Large-scale Heat Research Articles

A penalty-free hybrid algorithm framework based on feasible stream matching principle for large-scale heat exchanger networks synthesis

In this work, a penalty-free hybrid stochastic-deterministic algorithm framework is proposed for large-scale heat exchanger networks (HENs) synthesis (HENS), formulated as a computationally-hard mixed-integer nonlinear programming (MINLP) problem. In the outer level, an improved genetic algorithm (GA) is developed to optimize process stream matches represented by integer variables whose values are generated by a unique heat exchanger vector. Unlike previous researches, the improved GA does not rely on any penalty terms, because we propose a feasible stream matching principle to exclude all infeasible process stream matches and only feasible matches are considered in optimization process. In the inner level, a reduced-size MINLP model is solved using deterministic methods to minimize total annualized costs (TACs), which are then used to evaluate the fitness of candidate HENs. Through this way, the proposed framework combines deterministic and stochastic methods to enhance optimization efficiency and global search capability. Illustrative tests on six benchmark cases demonstrate that the framework can efficiently achieve lower-cost solutions compared to deterministic, stochastic, or hybrid methods. The results show a decrease in TAC for all six cases and a reduction in solution time ranging from 11.1% to 97.2%. Importantly, the proposed framework can be extended to solve MINLP problems in other process networks.

Potential of treated wastewater as an energy source for district heating: Incorporating social elements into a multi-factorial comparative assessment for cities

Recovering waste heat from urban infrastructures is gaining greater importance in the context of decarbonisation. However, evaluating the feasibility of waste heat recovery projects requires a holistic analysis of potential impacts, which includes social elements that are often overlooked. This paper introduces a novel methodology for assessing the competitiveness of waste heat integration into district heating, based on a multi-factorial decision support tool that incorporates energy poverty as a key performance indicator, in addition to energy, environmental and economic factors. The comparative assessment is based on the implementation of large-scale heat pumps recovering wastewater heat, a resource of great potential that is still underutilised in Europe. The methodology is tested in the cities of London and Riga, which are in countries with significantly different stages of DH development. In London, an emerging market with high growth potential, and in Riga, where there is a well-established DH system. The study has shown that waste heat can significantly reduce consumers' bills for heating, which was observed in all analysed scenarios. The social benefit decreases when the replaced technology involves biomass heat-only boilers or combined heat and power. The methodology presented is generic and can be applied to other locations and heat sources.

Solar district heating system with large heat storage: Energy, exergy, economic and environmental (4E) analysis

In the context of the global energy crisis and climate change, solar district heating systems are an essential technology that can mitigate this problem. To accelerate the transition to sustainability, a proven solar district heating system and an analysis method are needed to serve as a role model. For this purpose, a techno-economic analysis method is proposed in this study. It consists of a bi-directional long short-term memory method for correcting outlier data and a balanced method for energy and exergy analyses. The solar district heating system with large-scale thermal storage in Dronninglund, Denmark, is investigated in detail. The design of this system is centered on an integrated control strategy that synchronizes the solar collector loop, the energy storage loop, and the heating load loop to improve overall efficiency. The results show an increase in solar collector efficiency to 41 %, thermal storage efficiency to 89 %, and a coefficient of performance to 1.74 for the absorption heat pump. This integration increases the system’s coefficient of performance dramatically to 2.9, with a renewable energy percentage of 77 %. Exergy analysis shows a storage exergy of 68 % and a heat pump exergy of 49 %, which suggests that the system has a highly efficient energy conversion. The annual heating demand for the industrial and residential branches is 7,450 MWh and 28,100 MWh, respectively, which are covered by solar (42 %), biomass oil (35 %), and natural gas (23 %). The economic assessment shows that the net present value could rise from −5.5 million euros over 10 years to 15.2 million euros over 40 years, indicating long-term economic advantages. The system achieves 122 kg/MWh of carbon reduction with a 0.92 carbon neutrality factor, which is carbon neutral. This study provides a compelling case for deploying large-scale solar heating systems, offering a robust analysis method and insightful findings for technological developments and economic optimizations.

