In the United Kingdom, means of meeting domestic heating is being electrified to decarbonise in effort to reduce the greenhouse gases emissions from the burning of natural gas. Therefore, the uptake of heat pumps is o...In the United Kingdom, means of meeting domestic heating is being electrified to decarbonise in effort to reduce the greenhouse gases emissions from the burning of natural gas. Therefore, the uptake of heat pumps is on the increase. The operation and working principle of heat pumps must be well understood in the investigations of their impacts on the grid and the grid assets, especially distribution transformers which could be overloaded due to higher peak load demand. This work develops an operational model of heat pumps as combined space heating and domestic hot water provider implemented in MATLAB. The developed operational model of heat pumps is adaptable and repeatable for different input parameters. The developed model is used to generate daily average demand profiles of heat pumps for a typical winter weekday and a typical summer weekday. The generated demand profiles of heat pumps by the developed model compared well with the demand profiles of heat pumps generated from actual field projects which are usually expensive and time-tasking.展开更多
To further improve the utilization efficiency of solar energy and the performance of solar heat pump heating systems,a new heating mode of a solar air-source heat pump（SASHP）is proposed,and the characteristics and p...To further improve the utilization efficiency of solar energy and the performance of solar heat pump heating systems,a new heating mode of a solar air-source heat pump（SASHP）is proposed,and the characteristics and performance of the heat pump part of this new heating system are studied.Based on a SASHP with 10 kW,the mathematical model of this system is built,and the characteristics and performance are concluded from the simulation analysis at different environmental temperatures and output water temperatures.The results show that the performance of heat pumps can be greatly improved based on the new SASHP.When the environmental temperature is 7 ℃,the coefficient of performance（COP）of the air-source heat pump（ASHP）can be increased by 26% at most.This paper sets up a base for further study on the heating system with this new SASHP in the heating season.展开更多
In unconsolidated sandstone reservoirs,presence of numerous movable grains and a complex grain size composition necessitates a clear understanding of the physical clogging process for effective groundwater recharge in...In unconsolidated sandstone reservoirs,presence of numerous movable grains and a complex grain size composition necessitates a clear understanding of the physical clogging process for effective groundwater recharge in groundwater-source heat pump systems.To investigate this,a series of seepage experiments was conducted under in situ stress conditions using unconsolidated sandstone samples with varying grain compositions.The clogging phenomenon arises from the combined effects of grain migration and compaction,wherein the migration of both original and secondary crushed fine-grain particles blocks the seepage channels.Notably,grain composition influences the migration and transport properties of the grains.For samples composed of smaller grains,the apparent permeability demonstrates a transition from stability to decrease.In contrast,samples with larger grains experience a skip at the stability stage and directly enter the decrease stage,with a minor exception of a slight increase observed.Furthermore,a unique failure mode characterized by diameter shrinkage in the upper part of the sample is observed due to the combined effects of grain migration and in situ stress-induced compaction.These testing results contribute to a better understanding of the clogging mechanism caused by the coupled effects of grain migration and compaction during groundwater recharge in unconsolidated sandstone reservoirs used in groundwater-source heat pump systems.展开更多
The vapor recompression heat pump(VRHP) distillation technology offers significant improvements in energy efficiency for distillation systems with small temperature differences between the top and bottom of the column...The vapor recompression heat pump(VRHP) distillation technology offers significant improvements in energy efficiency for distillation systems with small temperature differences between the top and bottom of the column. However, the separation of wide-boiling binary mixtures leads to substantial temperature differences between the top and bottom of the column. This limits the applicability of conventional VRHP due to high capital costs and strict performance requirements of the compressor. To overcome these challenges and to accommodate compressor operating conditions, a novel synthesis and design method is introduced to integrate VRHPs with wide-boiling binary mixture distillation columns(WBMDCs). This method enables quick determination of an initial configuration for the integrated WBMDC-VRHP system and helps identify the optimum configuration with the minimum total annual cost. Two examples, namely the separation of benzene/toluene and isopropanol/chlorobenzene, are employed to derive optimum configurations of the WBMDC-VRHP and compare them with the WBMDC. A systematic comparison between the WBMDC-VRHP and WBMDC demonstrates the superior steady-state performance and economic efficiency of the WBMDC-VRHP.展开更多
With the implementation of electric energy alternatives,the large-scale application of electric energy substitution represented by air-source heat pumps has replaced traditional coal-fired heating,which is beneficial ...With the implementation of electric energy alternatives,the large-scale application of electric energy substitution represented by air-source heat pumps has replaced traditional coal-fired heating,which is beneficial for the environment and alleviates air pollution.However,the large-scale application of airsource heat pumps has brought power quality problems such as voltage sags,harmonic pollution,and three-phase imbalance to the distribution network.This paper studies the fixed-frequency and variablefrequency air-source heat pump,introduces its working principle,analyzes the mechanism of its power quality problem.Moreover,the paper establishes a simulation model for the fixed-frequency heat pump and variable-frequency heat pump to connect to the distribution network.This research mainly studies the impact of large-scale fixed-frequency heat pumps on the depth of voltage sags in the distribution network and the impact of large-scale variable-frequency heat pumps on the harmonic content of the distribution network under different penetration rates and uses measured data to verify the reliability of the simulation results.This paper uses experimental data for the first time to verify the real power quality problems of large-scale heat pumps,which can provide a reference for determining the power quality standards for heat pumps connected to the power grid.At the same time,it can also provide a reference for the power quality management of the distribution network that is actually connected to electric heating.展开更多
