Waste heat generation,upgrading,and refrigeration are the fundamental ways to recover and utilize waste heat.Rationalizing the use of refrigerants also contributes to creating energy savings and minimizing carbon emis...Waste heat generation,upgrading,and refrigeration are the fundamental ways to recover and utilize waste heat.Rationalizing the use of refrigerants also contributes to creating energy savings and minimizing carbon emissions.This study evaluates the thermodynamics,economics,and environment of different refrigerants in three waste heat recovery schemes:generate electricity,heat pump,and refrigeration.Based on this,the entropy weight and technique for order preference by similarity to an ideal solution are combined to assess the overall performance of the refrigerants.A thorough analysis reveals that R1234ze(E)could replace R245fa and R123 in the organic Rankine cycle.The best refrigerant for vapor compression refrigeration and high-temperature heat pump systems is R1243zf.In addition,the multi-objective decision analysis shows that the performance difference among the nine selected refrigerants is the total cost,followed by the environmental impact.The approach successfully recognizes the variations between different refrigerants in the same waste heat recovery scheme and gives a thorough evaluation.It sets instructions for the future use of eco-friendly refrigerants and their application of waste heat recovery schemes.展开更多
To further enhance the recovery rate of low-temperature waste heat,the low-temperature flue gas in the sinter annular cooler was chosen as the heat source of an organic Rankine cycle(ORC)system,and the comprehensive e...To further enhance the recovery rate of low-temperature waste heat,the low-temperature flue gas in the sinter annular cooler was chosen as the heat source of an organic Rankine cycle(ORC)system,and the comprehensive evaluation of energy,exergy and economic performance of the ORC system was conducted deeply.The energy,exergy and economic performance models of the ORC system were established,and proper candidate organic working fluids(OWFs)were selected based on the thermo-physical properties of OWF and operating characteristics of ORC system.Then,the effects of ORC crucial parameters on the system energy,exergy and economic performances were evaluated in detail.Finally,the bi-objective optimization based on the genetic algorithm was conducted to analyze the optimal performance of the ORC system under the designed ORC crucial parameters,and the exergy efficiency and electricity production cost were set as the evaluation indexes of parametric optimization.The results indicate that the ORC system with the higher evaporation temperature and lower condensation temperature can obtain the larger system exergy efficiency and smaller electricity production cost.The smaller the superheat degree of OWF and pinch-point temperature difference in the evaporator are,the better the energy and exergy performances of the ORC system are.Under the optimization results,R245fa has the best comprehensive performance with the exergy efficiency of 46.34%and electricity production cost of 0.12123$/kWh among the selected candidate OWFs,which should be preferentially chosen as the OWF of the ORC system.展开更多
Heat Recovery Ventilators(HRVs)are essential for improving indoor air quality(IAQ)and reducing energy consumption in residential buildings situated in cold climates.This study considers the efficiency and performance ...Heat Recovery Ventilators(HRVs)are essential for improving indoor air quality(IAQ)and reducing energy consumption in residential buildings situated in cold climates.This study considers the efficiency and performance optimization of HRVs under cold climatic conditions,where conventional ventilation systems increase heat loss.A comprehensive numerical model was developed using COMSOL Multiphysics,integrating fluid dynamics,heat transfer,and solid mechanics to evaluate the thermal efficiency and structural integrity of an HRV system.The methodology employed a detailed geometry with tetrahedral elements,temperature-dependent material properties,and coupled governing equations solved under Tehran-specific boundary conditions.A multi-objective optimization was implemented in the framework of the Nelder-Mead simplex algorithm,targeting the maximization of the average outlet temperature and minimization of the maximum von Mises thermal stress,with inlet flow velocity as the design variable(range:0.5–1.2m/s).Results indicate an optimal velocity of 0.51563 m/s,achieving an average outlet temperature of 289.44 K and maximum von Mises stress of 221 MPa,validated through mesh independence and detailed contour analyses of temperature,velocity,and stress distributions.展开更多
Considering four different climate zones in China, an investigation on the choice of heat recovery ventilator for the buildings with little moisture emissions is carried out. The annual composition of energy consumpti...Considering four different climate zones in China, an investigation on the choice of heat recovery ventilator for the buildings with little moisture emissions is carried out. The annual composition of energy consumption of air intake for per unitary air ventilation flow rate is evaluated by employing the testing data of climatic parameters in eight selected cities. The analysis shows that the total heat recovery is suitable in a controlled ventilation system with air humidity controlled during heating period of all the climates. For the building without air humidity controlled in winter, the sensible heat recovery ventilators can be used in severe cold and cold regions, and total heat recovery systems are more suitable for energy saving in hot summer and cold winter and hot summer and warm winter regions.展开更多
In order to evaluate the heating performance of gas engine heat pump（GEHP） for air-conditioning and hot water supply, a test facility was developed and experiments were performed over a wide range of engine speed（1...In order to evaluate the heating performance of gas engine heat pump（GEHP） for air-conditioning and hot water supply, a test facility was developed and experiments were performed over a wide range of engine speed（1400-2600 r/min）, ambient air temperature（2.4-17.8 ℃） and condenser water inlet temperature（30-50℃）. The results show that as engine speed increases from 1400 r/min to 2600 r/min, the total heating capacity and energy consumption increase by about 30% and 89%, respectively; while the heat pump coefficient of performance（COP） and system primary energy ratio（PER） decrease by 44% and 31%, respectively. With the increase of ambient air temperature from 2.4 ℃ to 17.8 ℃, the heat pump COP and system PER increase by 32% and 19%, respectively. Moreover, the heat pump COP and system PER decrease by 27% and 15%, respectively, when the condenser water inlet temperature changes from 30 ℃ to 50 ℃. So, it is obvious that the effect of engine speed on the performance is more significant than the effects of ambient air temperature and condenser water inlet temperature.展开更多
