761 results about "Expansion tank" patented technology

The invention discloses a hydropower station expansion tank water level prediction alarm method and system, belongs to the technical field of hydropower station automatic control, and aims to solve the technical problems of limited monitoring points, high false alarm rate, response delay and the like of a traditional hydropower station expansion tank water level alarm system. According to the invention, the multi-mode sensing network is constructed, and data of the pressure sensor array, the radar level meter and the float switch group are fused, so that space continuous monitoring is realized; a three-level sensing architecture is adopted, heterogeneous data is subjected to normalization processing, and dimensional differences are eliminated; the LSTM network is used for liquid level prediction, and a self-adaptive window adjustment mechanism is combined, so that the prediction flexibility and accuracy are improved; a DQN algorithm is adopted to optimize a control strategy, fine adjustment of the liquid level is achieved by adjusting the opening degree of the valve, the accuracy, timeliness and intelligent level of water level monitoring and alarming of the expansion water tank of the hydropower station are remarkably improved, the stability of the liquid level of the water tank is ensured, the system operation efficiency is optimized, the manual intervention requirement is reduced, and safety is improved.

The invention relates to the field of liquid level monitoring, in particular to a liquid level monitoring method and system for an expansion water tank. The method comprises the following steps: acquiring an acceleration sequence of the expansion tank and liquid level sequences at different preset positions, obtaining a center frequency of a target sequence, and constructing a center frequency sequence of all the liquid level sequences; a target window sequence is obtained, the liquid level change rate at any sampling moment is calculated, a change rate sequence is constructed, and the confidence weight is calculated according to the change rate sequence and the acceleration sequence; calculating a fusion liquid level value of the target window sequence; traversing different center frequencies to obtain a plurality of fusion liquid level values corresponding to any liquid level sequence, and taking a mean value of all the fusion liquid level values as a marked liquid level value of any liquid level sequence; and monitoring the liquid level of the expansion water tank according to the obtained comprehensive liquid level value. According to the technical scheme, the precision of the liquid level monitoring result can be improved.

A cooling system for an electric traction machine includes a looped conduit system for conducting a first cooling liquid and a circulation pump for conveying the first cooling liquid in a first circulation direction. The cooling system includes an expansion tank filled at least partially with the first cooling liquid and a gas, and a motor input terminal for fluidically connecting the looped conduit system on an input side to the electric traction machine. The cooling system includes a motor output terminal for fluidically connecting the looped conduit system on an output side to the electric traction machine and a first heat exchanger for dissipating heat from and / or supplying heat to the first cooling liquid. In the first circulation direction, the first heat exchanger is arranged downstream of the electric traction machine and connected via the motor input and output terminal and upstream of the expansion tank.

An expansion tank, a thermal management system, and a vehicle. An expansion tank (10) is for use in a vehicle, and the vehicle comprises a motor heat exchange circuit (20) and a battery heat exchange circuit (30). The expansion tank (10) comprises a tank body (100) and a flow channel assembly (200). The tank body (100) defines a fluid storage chamber (130) for storing a heat exchange fluid. The flow channel assembly (200) comprises a first flow channel portion (210) and a second flow channel portion (220). The first flow channel portion (210) and the second flow channel portion (220) jointly define a fluid replenishment passage (230) and a degassing passage (240). Both the fluid replenishment passage (230) and the degassing passage (240) are in communication with the fluid storage chamber (130), and both can communicate with the motor heat exchange circuit (20) and / or the battery heat exchange circuit (30). The first flow channel portion (210) and / or the second flow channel portion (220) is integrally connected to the tank body (100).