The conventional distillation is hard to accomplish the separation of acetonitrile/ethyl acetate/n-hexane mixture. Herein, a heterogeneous azeotropic distillation(HAD) without adding entrainer is proposed to separate ...The conventional distillation is hard to accomplish the separation of acetonitrile/ethyl acetate/n-hexane mixture. Herein, a heterogeneous azeotropic distillation(HAD) without adding entrainer is proposed to separate ternary mixture. The proposed scheme is optimized via the simulated annealing algorithm and minimum total annual cost(TAC) is used as objective functions. To minimize energy consumption,heat pump is added on the basis of optimal heterogeneous azeotropic distillation and heat integration technology is used to further improve the energy recovery. The TAC, gas emission, energy consumption and exergy destruction are used to discuss the economy and environmental protection of processes.Among all the processes, the heat pump with higher preheating temperature(HPT) assisted HAD process by combining with heat integration(HAD-HPT-HI) has best performances on economic, environment,energy and exergy. Compared with conventional HAD process, the HAD-HPT-HI achieves the reductions of 52.17%, 68.86%, 65.87% and 65.46% on TAC, total energy consumption, gas emissions and exergy destruction, respectively.展开更多
The electrification of building heating is an effective way to meet the global carbon target. As a clean and sustainable electrified heating technology, air-source heat pumps (ASHPs) are widely used in areas lacking c...The electrification of building heating is an effective way to meet the global carbon target. As a clean and sustainable electrified heating technology, air-source heat pumps (ASHPs) are widely used in areas lacking central heating. However, as a major component of space heating, heating terminals might not fit well with ASHP in order to achieve both intermittency and comfort. Therefore, this study proposes a novel radiation-adjustable heating terminal combined with an ASHP to achieve electrification, intermittency, and better thermal comfort. Radiant terminals currently suffer from three major problems: limited maximum heating capacity, inability to freely adapt, and difficulty with combining them with ASHPs. These problems were solved by improving the structural design of the novel terminal (Improvement A–E). Results showed that the maximum heating capacity increased by 23.6% and radiation heat transfer ratio from 10.1% to 30.9% was provided for users with the novel terminal. Further, new flat heat pipe (FHP) design improved stability (compressor oil return), intermittency (refrigerant thermal inertia), and safety (refrigerant leakage risk) by reducing the length of exposed refrigerant pipes. Furthermore, a new phased operation strategy was proposed for the novel terminal, and the adjustability of the terminal was improved. The results can be used as reference information for decarbonizing buildings by electrifying heating terminals.展开更多
To enhance system stability,solar collectors have been integrated with air-source heat pumps.This integration facilitates the concurrent utilization of solar and air as energy sources for the system,leading to an impr...To enhance system stability,solar collectors have been integrated with air-source heat pumps.This integration facilitates the concurrent utilization of solar and air as energy sources for the system,leading to an improvement in the system’s heat generation coefficient,overall efficiency,and stability.In this study,we focus on a residential building located in Lhasa as the target for heating purposes.Initially,we simulate and analyze a solar-air source heat pump combined heating system.Subsequently,while ensuring the system meets user requirements,we examine the influence of solar collector installation angles and collector area on the performance of the solar-air source heat pump dual heating system.Through this analysis,we determine the optimal installation angle and collector area to optimize system performance.展开更多
For heating systems based on electricity storage coupled with solar energy and an air source heat pump(ECSA),choosing the appropriate combination of heat sources according to local conditions is the key to improving e...For heating systems based on electricity storage coupled with solar energy and an air source heat pump(ECSA),choosing the appropriate combination of heat sources according to local conditions is the key to improving economic efficiency.In this paper,four cities in three climatic regions in China were selected,namely Nanjing in the hot summer and cold winter region,Tianjin in the cold region,Shenyang and Harbin in the severe cold winter region.The levelized cost of heat(LCOH)was used as the economic evaluation index,and the energy consumption and emissions of different pollutants were analyzed.TRNSYS software was used to simulate and analyze the system performance.The Hooke-Jeeves optimization algorithm and GenOpt software were used to optimize the system parameters.The results showed that ECSA systemhad an excellent operation effect in cold region and hot summer and cold winter region.Compared with ECS system,the systemenergy consumption,and the emission of different pollutants of ECSA system can be reduced by a maximum of 1.37 times.In cold region,the initial investment in an air source heat pump is higher due to the lower ambient temperature,resulting in an increase in the LOCH value of ECSA system.After the LOCH value of ECSA system in each region was optimized,the heating cost of the system was reduced,but also resulted in an increase in energy consumption and the emission of different pollutant gases.展开更多
A hybrid heat pump(compression/absorption)with an integrated thermal photovoltaic unit is studied.The considered working fluids are organic mixtures:R245fa/DMAC and R236fa/DMAC,chosen for their low Global Warming Pote...A hybrid heat pump(compression/absorption)with an integrated thermal photovoltaic unit is studied.The considered working fluids are organic mixtures:R245fa/DMAC and R236fa/DMAC,chosen for their low Global Warming Potential.The main objective is the optimization of energy efficiency in order to minimize the environmental impact through the implementation of a sustainable strategy.It is shown that Exergy Analysis itself is a valuable tool in energy integration.Within the imposed framework of minimizing total annual costs,entropy analysis can be instrumental in determining the optimal plant concept,optimizing energy conversion and use,and improving profitability.The present results are discussed under the optimistic hope that they may help to define new energy and environmental policies.展开更多
