This paper investigates the possibility of using the free expansion of gaseous CO2 in portable air-cooling systems. The cooling capacity of the gaseous CO2 free jet expansion was calculated using three different appro...This paper investigates the possibility of using the free expansion of gaseous CO2 in portable air-cooling systems. The cooling capacity of the gaseous CO2 free jet expansion was calculated using three different approaches and the results showed that the simplified calculations would give approximated cooling values with an 11.6% maximum error. The mass flow rate, upstream pressure and cooling capacity of the gaseous CO2 decreased with time. A maximum 48.5 watts of cooling was recorded at minute 4 and a minimum value of 10.4 watts at the end of the test. The drop in cooling capacity is due to the evaporation of the liquid CO2 inside the small cylinder which cools the two-phase CO2 mixture and causes a pressure drop (from 6 MPa to 2.97 MPa), which also affects the mass flow rate of gaseous CO2 exiting the orifice (from 0.56 g/s to 0.24 g/s). If this cooling technique is to be considered in portable compact-cooling systems, the mass, pressure and cooling capacity drop with time must be solved. One of the solutions could be to cover the cylinder with a heating coat to compensate for the heat absorbed by the evaporation of the liquid CO2.展开更多
Free convection flow between two vertical parallel plates with transverse sinusoidal injection of the fluid at the stationary plate and its corresponding removal by constant suction through the plate in uniform motion...Free convection flow between two vertical parallel plates with transverse sinusoidal injection of the fluid at the stationary plate and its corresponding removal by constant suction through the plate in uniform motion has been analyzed. Due to this type of injection velocity, the flow becomes three-dimensional. Analytical expressions for the velocity, temperature, skin friction and rate of heat transfer were obtained. The important characteristics of the problem, namely the skin friction and the rate of heat transfer are discussed in detail with the help of graphs.展开更多
This paper systematically describes the technical principles,evaluation indicators,system forms and research progress of air-side evaporative cooling air conditioning systems,water-side evaporative cooling air conditi...This paper systematically describes the technical principles,evaluation indicators,system forms and research progress of air-side evaporative cooling air conditioning systems,water-side evaporative cooling air conditioning systems and freon-side evaporative cold coagulation heat air conditioning systems of Data center.In order to reduce the energy consumption of the refrigeration and air-conditioning system in the Data center,the applica-tion conditions and scenarios of the different forms of evaporative cooling air-conditioning systems should be considered comprehensively.Therefore,it is very important that the renewable energy-dry air can be used to the greatest extent.These efforts would contribute to China’s 2030"Carbon Peak"and 2060"Carbon Neutral."展开更多
High temperature heat hazard at mineral mine becomes more and more serious as the increase of mining depth.Heat sources at working faces of mineral mines are complex and are of different characteristics,presenting new...High temperature heat hazard at mineral mine becomes more and more serious as the increase of mining depth.Heat sources at working faces of mineral mines are complex and are of different characteristics,presenting new challenges for air conditioning systems.In this paper,heat sources at four types of working faces are summarized and their characteristics are investigated.Based on this,simplified equations,which are linear with length of working faces,are proposed to calculate heat dissipation rates.So that the main heat sources of different working faces can be found,and cooling load of air conditioning systems can be calculated.Then,considering main heat sources of coal mines,a typical working face is designed to investigate performances of different ventilation systems and air conditioning systems.Simulation results show that segmented ventilation systems(SC)and heat shield assisted centralized ventilation systems(CCHS)can realize much better temperature distributions at working faces.However,cooling load can be greatly reduced for CCHS,when untreated air is supplied to the coal seam side.Based on this,free cooling assisted air conditioning systems are designed,and annual average energy efficiency ratio(EERann)of the systems are investigated and compared between direct evaporate cooling and indirect evaporate cooling(IEC).For SC,as compared with scenarios without free-cooling,IEC can increase EERann by 15%-23%and 22%-32%under Benxi and Datong ambient conditions,respectively.Besides,to ensure high EERann,CCHS is preferred and it is essential to increase thermal insulation of air ducts.展开更多
文摘This paper investigates the possibility of using the free expansion of gaseous CO2 in portable air-cooling systems. The cooling capacity of the gaseous CO2 free jet expansion was calculated using three different approaches and the results showed that the simplified calculations would give approximated cooling values with an 11.6% maximum error. The mass flow rate, upstream pressure and cooling capacity of the gaseous CO2 decreased with time. A maximum 48.5 watts of cooling was recorded at minute 4 and a minimum value of 10.4 watts at the end of the test. The drop in cooling capacity is due to the evaporation of the liquid CO2 inside the small cylinder which cools the two-phase CO2 mixture and causes a pressure drop (from 6 MPa to 2.97 MPa), which also affects the mass flow rate of gaseous CO2 exiting the orifice (from 0.56 g/s to 0.24 g/s). If this cooling technique is to be considered in portable compact-cooling systems, the mass, pressure and cooling capacity drop with time must be solved. One of the solutions could be to cover the cylinder with a heating coat to compensate for the heat absorbed by the evaporation of the liquid CO2.