In this paper, the research was focused on optimizing low-temperature heat recovery to adopt multi-effect distil- lation （MED） in desalination by pinch technology. And further analysis indicated that phase changes o...In this paper, the research was focused on optimizing low-temperature heat recovery to adopt multi-effect distil- lation （MED） in desalination by pinch technology. And further analysis indicated that phase changes occurred during the heat recovery process. In such case, the feed stream was divided into two streams： the liquid feed stream and the gaseous feed stream. Through calculation, the optimal ATmin was established at 26℃, and the total cost of heat exchange process was only $1.098× 106. By using the Problem Table Algorithm for pinch analysis, the temperature of the hot and the cold steams was 119℃ and 93 ℃, respectively. At a temperature higher than 119 ℃, all heat of the hot stream could not be cooled by the condenser, and the minimum heat load of utility （QH.min） was 440457.64 kW; and at a temperature below 93 ℃, all heat of the cold stream could not be provided by the heater, and the minimum cold load of utility （QC.min） was 1965993.85 kW. Finally, the synthesis of heat exchanger network was established through integrating two heat exchanger networks.展开更多
Underground mines in Arctic and Subarctic regions require the preheating of mine intake air during winter.The cold fresh air of those remote areas can be as severe as40℃ and commonly needs to be heated to around+3℃...Underground mines in Arctic and Subarctic regions require the preheating of mine intake air during winter.The cold fresh air of those remote areas can be as severe as40℃ and commonly needs to be heated to around+3℃.This extensive amount of heating is usually provided by employing large-size air heaters,fueled by diesel,propane,natural gas,or heavy oil,leading to high energy costs and large carbon footprints.At the same time,the thermal energy content of a diesel generator sets(gen-sets)exhaust is known to be one-third of the total heating value of its combusted fuel.Exhaust heat recovery from diesel gen-sets is a growing technology that seeks to mitigate the energy costs by capturing and redirecting this commonly rejected exhaust heat to other applications such as space heating or pre-heating of the mine intake air.The present study investigated the possibility of employing a simple system based on off-theshelf heat exchanger technology,which can recover the waste heat from the exhaust of the power generation units(diesel gen-sets)in an off-grid,cold,remote mine in Canada for heating of the mine intake air.Data from a real mine was used for the analysis along with environmental data of three different location-scenarios with distinct climates.After developing a thermodynamic model,the heat savings were calculated,and an economic feasibility evaluation was performed.The proposed system was found highly viable with annual savings of up to C$6.7 million and capable enough to provide an average of around 75%of the heating demand for mine intake air,leading to a payback period of about eleven months or less for all scenarios.Deployment of seasonal thermal energy storage has also been recommended to mitigate the mismatch between supply and demand,mainly in summertime,possibly allowing the system to eliminate fuel costs for intake air heating.展开更多
A bottoming cycle system based on CO2 Brayton cycle is proposed to recover the engine exhaust heat. Its performance is compared with the conventional air Brayton cycle under five typical engine conditions. The results...A bottoming cycle system based on CO2 Brayton cycle is proposed to recover the engine exhaust heat. Its performance is compared with the conventional air Brayton cycle under five typical engine conditions. The results show that CO2 Brayton cycle proves to be superior to the air Brayton cycle in terms of the system net output power, thermal efficiency and recovery efficiency. In most cases, the recovery efficiency of CO2 Brayton cycle can be higher than 9% and the system has a better performance at the engine＇s high operating load, The thermal efficiency can be as large as 24.83% under 100% olaerating load, accordingly, the net outnut nower of 14.86 kW in nhtnined展开更多
The burning of fossil fuels in industry results in significant carbon emissions,and the heat generated is often not fully utilized.For high-temperature industries,thermophotovoltaics(TPVs)is an effective method for wa...The burning of fossil fuels in industry results in significant carbon emissions,and the heat generated is often not fully utilized.For high-temperature industries,thermophotovoltaics(TPVs)is an effective method for waste heat recovery.This review covers two aspects of high-efficiency TPV systems and industrial waste heat applications.At the system level,representative results of TPV complete the systems,while selective emitters and photovoltaic cells in the last decade are compiled.The key points of components to improve the energy conversion efficiency are further analyzed,and the related micro/nano-fabrication methods are introduced.At the application level,the feasibility of TPV applications in high-temperature industries is shown from the world waste heat utilization situation.The potential of TPV in waste heat recovery and carbon neutrality is illustrated with the steel industry as an example.展开更多
Waste heat recovery from hot steel slag was determined in a granular bed through the combination of numerical simulation and an industrial test method.First,the effective thermal conductivity of the granular bed was c...Waste heat recovery from hot steel slag was determined in a granular bed through the combination of numerical simulation and an industrial test method.First,the effective thermal conductivity of the granular bed was calculated.Then,the unsteady-state model was used to simulate the heat recovery under three different flow fields(O-type,S-type,and nonshielding type(Nontype)).Second,the simulation results were validated by in-situ industrial experiments.The two methods confirmed that the heat recovery efficiencies of the flow fields from high to low followed the order of Nontype,S-type,and O-type.Finally,heat recovery was carried out under the Nontype flow field in an industrial test.The heat recovery efficiency increased from~76%and~78%to~81%when the steel slag thickness decreased from 400 and 300 to 200 mm,corresponding to reductions in the steel slag mass from 3.96 and 2.97 to 1.98 t with a blower air volume of 14687 m^(3)/h.Therefore,the research results showed that numerical simulation can not only guide experiments on waste heat recovery but also optimize the flow field.Most importantly,the method proposed in this paper has achieved higher waste heat recovery from hot steel slag in industrial scale.展开更多
