Temperature Of Heat Carrier Research Articles

Experimental study of kukersite oil shale pyrolysis by solid heat carrier

The investigation of oil shale pyrolysis in the experimental retorting system by solid heat carrier (silica sand) was conducted. Modeling of the heat and mass transfer processes in the retorting system was performed with use of simplified mathematical model. It was shown that the radiation heat exchange plays the main role in the heat transfer between oil shale particles and solid heat carrier under the conditions of volatiles release. The maximum yield of the shale oil amounts to 73% at temperature of experiment of 560°C, which exceeds the data obtained in the Fisher assay on 20%. The conditions that lead to increase in maximum yield of shale oil in the industrial UTT units with the rotary drum reactor were ascertained. They are mainly associated with a decrease in the solid heat carrier (ash) temperature, which leads to the inhibition of secondary reactions between ash and the acidic compounds of the shale oil.

Universal Entropy Efficiency of Thermal Processes

Objectives: The main task of the estimation of power processes of any technical system is to define the efficiency of the consumed energy usage. Method: The most often used efficiency criterion is the ratio of the useful energy to the consumed energy defined from the power flow balances and the environmental losses. This criterion is defined primarily on the basis of the energy conservation law (more often on the primary case, i.e., on the basis of the 1st law of thermodynamics) and is generally called the coefficient of efficiency (COE). Findings: The article presents the entropy coefficient of efficiency. The entropy efficiency of a building depends on the inside and outside temperatures and the heat carrier temperature in the heating system, but only to the extent to which the heat emission and the heat conductivity coefficients depend on these temperatures. Taking these values to be constant, one can determine that the building efficiency depends only on the thermo physical properties of the radiators, walls and heat carriers. The method can be applied to obtain a common criterion of efficiency of complex heating or/and cooling buildings. If thermal energy converts into work, then entropy efficiency is equal to ratio of real cycle efficiency to thermal efficiency of Carnot cycle both for power and heat pump cycles. Also this method works for endoreversible cycles. Improvements: Entropy efficiency EnEf is the universal parameter of thermodynamic efficiency including COE and COP. EnEf criterion can be applied even in the cases when COE and COP have no sense.

The Technology of Automatic Control of Heat Consumption in Buildings

The paper is devoted to development and research of buildings’ heat consumption management technology. Schematics of heat consumption management for CHP and low-grade as heat sources discussed. Analysis of management system capability during spring and autumn seasons conducted. The research was made withnumerical approach. Adequacy of implemented models and methods was proved. Engineering and operational recommendations were made for management of buildings’ heat consumption systems. Higher efficiency of buildings was proved while implementing developed technology regardless of heat sources. Management technology efficiency showed dependency on its schematics, heat-carrier temperature and temperature of low- grade heat source (for schematics with heat pump).

Simulation Study of Shenmu Coal Pyrolysis by Gas Heat Carrier Based on a Moving Bed

Coats–Redfern integral method combined with thermogravimetry-mass spectrometry technology was applied to study the evolution of the main pyrolysis products for Shenmu bituminous coal. And a heat transfer, reaction, numerical model of coal pyrolysis by gas heat carrier in a moving-bed reactor is developed. The model can predict the internal temperature profile and pyrolysis volatiles evolution of different coal species as well as the temperature distribution of gas heat carrier versus bed height. The results show that when the temperature of the gas heat carrier increases from 700 to 900 °C, the theoretical bed height of pyrolysis drops from 0.26 to 0.14 m, and the maximum of the devolatilization rate increases from 0.954%·s–1 to 1.382%·s–1. The coal species have significant influence on their temperature-rise pyrolysis process in a gas heat carrier moving-bed reactor. Higher initial temperature or velocity of gas heat carrier, smaller particle size, or moving velocity of coal tends to accelerate the devolatilization rate and shorten the pyrolysis time. This work may provide a theoretic foundation for the reactor amplification and different industrial condition prediction of high-volatile coal pyrolysis in a moving-bed reactor.

Natural and Artificial Methods for Regeneration of Heat Resources for Borehole Heat Exchangers to Enhance the Sustainability of Underground Thermal Storages: A Review

The concept of borehole heat exchanger (BHE) field exploitation is described, along with problems regarding the sustainability of heat resources in rock masses. A BHE field sometimes has problems with the stability of the heat carrier temperature during long-term exploitation. The main reason for this is an insufficient heat stream with which to transfer heat by conduction in rock. Possibilities for the regeneration of heat in rock masses, based on experiences at the Geoenergetics Laboratory (Drilling, Oil and Gas Faculty, AGH University of Science and Technology), are described.

