1139results about How to "Good cooling effect" patented technology

The invention relates to multifunctional protective composite coating material, which is recombined with one layer or multilayer specific functional coating. Corrosion transformation, thermal obstructing, thermal reflecting and thermal emitting are reduced through conducting the rust protection processing for metal base plate. The coating material has the advantages of high reflectance for visible sunlight and near-infrared sunlight, strong radiation ratio in 8-13.5 mu m bands, low thermal conductivity coefficient, excellent temperature reduction effect in summers, thermal radiation property approximately to background in visible lights and infrared bands, excellent concealment effect and favorable corrosion property and the like.

The invention discloses a liquid-cooled radiation structure, which comprises a substrate and at least one radiation fins, wherein the substrate is provided with at least one liquid input pipeline, at least one liquid output pipeline and at least one groove; the inner side of the groove is communicated with the liquid input pipeline and the liquid output pipeline to form an opening respectively; in addition, the radiation fin is provided with a plate body which can be embedded into and seal the groove; and the surface of the plate body is provided with a plurality of flow deflectors which can be embedded into the groove. The flow deflectors and the groove form a plurality of runners allowing the shunting of liquid, and the liquid flowing through the liquid input pipeline and the liquid output pipeline can flow among the plurality of runners by flowing in and out of the two openings of the groove, so that continuous cyclic radiation can be realized in the substrate.

The invention discloses a server machine cabinet. The server machine cabinet comprises a shell, a server and a liquid-cooled radiating system, wherein the server and the liquid-cooled radiating system are arranged in the shell; a heat conducting plate close to the server is arranged in the shell; the liquid-cooled radiating system comprises a refrigerator and a pipeline, wherein the refrigerator is arranged out of the shell; the pipeline connects the heat conducting plate with the refrigerator; the heat generated by the server in working forms a heat flow in the shell; the heat flow is cooled at the heat conducting plate; and the pipeline is extended out of the shell and is connected with the two opposite ends of the refrigerator respectively so as to transfer the heat, absorbed from the server, of the heat conducting plate to the refrigerator to perform heat exchange. In the server machine cabinet, cold-and-hot internal circulation is formed in the shell, so that the server machine cabinet contributes to reducing heat exchange space in the shell and increasing a radiating effect; therefore, the stability and the safety of server operation are improved.

The invention relates to the field of railway locomotive, electricity multiple unit and industrial control, in particular to a cooling technology of large-power current transformers, i.e. a two-side water cooling substrate of a power module of a current transformer. The invention solves the problem that the traditional heat sink of the power module of the large-power current transformer has the defects of large size, poor cooling effect and high producing cost. The two-side water cooling substrate is connected with a circulating water system of the current transformer and comprises a cooling substrate which is formed by brazing an upper cover plate and a lower substrate; the end surface of the lower substrate is provided with a connecting water channel and a water inlet and a water outlet of external circulating water; installation holes are arranged on the external surfaces of the upper cover plate and the lower substrate; and the internal surface of the lower substrate is provided with a groove-shaped water channel in which square wave shaped fins are arranged, wherein the fins are bent regularly. The two-side water cooling substrate can realize two-side water cooling, which reduces the heat resistance of the cooling substrate and increase the cooling efficiency on one hand, and lowers the difficulty of the producing process and reduces the producing cost on the other hand.

The present invention relates to an oven which comprises an oven body which is provided with a baking cavity body inside, a front frame arranged at the face of the over body, an oven door which can open and close the cavity body and a faceplate which is arranged over the oven door. The oven body is provided with a vent. A gap is arranged between the oven door and the faceplate. The oven door is provided with a cooling passage which is provided with an upper intake and a lower intake. The upside of the cavity body is provided with a cover plate. The cover plate and the external wall of the cavity body form an air course with an inlet and an outlet. The inside of the oven body is provided with a fan which ensures the airflow inside the air course flows from the inlet to the outlet. The oven of the present invention is characterized in that the front frame is provided with a through hole which is corresponding to the gap and the upper intake; the inlet of the air course is corresponding to the through hole, which ensures that the lower intake of the cooling passage and the gap become a first air inlet and a second air inlet respectively; the vent on the oven body becomes an air outlet. The present invention uses the double functions of the natural rising of hot air and the compulsory driving of a motor, so the refrigeration effect of the oven door is better, meanwhile, the gap is used as the second air inlet, which also ensures the using safeness.

