Low-potential Heat Research Articles

Thermodynamic analysis for definition of low-potential heat sources

This study presents a method for defining low-potential energy sources based on thermodynamic analysis. It defines low potential energy sources and presents the results of calculating temperature levels corresponding to the concept of a low potential energy source. A classification of energy sources by thermal level was carried out, including sources of cold, low-potential heat and cold at reduced temperatures, low-potential heat and cold at elevated temperatures, and high-temperature sources. The analysis demonstrates the correspondence between thermodynamic assessment and practical views of many researchers on low-potential energy sources. Conclusions about the influence of external factors on the temperature range for these sources are drawn. It is shown that factors affecting the range of low-potential temperatures include: the temperature potential of consumers, as a reference point for temperature, and the efficiency of local stations for converting heat into work or electricity. Narrowed assessment is presented based on optimal conditions for humans (22 °C), from −90 °C to 203 °C, and extended assessment based on limits of liquid water existence at atmospheric pressure and temperatures (0–100 °C) from −104 °C to 329 °C with an efficiency of heat conversion stations of 38 %.

Reduction of CO2 emissions by recycling low-potential heat from the Benfield CO2 removal process at a natural gas hydrogen production plant

AbstractThe EU policies related to CO2 emission strictly define the stages of carbon neutrality achieving. According to these regulations, all production installations that emit carbon dioxide will be charged additional emission fees from 2026 to fully in 2035. Analysis of the increasing emission fees shows that in some industries incurring such additional costs will result in a lack of profitability of the products. Industries directly related to the food sector, such as nitrogen fertiliser production, are strategic in the economies of all countries. Nitrogen fertilisers are produced from ammonia, which is synthesised on a large scale from hydrogen and nitrogen. Hydrogen is produced by natural gas reforming with water vapour resulting in syngas (mixture of H2, CO, CO2, H2O), which CO in the next step reacts with water vapour (water gas shift reaction) producing H2 and CO2. CO2 is separated from hydrogen using the Benfield method. The analysis of the Benfield process (one process of hydrogen production) shows a possible way to reduce CO2 emission by optimising heat balance. It was shown that in the proposed technology the heat recovery reaches 89%, while the level below 30% was reported for other available technologies. The proposed solution is based on recirculation and reuse of heat, which is lost in other technologies. The analysis is for a process balance in a medium-sized hydrogen production installation. The analysis considers also the correlations with other installations thermally linked to hydrogen production. The economic balance showed the great financial benefits of this solution. In the scenario discussed, the CO2 emission factor was reduced by 20%. Graphical Abstract

Фінансові перешкоди впровадженню теплових насосів в централізованому теплопостачанні

The use of powerful industrial heat pumps (HP) is a fairly effective means of rational and environmentally friendly use of energy resources both in individual households and in district heating (DH), as well as in production processes in various industries. Powerful HPs are used in Ukraine much less than in developed European countries. In fact, these are isolated cases. The post-war reconstruction of destroyed cities with their district heating systems gives Ukraine a unique chance to use modern energy-efficient technologies, including HP. As a result, efficiency will improve and DH competitiveness will increase due to the low cost of thermal energy for consumers. Almost all developed countries of the world have government financial support for the HP implementation. The purpose of this study is to determine the level and form of government financial support for projects to implement HP in DHs of Ukraine. Financial modeling of the implementation of heat pump plants shown that they are more expediently to be used in the mode of generating thermal energy than in the mode of regulating the electric load of power systems. It is shown that the projects of heat pump plants, which use the heat of flue gases as a source of low-potential heat (LPH), are the most economically attractive and practically do not require government financial support. Projects of heat pump plants, which use air, ventilation emissions, waste water, soil and groundwater, sea, rivers, and waste heat of technological processes as LPH, are not financially attractive without government financial support, and some of them are even unprofitable. The most appropriate comprehensive financial support is tax incentives and interest compensation on the loan. Sensitivity analysis showed that projects for the implementation of heat pump plants may be the most sensitive to the amount of generated thermal energy, the price of natural gas and electricity. Keywords: heat pumps, low-potential heat sources, district heating, financial obstacles, tax incentives, grants.

