External Heat Supply Research Articles

Dynamic simulation of an original Joule cycle liquid pistons hot air Ericsson engine

An Ericsson engine is an external heat supply engine working according to a Joule thermodynamic cycle. It is based on reciprocating piston-cylinder machines. Such engines are especially interesting for low power solar energy conversion, micro-CHP from conventional fossil fuels or from biomass and waste heat recovery. An innovative configuration has been designed where the mechanical pistons are replaced by liquid pistons. The engine is composed of two U-shape tubes partially filled with water, one for the compression spaces and one another for the expansion spaces. A thermodynamic model of the engine is developed. The model takes into account the dynamics of the liquid columns. It is shown that the engine indicated efficiency decreases when the rotation speed increases. The sign of the instantaneous torque on the flywheel changes four times per cycle, calling for a heavy flywheel. When the rotation speed increases above the natural frequency of oscillation of the liquid columns, the influence of the liquid pistons inertia is growing. Its impact is globally opposite to the one of the pressure in the cylinders. So, the effect of the inertia of the liquid columns is to reduce the amplitude of the torque variations.

직접 및 간접열교환에 따른 연속식 반응기 내 바이오매스 저속열분해 특성에 대한 실험적 연구

Biochar from pyrolysis is emerging as a new option for biomass utilization for various purposes including soil amelioration and carbon sequestration. This study investigated the slow pyrolysis characteristics of wood pellet in a continuous reactor varying the heat transfer type (direct and indirect contact) at various temperatures (400~700℃) with different carrier gas compositions (inert, O₂ 2%, and O₂ 4%). Direct contact heat transfer by preheated carrier gas accelerated the heat up of biomass, promoting the pyrolysis process as well as the temperature increase of indirect contact cases. The presence of O₂ in the carrier gas resulted in limited oxidation reactions with pyrolytic vapor, increasing the reactor temperature to 529.4℃ and 591.7℃ at 2% and 4% O₂, respectively, compared to the inert case having a final temperature of 492.4℃. This can be exploited to save the external heat supply but a careful temperature control is required to yield uniform biochar properties. The pyrolysis products from different test conditions were characterized for mass yield and detailed properties of biochar, bio-oil, and non-condensable gases.

Experimental parametric study of membrane distillation unit using solar energy

Solar distillation is a promising method for the supply of freshwater to rural communities because water is a vital factor for the survival of humans. Therefore potable water demand is increasing continuously because of the industrial, population and, fast agricultural applications. Nowadays, different techniques for water purification have been created to provide freshwater from salty and polluted water such as solar distillation method to distill brackish/saline water. This work presents an experimental study of the solar membrane distillation unit which is coupled with direct contact membrane (DCMD) which located at Kairouan University. The system is installed as part of a cooperation project research and development between Tunisian Electromechanical Systems Laboratory and German Institute for Solar Energy Systems entitled: Solar driven membrane distillation for resource efficient desalination in remote areas. For the heating of the hot feed water stream, a heat exchanger is included which can be operated with any external heat supply between 60 and 80 °C. For the cooling of the cold feed water stream, no heat exchanger is included. The cooling can be provided over the intake of cold feed water. The effect of solar irradiation and all temperature on the journal productivity of the unit has been presented.

ОПРЕДЕЛЕНИЕ РАЦИОНАЛЬНОГО СПОСОБА ПОДОГРЕВА СМЕСЕВЫХ МИНЕРАЛЬНО-РАСТИТЕЛЬНЫХ ТОПЛИВ ДЛЯ АВТОТРАКТОРНЫХ ДИЗЕЛЕЙ

Research objective is to provide the set temperature condition of mixed mineral and vegetable fuel (MMVF). The use of fuel systems with smart heating will increase the volume of mineral diesel fuel, replaced by renewable re-sources. The technique and results of research of heating with external and internal supply of heat and also with hashing of the heated environment are given. Researches were conducted on specially developed laboratory in-stallation. MMVF on the basis of flax, soy and rape oils were investigated. Concentration of a vegetable component made 40% on volume. The 1000 W external heater and also the 1000, 500 and 300 W external heaters of all types were used. It is established that when heating MMVF the external source of warmth provides good heating on all volume without use of extra for mixing, overheating is 50% of necessary size. When leading warmth without hash-ing of MMVF warming up came from an internal source (the 1000 W heater) unevenly, the unevenness was 60%. When using mechanical mixing of MMVF with heating from an internal source of warmth the unevenness of warm-ing up was 3.1…4.65% depending on heater power. By results of a research it was established that when using the heater with a power of 
 300 W when heating 1 liter of mixed mineral and vegetable fuel on the basis of rape oil with the maintenance of a vegetable component of 40% on volume time of heating to 60±2 °C was 230 s, the unevenness of heating was 3.1%, overheating was 3.1%. Recommendations about the most rational modes of heating of MMVF in a power supply system of the diesel are made.