The invention discloses heat-dissipation paint for an LED lamp, which is characterized by comprising the following components in percentage by mass: 30 to 50 percent of organosilicon polyurethane prepolymer, 10 to 20 percent of mixed solvent, 1 to 5 percent of silane coupling agent KH560, 8 to 15 percent of beryllium oxide, 15 to 50 percent of aluminium nitride and 1 to 5 percent of oleinic acid. A preparation method comprises the following steps of: firstly, uniformly blending the liquid components; secondly, adding solid components and uniformly stirring; and finally, grinding on a grinder and then packaging. The heat-dissipation paint for the LED lamp in the invention has the advantages of temperature resistance, aging resistance, high adhesion and good heat-dissipation effect.

The invention relates to cold accumulation transportation technique field, specially relating to a using method of a set of cold accumulation thermal insulation device. The method comprising following steps: A, preparing for boxing; B, boxing freight, C, measuring temperature and sealing the box; D, opening the box and measuring temperature after the freight reaches the destination; E, cleaning the device. The inventive method is provided with low resource consumption, a low transportation cost, accords with environmental protection requirements, and multi-temperature-segment service is provided. Special requirements for different temperatures and different service quality are satisfied in cold-chain logistic markets, and refrigerated transport service of a small batch and poly batches is provided.

The invention discloses a horizontal sand mill which comprises a base, a motor, a main shaft and a grinding cylinder. The motor is fixed on the base, the main shaft is hollow and is connected with the motor through a belt pulley, cooling oil chambers are fixedly arranged around the main shaft, a cooling water flowing passage is intermediately formed, a plurality of grinding rods are fixedly arranged around the outer wall of a grinding inner sleeve, a cooling water pipe is arranged in the grinding inner sleeve, a U-shaped spiral water channel is fixedly arranged around the outer wall of the cooling water pipe, and a feeding hole and a discharging hole are arranged on a grinding outer sleeve. In the mill, both-end-surface mechanical sealing is adopted and a sealing ring is arranged at the joint of a bearing and a shaft. By adopting the technical scheme of the invention, the defects caused by overhigh temperature generated when a traditional horizontal sand mill runs are effectively overcome, the sand mill is stable and reliable to run, and the production quality and the operation efficiency are greatly improved.

Disclosed is an iron-core-provided self-circulating evaporating cooling disk-type motor. A stator of the motor is composed of a stator iron core (1), a stator coil (2), an enclosure (6) and a sealing disk (7). A rotor is composed of a bearing (8), a shaft (9), a rotor iron core (10) and magnetic steel (11). An evaporating cooling system is composed of a condenser (3), a steam inlet pipe (4), a liquid return pipe (5), a stator cavity (13) and evaporating cooling media (12). The enclosure (6) and the sealing disk (7) form the stator cavity (13) and the stator cavity (13) is filled with the evaporating cooling media (12). When the disk-type motor runs, heat generated by the stator iron core (1) and the stator coil (2) due to losses is transmitted to the evaporating cooling media (12), so that the temperature of the evaporating cooling media rises, the evaporating cooling media are gasified, phase-change heat absorption is generated, and the evaporating cooling media enter the condenser (3) through the steam inlet pipe (4) to be cooled and become liquid and then flow back into the stator cavity (13) through the liquid return pipe (5). Thus, the self-circulating evaporating cooling system without external force driving is formed.

The invention relates to a diamond fret saw, which comprises a fret saw inner core, wherein the fret saw inner core is formed by mutually twisting more than two strands of metal wires; a metal layer is plated on the surface of the fret saw inner core; the surface of the metal layer is fixedly provided with abrasive grains; and the abrasive grains are diamond particles, other wear-resistant material particles, or mixture of diamond particles and other wear-resistant material particles. The continuous production technology of the diamond fret saw provided by the invention has the advantages of being reasonable in flow, high in yield and the like, and the diamond fret saw can be continuously produced.

