Heating Mode Research Articles

An energy consumption rectification method based on Bayesian linear regression and heating degree‐days

AbstractThe time‐varying external environment is one of the main variables influencing heating energy consumptions, so that its influence should be rectified when energy savings of different heating modes are calculated. This paper proposes an energy consumption rectification method based on Bayesian linear regression and heating degree‐days, to obtain heating energy consumptions without the influence of different outdoor temperatures. The proposed method consists of three main steps. First, a physical model of heating houses is used to prove a relationship between energy consumptions and heating degree‐days. Second, Bayesian linear regression is exploited to estimate uncertainty ranges of heating energy consumptions. Finally, heating energy consumptions are rectified, and energy savings with their uncertainty ranges for different heating modes under the same outdoor temperature are obtained. The proposed method does not require the physical parameters of heating houses to facilitate practical implementation. Additionally, it provides uncertainty ranges of heating energy consumptions to measure the estimation accuracy. Numerical and experimental examples show that the proposed method provides more accurate estimates of heating energy consumptions than existing methods.

Study on the influence of temperature rise inhibitor on the early-age temperature field of moderate heat Portland cement (MHC) concrete

The employment of moderate heat Portland cement (MHC) and temperature rise inhibitor (TRI) are two important methods to reduce the early temperature rise of mass concrete in engineering. This study evaluated the impact of TRI on the temperature control effect and temperature field of MHC concrete at early-age. The thermal parameters of cement mortar, the adiabatic temperature rise and the hydration product of MHC concrete with varying TRI contents (0 %, 0.4 %, 0.8 %, 1.2 %) were tested. Results showed that both thermal conductivity and specific heat capacity of cement mortar inversely correlate with age, with higher TRI content enhancing specific heat capacity and reducing thermal conductivity; TRI can effectively reduce the adiabatic temperature rise of MHC concrete within 7 days, most significant at 24 h. Using the Krstulovic-Dabic model to analyze MHC's hydration process, and the results showed that the addition of TRI reduces the reaction rate in three stages (Crystallization Nucleation and Crystal Growth (NG), Phase Boundary Reaction (I) and Diffusion Reaction (D)), hinders the nucleation process, and shortens I stage. The microscopic temperature field simulation showed that TRI can reduce the early temperature gradient of MHC concrete under different aggregate characteristics, and its temperature control effect is more significant in MHC concrete with lower coarse aggregate content and smaller aggregate particle size. In addition, this paper analyzed the uniformity of temperature field in MHC concrete with TRI under different aggregate characteristics, and found that the early-age temperature field of MHC concrete has a smaller variance after adding TRI, indicating it becomes more uniform.

Non-invasive mass flow and local heat transfer coefficient measurements in pulsating heat pipes

A single loop Pulsating Heating Pipe (PHP) experimental setup was developed for non-invasive measurement of the local heat transfer coefficient and the mass flow along the PHP evaporator. These measurements are valuable to validate modeling tools used in the design of PHP. A two-step differential heat input method was used for measurement of mass flow and the results were compared with the optical and theoretical results. The conditions tested in the PHP were 50, 60 and 70% filling ratio, R134a as working fluid, internal diameter of 2 mm, saturation temperature of between 30 to 40 °C, inclination angles from 30 to 90° (vertical bottom heat mode) and heat loads on the evaporator from 10 up to 68 W. The results indicate a high performance in heat transfer of the PHP, with minimum internal thermal resistance values close to 0.008 K/W as well as local heat transfer coefficients greater than 10 kW/m2K for observed values of mass velocities between 60 and 140 kg/m2s. The results were compared with correlations from the literature and these were able to predict the results with a 20% average error margin, suggesting many similarities with convective boiling mechanisms.

