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Natural gas depressurization at city gate stations can cause hydrate formation, necessitating preheating before pressure regulation. To reduce the high energy consumption of traditional city gate station preheating processes, this study introduces four novel multi-energy coupled systems: photovoltaic-air source heat pump (PV-ASHP), solar thermal-combined heat and power-ASHP (ST-CHP-ASHP), CHP-ASHP, and ASHP system, with a typical city gate station in Shanghai taken as the research case. Dynamic energy simulation systems were developed in Dymola software to evaluate the proposed systems from energy, environmental, and economic perspectives, conducting a comparison with conventional boiler preheating systems, including sensitivity analysis of energy prices on system economics. Results indicate PV-ASHP has the lowest annual total cost (ATC) and shortest discounted payback period, while ATC values for ST-CHP-ASHP, CHP-ASHP, and ASHP increase by 6.4 %, 9.6 %, and 12.6 %, respectively. ST-CHP-ASHP and PV-ASHP demonstrate advantages in primary energy rate and carbon emissions, with ST-CHP-ASHP performing slightly better than PV-ASHP. Currently, PV-ASHP demonstrates the highest development potential. If photovoltaic feed-in tariffs remain constant, and natural gas prices decrease by over 12.5 % or CHP feed-in tariffs increase by over 38.4 %, ST-CHP-ASHP becomes more economically viable. This research provides valuable insights for retrofitting China's existing city gate station preheating systems.

Energy conservation and emission reduction are critical global concerns, with infrared gas stoves recognized for their superior thermal efficiency and low emissions. However, research on infrared gas stoves with vertical ejectors, particularly those designed for use in horizontally constrained spaces, remains sparse. To bridge this gap, an experimental system is constructed to investigate the effects of perforated plate height, nozzle exit position (NXP), and heating height on stove performance. The experimental results reveal that gas uniformity is significantly influenced by the height of the perforated plate, while NXP has a lesser impact. The optimal height of the perforated plate is 12 mm, and the recommended value for NXP is −4 mm. With the heating height increasing from 15.0 mm to 36.5 mm, the thermal efficiency of the infrared gas stove decreases from 70.2 % to 59.3 %. The concentration of carbon monoxide in the flue gas initially declines sharply then gradually increases with the increase of heating height. Meanwhile, the concentration of nitrogen oxide exhibits slight fluctuations, with a mere 2 ppm difference between maximum and minimum values. Based on the results, a heating height of 19.3 mm is recommended. This study provides guidance for optimizing domestic gas stoves.

Utilization of gas engine-driven heat pumps (GEHP) can reduce the heavy loads on the power grid when electric heat pumps operate during the heating season. This study is to examine the performance of GEHP as a water heater with different engine speeds and water flow rates providing space-heating and sanitary hot water. When the engine speed rises from 1400 rpm to 1900 rpm, the temperature rise of water increases by 37% from 25.7 °C to 35.3 °C. Moreover, the system heat capacity rises from 71.8 kW to 97.7 kW with an increase of 36%, while the COP decreases from 3.6 to 3.0. As the inlet water flow rate an increase from 2.5 m3/h to 4.0 m3/h, the temperature rise decreases from 44.3 °C to 24.1 °C, with decreasing heat capacity from 128.8 kW to 112.1 kW. Additionally, the primary energy ratio (PER) initially increases from 1.46 to 1.50 at the engine speed of 1800 rpm, followed by a slight decrease to 1.48 when the engine speed reaches 1900 rpm. With an increasing water flow rate, the PER achieves its highest value of 1.64 at 3 m3/h and its lowest value of 1.49 at 3.5 m3/h.