文摘Free convection flow between two vertical parallel plates with transverse sinusoidal injection of the fluid at the stationary plate and its corresponding removal by constant suction through the plate in uniform motion has been analyzed. Due to this type of injection velocity, the flow becomes three-dimensional. Analytical expressions for the velocity, temperature, skin friction and rate of heat transfer were obtained. The important characteristics of the problem, namely the skin friction and the rate of heat transfer are discussed in detail with the help of graphs.
基金This study was supported by the Shenzhen Sustainable Development Science and Technology Project(2021N033)the National Key Research and Development Program(2016YFC0700404)the National Natural Science Foundation of China(51676145).
文摘This paper systematically describes the technical principles,evaluation indicators,system forms and research progress of air-side evaporative cooling air conditioning systems,water-side evaporative cooling air conditioning systems and freon-side evaporative cold coagulation heat air conditioning systems of Data center.In order to reduce the energy consumption of the refrigeration and air-conditioning system in the Data center,the applica-tion conditions and scenarios of the different forms of evaporative cooling air-conditioning systems should be considered comprehensively.Therefore,it is very important that the renewable energy-dry air can be used to the greatest extent.These efforts would contribute to China’s 2030"Carbon Peak"and 2060"Carbon Neutral."
基金This work was supported by the Prospective Joint Research Project of Jiangsu Province （BY2012196） the National Natural Science Foundation of China （Grant No. 51077013）+3 种基金 Special funds for Jiangsu Province Scientific and Technological Achievements Projects of China （BA2011086） Program for Training of 333 High-Level Talent, Jiangsu Province of China （BRA2010033） Scientific Innovation Research Foundation of College Graduate in Jiangsu Province （CXLX-0134） and The Scientific Research Foundation of Graduate of South-east University （YBJJI110）.
基金The authors appreciate the support from the National Natural Science Foundation of China(No.51706015)from the Fundamental Research Funds for the Central Universities(FRF-IDRY-19-01).
文摘High temperature heat hazard at mineral mine becomes more and more serious as the increase of mining depth.Heat sources at working faces of mineral mines are complex and are of different characteristics,presenting new challenges for air conditioning systems.In this paper,heat sources at four types of working faces are summarized and their characteristics are investigated.Based on this,simplified equations,which are linear with length of working faces,are proposed to calculate heat dissipation rates.So that the main heat sources of different working faces can be found,and cooling load of air conditioning systems can be calculated.Then,considering main heat sources of coal mines,a typical working face is designed to investigate performances of different ventilation systems and air conditioning systems.Simulation results show that segmented ventilation systems(SC)and heat shield assisted centralized ventilation systems(CCHS)can realize much better temperature distributions at working faces.However,cooling load can be greatly reduced for CCHS,when untreated air is supplied to the coal seam side.Based on this,free cooling assisted air conditioning systems are designed,and annual average energy efficiency ratio(EERann)of the systems are investigated and compared between direct evaporate cooling and indirect evaporate cooling(IEC).For SC,as compared with scenarios without free-cooling,IEC can increase EERann by 15%-23%and 22%-32%under Benxi and Datong ambient conditions,respectively.Besides,to ensure high EERann,CCHS is preferred and it is essential to increase thermal insulation of air ducts.