The utility model relates to an expansion tank assembly and a unit. The expansion tank assembly comprises an expansion tank, the expansion tank comprises a tank body and a connector part arranged at the bottom of the tank body, the tank body is provided with an inner cavity, an inlet and outlet flow channel is formed in the connector part, and the inlet and outlet flow channel communicates with the inner cavity; the valve assembly comprises a main body part, the main body part is provided with a first port, a second port and a third port, a first flow channel and a second flow channel communicated with the first flow channel are formed in the main body part, the first port and the second port are located at the two ends of the first flow channel, the third port is located at one end of the second flow channel, and the third port is connected with the connector part. The second flow channel is communicated with the inlet and outlet flow channel; the flow blocking component comprises a flow blocking plate and an installation blocking piece, the installation blocking piece is installed in the tank body and located in the inner cavity, one end of the flow blocking plate is fixedly connected with the installation blocking piece, the flow blocking plate penetrates through the second flow channel, and the other end of the flow blocking plate extends into the first flow channel. The expansion tank assembly can prevent liquid in the tank body from becoming dead water due to long-term non-flowing.

An activated carbon cartridge for an expansion tank for a battery cooling system is disclosed. The activated carbon cartridge includes a cartridge housing with a body and a cover. A base of the body and the cover (18) are structured to be air-permeable. Activated carbon is disposed in the cartridge housing. A seal is arranged on the base of the body for sealing against an intermediate wall of a container housing of the expansion container. A spring is supported on the lid.

The invention relates to a fluid equalization tank with a receiving chamber and a wall, wherein the wall divides the receiving chamber into a plurality of subchambers. The subchambers are fluidically connected via openings in the wall.

An expansion tank for a battery cooling system may include a tank housing having a first lid and a second lid, a dryer cartridge screwable onto a threaded nipple of the first lid, a vacuum valve arranged in the first lid, and a pressure relief valve arranged in the second lid. Fresh air from an environment may enter the expansion tank via the vacuum valve and the dryer cartridge when there is a vacuum in the expansion tank. Air may be released from the expansion tank into the environment via the pressure relief valve when there is excess pressure in the expansion tank.

The invention relates to the technical field of automobile heat management, in particular to a heat management integrated module which comprises an expansion water tank assembly. The system further comprises an agent side assembly and a water side assembly, and the expansion water tank assembly and the water side assembly are both installed on the agent side assembly. The expansion water tank assembly is matched with the water side assembly to dissipate heat of a vehicle motor and a battery, and the agent side assembly is used for adjusting the temperature of a driving cab and the temperature of the battery; the system structure is simpler, the control logic is more complex, the number of pipelines and parts and the system assembling time are reduced to the maximum extent, and the machining and assembling cost is reduced; the heat management controller is used for controlling opening or closing of related components and changing a circulation loop according to the temperature control requirements of all the components, so that fine management of heat is achieved, and energy waste is reduced.

The invention provides a temperature control system and method for a low-flash-point heat-conducting medium. The temperature control system comprises a medium circulation subsystem, a heating subsystem and a cooling subsystem. The medium circulating system stores a low-flash-point medium through a first expansion tank, and the medium is driven by a main circulating pump to flow through a heat exchanger and an evaporator; the heating system stores a high-temperature heat-conducting medium through a second expansion tank, the high-temperature heat-conducting medium is heated through an electric heating pipe, and then the flow is controlled through a main adjusting valve and a bypass adjusting valve to enter a heat exchanger to indirectly exchange heat with a low-flash-point medium. The refrigerating system is connected with the evaporator to provide cooling capacity. The temperature control method comprises the following steps: preheating a high-temperature medium to 80-85% of a target temperature, and starting a main circulating pump after the high-temperature medium is stabilized; the valve and the electric heating tube are synchronously adjusted, and the opening degree of the main valve is kept to be 40-60%; the accurate temperature control stage adopts a three-section strategy: the current situation is maintained within + / -1 DEG C, only the valve is adjusted at + / -1-5 DEG C, and the valve and the electric heating tube are cooperatively adjusted when the temperature exceeds + / -5 DEG C. According to the invention, through medium isolation and hierarchical control, the safety is ensured, and accurate temperature control is realized.