Appropriate flame-spraying treatment exacerbates thermal oxidative degradation of residual polyethylene films

In dryland farming, plastic film mulching can significantly increase crop yields, but the resulting residues impair soil health. Heretofore, only few studies had examined how heat treatment facilitates the rapid degradation of polyethylene (PE) residual films. Herein, we characterized the variations in micro-morphology, functional groups, and crystallinity of PE residual films after moderate heat exposure using a self-made flame-spraying equipment. The results revealed that solid residues (SR) obtained from flame-spraying showed a gravimetric weight loss of 9.39 %–15.35 % compared with untreated PE residual films (UPF). Scanning electron microscope equipped with energy dispersive X-ray spectroscopy revealed considerable pits, cracks, and visible roughness in appearance and an increase in the oxygen-to‐carbon (O/C) atomic ratio. Fourier-transform infrared spectroscopy identified characteristic oxygen-containing functional groups and double bonds. X-ray diffraction showed that flame-spraying treatments did not alter the crystal form of polymer, but increased the crystallinity. Higher flame-spraying temperatures resulted in larger oxygen-containing bond indices and lower crystallinity, suggesting a more severe decomposition of PE residual film. The possible volatile gaseous products at different reaction temperatures were predicted using thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TG-FTIR). Degradation of the PE residual film started at 220 °C, and concentrated release of major products such as long-chain aliphatic hydrocarbons, ketones, and CO2, occurred in the temperature range of 340 °C–440 °C. These results highlighted the effectiveness of the moderate flame-spraying method in accelerating rapid decomposition of residual films, and a flame-spraying temperature range of 220 °C–340 °C should be recommended to avoid potential environmental risks induced by the release of large quantities of degradation products. This study will contribute to enhance our understanding of the thermal oxidative degradation behavior of PE waste and provide a scientific basis for the rapid and clean establishment of PE residual films mitigation in agricultural fields.

Winter thermal study in coastal rural dwellings: focus on elderly comfort in Chinese cold coastal regions

ABSTRACT With the continuous progress of China’s rural revitalization and the increasing aging population in coastal rural areas, it has become a research focus to make the indoor thermal environment more suitable for the elderly, especially in winter. This study took Qingdao’s coastal rural areas in the cold region of China as an example. A field survey was conducted in 110 coastal rural dwellings, and four typical dwellings were selected for on-site measurements. This study collected information on the characteristics of local residential buildings, the primary living spaces for the elderly, heating methods, and thermal satisfaction. It also documented the energy expenditure and thermal conditions of the surveyed dwellings. The research findings indicate that the current heating system, while capable of partially improving the indoor thermal environment, is still affected by poor thermal insulation performance. As a result, there are issues such as low average indoor temperature, significant temperature fluctuations, and overall thermal instability. The findings of this study provide comprehensive information on the heating modes used in coastal rural dwellings, and the results can be utilized to evaluate and further improve the thermal environment of dwellings in cold coastal rural areas.

Thermal Interaction and Cooling of Electronic Device with Chiplet 2.5D Integration

With the development of artificial intelligence (AI) and high-performance computing (HPC), the microelectronic industry is challenged with increased device integration density. Chiplet architecture can break through a variety of limitations on the system-on-chip (SoC) to create a high-computility system. However, chiplet heterogeneous integration suffers from high heat flux and serious thermal interaction problems. The factors affecting thermal interaction are not clear. In this paper, a collective parameter model and a distribution parameter model are developed to clarify the optimization method to mitigate thermal interaction. The trends predicted by the parameter model are consistent with the finite element method (FEM) simulation results. Furthermore, to cool the chiplets, a thermal test vehicle is designed and fabricated, and the cooling performance of the test vehicle with different flow rates, different TIMs (Thermal Interfacial Materials) (DOW5888 vs. liquid metal), and different heat modes is experimentally investigated. Compared with DOW5888, the utilization of liquid metal TIM can mitigate thermal interaction by 56% and 76% at flow rates of 0.2 L/min and 0.8 L/min, respectively. Consequently, at a temperature rise of 60 °C and a flow rate of 0.8 L/min, using liquid metal TIM can achieve heat fluxes of 330 W/cm2 and 520 W/cm2 for two chiplets, respectively.

