Sensorless Battery Internal Temperature Estimation using a Kalman Filter with Impedance Measurement

This study presents a method of estimating battery cell core and surface temperature using a thermal model coupled with electrical impedance measurement, rather than using direct surface temperature measurements. This is advantageous over previous methods of estimating temperature from impedance, which only estimate the average internal temperature. The performance of the method is demonstrated experimentally on a 2.3 Ah lithium-ion iron phosphate cell fitted with surface and core thermocouples for validation. An extended Kalman filter, consisting of a reduced order thermal model coupled with current, voltage and impedance measurements, is shown to accurately predict core and surface temperatures for a current excitation profile based on a vehicle drive cycle. A dual extended Kalman filter (DEKF) based on the same thermal model and impedance measurement input is capable of estimating the convection coefficient at the cell surface when the latter is unknown. The performance of the DEKF using impedance as the measurement input is comparable to an equivalent dual Kalman filter using a conventional surface temperature sensor as measurement input.Comment: 10 pages, 9 figures, accepted for publication in IEEE Transactions on Sustainable Energy, 201

Experimental study on transcritical Rankine cycle (TRC) using CO2/R134a mixtures with various composition ratios for waste heat recovery from diesel engines

A carbon dioxide (CO2) based mixture was investigated as a promising solution to improve system performance and expand the condensation temperature range of a CO2 transcritical Rankine cycle (C-TRC). An experimental study of TRC using CO2/R134a mixtures was performed to recover waste heat of engine coolant and exhaust gas from a heavy-duty diesel engine. The main purpose of this study was to investigate experimentally the effect of the composition ratio of CO2/R134a mixtures on system performance. Four CO2/R134a mixtures with mass composition ratios of 0.85/0.15, 0.7/0.3, 0.6/0.4 and 0.4/0.6 were selected. The high temperature working fluid was expanded through an expansion valve and then no power was produced. Thus, current research focused on the analysis of measured operating parameters and heat exchanger performance. Heat transfer coefficients of various heat exchangers using supercritical CO2/R134a mixtures were provided and discussed. These data may provide useful reference for cycle optimization and heat exchanger design in application of CO2 mixtures. Finally, the potential of power output was estimated numerically. Assuming an expander efficiency of 0.7, the maximum estimations of net power output using CO2/R134a (0.85/0.15), CO2/R134a (0.7/0.3), CO2/R134a (0.6/0.4) and CO2/R134a (0.4/0.6) are 5.07 kW, 5.45 kW, 5.30 kW, and 4.41 kW, respectively. Along with the increase of R134a composition, the estimation of net power output, thermal efficiency and exergy efficiency increased at first and then decreased. CO2/R134a (0.7/0.3) achieved the maximum net power output at a high expansion inlet pressure, while CO2/R134a (0.6/0.4) behaves better at low pressure

Preliminary experimental comparison and feasibility analysis of CO2/R134a mixture in Organic Rankine Cycle for waste heat recovery from diesel engines

This paper presents results of a preliminary experimental study of the Organic Rankine Cycle (ORC) using CO2/R134a mixture based on an expansion valve. The goal of the research was to examine the feasibility and effectiveness of using CO2 mixtures to improve system performance and expand the range of condensation temperature for ORC system. The mixture of CO2/R134a (0.6/0.4) on a mass basis was selected for comparison with pure CO2 in both the preheating ORC (P-ORC) and the preheating regenerative ORC (PR-ORC). Then, the feasibility and application potential of CO2/R134a (0.6/0.4) mixture for waste heat recovery from engines was tested under ambient cooling conditions. Preliminary experimental results using an expansion valve indicate that CO2/R134a (0.6/0.4) mixture exhibits better system performance than pure CO2. For PR-ORC using CO2/R134a (0.6/0.4) mixture, assuming a turbine isentropic efficiency of 0.7, the net power output estimation, thermal efficiency and exergy efficiency reached up to 5.30 kW, 10.14% and 24.34%, respectively. For the fitting value at an expansion inlet pressure of 10 MPa, the net power output estimation, thermal efficiency and exergy efficiency using CO2/R134a (0.6/0.4) mixture achieved increases of 23.3%, 16.4% and 23.7%, respectively, versus results using pure CO2 as the working fluid. Finally, experiments showed that the ORC system using CO2/R134a (0.6/0.4) mixture is capable of operating stably under ambient cooling conditions (25.2–31.5 °C), demonstrating that CO2/R134a mixture can expand the range of condensation temperature and alleviate the low-temperature condensation issue encountered with CO2. Under the ambient cooling source, it is expected that ORC using CO2/R134a (0.6/0.4) mixture will improve the thermal efficiency of a diesel engine by 1.9%