Improved heat transfer mathematical model forpyramid shaped seasonal heat storage water pit and the influence of boundary conditions

Seasonal heat storage can make use of urban waste heat for low-carbon heating throughout the year. Previous models for pyramid shaped water pit have limited adaptability and ignore the impact of soil temperature in the early stages of operation on the performance of water pits. This article combines two classic mathematical models to establish a mathematical model that can adapt to various sizes of inverted pyramid shaped water pits. The validation of this model was conducted using experimental data from 60000 m3 water pit of Dronninglund, and the influence of boundary conditions for this module were calculated and discussed. The results showed that the root mean square errors of the simulated top, bottom, and average temperature of the water pit were 3.07 °C, 2.39 °C, and 1.37 °C, with relative deviation ratios of 4.25 %, 2.27 %, and 6.62 %, respectively. Furthermore, it was found that for every 5 °C increase in the set average soil temperature, the storage efficiency of the water pits increases by 0.4 %∼0.5 %. In the case of common top insulation of the water pit, the total heat loss at the top, side walls, and bottom are 66.83 %, 31.8 %, 1.37 %. While considering comprehensive insulation in all directions, the heat loss rate for the top, side walls, and bottom are similar with the former, being 67.84 %, 30.79 %, and 1.37 %, respectively. The proposal and findings of this article provide a basis for simplified optimization planning and design of large-scale seasonal heat storage systems.

Lightweight Reseach of Tube Sheet for Spiral Wound Heat Exchanger Based on ANSYS

Abstract Tube sheet is the key pressure-bearing part in the spiral wound heat exchanger, and the high-strength and light-weight tube sheet structure is of great engineering significance for the development of a large-scale heat exchanger. In order to further realize the lightweight of the spiral-wound heat exchanger, this paper analyzes the influence of the thickness of the heat exchanger tube sheet on its strength based on the Ansys software and proposes the optimization design method of the tube sheet based on the strength safety factor F, which solves the problem that the software cannot take the stress linearization result as the state variable in the optimization calculation. The optimization results show that the thickness of the tube sheet is reduced by 40%. At this time, the stress strength at the connection between the tube sheet and the head and the center of the tube sheet first exceeds the design bearing capacity, indicating that the strength conditions of the two places are the controlling factors of the thickness. The results are important for the lightweight design of heat exchanger tube plate and material saving.

Structure and mechanism of directional heat induced asphalt pavement with thermal aggregation effect

Efficiently and actively dissipating accumulated heat within asphalt pavement is crucial for reducing pavement distress and improving subgrade stability. This paper proposed a novel inverted “T” shaped heat induced structure (IT-HIS) that facilitates the rapid transfer of heat from the pavement to the subgrade and shoulders. The IT-HIS consists of two components: a vertical gradient thermal conductivity structure utilizing steel slag, and a horizontal oriented carbon fiber heat induced structure. The heat transfer behavior of the IT-HIS was analyzed using a finite element heat transfer model created in ABAQUS, and the results were validated through indoor irradiation experiments. The findings demonstrated that the IT-HIS enhanced heat flow and promoted secondary aggregation in the vertical direction, while facilitated lateral heat dissipation. Compared to the ordinary group (OG), the heat flux of IT-HIS at depths of 5 cm and 6.5 cm increased by 19.8 % and 64.6 %, respectively. The indoor irradiation experiment results indicated that during the heat absorption period, the IT-HIS reduced temperatures at depths of 0 cm, 2 cm, and 5 cm by 1.5 ℃, 1.7 ℃, and 1.1 ℃, respectively. During the heat dissipation period, the IT-HIS reduced temperatures at depths of 0 cm, 5 cm, and 10 cm by 0.9 ℃, 0.7 ℃, and 1.8 ℃, respectively. The IT-HIS enhanced the cooling effect during daytime and inhibited heat upward during nighttime based on the gradient thermal conductivity structure. The proposal and validation of this structure provide a fundamental approach to forming large-scale high-speed microchannel heat dissipation within asphalt pavements, and is expected to provide experimental and theoretical foundations for the development of directional active cooling technologies.

