Coupled Heat System Research Articles

Performance and economic analysis of a novel water storage tank coupled with geothermal heating System: A field test

This study tackles the underutilization of geothermal resources for building heating by introducing a novel water storage tank designed to enhance efficiency and reduce operational costs. We established a field experimental system to assess this geothermal-energy storage coupled heating system under various thermal loads, comparing its performance against traditional systems. The key findings include: (1) The novel water tank achieves release/storage ratios of over 85% under various loads, surpassing existing water storage systems and demonstrating superior performance. (2) The thermal storage efficiency exceeds 45% under all load conditions, reaching up to 100% at low loads, highlighting the tank’s crucial role in energy conservation. (3) Compared to traditional systems, the coupled heating system significantly reduces operating costs, with reductions exceeding 20% under different loads. These results indicate that the novel tank not only boosts efficiency but also offers notable economic advantages. The innovative design and its validation in the field enhance existing literature by providing a viable, efficient solution for geothermal heating, encouraging broader adoption of geothermal energy and aiding in carbon emission reduction.

Thermal performance research on a novel coupled heating system combined solar air heater with ventilation PCM wall

Solar heating technology is increasingly recognized as a prominent option for clean building heating. However, challenges such as intermittent thermal energy supply and supply–demand mismatch hinder its widespread adoption. To address this issue, this paper introduces a novel coupled heating system that combines a solar air heater with a ventilation Phase Change Material (PCM) wall. A rural residential house in Tianjin was chosen as an experimental platform and comparative experiments was conducted to compare the advantages of the ventilation PCM wall with the conventional wall. Additionally, numerical simulations were utilized to address the non-uniform heat transfer in the direction of the Heat Transfer Fluid (HTF) flow by employing cascaded PCM. The experimental results demonstrated that the coupled heating system exhibited high thermal storage and release efficiency, significantly improving indoor thermal comfort. Under optimal operating conditions (air supply temperature: 35-45℃, air supply speed: 3–4 m/s), the system achieved rapid thermal storage within 4 h, reaching a maximum thermal storage efficiency of up to 87.6 %. The test room maintained a nighttime temperature of 15.7 °C, exhibiting temperatures 6.3–10 °C higher than the control room. Numerical results revealed that the cascaded PCM enhanced the thermal storage rate, particularly at the first 2.8 h of the thermal storage period, contributing to the overall efficiency and flexibility of the system. This research provides theoretical guidance for the optimal design and practical application of the ventilation PCM wall.

Experimental study of coupled solar and air source heat pump heating system

To increase the heating stability and system energy efficiency as well as to offer technical assistance for promoting and deploying multi-energy coupled heating technology in village and township buildings, a solar-air source coupled heating system is suggested and developed. The experiment was conducted on a multi-energy coupled heating system for a village and town office building in Hun nan New Area, Shenyang City, over a period of 15 days, with an average daily solar radiation intensity of 558.62 w/m2-h and an average outdoor temperature ranging from -18.3 °C to -2.7 °C. The trial findings demonstrated that all indoor temperatures could exceed 18 °C while the system was in use, and the average value of the system’s overall energy efficiency was 2.45.

Optimal control study of solar-air source heat pump coupled heating system operation

