Heating-only fan coil(HFC)is one of the suited end users,which is not only compact but also highly efficient.And the major factors affecting the heat dissipation performance of HFC include leakage through coil bypass,...Heating-only fan coil(HFC)is one of the suited end users,which is not only compact but also highly efficient.And the major factors affecting the heat dissipation performance of HFC include leakage through coil bypass,distance between fan and coil,fan structure and air inlet type.Under natural air convection or forced,experimental studies were made on the effects of these factors upon the heat dissipation performance of HFC.The results show that:1)After reducing the leakage through coil bypass,the heat dissipation of HFC increases 16.9% under natural convection,and increases 8.3% under forced convection.2)After the distance between fan and coil be raised from 23.2cm to 41.7cm,the heat dissipation of HFC decreases 21.3% under natural convection,but increases12.8% under forced convection.3)After changing the fan structure,the heat dissipation of HFC increases 41.8% under natural convection,and the heat dissipation per motor power increases 96.1% under forced convection.4)The heat dissipations of HFC with round pass,slit and strip type of air inlet are different,whose proportion is about 100%,110%,136% under natural convection,and 100%,105%,116% under forced convection.展开更多
The duct static pressure reset (DSPR) control method is a popular modern control method widely applied to variable air volume (VAV) systems of commercial buildings. In this paper, a VAV system simulation program was u...The duct static pressure reset (DSPR) control method is a popular modern control method widely applied to variable air volume (VAV) systems of commercial buildings. In this paper, a VAV system simulation program was used to predict the system performance and zone air temperature of two kinds of layouts that were applied to a typical floor of an existing building office in Hong Kong. The position where the static pressure sensor was placed should affect the zones temperature and energy consumption. The comparison of predictions of the two kinds of layouts indicates that with the same DSPR control method the layout of the air duct might influence the fan control result and energy savings.展开更多
An innovative idea of extracting kinetic energy from man-made wind resources using ducted turbine system for on-site power generation is introduced in this paper. A horizontal axis ducted turbine is attached to the to...An innovative idea of extracting kinetic energy from man-made wind resources using ducted turbine system for on-site power generation is introduced in this paper. A horizontal axis ducted turbine is attached to the top of the chimney to harness the kinetic energy of flue gases for producing electricity. The turbine system is positioned beyond the chimney outlet, to avoid any negative impact on the chimney performance. The convergentdivergent duct causes increase in the flue gas velocity and hence enhances the performance of the turbine. It also acts as a safety cover to the energy recovery system. The results from the CFD based simulation analysis indicate that sig- nificant power 34 kW can be harnessed from the chimney exhaust. The effect of airfoils NACA4412 and NACA4416 and the diffuser angle on the power extraction by the energy recovery system using a 6-bladed ducted turbine has been studied with the CFD simulation. It is observed that the average flue gas velocity in the duct section at the throat is approximately twice that of the inlet velocity, whereas maximum velocity achieved is 2.6 times the inlet velocity. The simulated results show that about power may be extracted from the chimney flue gases of 660 MW power plant. The system can be retrofitted to existing chimneys of thermal power plants, refineries and other industries.展开更多
Air in the main pancreatic duct has been reported only rarely and might be associated with either a spontane- ous or a surgically induced alteration of the anatomy of the biliary tract. We report a case of ＂innocent...Air in the main pancreatic duct has been reported only rarely and might be associated with either a spontane- ous or a surgically induced alteration of the anatomy of the biliary tract. We report a case of ＂innocent＂ air found incidentally in the main pancreatic duct. To our knowledge, this is only the third such case reported. A 54-year-old woman presented with hemoptysis that had lasted for 3 d. She underwent a chest computed tomography scan, which revealed not only focal bron- chiectasis in the left lower lobe, but also air in the main pancreatic duct and dilatation of the common bile duct. She was managed conservatively for the hemop- blsis and no further problems developed. She had no specific gastrointestinal symptoms and had no history of surgery or medication. Her laboratory parameters were normal. Magnetic resonance cholangiopancrea- tography also demonstrated air in the main pancreatic duct and a dilated common bile duct （CBD）. Duode- noscopy revealed separate biliary and pancreatic ori-rices with patulous openings and some air bubbles ap- pearing in the pancreatic orifice. Endoscopic retrograde cholangiopancreatography （ERCP） showed the dilated CBD and pancreatic duct with some air bubbles, but no other abnormal lesions. She was discharged with no further problems. Most patients with air in the main pancreatic duct have had a pancreatobiliary disease, or a history of pancreatobiliary disease, pancreatobiliary surgery or sphincterotomy. If the air is innocent, as in our case, ERCP should be performed to evaluate any altered sphincteric function or anatomy such as patu- Ious openings.展开更多
Based on the corresponding theories of engineering thermodynamics and hydro-dynamics, a careful study is made of the characteristics of air flow in different duct-embedded ways. According to critical Reynolds number, ...Based on the corresponding theories of engineering thermodynamics and hydro-dynamics, a careful study is made of the characteristics of air flow in different duct-embedded ways. According to critical Reynolds number, the atmospheric critical velocity of the duct with different diameters, which makes laminar flow different from turbulent flow, is calculated. Given the condition in which a forced flow occurs and the wind strength is larger than the atmospheric pressure gradient along the air-duct, a rational ratio of the length to the diameter is presented. Based on the above theory and field test data on soil temperature and embankment settlement, the advantages and disadvantages are discussed in details of all duct-embedded ways that might affect the stability of embankment.展开更多
基金Supported by National11th Five-Year Plan Major Scientific and Technological Issues of China(2006BAJ01A04)
文摘Heating-only fan coil(HFC)is one of the suited end users,which is not only compact but also highly efficient.And the major factors affecting the heat dissipation performance of HFC include leakage through coil bypass,distance between fan and coil,fan structure and air inlet type.Under natural air convection or forced,experimental studies were made on the effects of these factors upon the heat dissipation performance of HFC.The results show that:1)After reducing the leakage through coil bypass,the heat dissipation of HFC increases 16.9% under natural convection,and increases 8.3% under forced convection.2)After the distance between fan and coil be raised from 23.2cm to 41.7cm,the heat dissipation of HFC decreases 21.3% under natural convection,but increases12.8% under forced convection.3)After changing the fan structure,the heat dissipation of HFC increases 41.8% under natural convection,and the heat dissipation per motor power increases 96.1% under forced convection.4)The heat dissipations of HFC with round pass,slit and strip type of air inlet are different,whose proportion is about 100%,110%,136% under natural convection,and 100%,105%,116% under forced convection.
