The Experts below are selected from a list of 168 Experts worldwide ranked by ideXlab platform

Gang Pei - One of the best experts on this subject based on the ideXlab platform.

  • Performance evaluation and analyses of novel parabolic trough evacuated collector tubes with spectrum-selective Glass Envelope
    Renewable Energy, 2019
    Co-Authors: Qiliang Wang, Honglun Yang, Jingyu Cao, Gang Pei
    Abstract:

    Abstract Evacuated collector tubes (ECTs), the key components of the parabolic trough collector, suffer considerable heat loss at high operating temperature. Based on the characteristic of uneven distribution of solar irradiance around the absorber tube, novel ECTs covered with infrared (IR)-reflectors on the partial area of Glass Envelope were proposed to effectively reduce the heat loss and enhance the performance. Two kinds of ideal IR-reflectors, namely, the first one with a fixed cutoff wavelength, the second one with a variable and optimal cutoff wavelength were proposed. A real material of transparent conductive oxide (TCO) film was also used as an IR-reflector in novel ECTs for the analysis. The mathematical models relying on spectral parameter calculation method were established for comprehensively investigating the overall performance of the novel ECTs. Moreover, the influences of TCO film reflectivity and emissivity on the ECTs were investigated. Results demonstrated that the novel ECTs with TCO films, the first ideal films, and the second ideal films achieved obvious superior thermal performance compared with the conventional ECTs. Their relative heat loss reductions at an absorber temperature of 600 °C reached 18.7, 25.3, and 43.8%, the heat-collecting efficiencies were relatively enhanced by 7.2, 10.8, and 16.7%, respectively.

  • A spectral self-regulating parabolic trough solar receiver integrated with vanadium dioxide-based thermochromic coating
    Applied Energy, 1
    Co-Authors: Qiliang Wang, Honglun Yang, Gang Pei, Boxu Shen, Junchao Huang, Hongxing Yang
    Abstract:

    Abstract A significant decrease in the solar-thermal conversion efficiency of parabolic trough collectors occurs at high operating temperatures, mainly due to the massive radiant heat loss from the parabolic trough solar receiver incurred in this case. In this paper, a novel parabolic trough solar receiver integrated with vanadium dioxide-based thermochromic coating is proposed to effectively reduce the radiant heat loss and improve the overall performance of solar receivers. The thermochromic layer, deposited on the Glass Envelope’s inner surface in the negative thermal-flux region, has a reversible transition from a monoclinic (M) phase to a rutile (R) phase at the critical temperature of 68 °C. The occurrence of the phase transition in the thermochromic coating induces beneficial self-regulation of the spectrum-selectivity characteristics of the Glass Envelope, i.e., transmittance, reflectance, and absorptance (emittance) of Glass Envelope to solar and infrared radiation, for enhancing the thermal performance of solar receivers. Comprehensive heat transfer models based on the finite volume and spectral radiant heat transfer methods are established in this study. It is validated the models can predict the thermal performance of the solar receivers with high accuracy. In this framework, the total heat loss, thermal efficiency, and exergy efficiency of parabolic trough collector systems integrated with the proposed novel solar receivers are investigated and analyzed. Besides, the effects of transmittance of thermochromic coating (M phase) and emittance of thermochromic coating (R phase), two key parameters, on the overall performance of proposed solar receivers are also studied. The results show that no matter under the M phase or R phase, the thermochromic coating can play unique advantages to improve the thermal performance of the proposed solar receivers. The heat loss and thermal efficiency of the proposed solar receivers are effectively reduced and enhanced by 18.2% and 4.8% at the absorber temperature of 600 °C and inlet fluid temperature of 580 °C, respectively.

Qiliang Wang - One of the best experts on this subject based on the ideXlab platform.

