Papers by Dr. Ravita Lamba
2022 IEEE 10th Power India International Conference (PIICON)
Journal of Energy Storage
Energy, 2016
The exoreversible and irreversible thermodynamic models of a two stage thermoelectric cooler (TTE... more The exoreversible and irreversible thermodynamic models of a two stage thermoelectric cooler (TTEC) considering Thomson effect in conjunction with Peltier, Joule and Fourier heat conduction effects have been investigated using exergy analysis. New expressions for the interstage temperature, optimum current for the maximum cooling power, energy and exergy efficiency conditions, energy efficiency and exergy efficiency of a TTEC are derived as well. The number of thermocouples in the first and second stages of a TTEC for the maximum cooling power, energy and exergy efficiency conditions are optimized. The results show that the exergy efficiency is lower than the energy efficiency e.g., in an irreversible TTEC with total 30 thermocouples, heat sink temperature (T H) of 300 K and heat source temperature (T C) of 280 K, the obtained maximum cooling power, maximum energy and exergy efficiency are 20.37 W, 0.7147 and 5.10% respectively. It has been found that the Thomson effect increases the cooling power and energy efficiency of the TTEC system e.g., in the exoreversible TTEC the cooling power and energy efficiency increased from 14.87 W to 16.36 W and from 0.4079 to 0.4998 respectively for DT C of 40 K when Thomson effect is considered. It has also been found that the heat transfer area at the hot side of an irreversible TTEC should be higher than the cold side for maximum performance operation. This study will help in the designing of the actual multistage thermoelectric cooling systems.
2022 IEEE IAS Global Conference on Emerging Technologies (GlobConET)
Journal of Cleaner Production
International Journal of Exergy
Waste heat is inevitable in any human endeavour. Thus, the need to develop thermal energy convers... more Waste heat is inevitable in any human endeavour. Thus, the need to develop thermal energy conversion systems. Thermoelectric generators (TEGs) are solidstate devices that convert waste heat to useful electricity. They have found various applications in converting solar energy to electricity, harvesting exhaust waste heat in automobiles and power plants and providing power for spacecrafts by converting the heat released during radioactive decay to electricity. Despite these perks, they are characterised by very low efficiencies. Thus, several efficiency enhancement strategies such as material modification and leg geometry alteration have been introduced. Pertaining the latter, the trapezoidal shaped geometry has been studied extensively. Although it offers a higher efficiency compared to the conventional rectangular leg geometry, it still exhibits higher thermal stresses and consequently, a reduced lifespan. A conical frustum shaped TE pin has not been conceived yet. The investigation of this leg geometry is important since it might provide a higher efficiency and operating lifetime compared to the current trapezoidal leg. Thus, a thoroughly validated numerical model is used in evaluating the performance of three TEGs comprising rectangular, trapezoidal and conical frustum shaped TE legs. Results indicate that the proposed conical frustum leg TEG enhances the power density and exergy efficiency of the trapezoidal device by 20% and 23%, respectively. Also, the thermal stress and thermodynamic irreversibilities of the trapezoidal leg TEG are reduced by 2% and 0.5%, respectively.
Topical Drifts in Intelligent Computing
International Journal of Energy Research, 2021
Thermal Science and Engineering Progress, 2018
The thermoelectric coolers (TECs) are being used widely in cooling of many electronic devices bec... more The thermoelectric coolers (TECs) are being used widely in cooling of many electronic devices because of their stable operation. The cooling capacity and energy efficiency are two important performance parameter of a thermoelectric cooler (TEC) which can also be enhanced by changing the geometric configuration of thermoelectric leg. In this
Energy Conversion and Management, 2019
In this work, a novel technique to improve the performance of Peltier cooler under varying electr... more In this work, a novel technique to improve the performance of Peltier cooler under varying electric pulse conditions has been studied with the use of phase change material (PCM). The 2D heat transfer model of Peltier cooler along with heat sink has been developed and studied numerically. The results show that the cold side temperature of Peltier cooler with PCM has been reduced significantly from −14.5°C to −17.5°C under pulse operation as compared to the Peltier cooler without PCM under pulse operation. It is also found that, there is no significant reduction in COP of the Peltier cooler under pulse operation with PCM as compared to pulse operation without PCM. These studies have been carried out by varying the hot side heat transfer coefficient, fill volume of PCM in heat sink and the shape of the electric pulse. It has been observed that the super cooling of Peltier cooler increases with increase in fill volume of PCM. Furthermore, it has been found that the super cooling performance of the Peltier cooler is more predominant with the square pulse as compared to ramp and triangular pulses.
