Efficient Heat Generation Research Articles

Improved efficiency of heat generation in nonlinear dynamics of magnetic nanoparticles.

The deterministic Landau-Lifshitz-Gilbert equation has been used to investigate the nonlinear dynamics of magnetization and the specific loss power in magnetic nanoparticles with uniaxial anisotropy driven by a rotating magnetic field. We propose a new type of applied field, which is "simultaneously rotating and alternating," i.e., the direction of the rotating external field changes periodically. We show that a more efficient heat generation by magnetic nanoparticles is possible with this new type of applied field and we suggest its possible experimental realization in cancer therapy which requires the enhancement of loss energies.

Performance Analysis of a Hybrid District Heating System: a Case Study of a Small Town in Croatia

Hybridisation of district heating systems can contribute to more efficient heat generation through cogeneration power plants or through an increase in the share of renewable energy sources in total energy consumption while reducing negative aspects of particular energy source utilisation. In this work, the performance of a hybrid district energy system for a small town in Croatia has been analysed. A mathematical model for process analysis and optimisation algorithm for optimal system configuration have been developed and described. The main goal of the system optimisation is to reduce heat production costs. Several energy sources for heat production have been considered in 8 different simulation cases. Simulation results show that the heat production costs could be reduced with introduction of different energy systems into an existing district heating system. Renewable energy based district heating systems could contribute to heat production costs decrease in district heating systems up to 30% in comparison with highly efficient heat production technologies based on conventional fuels.

Potential of residential buildings as thermal energy storage in district heating systems – Results from a pilot test

Heat demand in a district heating system can have a significant variation within 1day, which produces problematic conditions for efficient heat generation. Short-term thermal energy storage can decrease this daily variation and make the conditions for generating heat more favorable. By periodically overheating and underheating buildings, causing small variations in indoor temperature, building thermal inertia can be utilized for thermal energy storage. This study presents the results from a pilot test where the potential to function as thermal energy storage was tested for five multifamily residential buildings in Gothenburg, Sweden. The signals from the outdoor temperature sensors were adjusted in different cycles during a total of 52weeks. The delivered heat and indoor temperature were measured during the test. The results indicate that heavy buildings, with a structural core of concrete, can tolerate relatively large variations in heat deliveries while still maintaining a good indoor climate. The study also demonstrated that a fixed time constant is not accurate enough to describe the variations in indoor temperature caused by the utilization of the buildings as short-term thermal energy storage. Degree hours is instead proposed as a simple yet adequate measurement for the thermal energy storage capacity in buildings. Storing 0.1kWh/m2floor area of heat will very rarely cause variations in indoor temperature larger than ±0.5°C in a heavy building.

Transcriptomic analysis of brown adipose tissue across the physiological extremes of natural hibernation.

We used RNAseq to generate a comprehensive transcriptome of Brown Adipose Tissue (BAT) over the course of a year in the naturally hibernating thirteen-lined ground squirrel, Ictidomys tridecemlineatus. During hibernation ground squirrels do not feed and use fat stored in White Adipose Tissue (WAT) as their primary source of fuel. Stored lipid is consumed at high rates by BAT to generate heat at specific points during the hibernation season. The highest rate of BAT activity occurs during periodic arousals from hypothermic torpor bouts, referred to as Interbout Arousals (IBAs). IBAs are characterized by whole body re-warming (from 5 to 37 °C) in 2-3 hours, and provide a unique opportunity to determine the genes responsible for the highly efficient lipid oxidation and heat generation that drives the arousal process. Illumina HighSeq sequencing identified 14,573 distinct BAT mRNAs and quantified their levels at four points: active ground squirrels in April and October, and hibernating animals during both torpor and IBA. Based on significant changes in mRNA levels across the four collection points, 2,083 genes were shown to be differentially expressed. In addition to providing detail on the expression of nuclear genes encoding mitochondrial proteins, and genes involved in beta-adrenergic and lipolytic pathways, we identified differentially expressed genes encoding various transcription factors and other regulatory proteins which may play critical roles in high efficiency fat catabolism, non-shivering thermogenesis, and transitions into and out of the torpid state.

Progress Towards an Optimization Methodology for Combustion-Driven Portable Thermoelectric Power Generation Systems

There is enormous military and commercial interest in developing quiet, lightweight, and compact thermoelectric (TE) power generation systems. This paper investigates design integration and analysis of an advanced TE power generation system implementing JP-8 fueled combustion and thermal recuperation. In the design and development of this portable TE power system using a JP-8 combustor as a high-temperature heat source, optimal process flows depend on efficient heat generation, transfer, and recovery within the system. The combustor performance and TE subsystem performance were coupled directly through combustor exhaust temperatures, fuel and air mass flow rates, heat exchanger performance, subsequent hot-side temperatures, and cold-side cooling techniques and temperatures. Systematic investigation and design optimization of this TE power system relied on accurate thermodynamic modeling of complex, high-temperature combustion processes concomitantly with detailed TE converter thermal/mechanical modeling. To this end, this paper reports integration of system-level process flow simulations using CHEMCAD™ commercial software with in-house TE converter and module optimization, and heat exchanger analyses using COMSOL™ software. High-performance, high-temperature TE materials and segmented TE element designs are incorporated in coupled design analyses to achieve predicted TE subsystem-level conversion efficiencies exceeding 10%. These TE advances are integrated with a high-performance microtechnology combustion reactor based on recent advances at Pacific Northwest National Laboratory (PNNL). Predictions from this coupled simulation approach lead directly to system efficiency–power maps defining potentially available optimal system operating conditions and regimes. Further, it is shown that, for a given fuel flow rate, there exists a combination of recuperative effectiveness and hot-side heat exchanger effectiveness that provides a higher specific power output from the TE modules. This coupled simulation approach enables pathways for integrated use of high-performance combustor components, high-performance TE devices, and microtechnologies to produce a compact, lightweight, combustion-driven TE power system prototype that operates on common fuels.