With China’s ambitious goals of carbon capping by 2030 and carbon neutrality by 2060, the multi-energy coupled clean heating technology represented by solar-air source heat pumps is developing rapidly. In order to solve the above problems, this paper analyzes the characteristics of the multi-energy coupled heating system by establishing a virtual simulation model and optimizing the system operation and control modes. Technical support is provided for efficiently utilizing multi-energy coupled heating technology in rural buildings.In this paper, the mathematical model of the system is established by analyzing the form and working principle of the solar-air source heat pump coupled heating system. Initially, three operation strategies are constructed: priority utilization of solar energy strategy (Strategy I), air source heat pump fixed temperature switching strategy (Strategy II), and air source heat pump timed switching strategy (Strategy III), laying the foundation for operation strategy optimization.The dynamic load change pattern of the building in winter was calculated using TRNSYS software, based on which equipment selection was carried out, and a simulation model of the solar-air source heat pump coupled heating system was established. The system operation strategy was optimized. A temperature difference control strategy was used for the solar collector cycle control optimization, which increased the solar collector efficiency by 12% compared to the fixed temperature control strategy. Based on typical climate data, the heating season was divided into 10 phases according to a 15-day cycle, and three operation strategies were optimized and compared for each phase with the goal of comprehensive system energy efficiency. After comparison and analysis, strategy 1 and 3 have their advantages in different stages of the heating season. The operation strategies with higher system energy efficiency in each stage were combined in the heating season, called combined operation strategy (strategy 4), and compared with other strategies in the heating season. Compared with strategy 1 and strategy 3 in the whole heating season, the system energy efficiency of strategy 4 was improved by 3%-6%. This indicates that strategy 4 has better operation effect.

Feasibility study on solar coupled gas-fired boiler heating system retrofit in residential buildings in the HSCW zone of China

Residential buildings in the hot summer and cold winter (HSCW) zone rely on gas-fired boiler for heating have a certain application basis, but high operating costs and limited gas consumption seriously limit the promotion of gas-fired boiler. To reduce domestic gas consumption in Wuhan, two solar auxiliary gas-fired boiler heating systems formed in parallel and series are proposed and explore the feasibility of coupled heating system retrofit. The simulation models of two solar coupled gas-fired boiler heating systems are established by TRNSYS, and the results indicate that the indoor thermal environment of the two systems is good and the temperature of the tank is stable. The solar fraction of the parallel system reaches 24.40%, which has better energy saving. The optimization analyses display that the system has the best economy when the collector area ratio is 10.0%, and the collector area and tank volume ratio is 8/0.7. The solar-assisted parallel heating system retrofit can save 2.02 × 104 MJ over the entire life cycle, and the increased initial investment can be recovered within 4.75 years. The research results can provide a basis and new ideas for the heating retrofit of the gas-fired boiler in residential buildings in the HSCW zone.

Performance Analysis of the Coupled Heating System of the Air-Source Heat Pump, the Energy Accumulator and the Water-Source Heat Pump

In the remote areas of northern China without central heating and gas supply, for users intending to replace coal-boilers, the air-source heat pump system is always questionable due to the contradiction between its heating capacity and user’s heating demand, especially in very cold areas, whose COP and economy is very poor. The accumulator with phase change materials would be a promising one to solve this problem. With the help of TRNSYS software, a heating system coupled with air-source heat pump, accumulator, and water-source heat pump and its operation mode are provided and analyzed based on the heat source renovation demand of a middle school in Tianshui City suburb which has 5560 m2 area to be heated. The average COP simulated during the heating period of the coupled heating system is 2.23. Based on the simulation model and results, the heat source renovation of the middle school in Tianshui City suburb was carried out, its tested and simulated COP over the day was 2 and 2.05, respectively, which also reveals the validity of the numerical method for this problem.

Land-atmosphere-ocean coupling associated with the Tibetan Plateau and its climate impacts.

This paper reviews recent advances regarding land–atmosphere–ocean coupling associated with the Tibetan Plateau (TP) and its climatic impacts. Thermal forcing over the TP interacts strongly with that over the Iranian Plateau, forming a coupled heating system that elevates the tropopause, generates a monsoonal meridional circulation over South Asia and creates conditions of large-scale ascent favorable for Asian summer monsoon development. TP heating leads to intensification and westward extension (northward movement) of the South Asian High (Atlantic Intertropical Convergence Zone), and exerts strong impacts on upstream climate variations from North Atlantic to West Asia. It also affects oceanic circulation and buoyancy fields via atmospheric stationary wave trains and air–sea interaction processes, contributing to formation of the Atlantic Meridional Overturning Circulation. The TP thermal state and atmospheric–oceanic conditions are highly interactive and Asian summer monsoon variability is controlled synergistically by internal TP variability and external forcing factors.