Journal of Electronic Materials, 2018
A thermodynamic model for a concentrating solar thermoelectric generator considering the Thomson ... more A thermodynamic model for a concentrating solar thermoelectric generator considering the Thomson effect combined with Fourier heat conduction, Peltier, and Joule heating has been developed and optimized in MATLAB environment. The temperatures at the hot and cold junctions of the thermoelectric generator were evaluated by solving the energy balance equations at both junctions. The effects of the solar concentration ratio, input electrical current, number of thermocouples, and electrical load resistance ratio on the power output and energy and exergy efficiencies of the system were studied. Optimization studies were carried out for the STEG system, and the optimum number of thermocouples, concentration ratio, and resistance ratio determined. The results showed that the optimum values of these parameters are different for conditions of maximum power output and maximum energy and exergy efficiency. The optimum values of the concentration ratio and load resistance ratio for maximum energy efficiency of 5.85% and maximum exergy efficiency of 6.29% were found to be 180 and 1.3, respectively, with corresponding power output of 4.213 W. Furthermore, at higher concentration ratio (C = 600), the optimum number of thermocouples was found to be 101 for maximum power output of 13.75 W, maximum energy efficiency of 5.73%, and maximum exergy efficiency of 6.16%. Moreover, the optimum number of thermocouple was the same for conditions of maximum power output and energy and exergy efficiency. The results of this study may provide insight for design of actual concentrated solar thermoelectric generator systems.
Journal of Thermal Analysis and Calorimetry, 2019
In the present work, a novel technique has been developed to enhance the thermal performance of a... more In the present work, a novel technique has been developed to enhance the thermal performance of a thermoelectric cooler (TEC) by integrating with phase-change material (PCM). The PCM has been integrated at the hot side of the thermoelectric cooler to maintain constant and relatively low temperature. The study has been carried out with variable geometric parameters of the heat sink, variable cooling load conditions, variable input currents to the TEC and with different PCMs. The results show that there is a significant reduction in both hot and cold side temperatures of the thermoelectric cooler with the use of PCM. For a typical operating condition in the TEC with two thermocouples (2 mm 9 2 mm 9 3 mm each) under cooling load of 0.03 W and convective heat transfer coefficient of 5 Wm-2 K-1 , the hot and cold side temperatures of the TEC have been reduced from 52 to 30°C and 25 to 12°C, respectively, with the use of PCM. The coefficient of performance of the TEC integrated with PCM has been estimated and it has been found to be 30% higher than the TEC without PCM for a cooling load of 0.05 W. Moreover, the thermal performance of TEC has been studied with variable fill volume of PCM in the heat sink. It has been found that the increase in fill volume of PCM increases the thermal performance of the TEC. This study has been carried out with different PCMs and similar performance enhancements have been observed.
Journal of Cleaner Production, 2019
The applicability of phase change materials (PCMs) for the thermal management of low concentrated... more The applicability of phase change materials (PCMs) for the thermal management of low concentrated photovoltaic systems is explored in the current research work. Extended surfaces on the back surface of the PCM container are proposed with its small portion extruded to the outside. PCM thicknesses of 80 mm, 100 mm, and 120 mm are investigated, and an 80 mm thick PCM system is considered as the base configuration. Systems with 2 fins, 3 fins, and 4 fins are analyzed with two different fin lengths of 30 mm and 40 mm inside the PCM enclosure. Two-dimensional transient numerical analysis has been carried out with ANSYS FLUENT using the enthalpy porosity method. The nonuniform melting behavior of PCMs due to natural convection inside the molten PCMs is considered during the analysis using a Boussinesq approximation. The result shows that the proposed 4 fin configuration enhances the melting time by 6000 s compared to the no fin system, reduces the average PCM temperature inside the container by 18%, and decreases the heater surface temperature by 16%.
Energy Conversion and Management, 2018
In this study, a theoretical model of a concentrated photovoltaic-thermoelectric hybrid system ha... more In this study, a theoretical model of a concentrated photovoltaic-thermoelectric hybrid system has been developed based on first and second laws of thermodynamics and analysed in MATALB. A numerical method has been exploited to determine the temperatures of photovoltaic module (PV) and hot and cold side of thermoelectric generator (TEG) by iteratively solving the energy balance equations. The proposed study takes into account the effects of hot and cold side thermal resistances, thermoelectric properties, fill factor, geometry of thermoelectric module, load resistance and electrical current on the performance of the hybrid system. The results show that the optimum value of ratio of TEG load resistance to TEG internal resistance, m for maximum power output and efficiency of thermoelectric module is higher than unity. The concentration ratio should also be optimized to achieve maximum PV power output. For the fixed leg length of 5 mm and CG value of 1 kW/m 2 , the optimum m corresponding to maximum power output and maximum efficiency of the hybrid system is 0.5. The maximum power output and efficiency of the hybrid system increase by 5% as compared to the corresponding values of concentrated PV system. Moreover, at higher concentration ratios, the contribution of thermoelectric power to the power output of hybrid system is higher. Further, for other parameters fixed, the optimum value of CG for maximum power output of the hybrid system is 5.5 kW/m 2 and it is 14% higher than the corresponding power output of CPV system alone. This improvement in the performance of hybrid system is added by the thermoelectric generator module. The results of this analysis incorporating the electrical and thermal contact resistances of thermoelectric device, may be helpful to envisage the design of a real photovoltaic-thermoelectric hybrid system.
