The Experts below are selected from a list of 5166 Experts worldwide ranked by ideXlab platform
Tsungching Chen - One of the best experts on this subject based on the ideXlab platform.
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experimental and theoretical studies of recyclic flat plate solar water heaters equipped with rectangle conduits
Renewable Energy, 2010Co-Authors: Tsungching Chen, Chengjung TsaiAbstract:Abstract A Recycle opeRation design using a flat-plate solar water heater with rectangle flow conduits was theoretically and experimentally investigated. Devices with differing flow-conduit geometries (i.e. aspect Ratio) and external Recycle were designed to create a solar heater with low heat-transfer resistance between the absorber and working fluid to increase the convective heat-transfer coefficient. Considerable solar water heater collector efficiency improvement has been obtained employing rectangle flow conduits and a Recycle opeRation, instead of Recycle solar collector constructed with circular pipes operated at the same total mass flow rate. Under a fixed absorber area and distance between the flow conduits, the collector efficiency increases with increasing flow conduit aspect Ratio, total mass flow rate and Recycle Ratio but with decreasing inlet water temperature. The incident solar radiation, mass flow rate, Recycle Ratio and flow conduit aspect Ratio influences on the collector efficiency and energy consumption are also discussed.
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the influences of Recycle on performance of baffled double pass flat plate solar air heaters with internal fins attached
Applied Energy, 2009Co-Authors: Ho-ming Yeh, Tsungching Chen, Tungwen Cheng, R C WangAbstract:A new device for inserting an absorber plate to divide a flat-plate channel into two parts with fins attached by baffles and external recycling at the ends is presented. The proposed device substantially improves the heat-transfer efficiency. Experimental and theoretical investigations into the device efficiency are presented. The theoretical prediction agreement with the measured values from the experimental results is good. The experimental and theoretical results are represented graphically and compared with data from the downward-type single-pass solar air heaters of the same size without recycling. Considerable heat-transfer improvement is obtained by employing baffled double-pass opeRations with external recycling and fin attached over and under the absorber plate. The Recycle Ratio and absorber plate location influences on the heat-transfer efficiency and on the power consumption increment are also discussed.
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the Recycle effect on the collector efficiency improvement of double pass sheet and tube solar water heaters with external Recycle
Renewable Energy, 2006Co-Authors: Chiidong Ho, Tsungching ChenAbstract:The paper presents a theoretical prediction of the performance of a double-pass sheet-and-tube solar water heater with external Recycle and comparison with that of a conventional type collector. Analytical results show that the Recycle effect can effectively enhance the collector efficiency compared with that in a single-pass device with the same flow rate. The desirable effect of increasing convective transfer rate and the undesirable effect of reducing heat-transfer driving force are the two conflict effects produced by the Recycle opeRation. It was found that the increment of convective transfer rate by increasing the Recycle Ratio could generally compensate for the decrement of the temperature difference, leading to improved performance, especially for low flow rate. Also, the collector efficiency increases with increasing collector aspect Ratio (i.e. either increasing the tube length or decreasing the number of tube pairs) for a specified collector area and the distance between tubes.
Gerry Riley - One of the best experts on this subject based on the ideXlab platform.
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comparison of effects on heat transfer and burnout under wet and dry Recycle oxyfuel combustion conditions
Journal of The Energy Institute, 2011Co-Authors: J P Smart, R Patel, Gerry RileyAbstract:In this study, the effect of using both wet and dry Recycled flue gases on oxyfuel combustion has been investigated using an International Flame Research Foundation (IFRF) burner installed on a 0·5 MWt combustion test facility firing Russian coal and Russian coal/biomass blend under wet and dry Recycle conditions. Radiative and convective heat transfer characteristics and burnout measurements were the primary focus of the work. Recycle Ratios were varied between 65 and 75%. The peak radiative heat flux decreases with increasing Recycle Ratio under both wet and dry Recycle conditions for both the parent coal and the coal/biomass blend. The opposite trend is observed with the convective heat flux. The peak radiative heat fluxes are higher and the convective heat fluxes are lower for the dry Recycle compared to the wet Recycle. Low residual carbon in ash levels is measured with oxyfuel under both wet and dry Recycle Ratios.