Dual-porosity approach: heat transfer and heat storage processes in porous media

ABSTRACT This study emphasizes the significance of understanding groundwater flow behavior for effective contaminant transport and heat storage. Aquifers, with their irregular shapes and variable permeability, exhibit anisotropic flow resistances that affect mass and heat transfer, posing challenges for modeling. The dual-porosity model is used as a numerical approach to calculate macroscopic heat transfer without explicitly resolving the structure. By solving equations for mobile and immobile phases and coupling relevant equations for heat conservation, this model was applied to transient numerical experiments simulating heat transfer and storage in a desktop model filled with glass beads. Results indicate alignment with experimental and numerical models resolving porous structures on the microstructure scale. This methodology offers a comprehensive digital toolbox for solving large-scale heat storage problems in aquifers, contributing to digital and sustainability transformations with reasonable computational demands.

Real-time monitoring and optimization of a large-scale heat pump prone to fouling - towards a digital twin framework

Large-scale heat pumps are a promising technology for the decarbonisation of heat supplied in buildings and industries, provided they operate as expected. However, common faults like fouling and unplanned downtime periods can significantly affect their performance and availability. This could limit the widespread adoption of large-scale heat pumps over other heating technologies such as gas and electric boilers. Approaches described in the literature to optimize the operation of large-scale heat pumps often lack validation under real-world conditions and do not account for performance degradation due to faults. This work demonstrates a step towards utilizing digital twins to improve the energy performance of a commercial large-scale heat pump affected by fouling. A framework was proposed based on the real-time adaptation of digital twins, where a simulation model was calibrated online based on measurements from the heat pump in operation, which was then used for set point optimization. This enabled to determine optimal intermediate pressure set points in the heat pump operating under varying levels of fouling over time. The framework was tested on different periods of heat pump operation spread over ten calendar months. The results showed that the use of online calibration rather than a single calibration decreased performance estimation errors between 3 and 17 percentage points. Moreover, the set points determined by the online-calibrated model, along with a simpler polynomial model derived from it, showed improvements in the heat pump performance by up to 3%, depending on the level of fouling. The findings of this study demonstrated the potential to extend the proposed framework using digital twins to enhance the energy efficiency of large-scale heat pumps.

Centrifugal compressor design and cycle analysis of large-scale high temperature heat pumps using hydrocarbons

Using natural refrigerants in heat pumps, including hydrocarbons, is becoming attractive because of the tightening regulations concerning synthetic refrigerants. In the literature there is lack of studies investigating detailed component design, including compressor design when using hydrocarbons. This study investigates numerically centrifugal compressor design with hydrocarbons for large-scale high-temperature heat pumps. The compressor analysis was combined with a thermodynamic analysis of a two-stage heat pump. The effect of temperature lift and flash intercooler temperature on compressor sizing, rotational speed, efficiency, axial force, and Mach number were investigated. Generally, the use of hydrocarbons with five carbon atoms resulted in higher coefficient of performance and required lower compressor rotational speeds and larger compressor dimensions when compared to the hydrocarbons with four carbon atoms. The simulated rotational speeds were ranging from 8 krpm to 30 krpm, impeller diameters from 0.15 m to over 0.7 m and compressor efficiencies from 77% to over 85%. The use of cyclic molecules, namely cyclopentane and cyclobutene resulted in the highest heat pump coefficient of performance. Also, the flash intercooler temperature had a notable effect on the compressor design and axial force which has to be taken into account in heat pump cycle design.