Climate change induced heat and drought stress hamper climate change mitigation in German cereal production

ContextAgricultural production and climate change strongly influence each other and there are significant efforts to minimize negative impacts in both directions. In particular, breeding progress has succeeded in reducing the carbon footprint (CFP) of cereals over time. However, there is widespread certainty that climate change-related weather extremes have led to stagnation of cereal yields in many global production regions. Research questionWe assume that climate change-related yield stagnation is also evident in variety trials in Germany, which has to date only been shown for on-farm yields. Furthermore, we expect that the stagnation in yields also leads to a stagnation in the downward trend of CFP, and that heat and drought stress in particular increase the CFP of cereals. In addition, we hypothesize that the site-specific soil quality largely determines stress induced increases in CFP. MethodsWe conduct a partial life cycle assessment (LCA) with German variety trial data from 1993 to 2021 and determine the greenhouse gas emissions per unit of land (GHGL), as well as the CFP of winter wheat, winter rye, and winter barley. Further, we evaluate the time trends of yield, GHGL, and CFP using linear and quadratic plateau models. In addition, we calculate spatio-dynamic weather indices (WIs) for moderate, severe and extreme heat and drought stress. Using mixed models, we estimate the explanatory power and effect size of heat and drought WIs on the CFP. Finally, we present the spatial differences of heat and drought on the CFP at different soil qualities. ResultsWe show yield plateaus in all crops and stagnating GHGL trends, resulting in a stagnation of the downward trend of CFP, especially for rye and barley. We highlight that heat and drought increase the CFP of all crops. However, the impact of heat and drought on the CFP varies greatly with soil quality across all crops. ConclusionsWe conclude that climate change-induced weather extremes are major challenges not only for cereal production and food security but also for climate change mitigation in the agricultural sector, highlighting the importance of high-yield locations, alongside variety selection and resource-efficient management, for climate change mitigation. SignificanceThis study is the first that proves significant yield stagnation in German variety trials. Moreover, this study is the first to analyze the impact of heat and drought stress on cereal CFP, with novel results that proof that climate adaptation will become a crucial aspect of climate change mitigation in field crops.

Towards various occupants with different thermal comfort requirements: A deep reinforcement learning approach combined with a dynamic PMV model for HVAC control in buildings

Reinforcement learning (RL) has great potential in achieving energy-efficient, comfortable and intelligent control of heating, ventilation and air conditioning (HVAC) systems. Although research on RL-based HVAC control has attracted increasing interest, current studies generally use simple building simulation as the environment to train agents, and the definition of thermal comfort is limited to a wide temperature range, which cannot meet the different thermal comfort requirements of various occupants. This study proposes a deep reinforcement learning (DRL) control framework based on the Dueling Deep Q-network (DQN) algorithm, combined with a self-designed environmental model and reward function, for HVAC control meeting different thermal comfort requirements. Specifically, based on the theory of building thermal dynamics, a nonlinear equation modified by experimental data is used for the environmental model that reflects the actual thermal change of building. Different thermal comfort requirements are considered and analysed through a dynamic predicted mean vote (PMV) model that focuses on the metabolic rate and clothing level of occupants. By systematically exploring different heating modes for occupants and control time intervals, the proposed framework demonstrates that heating energy consumption can be reduced by 4.8%-39.58% under various conditions compared to rule-based control. In addition, the study found that the HVAC control based on DRL has greater potential in saving energy when the heating demand of building is higher. Our study is helpful for researchers to make HVAC control more energy-efficient and user-friendly with the help of artificial intelligence.

Učinak naprednih izolacijskih materijala i strategija pasivne optimizacije na toplinsku udobnost u tradicionalnim kućama tijekom zime

This study proposed an interior thermal comfort test to enhance the interior thermal comfort of traditional houses in the Guan Zhong region of the Shaanxi Province during winter. The study was conducted in Xiaoliu village by employing field tests and a questionnaire survey. The field tests and analysis revealed that the thermal comfort of traditional houses in this region is poor, the spatial layout of the houses is unsuitable for conserving heat, the thermal properties of the enclosure walls are inadequate, and the mode of heating is inefficient. The heat transfer parameters, heat lost and gained through fabrics, and thermal properties of nanomaterials have been used to improve the thermal comfort analysis. Combined with the local economic conditions, passive design strategies such as optimizing the spatial layout, improving the thermal insulation performance of the enclosure walls, and using solar energy were implemented. The simulation results indicate that energy consumption can be significantly reduced, and the indoor thermal comfort of traditional houses can be enhanced by reasonably dividing the indoor space, increasing the thermal insulation performance of the enclosure walls, and making better use of solar energy and natural ventilation. Therefore, to improve thermal comfort and reduce the energy load of traditional houses in the Guan Zhong region, it is necessary to adopt passive optimisation strategies.