Regenerative combustion technology has many advantages such as fuel saving, high combustion efficiency and low emission, and it has been widely used for large-scale furnaces. However, when regenerative combustion technology is adopted for small-scale furnaces, many technical problems occur. In this paper, a small-scale regenerative furnace with heat load of 70–80 kW and primary air coefficient of 1.00–1.60 was designed. It was found that the flame shifts from bright pale blue with faint rotating streamlines to yellowish transparent without apparent streamlines and to bright and transparent eventually. When main burners work stably, the temperature inside the furnace raises rapidly at first, and then the temperature increases steadily and fluctuates periodically. The highest temperature in the furnace can reach around 1300 °C. As the reversing time increases, the temperature fluctuation becomes more dramatically and the highest temperature is higher. NOx concentrations at all measurement points are below 50 ppm. Heat transfer efficiencies of each heat retainer show an increasing trend with the rise of the number of reversions. As reversing time increases, the heat transfer efficiency shows a decreasing trend.

With the increasingly stringent requirements for nitrogen oxide emissions, fully premixed water-cooled burners have been gradually discussed and studied due to their low cost and obvious effect on NOx reduction. However, their application in civil gas appliances is relatively rare, and there are few systematic studies combining experiments and simulations. In this paper, the experimental research and numerical simulation of the water-cooled burner are firstly carried out, and the accuracy of the numerical model is verified by the measured results. Then, the location and influencing factors of NOx generation are analyzed, and the direct factors affecting NOx generation in the water-cooled combustion technology are determined. The results show that the primary air coefficient is the main factor affecting the formation of NOx, the secondary air has little effect on the formation of NOx, and the premixed air temperature has little effect on it. The results have certain guiding significance for the design of water-cooled burners.

The application of gas engine driven heat pump (GHP) system can improve the peak valley difference of power and gas system and promote the low-carbon utilization of energy system. The energy consumption of GHP system in different types of buildings and especially the coefficient of performance (COP) under partial load rate needs more analysis. In this paper, according to the local meteorological parameters in Shanghai, the COP operation curve of GHP and electric driven heat pump (EHP) units under partial load rate was analyzed. Combined with the load calculation, the annual energy consumption of GHP and EHP units in different types of buildings, and the influence of energy price on economy of GHP system were analyzed. For office buildings and catering buildings, the energy consumption and operating costs of GHP system were slightly lower than those of EHP system, while for hotel buildings, the annual operating costs of GHP were lower than those of EHP only when the winter gas price was 2.39 yuan/m3 and the summer gas price was 2.19 yuan/m3. Therefore, in order to promote the market competitiveness of gas air conditioning, it is necessary to further refine the gas price or charge standard.

To study the effect of hydrogen-blended natural gas on the combustion stability and emission of domestic gas water heater, a test system is built in this paper, taking a unit of the partial premixed burner commonly used in water heaters as the object. Under the heat load of 0.7–2.3 kW, the changes of flame shape, burner temperature and pollutant emission of natural gas with hydrogen volume ratio of 0–40% are studied with independent control of primary air supply and mixing. The results show that: with the increase of hydrogen blending ratio, the inner flame height increases firstly and then reduces, while the change of burner temperature is opposite. The maximum inner flame height and the minimum temperature of the burner both appear at the hydrogen blending ratio of 10–20%. It can be seen that the limit of hydrogen blending ratio which can maintain the burner operate safely and stably under rated heat load is 40% through the maximum temperature distribution on the burner surface. The CO emission in the flue gas gradually decreases with the increase of hydrogen blending ratio, while the NOx emission fluctuates slightly when the hydrogen blending ratio is less than 20%, but then decreases gradually.

De-carbonization actions, represented by the electrification of end-use energy sources, have been strongly promoted, while space heating in residential buildings is an important aspect. In this paper, Jinan and Qingdao in northern China are selected to explore the challenges that electrification of heating will bring. The electricity demand for heating of different types of buildings is simulated, with the assumption that all heating loads are provided by electric heat pumps. Then the comparison of heating electricity demand with current electricity consumption in various social sectors has been analyzed to investigate the impact of the newly added electrical load on the power grid. The annual dynamic power supply under the currently installed wind turbines and photovoltaic modules is calculated to explore the interrelationship between the power supply potential of the available renewable energy and the heating electricity demand. The results show that the implementation of heating electrification will bring a strong impact on the existing grid, with photovoltaic generation almost negligible during the heating period and wind generation severely affected by intermittency. In the future, the deployment of installed renewable energy needs to continue to be promoted, while the layout of energy storage facilities needs to be strengthened.