Assessment of Grid and System Supportability Based on Spatio-Temporal Conditions—Novel Key Performance Indicators for Energy System Evaluation

The energy transition introduces new technical standards, laws and regulations regarding the stability and reliability of energy grids and systems. Due to the non-existence of a measuring standard, key performance indicators (KPIs) were developed to enable the measurement and comparison of individual energy grid (namely electricity, heat and gas grid) and system supportabilities while also promoting well-founded decision-making and optimization efforts. Inconsistencies in definitions concerning fundamental energy terms and the correlations between them inhibit the effective usage of the KPIs. Therefore, the overarching issue of the security of energy supply and its related subjects were also approached. The primary subject of this paper is the development of two new KPIs to measure and compare the energy grid and system supportability. These KPIs are based on spatio-temporal conditions in their respective grids. The usage and benefits of the developed KPIs are exemplarily highlighted by analyzing the impact of a scenario with the integration of a large-scale heat pump into the electricity and heat grid. The energy grid supportability is determined for each grid, whereas the energy system supportability takes the interactions of the electricity and heat grid into account. The developed KPIs are intended to enable stakeholders to identify areas with optimization potential in energy grids and systems. Moreover, the KPIs can be used to create a standardized evaluation method for regulatory requirements.

Improving the combustion of scramjet engines with struts using grooves and bumps

Grooves and bumps are arranged on both sides of a normal strut (NS) to fabricate vortex generators, and introduce streamwise vortices. Struts with sawtooth grooves (GS-1), rectangular bumps (BS-1), and trapezoidal and triangular bumps (BS-2) have been proposed. In this study, struts with V-shaped grooves (GS-2) and trapezoidal and triangular bumps (BS-3) were configured. The flow fields in the cold and hot states of scramjet combustors with NS, GS-1, GS-2, BS-1, BS-2, and BS-3 were simulated numerically using steady RANS equations and an SST k-ω turbulence model. The results show that proper arrangement of the grooves and bumps on the strut can improve the mixing and combustion performance. Compared with the NS, for GS-1, GS-2, BS-1, BS-2, and BS-3, the distance required to achieve 100% fuel mixing efficiency is shorter by 21.2%, 9.1%, 18.2%, 12.1%, and 15.2%, respectively, and to achieve 100% combustion efficiency, the distance is shorter by 42.7%, 46.9%, 47.9%, 53.1%, and 58.3%, respectively. Therefore, improvement in combustion performance does not positively correlate with improvement in the mixing performance. Large-scale heat and mass convection in streamwise vortices play a dominant role in mixing. The larger the proportion of the fuel area affected by the streamwise vortices, the more conducive it is to achieving a higher mixing performance, whereas the wall has a negative impact. However, the large-scale heat and mass convection in the streamwise vortices and small-scale heat and mass convection in the high-turbulence zones are closely related to the supply of oxygen and fuel required for the combustion zone. Large-scale streamwise vortices combined with thick high-turbulence zones are conducive to achieving a high combustion rate. When the recirculation zone has a larger combustion area and smaller wall effects, a higher combustion performance is easily achieved. Compared with the grooves, the stronger disturbance effect of the bumps on the fluid effectively increased the thickness of the high-turbulence zone, thus obtaining a higher combustion performance. However, the greater blocking area and new oblique shockwaves generated by the bumps induced a greater total pressure loss. Therefore, combining bumps and grooves can further optimize strut configurations.