Performance assessment of deep borehole heat exchanger heating system under different heating modes

Abstract With the transition towards renewable energy sources, particularly as we move away from fossil fuels, there has been a constant evolution of deep borehole heat exchanger (DBHE) coupled heat pump heating technology. On the basis of the heat-exchanging properties of circulating fluid in the DBHE heating system, this paper clarifies the setup forms of this system, and elucidates the influence of heat extraction performance. After analysis and research, it can be concluded that the direct supply mode shows a more prominent decline in water temperature compared to the coupled heat pump and coupled plate heat exchanger modes. The imported and exported water temperatures when heating ends were recorded as 9.98°C and 16°C, respectively. The imported and exported water temperatures for both the direct supply and the coupled plate heat exchanger modes tend to be similar at 19.6°C and 25.5°C at a temperature of 7°C. Heat pump not only enhances the heat exchange features of ground source heat pump (GSHP) heating system, but also defines the configuration of heat extraction performance of DBHE. The system power consumption in the coupled plate heat exchanger mode is lower than that in the heat pump mode which is conducive to stable operation. Therefore, the best design form of the DBHE Heating System is the heat pump coupled plate exchange mode.

Indoor Thermal Environment Improvement Based on Switchable Radiation/Convection-Combined Intermittent Heating: Comparison between Conventional Terminals and Integrated Novel Terminal

Intermittent heating is an energy-saving heating mode, which can save energy in terms of time, and thus is worth promoting, particularly in residential heating scenarios. Conventional radiant heating terminals, that is floor heating, and convective heating terminals, that is fan coils, cannot achieve both intermittent and thermal comfort during intermittent heating. Therefore, this study proposes a switchable convective-radiant heating regulation method for floor heating and fan coils to achieve a comfortable indoor environment with high thermal response speed. Furthermore, a novel combined radiant-convective heating terminal was proposed for a reliable and effective solution. Results showed that the proposed switchable method could increase both intermittence and thermal comfort. In addition, the heating terminal showed better heating performance than the combination of two conventional terminals at the key points of heating capacity, flexibility, and thermal response. It could initially heat up a typical residential space within 20–40 min and then stabilize the room temperature in a comfortable range of 18–22 °C, showing great potential for intermittent heating in room-scale heating conditions. This study provides a reference technique for intermittent heating with reduced system complexity and precise environmental control.

Design method and experimental study on a novel self-sustaining internal combustion burner

Peak shaving represents a particular challenge with regard to coal-fired power plants, as methods to achieve stable, high-efficiency, and low-nitrogen-oxide combustion at ultralow loads remain unavailable. In this study, based on analysis of the ignition mechanism, heating mode, and theory of preheating method, we proposed a novel pulverized coal full-time self-sustaining internal combustion burner by combining the processes of plasma ignition, reverse jetting, and multi-stage ignition. A flame stability model for the burner's recirculation zone was established using the temperature change rate of the recirculation zone as a criterion. The ignition position of the stable self-sustained combustion of the pulverized coal gas stream was determined under various working conditions, and the length of the ignition core stage, a component of the burner inside which the pulverized coal gas stream achieves stable self-sustained combustion, was determined based on the calculated maximum ignition position; a self-sustaining internal combustion burner was then designed based on the ascertained length. Subsequently, we established an experimental system for the self-sustaining internal combustion burner and conducted tests in the load range of 25 %–100 %. Notably, the results of the pulverized coal self-sustained ignition position experiment were consistent with the computational results of the model. The self-sustaining internal combustion burner offers a quick start–stop feature, with the pulverized coal able to achieve stable self-sustained combustion after the plasma igniter shuts off. The resultant gas-phase products exiting the burner met the boiler's concentration requirements for enhanced nitrogen reduction, and the burner exhibited good anti-interference properties. The influence of the pulverized coal gas stream velocity and concentration on the self-sustained ignition was expounded. Under the experimental conditions, an optimal concentration range was ascertained for stable ignition of the pulverized coal gas stream, with the ignition position gradually advancing backward with increasing gas stream velocity. Together, our findings highlight the potential of the proposed burner design to support clean and efficient pulverized coal combustion in coal-fired power plants.

