A preliminary experimental investigation on characteristics of natural convection based on solar thermal collection using supercritical carbon dioxide

Zhang, X. R.

doi:10.1002/er.2936

Cited by 9 publications

(10 citation statements)

References 25 publications

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“…Such kind of evacuated solar collector panel is generally used for pressurized/low‐to‐medium temperature energy conversion systems , and in the current study, it serves as one general base for the energy efficiency comparison. The following parameters are defined to describe the collector characteristics of such collector panel :

{italicI}_{italict} = \int_{0}^{{italict}_{italicd}} I dt

\overset{true¯}{m_{italicC O_{2}}} = \frac{\int_{0}^{{italict}_{italicd}} {italicm}_{C {italicO}_{2}} d t}{t_{d}}

{italicq}_{italiccollector} = {italicm}_{C {italicO}_{2}} ({italich}_{1} - {italich}_{4})

{italicq}_{italicct} = \int_{0}^{{italict}_{italicd}} {italicq}_{italiccollector} dt

{italicη}_{italiccollector} = \frac{q_{collector}}{italicI}

\overset{true¯}{η_{collector}} = \frac{q_{ct}}{I_{t}}

where I is the solar radiation, I t is the total solar radiation during the test time period per day (an integral of the solar radiation on a test time period),

\overset{...}{true}

…”

Section: Model Setups For Representative Power Cyclesmentioning

confidence: 99%

“…Regenerator and reheater pieces of equipment may be added for efficiency considerations. Based on previous experimental results [24][25][26][27][28][29][30][31][32], evacuated tube-kind solar collector using supercritical CO 2 (for high pressure and temperature operation) is assumed as the energy source for the current thermodynamic cycles. The collector consists of a glass envelope over a glass tube coated with a selective solar absorber coating.…”

Section: Model Construction For Basic Low-to-medium Temperature Thermmentioning

confidence: 99%

“…CO 2 fluid is also generally used as the base working fluid for thermodynamic cycle discussion and optimizations because of its more and more matured development in low-to-medium temperature region. In recent years, many groups have investigated the use of CO 2 as a natural working fluid for low-to-medium heat harvest systems [20][21][22][23][24][25]. A solar energy-powered Rankine thermodynamic cycle using supercritical carbon dioxide as a working fluid was put forward and analyzed in Zhang et al [21].…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamic analysis of representative power generation cycles for low-to-medium temperature applications

Chen

Zhao

et al. 2014

Int. J. Energy Res.

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SUMMARY This study is focused on the analysis of representative thermodynamic cycles for power generation at low‐to‐medium temperatures (with the highest cycle temperature from 450 to 700 K). The natural working fluid of carbon dioxide is selected for the current tests and comparisons with suitable operation ranges. Energy balance and exergy loss models are established and applied to 10 selected representative thermodynamic cycles. One modified efficiency parameter is also defined for better comparison of performances, which has considered the effects of both specific thermodynamic process and cycle complexity. Based on the modified efficiency parameter, it is found that Rankine cycle yields the highest performance at 450–500 K among the 10 representative cycles, while regenerative Brayton cycle shows better behavior for 550–700 K. Detailed behaviors and optimal principals of regenerative Brayton cycles are also identified and compared in this study. Also, a new cycle is also proposed in this study, which combines the advantages of Rankine cycle and Brayton cycle. The new cycle is proved to have better work output potential but higher system complexity factor. In addition, based on the thermodynamic analysis, possible future directions of low‐to‐medium temperature power cycles are summarized. It is hoped that the results can be of help for related power generation system designs. Copyright © 2014 John Wiley & Sons, Ltd.