ПРОБЛЕМЫ УТИЛИЗАЦИИ ТЕПЛОТЫ УХОДЯЩИХ ГАЗОВ АВТОНОМНЫХ КОТЕЛЬНЫХ

The problem of fuel and energy resources is presented as one of the most important global problems. Energy saving in consumer heat supply systems is indicated as an important aspect of reducing the consumption of fuel and energy resources. There is a significant potential for energy saving in heat supply systems, which is conditioned by considerable heat losses with exhaust gases from boilers. A problems related to the utilization of low-potential heat of exhaust gases are identified. A review and analysis of ways to utilize the heat of the exhaust gases of boiler houses and directions of useful use of this heat are performed, their advantages and disadvantages are indicated. The direction of conducting research on methods of utilization of low-potential heat of exhaust gases and ways of using of this heat, allowing to create high-effective low-waste complexes and systems, is recommended.

Control of Carbon Dioxide Bivalent Heat Pump on Heating of Buildings

The scheme of a bivalent heat pump (BHP) is considered, using both the heat of the water from the return network and the heat of the outside air as low-potential heat sources (LPH). The aim of the work is to create a BHP circuit that provides functioning at the variable heat load temperature. The goal was achieved by solving the following problems: analysis of methods of synthesis of BHP circuits, analysis of circuit operation under random disturbances and development of the automatic control systems for BHP. The most significant result of the work is: a heat pump circuit that can operate at variable pressures of the evaporator and the gas cooler. The next significant result is, for bivalent heat pumps intended for operation in heat supply systems with qualitative and qualitative-quantitative laws of thermal control, the introduction into the heat pump circuit of a heat exchanger installed in the return water circuit of the secondary building and cooled by outside air, as well as two control valves installed in series between the gas cooler and the evaporator, the first valve installed along the refrigerant flow being controlled by a signal based on the pressure difference between the outlet of the gas cooler and the separation vessel between the evaporator and the gas cooler, and the second by pressure in front of the evaporator. The significance of the obtained results lies in the increase of the COP of the heat pump, due to the increase of heat transfer in the gas cooler circuit. The HHP circuit differs from the known ones in that it uses two control valves and the heat exchanger for additional cooling of the return water of the BHP heated building.

Measurement and modelling of vapor–liquid phase equilibrium of 1,1-difluoroethane (R152a) + 1,1,2,3,3,3-hexafluoro-1-propene (R1216) at temperatures ranging from 283.15 K to 313.15 K

Compared to pure refrigerants, mixed refrigerants can effectively fulfill the demands of high efficiency, safety, and environmental preservation. An efficient mixture can be created by combining environmentally safe and non-combustible refrigerants with low global warming potential (GWP) and high latent heat hydrofluorocarbons (HFCs) in precise ratios. For this investigation, an experimental apparatus was built to obtain vapor–liquid equilibrium (VLE) data for the R152a + R1216 mixture within temperatures of 283.15 to 313.15 K. To depict the VLE characteristics of the binary systems, the Peng-Robinson (PR) equation of state (EoS) was utilized with the van der Waals (vdW) mixing rule. And to compare, the Huron and Vidal first-order (HV) and the Wong-Sandler (WS) mixing rules were utilized alongside the PR EoS and the non-random two-liquid (NRTL) activity coefficient model to correlate the acquired data. The findings indicated that the models showed strong concurrence with the empirical data. The binary mixture displays a near-azeotropic phenomenon when the mole fraction of R152a is below 0.65. The azeotropic point is fall within the experimental temperature range when the R152a liquid-phase has a mole fraction between 0.3069 and 0.4104.

Повышение энергетической эффективности газопоршневой ТЭС за счет комплексного использования тепловых вторичных энергоресурсов

