Entire Heating Period Research Articles

Monitoring the heating energy performance of a heat wheel in a direct expansion air handling unit

This study presents an on-site examination of the heating energy performance of a real ventilation system, running on the flat roof of a shopping complex building in Hungary. The main focus of this study is to delve into the heating energy efficiency of specific air handling elements, such as the air-to-air rotary heat wheel and the direct expansion heating coil supplied by a variable refrigerant volume outdoor unit under real operation conditions. Additionally, an investigation was carried out during the heating season to scrutinize the potential occurrence of CO2 transfer from the exhaust airflow to the supply airflow within the heat wheel, which issue highlights a notable limitation of the heat recovery system. Based on the monitored and measured data, the energy saving impact of the heat wheel was 20.5 % on the electric power consumption of the variable refrigerant volume outdoor unit throughout the entire heating period, compared to operation without heat wheel. Furthermore, the relative average of CO2 cross-contamination is recorded as 3.8 % in the investigated heating season.

Heat transfer within nonequilibrium dense aluminum heated by a heavy ion beam

Abstract Energetic laser-accelerated ions can heat a small solid-density sample homogeneously to temperatures over 10,000 K in less than a nanosecond. During this brief heating time, the electron temperature of the sample rises first, and then the ion temperature increases owing to the heat transfer between the hot electrons and cold ions. Since energy deposition from the incident heavy ion beam continues concurrently with the electron-ion relaxation process within the heated sample, the electron and ion temperatures do not reach equilibrium until the end of the heating. Here we calculate the temperature evolutions of electrons and ions within a dense aluminum sample heated by a laser-accelerated gold ions using the two-temperature model. For these calculations, we use the published stopping power data, known electron-ion coupling factors, and the SESAME equation-of-state (EOS) table for aluminum. For the first time, we investigate the electron and ion temperature distributions within the warm dense aluminum sample and the heating uniformity throughout the entire heating period. We anticipate that knowledge of the temperature evolution during heating will allow for the study of the stopping power, thermal conductivity, EOS, and opacity of warm dense matter heated by an energetic heavy ion beam.

Evaluation of Heated Window System to Enhance Indoor Thermal Comfort and Reduce Heating Demands Based on Simulation Analysis in South Korea

Heated glass can be applied to improve windows’ condensation resistance and indoor thermal comfort in buildings. Although this applied technology has advantages, there are still some concerns in practical applications, such as additional energy consumption and control issues. This study evaluates the effectiveness of a heated window heating (HWH) system in terms of thermal comfort and heating energy performance (HEP). The simulation-based analysis is performed to evaluate the effectiveness of the HWH using a residential building model and to compare it with radiant floor heating (RFH) and hybrid heating (HH) systems (i.e., combined HWH and RFH). This study also investigates the peak and cumulative heating loads using HWH systems with various scenarios of control methods and setpoint temperature. The predicted mean vote (PMV) is used as an indoor thermal comfort index. The ratio of cumulative thermal comfort time to the entire heating period is calculated. The results show that HWH and HH can reduce the heating load by up to 65.60% and 50.95%, respectively, compared to RFH. In addition, the times of thermal comfort can be increased by 12.55% and 6.98% with HWH and HH, respectively. However, considering the social practices of South Korea, HH is more suitable than HWH. Further investigations for HH show that a surface setpoint of 26 °C is proper, considering both heating demands and thermal comfort. In addition, the setpoint temperature should be determined considering HEP and the thermal comfort for HWH, and the optimal setpoint temperature was suggested under specific conditions.

The Human’s Comfort Mystery—Supporting Energy Transition with Light-Color Dimmable Room Lighting

The constant increase of intermittent renewable energies in the electricity grid complicates balancing supply and demand. Thus, research focuses on solutions in demand-side management using energy flexibility to resolve this problem. However, the interface between demand-side management and human behavior is often insufficiently addressed, although further potential could be leveraged here. This paper elaborates on the effect of light color on humans’ temperature and comfort perception in connection to energy flexibility. Researchers have found that people perceive blue light as colder and red light as warmer. To this end, we evaluate the effect of light color in a case study for a German industrial facility assuming sector-coupled electric heating. We simulate the entire heating period from October to April in an hourly granularity, using the well-established real options analysis and binomial trees as a decision support system to heuristically minimize energy expenditures by utilizing deferral options when energy prices are high. Our results show a 12.5% reduction in heating costs for sector-coupled electric heating, which extrapolated leads to CO2-eq emission savings of over 34,000 tons per year for the entire German industry, thereby supporting the energy transition.