The invention discloses a stepped differential-velocity fluidized bed cooler relating to a fluidized bed cooler. The invention aims to solve the problems of overhigh discharging temperature, poor cooling effect and non-uniform discharged grain temperature in the traditional fluidized bed cooler. A feeding pipe is communicated with the side wall at one end of a fluidized bed main body; an outer side wall at the other end of the fluidized bed main body is provided with an exhaust pipe and a first discharging pipe from the top down; a plurality of air chambers are arranged in the fluidized bed main body; the air chambers are arranged in sequence from high to low along the feeding-to-discharging direction of the fluidized bed main body; the upper end of each air chamber is provided with an air distribution plate; each air distribution plate is provided with a second discharging pipe; a plurality of air distribution holes are uniformly distributed and processed on each air distribution plate; a hood is arranged at each air distribution hole; an overflow plate is vertically arranged between every two adjacent air distribution plates; and the height of each overflow plate is sequentially and progressively reduced along the feeding-to-discharging direction of the fluidized bed main body. The stepped differential-velocity fluidized bed cooler is used for high-temperature granular materials in the cooling industry field.

The invention discloses an icing sugar spray drying system with a high DE value, which consists of a feeding part, an atomizing part, a drying part and an air supply part; a sizing agent obtained from pretreatment is thrown into a stock chest, the stock chest is connected with the feeding part, the feeding part conveys syrup to the atomizing part, then the syrup enters the drying part after being atomized by the atomizing part, and dry and hot wind is sent to the drying part by the air supply part; the syrup evaporated moisture content at the drying part enters the stage of product package after whirl wind separation; as the icing sugar has lower softening point (about 50 DEG C) and strong hygroscopicity, the icing sugar is soften to stick on the wall if the temperature of the tower wall is too high, while the icing sugar reaches the dew point to stick on the wall if the temperature of the tower wall is too low, therefore, a jacket is utilized to control the temperature of the tower wall, the entering air temperature is controlled at 120-140 DEG C, and the leaving air temperature is controlled at 65-75 DEG C, thus being capable of preventing the icing powder from sticking on the wall.

The invention discloses a phase-change composite microcapsule hydrogel and a physical antipyretic patch thereof; the phase-change composite microcapsule hydrogel contains a macromolecular substance, phase-change composite microcapsules, thermochromic microcapsules and other materials. The antipyretic patch is composed of a back lining layer, a hydrogel layer and an anti-sticking layer successively; the hydrogel is a phase-change composite microcapsule hydrogel and coats the back lining layer; the back lining layer is made of a pharmaceutical-graded non-woven fabric and is printed with a color-temperature correlation band, and the middle of the back lining layer is left with a gap for observation of color change of the hydrogel layer. The thermochromic microcapsules in the antipyretic patch can be gradually faded along with body temperature rising and is faded to be colorless when the temperature is higher than 39.5 DEG C, to warn that the antipyretic patch is failed. The phase-change composite microcapsule material of the antipyretic patch can be turned back to a solid after being cooled, can be used repeatedly, thereby saving cost. The phase-change material and the temperature-sensitive color changing material adopted by the antipyretic patch are both macromolecular materials, and the antipyretic patch is non-toxic and harmless, has no side effect and is safe to use.

The invention discloses a power distribution cabinet with an efficient heat dissipation and cooling function. The power distribution cabinet comprises a cabinet body, cooling water pipes, a cooling blower and a plurality of blast pipes; the cabinet body comprises outer plates and inner plates; electric appliance component mounting grooves are formed in the inner side walls of the inner plates separately; an interval is reserved between the outer plate and the corresponding inner plate; the cooling water pipes are arranged in an S-shaped spiral manner from bottom to top along the intervals; the cooling blower is fixed to the top of the cabinet body; the blast pipes are fixed to the side surfaces of the mounting grooves and are in the same direction with the mounting grooves. According to the structure, the power distribution cabinet with the efficient heat dissipation and cooling function adopts both air cooling and water cooling manners to realize heat dissipation, and has the characteristics of being quick in heat dissipation, and excellent in cooling effect; meanwhile, the cabinet body is provided with a ventilation device, so that the realization of the whole cooling effect of the cabinet body is accelerated.

A water cooled electromagnetic crystallizer for conticasting is composed of upper and lower flanges, coil, sleeve pipe of crystallizer, cooling water jacket, cooling water tube, connection part and lifting gear. It features that the upper part of said sleeve pipe has local slit structure, the cooling water tube is arranged in split body and a water seam structure is formed between the lower part of said sleeve pipe and cooling water jacket.