An exhaust heat recovery generator is proposed to be integrated with conventional gas-fired triple-effect LiBr/water absorption cooling cycles to improve system energy efficiency. As a case study, simulation of the no...An exhaust heat recovery generator is proposed to be integrated with conventional gas-fired triple-effect LiBr/water absorption cooling cycles to improve system energy efficiency. As a case study, simulation of the novel cycle based on promising parallel flow with cooling capacity of 1 150 kW is carried out under various heat recovery generator vapor production ratios ranging from 0 to 3.5%. The life cycle saving economic analysis, for which the annual gas conservation is estimated with Bin method, is employed to prove the worthiness of extra expenditure. Results show that the optimum gas saving revenue is obtained at 2.8% heat recovery generator vapor production ratio with 42 kW exhaust heat recovered, and the system energy efficiency is improved from 1.78 to 1.83. The initial investment of exchanger can be paid back within 7 years and 9 000 CNY of gas saving revenue will be achieved over the 15-year life cycle of the machine. This technology can be easily implemented and present desirable economic effects, which is feasible to the development of triple-effect absorption cycles.展开更多
Dynamic performance is important to the controlling and monitoring of the organic Rankine cycle(ORC) system so to avoid the occurrence of unwanted conditions. A small scale waste heat recovery system with organic Rank...Dynamic performance is important to the controlling and monitoring of the organic Rankine cycle(ORC) system so to avoid the occurrence of unwanted conditions. A small scale waste heat recovery system with organic Rankine cycle was constructed and the dynamic behavior was presented. In the dynamic test, the pump was stopped and then started. In addition, there was a step change of the flue gas volume flow rate and the converter frequency of multistage pump, respectively. The results indicate that the working fluid flow rate has the shortest response time, followed by the expander inlet pressure and the expander inlet temperature.The operation frequency of pump is a key parameter for the ORC system. Due to a step change of pump frequency(39.49-35.24 Hz),the expander efficiency and thermal efficiency drop by 16% and 21% within 2 min, respectively. Besides, the saturated mixture can lead to an increase of the expander rotation speed.展开更多
Ground-coupled heat pumps(GCHP)are commonly used in residential heating system.To mitigate the boreholes temperature dropping with operating time,a new exhaust-air recharging system is developed.The new recharging sys...Ground-coupled heat pumps(GCHP)are commonly used in residential heating system.To mitigate the boreholes temperature dropping with operating time,a new exhaust-air recharging system is developed.The new recharging system can be used in three operational modes.In this paper,a ground-coupled heat recovery ventilation(HRV)model is discussed.A thermal model is set up to find the optimal brine flow rate and heat transfer allocation ratio between exhaust and supply coils for maximum heat recovery efficiency.Contrary to the conventional liquid-loop HRV systems,the brine temperature entering the exhaust coil never goes blow zero(0℃),and hence defrosting is needless in the ground-coupled HRV system.This can make the ground-coupled HRV system over 20% more efficient than a conventional HRV system at low outdoor temperatures.展开更多
Thermoelectric generators(TEGs)are considered promising devices for waste heat recovery from various systems.The Seebeck effect can be utilized to generate power using the residual heat emitted by the filter dryer rec...Thermoelectric generators(TEGs)are considered promising devices for waste heat recovery from various systems.The Seebeck effect can be utilized to generate power using the residual heat emitted by the filter dryer receiver(FDR)of an air conditioning(A/C)system,which would otherwise go to waste.The study aims to build a set of thermoelectric generators(TEG)to collect the waste heat of the FDR and generate low-power electricity.A novel electrical circuit with two transformers is designed and fabricated to produce a more stable voltage for operation and charging.The thermoelectric generator(TEGs)was installed on the FDR of the A/C unit.The test showed that climate conditions have a significant impact on the output power generated from the system.The results showed that the peak voltage recorded in the current study is 5.2 V per day(wet,cold,and wind weather)with an output power of 0.2 W.These values are acceptable for powering the load and charging a single battery with 3.5 V as the voltage increases battery 0.1 V/20 min charge.A case study of operating the emergency signs in a building was considered.The current heat recovery system is deemed to be easily installed and can be connected to a network of TEGs to produce more power.展开更多
This study explores the potentials of employing an Organic Rankine Cycle (ORC) system with variable inlet guide vanes (VIV) turbine geometry designed on a GT-Suite platform for effective exhaust heat recovery (EHR) ap...This study explores the potentials of employing an Organic Rankine Cycle (ORC) system with variable inlet guide vanes (VIV) turbine geometry designed on a GT-Suite platform for effective exhaust heat recovery (EHR) application onboard passenger vehicles. The ORC model simulation was based on vehicle speed mode using R245fa as working fluid to assess the thermal performance of the ORC system when utilizing modified turbine geometry. Interestingly, the model achieved a very improved performance in contrast to the model without a modified turbine configuration. The results revealed the average 2.32 kW ORC net output, 4.93% thermal efficiency, 6.1% mechanical efficiency, and 5.0% improved brake specific fuel consumption (BSFC) for the developed model. As determined by the performance indicators, these promising results from the model study show the prospect of EHR technology application in the transportation sector for reduction in exhaust emissions and fuel savings.展开更多
Drum level sloshing is the latest discovery in the application of heat recovery steam generator (HRSG) in combined cycle, and shows certain negative influence on drum level controlling. In order to improve drum level ...Drum level sloshing is the latest discovery in the application of heat recovery steam generator (HRSG) in combined cycle, and shows certain negative influence on drum level controlling. In order to improve drum level controlling, influence factors on the drum level sloshing were investigated. Firstly, drum sub-modules were developed using the method of modularization modeling, and then the model of drum level sloshing was set up as well. Experiments were carried out on the experimental rig, and the model was validated using the obtained experimental results. Dynamic simulation was made based on the model to get a 3-D graph of drum level sloshing, which shows a vivid procedure of drum level sloshing. The effect of feed-water flow rate, main-steam flow rate and heating quantity on the drum level sloshing was analyzed. The simulation results indicate that the signals with frequency higher than 0.05 Hz are that of drum level sloshing, the signals with frequency of 0.0-0.05 Hz are that of drum level trendy and "false water level", and variation of the feed-water flow rates, main-steam flow rates and heating quantities can change the frequency of drum level sloshing, i.e., the frequency of sloshing increases with the increase of feed-water flow rate, or the decrease of the main-steam flow rate and the heating quantity. This research work is fundamental to improve signal-to-noise ratio of drum level signal and precise controlling of drum level.展开更多
