Showing papers on "Thermal reservoir published in 2016"
TL;DR: In this article, the authors present a review of current and future liquid, gas, supercritical, two-phase and particulate heat transfer fluid (HTF) technologies for solar thermal power plants.
Abstract: The Heat transfer fluid (HTF) is a key component of solar thermal power plant because it significantly impacts the receiver efficiency, determines the type of thermodynamic cycle and the performance it can achieve, and determines the thermal energy storage technology that must be used. This paper reviews current and future liquid, gas, supercritical, two-phase and particulate HTFs. Thermophysical properties are presented as well as correlations to determine the receiver tube-HTF heat transfer coefficients. Variations of convective heat transfer coefficients as a function of temperature are illustrated for all selected HTFs in their stable operation temperature ranges. Finally, recent developments on new HTFs working at 700 °C and beyond are discussed.
227 citations
TL;DR: It is demonstrated that a thermal transistor can be made up with a quantum system of three interacting subsystems, coupled to a thermal reservoir each, and high amplification can be obtained in a wide range of energy parameters and temperatures.
Abstract: We demonstrate that a thermal transistor can be made up with a quantum system of three interacting subsystems, coupled to a thermal reservoir each. This thermal transistor is analogous to an electronic bipolar one with the ability to control the thermal currents at the collector and at the emitter with the imposed thermal current at the base. This is achieved by determining the heat fluxes by means of the strong-coupling formalism. For the case of three interacting spins, in which one of them is coupled to the other two, that are not directly coupled, it is shown that high amplification can be obtained in a wide range of energy parameters and temperatures. The proposed quantum transistor could, in principle, be used to develop devices such as a thermal modulator and a thermal amplifier in nanosystems.
203 citations
TL;DR: By introducing a modified quantum Otto cycle, this work fully characterizes operational regimes forbidden in the standard case, such as refrigeration and work extraction at the same time, accompanied by efficiencies equal to unity.
Abstract: We analyze the entropy production and the maximal extractable work from a squeezed thermal reservoir. The nonequilibrium quantum nature of the reservoir induces an entropy transfer with a coherent contribution while modifying its thermal part, allowing work extraction from a single reservoir, as well as great improvements in power and efficiency for quantum heat engines. Introducing a modified quantum Otto cycle, our approach fully characterizes operational regimes forbidden in the standard case, such as refrigeration and work extraction at the same time, accompanied by efficiencies equal to unity.
170 citations
TL;DR: In this paper, a two-dimensional finite volume based numerical model along with enthalpy-porosity technique is employed to simulate the phase change of storage media during the discharging mode.
115 citations
TL;DR: In this paper, the authors developed a three-dimensional transient model, which describes the multi-physical coupling of thermal (T), hydraulic (H), and mechanical (M) processes during heat extraction of enhanced geothermal systems.
96 citations
TL;DR: In this article, the transient response of packed bed latent heat thermal energy storage system in removing fluctuations in the heat transfer fluid (HTF) temperature during the charging and discharging period is presented.
85 citations
TL;DR: In this article, phase change materials (PCM) were proposed to use as backfill material instead of common materials to improve the performance of ground source heat pump (GSHP) systems.
79 citations
TL;DR: In this article, a metal-hydride (MH) bed integrating a Phase Change Material (PCM) as latent heat storage system is appropriately selected and investigated in a metal hydride-hydrogen storage tank.
75 citations
TL;DR: In this paper, the authors investigated the generation of entropy and transfer of heat during forced convection of a nanofluid through a partially-filled porous channel, where a fully developed flow in a channel with a central porous insert and under constant heat flux boundary condition was considered.
70 citations
TL;DR: In this article, the effects of surface dependent heat source/sink, viscosity and thermal conductivity variations on unsteady flow of Casson fluid over a vertical cone and flat plate were investigated.
67 citations
TL;DR: The Szilard map is introduced, a deterministic chaotic system that encapsulates the measurement, control, and erasure protocol by which Maxwellian demons extract work from a heat reservoir and symmetrizes the demon and the thermodynamic system, allowing one to explore their functionality and recover the fundamental trade-off between the thermodynamics costs of dissipation due to measurement and those due to erasure.
Abstract: We introduce a deterministic chaotic system-the Szilard map-that encapsulates the measurement, control, and erasure protocol by which Maxwellian demons extract work from a heat reservoir. Implementing the demon's control function in a dynamical embodiment, our construction symmetrizes the demon and the thermodynamic system, allowing one to explore their functionality and recover the fundamental trade-off between the thermodynamic costs of dissipation due to measurement and those due to erasure. The map's degree of chaos-captured by the Kolmogorov-Sinai entropy-is the rate of energy extraction from the heat bath. Moreover, an engine's statistical complexity quantifies the minimum necessary system memory for it to function. In this way, dynamical instability in the control protocol plays an essential and constructive role in intelligent thermodynamic systems.