Study Region: Three-River Source Region, Qinghai-Tibetan Plateau, China. Study Focus: Evapotranspiration (ET) is often the largest loss of water from grassland ecosystems and consists of two constituents: evaporation (E) and transpiration (T), but it is very difficult to separate E and T. In this study, we used an energy balance model (Shuttleworth-Wallace) and a water balance model (SOILWAT2) to estimate the water budget variables over a 10-year period (2007–2016) in a degraded alpine meadow in the Three-River Source Region on the Qinghai-Tibetan Plateau. New Hydrological Insights for the Region: The models produced contrasting patterns of precipitation and ET partitioning at the study site. Precipitation partitioning by SW2 resulted in substantial fluxes of both ET and deep drainage, while ET estimated by SW consumed almost all precipitation. ET was partitioned by the models into different annual E and T fluxes as well as different monthly and annual T/ET. Our study site located in an important water source region suggests that its water balance would contribute to drainage which aligns better with SW2 results. The surprising discrepancies between the models in the partitioning of precipitation into T, E, and deep drainage, however, is limiting our understanding and management of the degraded site and will require future work to reconcile.

The exhaust gas temperature of SOFC is as high as 600–1000 °C and contains combustible components that can be reused. In this paper, an experimental system was set up to study the combustion characteristics of SOFC simulated exhaust gas in a porous medium burner, the combustion of SOFC exhaust gas under different equivalence ratio, the effects of hydrogen concentration and water vapor fraction in the anode exhaust gas and the stable combustion limits of the burners had been analyzed. Results showed that: equivalence ratio and adiabatic flame temperature had a significant effect on the combustion, when the adiabatic flame temperature of mixed gas below 440 °C, or the water vapor content in the anode gas was greater than 85%, the flame couldn’t be stably burned; On the condition of the fuel utilization rate of 60% and the equivalence ratio of 0.40, the burner could burn stably with the inlet airflow velocity from 0.16 to 0.24m/s; The combustion stability limit of the exhaust gas burner varied with the utilization ratio of the stack, with increasing of fuel utilization ratio, the equivalence ratio of lifting and flashback limit was changing, and the adiabatic flame temperature of stable combustion limit had been studied.

The relationship between lifted flames and burner head temperature of partially premixed gas burners supplied by various natural gas sources was investigated, and the application of AGA(American Gas Association) lifting limit for Chinese domestic gas burners was studied. Results showed that lifted flames became more seriously with the burner head temperature decreasing, also with the increase of lift height of flames, it would lead to reduce the burner head temperature, eventually the burner head would reach the thermal equilibrium state which maintained stable flames and temperature. The lifting limit curve of partially premixed gas burners was only one under the same gas source, and it only depended on the burner structures and gas source characteristics, but nothing to do with the burner head temperature. The gas source with lower Wobbe index and calorific value made the burner appearing lifted flame more easily. Comparing with the experiment results and AGA lifting index prediction, it suggested that the limits of AGA lifting index IL≤ 1.10 should be change into IL≤ 1.05 using in China. Keywords: Partially premixed gas burners, Lifted flames, Natural gas, AGA lifting index

This document aims to assess the different performance of swirling strip-port and normal round-port domestic gas cookers with gas property fluctuation and propose suitable structure design parameter for both port types. Comparing with normal round-port gas cookers, swirling strip-port samples are not advantage on aspects of thermal efficiency and CO emission, but in term of NOx emission it performs very well which can effectively control NOx emission in a suitable range and improve gas cooker′s adaptive capacity, when natural gas is interchanged. It is easier to qualify CO emission with low NOx emission for swirling strip-port gas cookers, though it will sacrifice a part of thermal efficiency, while normal round-port gas cookers are easier to qualify CO emission with high thermal efficiency. The burner head design structure parameters of normal round-port gas cookers which can well adapt natural gas interchange are port thermal intensity in 7.2–8.4 W/mm2 and structure factor ε in 30–40, as well as swirling strip-port gas cookers are port thermal intensity in 8.0–11.5 W/mm2 with structure factor ε in 35–45. Keywords: Domestic gas cooker, Swirling strip-port, Normal round-port, Thermal efficiency, Emission, Natural gas interchange

