A simulation based uncertainty analysis indicates that an uncertainty level of approximately 5% could be achieved on heat loss measurements for the transient method introduced in this paper, whereas for a conventional stationary field measurement technique, the uncertainty is estimated to 17–19%.

Heat Loss Measurement and Analyses of Solar Parabolic Trough Receiver

2013 ◽  
Vol 291-294 ◽  
pp. 127-131
Author(s):  
Jian Feng Lu ◽  
Jing Ding ◽  
Jian Ping Yang ◽  
Kang Wang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Loss ◽  
Boundary Region ◽  
Heat Losses ◽  
Experimental Measurements ◽  
Wind Condition ◽  
Parabolic Trough ◽  
Loss Measurement ◽  
Glass Envelope

The heat loss of vacuum receiver plays critical important role in solar parabolic trough system. In this paper, experimental measurements and calculation models were conducted to investigate the heat loss of solar parabolic trough receiver with receiver length of 10.2 m and diameter of 0.120 m. In general, the heat loss of receiver decreased with the receiver wall temperature, while it can approach minimum under special wind condition. The heat loss of receiver mainly included the heat loss of glass and boundary region, and the heat losses of receiver, glass region and boundary region with tube temperatures of 176.2oC were respectively 987.1 W, 762.2 W and 224.9 W. Outside the glass envelope, the convection and radiation both play an important role in the heat loss of receiver, while the heat transfer is mainly dependent upon the radiation inside the glass envelope. In addition, the heat losses of convection outside the glass and radiation inside the glass from calculation very well agreed with the experimental data.

Developments in High Temperature Parabolic Trough Receiver Technology

Solar Energy ◽  
2004 ◽  
Author(s):  
Henry Price ◽  
Mary Jane Hale ◽  
Rod Mahoney ◽  
Carin Gummo ◽  
Robert Fimbres ◽  
...  
Keyword(s):  
High Temperature ◽  
Solar Energy ◽  
High Efficiency ◽  
Failure Rates ◽  
Significant Issue ◽  
Parabolic Trough ◽  
Parabolic Trough Collector ◽  
Selective Coating ◽  
Linear Receiver ◽  
Glass Envelope

The parabolic trough linear receiver is one of the primary reasons for the high efficiency of the Luz parabolic trough collector design used at the Solar Energy Generating Systems (SEGS) plants. Experience from the SEGS plants has shown that the reliability and lifetime of the parabolic trough receiver tube is the most significant issue for existing and future parabolic trough plants. Although highly efficient, the original Luz receiver tubes experienced high failure rates (approximately 4% to 5% per year). Failures included vacuum loss, glass envelope breakage, and degradation of the selective coating. This paper reviews receiver failure rates, the primary failure causes at two of the SEGS plants, and discusses receiver technology developments during the last several years that focus on improving the reliability of parabolic trough receivers. Data are provided on the performance and reliability of a new commercially available trough receiver.

Experimental Tests on Parabolic Trough Receivers Employing Bifurcated, Air-Filled Annuli

2011 ◽  
Author(s):  
Hany Al-Ansary ◽  
Obida Zeitoun
Keyword(s):  
Natural Convection ◽  
Heat Loss ◽  
Experimental Tests ◽  
Receiver Design ◽  
Parabolic Mirror ◽  
Parabolic Trough ◽  
Insulating Material ◽  
The Mean ◽  
Mean Time ◽  
Glass Envelope

A new parabolic trough receiver design is tested. In this design, the annulus of the receiver is bifurcated such that the half facing away from the parabolic mirror, and receives minimal concentrated sunlight, is filled with an insulating material, whereas the half receiving the majority of the concentrated sunlight is allowed to be filled with air. By insulating the outward facing half of the annulus, heat loss by radiation is minimized. In the mean time, heat loss by natural convection due to the presence of air in the lower half of the annulus is expected to be significantly subdued, since the hotter air will be closer to the heat collection element, which is at a generally higher position than the glass envelope. Experimental tests were performed on roof-mounted troughs which utilize receivers with air-filled annuli. The system consists of two identical but independent rows. The receivers in the first row have normally air-filled annuli, while the receivers in the second row have annuli that are half-filled with an insulating material and half-filled with air. The results have shown that the thermal performance of the modified receiver was indeed superior to conventional receivers with air-filled annuli.