Recently, the advantages and prospects to use piston gas internal combustion engines for the combined generation of electrical and thermal energy have become increasingly obvious. The range of single capacities of gas piston units (GPU) ranges from 0,1 MW to tens of MW, which makes them more attractive when designing various power facilities. Most brands of gas piston units can operate in co-generation mode, that is, as a combined heat and power plant that simultaneously generates electrical and thermal energy. The purpose of this study is to substantiate the possibility of integrated use of heat of the cooling systems of the gas piston engine of a thermal power plant (TPP). The studies conducted are carried out using well-known methods of thermodynamic calculation of the internal combustion engine cycle, of determination of the components of its thermal balance and thermal calculation of the equipment for utilization of secondary thermal energy resources. The results of the analysis of the heat losses of the GPU drive engine have showed that the total losses during its operation are about 11544,5 kW. Average potential heat losses with flue gases are 45,87 %, and low-potential heat losses with water in cooling systems and oil in lubrication systems are 53,14 %. A schematic diagram is proposed for the integrated utilization of thermal renewable energy resources (RES) at a gas piston thermal power plant. The main difference between the proposed scheme and the existing technical solutions is the utilization of the heat of the low-temperature charge air cooling system after the second section of the compressor and the heat of the engine lubrication system. An analysis of the expenditure part of the energy balance of the drive engine in case of the integrated use of thermal RES in the GPU cycle, has showed that the implementation of energy-saving measures will make it possible to usefully use up to 93,05 % of the supplied energy in the generation of electrical and thermal power.

METAL, NONMETAL, ENERGY AND ENERGY CARRIER PRODUCTION BY PLASMA ARC ELECTROLYTIC CENTRIFUGAL CONVERSION

The new plasma arc electrolytic centrifugal conversion process is intended to reduce material consumption, time and energy costs when producing various products represented by metals, nonmetals and energy carriers. The task is accomplished through combining the metallurgical, chemical and energy production into an integral production facility. All polluting emissions associated today with the metallurgical, chemical and energy sectors serve as reagents for the new process and are used for manufacture of useful products sent to the market. Energy saving substance separation requires concentration of the maximum possible amount of various chemical elements in the melting area; they serve as catalysts reducing the reaction energy consumption. The energy production and consumption processes are closed loop with the generated reagents redistributed among the production areas and reversed for recycling what allows low potential heat retaining from losses to the environment. As of today, thermal and nuclear power stations as well as metallurgical and petrochemical plants discharge about two thirds of the produced heat energy to the environment. In the plasma arc electrolytic centrifugal conversion process the energy is diverted from one production process to another allowing several times higher hydrocarbon processing. Elimination of harmful emissions into the atmosphere requires energy released due to the system combining the energy production with the mining, metallurgical and chemical industries. The substance processing is induced by the energy produced when burning hydrogen derived from hydrocarbon materials in oxygen recovered from ore. All energy produced but not consumed for external energy demand, is transferred into methanol serving as hydrogen, and therefore energy, accumulator. Energy is transferred over large distances by methanol transportation over pipelines with the return to the processing area of carbon dioxide gas, required for plasma initiation.

Cogeneration Installations in Degassing Systems of Solid Municipal Waste Polygons

The possibility of using energy and resource-saving power plants of cogeneration type with steam injection into the flow part with deep utilization of high-potential and low-potential heat of the gas-steam mixture in systems for degassing municipal solid waste is investigated. The use of a combined technology of absorption and adsorption purification of landfill gas is proposed. The conclusion is made about the effectiveness of using landfill gas as an energy carrier in a combined contact-type bioenergetic installation with a heat recovery heat exchanger, which will save the national wealth of the country and at the same time solve the problems of modern megacities associated with reducing the negative impact of MSW landfills on the environment.

Range of application of heat pump systems on various natural refrigerants

GROUNDING: The utilization of heat pumps (variation of vapor compressing machines) for heat transfer between different temperature levels is a promising development trend, considering low cost of heat energy, environmental friendliness of working mediums, economically sufficient solutions and low cost maintenance. Heat pumps are used for heating in building structures where low potential heat sources are wastewater streams, groundwater streams, air, heat of the soil. It is also possible to use low potential heat of heat emissions from industrial plants, that can be cost effectively in terms of production resources usage.
 AIMS: Selection of the refrigerant and its composition in order to provide operational stability for heat pumps at temperature levels from 48 to 95 ̊C with minimum energy consumption for the most widespread thermodynamical cycles.
 MATERIALS AND METHODS: Standard thermodynamic cycles of heat pumps were simulated using Aspen HYSYS software. Further optimization and parameter selection were performed using MATLAB module Global Optimization Toolbox.
 RESULTS: In compliance with demanded design parameters the results of each working medium simulation were obtained. Energy efficient parameters of the common heat pumps thermodynamical cycles were determined.
 CONCLUSIONS: According to exergy analysis of the thermodynamical cycles it has been determined that mixed refrigerants, pentane and ammonia are the most suitable and energy efficient working fluids for heat pumps.