Process heating constitutes a significant share of final energy consumption in the industrial sector around the world.In this paper,a high-temperature heat pump(HTHP)using flash tank vapor injection technology(FTVI)is...Process heating constitutes a significant share of final energy consumption in the industrial sector around the world.In this paper,a high-temperature heat pump(HTHP)using flash tank vapor injection technology(FTVI)is proposed to develop low-temperature geothermal source for industrial process heating with temperature above 100°C.With heat sink output temperatures between 120°C and 150°C,the thermo-economic performance of the FTVI HTHP system using R1234ze(Z)as refrigerant is analyzed and also compared to the single-stage vapor compression(SSVC)system by employing the developed mathematical model.The coefficient of performance(COP),exergy efficiency(ηexe),net present value(NPV)and payback period(PBP)are used as performance indicators.The results show that under the typical working conditions,the COP andηexe of FTVI HTHP system are 3.00 and 59.66%,respectively,and the corresponding NPV and PBP reach 8.13×106 CNY and 4.13 years,respectively.Under the high-temperature heating conditions,the thermo-economic performance of the FTVI HTHP system is significantly better than that of the SSVC system,and the larger the temperature lift,the greater the thermo-economic advantage of the FTVI HTHP system.Additionally,the FTVI HTHP system is more capable than the SSVC system in absorbing the financial risks associated with changes of electricity price and natural gas price.展开更多
The screw air-source heat pump can cause incessant high noise levels during operation,which might hinder adoption of this energy-efficient heat pump.First,acoustic measurements and comparison testing were performed in...The screw air-source heat pump can cause incessant high noise levels during operation,which might hinder adoption of this energy-efficient heat pump.First,acoustic measurements and comparison testing were performed in this research.The measurements revealed that the compressor is the main noise source of the heat pump,and it shows a multipeak frequency distribution and a wide frequency spectrum under different work conditions,with multiple peaks at 63,250,and 1000 Hz.Then,a compressor sound insulation cover with broadband absorption was proposed,and it was experimentally proven that the insulation cover can reduce the maximum sound pressure level of one unit from 89.8 dBA to 79.1 dBA.Third,we proposed several noise reduction strategies and compared their noise reduction effects using computer simulation.The results showed that the noise problem can be effectively improved through the rational design of the sound barrier and the layout and opening options of heat pump.The distance between the sound barrier and heat pump and the sound attenuation due to diffraction ALa exhibit a U-shaped relation.For buildings of different heights,the optimal heights of noise barrier are proposed.The 5.5-meter is the optimal height of the sound barrier for single-story buildings.The conclusions can be applied to other building projects for heat pump noise reduction.展开更多
The paper deals with the impact of a mechanical compression heat pump, operated by electrical energy, on the environment. Irrespective of its origin and the history of its production, this energy pollutes the environm...The paper deals with the impact of a mechanical compression heat pump, operated by electrical energy, on the environment. Irrespective of its origin and the history of its production, this energy pollutes the environment as waste heat. The operational energy, obtained from the so-called alternative energy sources (wind, water energy), also burdens the environment as waste heat. This is not the case with the solar energy. A direct conversion of the Sun’s rays into electricity does not additionally affect the environment, compared to their direct conversion into heat without our intervention.展开更多
Photovoltaics,energy storage,direct current and flexibility(PEDF)are important pillars of achievement on the path to manufacturing nearly zero energy buildings(NZEBs).HVAC systems,which are an important part of public...Photovoltaics,energy storage,direct current and flexibility(PEDF)are important pillars of achievement on the path to manufacturing nearly zero energy buildings(NZEBs).HVAC systems,which are an important part of public buildings,play a key role in adapting to PDEF systems.This research studied the basic principles and operational control strategies of a DC inverter heat pump using a DC distribution network with the aim of contributing to the development and application of small DC distribution systems.Along with the characteristics of a DC distribution network and different operating conditions,a DC inverter heat pump has the ability to adapt to changes in the DC bus voltage and adds flexibility to the system.Theoretical models of the DC inverter heat pump integrated with an ice storage unit were developed.The control strategies of the DC inverter heat pump system considered the influence of both room temperature and varied bus voltage.A simulation study was conducted using MATLAB&Simulink software with simulation results validated by experimental data.The results showed that:(1)The bus fluctuation under the rated working voltage had little effect on the operation of the unit;(2)When the bus voltage was fluctuating from 80%-90%or 105%-107%,the heat pump could still operate normally by reducing the frequency;(3)When the bus voltage was less than 80%or more than 107%,the unit needed to be shut down for the sake of equipment safety,so that the energy storage device could adjust to the sharp decrease or rise of voltage.展开更多
This article gives an overview of using the ground source heat pump (GSHP) and air-to-water heat pump (A&WHP) in cold climate areas for heating and for domestic hot water production of buildings. Computer simulati...This article gives an overview of using the ground source heat pump (GSHP) and air-to-water heat pump (A&WHP) in cold climate areas for heating and for domestic hot water production of buildings. Computer simulation and analysis were carried out for a typical detached house, with 200 m2 of living area, the heat demand of 9 kW and the average heat demand for DHW production of 1 kW. In heating period the average Coefficient of Performance (COP) of the A&WHP is considerably lower than COP of the GSHP.展开更多
Meeting the climate change mitigation targets will require a substantial shift from fossil to clean fuels in the heating sector.Heat pumps with deep borehole exchangers are a promising solution to reduce emissions.Her...Meeting the climate change mitigation targets will require a substantial shift from fossil to clean fuels in the heating sector.Heat pumps with deep borehole exchangers are a promising solution to reduce emissions.Here the thermal behavior of deep borehole exchangers(DBHEs)ranging from 1 to 2 km was analyzed for various heat flow profiles.A strong correlation between thermal energy extraction and power output from DBHEs was found,also influenced by the heating profile employed.Longer operating time over the year typically resulted in higher energy production,while shorter one yielded higher average thermal power output,highlighting the importance of the choice of heating strategy and system design for optimal performance of DBHEs.Short breaks in operation for regenerating the borehole,for example,with waste heat,proved to be favorable for the performance yielding an overall heat output close to the same as with continuous extraction of heat.The results demonstrate the usefulness of deep boreholes for dense urban areas with less available space.As the heat production from a single DBHE in Finnish conditions ranges from half up to even a few GWh a year,the technology is best suitable for larger heat loads.展开更多