A composite model for nucleate boiling heat transfer in a slush nitrogen pool

The pool boiling of slush nitrogen (SlN2) with various solid volume fractions at subatmospheric pressures is studied to establish a semi-empirical model considering the effects of phase-change solid nitrogen (SN2) particles on convective heat flux and boiling heat flux. The convective heat flux is studied with the modified correlation based on Sindt's fitting, while an improved correlation based on Rohsenow correlation with the dimensionless form of wall superheat in the range of 0<Ja∗ρ∗0.14<0.04 is obtained for the boiling heat flux. With the increasing wall superheat, the enhancement weakens till vanishes at the transition point. This point marks the separation between low- and high-heat-flux regions, where the probability of SN2 invading to thermal boundary layer diminishes to 0 %. The low-heat-flux boiling correlation considers the heat transfer enhancement due to SN2 concentration while the high-heat-flux one ignores the impact of SN2. As the components of SlN2 nucleate boiling model, the convective and boiling heat flux both show the accuracy of ±20 % with experiments. Upon analyzing the boiling curves of SlN2 with various solid volume fractions, SlN2 outperforms LN2 in coolant efficiency at moderate heat load.

The 1D model of hybrid heat pump system designed and prototyped for electric vehicles

In this paper, a one-dimensional mathematical model of a hybrid heat pump system was developed to improve the driving range of electric vehicles considering energy consumption. The generated one-dimensional model was performed in four different heating modes under various scenarios to satisfy the heating demand considering both the driving range and the target temperature. This model was run in recirculation mode in all analyses for energy efficiency. The electric heater capacity can be reduced to prevent overheating in the cabin. The fastest proposed cases reached the target temperature in 300 s. In this case, the vehicle range was lowest and varied between 72.3 % and 77.5 %. The highest vehicle range varied between 81.3 % and 86.1 % and provided sufficient heating in approximately 900 s. In addition, the effect of preheating by different capacities electric heaters, it was observed that preheating with a low-capacity electric heater had advantages. As a result, the present study shows that the dynamic behavior of the hybrid heat pump systems allows researchers to improve electric vehicles thermal management system which had a crucial role. The results of the model were in good agreement with the experimental data presented with similar boundary conditions in available literature.

Understanding the dominant intraseasonal modes of the springtime primary diabatic heating over the eastern Tibetan Plateau

Understanding the dominant intraseasonal modes of the springtime primary diabatic heating over the eastern Tibetan Plateau

Crystallization, mechanical, and heat resistance performances of copolymer polypropylene modified by α nucleating agent

AbstractPolypropylene (PP) was a very practical and important thermoplastic, which was widely used in various fields due to its low cost, universal, and corrosion resistance. However, the moderate mechanical and heat resistance properties of PP limited its application in some special fields. In this paper, nucleating agents NP‐657 were added to further improve its mechanical and heat resistance performances of PP (300H). Furthermore, the heterogeneous nucleation of NP‐657 reduced the crystal size and increased the crystal density of 300H. With the rise of NP‐657 content, the crystallization rate of different PP systems increased significantly, such as the t1/2 of 300H‐0.2 reduced by 31.9 min in comparison with that of 300H at 140°C. At the same time, the crystallinity of 300H‐0.05 with 0.05 wt.% NP‐657 increased by about 5.96% compared with 300H. In addition, 300H‐0.05 has the highest tensile strength (23.9 ± 0.6 MPa), flexural modulus (1273.3 ± 67.3 MPa), and the highest thermal deformation temperature (88.5 ± 7.7°C) in different PP systems. In general, this paper provided a reference for the fabrication of PP with satisfactory mechanical and heat resistance performances.Highlights 300H‐0.05 had a maximum crystallinity of 40.8 ± 0.2% in different PP systems. The flexural modulus of 300H‐0.05 was 434 MPa higher than that of 300H. The tensile strength of 300H‐0.05 increased to 23.9 ± 0.6 MPa. 300H had the highest thermal deformation temperature of 88.5 ± 7.7°C.

Construction of Coordination Spaces with Narrow Pore Windows in Co-Based Metal-Organic Frameworks toward CO2/N2 Separation.