METHODICAL APPROACH TO ESTIMATING THE POTENTIAL OF THERMAL ENERGY PRODUCTION BY HEAT PUMP PLANTS IN CASE OF THEIR IMPLEMENTATION IN REGIONAL DISTRICT HEATING SYSTEMS

The results of the estimation of the annual potential for thermal energy production using heat pumps (HPs) in district heating systems (DHS) for the regions of Ukraine and the country as a whole are given. This study is relevant due to the high level of DHS development in Ukraine, which reaches 52 %. Today, the outdated equipment of DHSs in Ukraine needs significant technological modernization. Also, in the near future, it will be necessary to restore DHSs destroyed as a result of the total destruction of the civil infrastructure by the russian aggressor. The post-war reconstruction of Ukrainian cities has a unique chance to radically update DHSs using renewable energy sources and innovative technologies, including HPs. The authors propose a new methodical approach for the regional determination of the forecast implementation scope of HPs in DHSs. Using this approach, the economically available energy potential of thermal energy production by HPs in DHSs from various low-potential heat sources (LPHS) was determined, both for the regions of Ukraine and for the country as a whole. As of 2020, this energy potential for DHSs of Ukraine is 62.601 million Gcal/year (262.1 PJ/year): 22.2 % is provided by natural LPHS (heat of air (2.2 %), river water (16.9 %), ground and groundwater (3.1 %)) and 77.8 % is provided by anthropogenic LPHS (heat of ventilation emissions of buildings connected to the DHS (43.0%), sewage water (9.7 %), flue gases from boilers and combined heat power plants (14.3 %), cooling water of technological processes (10.8 %)). The calculated energy potentials for the thermal energy production by HPs from various LPHSs for DHSs of 24 regions of Ukraine are presented also. Information from scientific publications, regulatory documents, annual reports of the State Statistical Service of Ukraine and other government agencies used as the initial data for calculations. Approved methods of heat engineering calculations, methods of statistical and calculation-comparative analysis using Microsoft Excel computer software used to calculate and visualize the results. Methodical recommendations for determining the priority and locations for the implementation of HPs in regional DHSs of Ukraine, which developed by the authors of the article, are presented. Bibl. 48, Fig. 2, Tab. 4.

Mathematical modeling of the heat transfer process in a dense blown layer of granular material

The object of research: a mathematical model of unsteady heat transfer between particles forming a dense layer in a heat exchange channel and an air flow passing through the layer.
 Investigated problem: obtaining a mathematical model adequate to the physical phenomenon will significantly expand the field of research, reduce the time for determining the thermal characteristics of heat transfer and data processing.
 The main scientific results: an explicit analytical dependence is obtained that allows calculating the local temperature of the layer in an arbitrary cross-section of the channel at selected moments of time. The presented analytical dependence was verified by analyzing the calculated data on the material temperatures in the channel obtained by varying the main physical quantities: the effect of the heating duration, heat transfer coefficient, porosity, and density on the temperature distribution was studied. The temperatures along the length of the channel were calculated at different points in time with the following initial data: material - gravel: c=860, ρ=1500, λ=0.6, ε=0.4; aud=800. Based on the results of the calculations for the time τ=60 s, τ=900 s, τ=1800 s, τ=2400 s, τ=1800 s, the graphs shown in the paper are constructed. It is shown that the mathematical model adequately describes the process of heating a layer of granular material in a heat exchange channel and allows obtaining satisfactory data on the temperature distribution along the length at different points in time. The calculated data correlate satisfactorily with the experimental results.
 Innovative technological product is an analytical dependence obtained for the first time, which is necessary for inclusion in the calculation method of regenerative heat exchangers intended for the utilization of low-potential heat flows.
 The area of practical use of the research results is the heat engineering calculations of regenerative heat exchangers with a dense granular packing. The consumers of the developed regenerators are greenhouses and food industry. Such industries are characterized by a low-potential level of thermal emissions, the heat of which is difficult to utilize using existing heat exchange equipment.
 Scope of the innovative product: design bureaus focused on the design of innovative heat exchangers for the utilization of low-potential heat flows, and research laboratories studying the processes of heat exchange between a dense layer of granular material and a through gas (air) flow.