Data centers(DCs)are highly energy-intensive facilities,where about 30%–50%of the power consumed is attributable to the cooling of information technology equipment.This makes liquid cooling,especially in twophase mod...Data centers(DCs)are highly energy-intensive facilities,where about 30%–50%of the power consumed is attributable to the cooling of information technology equipment.This makes liquid cooling,especially in twophase mode,as an alternative to air cooling for the microprocessors in servers of interest.The need to meet the increased power density of server racks in high-performance DCs,along with the push towards lower global warming potential(GWP)refrigerants due to environmental concerns,has motivated research on the selection of two-phase heat transfer fluids for cooling servers while simultaneously recovering waste heat.With this regard,a heat pump-assisted absorption chiller(HPAAC)system for recovering waste heat in DCs with an on-chip twophase cooling loop driven by the compressor is proposed in the present paper and the low GWP hydrofluoroolefin refrigerants,including R1224yd(Z),R1233zd(E),R1234yf,R1234ze(E),R1234ze(Z),R1243zf and R1336mzz(Z),are evaluated and compared against R245fa as server coolant.For theHPAAC system,beginning with the development of energy and economic models,the performance is analyzed through both a parametric study and optimization using the coefficient of performance(COP),energy saving ratio(ESR),payback period(PBP)and net present value(NPV)as thermo-economic indicators.Using a standard vapor compression cooling system as a benchmark,the results indicate that with the evaporation temperature between 50℃and 70℃and the subcooling degree ranging from5℃to 15°C,R1233zd(E)with moderate compressor suction pressure and pressure ratio is the best refrigerant for the HPAAC systemwhile R1234yf performs the worst.More importantly,R1233zd(E)is also superior to R245fa based on thermo-economic performance,especially under work conditions with relatively lower evaporation temperature as well as subcooling degree.Under the given working conditions,the overall COP,ESR,NPV,and PBP of R1233zd(E)HPAAC with optimum subcooling degree range from4.99 to 11.27,25.53 to 64.59,1.13 to 4.10×10^(7) CNY and 5.77 to 2.22 years,respectively.Besides,the thermo-economic performance of R1233zd(E)HPAAC under optimum working conditions in terms of subcooling degree varying with the evaporation temperature is also investigated.展开更多
Low temperature heat adsorption pumps represent the innovative cooling systems, where cold is generated through adsorption/desorption cycle of water by a suitable adsorbent with good adsorption and high thermal conduc...Low temperature heat adsorption pumps represent the innovative cooling systems, where cold is generated through adsorption/desorption cycle of water by a suitable adsorbent with good adsorption and high thermal conductive properties. In this work, the hydrothermal synthesis of zeolite SAPO-34 on thermal conductive grapbitic supports, aiming at the development of highly pertbrming adsorbent materials, is reported. The synthesis was carried out using as-received and oxidized commercial carbon papers, and graphite plate. Composites were characterized by XRD, SEM and also by a thermogravimetric method, using a Cahn microbalance. The water adsorbing capacity showed typical S-shape trend and the maximum water loading was around 25 wt%, a value close to water adsorption capability of pure SAPO-34. These results are very promising for their application in heat adsorption pumps.展开更多
The renewable energy will play significant role in the world primary energy consumption in the future. Geothermal energy is immense with 5 000 EJ/a of technical potential, and geothermal heat pumps (GHPs) are one of t...The renewable energy will play significant role in the world primary energy consumption in the future. Geothermal energy is immense with 5 000 EJ/a of technical potential, and geothermal heat pumps (GHPs) are one of the fastest growing applications of renewable energy in the world with annual increases of 10 % and much faster in China. With high coefficient of performance (COP) up to 6, GHPs make efficiency of primary energy more than 240 % with assumed a 40 % of electricity generation efficiency, which means energy savings and CO2 emission reduction. In this paper,the geothermal resources and its utilization are talked about, and GHPs technology was introduced. Due to its high efficiency, there will be energy savings by using GHPs. There is also CO2 emission reduction because of using geothermal heat pumps, which is analyzed in the end.展开更多
In order to investigate the alternate operation characteristics of a solar-ground source heat pump system（SGSHPS）,various alternate operation modes are put forward and defined.A two-dimensional mathematical model wi...In order to investigate the alternate operation characteristics of a solar-ground source heat pump system（SGSHPS）,various alternate operation modes are put forward and defined.A two-dimensional mathematical model with freezing/melting phase changes is developed for the heat transfer analysis of the soil.Based on the numerical solution of the model,the variation trends of underground soil temperature of the SGSHPS operated in various alternate operation modes are discussed.The results indicate that,for the day-night and short-time interval alternate operation modes without solar energy,the operation time fraction of a solar heat source should be confined to from 50% to 58% when operated in an alternate period of 24 h.Meanwhile,the disadvantages of a natural resumption of soil temperature can be overcome effectively by solar energy filling,and an optimal operation effect can be achieved by integrating the mode of solar energy filling with other alternate modes.In addition,the accuracy of the presented model is verified by the experimental data of borehole wall temperatures.The conclusions can provide a reference for the optimization operation of the SGSHPS.展开更多
文摘In the United Kingdom, means of meeting domestic heating is being electrified to decarbonise in effort to reduce the greenhouse gases emissions from the burning of natural gas. Therefore, the uptake of heat pumps is on the increase. The operation and working principle of heat pumps must be well understood in the investigations of their impacts on the grid and the grid assets, especially distribution transformers which could be overloaded due to higher peak load demand. This work develops an operational model of heat pumps as combined space heating and domestic hot water provider implemented in MATLAB. The developed operational model of heat pumps is adaptable and repeatable for different input parameters. The developed model is used to generate daily average demand profiles of heat pumps for a typical winter weekday and a typical summer weekday. The generated demand profiles of heat pumps by the developed model compared well with the demand profiles of heat pumps generated from actual field projects which are usually expensive and time-tasking.
