Showing 7 results for Thermal Efficiency
Volume 14, Issue 4 (7-2012)
Abstract
In this paper, the performance evaluation of a two-way hybrid photovoltaic/thermal (PV/T) solar collector was analytically and experimentally carried out. Mathematical expressions for operating parameters in glass to glass and glass to tedlar PV/T solar collectors were developed and experimentally validated by a glass to tedlar PV/T solar collector system. Also the influence of air flow rate on the solar collector performance was investigated. The results showed that the glass to glass PV/T solar collector gave higher outlet air temperature, cell temperature and thermal efficiency than the glass to tedlar PV/T solar collector. However, back surface temperature and electrical efficiency were higher in case of glass to tedlar collector. Increasing the air flow rate led to a lower outlet air temperature and a higher electrical efficiency of the photovoltaic module. Maximum experimental electrical efficiency, thermal efficiency and overall thermal efficiency for the glass to tedlar PV module were found to be 10.35, 57.9 and 84.5%, respectively.
Alireza Batooei, Ali Keshavarz Valian,
Volume 16, Issue 2 (4-2016)
Abstract
A Stirling engine cycle combined with a SI engine cycle to recover the SI engine exhaust gas waste heat. One dimensional combustion simulation code is prepared for Spark Ignition type engine (M355G) simulation. The accuracy of numerical simulated results has been validated with M355G experimentally. The experimental generated power and exhaust gas temperature vary in the range of 84.1- 176.7 kW and 610-710 , respectively. The 1D code estimates the generated power with maximum 5.9% error and average exhaust gas temperature with 3.8% error in the operating range of the engine. The thermal analysis is done, and the results show that about 25% the part of input energy transfers by the exhaust gas as a waste. The results indicate that by installing a Stirling engine heater on the exhaust pipe of the SI engine can recover about 8.4kW of the waste heat at the best condition. The simulation of Alpha-type Stirling engine is done by GT-Suit program and the Solo V161 experimental results is used for the validation. According to 9% error in generated power calculation for validation, the new Stirling engine is suggested for installing in exhaust pipe. The generated power and thermal efficiency is estimated for Stirling engine in various exhaust gas temperature which occurred in various SI engine working condition. The coupled engines heat balance showed that the thermal efficiency is about 2-3% more than the ordinary one.
Seyed Mostafa Hosseinalipour, Parisa Afkari, Hamidreza Shahbazian,
Volume 17, Issue 5 (7-2017)
Abstract
Gas turbine power and thermal efficiency increase with inlet temperature. Considering the temperature limitations for the alloys used in gas turbine components, employment of techniques for reduction of these components temperatures seems to be an essential subject. Based on the research conducted on this subject, among all the proposed methods, rib cooling yields higher heat transfer coefficient and among various types of ribs, V-shaped ribs have higher heat transfer compared to angled rib. The purpose of this feasibility study is to investigate the two proposed ribs for use in gas turbine from heat transfer and fluid flow view and compare their thermal performance. In this work, 3-D numerical simulation has been performed for V-shaped ribs with an angle of 〖60〗^° for the two cases of staggered and inline ribs in two opposite walls in a rectangular channel. Experimental results have been used for validation. The results indicate an enhancement of ~22% in heat transfer if V-shaped ribs with an angle 〖60〗^° and downstream orientation are located in staggering form in two opposite walls of a channel. In this case, an increase of 10% is observed for pressure drop, however, its thermal performance increases 12% which is positive and considerable.
