scholarly journals Experimental Investigation and Theoretical Analysis on the Performance of Tube-Sheet Photovoltaic Thermal (PV/T) Collectors

2021 ◽  
Vol 8 ◽  
pp. 45-58
Author(s):  
Guoqing Yu ◽  
Hongzhi Liu ◽  
Wei Zhao ◽  
Gaojie Yang
Keyword(s):  
Theoretical Analysis ◽  
Thermal Resistance ◽  
Water Temperature ◽  
Temperature Difference ◽  
Electricity Generation ◽  
Large Temperature ◽  
Transfer Model ◽  
Tube Sheet ◽  
Daily Average ◽  
Pv Panel

The PV/T collectors realize the simultaneous output of electricity and thermal energy, which are more efficient than the separated photovoltaic (PV) or solar thermal collectors. In this paper, the electricity generation and thermal collection performances of tube-sheet PV/T collector are studied. The main research contents are as follows: an experimental test system of PV/T collector was built to test the electricity generation and thermal collection performances of tube-sheet PV/T at an inlet water temperature of 30°C. Moreover, the flow resistance test was carried out. In addition, the theoretical heat transfer model was established, and the thermal performance was calculated by theoretical analysis. The experimental data showed that the daily average temperature difference between the PV panel and the inlet water temperature was about 22.5°C. The daily average electrical efficiency was about 9.25%, and the daily average thermal efficiency was about 28.67%. The theoretical analysis of the tube-sheet PV/T model was carried out, and the calculated results were close to the experimental results. The main reason for the large temperature difference between the PV panel and water temperature was that the combined thermal resistance between the PV panel and the absorber plate was large, and reducing the combined thermal resistance could reduce the temperature of the PV panel. The effects of solar irradiance, ambient temperature and spacing of row tubes on the performance of thermal collection were analyzed to optimize the PV/T performance.

Sea Water Distillatory Using Rising Film on the Fluted Surface of Horizontal Tubes

2006 ◽  
Author(s):  
Yan Li ◽  
Ning Mei ◽  
Yesheng Sun
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Theoretical Analysis ◽  
Numerical Solution ◽  
Temperature Difference ◽  
Sea Water ◽  
Flow Characteristics ◽  
Horizontal Tube ◽  
Transfer Model ◽  
Horizontal Tubes

The purpose of this study is to investigate the mechanism of the seawater distillatory using rising liquid thin film on the fluted surface of a horizontal tube. By analyzing the formation of the rising film, a process of the HRF evaporators was designed to analysis the efficiency of the system. The numerical solution of heat transfer model shows that the temperature difference of HRF in one effect is lower than that of HFF. The behaviors of the flow characteristics were discussed. The results show that the rising liquid thin film could be formed when the rate of roll equaled 15°. The results from theoretical analysis suggest that seawater distillatory using rising liquid thin film on the fluted surface of a horizontal tube was especially suitable for the wobble environment.

scholarly journals Optimal Design Strategy of a Solar Reflector Combining Photovoltaic Panels to Improve Electricity Output: A Case Study in Calgary, Canada

2021 ◽  
Vol 13 (11) ◽  
pp. 6115
Author(s):  
Moon Keun Kim ◽  
Khalid Osman Abdulkadir ◽  
Jiying Liu ◽  
Joon-Ho Choi ◽  
Huiqing Wen
Keyword(s):  
Solar Radiation ◽  
Electricity Generation ◽  
Low Cost ◽  
Design Strategy ◽  
Numerical Approach ◽  
Optimal Shape ◽  
Energy Technology ◽  
Experimental Database ◽  
Pv Panel

This study explores the combination of photovoltaic (PV) panels with a reflector mounted on a building to improve electricity generation. Globally, PV panels have been widely used as a renewable energy technology. In order to obtain more solar irradiance and improve electricity output, this study presents an advanced strategy of a reflector combining PV panels mounted on a building in Calgary, Canada. Based on an experimental database of solar irradiances, the simulation presents an optimal shape designed and tilt angles of the reflector and consequently improves solar radiation gain and electricity outputs. Polished aluminum is selected as the reflector material, and the shape and angle are designed to minimize the interruption of direct solar radiation. The numerical approach demonstrates the improvement in performance using a PV panel tilted at 30°, 45°, 60°, and 75° and a reflector, tilted at 15.5° or allowed to be tilted flexibly. A reflector tilted at 15.5° can improve solar radiation gains, of the panel, by nearly 5.5–9.2% at lower tilt angles and 14.1–21.1% at higher tilt angles. Furthermore, the flexibly adjusted reflector can improve solar radiation gains on the PV panel, by nearly 12–15.6% at lower tilt angles and 20–26.5% at higher tilt angles. A reflector tilted at 15.5° improves the panel’s output electricity on average by 4–8% with the PV panel tilted at 30° and 45° respectively and 12–19 % with the PV panel tilted at 60° and 75°, annually. Moreover, a reflector that can be flexibly tilted improves electricity output on average by 9–12% with the PV panel tilted at 30° and 45° and 17–23% with the PV panel tilted at 60° and 75°. Therefore, the utilization of a reflector improves the performance of the PV panel while incurring a relatively low cost.