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oxy fuel combustion of coal and biomass the effect on radiative and convective heat transfer and burnout
Combustion and Flame, 2010Co-Authors: J P Sma, R Patel, Gerry RileyAbstract:Abstract This paper focuses on results of co-firing coal and biomass under oxy-fuel combustion conditions on the RWEn 0.5 MWt Combustion Test Facility (CTF). Results are presented of radiative and convective heat transfer and burnout measurements. Two coals were fired: a South African coal and a Russian Coal under air and oxy-fuel firing conditions. The two coals were also co-fired with Shea Meal at a co-firing mass fraction of 20%. Shea Meal was also co-fired at a mass fraction of 40% and sawdust at 20% with the Russian Coal. An IFRF Aerodynamically Air Staged Burner (AASB) was used. The thermal input was maintained at 0.5 MWt for all conditions studied. The test matrix comprised of varying the Recycle Ratio (RR) between 65% and 75% and furnace exit O2 was maintained at 3%. Carbon-in-ash samples for burnout determination were also taken. Results show that the highest peak radiative heat flux and highest flame luminosity corresponded to the lowest Recycle Ratio. The effect of co-firing of biomass resulted in lower radiative heat fluxes for corresponding Recycle Ratios. Furthermore, the highest levels of radiative heat flux corresponded to the lowest convective heat flux. Results are compared to air firing and the air equivalent radiative and convective heat fluxes are fuel type dependent. Reasons for these differences are discussed in the main text. Burnout improves with biomass co-firing under both air and oxy-fuel firing conditions and burnout is also seen to improve under oxy-fuel firing conditions compared to air.
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radiation and convective heat transfer and burnout in oxy coal combustion
Fuel, 2010Co-Authors: J P Smart, P Onions, Gerry RileyAbstract:Measurements of radiative and convective heat transfer, and carbon-in-ash have been taken on the RWEn 0.5 MWth combustion test facility (CTF) firing two different coals under oxy-fuel firing conditions. A 0.5 MWth scaled version of an IFRF Aerodynamically Air Staged Burner (AASB) was used under oxy-fuel firing conditions using simulated dry Recycled flue gas. The two coals fired were a Russian Coal and a South African Coal. Recycle Ratios were varied within the range of 65–75% dependent on coal. Furnace exit O2 values were maintained at 3% and 6% for the majority of tests. Air firing tests were also performed to generate baseline data. The work described in the main text gives a comprehensive insight into the effect of oxy-fuel combustion on both radiative and convective heat transfer, and carbon-in-ash compared to air under dry simulated Recycle conditions. Results have shown peak radiative heat flux values are inversely related to the Recycle Ratio for the two coals studied. Conversely, the convective heat flux values increase with increasing Recycle Ratio. It was also observed that the axial position of the peak in radiative heat flux moves downstream away from the burner as Recycle Ratio is increased. It has been shown that a “working range” of Recycle Ratios exist where both the radiative and convective heat fluxes are comparable with air. Carbon-in-ash (CIA) was measured for selected conditions. For air firing of Russian Coal, the CIA for follows and expected trend with CIA decreasing with increasing furnace exit O2. The CIA data for the two Recycle Ratios of 72% and 68% for the same coal show that the CIA values are lower than for air firing for corresponding furnace exit O2 levels and vary little with the value of furnace exit O2. CIA measurements were taken for the South African Coal for a range of Recycle Ratios at 3% and 6% furnace exit O2 levels. Results indicate that the CIA values are lower for higher furnace exit O2 as would be expected. There appears to be a marginal general decrease in CIA as Recycle Ratio increases but it is suggested that at these generally low levels of CIA (i.e. < 0.7%) it is difficult to be conclusive.
Satyender Singh - One of the best experts on this subject based on the ideXlab platform.
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thermal and thermohydraulic efficiency of recyclic type double pass solar air heaters with fins and baffles
Heat Transfer Engineering, 2016Co-Authors: Satyender Singh, Prashant DhimanAbstract:This paper presents investigations related to the heat-transfer performance improvement of double-pass finned and finned with baffles solar air heaters. The analytical study has been carried out to see the effects of parameters such as mass flow rate, Recycle Ratio, fins thickness, number of fins, and baffles width on the heaters’ efficiencies. It is indicated that the mass flow rate and the Recycle Ratio are the most significant factors, which considerably increase the heaters’ efficiencies by increasing the fluid velocity. The theoretical results showed that the device with fins plus baffles can enhance the heat transfer rate compared with the device with fins under the same flow rate and working dimensions. The effect of the depth of the first channel on the thermal and thermohydraulic efficiency improvement is also delineated. To validate the proposed theoretical models, comparisons of the results are performed with those obtained from previous studies and show that good agreement is achieved.
