The Experts below are selected from a list of 34776 Experts worldwide ranked by ideXlab platform
Anil Kumar - One of the best experts on this subject based on the ideXlab platform.
-
Heat transfer augmentation in solar thermal collectors using impinging air jets: A comprehensive review
Renewable & Sustainable Energy Reviews, 2018Co-Authors: Ranchan Chauhan, Tej Singh, Nitin Kumar, N.s. Thakur, Raj Kumar, Anil KumarAbstract:Jet impingement has led to considerable augmentation in heat transfer characteristics of solar thermal collectors. The impinging air jets are characterized by different control factors where it becomes essential to study their dependence on performance defining criteria so as to arrive at the optimized impinging jet geometry which create one or combination of following conditions favorable for heat transfer with minimal friction losses inside the collector: (a) breaking Laminar sub layer (b) increasing turbulent intensity (c) increasing heat transfer area, and (d) generating vortex or secondary flows. The present article examines the thermodynamic behavior of solar thermal collector, review the experimental investigations reported in the literature to study the dependence of control factors on heat transfer and friction characteristics and review the multi criteria decision making methods towards optimization of control factor combinations for an optimal design of the impinging jet solar thermal collector. This study provides a platform for scientists working in the same research field to design a better heat transfer enhancement contrivance in the form of jet control factors to improve the thermohydraulic performance by maximizing the energy output from the system.
-
Analysis of Heat Transfer and Fluid Flow in Different Shaped Roughness Elements on the Absorber Plate Solar Air Heater Duct
Energy Procedia, 2014Co-Authors: Anil KumarAbstract:Abstract An artificial roughness on the heat transfer surface in the form of projections mainly creates turbulence near the wall or breaks the Laminar Sub-Layer and thus enhances the heat transfer coefficient. In the present work the performance of a solar air heater duct provided with artificial roughness in the form of thin circular wire in V-shaped, Multi v-shaped ribs and Multi v-shaped ribs with gap geometries has been analyzed using CFD. The effect of these geometries on heat transfer and friction factor and performance enhancement was investigated covering the range of roughness parameters V-shaped, Multi v-shaped ribs, Multi v-shaped ribs with gap and working parameters. Different turbulent models have been used for the analysis heat transfer and friction factor and their results are compared with Dittus-Boelter Empirical relationship for smooth surface. Renormalization k-epsilon model based results have been found in good agreement and accordingly this model is used to predict heat transfer and friction factor in the duct.
-
Computational Fluid Dynamics Based Analysis of Angled Rib Roughened Solar Air Heater Duct
2013Co-Authors: Anil Kumar, Muneesh Sethi, Khushmeet Kumar, Sourabh Khurana, Abhilash PathaniaAbstract:An artificial roughness on the heat transfer surface in the form of projections mainly creates turbulence near the wall or breaks the Laminar Sub-Layer and thus enhances the heat transfer coefficient. In the present work the performance of a solar air heater duct provided with artificial roughness in the form of thin circular wire in discrete angled rib geometries has been analyzed using Computational Fluid Dynamics (CFD). The effect of this geometry on heat transfer and friction factor and performance enhancement was investigated covering the range of roughness parameters, P/e=8, e/D=0.043, d/W=0.25, g/e=1.0, α=60° and working parameters (Reynolds number, Re from 2,000 to 20,000). Different turbulent models have been used for the analysis heat transfer and friction factor and their results are compared with Dittus Boelter Empirical relationship for smooth surface. Renormalization k-epsilon model based results have been found in good agreement and accordingly this model is used to predict heat transfer and friction factor in the duct.
Ranchan Chauhan - One of the best experts on this subject based on the ideXlab platform.