ПОВЫШЕНИЕ ЭФФЕКТИВНОСТИ ФУНКЦИОНИРОВАНИЯ ПРОМЫШЛЕННОГО ПРЕДПРИЯТИЯ ЧЕРЕЗ ОЦЕНКУ ПОТЕРЬ ТЕПЛОВОЙ ЭНЕРГИИ

The article discusses ways to improve the efficiency of the functioning of industrial enterprises using the method of assessing thermal energy losses through building envelope, performed on the basis of instrumental examination, as well as using the method of determining heat loss for the entire heating period if it is impossible to carry out a calculation based on instrumental examination.

ENERGY EFFICIENCY OF COMBINED HEAT SUPPLY SYSTEMS

The consumption of energy resources in the world states is constantly growing from year to year. The production of fossil fuels is also increasing, but for various reasons it cannot fully cover the required amount from consumers. One of the most important consumption sectors is heat loads from heating, ventilation and hot water supply of industrial and residential buildings. To cover the thermal loads of heating and hot water supply, the necessary heat carrier is water heated to a certain temperature. The most promising from the point of view of heating water for hot water supply are solar collectors. Hot water for heating needs to be reheated practically throughout the entire heating period. The introduction of heat pumps is promising. When using solar collectors, the heating agent can be reheated in heat pumps.
 The aim of the study is to develop such a combined heat supply system that uses more renewable energy and as a peak source a fossil fuel boiler (electric energy), as well as a method for calculating this system to determine the optimal composition of equipment and rational modes of its operation.
 The methodology for calculating heat supply systems combining solar collectors, heat pumps and fossil fuel boilers is presented. The problem of load distribution between the main elements of the combined heat supply system should take into account the probabilistic component. This is due to the fact that with a changing real mode of operation, different thermal load of the equipment can be optimal. This is primarily influenced by the variable heat inputs from solar collectors during the day. According to the above method, it is possible to determine the optimal parameters of the heat supply system for different operating modes, at which the minimum consumption of fossil fuel will be ensured.

The Efficiency of Vapor Compression Transformation of Energy Flows for Heat Supply Based on the Sea Water

The results of the analytical study substantiated the operating conditions for the highly efficient use of the temperature potential of seawater in heat pump heating systems (HPHS) for buildings a building with correspondingly improved environmental indicators. Based on the analysis of the regional conditions of the Odessa water area of the Black Sea, the initial parameters have been substantiated and rational modes of operation of an improved HPHS with central, decentralized or local heating of the subscriber energy carrier have been determined. As indicators for evaluating the efficiency of the HPHS operation, the conversion factor of energy flows and the specific consumption of external energy for the drive of the compressor and the circulating pump of cooled water in the operation of heat pump units were considered. For seawater in the Odessa water area of the Black Sea during the entire heating period, the following temperatures were considered as initial data for analysis: water at the inlet to the evaporator (5–10) ° C, at the outlet (1 °C); calculated temperature difference of the coolant in the heating system (50–40) °C, indoor air (20 °C); estimated outdoor temperature (–18 °C). The characteristic correspondence between the flow rates of the cooled sea water and the heated energy carrier of the heat supply system was taken into account. The prerequisites of high efficiency of the heat pump heat supply system in which the actual conversion coefficient exceeds the seasonal normalized calculated and minimum value at an outdoor temperature of (–10) °C under the limiting conditions of the monoenergy regime for both new and reconstructed buildings were substantiated. In the course of the study, it has been determined that the total specific consumption of external energy for the compressor drive and the circulation of cooled water in the operation of a heat pump unit with a characteristic ratio of water equivalents, even under the limiting conditions of the monoenergetic mode of operation of the heat supply system at an outdoor temperature of (–10) °C, are within the range of generally accepted values (w = 0.28–0.34).