Study on optimal distribution of heating load based on the first law of thermodynamics

The principle of external heat supply for cogeneration units is to meet the maximum heat load demand of the heating network, and the heat load of the heating network will vary significantly with the climate and solar light intensity. The heat supply system of extraction steam unit with high back pressure heating unit is taken as the research object to study the influence of heat load peak and valley change on the economy of cogeneration units. The energy consumption and operation economy of the cogeneration unit are analyzed by the heat consumption theory and the standard coal consumption of generating and heating income standard. The results show that the heat consumption of cogeneration units is reduced by 411.62 kJ(kW·h)−1 during the peak heat load in the extreme cold period than the low heat load in the end of the heat supply. The standard coal consumption per yuan income of the generation and heating is increased by 15 g.RMB−1. The daily gross income of generating and heating is reduced by about 47196 RMB per day for 12 hours of heat load. The cogeneration unit should use the return network temperature of the heat network as the basis for the change of the peak and valley of the heat network load when adjusting the external heating parameters and the operation mode of the unit.

The Thermodynamic Calculation of Offset Shafts Rotary Engine Ideal Cycle with External Heat Supply

The Thermodynamic Calculation of Offset Shafts Rotary Engine Ideal Cycle with External Heat Supply

Analysis of the Stirling engine in the Schmidt approximation

Exploration, oil and gas well development, and oil and gas production facilities are often located in remote, remote locations away from electrical networks and highways. Autonomous power supply of these facilities is currently carried out by means of diesel power plants, which is associated with the necessary supply of fuel and associated high overhead costs. In this regard, the use of renewable energy sources (RES) is of particular relevance. As such, wind energy, geothermal heat, solar radiation energy, associated petroleum gas energy are known. The same group should include local energy sources such as peat, wood, coal, coal shale, etc.with the exception of the first of these sources, the rest require the conversion of thermal energy into mechanical energy, and then, by means of an electric generator into electrical energy. The only known universal Converter is the Stirling generator-a machine in which the generator is combined with the Stirling engine. Stirling engine (DS) – refers to external combustion engines, more precisely external heat supply. For the operation of the DS, it is only required to bring the temperature difference to its heat exchangers, and both the increased temperature of the heater and the reduced temperature of the refrigerator are important. As a heater, you can use the heat of the burner, steam or water heated in geothermal or solar collectors. It is possible to supply directly solar energy from solar concentrators. For these cases, a special design of the DS with a quartz head is provided, through which concentrated solar radiation enters directly into the expansion chamber. Geothermal water supplied directly from the well or associated petroleum gas, which can be highly corrosive, can also be used for these engines. As a refrigerator, you can use the environment, chilled water, ice or snow. DS works in a closed cycle, which allows you to completely seal the body and use helium or hydrogen as a working fluid. This ensures high working fluid pressure, which increases the specific power (power per unit volume or weight of the engine). Currently, these engines have not received mass application, which is explained by both economic reasons (high cost of development, competition from the ice) and commercial (patent restrictions, trade secrets).

Deep regeneration of activated carbon catalyst and autothermal analysis for chemical looping methane thermo-catalytic decomposition process

The application of a chemical looping process to methane thermo-catalytic decomposition using activated carbon (AC) as a catalyst has been recognized as a promising technology for continuous high-purity H2 production in a carbon constrained world. However, it usually needs an external heat supply for the endothermic decomposition reactions. By taking advantage of the chemical looping combustion (CLC) technology, this study proposed a deep regeneration approach using H2O and O2 as regeneration agents to overcome the issues with maintaining catalytic activity and producing the heat needed for the endothermic reactions of H2 production from methane. TG-DTA and bench scale fluidized bed experimental results indicate that a deep regeneration degree of 30% or above could completely reactivate the spent AC catalyst and simultaneously generate sufficient heat than required in the methane decomposition reaction. Characterization study implies that the deep regenerated AC catalyst could maintain its physical properties within a certain number of cycles. Based on the experimental results, the chemical looping methane thermo-catalytic decomposition process was further optimized and assessed by Aspen Plus® thermodynamic simulation. The results indicate that heat and mass balances could be attained, and the circulation of the AC catalyst with a temperature difference of 262 °C between the decomposer and the regenerator enabling the process to run autothermally.