Experimental Analysis of Overall Thermal Properties of Parabolic Trough Receivers

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Eckhard Lüpfert ◽  
Klaus-J. Riffelmann ◽  
Henry Price ◽  
Frank Burkholder ◽  
Tim Moss
Keyword(s):  
Thermal Properties ◽  
Experimental Analysis ◽  
Operating Temperature ◽  
Field Measurements ◽  
Heat Losses ◽  
Thermal Loss ◽  
Parabolic Trough ◽  
Energy Balances ◽  
Good Agreement ◽  
Glass Envelope

The heat loss of a receiver in a parabolic trough collector plays an important role in collector performance. A number of methods have been used to measure the thermal loss of a receiver tube depending on its operating temperature. This paper presents methods for measuring receiver heat losses including field measurements and laboratory setups both based on energy balances from the hot inside of the receiver tube to the ambient. Further approaches are presented to measure and analyze the temperature of the glass envelope of evacuated receivers and to model overall heat losses and emissivity coefficients of the receiver. Good agreement can be found between very different approaches and independent installations. For solar parabolic trough plants operating in the usual 390°C temperature range, the thermal loss is around 300W∕m receiver length.

Evaporative Heat Loss Mechanisms of the Newborn Calf, Bos Taurus

1968 ◽  
Vol 124 (2) ◽  
pp. 83-88 ◽  
Author(s):  
J.R.S. Hales ◽  
J.D. Findlay ◽  
D. Robertshaw
Keyword(s):  
Heat Loss ◽  
Bos Taurus ◽  
Evaporative Heat Loss ◽  
Loss Mechanisms

scholarly journals Characterization and Corrections for Clamp-On Fluid Temperature Measurements in Turbulent Flows

2018 ◽  
Vol 10 (3) ◽  
Author(s):  
Bijan Nouri ◽  
Marc Röger ◽  
Nicole Janotte ◽  
Christoph Hilgert
Keyword(s):  
Fluid Flow ◽  
Turbulent Flows ◽  
Power Plants ◽  
Measurement Data ◽  
Temperature Measurements ◽  
Correction Function ◽  
Acceptance Testing ◽  
Fluid Temperature ◽  
Parabolic Trough ◽  
Operation Conditions

A clamp-on measurement system for flexible and accurate fluid temperature measurements for turbulent flows with Reynolds numbers higher than 30,000 is presented in this paper. This noninvasive system can be deployed without interference with the fluid flow while delivering the high accuracies necessary for performance and acceptance testing for power plants in terms of measurement accuracy and position. The system is experimentally validated in the fluid flow of a solar thermal parabolic trough collector test bench, equipped with built-in sensors as reference. Its applicability under industrial conditions is demonstrated at the 50 MWel AndaSol-3 parabolic trough solar power plant in Spain. A function based on large experimental data correcting the temperature gradient between the measured clamp-on sensor and actual fluid temperature is developed, achieving an uncertainty below ±0.7 K (2σ) for fluid temperatures up to 400 °C. In addition, the experimental results are used to validate a numerical model. Based on the results of this model, a general dimensionless correction function for a wider range of application scenarios is derived. The clamp-on system, together with the dimensionless correction function, supports numerous combinations of fluids, pipe materials, insulations, geometries, and operation conditions and should be useful in a variety of industrial applications of the power and chemical industry where temporal noninvasive fluid temperature measurement is needed with good accuracy. The comparison of the general dimensionless correction function with measurement data indicates a measurement uncertainty below 1 K (2σ).

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