Оптимізація системи регулювання відпуску теплоти

Heat supply regulation should ensure high energy efficiency of district heating systems (DHS) in general, reducing the specific indicators of heat production and release and maintaining the normalized thermal regime of the premises with any changes in outdoor temperature, insolation, infiltration and heat. Usually the processes of central regulation of DHS at heat sources and heat consumers are considered separately: not only technically but also organizationally. In this regard, the proposal for joint consideration of central and local regulation of heat supply is relevant and useful. The proposed solutions can increase the efficiency of existing DHS at the stage of transition to modern options for their implementation, in which heat control units are located at the entrance to individual apartments, and thus, the degree of regulation of DHS as close as possible to autonomous heating systems. The purpose of the study is to comprehensively consider the impact of individual stages of heat supply on the overall efficiency of DHS. The most common in domestic DHS is a method of high-quality central control of heat supply by changing the temperature of the coolant in the pipelines of thermal networks at the outlet of heat sources. However, this method has a significant disadvantage - it is inefficient regulation during the period of cutting the temperature schedule with a joint load on heating and hot water. Working during this period leads to significant overheating in premises and unproductive heat loss. Unproductive heat losses because of inadequate regulation when lowering the heat release schedule reach up to 18% of the heat potential of the fuel used. The introduction of a combined quantitative and qualitative regulation is proposed, in which, up to the cutoff temperature of the temperature schedule, the heat release is controlled by changing the temperature of the coolant, and after the cutoff, the transition to quantitative central regulation is carried out. Practical recommendations for the implementation of such regulation have been developed. Combined central regulation ensures the possibility of providing hot water supply services throughout the entire heating period, avoids hydraulic and thermal deregulation of systems and ensures optimal conditions for the operation of heat generators, reduced energy consumption and a significant increase in the overall efficiency of the DHS. Key words: heat supply, centralized systems, energy saving, efficiency, heat load regulation

Performance investigation of a transcritical CO2 heat pump combined with the terminal of radiator and floor radiant coil for space heating in different climates, China

CO2 air-source heat pump is regarded as a promising technology for domestic hot water and automotive air-conditioning system. However, its coefficient of performance is not very satisfactory when it is used for space heating in winter, while this phenomenon is more obvious at the condition of taking conventional radiator as a heating terminal unit. To cope with this issue, a transcritical CO2 air-source heat pump system combined with the terminal of radiator and floor radiant coil for space heating was developed in this paper, for fulfilling the energy cascade utilization. The performance and feasibility of the studied system were investigated using Transient System Simulation Program and compared with a benchmark system in five locations with different climate zones, China. The results showed that, taken Shenyang as an example, the inlet water temperature of heat pump unit of the studied system and the benchmark system were 36 °C and 50 °C respectively. Also the average coefficient of performance and heating seasonal performance factor of CO2 air-source heat pump unit were 17%–28% and 9%–22% higher, respectively, compared with the benchmark system during the entire heating period. This study is helpful to improve the application of transcritical CO2 air-source heat pump for space heating in severe and cold zones in China.

A comprehensive study on a novel transcritical CO2 heat pump for simultaneous space heating and cooling – Concepts and initial performance

Carbon dioxide (CO2) is a natural substance and an environmentally benign, safe and economical refrigerant that can be used for cooling and heating systems. Unlike a traditional reversible heat pump system that only works either in heating or cooling, the air-to-air transcritical CO2 heat pump system reported in this paper is capable of providing simultaneous space heating and cooling through an Air Handling Unit (AHU) at any time. The system with cooling and heating capacities of 210 kW and 110 kW, respectively, was installed in a cinema complex in South Australia, and continuously operated from September to November in 2020. In this paper, the detailed configuration of the CO2 heat pump system with parallel compression is described. A complete system layout, comprising of cooling, heating and shared circuits, is revealed for the first time. A mathematical model based on highly efficient Bitzer compressors has also been developed in this study. The experimental data recorded in an entire heating period of approximately one hour has been utilised for model validation and analysis. Through the validation, the simulated power consumption for the compressors with Variable Speed Drive (VSD) and Fixed Speed Drive (FSD) has been compared to the experimental data with acceptable agreements. The simulated discharge temperatures agree with the actual temperatures measured within 10%. Moreover, the latest system performance from September to November has been evaluated based on the heating and cooling loads and combined COPs. It was found that the combined COP was relatively stable at around 3 regardless of climate conditions.