Solving large-scale combined heat and power economic dispatch problems by using deep reinforcement learning based crisscross optimization algorithm

The extensive interconnection in bulk power systems brings great challenges in the economic dispatch problems, especially the large-scale combined heat and power economic dispatch (CHPED), which is quite intractable due to complex thermal and electrical couplings in cogeneration units. Most meta-heuristic algorithms cannot work well while considering non-convexity, discontinuity, and non-differentiability. Particularly, when it comes to the high dimensional and large-scale CHPED problems, these algorithms are either easy to trap in the local optimum or quite time-consuming. To address these issues, a novel deep reinforcement learning (DRL) based crisscross optimization (CSO) algorithm is proposed for the first time, which can (1) improve the searching ability of CSO, (2) enhance the overall searching efficiency, and (3) perform extraordinarily well for the large-scale CHPED problems. Firstly, to further improve the global search ability, DRL is employed to reduce dimensionality and narrow the search space of the initial population of the CSO algorithm. Then, DRL is updated by the deep deterministic policy gradient (DDPG) strategy, which can facilitate an instantaneous decision in accelerating CSO. Thereafter, by adopting each decision provided by DRL, a great difference may occur in the same scenario to speed up the crossover procedure and guide the upcoming search round. On this basis, the enhanced CSO algorithm could quickly carry out crossovers with search space contraction and dimensionality reduction. Finally, experiments on four test systems have substantiated the effectiveness of the proposed algorithm, especially the superiority over other state-of-the-art techniques in solving large-scale CHPED problems.

Innovative Power Generation Technologies for Improved Household Energy Delivery and Sustainable Future: Classical Solutions from ENEA Research Centre, Trisaia Italy

The present communication is focused predominantly on important R&D solutions relevant to renewable energy technologies covering the following: (i) Innovative heat transfer fluid and thermal storage technology based on a molten salt mixture developed by ENEA for large-scale heat storage. The system uses a parabolic trough collector, compared with diathermic oil, which allows higher operating temperature, resulting in significant benefits to the plant’s operation, safety and the environment. (ii) The world’s first solar disk powered by air micro turbine developed by ENEA. (iii) An innovative steam-explosion prototype plant installed at ENEA for the pre-treatment of lignocellulosic biomass and the fractionation of bio components to generate ethanol from lignocellulosic material using hemicellulose and lignin. (iv) The production of hydrogen-enriched biogas using steam as the gasification agent, which helps in obtaining nearly nitrogen-free product gas and with a high calorific value of around 12 MJ/Nm3 dry gas and a high percentage of hydrogen (up to 55%) while using steam as the gasifying agent in the presence of a catalyst. (v) A rotary kiln plant, with the main purpose being to develop and optimize a thermo-chemical process to convert used rubber tyres so as to recover material and energy, as well as other solid products, with high value-added “Activated carbon” and synthesis gas.

Semi-analytical model of a large-scale water pit heat storage for the long-term thermal applications

Solar district heating systems reduce carbon emissions effectively. Large-scale water pit thermal energy storages (PTES) have high heat capacities, low costs per cubic volume, and long lifetimes. Integrating PTES with a solar heating system can significantly increase solar heating efficiency and alleviate the time and climate constraints of renewable energy. An improved TRNSYS semi-analytical model of PTES (Type 1535–1301) is proposed based on the finite difference method. The model is characterized by discretizing the energy equation and then combining it with the analytical solution of the full differential equation to find the temperature variation. The model is validated with a full year measurement on a Danish PTES. In addition, a parametric investigation of grid discretization, storage geometry, soil properties, and diffuser location is performed. The control strategies are investigated to best utilize the PTES for demand response. The results indicate that the Type 1535–1301 model accurately predicts the year-round thermal performance of the PTES. The differences between the calculated and measured energies are lower than 1.3 %, and the differences between the calculated and measured temperatures are lower than 2.8 K. With an increase of the slope angle of the PTES side wall, the top and side heat losses decrease, and the storage temperature and thermal stratification effectiveness improve. Furthermore, the relative Fourier number (Fom) is proposed to represent the soil thermal diffusivity. The rise ofFom leads to an increase of heat loss and a decrease of storage efficiency. The analysis show that the top diffuser is best located at the highest position, and the bottom diffuser is best placed at the lowest position. At the same time, the middle diffuser is best placed at 29 % of the total volume from top to bottom. The semi-analytical model in this paper decreases the annual heat transfer computation time for a single grid to 57 ms. The model has been embedded into TRNSYS for convenient system prediction. The findings of this paper can be used as a reference for engineering practice and subsequent research.