In order to improve the recovery and utilization rates of sinter waste heat effectively,the organic Rankine cycle(ORC)system with subcritical cycle was designed to recover the low-temperature sinter cooling flue gas w...In order to improve the recovery and utilization rates of sinter waste heat effectively,the organic Rankine cycle(ORC)system with subcritical cycle was designed to recover the low-temperature sinter cooling flue gas waste heat in an annular cooler for power generation.The thermodynamic,economic and multi-objective optimization models of ORC system were established,and R600a was selected as the ORC working medium.Subsequently,the variations in system thermodynamic performance and economic performance with the ORC thermal parameters were discussed in detail,and the optimal ORC thermal parameters were determined.The results show that the system net output power increases with increasing the evaporation temperature and decreasing the condensation temperature and increases first and then,decreases with the increase in superheat degree for a given flue gas outlet temperature in the evaporator,while the heat transfer area per unit net output power appears different variation trends in various ranges of flue gas outlet temperature.Taking the sinter cooling flue gas waste heat of 160℃as the ORC heat source,the optimal thermal parameters of ORC system were the flue gas outlet temperature of 90℃,the evaporation temperature of 95℃,the superheat degree of 10℃,and the condensation temperature of 28℃.展开更多
In present,the wet-based pattern is mainly adopted to deal with the steel slag by steel plant at home and abroad,the wet-based technology has some defects;Wasting of water,pollution of the environment,and the slag has...In present,the wet-based pattern is mainly adopted to deal with the steel slag by steel plant at home and abroad,the wet-based technology has some defects;Wasting of water,pollution of the environment,and the slag has not been fully recycled.This paper presents a new method,which is aimed to realize dry granulation,waste heat recovery and comprehensive utilizing the steel slag.According to the ideas of wind quenching granulation,the heating slag from the converter furnace,was bring to the granulation heat exchange system,through the process of breaking in a container,the granulation heat exchange system has the functions of feeding continuously and heat exchange.The heat air,through the diversion tubes,could be recycled in removing the dust.The granulation slag could be bring to a confined roller,granulating and cooling secondarily.The roller export was connected to a magnetic separator.The separated iron could be recycled,and the remaining slag could also be reused as building materials,in process of stabilization and secondary magnetic separation.The heated air could be guided into the boiler to generate the steam,which can be used to generate electricity,or use as cleaned energy,realizing the target to recycle the waste heat in steel slag.The highlights of the new method are dry granulation and waste heat recovery.This paper states the process of heat exchange between the air and the steel slag in the system of granulation heat exchange in the new technical process.In theory,it has been proved reasonable with the the system of granulation heat exchange,and also the work conditions has been optimized.展开更多
The building energy consumption is an important part among the total society energy consumption,in which the energy consumption for air conditioning occupies almost 70%.The energy consumption of the air conditioning s...The building energy consumption is an important part among the total society energy consumption,in which the energy consumption for air conditioning occupies almost 70%.The energy consumption of the air conditioning system for fresh air handling can be saved effectively when the exhaust air energy could be recovered to preheat or precool the fresh air.Considering the install locations requirements on field,the pump-driven heat pipes(PHP)were developed as heat recovery ventilators(HRVs)and used in an existing experiment building in Beijing Urban.The thermal performance of the PHP HRVs was tested in real operation time periods under winter running mode.Both the power and heat consumption of the modular air handling units with and without HRVs were monitored and obtained,as well as the hourly power and heat consumption.The energy savings of HRVs were analyzed.The results indicate that the PHP HRVs can work steadily and meet the energy recovery need well.The temperature effectiveness of the HRVs can be kept from 60%to 70%.The test total energy saving rate was 24.48%,and the average hourly heat consumption reduced by 28.54%.The daily energy consumption can be saved by 118 kWh,and the energy savings can reach to 9440 kWh for a whole winter.展开更多
Concentrating Solar Power(CSP)plants offer a promising way to generate low-emission energy.However,these plants face challenges such as reduced sunlight during winter and cloudy days,despite being located in high sola...Concentrating Solar Power(CSP)plants offer a promising way to generate low-emission energy.However,these plants face challenges such as reduced sunlight during winter and cloudy days,despite being located in high solar radiation areas.Furthermore,their dispatch capacities and yields can be affected by high electricity consumption,particularly at night.The present work aims to develop an off-design model that evaluates the hourly and annual performances of a parabolic trough power plant(PTPP)equipped with a waste heat recovery system.The study aims to compare the performances of this new layout with those of the conventional Andasol 1 plant,with the aim of assessing the improvements achieved in the new design.Based on the results,it can be concluded that the new layout has increased the annual generated power to almost 183 GWh(an increase of about 7.60% is achieved compared to the Andasol 1 layout that generates 169 GWh annually).Additionally,the proposed installation has achieved an efficiency of 20.55%,which represents a 7.87% increase compared to the previous design(19.05%).The Levelized Cost of Electricity(LCOE)of the new layout has been reduced by more than 5.8% compared to the Andasol 1 plant.Specifically,it has decreased from 13.11 to 12.35 c/kWh.This reduction in LCOE highlights the improved cost-effectiveness of the newlayout,making it amore economically viable option for generating electricity compared to the conventional Andasol 1 plant.展开更多
基金supported by the National Natural Science Foundation of China(22178190)the National Youth Natural Science Foundation of China(22408195).