Save production: A bottom-up energy model for Dutch industry and agriculture

A new version of the model Save production simulates the development of energy use in the Dutch industry and agriculture, including combined heat and power generation. The model disaggregates national energy consumption into fuel types, industrial sectors, energy functions and energy technologies. Simulation is based on microeconomic investment behavior. Examples of model application show results on the penetration of combined heat and power in relation to policy instruments such as CO 2 prices, electricity price support and investment subsidies. Policies that discriminate on CO 2 emissions result in a slightly more efficient heat and power generation. Tailored to the Dutch situation, Save production is well equipped to generate outlooks for the Dutch industrial and agricultural energy use, and for analyzing the role of policies in detail. Its main strength lies in the middle term simulation of decision-making on energy saving technologies and analysis of policy effects. Specific precautions are required when the model is used for analysis on the longer-term, for simulating extreme policies or for the analysis of extremely fluctuating energy prices.

04/01369 Combined molten carbonate fuel cell and gas turbine systems for efficient power and heat generation using biomass: Jurado, F. and Valverde, M. Electric Power Systems Research, 2003, 65, (3), 223–232

04/01369 Combined molten carbonate fuel cell and gas turbine systems for efficient power and heat generation using biomass: Jurado, F. and Valverde, M. Electric Power Systems Research, 2003, 65, (3), 223–232

Combined molten carbonate fuel cell and gas turbine systems for efficient power and heat generation using biomass

When used in combination with turbines, fuel cells can produce from 55 to 90% of the electricity of the system while turbines produce the remainder. Fuel flexibility enables the use of low-cost indigenous fuels, renewables, and waste materials. The characteristics of gas from biomass gasification may vary significantly. Most real systems cannot be modeled exactly. Errors arise from unmodeled or unknown parameters. From another point of view, robust control incorporates the varying or uncertain parameters of the model. The advantage of this uncertainty representation is that it provides a good representation of the uncertainty arising in many real control problems.

00/03591 Combined solid oxide fuel cell and gas turbine systems for efficient power and heat generation

00/03591 Combined solid oxide fuel cell and gas turbine systems for efficient power and heat generation

Combined solid oxide fuel cell and gas turbine systems for efficient power and heat generation

The Department of Heat and Power Engineering at Lund University in Sweden has been conducting theoretical studies of combined SOFC and gas turbine (SOFC/GT) cycles. The overall goal is an unbiased evaluation of performance prospects and operational behaviour of such systems. The project is part of a Swedish national program on high-temperature fuel cells. Results of continuous studies started earlier by authors are presented. Recent developments in modelling techniques has resulted in a more accurate fuel cell model giving an advantage over previous system studies based on simplified SOFC models. The fuel cell model has been improved by detailed representation of resistive cell losses, reaction kinetics for the reforming reaction and heat conduction through the solid part of the cell. This SOFC model has further been confirmed against the literature and integrated into simulation software, Aspen Plus™. Recent calculations have focused on a system with external pre-reforming and anode gas recirculation for the internal supply of steam. A reference system, sized at 500 kW, has also been analyzed in variants with gas turbine reheat and air compression intercooling. In addition, knowledge of stack and system behaviour has been gained from sensitivity studies. It is shown that the pressure ratio has a large impact on performance and that electrical efficiencies of more than 65% are possible at low pressure ratios.

P-5-644 - Treatment of tumors of the anterior skull base: Report of 80 cases

Whole body hyperthermia treatment using magnetic nanoparticles as thermal seeds is a promising cancer therapy that enables selective heating of hidden microtumors that are scattered in different internal body parts and undetectable using current medical technology and tools. In this chapter, conventional magnetic physics models for the mechanism of heat generation in magnetic nanoparticles are described. Then, the operational limits of magnetic field and frequency conditions that influence the heat generation capacity besides the saturation magnetization of thermal seeds are discussed from the viewpoint of biomedical safety. Subsequently, heat dissipation mechanisms for efficient heat generation under strict safety restrictions are overviewed based on current understanding of physics of nanomagnetism. This chapter also covers the effects of magnetic interactions between magnetic nanoparticles and their potential therein. Finally, this chapter ends with summarizing future prospects from the standpoint of treatment technique and design of efficient thermal seeds.