基金The National Natural Science Foundation of China(No.50676018)the National Key Technology R&D Program of China during the 11th Five-Year Plan Period(No.2008BAJ12B02)
文摘To further improve the utilization efficiency of solar energy and the performance of solar heat pump heating systems,a new heating mode of a solar air-source heat pump（SASHP）is proposed,and the characteristics and performance of the heat pump part of this new heating system are studied.Based on a SASHP with 10 kW,the mathematical model of this system is built,and the characteristics and performance are concluded from the simulation analysis at different environmental temperatures and output water temperatures.The results show that the performance of heat pumps can be greatly improved based on the new SASHP.When the environmental temperature is 7 ℃,the coefficient of performance（COP）of the air-source heat pump（ASHP）can be increased by 26% at most.This paper sets up a base for further study on the heating system with this new SASHP in the heating season.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFE0137200)National Natural Science Foundation of China(Grant Nos.52309147 and 52179114).
文摘In unconsolidated sandstone reservoirs,presence of numerous movable grains and a complex grain size composition necessitates a clear understanding of the physical clogging process for effective groundwater recharge in groundwater-source heat pump systems.To investigate this,a series of seepage experiments was conducted under in situ stress conditions using unconsolidated sandstone samples with varying grain compositions.The clogging phenomenon arises from the combined effects of grain migration and compaction,wherein the migration of both original and secondary crushed fine-grain particles blocks the seepage channels.Notably,grain composition influences the migration and transport properties of the grains.For samples composed of smaller grains,the apparent permeability demonstrates a transition from stability to decrease.In contrast,samples with larger grains experience a skip at the stability stage and directly enter the decrease stage,with a minor exception of a slight increase observed.Furthermore,a unique failure mode characterized by diameter shrinkage in the upper part of the sample is observed due to the combined effects of grain migration and in situ stress-induced compaction.These testing results contribute to a better understanding of the clogging mechanism caused by the coupled effects of grain migration and compaction during groundwater recharge in unconsolidated sandstone reservoirs used in groundwater-source heat pump systems.
文摘The vapor recompression heat pump(VRHP) distillation technology offers significant improvements in energy efficiency for distillation systems with small temperature differences between the top and bottom of the column. However, the separation of wide-boiling binary mixtures leads to substantial temperature differences between the top and bottom of the column. This limits the applicability of conventional VRHP due to high capital costs and strict performance requirements of the compressor. To overcome these challenges and to accommodate compressor operating conditions, a novel synthesis and design method is introduced to integrate VRHPs with wide-boiling binary mixture distillation columns(WBMDCs). This method enables quick determination of an initial configuration for the integrated WBMDC-VRHP system and helps identify the optimum configuration with the minimum total annual cost. Two examples, namely the separation of benzene/toluene and isopropanol/chlorobenzene, are employed to derive optimum configurations of the WBMDC-VRHP and compare them with the WBMDC. A systematic comparison between the WBMDC-VRHP and WBMDC demonstrates the superior steady-state performance and economic efficiency of the WBMDC-VRHP.
基金Science and Technology Project of State Grid Corporation of China,Scale application and benefit evaluation of typical power substitution technology considering the influence of power quality(52182018000H).
文摘With the implementation of electric energy alternatives,the large-scale application of electric energy substitution represented by air-source heat pumps has replaced traditional coal-fired heating,which is beneficial for the environment and alleviates air pollution.However,the large-scale application of airsource heat pumps has brought power quality problems such as voltage sags,harmonic pollution,and three-phase imbalance to the distribution network.This paper studies the fixed-frequency and variablefrequency air-source heat pump,introduces its working principle,analyzes the mechanism of its power quality problem.Moreover,the paper establishes a simulation model for the fixed-frequency heat pump and variable-frequency heat pump to connect to the distribution network.This research mainly studies the impact of large-scale fixed-frequency heat pumps on the depth of voltage sags in the distribution network and the impact of large-scale variable-frequency heat pumps on the harmonic content of the distribution network under different penetration rates and uses measured data to verify the reliability of the simulation results.This paper uses experimental data for the first time to verify the real power quality problems of large-scale heat pumps,which can provide a reference for determining the power quality standards for heat pumps connected to the power grid.At the same time,it can also provide a reference for the power quality management of the distribution network that is actually connected to electric heating.