End flare of linear flow split profiles

One approach to design load optimized structures is the use of bifurcations. Linear flow splitting is a continuous sheet-bulk metal forming process, whereby bifurcated profiles are manufactured without joining or external heat supply. By roll forming linear flow split profiles, a wide spectrum of profile geometries can be realized, e.g. multi-chamber-profiles. Those profiles often require high dimensional accuracy to ensure their functionality. During roll forming, process related residual stresses are induced, which are released when the profiles are cut to length. Thereby increased deformation at the profile ends occurs, also known as end flare. End flare of bifurcated profiles has not been investigated so far. The aim of this research is to investigate end flare after roll forming of linear flow split profiles. Therefore, end flare after roll forming of a conventional sheet metal and a linear flow split profile is compared. The effect of residual stresses induced by linear flow splitting as well as the effect of additional geometrical stiffness due to the bifurcations on the development of end flare are examined. It is found that the residual stresses induced by linear flow splitting have no significant effect on end flare. However, the geometrical bifurcation affects the roll forming process, leading to higher residual stresses in the flange, which significantly affect the magnitude and the direction of end flare.

Heat transfer in a one-dimensional harmonic crystal in a viscous environment subjected to an external heat supply

We consider unsteady heat transfer in a one-dimensional harmonic crystal surrounded by a viscous environment and subjected to an external heat supply. The basic equations for the crystal particles are stated in the form of a system of stochastic differential equations. We perform a continualization procedure and derive an infinite set of linear partial differential equations for covariance variables. An exact analytic solution describing unsteady ballistic heat transfer in the crystal is obtained. It is shown that the stationary spatial profile of the kinetic temperature caused by a point source of heat supply of constant intensity is described by the Macdonald function of zero order. A comparison with the results obtained in the framework of the classical heat equation is presented. We expect that the results obtained in the paper can be verified by experiments with laser excitation of low-dimensional nanostructures.

Многотопливная микротепловая электростанция мощностью 1–10 кВт для удаленных объектов сельской местности и фермерских хозяйств

The problem of efficient electricity supply to rural consumers has not yet been fully resolved. A way to solve this problem is to develop a micro thermal power plant that can function on virtually any fuel. Using own energy source will reduce the cost of its production for the farm, significantly increase the reliability of electricity supply, and ensure its uninterrupted supply to consumers. The suggested power plant is driven by a thermal motor with external heat supply. The results of computer simulation of an engine with external heat supply, which works based on Stirling principle, are given. The design features of the engine being developed are considered.

Performance Evaluation of Absorber Reactors for Solar Fuel Production

Waste to energy conversion through thermochemical processing offers a potential option for valorisation of waste biomass, however, it requires external heat supply to process the waste. Solar energy is a promising solution to convert the waste and produce alternative fuels that can replace coal, oil and natural gas for heat and electricity generation. To realize this, the radiation from the sun should be converted to thermal energy. Among the solar concentrators, parabolic dish gives the highest concentration ratio per area in converting the solar energy to heat and electricity. The absorber is the main part of the dish which is placed at the focal point and converts the radiation to thermal energy. In this work, experiments were conducted on stainless steel, copper, ceramic and glass reactors as absorber materials of parabolic dish with aperture diameter 1.8 m coated with aluminium pet as reflective material. The objective of this research was to evaluate solar radiation-absorbing performance of the reactors and design efficient reactor for solar fuel production. Two sets of experiments were conducted. First, each of the reactors was placed at the focal point then the heating rate and maximum temperatures inside the reactors were recorded as a function of radiation intensity using K-type thermocouples. Secondly, each reactor was coated using carbon soot and then the experiment was repeated. Results showed that the coated glass reactor has the best performance in all the absorbers. Of the uncoated reactors, the stainless steel gave best results with stable and uniform temperature distribution inside the reactor. The results can be used as benchmarks for future design and application of the solar thermal technology.

ANALYSIS METHOD OF CALCULATION PARAMETERS OF HEAT AND MASS TRANSFER PROCESSES IN THE STIRLING ENGINE

The article highlights the optimal calculation methods for determining the parameters of heat and mass transfer processes occurring in the rotary-vane engine with an external supply of heat. It is shown that the mathematical model of working processes must consist of two parts. One part describes the processes occurring in the isolated volume. The second part describes the processes of mass exchange between the working chambers of two modules, as well as a heater or a cooler.