-
Effective efficiency distribution characteristics in protruded/dimpled-arc plate solar thermal collector
Renewable Energy, 2019Co-Authors: Ranchan Chauhan, Sung Chul KimAbstract:Abstract Protruded or dimpled-arc absorbers help in accelerating the heat transfer through the rectangular air flow channels while keeping the friction factor at lowest possible value. In the present study, the effective efficiency distribution for protruded/dimpled-arc absorbers in a solar thermal collector is studied taking into account the thermal energy gain and the required pumping power for air flow as simultaneous considerations. The mathematical model used for computation has been validated and the effective efficiency characteristics have been presented as a function of flow Reynolds number. Further, the optimization of process parameters has been carried out and the design procedure for selection of optimal set of design parameters for desired value of temperature rise is discussed. The investigation concludes that the relative height and pitch affect the effective reattachment of the distributed flow whereas the arc angle due to presence of vortex legs generation by dimple/protrusion affects Laminar Sub-Layer and thereby the performance attributes. Highest effective efficiency of 72% for protruded-arc absorber for protrusion height ratio of 0.36, protrusion pitch ratio of 12 and arc angle of 60° has been achieved while maximum of 69.7% for dimpled-arc absorber is achieved on dimple height ratio of 0.3, dimple pitch ratio of 10 and arc angle of 60°.
-
Heat transfer augmentation in solar thermal collectors using impinging air jets: A comprehensive review
Renewable & Sustainable Energy Reviews, 2018Co-Authors: Ranchan Chauhan, Tej Singh, Nitin Kumar, N.s. Thakur, Raj Kumar, Anil KumarAbstract:Jet impingement has led to considerable augmentation in heat transfer characteristics of solar thermal collectors. The impinging air jets are characterized by different control factors where it becomes essential to study their dependence on performance defining criteria so as to arrive at the optimized impinging jet geometry which create one or combination of following conditions favorable for heat transfer with minimal friction losses inside the collector: (a) breaking Laminar sub layer (b) increasing turbulent intensity (c) increasing heat transfer area, and (d) generating vortex or secondary flows. The present article examines the thermodynamic behavior of solar thermal collector, review the experimental investigations reported in the literature to study the dependence of control factors on heat transfer and friction characteristics and review the multi criteria decision making methods towards optimization of control factor combinations for an optimal design of the impinging jet solar thermal collector. This study provides a platform for scientists working in the same research field to design a better heat transfer enhancement contrivance in the form of jet control factors to improve the thermohydraulic performance by maximizing the energy output from the system.
Vikas J. Lakhera - One of the best experts on this subject based on the ideXlab platform.
-
Thermo-hydraulic performance analysis of a solar air heater roughened with reverse NACA profile ribs
Applied Thermal Engineering, 2020Co-Authors: Yogesh M. Patel, Sanjay V. Jain, Vikas J. LakheraAbstract:Abstract The solar air heater is subjected to a low convective heat transfer coefficient on account of the formation of the Laminar Sub-Layer between the absorber plate and flowing air. To increase the heat transfer coefficient, the Laminar Sub-Layer can be interrupted with the use of artificial roughness (turbulator) on the absorber plate. In the present analysis, the effects of novel type of roughness element in the form of NACA 0040 profile ribs in the reverse position are studied on the performance of the solar air heater. The effects of relative roughness pitch (P/e) and relative roughness height (e/D) were studied for the Reynolds number (Re) ranging from 6000 to 18,000. Among the various roughness parameters, NACA 0040 profile ribs provided in the reverse direction with P/e as 5 and e/D as 0.065 was found to be the optimum. The thermo-hydraulic performance parameter for this case was found to be 2.53 at a Reynolds number of 6000. The experimental results validated the numerical results, and the maximum deviation was found to be 4.84%. An empirical correlation was developed for prediction of Nu and f in terms of Re and e/D and found to conform within ±3% of the corresponding experimental values.