Theoretical investigation on the heating performance of a recuperative heat pump water heater using CO2/HCs with large temperature glides in cold regions

2021 ◽  
pp. 1-22
Author(s):  
Jielin Luo ◽  
Qin Wang ◽  
Zhen Zhao ◽  
Kaiyin Yang ◽  
Guangming Chen ◽  
...  
Keyword(s):  
Heat Pump ◽  
Temperature Difference ◽  
Hot Water ◽  
Large Temperature ◽  
Water Heater ◽  
Ambient Temperatures ◽  
Heating Performance ◽  
Heat Pump Water Heater ◽  
Vapor Injection ◽  
Injection Cycle

Abstract Considering the issues of environmental pollution and energy efficiency, heat pumps are gradually replacing traditional coal combustion for heating at low ambient temperatures. In this paper, eco-friendly CO2/HCs with large temperature glides are applied in a single-stage recuperative heat pump water heater. Its heating performance is theoretically investigated under the working condition of producing circulating hot water in typical winter of northern China, with medium temperature difference between supply/return water and large temperature difference between air inlet and water inlet. Due to its simple structure, low initial investment and high efficiency, its potential for producing circulating hot water is demonstrated. Exergy analyses are conducted to reveal the significant influence of the exergy losses of heat exchanger on system performance. For specified CO2/HC, optimal COP is obtained through global optimization of cycle pressures and mixture concentration. The heating performances of different CO2/HCs are compared, among which CO2/R600 and CO2/R600a behave better. Meanwhile, a typical vapor-injection cycle is used to demonstrate priorities on the heating performance of this recuperative cycle, in which the COP of recuperative cycle using CO2/R600 is more than 3.4% higher than that of the vapor-injection cycle. The results obtained in this paper provide a simple and efficient solution for producing circulating hot water at low ambient temperatures.

Double-diffusive instabilities in a vertical slot

1999 ◽  
Vol 392 ◽  
pp. 213-232 ◽  
Author(s):  
OLIVER S. KERR ◽  
KIT YEE TANG
Keyword(s):  
Temperature Difference ◽  
Salinity Gradient ◽  
Stability Boundary ◽  
Large Temperature ◽  
Vertical Slot ◽  
Stability And Instability ◽  
Heat Diffusivity ◽  
Prandtl Numbers ◽  
The Stability ◽  
Double Diffusive

A fluid stably stratified by a salinity gradient and enclosed between two vertical boundaries can become unstable when it is subjected to a temperature difference between the walls. The linear stability of such a fluid in a vertical slot is investigated. Errors in earlier results are found, confirming recent results of Young & Rosner (1998). Four different asymptotic regimes on the stability boundary are identified. One of these, the limit of a strong salinity gradient, has previously been analysed. The analyses of the separate asymptotic limits of weak salinity gradient, large temperature difference and small wavenumber are also given. These four cases make up much of the total boundary between stability and instability for double-diffusive instabilities in a vertical slot, and so most of this boundary can be mapped out for general Prandtl numbers and salt/heat diffusivity ratios using these results.

Experimental Investigation of Heat Transfer in Impingement Air Cooled Plate Fin Heat Sinks

2005 ◽  
Vol 128 (4) ◽  
pp. 412-418 ◽  
Author(s):  
Zhipeng Duan ◽  
Y. S. Muzychka
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Transfer Model ◽  
Heat Sinks ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Developing Flow ◽  
Rectangular Channels

Impingement cooling of plate fin heat sinks is examined. Experimental measurements of thermal performance were performed with four heat sinks of various impingement inlet widths, fin spacings, fin heights, and airflow velocities. The percent uncertainty in the measured thermal resistance was a maximum of 2.6% in the validation tests. Using a simple thermal resistance model based on developing laminar flow in rectangular channels, the actual mean heat transfer coefficients are obtained in order to develop a simple heat transfer model for the impingement plate fin heat sink system. The experimental results are combined into a dimensionless correlation for channel average Nusselt number Nu∼f(L*,Pr). We use a dimensionless thermal developing flow length, L*=(L∕2)∕(DhRePr), as the independent parameter. Results show that Nu∼1∕L*, similar to developing flow in parallel channels. The heat transfer model covers the practical operating range of most heat sinks, 0.01<L*<0.18. The accuracy of the heat transfer model was found to be within 11% of the experimental data taken on four heat sinks and other experimental data from the published literature at channel Reynolds numbers less than 1200. The proposed heat transfer model may be used to predict the thermal performance of impingement air cooled plate fin heat sinks for design purposes.

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