文摘Waste heat generation,upgrading,and refrigeration are the fundamental ways to recover and utilize waste heat.Rationalizing the use of refrigerants also contributes to creating energy savings and minimizing carbon emissions.This study evaluates the thermodynamics,economics,and environment of different refrigerants in three waste heat recovery schemes:generate electricity,heat pump,and refrigeration.Based on this,the entropy weight and technique for order preference by similarity to an ideal solution are combined to assess the overall performance of the refrigerants.A thorough analysis reveals that R1234ze(E)could replace R245fa and R123 in the organic Rankine cycle.The best refrigerant for vapor compression refrigeration and high-temperature heat pump systems is R1243zf.In addition,the multi-objective decision analysis shows that the performance difference among the nine selected refrigerants is the total cost,followed by the environmental impact.The approach successfully recognizes the variations between different refrigerants in the same waste heat recovery scheme and gives a thorough evaluation.It sets instructions for the future use of eco-friendly refrigerants and their application of waste heat recovery schemes.
基金the financial support for this work provided by the National Natural Science Foundation of China(51974087)Anhui Provincial Natural Science Foundation(1908085QE203)+1 种基金University Natural Science Research Foundation of Anhui Province(2022AH050262)Science Research Foundation of Anhui Jianzhu University(2020QDZ02).
文摘To further enhance the recovery rate of low-temperature waste heat,the low-temperature flue gas in the sinter annular cooler was chosen as the heat source of an organic Rankine cycle(ORC)system,and the comprehensive evaluation of energy,exergy and economic performance of the ORC system was conducted deeply.The energy,exergy and economic performance models of the ORC system were established,and proper candidate organic working fluids(OWFs)were selected based on the thermo-physical properties of OWF and operating characteristics of ORC system.Then,the effects of ORC crucial parameters on the system energy,exergy and economic performances were evaluated in detail.Finally,the bi-objective optimization based on the genetic algorithm was conducted to analyze the optimal performance of the ORC system under the designed ORC crucial parameters,and the exergy efficiency and electricity production cost were set as the evaluation indexes of parametric optimization.The results indicate that the ORC system with the higher evaporation temperature and lower condensation temperature can obtain the larger system exergy efficiency and smaller electricity production cost.The smaller the superheat degree of OWF and pinch-point temperature difference in the evaporator are,the better the energy and exergy performances of the ORC system are.Under the optimization results,R245fa has the best comprehensive performance with the exergy efficiency of 46.34%and electricity production cost of 0.12123$/kWh among the selected candidate OWFs,which should be preferentially chosen as the OWF of the ORC system.
文摘Heat Recovery Ventilators(HRVs)are essential for improving indoor air quality(IAQ)and reducing energy consumption in residential buildings situated in cold climates.This study considers the efficiency and performance optimization of HRVs under cold climatic conditions,where conventional ventilation systems increase heat loss.A comprehensive numerical model was developed using COMSOL Multiphysics,integrating fluid dynamics,heat transfer,and solid mechanics to evaluate the thermal efficiency and structural integrity of an HRV system.The methodology employed a detailed geometry with tetrahedral elements,temperature-dependent material properties,and coupled governing equations solved under Tehran-specific boundary conditions.A multi-objective optimization was implemented in the framework of the Nelder-Mead simplex algorithm,targeting the maximization of the average outlet temperature and minimization of the maximum von Mises thermal stress,with inlet flow velocity as the design variable(range:0.5–1.2m/s).Results indicate an optimal velocity of 0.51563 m/s,achieving an average outlet temperature of 289.44 K and maximum von Mises stress of 221 MPa,validated through mesh independence and detailed contour analyses of temperature,velocity,and stress distributions.
基金National Natural Science Foundation of China(Grant No50578034)Shanghai Educational Development Foundationtitled"Shuguang Project"(Grant NO03SG30)
文摘Considering four different climate zones in China, an investigation on the choice of heat recovery ventilator for the buildings with little moisture emissions is carried out. The annual composition of energy consumption of air intake for per unitary air ventilation flow rate is evaluated by employing the testing data of climatic parameters in eight selected cities. The analysis shows that the total heat recovery is suitable in a controlled ventilation system with air humidity controlled during heating period of all the climates. For the building without air humidity controlled in winter, the sensible heat recovery ventilators can be used in severe cold and cold regions, and total heat recovery systems are more suitable for energy saving in hot summer and cold winter and hot summer and warm winter regions.
基金Project(hx2013-87)supported by the Qingdao Economic and Technology Development Zone Haier Water-Heater Co.Ltd.,China
文摘In order to evaluate the heating performance of gas engine heat pump（GEHP） for air-conditioning and hot water supply, a test facility was developed and experiments were performed over a wide range of engine speed（1400-2600 r/min）, ambient air temperature（2.4-17.8 ℃） and condenser water inlet temperature（30-50℃）. The results show that as engine speed increases from 1400 r/min to 2600 r/min, the total heating capacity and energy consumption increase by about 30% and 89%, respectively; while the heat pump coefficient of performance（COP） and system primary energy ratio（PER） decrease by 44% and 31%, respectively. With the increase of ambient air temperature from 2.4 ℃ to 17.8 ℃, the heat pump COP and system PER increase by 32% and 19%, respectively. Moreover, the heat pump COP and system PER decrease by 27% and 15%, respectively, when the condenser water inlet temperature changes from 30 ℃ to 50 ℃. So, it is obvious that the effect of engine speed on the performance is more significant than the effects of ambient air temperature and condenser water inlet temperature.