Research On Solar Energy Collector With Cell Polycarbonate Absorber

A flat plate solar collector with cell polycarbonate absorber and transparent cover has been made and its experimental investigation carried out. The collector consists of a wooden box, into which, a layer of heat insulation with a mirror film and 4 mm thick cell polycarbonate sheet, as the absorber, are placed. The coherence between collector’s efficiency, heat carrier and ambient air temperature, as well as intensity of the solar radiation and heat power in the experimental investigation has been obtained. During the experimental examination the maximum temperature of the heat carrier reached 80˚C at the intensity of solar radiation about 0.8 kW/m2 and ambient air temperature around 32˚C. The efficiency of the collector reached 33-60%, depending on the intensity of solar radiation and surrounding air temperature.

Pyrolysis of oil shale by solid heat carrier in an innovative moving bed with internals

This article reports a new moving bed with particularly designed side and central channels as its internals for small-size oil shale pyrolysis by solid heat carrier. The bed is called moving bed with internals (MBI), and the solid heat carrier is shale ash from industrial Fushun retorting furnace. The pyrolysis was tested by varying the temperature of solid heat carrier, thickness of particle bed between the side and central channels, and ash-to-shale mass blending ratio in terms of the oil and gas product distribution and qualities. The shale oil yield is close to 90% of the Fischer Assay yield, and of the produced oil over 70wt.% is gasoline and diesel and its dust content is only about 0.1wt.%. The highest shale oil yield occurs at the pyrolysis temperature of 495°C. The shale oil yield decreases with increasing particle bed thickness due to the increased shale oil cracking over shale ash in the prolonged residence time of volatile products inside the particle bed. Mechanism analysis shows that the central channel in the MBI directs the pyrolysis products to flow from the annulus to center of the particle bed, and this makes the moving bed as a filtration layer that considerably reduces the dust content in the produced oil. Meanwhile, this lateral flow greatly shortens the time of secondary reactions occurring to the pyrolysis products so that MBI could be applied to small-size oil shale to produce shale oil with high yield and high quality.

Modeling the Heat Regime of Thermal Boreholes with Pore Moisture Freezing/Melting

Modern computer programs modeling heat transfer near the boreholes of geothermal or ground source heat pumps (GSHP) ignore freezing and melting of pore moisture. This is so because most GSHP are deployed in regions with moderate climate, where ground temperatures are generally positive. To ensure efficient exploitation of GSHP under Russia's climatic conditions, we have to allow the heat carrier temperature, i.e., the ground temperature, to drop below zero. During the heating season, pore moisture freezes and melts releasing and absorbing the latent heat, which may affect the heat regime in the neighborhood of the thermal borehole. To assess the effect of latent heat on the borehole heat regime, we need a sufficiently simple and "fast" algorithm that can be used in engineering calculations during GSHP design. In this article, we present a pore moisture freezing/melting algorithm developed by the Insolar group of companies. The algorithm utilizes the concept of equivalent or "effective" ground thermal conductivity. Results of computer experiments are reported, confirming the essential dependence of the GSHP efficiency on ground-moisture phase transitions.

Control of heat supply of building based on the use of individual heat point of original design

The literature states that the transition from central heat points to individual heat points with the installation of appropriate automation allows to achieve a heat energy saving of more than 20%, but reliable experimental data, substantiating this position are not found today. Therefore, long-term experimental studies of heat supply of administrative building based on the individual heat point of original design to determine the real heat energy saving in actual practice taking into account environmental factors were conducted. Based on the experimental data, graphical dependencies of consumption of the heat carrier, heat energy and heat carrier temperature on the ambient temperature for two operation modes of the individual heat point with the calculated heat energy saving were constructed. The effectiveness of introducing the individual heat point was also determined. As a result of experimental studies, it was found that the higher the ambient temperature, the more unreasonable heat energy consumption with centralized unregulated heat supply, especially at the beginning and end of the heating season. Therefore, introducing individual heat points is one way to increase energy efficiency during new construction and modernization of existing buildings, which enhances the heat supply quality and efficiency thus providing consumers with comfort. Long-term experimental studies of heat supply of administrative building based on the individual heat point have shown the possibility of heat energy saving of up to 15%. The experimental data are important for providing recommendations on mass introduction of individual heat points of different capacities for housing and communal services.

