Showing papers by "Shankar Narayanan published in 2013"

Design and Optimization of High Performance Adsorption-Based Thermal Battery

Abstract: Electric vehicle (EV) technology faces a substantial challenge in terms of driving range, especially when the vehicle’s climate control system relies entirely on the onboard electric battery. Therefore, we are developing an advanced adsorption-based thermal battery (ATB) capable of delivering both heating and cooling for electric vehicles with minimal use of the electric battery bank. While adsorption based climate control systems offer the advantage of direct usage of primary thermal energy sources for operation, they typically have low COP values, and are often bulky and heavy. A compact and lightweight ATB is necessary to replace existing climate control systems in EVs that use electric battery for operation. In this paper, we present a detailed computational analysis of adsorption kinetics taking place within an adsorption bed that is capable of delivering large cooling and heating capacities by making use of novel adsorbents. The overall design of the adsorption bed, which is a critical element in achieving a high performance thermal battery, is also discussed. To make performance predictions, we characterized the adsorbents to obtain their thermophysical and transport properties as well as adsorption characteristics. The model consequently incorporates these measured properties to predict the performance variation as a function of time. This work provides the critical parameters affecting heating and cooling rates, and identifies avenues for further improvement in the overall performance of the thermal battery.Copyright © 2013 by ASME

Zeolite Y adsorbents with high vapor uptake capacity and robust cycling stability for potential applications in advanced adsorption heat pumps

Abstract: Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg2+ ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg,Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the labscale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N2 sorption, 27Al/29Si MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick's 2nd law and D-R equation regressions. Among these, close examination of sorption isotherms for H2O and N2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications.

Finite element analysis of forming limits for stretch forming of perforated aluminium sheet metals

Abstract: Stretch forming is one of the sheet metal forming process in which sheets are stretched to get the required shape. Formability of sheet metal is its ability to form when it is subjected to cold working process. Formability of a sheet metal is measured by Forming Limit Diagram (FLD/FLC). The limiting or failure strains in sheet metal forming are best represented by a forming limit curve which indicates the onset of necking over all possible combinations of strains in the plane. An attempt is made here to simulate the stretch forming of perforated sheet metals thereby studying its limiting strain. The uniaxial stretching and biaxial stretching are performed to get forming limit diagram. The influence of open area, and hole shape on FLD are studied. Perforated sheet is modelled with finite element method by using commercial FEA software ANSYS to calculate the major strain, minor strain and failure load for both uniaxial stretching and biaxial stretching of perforated sheet metal. It has been found that increasing in open area reduces the limiting major and minor strain. It has also been studied the influence of hole shape and punch shape on limiting major and minor strain.

Experimental Characterization of Adsorption and Transport Properties for Advanced Thermo-Adsorptive Batteries

Abstract: Thermal energy storage has received significant interest for delivering both heating and cooling in electric vehicles, to minimize the use of the on-board electric batteries for heating, ventilation and air-conditioning (HVAC). An advanced thermo-adsorptive battery (ATB) is currently being developed, to provide both heating and cooling for an electric vehicle. We present a detailed thermophysical and physicochemical characterization of adsorptive materials for the development of the ATB. We discuss the feasibility of using contemporary adsorptive materials, such as zeolite 13X, by carrying out a detailed experimental characterization. In this study, zeolite 13X is combined with aluminum hydroxide (Al(OH)3) as a binder to improve the thermal conductivity. We also investigate the effect of densification on the overall transport characteristics of the adsorbent-binder composite material. Accordingly, the effective thermal conductivity, surface area, adsorption capacity and surface chemistry were characterized using the laser flash technique, surface sorption analyzer, thermogravimetric analyzer, and x-ray scattering technique. Thermal conductivity predictions of both zeolite 13X and its combination with the binder were made with existing conductivity models. Thermal conductivity in excess of 0.4 W/mK was achieved with the addition of 6.4 wt.% of Al(OH)3. However, a 10.6 % decrease in adsorption capacity was also observed. The experimental characterization presented herein is an essential step towards the development of the proposed ATB for next-generation electric vehicles.Copyright © 2013 by ASME

Monolithically integrated bi-directional heat pump

Abstract: Monolithically integrated heat pump. The heat pump includes an adsorbent/absorbent condenser forming a hot terminal integrated with a phase change heat exchanger forming a cold terminal. The adsorbent/absorbent condenser and the phase change heat exchanger are integrated into a single pressure vessel.

Design and Optimization of High Performance Adsorption-Based Thermal Battery

Abstract: Electric vehicle (EV) technology faces a substantial challenge in terms of driving range, especially when the vehicle’s climate control system relies entirely on the onboard electric battery. Therefore, we are developing an advanced adsorption-based thermal battery (ATB) capable of delivering both heating and cooling for electric vehicles with minimal use of the electric battery bank. While adsorption based climate control systems offer the advantage of direct usage of primary thermal energy sources for operation, they typically have low COP values, and are often bulky and heavy. A compact and lightweight ATB is necessary to replace existing climate control systems in EVs that use electric battery for operation. In this paper, we present a detailed computational analysis of adsorption kinetics taking place within an adsorption bed that is capable of delivering large cooling and heating capacities by making use of novel adsorbents. The overall design of the adsorption bed, which is a critical element in achieving a high performance thermal battery, is also discussed. To make performance predictions, we characterized the adsorbents to obtain their thermophysical and transport properties as well as adsorption characteristics. The model consequently incorporates these measured properties to predict the performance variation as a function of time. This work provides the critical parameters affecting heating and cooling rates, and identifies avenues for further improvement in the overall performance of the thermal battery. NOMENCLATURE