基金financial support provided by the National Natural Science Foundation of China (22178030, 21878025, and 22078026)。
文摘The conventional distillation is hard to accomplish the separation of acetonitrile/ethyl acetate/n-hexane mixture. Herein, a heterogeneous azeotropic distillation(HAD) without adding entrainer is proposed to separate ternary mixture. The proposed scheme is optimized via the simulated annealing algorithm and minimum total annual cost(TAC) is used as objective functions. To minimize energy consumption,heat pump is added on the basis of optimal heterogeneous azeotropic distillation and heat integration technology is used to further improve the energy recovery. The TAC, gas emission, energy consumption and exergy destruction are used to discuss the economy and environmental protection of processes.Among all the processes, the heat pump with higher preheating temperature(HPT) assisted HAD process by combining with heat integration(HAD-HPT-HI) has best performances on economic, environment,energy and exergy. Compared with conventional HAD process, the HAD-HPT-HI achieves the reductions of 52.17%, 68.86%, 65.87% and 65.46% on TAC, total energy consumption, gas emissions and exergy destruction, respectively.
基金supported by the National Science Foundation for Distinguished Young Scholars of China(51825802).
文摘The electrification of building heating is an effective way to meet the global carbon target. As a clean and sustainable electrified heating technology, air-source heat pumps (ASHPs) are widely used in areas lacking central heating. However, as a major component of space heating, heating terminals might not fit well with ASHP in order to achieve both intermittency and comfort. Therefore, this study proposes a novel radiation-adjustable heating terminal combined with an ASHP to achieve electrification, intermittency, and better thermal comfort. Radiant terminals currently suffer from three major problems: limited maximum heating capacity, inability to freely adapt, and difficulty with combining them with ASHPs. These problems were solved by improving the structural design of the novel terminal (Improvement A–E). Results showed that the maximum heating capacity increased by 23.6% and radiation heat transfer ratio from 10.1% to 30.9% was provided for users with the novel terminal. Further, new flat heat pipe (FHP) design improved stability (compressor oil return), intermittency (refrigerant thermal inertia), and safety (refrigerant leakage risk) by reducing the length of exposed refrigerant pipes. Furthermore, a new phased operation strategy was proposed for the novel terminal, and the adjustability of the terminal was improved. The results can be used as reference information for decarbonizing buildings by electrifying heating terminals.
文摘To enhance system stability,solar collectors have been integrated with air-source heat pumps.This integration facilitates the concurrent utilization of solar and air as energy sources for the system,leading to an improvement in the system’s heat generation coefficient,overall efficiency,and stability.In this study,we focus on a residential building located in Lhasa as the target for heating purposes.Initially,we simulate and analyze a solar-air source heat pump combined heating system.Subsequently,while ensuring the system meets user requirements,we examine the influence of solar collector installation angles and collector area on the performance of the solar-air source heat pump dual heating system.Through this analysis,we determine the optimal installation angle and collector area to optimize system performance.
基金This work was supported by the National Key Research and Development Program of China(No.2019YFE0193200 KY202001)Science and Technology Planning Project of Beijing(No.Z201100008320001 KY191004).
文摘For heating systems based on electricity storage coupled with solar energy and an air source heat pump(ECSA),choosing the appropriate combination of heat sources according to local conditions is the key to improving economic efficiency.In this paper,four cities in three climatic regions in China were selected,namely Nanjing in the hot summer and cold winter region,Tianjin in the cold region,Shenyang and Harbin in the severe cold winter region.The levelized cost of heat(LCOH)was used as the economic evaluation index,and the energy consumption and emissions of different pollutants were analyzed.TRNSYS software was used to simulate and analyze the system performance.The Hooke-Jeeves optimization algorithm and GenOpt software were used to optimize the system parameters.The results showed that ECSA systemhad an excellent operation effect in cold region and hot summer and cold winter region.Compared with ECS system,the systemenergy consumption,and the emission of different pollutants of ECSA system can be reduced by a maximum of 1.37 times.In cold region,the initial investment in an air source heat pump is higher due to the lower ambient temperature,resulting in an increase in the LOCH value of ECSA system.After the LOCH value of ECSA system in each region was optimized,the heating cost of the system was reduced,but also resulted in an increase in energy consumption and the emission of different pollutant gases.
文摘A hybrid heat pump(compression/absorption)with an integrated thermal photovoltaic unit is studied.The considered working fluids are organic mixtures:R245fa/DMAC and R236fa/DMAC,chosen for their low Global Warming Potential.The main objective is the optimization of energy efficiency in order to minimize the environmental impact through the implementation of a sustainable strategy.It is shown that Exergy Analysis itself is a valuable tool in energy integration.Within the imposed framework of minimizing total annual costs,entropy analysis can be instrumental in determining the optimal plant concept,optimizing energy conversion and use,and improving profitability.The present results are discussed under the optimistic hope that they may help to define new energy and environmental policies.
基金supported by the Carbon Peak and Carbon Neutralization Science and Technology Innovation Special Fund of Jiangsu Province,China(No.BE2022859)Natural Science Foundation of Guangdong Province,China(No.2021A1515011763).