Energy saving in a urban farm with a heat pump

Despite the high urbanization in the world, at the level of 55% in Europe and the USA, there is still a culture of home gardening in cities, both for decorative purposes and for growing crops for consumption in the household. This tradition is favored by the prevalence of low-rise buildings, whose share in the USA is 92%, in Europe 80%, in Russia only 52%. Due to the lack of access to land, the inhabitants of Russia need new approaches to crop production, which will allow access to fresh vegetables at home, such methods can be aero and hydroponic plants that allow growing plants without soil, and these plants can be easily automated. Due to the specifics of the housing stock in Russian cities, a balcony or a loggia was determined as the best place for installing personal farms. The balcony or loggia are unheated rooms of the apartment, redevelopment with the balcony or loggia attached to the room or the transfer of heating devices is prohibited, therefore, to arrange optimal conditions for plants, along with warming, this room must be heated. Calculations showed that to maintain the required temperature on the insulated The balcony of an apartment building in Moscow will require 7488 MJ of thermal energy for the entire heating period. The cost of electricity costs per year, when using a heat pump, can be reduced by more than 35% compared to electric heating, and the energy consumption during conditioning is also taken into account in the total cost of heat supply using a heat pump, which allows you to create more favorable temperature conditions in summer.

Performance assessment of an air source heat pump water heater from exergy aspect

In this study, thermodynamic inefficiencies of the components and the whole system are quantified by exergy destruction. The performance of an air source heat pump water heater (ASHPWH) is examined experimentally under varying ambient conditions from the exergy destruction aspect. The exergy destruction is calculated for each moment through the entire heating period with regard to collected temperature and pressure data under various ambient conditions. The exergy destructions are examined continuously in a sequence from the beginning to the end of the water heating process. This approximation allows the designer and the manufacturer to see the progress of exergy destruction through the entire heating period to evaluate the performance of every component for avoiding irreversibilities and improving the ASHPWH. During these observations, three individual zones are observed in which the exergy destruction characteristics have changed. Furthermore, the impact of the ambient conditions on these zones is identified either. The thermodynamic properties and exergy destruction values are computed for all data collected by a MATLAB code. The results would be helpful to picture out the true evolution of the exergy destruction from component aspect either solely or combined effect of them during the water heating period.

ОБ ОДНОМ РЕШЕНИИ ЗАДАЧИ ВЫБОРА КОЛИЧЕСТВА И МОЩНОСТИ КОТЛОВ ПРИ ПРОЕКТИРОВАНИИ КОТЕЛЬНОЙ УСТАНОВКИ

Introduction. The problem of energy saving in the housing and communal services sector is the most urgent problem of the present time; its solution is possible, including through a rational choice of the technical composition of the boiler plant. Therefore, consideration of the boiler design issues is an important task. Objective. Consider the task of choosing the number and capacity of boilers for the designed heat supply source. Materials and methods. The methods for solving this problem, which are available in the literature, are analyzed. It is indicated that the task is very diffi-cult, primarily because of its multicriteria, and that in the literature on its solution there are recom-mendations mainly of a qualitative nature. Results. A new formalized calculation method is pro-posed, which includes three options for solving this problem. It is established that the number of boilers in the boiler room in all three calculation options does not at all depend on the calculated heat load, but is determined only by the calculated and permissible internal air temperatures, as well as by the calculated and average outdoor temperatures for the heating period. A larger number of boilers is obtained when calculating according to the first option, and a smaller number when calcu-lating according to the third option; therefore, the first option is preferable in the sense that when it is implemented, it is possible to have a nominal or close to nominal mode of operation of the boilers during the entire heating period. This is achieved by changing the number of boilers included in the operation. The second solution to the problem involves the installation of two types of boilers in the boiler room, and in the other two versions the boilers are of the same type. It is noteworthy that the rated power of the boilers calculated according to the first option is equal to the rated power of the boi-lers calculated according to the second option for operating conditions at an average outdoor tempera-ture of the heating period. The rated power of the additional boiler for the second option is equal to the rated power of the boilers for the third calculation option. Conclusion. The developed technique allows to streamline the procedure for selecting possible options for the technical composition of a boiler room, reduces the number of such possible options, what subsequently (during the economic analysis, as well as, in general, when designing) helps to reduce the amount of computational work. The tech-nique has been tested on a specific example and is recommended for use in solving design problems.