The invention discloses a flexible heat conduction / heat storage double-function composite material. The flexible heat conduction / heat storage double-function composite material is characterized in that (1-40wt% of) phase-change heat storage material particles are uniformly dispersed in matrixes, and the matrixes comprise (60-99wt% of) high-heat-conduction materials and are of three-dimensional stereoscopic network structures. The invention further discloses a method for preparing the flexible heat conduction / heat storage double-function composite material and application of the flexible heat conduction / heat storage double-function composite material. The flexible heat conduction / heat storage double-function composite material, the method and the application have the advantages that the flexible heat conduction / heat storage double-function composite material has a phase-change heat storage function with quick response capacity and is extremely high in heat conductivity (20-200 W / mK), accordingly, heat can be quickly transferred, heat of high-heat-production components such as chips and screens can be effectively conducted / absorbed, the hot-spot temperatures can be lowered, the service life of electronic equipment can be prolonged, the flexible heat-conduction / heat storage double-function composite material is free of leakage and high in flexibility and can be widely applied to electronic equipment such as intelligent mobile phones with strict requirements on structure spaces, and the like.

The invention discloses an integrated servo motor. A servo motor body (1) is connected with a servo driver via a cooler, the cooler comprises a cooling jacket which is sleeved on the servo motor body (1), a casing (2) of the servo driver is connected with the cooling jacket, and the wall of the cooling jacket includes cooling channels; the casing (2) of the servo driver internally includes an enclosed cavity and is made of a metal heat-conductive material, and a fan (11) is installed in the casing; an electrical conjunction box (16) is positioned in the cooling jacket, and an encoder (17) is connected with one end, close to the electrical conjunction box (16), of a central shaft of the servo motor body (1); and a vibration-proof device which is used for protecting electronic components (12) in the servo driver is arranged in the servo driver. The integrated servo motor of such structure is good in heat radiation and cooling effects, and is convenient to maintain.

The invention discloses an electrified curing machine which is convenient to operate. The curing machine comprises a frame, wherein the frame is provided with a left support block and a right support block, a plurality of middle support blocks are arranged between the left support block and the right support block, and a sliding clamp is arranged at the upper end of the right support block; the middle part of the sliding clamp is connected with the piston rod of a locating cylinder by a connecting block, the locating cylinder is arranged on the frame, and a locating plate is arranged on the frame between one ends of the left support block and the right support block; the locating plate is uniformly provided with a plurality of locating slots mutually matched with heat conduction pipes on a PTC (Positive Temperature Coefficient) heater, the frame at one side of the locating plate is provided with an electrode post fixing plate and a cylinder, and a plurality of mounting slots matched with the locating slots are uniformly arranged on the electrode post fixing plate; electrode posts are respectively arranged at the two sides of the mounting slots, a push plate is connected on the piston rod of the cylinder, and a plurality of connecting conductive posts mutually matched with the mounting slots are uniformly arranged on the push plate.

The invention discloses a light emitting diode (LED) spherical lamp transmitting heat through liquid. The LED spherical lamp comprises a lamp cap assembly formed by a lamp cap and a lamp connecting seat, a hollow radiator, a driving power supply, a light emitting assembly formed by a light engine module and a high-transmittance temperature-resistant protective cover, and a glass cover, wherein a power supply containing cavity is arranged inside the hollow radiator, a seal cover is sleeved outside the driving power supply, the bottom of the seal cover is connected with the inner circumferential wall of the hollow radiator in sealed mode, a sealed liquid circulation radiating channel is formed by a gap between the high-transmittance temperature-resistant protective cover and the glass cover and a gap between the seal cover and the hollow radiator in communicated mode, and high-thermal conductivity liquid is installed in the liquid circulation radiating channel. Heat produced by light of lighting of LED lamp beads in the light engine module heats the high-thermal conductivity liquid, the high-thermal conductivity liquid produces convection in the liquid circulation radiating channel after being heated, the heat is diffused into air through the glass cover and the hollow radiator, and the radiating mode is good in effects, and the junction temperature of the LED lamp beads can be effectively reduced.