Effects of the Heat Carrier’s Temperature and Particle Size on the Pyrolysis of <i>Imperata </i><i>cylindrica </i>in a Transported Bed Reactor

The pyrolysis of Imperata Cylindrica in a transported bed reactor has been carried out using sand as heat carrier. This study is to determine the significant effect of the pyrolysis process condition for heat carrier temperature and particle size on the liquid yield and bio oil properties. Physical and chemical properties of bio-oil such as the water content, pH, viscosity and density were determined. The results showed that the heat carrier’s temperature highly affected the liquid product, yielding 2.30 to 11.89 wt.% in increasing the temperature from 450 to 600°C. The yield increased with larger particle size with 0.375 mm diameter gives maximum yield of 11.88 wt.% (600°C) but decreased gradually until 0.650 mm diameter afterwards.

Flash Pyrolysis of Coal with Solid Heat Carrier in a Fluidized Bed

Flash pyrolysis of Shenmu coal with solid heat carrier was carried out in a fluidized bed using semi-coke as the solid heat carrier and nitrogen as the carrier gas. The effects of pyrolysis temperature, reaction time and mass ratio of heat carrier to coal on the yields of products were studied. It is found that the best operating conditions involving pyrolysis temperature 550°C, reaction time 6 min and mass ratio of heat carrier to coal 2. The properties of coal tar from fluidized bed, such as density, viscosity, freezing point, carbon residue and hydrogen carbon atom ratio, are almost higher than that of the above water coal tar and lower than that of the below water coal tar, while the above and below water coal tar obtained from Sanjiang squared retort. The results of simulation distillation show that gasoline and diesel fractions of coal tar from fluidized bed are higher than that of below water coal tar and lower than that of above water coal tar, while the heavy oil fraction is opposed.

Exergy analysis of zeotropic mixtures as working fluids in Organic Rankine Cycles

The thermodynamic performance of non-superheated subcritical Organic Rankine Cycles (ORCs) with zeotropic mixtures as working fluids is examined based on a second law analysis. In a previous study, a mixture selection method based on a first law analysis was proposed. However, to assess the performance potential of zeotropic mixtures as working fluids the irreversibility distributions under different mixtures compositions are calculated. The zeotropic mixtures under study are: R245fa–pentane, R245fa–R365mfc, isopentane–isohexane, isopentane–cyclohexane, isopentane–isohexane, isobutane–isopentane and pentane–hexane. The second law efficiency, defined as the ratio of shaft power output and input heat carrier exergy, is used as optimization criterion. The results show that the evaporator accounts for the highest exergy loss. Still, the best performance is achieved when the condenser heat profiles are matched. An increase in second law efficiency in the range of 7.1% and 14.2% is obtained compared to pure working fluids. For a heat source of 150°C, the second law efficiency of the pure fluids is in the range of 26.7% and 29.1%. The second law efficiency in function of the heat carrier temperature between 120°C and 160°C shows an almost linear behavior for all investigated mixtures. Furthermore, between optimized ORCs with zeotropic mixtures as working fluid the difference in second law efficiency varies less than 3 percentage points.

Thermal Regime in a Building in the Presence of Mixing of Heat Carriers from Delivery and Return Pipelines

We consider the problem of establishing a temperature regime in rooms and a heating system on mixing heat carriers flowing in a delivery and return pipelines. We show that unlimited mixing of heat carriers leads to the leveling of temperatures on the stories of a building and to attainment of a limiting temperature in the building close to the heat carrier temperature in the delivery pipeline of the municipal network. It has been established that if the heat carrier flow rate in the heating system does not change in the process of mixing, the temperature in the heating system and the temperature in the rooms of a building can decrease to the outdoor air temperature.

The study of the heat-engineering characteristics of a solar heat collector based on aluminum heat pipes

This paper presents the results of studies into the heat-engineering characteristics of a flat heat solar collector based on aluminum heat pipes that is designed to be used in building facades. The principle of work and the structure of the solar collector are considered; the results of its comparison with a traditional flat solar collector are presented. The studies were performed at a heat carrier temperature range of +10–+30°C and at a solar heat flow density of 400–1000 W/m2. The obtained experimental heat-engineering characteristics of the collector based on heat pipes show that they are at a level of traditional flow solar collectors; for example, its efficiency is 0.65–0.73. Meanwhile, the hydraulic resistance of the structure with heat pipes is by a factor of 2–2.4 smaller and ensures a high level of scalability, reliability, and maintainability, which is important when using it as an element of facade constructions of solar heat systems.