  • Performance evaluation and analyses of novel parabolic trough evacuated collector tubes with spectrum-selective Glass Envelope
    Renewable Energy, 2019
    Co-Authors: Qiliang Wang, Honglun Yang, Jingyu Cao, Gang Pei
    Abstract:

    Abstract Evacuated collector tubes (ECTs), the key components of the parabolic trough collector, suffer considerable heat loss at high operating temperature. Based on the characteristic of uneven distribution of solar irradiance around the absorber tube, novel ECTs covered with infrared (IR)-reflectors on the partial area of Glass Envelope were proposed to effectively reduce the heat loss and enhance the performance. Two kinds of ideal IR-reflectors, namely, the first one with a fixed cutoff wavelength, the second one with a variable and optimal cutoff wavelength were proposed. A real material of transparent conductive oxide (TCO) film was also used as an IR-reflector in novel ECTs for the analysis. The mathematical models relying on spectral parameter calculation method were established for comprehensively investigating the overall performance of the novel ECTs. Moreover, the influences of TCO film reflectivity and emissivity on the ECTs were investigated. Results demonstrated that the novel ECTs with TCO films, the first ideal films, and the second ideal films achieved obvious superior thermal performance compared with the conventional ECTs. Their relative heat loss reductions at an absorber temperature of 600 °C reached 18.7, 25.3, and 43.8%, the heat-collecting efficiencies were relatively enhanced by 7.2, 10.8, and 16.7%, respectively.

  • A spectral self-regulating parabolic trough solar receiver integrated with vanadium dioxide-based thermochromic coating
    Applied Energy, 1
    Co-Authors: Qiliang Wang, Honglun Yang, Gang Pei, Boxu Shen, Junchao Huang, Hongxing Yang
    Abstract:

    Abstract A significant decrease in the solar-thermal conversion efficiency of parabolic trough collectors occurs at high operating temperatures, mainly due to the massive radiant heat loss from the parabolic trough solar receiver incurred in this case. In this paper, a novel parabolic trough solar receiver integrated with vanadium dioxide-based thermochromic coating is proposed to effectively reduce the radiant heat loss and improve the overall performance of solar receivers. The thermochromic layer, deposited on the Glass Envelope’s inner surface in the negative thermal-flux region, has a reversible transition from a monoclinic (M) phase to a rutile (R) phase at the critical temperature of 68 °C. The occurrence of the phase transition in the thermochromic coating induces beneficial self-regulation of the spectrum-selectivity characteristics of the Glass Envelope, i.e., transmittance, reflectance, and absorptance (emittance) of Glass Envelope to solar and infrared radiation, for enhancing the thermal performance of solar receivers. Comprehensive heat transfer models based on the finite volume and spectral radiant heat transfer methods are established in this study. It is validated the models can predict the thermal performance of the solar receivers with high accuracy. In this framework, the total heat loss, thermal efficiency, and exergy efficiency of parabolic trough collector systems integrated with the proposed novel solar receivers are investigated and analyzed. Besides, the effects of transmittance of thermochromic coating (M phase) and emittance of thermochromic coating (R phase), two key parameters, on the overall performance of proposed solar receivers are also studied. The results show that no matter under the M phase or R phase, the thermochromic coating can play unique advantages to improve the thermal performance of the proposed solar receivers. The heat loss and thermal efficiency of the proposed solar receivers are effectively reduced and enhanced by 18.2% and 4.8% at the absorber temperature of 600 °C and inlet fluid temperature of 580 °C, respectively.

M.f. El-refaie - One of the best experts on this subject based on the ideXlab platform.

  • Solar heat gain through vertical cylindrical Glass
    Building and Environment, 1998
    Co-Authors: M.a. Kassem, S. Kaseb, M.f. El-refaie
    Abstract:

    Abstract Spaces with nonplanar glazed Envelopes are frequently encountered in contemporary buildings. Such spaces represent a problem when calculating the solar heat gain in the course of estimating the cooling or heating load; and hence, sizing of cooling or heating systems. The calculation, using the information currently available in the literature, is tedious and⧹or approximate. In the present work, the computational procedure for evaluating the solar heat gain to a space having a vertical cylindrical Glass Envelope is established, and, a computer program is coded to carry out the necessary computations and yield the results in a detailed usable form. The program is versatile and allows for the arbitrary variation of all pertinent parameters.

Junming Liang - One of the best experts on this subject based on the ideXlab platform.