Estimation of Thermal and Hydraulic Characteristics of Compact Brazed Plate Heat Exchangers

This thesis work presents various performance estimation methods of compact brazed plate heat exchangers (BPHE) operating in single phase, condenser, evaporator, cascaded and transcritical applications. Such methods play a vital role in development of heat exchanger selection software and during geometry parameter estimation in the new product development process. The suitability of employing commercial computational fluid dynamics (CFD) codes for estimating single phase thermal and hydraulic performance is investigated. Parametric studies are conducted on geometries of single phase fluid sections to isolate and quantify the influence of individual geometric parameters. The influence of mesh characteristics, choice of boundary conditions and turbulent flow modeling on the accuracy of the thermal and hydraulic predictions is presented. Benefits of simulation of fluid flow in entire channels and characteristics of channel flow for different geometric patterns are also presented. A computationally light, general, robust and continuous rating calculation method is developed for implementation in BPHE selection software. The pressure-enthalpy based method provides a generic rating core for various types of applications and provides extensive post processing information of the heat transfer process. General single phase thermal and hydraulic empirical correlations are developed as functions of plate geometric parameters. For facilitating better integration of the developed calculation method with other refrigeration system simulation software, first or higher order continuity is maintained in the sub-routines used for calculating local heat transfer coefficients and refrigerant properties. A new finite grid interpolation method is developed for fast and accurate retrieval of refrigerant properties. The developed method is currently implemented in SSPG7 (BPHE selection software of SWEP International AB) for supporting transcritical CO2 calculations and cascaded heat exchanger calculations. Additionally, the methods developed for single phase and two phase test data evaluation based on meta-heuristic optimization routines is also presented. The application and results of using the developed rating models for various types of calculations is summarized. Other topics such as influence of variable fluid properties on BPHE rating calculations, influence of multi-pass flow arrangement on lumped BPHE rating calculations are briefly presented

Quark-Hadron Phase Transitions in Viscous Early Universe

Based on hot big bang theory, the cosmological matter is conjectured to undergo QCD phase transition(s) to hadrons, when the universe was about $1-10 \mu$s old. In the present work, we study the quark-hadron phase transition, by taking into account the effect of the bulk viscosity. We analyze the evolution of the quantities relevant for the physical description of the early universe, namely, the energy density $\rho$, temperature $T$, Hubble parameter $H$ and scale factor $a$ before, during and after the phase transition. To study the cosmological dynamics and the time evolution we use both analytical and numerical methods. By assuming that the phase transition may be described by an effective nucleation theory (prompt {\it first-order} phase transition), we also consider the case where the universe evolved through a mixed phase with a small initial supercooling and monotonically growing hadronic bubbles. The numerical estimation of the cosmological parameters, $a$ and $H$ for instance, makes it clear that the time evolution varies from phase to phase. As the QCD era turns to be fairly accessible in the high-energy experiments and the lattice QCD simulations, the QCD equation of state is very well defined. In light of this, we introduce a systematic study of the {\it cross-over} quark-hadron phase transition and an estimation for the time evolution of Hubble parameter.Comment: 27 pages, 17 figures, revtex style (To appear in Phys. Rev. D). arXiv admin note: text overlap with arXiv:gr-qc/040404

Kinetic Modeling of Isothermal or Non-isothermal Adsorption in a Pellet: Application to Adsorption Heat Pumps

Understanding the interaction between a fluid and a solid phase is of fundamental importance to the design of an adsorption process. Because the heat effects associated with adsorption are comparatively large, the assumption of isothermal behavior is a valid approximation only when uptake rates are relatively slow. In this article, we propose to determine when it is needed to choose the isothermal or non-isothermal assumption according to two physical parameters alpha (ratio convection/capacity) and beta(quantity of energy/capacity). The proposed problem is solved by a mathematical method in the Laplace domain. When alpha-> infinite (infinitely high heat transfer coefficient) or beta->0(infinitely large heat capacity), the limiting case is isothermal. When the diffusion is rapid (alpha<10) the kinetics of sorption is controlled entirely by heat transfer. If the adsorption process is to be used as a heat pump, it shall be represented by an isotherm model with alpha and beta as high as possible