Effects of process parameters on pore structure of semi-coke prepared by solid heat carrier with dry distillation

The semi-coke was prepared by solid heat carrier with dry distillation in single factor method. The pore structures of raw coal and semi-coke were characterized by Brunauer–Emmett–Teller (BET) and scanning electron microscope (SEM). The results show that the adsorption and desorption isotherm of semi-coke are not coincident. There was a wide pore distribution on the semi-coke, in which mesopores and micropores account for a considerable proportion. Also there are many more secondary pores. With the increase of the final temperature of heat carrier and constant temperature, as well as the decrease of volume ratio of coal and hot carrier reactor, specific surface area and pore volume of semi-coke increased rapidly first and then decreased and finally increased, along with the rapidly reduction of average pore size. SEM photos show that the surface of semi-coke becomes increasingly rough and glossy.

Heat transfer analysis of short helical borehole heat exchangers

In this paper a numerical model to analyze the thermal behaviour of vertical ground heat exchangers with a helical shaped pipe is presented. This type of configuration can be a suitable alternative to conventional ground heat exchangers, especially when the heating and cooling loads of the building are very low.The model describes the heat transfer problem by means of a network of interconnected thermal resistances and capacitances. Moreover, as the investigated ground heat exchanger is usually installed in shallow depth, the model takes into account the interaction between the ground and the ambient environment which affects the fluid heat carrier temperature into the heat exchanger and, as a consequence, the energy efficiency of the heat pump.After a sensitivity analysis on the mesh parameters, the presented model is compared with experimental data and the simulation results show good agreement with the measurements. Finally, analyses to investigate the influence of the weather conditions, of the axial heat transfer and of the pitch between the turns of the helical pipe for two types of ground are carried out.

The Characteristic Research of Shenmu Coal Pyrolysis by Solid Heat Carrier

A fixed-bed experimental apparatus with the capacity of 1kg coal was set up for coal pyrolysis by solid heat carrier. Shenmu bituminous coal and quartz sand was used as raw material and solid heat carrier respectively. The effects of initial temperature of solid heat carrier, reaction time and blending ratio on the yield of gas and tar were examined at different conditions. The results showed that tar yield was above 10 wt% when the initial temperature of solid heat carrier more than 800oC, reaction time and blend ratio had lesser influence on gas and tar yield. At the investigated test condition, smaller coal particle leads to an inconspicuous increase on gas and tar yield. The characteristic of gas and tar products was also investigated in this paper.

Investigation of Transient Process of Heat Carrier Temperature of Water to Air Heat Exchanger

Transient process of the outlet heat carrier temperature of water to air heat exchanger is investigated. This transient process, provoked by instantaneous change of inlet heat carrier temperature, is tripartite: the time delay, the initial jump of temperature and the temperature change from the initial jump to the steady state value. The mathematical expressions for calculation of the delay, the initial jump and the steady state temperature are presented. Mathematical model for investigation of the temperature change from the initial jump to the steady state is described. It was defined that this temperature change, at precise evaluation, is not the first order lag (exponential) process, but for many tasks of automatic control of heating devices can be considered as such. The block scheme of heat exchanger representation in ACS of heat carrier temperature is delivered. The empirical equation for calculation of exponential process time constant is proposed. Ill. 3, bibl. 11 (in English; abstracts in English and Lithuanian). DOI: http://dx.doi.org/10.5755/j01.eee.118.2.1183

Process optimization of an auger pyrolyzer with heat carrier using response surface methodology

A 1kg/h auger reactor utilizing mechanical mixing of steel shot heat carrier was used to pyrolyze red oak wood biomass. Response surface methodology was employed using a circumscribed central composite design of experiments to optimize the system. Factors investigated were: heat carrier inlet temperature and mass flow rate, rotational speed of screws in the reactor, and volumetric flow rate of sweep gas. Conditions for maximum bio-oil and minimum char yields were high flow rate of sweep gas (3.5standardL/min), high heat carrier temperature (∼600°C), high auger speeds (63RPM) and high heat carrier mass flow rates (18kg/h). Regression models for bio-oil and char yields are described including identification of a novel interaction effect between heat carrier mass flow rate and auger speed. Results suggest that auger reactors, which are rarely described in literature, are well suited for bio-oil production. The reactor achieved liquid yields greater than 73wt.%.

Modeling and Estimation of Temperature Transient Process of Heat Carrier in Heating System

Transient temperature process of the heat carrier flowing in a conduit is investigated at a certain selected distance from the heat carrier temperature unit jump point. An electro analogical model of heat carrier temperature is designed. The model is realized and analysed by electrical circuits simulator PSpice included in the software OrCAD. It was defined that the transient change of heat carrier temperature is not the first order lag process when assessing it precisely. Expressions achieved by theoretic calculations are presented to calculate heat carrier front temperature and steady fluid temperature. Expression summarizing modelling results according to which it is possible to estimate the time constant of transient process of heat carrier fluid temperature is presented too.