Research and Development of Trinary Power Cycles

The most effective and environmentally safe fossil fuel power production facilities are the combined cycle gas turbine (CCGT) ones. Electric efficiency of advanced facilities is up to 58% in Russia and up to 64% abroad. The further improvement of thermal efficiency by increase of the gas turbine inlet temperature (TIT) is limited by performance of heat resistance alloys that are used for the hot gas path components and the cooling system efficiency. An alternative method for the CCGT efficiency improvement is utilization of low potential heat of the heat recovery steam generator (HRSG) exhaust gas in an additional cycle operating on a low-boiling heat carrier. This paper describes a thermodynamic analysis of the transition from binary cycles to trinary ones by integration of the organic Rankine cycle (ORC). A mathematical model of a cooled gas turbine plant (GT) has been developed to carry out calculations of high-temperature energy complexes. Based on the results of mathematical modeling, recommendations were made for the choice of the structure and parameters of the steam turbine cycle, as well as the ORC, to ensure the achievement of the maximum thermal efficiency of trinary plants. It is shown that the transition from a single pressure CCGT to a trinary plant allows the electric power increase from 213.4 MW to 222.7 MW and the net efficiency increase of 2.14%. The trinary power facility has 0.45% higher efficiency than the dual pressure CCGT.

Experimental study of the temperature regime of the solar pond in the climatic conditions of the south of Uzbekistan

This article is devoted to the experimental study of the temperature regimes of the solar pond in the southern climatic conditions of Uzbekistan. The research was conducted in an experimental version of a solar pond that accumulates low-potential heat. According to research, when taking heat from a salt solar pond, without a coating on its upper surface and comparing the results of a glass-covered experiment is 10-15% higher than that of a glass-covered experiment, when the ambient temperature is 34 °C and solar radiation is 973 W/m2 it is scientifically based that the temperature of saline solar pond water with a concentration of 25-30% rises to a temperature of 53 °C in the lower part of the pond and that the energy storage efficiency of the lower convective zone of the solar pond increases in parallel with increasing solar radiation

Utilization of low-potential secondary energy resources at oil pumping station

The article considers the sources of low-potential heat at oil pumping station, estimates the amount of heat of technological processes that is irretrievably lost in the environment from the oil ACD, cooling systems of electric motors and wastewater treatment plants, and also presents possible ways of utilization and useful use of this heat using heat pumps.

New Low-Potential Heat Exchangers Design

New Low-Potential Heat Exchangers Design

Cevherlerden ve tuzlu su kaynaklarından lityum kazanımı

Lityum, farklı özellikleri (düşük elektrot potansiyeli ve spesifik ısı kapasitesi) nedeniyle pek çok endüstride (pil, seramik ve cam sanayi, gres yağı, polimer, metalürji, klima sistemleri) yaygın bir şekilde kullanılmakdadır. Son yıllarda, gelişen teknolojiye bağlı olarak yeni alanlarda da (elektrikli araçlar, enerji depolama) kullanımıyla birlikte lityuma olan talep artmıştır. Bu nedenle, lityum Avrupa Birliği Komisyonu tarafından kritik hammaddeler listesine alınmıştır. Lityum üretimi çoğunlukla tuzlu su kaynaklarından ve cevherlerden (spodümen, lepidolit, zinvaldit, ambligonit, pedalit gibi) yapılmaktadır. Bununla birlikte, son yıllarda lityum-iyon piller gibi ikincil kaynaklardan da üretimi gerçekleştirilmektedir. Spodümen gibi cevher ya da konsantrelerden lityum kazanımı yaygın olarak sülfürik asit/kavurma prosesiyle gerçekleştirilir. Bu çalışmada, lityumun kritik hammadde olarak önemi, Dünya ve ülkemizin lityum potansiyeli ve cevherlerden/tuzlu su kaynaklarından lityum üretimi için uygulanan prosesler detaylı olarak incelenmiştir. Literatürde cevherlerden ve tuzlu su kaynaklarından lityum kazanımı üzerine yapılmış farklı araştırmaların bulguları tartışılmıştır. Ayrıca, Dünya’da lityum kazanımının gerçekleştirildiği tesislerden akım şemaları sunulmuştur.