Hundred-Watt Implantable TEG Module for Large-Scale Exhaust Gas Waste Heat Recovery

In this study, we have designed and developed an implantable thermoelectric generator (TEG) module tailored for large-scale flue gas waste heat recovery. We also have established a test stand to simulate diverse operational conditions, and systematically examined the influence of different operating conditions, including flue gas temperature, flue gas velocity, and cooling water temperature, on the electrical performance of the TEG module. When the flue gas temperature is 139 °C, the flue gas flow rate is 3.4 m/s, and the cooling water temperature is 20 °C, the TEG module operates at its peak performance. It achieves an open-circuit voltage of 856.3 V and an output power of 150.58 W. Furthermore, the TEG module demonstrates a notable power generation capacity of 3.86 kW/m3 and a waste heat recovery capacity of 135.85 kW/m3. The results prove the TEG module as an effective solution for large-scale flue gas waste heat recovery in industrial settings, contributing to sustainable energy practices. This study supports the application of thermoelectric power generation in the industrial sector, offering significant potential for advancements in energy efficiency.

Microwave dielectric characterization and loss mechanism of biowaste during pyrolysis

The effectiveness of microwave heating of biomass depends on the changes in dielectric properties. This study systematically investigated the microwave dielectric properties and loss mechanism of biowaste at different frequencies (915 and 2,450 MHz) and temperatures (25–800 °C) using the cavity perturbation method. The gas emissions and properties of the biochar produced during pyrolysis were characterised by SEM, XRD, and TG-FTIR. The findings revealed that the dielectric properties and penetration depth of the biomass and biochar changed significantly during microwave pyrolysis. The dielectric constant and dielectric loss coefficient first increased and then decreased during the drying stage, and they decreased continuously with the volatile’s generation in the pyrolysis stage, while the formation and high conductivity of biochar promoted a sharp increase in dielectric properties during the carbonisation stage. The loss tangent angle is 0.01–0.05 in the first two stages, while it increased to 0.10–0.25 in the carbonization stage, demonstrated that the biowaste is a low-loss material. However, the microwave absorption capacity was enhanced for pyrolyzed biochar. The loss mechanism revealed that dipole polarisation primarily contributes to the dielectric loss during the drying and pyrolysis stages, whereas interfacial polarisation plays an important role during the carbonisation stage. The data provided in this paper contribute to the evaluation of microwave penetration depth in biomass and the design of large-scale microwave-based heating systems. Furthermore, this study offers a theoretical basis for modelling and simulating the microwave heating of biomass and achieving efficient energy conversion.

GPU-DEM-based heat transfer model for an HTGR pebble bed

Based on the discrete element method (DEM) and GPU parallel computing, a particle heat transfer model is developed to simulate the heat transfer in a pebble bed of the high-temperature gas-cooled reactor (HTGR). The model is implemented based on a previously developed GPU-DEM program by our team and uses the mesh-based neighbor searching algorithm for the heat transfer calculation. This model couples the conduction and radiative heat transfer between the pebbles and incorporates neural networks and empirical fittings to calculate the radiation view factors, which can improve computational efficiency. The effective thermal conductivity of different models and experimental data are used to verify the accuracy of the model, and the influence of different radiation heat transfer models on the results is also compared. The results show that the effective thermal conductivity derived from the current model is comparable to the classical models at different temperatures, and the numerical simulation results based on the current model are in good agreement with the corresponding experimental data. Additionally, the model achieves a single-core speedup ratio of 126–395 times with GPU acceleration, significantly enhancing computational efficiency. In conclusion, the current model has been effectively verified for accuracy and computational efficiency, and it demonstrates great potential in dealing with large-scale pebble flow and heat transfer challenges in HTGRs.