TL;DR: In this article, the authors extended a previous enhanced geothermal system (EGS) model by implementing pressure and temperature-dependent thermophysical properties of real water and super-critical carbon dioxide (SCCO2), and employed the new model to simulate the long-term heat extraction processes of water-EGS and SCCO+EGS.
TL;DR: In this article, the thermoelectric properties of three terminal devices with Coulomb-coupled quantum dots (QDs) are considered, and the implications for the realisation of an all-thermal transistor are discussed.
TL;DR: In this article, a phase change material (PCM) base heat pipe heat sink was designed for high-power LEDs, which consists of a PCM base, adapter plate, heat pipe and finned radiator.
TL;DR: Yangbajing geothermal field is the first high-temperature hydrothermal convective geothermal system in China as mentioned in this paper, and the deep fractured granite reservoir is of great importance for capacity expanding and sustaining of the ground power plant.
TL;DR: In this article, a numerical thermo-hydraulic 3D model of the geothermal Upper Jurassic Aquifer (Malm) in the Munich region was developed based on a multidisciplinary reservoir characterization.
TL;DR: In this article, detailed exergy and energy analyses of shell and tube type latent heat thermal storage system (LHTES) for medium temperature solar thermal power plant (∼200 °C) are performed to estimate the net useful energy during the charging and discharging period in a cycle.
TL;DR: In this article, a pyroelectric-oscillating heat pipe (POHP) assembly of a low temperature generator continuously operates between a hot heat source and a cold heat sink.
Abstract: Low temperature thermal to electrical energy converters have the potential to provide a route for recovering waste energy. In this paper, we propose a new configuration of a thermal harvester that uses a naturally driven thermal oscillator free of mechanical motion and operates between a hot heat source and a cold heat sink. The system exploits a heat induced liquid-vapour transition of a working fluid as a primary driver for a pyroelectric generator. The two-phase instability of a fluid in a closed looped capillary channel of an oscillating heat pipe (OHP) creates pressure differences which lead to local high frequency temperature oscillations in the range of 0.1–5 K. Such temperature changes are suitable for pyroelectric thermal to electrical energy conversion, where the pyroelectric generator is attached to the adiabatic wall of the OHP, thereby absorbing thermal energy from the passing fluid. This new pyroelectric-oscillating heat pipe (POHP) assembly of a low temperature generator continuously operat...
TL;DR: In this article, the authors investigated the unconventional nature of entropy production in nonequilibrium systems with odd-parity variables that change signs under time reversal and found that the EP transferred to the environment is not equivalent to the usual reservoir entropy change due to heat transfer.
Abstract: We investigate the unconventional nature of entropy production (EP) in nonequilibrium systems with odd-parity variables that change signs under time reversal. We consider the Brownian motion of a particle in contact with a heat reservoir, where the particle’s momentum is an odd-parity variable. In the presence of an external momentum-dependent force, the EP transferred to the environment is found to be not equivalent to the usual reservoir entropy change due to heat transfer. An additional unconventional contribution to the EP, which is crucial for maintaining the non-negativity of the (average) total EP enforced by the second law of thermodynamics, appears. A few examples are considered to elucidate the novel nature of the EP. We also discuss detailed balance conditions with a momentum-dependent force.
TL;DR: In this paper, the authors describe how electromagnetically induced transparency may be used to construct a nontraditional near-ideal quantum heat engine as constrained by the second law, which produces a bright narrow emission at line center of an otherwise absorbing transition.
Abstract: We describe how electromagnetically induced transparency may be used to construct a nontraditional near-ideal quantum heat engine as constrained by the second law. The engine is pumped by a thermal reservoir that may be either hotter or colder than that of an exhaust reservoir, and also by a monochromatic laser. As output, it produces a bright narrow emission at line center of an otherwise absorbing transition.
TL;DR: In this article, a mini-tube capillary-network embedded and thermal-water activated building envelope is proposed to turn the passive component into active, therefore broadening the direct utilization of low-grade thermal energy in buildings.
TL;DR: In this paper, an evaluation of the subsurface ground temperature distribution during operation of a soil-borehole thermal energy storage (SBTES) system was performed. But, the results showed that only 2.43-4.86 GJ of thermal energy was stored attributable to heat losses.
Abstract: This study focuses on an evaluation of the subsurface ground temperature distribution during operation of a soil-borehole thermal energy storage (SBTES) system. The system consists of an array of five 9 m-deep geothermal heat exchangers, configured as a central heat exchanger surrounded by four other heat exchangers at a radial spacing of 2.5 m. In addition to monitoring the temperature of the fluid entering and exiting each heat exchanger, 5 thermistor strings were embedded in boreholes inside and outside of the array to monitor changes in ground temperature with depth. After 75 days of heat injection at a constant rate of 20 W/m, corresponding to 11.5 GJ of thermal energy, the average ground temperature in the array increased by 7°C. However, depending on the storage volume definition, only 2.43–4.86 GJ of thermal energy was stored attributable to heat losses. After a 4-month rest period the heat storage was observed to decrease by 60% owing to further heat losses. The trends in subsurface temp...