基金the National Nature Science Foundation (Grant No. 51178463)
文摘In this paper, the research was focused on optimizing low-temperature heat recovery to adopt multi-effect distil- lation （MED） in desalination by pinch technology. And further analysis indicated that phase changes occurred during the heat recovery process. In such case, the feed stream was divided into two streams： the liquid feed stream and the gaseous feed stream. Through calculation, the optimal ATmin was established at 26℃, and the total cost of heat exchange process was only $1.098× 106. By using the Problem Table Algorithm for pinch analysis, the temperature of the hot and the cold steams was 119℃ and 93 ℃, respectively. At a temperature higher than 119 ℃, all heat of the hot stream could not be cooled by the condenser, and the minimum heat load of utility （QH.min） was 440457.64 kW; and at a temperature below 93 ℃, all heat of the cold stream could not be provided by the heater, and the minimum cold load of utility （QC.min） was 1965993.85 kW. Finally, the synthesis of heat exchanger network was established through integrating two heat exchanger networks.
文摘Underground mines in Arctic and Subarctic regions require the preheating of mine intake air during winter.The cold fresh air of those remote areas can be as severe as40℃ and commonly needs to be heated to around+3℃.This extensive amount of heating is usually provided by employing large-size air heaters,fueled by diesel,propane,natural gas,or heavy oil,leading to high energy costs and large carbon footprints.At the same time,the thermal energy content of a diesel generator sets(gen-sets)exhaust is known to be one-third of the total heating value of its combusted fuel.Exhaust heat recovery from diesel gen-sets is a growing technology that seeks to mitigate the energy costs by capturing and redirecting this commonly rejected exhaust heat to other applications such as space heating or pre-heating of the mine intake air.The present study investigated the possibility of employing a simple system based on off-theshelf heat exchanger technology,which can recover the waste heat from the exhaust of the power generation units(diesel gen-sets)in an off-grid,cold,remote mine in Canada for heating of the mine intake air.Data from a real mine was used for the analysis along with environmental data of three different location-scenarios with distinct climates.After developing a thermodynamic model,the heat savings were calculated,and an economic feasibility evaluation was performed.The proposed system was found highly viable with annual savings of up to C$6.7 million and capable enough to provide an average of around 75%of the heating demand for mine intake air,leading to a payback period of about eleven months or less for all scenarios.Deployment of seasonal thermal energy storage has also been recommended to mitigate the mismatch between supply and demand,mainly in summertime,possibly allowing the system to eliminate fuel costs for intake air heating.
基金Supported by the National Basic Research Program of China("973"Program,No.2011CB707201)the National Natural Science Foundation of China(No.51206117)
文摘A bottoming cycle system based on CO2 Brayton cycle is proposed to recover the engine exhaust heat. Its performance is compared with the conventional air Brayton cycle under five typical engine conditions. The results show that CO2 Brayton cycle proves to be superior to the air Brayton cycle in terms of the system net output power, thermal efficiency and recovery efficiency. In most cases, the recovery efficiency of CO2 Brayton cycle can be higher than 9% and the system has a better performance at the engine＇s high operating load, The thermal efficiency can be as large as 24.83% under 100% olaerating load, accordingly, the net outnut nower of 14.86 kW in nhtnined
基金supported by the National Natural Science Foundation of China(No.52227813)China Postdoctoral Science Foundation(Nos.2023M740905,2023T160164)+3 种基金National Key ResearchDevelopment Program of China(No.2022YFE0210200)Natural Science Foundation of Heilongjiang Province(No.LH2023E043)the Fundamental Research Funds for the Central Universities(Nos.2022ZFJH04,HIT.OCEF.2021023)。
文摘The burning of fossil fuels in industry results in significant carbon emissions,and the heat generated is often not fully utilized.For high-temperature industries,thermophotovoltaics(TPVs)is an effective method for waste heat recovery.This review covers two aspects of high-efficiency TPV systems and industrial waste heat applications.At the system level,representative results of TPV complete the systems,while selective emitters and photovoltaic cells in the last decade are compiled.The key points of components to improve the energy conversion efficiency are further analyzed,and the related micro/nano-fabrication methods are introduced.At the application level,the feasibility of TPV applications in high-temperature industries is shown from the world waste heat utilization situation.The potential of TPV in waste heat recovery and carbon neutrality is illustrated with the steel industry as an example.
基金financially supported by the National Natural Science Foundation of China(No.51972019)the National Key Research and Development Program of China(No.2019YFC1905702)。
文摘Waste heat recovery from hot steel slag was determined in a granular bed through the combination of numerical simulation and an industrial test method.First,the effective thermal conductivity of the granular bed was calculated.Then,the unsteady-state model was used to simulate the heat recovery under three different flow fields(O-type,S-type,and nonshielding type(Nontype)).Second,the simulation results were validated by in-situ industrial experiments.The two methods confirmed that the heat recovery efficiencies of the flow fields from high to low followed the order of Nontype,S-type,and O-type.Finally,heat recovery was carried out under the Nontype flow field in an industrial test.The heat recovery efficiency increased from~76%and~78%to~81%when the steel slag thickness decreased from 400 and 300 to 200 mm,corresponding to reductions in the steel slag mass from 3.96 and 2.97 to 1.98 t with a blower air volume of 14687 m^(3)/h.Therefore,the research results showed that numerical simulation can not only guide experiments on waste heat recovery but also optimize the flow field.Most importantly,the method proposed in this paper has achieved higher waste heat recovery from hot steel slag in industrial scale.