文摘The duct static pressure reset (DSPR) control method is a popular modern control method widely applied to variable air volume (VAV) systems of commercial buildings. In this paper, a VAV system simulation program was used to predict the system performance and zone air temperature of two kinds of layouts that were applied to a typical floor of an existing building office in Hong Kong. The position where the static pressure sensor was placed should affect the zones temperature and energy consumption. The comparison of predictions of the two kinds of layouts indicates that with the same DSPR control method the layout of the air duct might influence the fan control result and energy savings.
文摘An innovative idea of extracting kinetic energy from man-made wind resources using ducted turbine system for on-site power generation is introduced in this paper. A horizontal axis ducted turbine is attached to the top of the chimney to harness the kinetic energy of flue gases for producing electricity. The turbine system is positioned beyond the chimney outlet, to avoid any negative impact on the chimney performance. The convergentdivergent duct causes increase in the flue gas velocity and hence enhances the performance of the turbine. It also acts as a safety cover to the energy recovery system. The results from the CFD based simulation analysis indicate that sig- nificant power 34 kW can be harnessed from the chimney exhaust. The effect of airfoils NACA4412 and NACA4416 and the diffuser angle on the power extraction by the energy recovery system using a 6-bladed ducted turbine has been studied with the CFD simulation. It is observed that the average flue gas velocity in the duct section at the throat is approximately twice that of the inlet velocity, whereas maximum velocity achieved is 2.6 times the inlet velocity. The simulated results show that about power may be extracted from the chimney flue gases of 660 MW power plant. The system can be retrofitted to existing chimneys of thermal power plants, refineries and other industries.
文摘Air in the main pancreatic duct has been reported only rarely and might be associated with either a spontane- ous or a surgically induced alteration of the anatomy of the biliary tract. We report a case of ＂innocent＂ air found incidentally in the main pancreatic duct. To our knowledge, this is only the third such case reported. A 54-year-old woman presented with hemoptysis that had lasted for 3 d. She underwent a chest computed tomography scan, which revealed not only focal bron- chiectasis in the left lower lobe, but also air in the main pancreatic duct and dilatation of the common bile duct. She was managed conservatively for the hemop- blsis and no further problems developed. She had no specific gastrointestinal symptoms and had no history of surgery or medication. Her laboratory parameters were normal. Magnetic resonance cholangiopancrea- tography also demonstrated air in the main pancreatic duct and a dilated common bile duct （CBD）. Duode- noscopy revealed separate biliary and pancreatic ori-rices with patulous openings and some air bubbles ap- pearing in the pancreatic orifice. Endoscopic retrograde cholangiopancreatography （ERCP） showed the dilated CBD and pancreatic duct with some air bubbles, but no other abnormal lesions. She was discharged with no further problems. Most patients with air in the main pancreatic duct have had a pancreatobiliary disease, or a history of pancreatobiliary disease, pancreatobiliary surgery or sphincterotomy. If the air is innocent, as in our case, ERCP should be performed to evaluate any altered sphincteric function or anatomy such as patu- Ious openings.
文摘Based on the corresponding theories of engineering thermodynamics and hydro-dynamics, a careful study is made of the characteristics of air flow in different duct-embedded ways. According to critical Reynolds number, the atmospheric critical velocity of the duct with different diameters, which makes laminar flow different from turbulent flow, is calculated. Given the condition in which a forced flow occurs and the wind strength is larger than the atmospheric pressure gradient along the air-duct, a rational ratio of the length to the diameter is presented. Based on the above theory and field test data on soil temperature and embankment settlement, the advantages and disadvantages are discussed in details of all duct-embedded ways that might affect the stability of embankment.