文摘Process heating constitutes a significant share of final energy consumption in the industrial sector around the world.In this paper,a high-temperature heat pump(HTHP)using flash tank vapor injection technology(FTVI)is proposed to develop low-temperature geothermal source for industrial process heating with temperature above 100°C.With heat sink output temperatures between 120°C and 150°C,the thermo-economic performance of the FTVI HTHP system using R1234ze(Z)as refrigerant is analyzed and also compared to the single-stage vapor compression(SSVC)system by employing the developed mathematical model.The coefficient of performance(COP),exergy efficiency(ηexe),net present value(NPV)and payback period(PBP)are used as performance indicators.The results show that under the typical working conditions,the COP andηexe of FTVI HTHP system are 3.00 and 59.66%,respectively,and the corresponding NPV and PBP reach 8.13×106 CNY and 4.13 years,respectively.Under the high-temperature heating conditions,the thermo-economic performance of the FTVI HTHP system is significantly better than that of the SSVC system,and the larger the temperature lift,the greater the thermo-economic advantage of the FTVI HTHP system.Additionally,the FTVI HTHP system is more capable than the SSVC system in absorbing the financial risks associated with changes of electricity price and natural gas price.
基金supported by the National Key R&D Program of China(No.2021YFB1507203)the National Natural Science Foundation of China(No.51838007).
文摘The screw air-source heat pump can cause incessant high noise levels during operation,which might hinder adoption of this energy-efficient heat pump.First,acoustic measurements and comparison testing were performed in this research.The measurements revealed that the compressor is the main noise source of the heat pump,and it shows a multipeak frequency distribution and a wide frequency spectrum under different work conditions,with multiple peaks at 63,250,and 1000 Hz.Then,a compressor sound insulation cover with broadband absorption was proposed,and it was experimentally proven that the insulation cover can reduce the maximum sound pressure level of one unit from 89.8 dBA to 79.1 dBA.Third,we proposed several noise reduction strategies and compared their noise reduction effects using computer simulation.The results showed that the noise problem can be effectively improved through the rational design of the sound barrier and the layout and opening options of heat pump.The distance between the sound barrier and heat pump and the sound attenuation due to diffraction ALa exhibit a U-shaped relation.For buildings of different heights,the optimal heights of noise barrier are proposed.The 5.5-meter is the optimal height of the sound barrier for single-story buildings.The conclusions can be applied to other building projects for heat pump noise reduction.
文摘The paper deals with the impact of a mechanical compression heat pump, operated by electrical energy, on the environment. Irrespective of its origin and the history of its production, this energy pollutes the environment as waste heat. The operational energy, obtained from the so-called alternative energy sources (wind, water energy), also burdens the environment as waste heat. This is not the case with the solar energy. A direct conversion of the Sun’s rays into electricity does not additionally affect the environment, compared to their direct conversion into heat without our intervention.
基金funded by State Grid Science&Technology Project“Research and Demonstration of Key Technologies on Electric-Heating Collaboration Cross-Network Mutual Supply for Typical Regional Clean Energy”,Grant Number 5400-202111575A-0-5-SF.
文摘Photovoltaics,energy storage,direct current and flexibility(PEDF)are important pillars of achievement on the path to manufacturing nearly zero energy buildings(NZEBs).HVAC systems,which are an important part of public buildings,play a key role in adapting to PDEF systems.This research studied the basic principles and operational control strategies of a DC inverter heat pump using a DC distribution network with the aim of contributing to the development and application of small DC distribution systems.Along with the characteristics of a DC distribution network and different operating conditions,a DC inverter heat pump has the ability to adapt to changes in the DC bus voltage and adds flexibility to the system.Theoretical models of the DC inverter heat pump integrated with an ice storage unit were developed.The control strategies of the DC inverter heat pump system considered the influence of both room temperature and varied bus voltage.A simulation study was conducted using MATLAB&Simulink software with simulation results validated by experimental data.The results showed that:(1)The bus fluctuation under the rated working voltage had little effect on the operation of the unit;(2)When the bus voltage was fluctuating from 80%-90%or 105%-107%,the heat pump could still operate normally by reducing the frequency;(3)When the bus voltage was less than 80%or more than 107%,the unit needed to be shut down for the sake of equipment safety,so that the energy storage device could adjust to the sharp decrease or rise of voltage.
基金supported by the Estonian Research Council,with Institutional research funding grant IUT1-15with the project“Development of efficient tech-nologies for air change and ventilation necessary for the increase of energy efficiency of buildings,AR12045”,financed by SA Archimedesby the project“Civil and Environmental Engineering PhD School,DAR9085”.
文摘This article gives an overview of using the ground source heat pump (GSHP) and air-to-water heat pump (A&WHP) in cold climate areas for heating and for domestic hot water production of buildings. Computer simulation and analysis were carried out for a typical detached house, with 200 m2 of living area, the heat demand of 9 kW and the average heat demand for DHW production of 1 kW. In heating period the average Coefficient of Performance (COP) of the A&WHP is considerably lower than COP of the GSHP.
文摘Meeting the climate change mitigation targets will require a substantial shift from fossil to clean fuels in the heating sector.Heat pumps with deep borehole exchangers are a promising solution to reduce emissions.Here the thermal behavior of deep borehole exchangers(DBHEs)ranging from 1 to 2 km was analyzed for various heat flow profiles.A strong correlation between thermal energy extraction and power output from DBHEs was found,also influenced by the heating profile employed.Longer operating time over the year typically resulted in higher energy production,while shorter one yielded higher average thermal power output,highlighting the importance of the choice of heating strategy and system design for optimal performance of DBHEs.Short breaks in operation for regenerating the borehole,for example,with waste heat,proved to be favorable for the performance yielding an overall heat output close to the same as with continuous extraction of heat.The results demonstrate the usefulness of deep boreholes for dense urban areas with less available space.As the heat production from a single DBHE in Finnish conditions ranges from half up to even a few GWh a year,the technology is best suitable for larger heat loads.