基金Supported by National Natural Science Foundation of China (No. 50376044)
文摘An exhaust heat recovery generator is proposed to be integrated with conventional gas-fired triple-effect LiBr/water absorption cooling cycles to improve system energy efficiency. As a case study, simulation of the novel cycle based on promising parallel flow with cooling capacity of 1 150 kW is carried out under various heat recovery generator vapor production ratios ranging from 0 to 3.5%. The life cycle saving economic analysis, for which the annual gas conservation is estimated with Bin method, is employed to prove the worthiness of extra expenditure. Results show that the optimum gas saving revenue is obtained at 2.8% heat recovery generator vapor production ratio with 42 kW exhaust heat recovered, and the system energy efficiency is improved from 1.78 to 1.83. The initial investment of exchanger can be paid back within 7 years and 9 000 CNY of gas saving revenue will be achieved over the 15-year life cycle of the machine. This technology can be easily implemented and present desirable economic effects, which is feasible to the development of triple-effect absorption cycles.
基金Project(2009Gk2009)supported by the Science and Technology Department Funds of Hunan Province,ChinaProject(12C0379)supported by the Scientific Research Fund of Hunan Province,ChinaProject(13QDZ04)supported by the Scientific Research Foundation for Doctors of Xiang Tan University,China
文摘Dynamic performance is important to the controlling and monitoring of the organic Rankine cycle(ORC) system so to avoid the occurrence of unwanted conditions. A small scale waste heat recovery system with organic Rankine cycle was constructed and the dynamic behavior was presented. In the dynamic test, the pump was stopped and then started. In addition, there was a step change of the flue gas volume flow rate and the converter frequency of multistage pump, respectively. The results indicate that the working fluid flow rate has the shortest response time, followed by the expander inlet pressure and the expander inlet temperature.The operation frequency of pump is a key parameter for the ORC system. Due to a step change of pump frequency(39.49-35.24 Hz),the expander efficiency and thermal efficiency drop by 16% and 21% within 2 min, respectively. Besides, the saturated mixture can lead to an increase of the expander rotation speed.
文摘Ground-coupled heat pumps(GCHP)are commonly used in residential heating system.To mitigate the boreholes temperature dropping with operating time,a new exhaust-air recharging system is developed.The new recharging system can be used in three operational modes.In this paper,a ground-coupled heat recovery ventilation(HRV)model is discussed.A thermal model is set up to find the optimal brine flow rate and heat transfer allocation ratio between exhaust and supply coils for maximum heat recovery efficiency.Contrary to the conventional liquid-loop HRV systems,the brine temperature entering the exhaust coil never goes blow zero(0℃),and hence defrosting is needless in the ground-coupled HRV system.This can make the ground-coupled HRV system over 20% more efficient than a conventional HRV system at low outdoor temperatures.
文摘Thermoelectric generators(TEGs)are considered promising devices for waste heat recovery from various systems.The Seebeck effect can be utilized to generate power using the residual heat emitted by the filter dryer receiver(FDR)of an air conditioning(A/C)system,which would otherwise go to waste.The study aims to build a set of thermoelectric generators(TEG)to collect the waste heat of the FDR and generate low-power electricity.A novel electrical circuit with two transformers is designed and fabricated to produce a more stable voltage for operation and charging.The thermoelectric generator(TEGs)was installed on the FDR of the A/C unit.The test showed that climate conditions have a significant impact on the output power generated from the system.The results showed that the peak voltage recorded in the current study is 5.2 V per day(wet,cold,and wind weather)with an output power of 0.2 W.These values are acceptable for powering the load and charging a single battery with 3.5 V as the voltage increases battery 0.1 V/20 min charge.A case study of operating the emergency signs in a building was considered.The current heat recovery system is deemed to be easily installed and can be connected to a network of TEGs to produce more power.
文摘This study explores the potentials of employing an Organic Rankine Cycle (ORC) system with variable inlet guide vanes (VIV) turbine geometry designed on a GT-Suite platform for effective exhaust heat recovery (EHR) application onboard passenger vehicles. The ORC model simulation was based on vehicle speed mode using R245fa as working fluid to assess the thermal performance of the ORC system when utilizing modified turbine geometry. Interestingly, the model achieved a very improved performance in contrast to the model without a modified turbine configuration. The results revealed the average 2.32 kW ORC net output, 4.93% thermal efficiency, 6.1% mechanical efficiency, and 5.0% improved brake specific fuel consumption (BSFC) for the developed model. As determined by the performance indicators, these promising results from the model study show the prospect of EHR technology application in the transportation sector for reduction in exhaust emissions and fuel savings.
基金Project(51276023) supported by the National Natural Science Foundation of ChinaProject(09k069) supported by the Open Project Funded by Universities Innovation Platform, Hunan Province, ChinaProject(2011GK311) supported by the Office of Science and Technology of Hunan Province, China
文摘Drum level sloshing is the latest discovery in the application of heat recovery steam generator (HRSG) in combined cycle, and shows certain negative influence on drum level controlling. In order to improve drum level controlling, influence factors on the drum level sloshing were investigated. Firstly, drum sub-modules were developed using the method of modularization modeling, and then the model of drum level sloshing was set up as well. Experiments were carried out on the experimental rig, and the model was validated using the obtained experimental results. Dynamic simulation was made based on the model to get a 3-D graph of drum level sloshing, which shows a vivid procedure of drum level sloshing. The effect of feed-water flow rate, main-steam flow rate and heating quantity on the drum level sloshing was analyzed. The simulation results indicate that the signals with frequency higher than 0.05 Hz are that of drum level sloshing, the signals with frequency of 0.0-0.05 Hz are that of drum level trendy and "false water level", and variation of the feed-water flow rates, main-steam flow rates and heating quantities can change the frequency of drum level sloshing, i.e., the frequency of sloshing increases with the increase of feed-water flow rate, or the decrease of the main-steam flow rate and the heating quantity. This research work is fundamental to improve signal-to-noise ratio of drum level signal and precise controlling of drum level.