Effect of organic eutectic on nitrocellulose stability during artificial aging

ABSTRACTRecently, the eutectic composition of organic binary mixtures MENA+DPA has been found to be an efficient stabilizer of nitrocellulose. However, the behavior of such new stabilizer must be further investigated, especially after a long period of storage of the energetic composition. In this study, the stabilizing effect of the eutectic MENA+DPA on NC stability during artificial aging (at 338.65 K for 120 days), compared to its pure components, has been investigated by conventional stability tests and kinetic modeling. According to Bergmann & Junk (T = 405.15 K) results and over the entire period of aging, the eutectic MENA+DPA exhibits the best stabilizing effect on NC. The vacuum stability test (T = 353.15, 363.15, 373.15, and 383.15 K) results revealed that the amount of the evolved gas of NC containing this eutectic composition is very close to that of DPA, known as the conventional stabilizer. Furthermore, the kinetic modeling on VST data, obtained at four isothermal temperatures, was performed by two different methodologies, viz, fitting and free models to determine the kinetic triplets, which have been subsequently used to predict the storage lifetime for the studied systems. It was found that the NC stabilized by the eutectic MENA+DPA presents the highest value of the activation energy and has the longest storage lifetime during the entire heating period corroborating the stability tests results and affirming the excellent stabilizing effect of this mixture with respect to its pure component even if a long storage period is expected.

Study of microwave heating of reference liquids in a coaxial waveguide reactor using the experimental, semi-analytical and numerical means

In this work, a new application of coaxial waveguides for microwave heating of individual liquid substances and reaction mixtures is considered. The studied reactor is a small hollow coaxial waveguide in which liquids (methanol or ethanol) are exposed to microwaves generated by a miniature semiconductor source of 2.45-GHz frequency. The temperature of a liquid in the coaxial chamber is measured using an IR temperature sensor, thermocouple and optic fiber probes through non-radiating (in microwave range) openings in the thick copper reactor's wall, with the satisfactory accord between their readings at the medium-level power (10 W). The dynamics of microwave heating is studied using the semi-analytical and numerical simulations, which prove to be in good agreement with the experimental data. Two semi-analytical models of microwave heating in the coaxial waveguide as particular cases of the general electromagnetic-thermal problem are developed. One of them is the lumped system model in which uniformity of the temperature field is assumed. It gives good agreement with the measurements and is physically justified at late heating times. Another one is a simplified non-uniform heating model which is based on consideration of a convective turbulent boundary layer in a short horizontal coaxial waveguide. This model furnishes a quantitative explanation of the measured temperature difference at opposite ends of this waveguide over the entire heating period. The results of this study are interesting for development of miniature reactors for on-demand chemistry and pharmacy.

Study on performance evaluation of CO2 heat pump system integrated with thermal energy storage for space heating

Abstract CO2 heat pumps have drawn a great deal of attention owing to their advantages of high efficiency and environmental friendly for heating water under low ambient temperature. However, the system performance is not desirable and shows a lower COP for space heating, especially for a radiator as heating terminal, due to the higher inlet water temperature at the gas cooler, which causes a large throttle loss when the refrigerant flow through the throttling device. To tackle this issue, a transcritical CO2 heat pump system integrated with thermal energy storage (TES) systems was developed in this paper. The heating performance of the proposed system was investigated using TRNSYS 17.0 based on a typical single family rural house located in Beijing, China. The results showed that the heating capacity and energy consumption decreased by 21 and 24%, respectively, and the heating seasonal performance factor (HSPF) of the proposed system increased by 4% in comparison with the baseline system (without TES) during the entire heating period. It has been proved that the proposed system showed a better performance for space heating with a radiator terminal at low ambient temperature.