The utility model relates to the technical field of refrigerating systems, in particular to an expansion tank. The expansion tank comprises a tank body, a balloon and a flange assembly, the balloon is installed in the tank body, a cavity is formed in the balloon, the balloon and the tank body are coaxially arranged, the balloon is provided with an inner side close to the axis direction and an outer side away from the axis direction, the balloon is provided with an opening, and the side wall, forming the opening, of the balloon is bent towards the radial outer side to form a first turned edge; a convex rib is arranged on the side face, away from the cavity, of the first turned-over edge in a protruding mode, the flange assembly is connected with the first turned-over edge, and the convex rib abuts against the flange assembly in an interference mode. The flange assembly has the advantages that deformation is generated after the convex rib abuts against the flange assembly in an interference mode, and therefore the gap between the flange assembly and the first flanging can be filled with the convex rib, the leakproofness between the flange assembly and the first flanging is improved, and the problem of medium leakage is prevented.

A drying device for an expansion tank in a battery cooling system can be implemented in various configurations. In some configurations, the drying device includes an air-permeable, bag-like housing containing a drying agent. In another configurations, the drying device includes a dimensionally stable drying body formed from a sintered, extruded, or sprayed drying agent.

The invention discloses a liquid cooling system and a pressure control method thereof. The pressure control method comprises the following steps: acquiring a real-time environment temperature, a real-time input side temperature and a real-time input side pressure; when the liquid cooling system enters a first liquid supplementing state, the real-time input side temperature and the real-time environment temperature are compared to confirm the initial expansion temperature; calculating a real-time temperature difference value between the real-time input side temperature and the initial expansion temperature; the real-time input side pressure is compared with a preset input pressure threshold value, the real-time temperature difference value is compared with a preset temperature difference threshold value, and the working state of the pressure adjusting mechanism is adjusted according to the comparison result; according to the method disclosed by the invention, through real-time monitoring and dynamic adjustment, the system pressure of the liquid cooling system is always maintained in a suitable operation interval; and meanwhile, the demand on the volume of the expansion tank is remarkably reduced by actively adjusting the pressure, so that the overall volume of the liquid cooling system is effectively reduced, the material cost and the manufacturing cost are directly reduced by reducing the volume demand of the expansion tank, and the market competitiveness of the product is improved.

The invention provides a skid-mounted ship high-temperature fresh water cooling device and system, the skid-mounted ship high-temperature fresh water cooling device comprises an outfitting frame and system equipment integrally mounted on the outfitting frame, and a hoisting part is arranged on the outfitting frame. The system equipment at least comprises a fresh water generator, a main engine cylinder sleeve water cooler, a main engine cylinder sleeve water pump, a main engine cylinder sleeve water preheating pump, a main engine cylinder sleeve water preheater, dosing equipment and a system pipeline. The system pipeline is connected with all the system devices and comprises a main inlet and a main outlet, and a first external connector and a second external connector are arranged between the main inlet and the main outlet; the main inlet is used for being connected with a main engine cylinder sleeve outlet, the main outlet is used for being connected with a main engine cylinder sleeve inlet, the first external connector is used for being connected with a high-temperature expansion water tank, and the second external connector is used for being connected with a clean water cabin. Integrated design of ship high-temperature fresh water cooling related equipment is achieved, the ship high-temperature fresh water cooling related equipment can be independently assembled and debugged and integrally hoisted and installed, the on-site workload is reduced, the construction difficulty is lowered, and the efficiency is improved.

An expansion tank for a battery cooling system may include a tank housing composed of a plastic, a first receptacle, a dryer cartridge positively received in the first receptacle, a first valve via which air is released from the expansion tank into an environment when there is excess pressure in the expansion tank, and a second valve via which fresh air from the environment enters the expansion tank when there is a vacuum in the expansion tank. The tank housing may include a first shell and a second shell connected to the first shell. The first receptacle may be disposed in at least one of the first shell or the second shell.