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{italicI}_{italict} = \int_{0}^{{italict}_{italicd}} I dt

\overset{true¯}{m_{italicC O_{2}}} = \frac{\int_{0}^{{italict}_{italicd}} {italicm}_{C {italicO}_{2}} d t}{t_{d}}

{italicq}_{italiccollector} = {italicm}_{C {italicO}_{2}} ({italich}_{1} - {italich}_{4})

{italicq}_{italicct} = \int_{0}^{{italict}_{italicd}} {italicq}_{italiccollector} dt

{italicη}_{italiccollector} = \frac{q_{collector}}{italicI}

\overset{true¯}{η_{collector}} = \frac{q_{ct}}{I_{t}}

where I is the solar radiation, I t is the total solar radiation during the test time period per day (an integral of the solar radiation on a test time period),

\overset{...}{true}

…”

Section: Model Setups For Representative Power Cyclesmentioning

confidence: 99%

Section: Model Construction For Basic Low-to-medium Temperature Thermmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Thermodynamic analysis of representative power generation cycles for low-to-medium temperature applications

Chen

Zhao

et al. 2014

Int. J. Energy Res.

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“…Nowadays, usage of supercritical fluids in various applications including refrigeration engineering, nuclear engineering, and aerospace engineering is very popular . More attention is primarily focused on carbon dioxide, water, refrigerants, and hydrocarbon fuels, particularly for water and carbon dioxide in the view of the heat transfer. In addition, there are also studies on thermodynamic analysis .…”

Section: Introductionmentioning

confidence: 99%

“…Similarly, this situation can be diminished and even removed by the higher operating pressures.KEYWORDS buoyancy, operating pressure, secondary flow, supercritical n-decane, thermal boundary layer, turbulence intensity 1 | INTRODUCTION Nowadays, usage of supercritical fluids in various applications including refrigeration engineering, nuclear engineering, and aerospace engineering is very popular. 1,2 More attention is primarily focused on carbon dioxide, water, refrigerants, and hydrocarbon fuels, 3-6 particularly for water 7-9 and carbon dioxide [10][11][12][13][14][15] in the view of the heat transfer. In addition, there are also studies on thermodynamic analysis.…”

mentioning

confidence: 99%

Turbulent heat transfer characteristics of supercritical n ‐decane in a vertical tube under various operating pressures

Sun

Sundén

et al. 2019

Int J Energy Res

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Summary To explore the effect of the operating pressure on the flow and thermal characteristics in a vertical tube with supercritical n‐decane, the inner wall temperature along the streamwise direction, the applicability of empirical correlations and buoyancy criteria are studied firstly. The mechanisms in views of density distribution, velocity field, turbulence intensity, the thickness of the thermal boundary layer, and secondary flow are then analyzed. It is observed that the buoyancy is helpful for the phenomenon of heat transfer deterioration at lower operating pressures but higher operating pressures can diminish this tendency. According to this reason, the empirical correlation proposed by Bae and Kim is suitable for the higher operating pressures but cannot well predict the occurrence of heat transfer deterioration. However, it can be evaluated by the buoyancy criterion Gr/Re2 = 0.01 qualitatively. The decrease of turbulence intensity, the thickened thermal boundary layer, and secondary flow generation make contributions to the heat transfer deterioration in particular. Similarly, this situation can be diminished and even removed by the higher operating pressures.

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A review on classification and comparison of different models in solar radiation estimation

Tolabi

Moradi

Ayob

2014

Int. J. Energy Res.

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SUMMARYThis paper introduces a new classification scheme for the solar radiation estimation techniques based on three categories: empirical models (based on statistical regression techniques), simulated models (based on training), and optimized models (based on optimization algorithms). For the optimized model category, a novelty bees algorithm estimation based on a linear empirical model is developed. Eight different methods from three classes have been tested on three sample geographic positions of Iran in order to compare the efficiency, complexity, sensed parameters, and required prior training of each category with others by implementing in the Matlab software. Among all tested models, the best properties are obtained for optimized empirical models by optimization algorithms. The main advantages of this model type are that it eliminates the training stage and therefore reduces the complexity rather than simulated models yet offers high accuracy estimation.

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A preliminary experimental investigation on characteristics of natural convection based on solar thermal collection using supercritical carbon dioxide

Cited by 9 publications

References 25 publications

Thermodynamic analysis of representative power generation cycles for low-to-medium temperature applications

Thermodynamic analysis of representative power generation cycles for low-to-medium temperature applications

Turbulent heat transfer characteristics of supercritical n ‐decane in a vertical tube under various operating pressures

A review on classification and comparison of different models in solar radiation estimation

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