Heat-recovery technology of exhaust gases with high moisture content for gas-fired boilers of municipal heat-energy

To improve the operational and environmental performance of steam and water-heating gas-fired boilers, is proposed the efficient technology based on a complex heat-recovery system with heating and humidifying the blown air and heating the cold water of the chemical water-purification system. In terms of the implementation of this technology, the heat-recovery system uses the utilized heat simultaneously for different needs of the boiler plant, this allows the condensation mode of operation of the heat-recovery equipment during the entire heating period. The aim of the work is to study the thermophysical aspects of the creation and operating efficiency of the proposed complex heat-recovery system, provided that the exhaust-gases of the boilers are of high moisture content. Researches of the heat and humidity characteristics of exhaust-gases hath carried out and the increase of the coefficient the use heat of fuel of boiler with the use of this complex heat-recovery system with heating and humidifying the blown air and heating (or without it) of cold water of the chemical water-purification system for various types of boilers (steam and water-heating) and the corresponding modes of their operation. The made comparative analysis of these systems, namely, the comparison data of such characteristics of heat-recovery systems as: their heat capacity Q, the increase of coefficient the use heat of fuel of boiler Δη caused by their use, the heating and humidifying parameters of the blown air and exhaust-gases after the heat-recovery installation. It is shown that for the proposed heat-recovery system in comparison with the corresponding system without the heating of cold water of chemical water-purification system, increases by 1.3 ÷ 1.6 times the general heating capacity of the system and up to 6.6 % rises coefficient the use heat of fuel of boiler. Also, the humidity content of the exhaust-gases is much reduced after the heat-recovery system, and consequently lowered the heat loss with the exhaust-gases.

Investigation on the feasibility and performance of transcritical CO2 heat pump integrated with thermal energy storage for space heating

CO2 heat pumps have drawn a great deal of attention as an economic form of heating under low ambient temperature conditions. However, the system performance is not desirable and shows a lower COP due to the higher inlet water temperature at the gas cooler, which causes a higher refrigerant temperature at the exit of the gas cooler, leading to a large throttle loss when the refrigerant flow through the throttling device. To tackle this issue, a transcritical CO2 heat pump unit integrated with two thermal energy storage (TES) containing phase change materials (PCMs) is proposed in this paper. The objective of this work is to model and simulate the proposed system using TRNSYS based on a typical single family rural house in Beijing (typical cold climate conditions), China. The results showed that the heating capacity and energy consumption decreased by 21 and 24%, respectively, and the heating seasonal performance factor (HSPF) of the proposed system increased by 4% in comparison with the baseline system during the entire heating period. The simulation results demonstrated that TES is helpful to improve CO2 heat pump system performance and monthly energy saving ratio for space heating.

Experimental investigation and seasonal performance assessment of a frost-free ASHP system with radiant floor heating

Air source heat pumps (ASHPs) have been increasingly used to promote energy savings and reduce environmental pollution. However, the evaporator frosting is one of the largest problems in ASHP systems during the heating operation. To examine this issue, a novel frost-free ASHP system has been developed. Nonetheless, the system performance and energy consumption are significantly dependent on the climate conditions. This research aims to identify the characteristics of the novel frost-free ASHP system with radiant floor heating in three different climate zones, China. TRNSYS 17.0 software was employed to investigate the seasonal performance of the new system based on the typical envelope thermal characteristic parameters in the entire heating period in three cities, i.e. Beijing (cold A zone), Xi'an (cold B zone), and Chengdu (hot summer and cold winter zone), located in different climate zones, China. The results showed that the heating seasonal performance factors (HSPFs) of the studied system were 3.9%, 1.9% and 9% higher than the conventional system in Xi'an, Beijing and Chengdu, respectively. It was concluded that the system could operate effectively and reduce substantial energy consumption in comparison with the conventional ASHP system for space heating in cold climate zones.

Energy efficiency of the accumulation wall with a transparent insulation

This paper presents a numerical model of an accumulating solar wall with transparent insulation (ASW-TI). The objective of the simulation was to evaluate the energy efficiency of ASW-TI for different climatic conditions in Poland, i.e. for high, medium, and low irradiation. For each climate, the calculations were made for the entire heating period. As a result, temperature distributions in a wall at different times of the process and the energy balance of the wall in particular months and during the entire heating period were obtained.