基金supported by the Key Science and Technology Project of China Southern Grid Co.,Ltd.(No.090000KK52220020).
文摘Data centers(DCs)are highly energy-intensive facilities,where about 30%–50%of the power consumed is attributable to the cooling of information technology equipment.This makes liquid cooling,especially in twophase mode,as an alternative to air cooling for the microprocessors in servers of interest.The need to meet the increased power density of server racks in high-performance DCs,along with the push towards lower global warming potential(GWP)refrigerants due to environmental concerns,has motivated research on the selection of two-phase heat transfer fluids for cooling servers while simultaneously recovering waste heat.With this regard,a heat pump-assisted absorption chiller(HPAAC)system for recovering waste heat in DCs with an on-chip twophase cooling loop driven by the compressor is proposed in the present paper and the low GWP hydrofluoroolefin refrigerants,including R1224yd(Z),R1233zd(E),R1234yf,R1234ze(E),R1234ze(Z),R1243zf and R1336mzz(Z),are evaluated and compared against R245fa as server coolant.For theHPAAC system,beginning with the development of energy and economic models,the performance is analyzed through both a parametric study and optimization using the coefficient of performance(COP),energy saving ratio(ESR),payback period(PBP)and net present value(NPV)as thermo-economic indicators.Using a standard vapor compression cooling system as a benchmark,the results indicate that with the evaporation temperature between 50℃and 70℃and the subcooling degree ranging from5℃to 15°C,R1233zd(E)with moderate compressor suction pressure and pressure ratio is the best refrigerant for the HPAAC systemwhile R1234yf performs the worst.More importantly,R1233zd(E)is also superior to R245fa based on thermo-economic performance,especially under work conditions with relatively lower evaporation temperature as well as subcooling degree.Under the given working conditions,the overall COP,ESR,NPV,and PBP of R1233zd(E)HPAAC with optimum subcooling degree range from4.99 to 11.27,25.53 to 64.59,1.13 to 4.10×10^(7) CNY and 5.77 to 2.22 years,respectively.Besides,the thermo-economic performance of R1233zd(E)HPAAC under optimum working conditions in terms of subcooling degree varying with the evaporation temperature is also investigated.
基金partially funded by "Fondo per la Ricerca per il Sistema Elettrico-AdP MSE-CNR"
文摘Low temperature heat adsorption pumps represent the innovative cooling systems, where cold is generated through adsorption/desorption cycle of water by a suitable adsorbent with good adsorption and high thermal conductive properties. In this work, the hydrothermal synthesis of zeolite SAPO-34 on thermal conductive grapbitic supports, aiming at the development of highly pertbrming adsorbent materials, is reported. The synthesis was carried out using as-received and oxidized commercial carbon papers, and graphite plate. Composites were characterized by XRD, SEM and also by a thermogravimetric method, using a Cahn microbalance. The water adsorbing capacity showed typical S-shape trend and the maximum water loading was around 25 wt%, a value close to water adsorption capability of pure SAPO-34. These results are very promising for their application in heat adsorption pumps.
文摘The renewable energy will play significant role in the world primary energy consumption in the future. Geothermal energy is immense with 5 000 EJ/a of technical potential, and geothermal heat pumps (GHPs) are one of the fastest growing applications of renewable energy in the world with annual increases of 10 % and much faster in China. With high coefficient of performance (COP) up to 6, GHPs make efficiency of primary energy more than 240 % with assumed a 40 % of electricity generation efficiency, which means energy savings and CO2 emission reduction. In this paper,the geothermal resources and its utilization are talked about, and GHPs technology was introduced. Due to its high efficiency, there will be energy savings by using GHPs. There is also CO2 emission reduction because of using geothermal heat pumps, which is analyzed in the end.
基金The National Key Technology R&D Program of Chinaduring the 11th Five-Year Plan Period(No.2008BAJ12B04)China Postdoctoral Science Foundation(No.20090461050)+1 种基金the Project of Researchand Development of Ministry of Housing and Urban-Rural Development ofChina(No.2008-K1-26)the New Century Talent Project of Yangzhou University for Excellent Young Backbone Teacher(2008)
文摘In order to investigate the alternate operation characteristics of a solar-ground source heat pump system（SGSHPS）,various alternate operation modes are put forward and defined.A two-dimensional mathematical model with freezing/melting phase changes is developed for the heat transfer analysis of the soil.Based on the numerical solution of the model,the variation trends of underground soil temperature of the SGSHPS operated in various alternate operation modes are discussed.The results indicate that,for the day-night and short-time interval alternate operation modes without solar energy,the operation time fraction of a solar heat source should be confined to from 50% to 58% when operated in an alternate period of 24 h.Meanwhile,the disadvantages of a natural resumption of soil temperature can be overcome effectively by solar energy filling,and an optimal operation effect can be achieved by integrating the mode of solar energy filling with other alternate modes.In addition,the accuracy of the presented model is verified by the experimental data of borehole wall temperatures.The conclusions can provide a reference for the optimization operation of the SGSHPS.