The utility model discloses an anti-overflow expansion tank and an anti-oil-overflow refrigeration temperature control system, the anti-overflow expansion tank comprises an expansion tank main body, the expansion tank main body is provided with a liquid adding port, the expansion tank is provided with a first interface and a second interface, the anti-overflow expansion tank further comprises an exhaust valve and a one-way valve, the first interface is connected with an inlet of the exhaust valve, and an outlet of the exhaust valve forms an exhaust port of the expansion tank; an outlet of the one-way valve forms a main outlet of the expansion groove; comprising the anti-overflow expansion tank and further comprises a medium outlet and a medium inlet, and the medium inlet is sequentially connected with a cold storage tank, a circulating pump, a plate heat exchanger, a compressor, an oil separator, a condenser, a drying filter and an expansion valve through pipelines, then enters the plate heat exchanger and is connected to the medium outlet; by modifying a common expansion tank, heat-conducting oil overflowing from the expansion tank due to backward flowing can continuously stay in the expansion tank, so that the working environment is not polluted, the waste of the heat-conducting oil is avoided, and waste oil is avoided.

The utility model discloses a waterproof hammer diaphragm type component of an expansion tank in the technical field of expansion tanks, which comprises an expansion tank main body, the bottom of the expansion tank main body is fixedly connected with supporting legs, and the waterproof hammer diaphragm type component can guide a diaphragm component to be placed in the expansion tank main body through the sliding connection between a guide strip and a guide plate. The mounting position of the bottom of the diaphragm assembly can be limited through clamping of the bottom of the limiting plate and the expansion tank body, the mounting position of the top of the diaphragm assembly can be limited through clamping of the extension strip and the built-in ring, the stability of the diaphragm assembly in the mounting and using process is improved, follow-up quick disassembly and replacement of the diaphragm assembly are facilitated, mixing of gas and water is avoided, and the service life of the diaphragm assembly is prolonged. Normal adjustment of the pressure of the expansion tank system is guaranteed, buffer protection can be conducted on one side of the diaphragm assembly through the spring telescopic rod and the arc-shaped elastic piece, therefore, pressure can be buffered together with elastic deformation of the diaphragm assembly, and the water hammer preventing effect is enhanced.

The application discloses an ammonia dual-fuel ship air conditioning refrigeration system and method and a ship, and relates to the field of ship air conditioning refrigeration systems. The system comprises an air conditioning cold water unit system, a liquid ammonia cold energy recovery heat exchanger system, an air conditioning refrigerant water expansion tank and an air conditioner. The air conditioning cold water unit system, the liquid ammonia cold energy recovery heat exchanger system, the air conditioning refrigerant water expansion tank and the air conditioner are connected through circulating pipelines and corresponding valves. The air conditioning cold water unit system and the liquid ammonia cold energy recovery heat exchanger system are arranged in an ammonia fuel supply equipment room, and the air conditioning refrigerant water expansion tank and the air conditioner are arranged inside a driver's cabin. An air conditioning refrigerant water circulating pump is arranged on the circulating pipeline in the ammonia fuel supply equipment room. The application recovers and utilizes the cold energy of low-temperature stored ammonia fuel, solves the problem that a ship is difficult to maintain and replace refrigerant in the European Union region, saves electric energy of a dual-fuel ship, and plays a role in energy saving and emission reduction.

The invention relates to a liquid expansion tank (1) having a receiving space (3) for receiving the coolant and an overflow space (4) for receiving excess coolant from the receiving space (3). The receiving space (3) and the overflow space (4) are then fluidically connected via an overflow channel (5). Figure for abstract: Fig. 1

This utility model relates to the field of battery anode material premixing technology and discloses a lithium-ion battery anode material premixing device, including a stirring tank and a drive motor. By controlling the lower stirring rod to connect with the upper stirring rod, and further controlling the drive motor to make the upper and lower stirring rods rotate synchronously, the second scraper will scrape the material on the filter plate, and the material will be crushed by the roller. The material falling off the filter plate will enter the interior of the stirring tank. When the hopper is opened, the material will be stirred by the first scraper and scraped out of the hopper, thereby increasing the mixing degree of the material. By controlling the matching of the buckle and the buckle seat, and making the stirring tank, filter plate and expansion tank stacked in sequence, the device can be assembled. In use, by pulling the buckle to release the buckle from the buckle seat, the expansion tank can be removed from the stirring tank. Furthermore, the internal components of the device can be disassembled, which facilitates the cleaning and maintenance of the device.