S.r. Kazemi Mazandarani, M. Farzaneh-Gord , M.m. Shahmardan ,
Volume 19, Issue 5 (5-2019)
Abstract
Prior to entering to the throttling valve of the City Gate Stations (CGS), high-pressure natural gas flow in pipelines is transmitted through Water Bath Indirect Heaters (WBIH), which is increasing its temperature to compensate for the temperature drop caused by the Joule-Thomson effect and preventing the occurrence of the hydration phenomenon, gas freezing, and subsequent blockage of the gas flow path. Because of feeding of processed gas of the network on a large scale, optimizing the WBIHs has a lot of significance. In the present study, each WBIH is simulated by a type of thermodynamic machine, consisting of two distinct thermal systems. According to the problem geometry and governing equations, the thermodynamic analysis of these two systems results in the formulation of a relationship between their thermal efficiencies together and the definition of a parameter was defined as the Thermodynamic Similarity Coefficient (TSC). Then, the results showed that always, a constant logarithmic relationship exists between of the Number of Heat Transfer Units (NTU) values difference of the fire tube and heat coil of the WBIHs with their TSC as well as a constant power relationship between their NTU values ratio with this coefficient too. Finally, by solving the equation system obtained from these two relations, it was possible to determine the optimal values of NTU for the fire tube and heat coil as functions of TSC of the WBIH and to achieve the relationship between their optimum geometric dimensions together in the most ideal heat transfer state with a maximum relative error of about 13%.
H. Farzan, S.m. Jaafarian, M. Ameri,
Volume 20, Issue 5 (5-2020)
Abstract
The asphalt pavements are exposed to daily solar radiation; hence the asphalt pavements provide the remarkable potential to heat a working fluid such as water. Simple structure and ease of fabrication of asphalt solar collectors (ASCs) promise applicability and low-cost operation of this class of thermal collectors. The current experimental and theoretical investigation evaluates the performance, efficiency and dynamic of ASCs in real operating condition at Bam County, Kerman. In this research, to investigate the performance of ASCs, a 1.2m2 prototype was fabricated and its dynamics was monitored under 6 hours a day in two different flow rates of water. The results illustrate that increasing the flow rate of water to collector by 2 times improves the collector efficiency by 25%, while the difference in the inlet and outlet water temperatures decreases. Furthermore, by utilizing the experimental data, a theoretical approach was utilized to predict the performance of ASC in the other flow rates of water. The developed analytic approach has good consistency with the obtained experimental test. The analytic approach provides an effective method to estimate the performance of ASCs with appropriate accuracy, when the experimental results are unavailable.
S. Ghaffarzadeh, A. Nassiri Toosi , M.t. Zarrinkolah,
Volume 20, Issue 8 (8-2020)
Abstract
RCCI as low temperature combustion is one of the common methods for reducing nitrogen oxides and soot pollutants. In this study, the effect of exhaust gas recirculation on combustion and emission of an RCCI engine, fueled with diesel and CNG was investigated. The investigated engine is a single-cylinder engine with diesel direct injection to the combustion chamber as high-reactivity fuel and a port fuel injection of CNG fuel as low-reactivity fuel. The start of injection, the injection shape, and the injection duration of both injectors are controlled by the developed ECU. Since the engine tested has good stability in the premix ratio of 60% and is capable of operating with high EGR percentage, it was selected for investigation. The results of this study show that with an increase of the exhaust gas recirculation rate from 0 to 34%, the amount of IMEP and thermal efficiency decrease by about 18%. As the EGR increases, the start, middle, and end of the combustion are delayed due to the decrease in oxygen content inside the combustion chamber. With the increase of EGR, the temperature of the combustion chamber decreased so that increasing CO and UHC production, showing an increase of 86 and 300%, respectively, while NOx decreases by 350%.
Mohammad Saleh Barghi Jahromi, Vali Kalantar, Mohammad Hossein Dehestani Bafghi,
Volume 23, Issue 12 (12-2023)
Abstract
Among solar collectors, solar parabolic dishes have attracted the attention of researchers due to their high working temperature and high thermal performance. The purpose of this study is to compare two absorber receivers (normal-black color) for the solar parabolic dish. The analysis of energy and exergy was investigated for different conditions at different hours. Two-axis tracking system was applied to the outlet temperature in the solar parabolic dish system. The results show that the maximum temperature of the normal and black absorber is 101.52 and 115.53 ℃ , respectively, and the maximum energy and exergy efficiency of the black spiral absorber plate is 0.7 and 0.21. In addition, the designed parabolic solar container raised the temperature of 80 liters of water to 60 ℃ in 5 hours after sunlight, which is suitable for bathing and washing clothes in winter in backward and rural areas without electricity and fuel. Therefore, it is enough for four to five people.