Specific interface area and self-stirring in a two-liquid system experiencing intense interfacial boiling below the bulk boiling temperatures of both components

We present an approach to theoretical assessment of the mean specific interface area $(\delta{S}/\delta{V})$ for a well-stirred system of two immiscible liquids experiencing interfacial boiling. The assessment is based on the balance of transformations of mechanical energy and the laws of the momentum and heat transfer in the turbulent boundary layer. The theory yields relations between the specific interface area and the characteristics of the system state. In particular, this allows us to derive the equations of self-cooling dynamics of the system in the absence of external heat supply. The results provide possibility for constructing a self-contained mathematical description of the process of interfacial boiling. In this study, we assume the volume fractions of two components to be similar as well as the values of their kinematic viscosity and molecular heat diffusivity.

Qualification of Aqueous Part Cleaning Machines for the Use of Waste Heat in Industrial Production Companies

This work presents an overview of solutions how part cleaning machines can be enabled to implement an external heat supply. The proposed solutions have to meet special requirements due to contaminated cleaning media during the heat exchange process. Standard components are used during the development and implementation to reach broad operational capability in different industries and industrial companies. Comprehensive measurements and studies of a single chamber cleaning machine with external heat supply through heat recovery of machine tools reveal an energy saving potential of more than 35%.

Oxidative pyrolysis of oil shale in tubular flow reactors with external heating

This article discusses the possibilities of the multipurpose use of oil shale based on the methods of their thermal processing. The main current concepts of oxidative pyrolysis processes are considered. A facility for the oxidative pyrolysis of powdered oil shale in tubular reactors of the gas-suspension type with external heat supply to the reaction zone is described.

Effects of active and passive warming of the foot sole on vibration perception thresholds

ObjectiveSkin temperatures are known to increase cutaneous sensitivity. However, it is unclear whether the amount of improved sensitivity differs depending on the protocol of heat application. Therefore, this study aimed to investigate the effects of active (treadmill walking) and passive (infrared radiator) warming of the foot sole on vibration perception thresholds. MethodsSixty healthy and injury-free subjects voluntarily participated in this study. Vibration perception thresholds (200Hz) and plantar temperatures were measured at the hallux and 1st metatarsal head. In experiment 1, warming and mechanically stimulating the skin was achieved by walking on a treadmill for 30min. In a follow-up study (experiment 2), external plantar heat was administered via an infrared radiator (30min). ResultsIn both experiments, increasing temperatures led to increased plantar sensitivity. However, the amount of improved sensitivity was greater in experiment 1, although plantar temperature increases were lower compared to experiment 2. ConclusionsWarming in conjunction with mechanical stimulation seems to have a greater potential to enhance plantar sensitivity compared to external heat supply only. SignificanceThe possible influence of mechanical stimulation and warming towards superior plantar afferent feedback highlights its importance regarding human posture and fall prevention.

Renewable hydrogen production by solar-powered methanol reforming

The present study demonstrates the possibility of generating hydrogen by methanol steam reforming at temperatures of 235–260 °C inside a non-concentrating solar collector, ideally for stationary fuel cell systems. In contrast to the current state-of-the-art, the solar collector provides all heat required for heating and evaporation of the reactants, endothermic reaction, and compensation of heat losses, without any external heat supply (such as from combustion of fuel or electric heating) and without the need for concentration of sunlight (as in conventional parabolic trough systems). Without the need for solar concentration, the system is simpler and more compact than conventional systems, and it can utilize all direct and indirect incident sunlight. The solar collector-reactor achieves hydrogen generation up to 6.62 LSTP min−1 per m2 collector area (equivalent to 1088 W m−2 LHV) under 1 sun, with solar-to-hydrogen efficiencies up to 78% and total energetic efficiencies (considering solar and fuel input) up to 43%.

Optimization of the engine heat exchanger header with an external supply of heat

The paper makes hydraulic calculation of heat exchanger inlet manifold of engine with an external supply of heat.The estimation of uneven fluid flow through heat exchanger elements was made.

Partial oxidation of sewage sludge briquettes in a updraft fixed bed

The fixed bed reaction of sewage sludge briquettes was investigated to evaluate the potential applications to gasification, combustion, or production of biochar as soil ameliorator. The reaction had two distinctive stages: ignition propagation and char oxidation. The ignition front of the sludge briquettes propagated at a lower speed, which significantly increased the stoichiometric ratio of overall combustion reaction and peak temperatures. The ignition front also had irregular shapes due to the channeling effects. During the char oxidation stage, the sludge ash agglomerated because of the slow reaction rate and increased CO2 formation. Because of low energy content in the product gas, the large briquettes were not favorable for syngas production. In addition, the low burning rates and ash agglomeration could cause problems in the operation of a grate-type furnace for combustion. However, the char accumulated above the ignition front had similar properties with that from pyrolysis under inert atmosphere. Therefore, the fixed bed reaction under partial oxidation conditions can be applied to produce biochar as soil ameliorator from the sludge briquettes without external heat supply.