The invention belongs to the field of cold region slope support and discloses a cold region active ventilation cooling self-recovery slope anchorage structure and a construction method. The cold region active ventilation cooling self-recovery slope anchorage structure comprises a framework, ventilation anchor pipes and a ventilation system. The ventilation anchor pipes are formed in the mode that anchor pipes are nested in ventilation pipes coaxially through positioning rings and the ventilation pipes are coaxially sleeved with exhaust pipes. The ventilation system is composed of fans, temperature control switches and solar panels, all of which are connected through wires. Slurry is injected into the anchor pipes, passes through slurry outlet holes and is bonded with surrounding stable frozen soil; geogrids, drain pipes and the framework are constructed on the slope surface, and the ventilation anchor pipes penetrate through the framework; the front section of each ventilation anchor pipe is sleeved with a flange base plate and a spring sequentially and is fixed on the framework through an anchorage device; plants are planted in the geogrids, and a drain channel is arranged at the slope toe; the fans are installed at the front sections of the anchor pipes, the temperature control switches and the solar panels are arranged on the framework, and the fans, the temperature control switches and the solar panels are connected through the wires. The cooling effect is remarkable due to automatic air supply, the swelling reduction, shock absorption and self-recovery functions are remarkable, water is drained in time, and development of frozen soil is promoted due to the geogrid slope surface and the plants; the method is easy and convenient to implement, and construction is rapid.

The invention relates to a chassis cooling system for a battery pack. The chassis cooling system comprises a chassis shell which opens upwards and a plurality of battery pack separating plates. A plurality of sliding grooves are formed in the inner side wall of the chassis shell, and the battery pack separating plates are embedded into the sliding grooves. A liquid storage cavity filled with negative thermal expansion materials is formed in each battery pack separating plate, and a water inlet channel and a water outlet channel which both communicate with the liquid storage cavity are also formed in each battery pack separating plate. A cooling cavity and ducts communicating with the water inlet channels and the water outlet channels are formed in the chassis shell, the cooling cavity communicates with the ducts communicating with the water inlet channel and the water outlet channel to form a cooling liquid passage, and the cooling cavity is filled with air bags.

The invention discloses a method for assembling an LED lighting lamp, which is characterized by comprising the following step of: arranging one or more heat radiators on a fixed pore plate (3), wherein one or more standard interface LED bulbs (1) is / are arranged on each heat radiator, and each standard interface LED bulb (1) is integrated with an LED light module and an independent drive power supply. According to the invention, one or more heat radiator is / are arranged on the fixed pore plate, and each heat radiator is provided with one or more standard interface LED bulbs. Compared with the traditional method for assembling the LED lamp, the method disclosed by the invention has the advantages of better heat radiating effect, low cost, more simple assembly, convenience for standardized popularization and wider application range.

The invention discloses a heat radiating method and mechanism of an electric automobile battery box. The heat radiating method comprises the following steps: introducing natural air outside an automobile to radiate heat when the temperature in the battery box exceeds the preset temperature T2; radiating heat by extracting air-conditioning cold air in the automobile when the temperature in the battery box exceeds the preset temperature T4, wherein T4>T2; and stopping extracting the air-conditioning cold air in the automobile when the air-conditioning cold air is subjected to heat radiation, so that the temperature decreases and does not exceed the preset temperature T3 which is lower than T4 and higher than T2, and introducing natural air outside the automobile to radiate heat. The heat radiation method can play a better heat radiation effect on the battery box, does not waste energy, and meanwhile does not affect the environment in the automobile.

The invention discloses a cold accumulation type air conditioner and a control method thereof. The cold accumulation type air conditioner comprises a refrigeration agent circulating system and a secondary refrigerant circulating system, wherein the refrigeration agent circulating system comprises a compressor, a condenser, a throttling device and a cold accumulation type evaporator, which are orderly connected end to end; the cold accumulation type evaporator comprises an evaporation unit and a cold accumulation unit which are spaced; the evaporation unit is suitable to supply cold energy to the cold accumulation unit; the cold accumulation unit comprises multiple cold accumulation monomers; a hydrate of carbon dioxide and tetrabutylammonium bromide is loaded in each cold accumulation monomer; the secondary refrigerant circulating system comprises a first heat exchanger, a circulating pump and a second heat exchanger, which are orderly connected end to end; the first heat exchanger is arranged in the cold accumulation unit; and the second heat exchanger is arranged in an indoor environment. The cold accumulation type air conditioner is good in refrigeration effect, and further, is low in production cost and better in practicability.