  • experimental studies on nonuniform heat transfer and deformation performances for trough solar receiver
    Applied Thermal Engineering, 2016
    Co-Authors: Qinyuan Yuan, Jing Ding, Weilong Wang, Junming Liang
    Abstract:

    Abstract The nonuniform heat transfer and deformation performances of trough solar receiver are measured and analyzed. The temperature field of Glass Envelope for trough solar receiver is directly measured by Flir thermal infrared imager. On the positive region face to the collector, the Glass temperature is remarkably higher than ambient temperature for concentrated solar radiation, and it approaches to a minimum near the center region positively face to the collector. On the opposite region face to the collector, the Glass temperature remarkably decreases, and its minimum may be lower than ambient temperature because of infrared radiation to the sky. The experimental thermal efficiency is 57.8–65.6% with fluid temperature 473 K and effective solar flux of 183–842 W/m2, and the maximum Glass temperature difference in the same cross section can reach as high as 44.2 K. The temperature distribution and thermal efficiency of trough solar receiver are further calculated by 1-D uniform model and 2-D nonuniform model, and the calculated results fit with experimental data. According to experimental observation results, the absorber tube remarkably bends because of nonuniform heat transfer, and the Glass Envelope will probably break as the absorber tube contacts with the Glass Envelope for large thermal deformation. In order to avoid the Glass Envelope breakage, the deformation of receiver can be reduced by increasing the flow rate.

Honglun Yang - One of the best experts on this subject based on the ideXlab platform.

  • Performance evaluation and analyses of novel parabolic trough evacuated collector tubes with spectrum-selective Glass Envelope
    Renewable Energy, 2019
    Co-Authors: Qiliang Wang, Honglun Yang, Jingyu Cao, Gang Pei
    Abstract:

    Abstract Evacuated collector tubes (ECTs), the key components of the parabolic trough collector, suffer considerable heat loss at high operating temperature. Based on the characteristic of uneven distribution of solar irradiance around the absorber tube, novel ECTs covered with infrared (IR)-reflectors on the partial area of Glass Envelope were proposed to effectively reduce the heat loss and enhance the performance. Two kinds of ideal IR-reflectors, namely, the first one with a fixed cutoff wavelength, the second one with a variable and optimal cutoff wavelength were proposed. A real material of transparent conductive oxide (TCO) film was also used as an IR-reflector in novel ECTs for the analysis. The mathematical models relying on spectral parameter calculation method were established for comprehensively investigating the overall performance of the novel ECTs. Moreover, the influences of TCO film reflectivity and emissivity on the ECTs were investigated. Results demonstrated that the novel ECTs with TCO films, the first ideal films, and the second ideal films achieved obvious superior thermal performance compared with the conventional ECTs. Their relative heat loss reductions at an absorber temperature of 600 °C reached 18.7, 25.3, and 43.8%, the heat-collecting efficiencies were relatively enhanced by 7.2, 10.8, and 16.7%, respectively.

  • A spectral self-regulating parabolic trough solar receiver integrated with vanadium dioxide-based thermochromic coating
    Applied Energy, 1
    Co-Authors: Qiliang Wang, Honglun Yang, Gang Pei, Boxu Shen, Junchao Huang, Hongxing Yang
    Abstract:

    Abstract A significant decrease in the solar-thermal conversion efficiency of parabolic trough collectors occurs at high operating temperatures, mainly due to the massive radiant heat loss from the parabolic trough solar receiver incurred in this case. In this paper, a novel parabolic trough solar receiver integrated with vanadium dioxide-based thermochromic coating is proposed to effectively reduce the radiant heat loss and improve the overall performance of solar receivers. The thermochromic layer, deposited on the Glass Envelope’s inner surface in the negative thermal-flux region, has a reversible transition from a monoclinic (M) phase to a rutile (R) phase at the critical temperature of 68 °C. The occurrence of the phase transition in the thermochromic coating induces beneficial self-regulation of the spectrum-selectivity characteristics of the Glass Envelope, i.e., transmittance, reflectance, and absorptance (emittance) of Glass Envelope to solar and infrared radiation, for enhancing the thermal performance of solar receivers. Comprehensive heat transfer models based on the finite volume and spectral radiant heat transfer methods are established in this study. It is validated the models can predict the thermal performance of the solar receivers with high accuracy. In this framework, the total heat loss, thermal efficiency, and exergy efficiency of parabolic trough collector systems integrated with the proposed novel solar receivers are investigated and analyzed. Besides, the effects of transmittance of thermochromic coating (M phase) and emittance of thermochromic coating (R phase), two key parameters, on the overall performance of proposed solar receivers are also studied. The results show that no matter under the M phase or R phase, the thermochromic coating can play unique advantages to improve the thermal performance of the proposed solar receivers. The heat loss and thermal efficiency of the proposed solar receivers are effectively reduced and enhanced by 18.2% and 4.8% at the absorber temperature of 600 °C and inlet fluid temperature of 580 °C, respectively.