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recyclic double pass packed bed solar air heaters
International Journal of Thermal Sciences, 2015Co-Authors: Prashant Dhiman, Satyender SinghAbstract:Abstract In the present work, analytical models to predict the thermal and thermohydraulic efficiencies of two different designs of double pass packed bed solar air heater under external Recycle have been proposed. It is predicted that Model A with the single air pass through the first channel as well as the Recycle of the air exiting from the second channel through the third channel can enhance the heat transfer rate more as compared to Model B. The wire mesh screen as an absorbing media above the absorber plate is used in both of the solar air heater models. The Recycle Ratio and the mass flow rate are varied from 0.1 to 1 and 0.01–0.025 kg/s, respectively. The results of the study depict that the Recycle Ratio and the mass flow rate substantially increases the heaters efficiencies by increasing the fluid velocity. The maximum value of the thermal efficiency of Model A is found to be about 6.6% higher than that of Model B. The optimum values of the Recycle Ratio and the mass flow rate, at which the heaters yield maximum values of thermo-hydraulic efficiencies, are identified and presented. In addition, the effect of the channel depth Ratio on the thermal performance improvement is also delineated.
Prashant Dhiman - One of the best experts on this subject based on the ideXlab platform.
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thermal and thermohydraulic efficiency of recyclic type double pass solar air heaters with fins and baffles
Heat Transfer Engineering, 2016Co-Authors: Satyender Singh, Prashant DhimanAbstract:This paper presents investigations related to the heat-transfer performance improvement of double-pass finned and finned with baffles solar air heaters. The analytical study has been carried out to see the effects of parameters such as mass flow rate, Recycle Ratio, fins thickness, number of fins, and baffles width on the heaters’ efficiencies. It is indicated that the mass flow rate and the Recycle Ratio are the most significant factors, which considerably increase the heaters’ efficiencies by increasing the fluid velocity. The theoretical results showed that the device with fins plus baffles can enhance the heat transfer rate compared with the device with fins under the same flow rate and working dimensions. The effect of the depth of the first channel on the thermal and thermohydraulic efficiency improvement is also delineated. To validate the proposed theoretical models, comparisons of the results are performed with those obtained from previous studies and show that good agreement is achieved.
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recyclic double pass packed bed solar air heaters
International Journal of Thermal Sciences, 2015Co-Authors: Prashant Dhiman, Satyender SinghAbstract:Abstract In the present work, analytical models to predict the thermal and thermohydraulic efficiencies of two different designs of double pass packed bed solar air heater under external Recycle have been proposed. It is predicted that Model A with the single air pass through the first channel as well as the Recycle of the air exiting from the second channel through the third channel can enhance the heat transfer rate more as compared to Model B. The wire mesh screen as an absorbing media above the absorber plate is used in both of the solar air heater models. The Recycle Ratio and the mass flow rate are varied from 0.1 to 1 and 0.01–0.025 kg/s, respectively. The results of the study depict that the Recycle Ratio and the mass flow rate substantially increases the heaters efficiencies by increasing the fluid velocity. The maximum value of the thermal efficiency of Model A is found to be about 6.6% higher than that of Model B. The optimum values of the Recycle Ratio and the mass flow rate, at which the heaters yield maximum values of thermo-hydraulic efficiencies, are identified and presented. In addition, the effect of the channel depth Ratio on the thermal performance improvement is also delineated.
Chunchieh Chao - One of the best experts on this subject based on the ideXlab platform.
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performance improvement of wire mesh packed double pass solar air heaters with external Recycle
Renewable Energy, 2013Co-Authors: Chunsheng Lin, Yuchuan Chuang, Chunchieh ChaoAbstract:The device performance of the new design of wire mesh packed double-pass solar air heaters with attaching wire mesh under external Recycle was investigated experimentally and theoretically. The improvement of device performance of wire mesh packed solar air heaters with different flow patterns is represented graphically and compared, including the single-pass, flat-plate double-pass with Recycle and wire mesh packed double-pass with Recycle. Heat transfer improvement is considerably obtained by employing such a recyclic double-pass with wire mesh packed, instead of using the flat-plate single-pass opeRation. The wire mesh packed double-pass device introduced in this study was proposed for aiming to strengthen the convective heat transfer coefficient for air flowing through the wire mesh packed bed, and to determine the optimal design on an economic consideRation in terms of both heat transfer efficiency improvement and power consumption increment. The effect of Recycle Ratio on the heat transfer efficiency enhancement as well as the power consumption increment has been also delineated.