ОЦЕНКА ВОЗМОЖНОСТИ СОЛНЕЧНОГО ТЕПЛОСНАБЖЕНИЯ С ИСПОЛЬЗОВАНИЕМ ВОЗДУШНОГО ТЕПЛОВОГО НАСОСА

Solar energy is one of the sources of renewable energy. However, during the cold season in Russia, the use of solar energy is difficult due to low outdoor air temperatures. The purpose of this article is to analyze the possibility of energy saving when using solar energy for the heating system of an individual residential building in Vladivostok. The latitude of the city is 43 °, but the estimated temperature for the design of heating is -22 ° C. This greatly complicates the use of solar heat. The possibility of accumulation of low-potential heat in a specially equipped outhouse (greenhouse) for conversion by a thermal air-water pump is analyzed in order to use it for heating needs in the future. Two constructions are considered as the finishing material of the extension: a two-layer polycarbonate with an air layer and an energy-saving double-glazed window. The calculation shows that in the coldest month is January, the potential of solar thermal energy is 14 %–37 % of the required heat demand, depending on the material used in the construction of the extension. In March and April, excess heat is generated. It can be used for hot water supply needs. Thus, for an individual residential building, the use of solar heat accumulated in a greenhouse extension is relevant as an additional source of heat for the heating system.

Prospects of using heat pumps for the thermal treatment of concrete in the field

Introduction. In the cold Russian climate, thermal treatment of concrete is kind of a mandatory operation conducted to accelerate concrete curing as part of the manufacturing of reinforced concrete products and structures. In practical work, concreting at low temperatures in the field may be accompanied by a shortage and high cost of energy resources needed to perform such thermal treatment.
 
 Materials and methods. A promising economical solution to the problem of thermal treatment of concrete and reinforced concrete products in the field is the use of air heat pump systems. The refrigerant circuits through a compressor, a condenser — heat exchanger, a throttle valve, and an air evaporator. The core element of such a unit is the compressor, which is driven not by an electric motor, as usual, but an internal combustion engine. The heat, generated by the heat pump, is delivered to the reinforced concrete product, subjected to thermal treatment, due to the circulation of the coolant through a supplementary circuit that has a condenser-heat exchanger, flexible connecting hoses and thermoactive formwork, in which fresh concrete is placed.
 
 Results. The heat pump, which is the source of low-potential heat energy transfer, represents a separate integrated and universal unit, convenient for transportation and installation on the site. The second element of the unit is the thermoactive formwork, that represents the whole range of devices used to manufacture various reinforced concrete products. The installation of this unit will not take more than 5–10 minutes. An alternative to heat pump systems is an electric thermal treatment unit powered by a gasoline electrical generator.
 
 Conclusions. The procedure of manufacturing concrete and reinforced concrete products using thermal treatment by air heat pumps is technically feasible, and its energy efficiency may exceed that of an alternative process, namely, the use of gasoline (diesel) electrical generators.

Thermodynamic Optimization of Low-Temperature Cycles for the Power Industry

The fuel price increase and severe environmental regulations determine energy-saving importance. Useful utilization of low-potential heat sources with 300–400 °С temperature becomes topical. The application of low-temperature power production facilities operating low-boiling heat carriers could be a solution to this problem. A comparative parametric study of a number of heat carriers resulted in a choice of the most promising fluids that are not expensive, have low toxicity and flammability, low ozone depletion and low global warming potential. These heat carriers are considered for application in simple power production cycles with and without regeneration. The main parameters were optimized at the initial temperatures of 323.15–623.15 K. The cycle without regeneration has a maximal net efficiency of 29.34% using the water at an initial temperature of 623.15 K. The regenerative cycle at a temperature below 490 K has its maximal efficiency using a water heat carrier, and at a higher temperature above 490 K with R236ea. The cycle with R236ea at 623.15 K has an electrical net efficiency of 33.30%. Using a water heat carrier, the maximal efficiency can be reached at pressures below 5 MPa for both cycles. Among the organic heat carriers, the minimal optimal initial pressure of a simple cycle is reached with the R236ea heat carrier below 45 MPa without regeneration and below 15 MPa with regeneration. Therefore when utilizing the latent heat with temperatures above 500 K R134a, R236ea and R124 are the most promising organic fluids. Such conditions could be obtained using different industrial sources with water condensation at elevated pressures.