Resistant starch (RS) is important in controlling diabetes. The primary objective of this study is to examine the impact of molecular conformation on the enzymatic hydrolysis efficiency of starch by α-amylase. And the interactions between starch molecules with different conformations and α-amylase were analysed by using molecule dynamics simulation and molecular docking. It was found, the natural conformational starch molecule was hydrolysed from the middle of the starch chain by α-amylase, producing polysaccharides. The bent PS-conformational starch molecules with multiple O 2 -O 3 intramolecular hydrogen bonds produced by high-pressure was hydrolysed from the head of the starch chain to produce glucose, which is not conducive to RS formation. The stretched H-conformation without intramolecular hydrogen bonds produced by heat treatment was not hydrolysed by α-amylase. However, it occupied the active groove and formed strong interactions with α-amylase, which prevented other starch molecules from binding to α-amylase, thus reducing hydrolysis efficiency. Moreover, the total interaction energies between the three starch molecules and α-amylase were approximately 78 kJ/mol. And several hydrogen bonds were formed between the starch molecules and α-amylase, which provides evidence for the continuous sliding hydrolysis hypothesis of α-amylase. Moreover, these results provide an important reference for elucidating the mechanism of RS formation., Competing Interests: Declaration of competing interest The authors declare no competing financial interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The effects of MgCl 2 and NaCl concentrations on potato starch were analysed. With an increase in MgCl 2 and NaCl concentrations from 0 to 4 mol/L, the gelatinisation properties, crystalline properties, and sedimentation rate of potato starch all showed a trend of rising first and then falling (or falling first and then rising). The inflection points of the effect trends were observed at 0.5 mol/L. This inflection point phenomenon was further analysed. At higher salt concentrations, starch granules were found to absorb external ions. These ions enhance the hydration of starch molecules and promote starch gelatinisation. When NaCl and MgCl 2 concentrations were increased from 0 to 4 mol/L, the starch hydration strength increased 52.09 and 65.41 times, respectively. At lower salt concentrations, the ions that naturally exist in starch granules seep out of the granules. The exudation of these ions may cause a certain degree of damage to the native structure of starch granules., Competing Interests: Declaration of competing interest We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled “The Effect Rules of MgCl2 and NaCl on the Properties of Potato Starch: The Inflection Point Phenomenon”., (Copyright © 2023 Elsevier B.V. All rights reserved.)

As a new starch gelatinization method, salt induced gelatinization can not only reduce energy consumption but also impart special physicochemical properties to starch gel. In this study, the process and mechanism of MgCl 2 induced starch gelatinization were explored. The results showed that, potato starch could be gelatinized after a treatment of 4 mol/L MgCl 2 for 3 h. The gelatinization started with the slight damage of outer shells, then the internal molecules leached out through the cracks or holes to form gel, finally the outer shells disintegrated. During the gelatinization process, the viscosity and granule size gradually increased after 0.5 h, while the original crystallinity disappeared rapidly in 0.5 h. Besides, MgCl 2 significantly increased the electrostatic interaction, then made starch molecules closer to each other and become denser, which may have close relationship with the appearance of the cracks and the disappearance of crystallization. Moreover, MgCl 2 enhanced the hydration and increased the binding free energy of starch molecules, then promoted starch gelatinization and accelerated the destruction of starch structure, which may be the critical factors of the starch gelatinization induced by MgCl 2 . The results will provide reference for the research and application of salt induced gelatinization., (Copyright © 2022 Elsevier B.V. All rights reserved.)