The invention provides a charging pile with good heat dissipation effect, and relates to the field of charging piles. The charging pile comprises a base, wherein a supporting column is fixedly installed in the middle of the top of the base; a box body is fixedly installed at the top of the supporting column, and a power supply body is fixedly installed in the middle of the bottom of an inner cavity of the box body; a water cooling device is arranged on the outer side of the power supply body, and the water cooling device is fixedly connected to the inner wall of the box body; and the water cooling device comprises a water tank and a cooling pipe, a water pump is fixedly arranged on the left side of the water tank, and the water pump communicates with the water tank through a water pipe arranged at the water inlet end of the water pump. According to the charging pile with good heat dissipation effect, a gear is arranged to drive a rack to move left and right, so that a fan can move leftand right to dissipate heat from the power supply body, by arranging a ventilation window, air in the box body can circulate with the outside world, by arranging the water cooling device, heat dissipation is carried out to the air around the power supply body by water cooling, and by arranging the annular U-shaped cooling pipe, the cooling area is larger and the cooling effect is better.

An integrated radiation substrate and making method thereof, which contains a metal substrate, a metal oxide insulator for heat conduction formed on metal substrate, wires formed on metal oxide insulator surface. The making method contains A, providing a metal substrate, B, forming metal oxide insulation layer on metal substrate by anode micro-arc technology, C, coating metal membrane by vacuum physics vapor deposition, said invention can obtain higher compactness, better adhesion and radiation effect.

The invention discloses a double-sided LED display screen. The double-sided LED display screen comprises an outer frame and surface covers arranged on front and back sides of the outer frame, wherein two LED modules are arranged between the outer frame and the two surface covers; each LED module comprises a PCB (printed circuit board), LED beads are mounted on the PCB, a heat-conducting silica gel sheet is mounted on the back surface of the PCB and is equivalent to the back surface of the PCB in size, a heat-conducting plate is mounted on the inner side of the heat-conducting silica gel sheet and closely attached to the heat-conducting silica gel sheet, and multiple heat-conducting fins are arranged on the inner side surface of the heat-conducting plate. The display screen can utilize display space sufficiently for double-sided display; the heat-conducting silica gel sheets and the heat-conducting plates are arranged on the back surfaces of the double-sided display screen, the heat-conducting fins are formed on the heat-conducting plates, the double-sided LED display screen is simple in structure and has the good cooling effect, and the service life of the display screen is prolonged.

The invention relates to a motor rotor, which comprises a rotor shaft and a rotor in a rat cage shape, wherein the rotor is tightly sleeved on the rotor shaft, the rotor comprises an aluminum injection end ring and a rotor iron core arranged in the aluminum injection end ring, the rotor iron core is formed by the overlap of a plurality of pieces of rotor punching sheets, a plurality of evenly distributed rotor punching sheet grooves are arranged on the rotor punching sheets, a rotor iron core groove is formed by the overlap of a plurality of rotor punching sheet grooves, the aluminum injection end ring is integrated into a whole through aluminum filled in the rotor punching sheet grooves and aluminum distributed at the end portion of the rotor iron core. The motor rotor is characterized in that a plurality of evenly distributed through holes are arranged on the rotor punching sheets, the through holes are distributed between the inner ring of the rotor punching sheets and the minimal inner diameter of the rotor punching sheet grooves, and the rotor through holes are formed by the overlap of the plurality of the through holes. The cooling effect is better and service life of enameled wires is greatly prolonged, as the axial direction of the air pressure produced by through holes themselves is in accordance with the axial direction of the air pressure produced by motor load, and simultaneously, the through holes enlarge cooling areas. In addition, the through holes on the rotor reduce the weight of the rotor and are helpful for improving motor starting performance, and the reduction of raw materials reduces motor cost.

An air-cooled motor is disclosed, comprising a motor shaft, a stator and a rotor which are disposed co-axially, said motor shaft being fitted with a fixed seat for supporting said stator and being operatably connected with said rotor and rotatably connected with said stator, said stator having a coil coupled to conductive wires; further comprising a front cover disposed at the front side of said rotor and having wind channels, wherein a front end portion of said rotor in the proximity of said front cover is provided with an air-inflow disk which has one or more air intake grooves each passing obliquely therethrough to form a windward angle relative to the rotation direction of said rotor; and said motor further comprises an air-exhausting disk which has one or more air outlet grooves each passing obliquely therethrough to form a windward angle relative to the rotation direction of said rotor.