TL;DR: In this paper, a thermal synthesis modeling of a thermochemical heat storage based on the reactive porous bed of MgCl2⋅2H2O in a closed system is presented.
TL;DR: In this article, the problem of power optimization of a chemically driven heat engine based on first and second order reaction kinetic theory was studied, and the effects of the finite-time thermodynamic characteristics of the coupling relation between chemical reaction and heat engine on the power optimization were analyzed.
Abstract: The finite-time thermodynamic method based on probability analysis can more accurately describe various performance parameters of thermodynamic systems. Based on the relation between optimal efficiency and power output of a generalized Carnot heat engine with a finite high-temperature heat reservoir (heat source) and an infinite low-temperature heat reservoir (heat sink) and with the only irreversibility of heat transfer, this paper studies the problem of power optimization of chemically driven heat engine based on first and second order reaction kinetic theory, puts forward a model of the coupling heat engine which can be run periodically and obtains the effects of the finite-time thermodynamic characteristics of the coupling relation between chemical reaction and heat engine on the power optimization. The results show that the first order reaction kinetics model can use fuel more effectively, and can provide heat engine with higher temperature heat source to increase the power output of the heat engine. Moreover, the power fluctuation bounds of the chemically driven heat engine are obtained by using the probability analysis method. The results may provide some guidelines for the character analysis and power optimization of the chemically driven heat engines.
TL;DR: In this article, the working pair CaCl2/H2O has been identified as suitable reference system due to the possibility to store thermal energy and perform an upgrade of thermal energy at the same time.
TL;DR: In this paper, the authors consider a stream of independently prepared units repeatedly put into contact with the system and show that this stream constitutes an effective resource of nonequilibrium free energy and identify the conditions under which it behaves as a heat, work or information reservoir.
Abstract: We expand the standard thermodynamic framework of a system coupled to a thermal reservoir by considering a stream of independently prepared units repeatedly put into contact with the system. These units can be in any nonequilibrium state and interact with the system with an arbitrary strength and duration. We show that this stream constitutes an effective resource of nonequilibrium free energy and identify the conditions under which it behaves as a heat, work or information reservoir. We also show that this setup provides a natural framework to analyze information erasure ("Landauer's principle") and feedback controlled systems ("Maxwell's demon"). In the limit of a short system-unit interaction time, we further demonstrate that this setup can be used to provide a thermodynamically sound interpretation to many effective master equations. We discuss how non-autonomously driven systems, micromasers, lasing without inversion, and the electronic Maxwell demon, can be thermodynamically analyzed within our framework. While the present framework accounts for quantum features (e.g. squeezing, entanglement, coherence), we also show that quantum resources do not offer any advantage compared to classical ones in terms of the maximum extractable work.
TL;DR: In this paper, the authors performed a detailed study of the heat extraction process in enhanced or engineered geothermal system (EGS) with a previously developed numerical model, and found that the EGS performance, e.g., production temperature and lifetime, is tightly related to the flow pattern in the reservoir.
Abstract: With a previously developed numerical model, we perform a detailed study of the heat extraction process in enhanced or engineered geothermal system (EGS). This model takes the EGS subsurface heat reservoir as an equivalent porous medium while it considers local thermal non-equilibrium between the rock matrix and the fluid flowing in the fractured rock mass. The application of local thermal non-equilibrium model highlights the temperature-difference heat exchange process occurring in EGS reservoirs, enabling a better understanding of the involved heat extraction process. The simulation results unravel the mechanism of preferential flow or short-circuit flow forming in homogeneously fractured reservoirs of different permeability values. EGS performance, e.g. production temperature and lifetime, is found to be tightly related to the flow pattern in the reservoir. Thermal compensation from rocks surrounding the reservoir contributes little heat to the heat transmission fluid if the operation time of an EGS is shorter than 15 years. We find as well the local thermal equilibrium model generally overestimates EGS performance and for an EGS with better heat exchange conditions in the heat reservoir, the heat extraction process acts more like the local thermal equilibrium process.
TL;DR: In this article, the performance analysis and optimization of a thermally regenerative electrochemical refrigerator (TRER) was investigated based on finite time analysis, and the general expressions of some important parameters of TRER were derived.
TL;DR: A case study of a vertical borehole ground-coupled heat pump (GCHP) system operating in Urbino (Central Italy) is presented in this paper, which includes an assessment of its seasonal performance and impact on the sedimentary heat reservoir from October 2010 to October 2014.
TL;DR: In this article, a solution to the finite cylinder-source model for the ground heat exchangers at different buried depths that takes into account the heat capacity inside them and allows arbitrary heat rate changes is presented.