Carbon emission reduction is an important measure to mitigate the greenhouse effect, which has become a hotspot in global climate change research. To contribute to this, here, we fabricated two Co-based metal-organic frameworks (Co-MOFs), namely, {[Co3(NTB)2(bib)]·(DMA)2·(H2O)4}n (DZU-211) and {[Co3(NTB)2(bmip)]·(DMA)2}n (DZU-212) (H3NTB = 4,4',4″-nitrilotribenzoic acid, bib = 1,4-bis(imidazol-1-yl)-butane, bmip = 1,3-bis(2-methyl-1H-imidazol-1-yl)propane) to realize efficient CO2/N2 separation by dividing coordination spaces into suitable pores with narrow windows. DZU-211 reveals a 3D open porous framework, while DZU-212 exhibits a 3D double-fold interpenetrated structure. The two MOFs both possess large coordination spaces and small open pore sizes, via the bib ligand insertion and framework interpenetration, respectively. Comparatively, DZU-211 reveals superior selective CO2 uptake properties due to its more suitable pore characteristics. Gas sorption experiments show that DZU-211 has a CO2 uptake of 52.6 cm3 g-1 with a high simulated CO2/N2 selectivity of 101.7 (298 K, 1 atm) and a moderate initial adsorption heat of 38.1 kJ mol-1. Moreover, dynamic breakthrough experiments confirm the potential application of DZU-211 as a CO2 separation material from postcombustion flue gases.

Investigation of a high-temperature combination heat pump for lower-cost electrification in multifamily buildings

The development of space and water heating combination heat pumps capable of generating water temperatures high enough for convective heat emitters will enable more cost-effective and equitable decarbonization solutions for electrifying multifamily buildings. In this paper, multifamily building models and a charge-sensitive mechanistic cycle model of a combination heat pump are developed, and the system performance is predicted based on the models. Unlike other state-of-the-art residential heat pumping equipment, the modeled combination heat pump using an economized, fluid-injected variable-speed compressor can achieve higher temperature lifts of 40° – 85°C, with lower installation costs and complexity. The model predicted heating coefficient of performance (COPh) is 2.1 at an ambient temperature of −15°C with a high-temperature lift of nearly 85°C, and a seasonal coefficient of performance in heating mode (SCOPh) ranges from 2 – 4 for different locations. The system shows 30% – 90% lower CO2eq emissions over a condensing gas boiler and 9% – 13% lower projected installation costs than two separate space and water heat pumping appliances.

Localized and delocalized topological modes of heat.

The topological physics has sparked intensive investigations into topological lattices in photonic, acoustic, and mechanical systems, powering counterintuitive effects otherwise inaccessible with usual settings. Following the success of these endeavors in classical wave dynamics, there has been a growing interest in establishing their topological counterparts in diffusion. Here, we propose an additional real-space dimension in diffusion, and the system eigenvalues are transformed from "imaginary" to "real." By judiciously tailoring the effective Hamiltonian with coupling networks, localized and delocalized topological modes are realized in heat transfer. Simulations and experiments in active thermal lattices validate the effectiveness of the proposed theoretical strategy. This approach can be applied to establish various topological lattices in diffusion systems, offering insights into engineering topologically protected edge states in dynamic diffusive scenarios.

A study of capacity demands for heat pumps intermittent heating of China’s residences

Heat pump heating is one of the most promising solutions for transitioning residential heating in China’s cold regions, as well as hot summer and cold winter regions from centralized, continuous heating to decentralized, intermittent heating, promoting low-carbon transformation. However, the fundamental issue of the actual capacity requirements for heat pumps in intermittent heating has not yet been addressed. In view of this, this study developed a numerical model that considers the dynamic coupling characteristics between the heat pump and the building environment. Using the model, the worst startup conditions for heat pumps in intermittent heating, actual heat pump capacity demands, and the differences in capacity compared to continuous heating mode for residential buildings in 230 Chinese cities are analyzed. The findings revealed an exponential relationship between intermittent heating capacity demands and time constraints, as well as a linear relationship with heating temperature. Specifically, the impact of the set temperature on capacity demands in cold regions and hot summer and cold winter regions is 22.8 W/(m2·°C) and 32 W/(m2·°C), respectively. These findings provide insights into the planning and design of future intermittent heating renovation projects in China.