基金support for this work provided by the National Natural Science Foundation of China(51974087 and 51904074)Anhui Provincial Natural Science Foundation(1908085QE203)+1 种基金Natural Science Research Foundation of Anhui Province University(2022AH050262)Science Research Foundation of Anhui Jianzhu University(2020QDZ02).
文摘In order to improve the recovery and utilization rates of sinter waste heat effectively,the organic Rankine cycle(ORC)system with subcritical cycle was designed to recover the low-temperature sinter cooling flue gas waste heat in an annular cooler for power generation.The thermodynamic,economic and multi-objective optimization models of ORC system were established,and R600a was selected as the ORC working medium.Subsequently,the variations in system thermodynamic performance and economic performance with the ORC thermal parameters were discussed in detail,and the optimal ORC thermal parameters were determined.The results show that the system net output power increases with increasing the evaporation temperature and decreasing the condensation temperature and increases first and then,decreases with the increase in superheat degree for a given flue gas outlet temperature in the evaporator,while the heat transfer area per unit net output power appears different variation trends in various ranges of flue gas outlet temperature.Taking the sinter cooling flue gas waste heat of 160℃as the ORC heat source,the optimal thermal parameters of ORC system were the flue gas outlet temperature of 90℃,the evaporation temperature of 95℃,the superheat degree of 10℃,and the condensation temperature of 28℃.
文摘In present,the wet-based pattern is mainly adopted to deal with the steel slag by steel plant at home and abroad,the wet-based technology has some defects;Wasting of water,pollution of the environment,and the slag has not been fully recycled.This paper presents a new method,which is aimed to realize dry granulation,waste heat recovery and comprehensive utilizing the steel slag.According to the ideas of wind quenching granulation,the heating slag from the converter furnace,was bring to the granulation heat exchange system,through the process of breaking in a container,the granulation heat exchange system has the functions of feeding continuously and heat exchange.The heat air,through the diversion tubes,could be recycled in removing the dust.The granulation slag could be bring to a confined roller,granulating and cooling secondarily.The roller export was connected to a magnetic separator.The separated iron could be recycled,and the remaining slag could also be reused as building materials,in process of stabilization and secondary magnetic separation.The heated air could be guided into the boiler to generate the steam,which can be used to generate electricity,or use as cleaned energy,realizing the target to recycle the waste heat in steel slag.The highlights of the new method are dry granulation and waste heat recovery.This paper states the process of heat exchange between the air and the steel slag in the system of granulation heat exchange in the new technical process.In theory,it has been proved reasonable with the the system of granulation heat exchange,and also the work conditions has been optimized.
基金supported by the Project of Science and Technology Program of Beijing Municipal Chao Yang District(CYSF2005,Zhun Li,http://www.bjchy.gov.cn/dynamic/notice/8a24fe83722fa7180172360a3f46044c.html).
文摘The building energy consumption is an important part among the total society energy consumption,in which the energy consumption for air conditioning occupies almost 70%.The energy consumption of the air conditioning system for fresh air handling can be saved effectively when the exhaust air energy could be recovered to preheat or precool the fresh air.Considering the install locations requirements on field,the pump-driven heat pipes(PHP)were developed as heat recovery ventilators(HRVs)and used in an existing experiment building in Beijing Urban.The thermal performance of the PHP HRVs was tested in real operation time periods under winter running mode.Both the power and heat consumption of the modular air handling units with and without HRVs were monitored and obtained,as well as the hourly power and heat consumption.The energy savings of HRVs were analyzed.The results indicate that the PHP HRVs can work steadily and meet the energy recovery need well.The temperature effectiveness of the HRVs can be kept from 60%to 70%.The test total energy saving rate was 24.48%,and the average hourly heat consumption reduced by 28.54%.The daily energy consumption can be saved by 118 kWh,and the energy savings can reach to 9440 kWh for a whole winter.
文摘Concentrating Solar Power(CSP)plants offer a promising way to generate low-emission energy.However,these plants face challenges such as reduced sunlight during winter and cloudy days,despite being located in high solar radiation areas.Furthermore,their dispatch capacities and yields can be affected by high electricity consumption,particularly at night.The present work aims to develop an off-design model that evaluates the hourly and annual performances of a parabolic trough power plant(PTPP)equipped with a waste heat recovery system.The study aims to compare the performances of this new layout with those of the conventional Andasol 1 plant,with the aim of assessing the improvements achieved in the new design.Based on the results,it can be concluded that the new layout has increased the annual generated power to almost 183 GWh(an increase of about 7.60% is achieved compared to the Andasol 1 layout that generates 169 GWh annually).Additionally,the proposed installation has achieved an efficiency of 20.55%,which represents a 7.87% increase compared to the previous design(19.05%).The Levelized Cost of Electricity(LCOE)of the new layout has been reduced by more than 5.8% compared to the Andasol 1 plant.Specifically,it has decreased from 13.11 to 12.35 c/kWh.This reduction in LCOE highlights the improved cost-effectiveness of the newlayout,making it amore economically viable option for generating electricity compared to the conventional Andasol 1 plant.