Performance Analysis of Heating Supply from a Coupled CCHP system with Ground Source Heat Pump

A coupled heating system with combined cooling heating and power (CCHP) system and ground source heat pump (GSHP) is proposed in this paper. The system adopts the internal combustion engine (ICE) to drive the generator to generate electricity, then the jacket water from ICE is used to absorption heat pump and/or preheats GSHP to increase the coefficient of performance (COP), and the exhausted gas is sent to the high pressure generator to drive the absorption heat pump. The mathematical models of components were established, through the analysis of the relationship between the various devices and operational characteristics. Then, the performance analysis of the system is carried out under the condition of variable jacket water distribution ratio and variable electricity load. The results show that the energy efficiency and exergy efficiency of the system are the largest, 128.24% and 34.21% at the heating work condition respectively.

Preservation of in situ artefacts by local heating in earthen pit in archaeology museum in cold winter

The environmental requirements for the appropriate preservation of artefacts are usually inconsistent with those for visitors to archaeology museums. Independently controlling the environments for preservation of artefacts and visitors has proven to be an efficient and energy-saving strategy for archaeology museums displaying funerary relics in pits. However, although such systems, would control well the preservation environment in the summer, but could be inefficient in the winter due to buoyant warm air usually remains in the upper part of the room. In this study, we argue that temperature inversion is the key factor for sustaining a stable local environment in a funerary pit to preserve artefacts. A laboratory room with a total area of 100 m2 was constructed to simulate a large open exhibition hall. An experimental funerary pit with various heating, ventilating and air-conditioning (HVAC) systems including: a capillary radiant system, an air curtain system and an air conditioning system for human comfort; was built to determine appropriate environmental control strategy for preserving artefacts in the winter independent of the environment in the museum viewing gallery. A series of environmental control tests were conducted and each strategy was evaluated in terms of environmental stability for relic preservation in the pit and economic efficiency. The air curtain and capillary radiant coupled heating system was shown to be a feasible and energy-efficient strategy for the environment required for preservation of the historical relics.

Multiple absorption-related blow-up rates to a coupled heat system

This paper deals with asymptotic behavior of solutions to a heat system with absorptions and coupling positive multi-nonlinearities. It is known that although absorption mechanisms may affect such as blow-up criteria, blow-up time, and initial data required for blow-up solutions, they cannot change blow-up rates of solutions in general. It has been reported in the current literature that blow-up rates for scalar equations with absorptions are all absorption-independent. In a previous paper of the authors, four absorption-independent simultaneous blow-up rates were obtained already for the same problem under weak absorptions. The present paper will furthermore prove that if the absorptions are unbalanced in the model (i.e., the absorption is stronger for one component and weaker for another), then there are in addition eight possible absorption-related blow-up rates for the model, besides the four absorption-independent ones. This exposes a significant difference between scalar and coupled nonlinear parabolic equations with absorptions.

Multiple blow-up rates in a coupled heat system with mixed-type nonlinearities

This paper studies heat equations with inner absorptions and coupled boundary fluxes of mixed-type nonlinearities. At first, the critical exponent is obtained, and simply described via a characteristic algebraic system introduced by us. Then, as the main results of the paper, three blow-up rates are established under different dominations of nonlinearities for the one-dimensional case, and represented in another characteristic algebraic system. In particular, it is observed that unlike those in previous literature on parabolic models with absorptions, two of the multiple blow-up rates obtained here do depend on the absorption exponents. In the known works, the absorptions affect the blow-up criteria, the blow-up time, as well as the initial data required for the blow-up of solutions, all without changing the blow-up rates. To our knowledge, this is the first example of absorption-dependent blow-up rates, exploiting the significant interactions among diffusions, inner absorptions and nonlinear boundary fluxes in the coupled system. It is also proved that the blow-up of solutions in the model occurs on the boundary only.