K. Vasudeva Karanth - One of the best experts on this subject based on the ideXlab platform.
-
Experimental investigations on a cross flow solar air heater having perforated circular absorber plate for thermal performance augmentation
Solar Energy, 2020Co-Authors: Shreyas P. Shetty, Akhil Paineni, Madhav Kande, N. Madhwesh, N. Yagnesh Sharma, K. Vasudeva KaranthAbstract:Abstract Conventional solar air heaters are associated with low thermal and thermohydraulic efficiencies due to the formation of Laminar Sub-Layer created in the region where the flowing air comes in contact with the absorber plate. Hence there is a need to break this Laminar Sub-Layer to improve the convective heat transfer capability of the collector. In this study, a solar air heater with perforated circular absorber plate is adopted with cross-flow configuration. The thermal performance is investigated for 5, 8 and 10 mm perforation vent diameters as well as 24, 36 and 54 number of vents. The configuration with perforated absorber plate provides a better convective heat transfer and thereby leads to better thermal and thermohydraulic efficiencies. This is compared with the base model in the absence of perforated absorber plate for a wide operating range of Reynolds numbers from 3000 to 21000. It is found from the study that when there is an increase in the number of perforations, there is a significant increase in thermohydraulic efficiency, even though there is a marginal drop in thermal efficiency. Also, with an increase in diameter of the perforated vents there is a remarkable improvement in the thermohydraulic efficiency though there is a marginal drop in the thermal efficiency. The best operating range of Reynolds number for the perforated solar collector is found to be between 9,000 to 15,000 having 54 vent perforations corresponding to 8 mm diameter and offers an efficiency of 75.55%.
-
A Turbulence Inducer Side Wall Treatment for a Solar Collector for Performance Improvement
Procedia Manufacturing, 2019Co-Authors: K. Vasudeva Karanth, N. Yagnesh Sharma, N. MadhweshAbstract:Abstract It is generally found that solar collector has lower conversion efficiencies due to low density of the carrying air medium. This issue has been an important focus for many researchers who are working hard to improve the efficacy of conversion by various design interventions for the absorber itself. However, there is vast scope for improving the efficiency by means of creating turbulence of the through flow by uniquely designing flow turbulators along the side wall of the duct itself of various designs discussed in this paper. These Turbulence generators are able to brake the Laminar Sub-Layer at the wall. This will result in a higher momentum exchange among the heated air particles. In this paper, an improved turbulence intensity is created so as to enhance the convective heat transfer capability of the medium. Several parametric configurations of the turbulent generators of different shapes are studied and presented in this paper, corresponding to various geometry and under different mass flow rate considerations so as to arrive at an optimum design of the Turbulators.
Sung Chul Kim - One of the best experts on this subject based on the ideXlab platform.
-
Effective efficiency distribution characteristics in protruded/dimpled-arc plate solar thermal collector
Renewable Energy, 2019Co-Authors: Ranchan Chauhan, Sung Chul KimAbstract:Abstract Protruded or dimpled-arc absorbers help in accelerating the heat transfer through the rectangular air flow channels while keeping the friction factor at lowest possible value. In the present study, the effective efficiency distribution for protruded/dimpled-arc absorbers in a solar thermal collector is studied taking into account the thermal energy gain and the required pumping power for air flow as simultaneous considerations. The mathematical model used for computation has been validated and the effective efficiency characteristics have been presented as a function of flow Reynolds number. Further, the optimization of process parameters has been carried out and the design procedure for selection of optimal set of design parameters for desired value of temperature rise is discussed. The investigation concludes that the relative height and pitch affect the effective reattachment of the distributed flow whereas the arc angle due to presence of vortex legs generation by dimple/protrusion affects Laminar Sub-Layer and thereby the performance attributes. Highest effective efficiency of 72% for protruded-arc absorber for protrusion height ratio of 0.36, protrusion pitch ratio of 12 and arc angle of 60° has been achieved while maximum of 69.7% for dimpled-arc absorber is achieved on dimple height ratio of 0.3, dimple pitch ratio of 10 and arc angle of 60°.