Energy Conversion and Management, 2017
To improve the power output and efficiency of the thermoelectric generator system, the variation ... more To improve the power output and efficiency of the thermoelectric generator system, the variation in the thermoelectric leg configuration is another option. In this paper, the thermodynamic analysis of exoreversible thermoelectric generator including influence of Thomson effect as well as influence of leg geometry on the power output and efficiency of the device has been carried out. The modified expressions for dimensionless figure of merit, power output, irreversibilities, energy and exergy efficiency considering Thomson effect have been derived analytically. The effects of various parameters such as dimensionless temperature ratio (h), shape parameter (R A), Thomson effect and load resistance ratio (R L /R 0) on the power output, energy and exergy efficiency have been studied. The operating range for shape parameter has been found which improves the power output, energy and exergy efficiency of the device, however, the optimum operating point corresponding to maximum power output is different from that of the maximum energy and exergy efficiency. The results of this study shows that when the shape parameter is increased from 1 (flat plate TEG) to 2 (trapezoidal TEG), then the energy and exergy efficiency improve by 2.32% and 2.31% respectively with a 1.3% decrease in power output at R L /R 0 = 10 and h = 0.5. This study will help in designing of the improved thermoelectric generator systems for different leg geometries.
Renewable and Sustainable Energy Reviews, 2017
The thermodynamic basis of energy conversion systems is being utilized to carry out performance a... more The thermodynamic basis of energy conversion systems is being utilized to carry out performance assessments and feasibility studies on photovoltaic (PV) systems in order to improve the design and efficiency of the system. The thermodynamic process of converting solar radiation directly into electrical energy, i.e. solar PV energy conversion, has been established, which includes electrical power generation, optical/thermal losses and electrical losses. In this paper, the thermodynamic modeling based on energy, endoreversible, entropy and exergy models of solar PV energy conversion system has been presented using the first and second law of thermodynamic, with an updated literature survey. The energetic and exergetic efficiencies of PV system have been evaluated and the reported theoretical upper limit efficiency of PV system using different thermodynamic models have been presented.
International Journal of Energy Research, 2017
An alternate option for improving the performance of the thermoelectric heat pump (TEHP) is the v... more An alternate option for improving the performance of the thermoelectric heat pump (TEHP) is the variation in thermoelectric leg configuration. In this paper, the thermodynamic model based on first and second law of thermodynamics for an exoreversible TEHP including influence of Thomson effect as well as leg geometry on the coefficient of performance and heating load of the device has been developed and optimized. Modified expressions have been derived analytically for dimensionless heating load, irreversibilities, figure of merit, energy, and exergy efficiency. The effects of operating and geometry parameters such as shape parameter (A c /A h), temperature ratio (T c /T h), Thomson effect, thermal and electrical contact resistances on the coefficient of performance, and heating load of the TEHP have been analysed. The results indicate that the Thomson effect has adverse effect on heating load of the system. The optimal parameters obtained through GA optimization process have been compared with the optimal parameters obtained through analytical method which proved the validity of GA optimization method for optimization of TEHP. After the testing, the GA optimization has been performed to determine the optimum parameters corresponding to maximum energy efficiency and maximum heating load. It was found that the GA population converges quickly after 20 runs only which proved the GA as time and cost-effective optimization tool. This study will be useful for designing of practical TEHP systems of different leg geometries.
Energy Conversion and Management, 2016
Abstract In this study, a thermodynamic model for analysing the performance of a concentrated pho... more Abstract In this study, a thermodynamic model for analysing the performance of a concentrated photovoltaic–thermoelectric generator (CPV–TEG) hybrid system including Thomson effect in conjunction with Seebeck, Joule and Fourier heat conduction effects has been developed and simulated in MATALB environment. The expressions for calculating the temperature of photovoltaic (PV) module, hot and cold sides of thermoelectric (TE) module are derived analytically as well. The effect of concentration ratio, number of thermocouples in TE module, solar irradiance, PV module current and TE module current on power output and efficiency of the PV, TEG and hybrid PV–TEG system have been studied. The optimum concentration ratio corresponding to maximum power output of the hybrid system has been found out. It has been observed that by considering Thomson effect in TEG module, the power output of the PV, TE and hybrid PV–TEG systems decreases and at C = 1 and 5, it reduces the power output of hybrid system by 0.7% and 4.78% respectively. The results of this study may provide basis for performance optimization of a practical irreversible CPV–TEG hybrid system.
Uploads
Papers by Dr. Ravita Lamba