Mechanisms and characteristics of wall skin friction reduction by boundary layer injection under hypervelocity inflow conditions

In this paper, the influences of boundary layer injection on skin friction reduction are numerically studied using Reynolds-averaged Navier-Stokes equations. The methodology is first validated by comparing the numerical results with the existing experimental data. Studies on the effects of inert gas boundary layer injection reveal that boundary layer injection forms a gas film cooling effect, which reduces skin friction through low viscosity and low temperature effects. However, the enhancement of turbulence in the boundary layer by the jet weakens this effect For fuel boundary layer injection, boundary layer combustion creates a low-density environment in the boundary layer, reducing the momentum transport of the fluid to the wall and significantly enhancing the drag reduction effect. Based on this, the drag reduction effect of boundary layer combustion is found to decrease significantly under mainstream heat release conditions, mainly due to the large-scale heat release in the outer edge of the boundary layer, which puts the fluid in a high-temperature and high-pressure state as a whole, and boundary layer combustion cannot establish a “barrier” for momentum transport in a low-density region.

Improvement of Moso Bamboo (Phyllostachys pubescens) Properties Using a Heat Treatment Process for Landscaping Materials and Evaluation of Its Durability against Biotic/Abiotic Factors

This study aimed to assess the effectiveness of large-scale heat treatment on Moso bamboo (Phyllostachys pubescens) grown in South Korea. The process involved multiple stages, including pretreatment, boiling, steaming, heating, and cooling. Heat treatment successfully reduced the water content to below 3% and increased the specific gravity from 0.62 to 1.12, thereby enhancing dimensional stability and strength. Following an ultraviolet-accelerated weathering test, the heated Moso bamboo exhibited improved color stability (ΔE 5.84) compared to untreated bamboo (ΔE 9.92). Furthermore, the heat-treated bamboo demonstrated high resistance against wood-rot fungi (weight loss < 10%) and termites (weight loss approximately 2%). In contrast to small lab-scale drying processes, this study employed a pilot-scale kiln for mass production, resulting in large-sized Moso bamboo with enhanced properties. This study revealed that distinct results, including extractives and lignin-degraded compounds, persisted in heated Moso bamboo cells after the heat treatment. The overall improvement in deterioration resistance, achieved through heat treatment, significantly contributes to the durability and longevity of bamboo materials in outdoor settings, such as landscape facilities.

Contrasts of Large-Scale Moisture and Heat Budgets between Different Sea Areas of the South China Sea and the Adjacent Land

Abstract This study investigates and compares large-scale moisture and heat budgets over the eastern rainy sea area around Dongsha, the western rainless sea area around Xisha, and the northern coastland of the South China Sea. Ten-year (2011–20) surface, balloon-sounding, satellite measurements, and ERA5 reanalysis are merged into the physically consistent data to study annual and vertical variations of the budgets. It shows that the surface and column-integrated heat and moisture budgets have the smallest annual evolution over the coastland. The latent heat as a key heat contributor in summer is mainly offset by total cold advection and partially offset by net radiative cooling. The horizontal moisture advection below 700 hPa presents moistening over the sea whereas drying over the coastland during rainy months, in which the vertical moisture advection presents moistening up to 250 hPa for all three subregions. The horizontal temperature advection is weak throughout the year over the sea but displays strong top warming and bottom cooling in summer and nearly the opposite in winter over the coastland. The diabatic cooling with a peak at ∼700 hPa in winter is largely due to the enhanced radiative cooling and latent cooling. While the diabatic heating with a peak at ∼500 hPa in summer is largely due to the enhanced latent heating. The earliest atmospheric heating and moistening occur in spring over the coastland, inducing the earliest precipitation increase. The enhanced heating and moistening over Xisha have a 1-month lag relative to Dongsha, resulting in lagging precipitation.