The application provides a whole heat pump, and relates to the technical field of heat pumps.The whole heat pump comprises a box, a fan, a compressor and a water module assembly.The box is provided with a first chamber and a second chamber which are spaced apart from left to right, and the fan is arranged in the first chamber.The water module assembly comprises a water module electric control box, an expansion tank and an electric heater, the water module electric control box is arranged on the right side of the second chamber, the expansion tank is arranged on the back side of the second chamber, the compressor is arranged on the left side of the second chamber, and the electric heater is arranged on the front side of the second chamber.The whole heat pump provided by the application has a more compact structure and occupies less space.

The utility model discloses a kind of duplex ball valves with non-return function, belong to ball valve technical field, including duplex ball valve body, one end of the duplex ball valve body is equipped with non-return pipe by bolt, the outside of the non-return pipe is provided with protection mechanism, the outside of the non-return pipe is provided with moving groove, the inside of the non-return pipe is provided with expansion tank, the inner chamber of the non-return pipe is provided with rear conical plug, the inner chamber of the moving groove is slidably connected with movable ring. In the utility model, when the inside of non-return pipe flows fluid, fluid pushes conical plug post and the inner wall of rear conical plug separate to make fluid flow, when the inside of non-return pipe does not flow fluid, the elastic force of spring is used to drive conical plug post reset, so that conical plug post is plugged to the inner chamber of non-return pipe, avoid fluid reflux, in addition, spring is supported by first fixed column and second fixed column and is packaged, spring can be replaced, and practicality is good.

The utility model discloses an expansion water tank for an automobile, and belongs to the technical field of component devices for automobiles. The expansion water tank for the automobile comprises a water tank body and a mounting frame, and further comprises a connecting frame fixedly connected to the water tank body; the threaded groove is formed in the mounting frame; the inner pipe is arranged in the mounting frame, the inner pipe is communicated with the threaded groove, and the two ends of the inner pipe are located over the mounting frame; the locking bolt is in threaded connection with the threaded groove, and the locking bolt is used for connecting the mounting frame and the connecting frame; lubricating oil is injected into the inner pipe, so that the lubricating oil can be immersed into the locking bolt and the thread groove; through the arrangement of the inner pipe, the threads can be soaked in lubricating oil, when water vapor intrudes subsequently, the threads can be effectively prevented from being rusted, follow-up dismounting is facilitated, through the arrangement of the liquid inlet pipe and the plastic opening, the amount of the added lubricating oil can be clearly known, and the situation that an engine room is dirty due to the fact that too much lubricating oil is added is avoided.

The invention relates to the technical field of boilers, and provides a drain flash tank which comprises a flash tank body and a heat exchange box. A heat exchange box is installed on one side of the flash tank, a water inlet is formed in the top end of the heat exchange box, a connecting pipe is installed on one side of the top end of the flash tank, and an auxiliary structure is arranged at the bottom end in the flash tank; the auxiliary structure comprises a mounting seat, the mounting seat is mounted at the bottom end in the flash tank, a rotating blade is mounted at the top end of the mounting seat, a fixing sleeve is mounted on the outer side of the rotating blade, a water outlet is formed in one side of the fixing sleeve, and an annular pipe is mounted at the top end of the mounting seat. The centrifugal force generated by rotation of the rotating blades can throw hydrophobic liquid with higher density to the inner wall of the flash tank, and steam gas with lower density gathers to the center under the action of the centrifugal force, so that vapor-liquid two-phase separation is more thorough, the water drop, namely water carrying phenomenon, carried in steam is reduced, and the quality of recycled steam is improved.

The utility model discloses a heat conduction oil system which comprises an expansion tank, an oil supply pipeline, an oil return pipeline, a cooler, a collecting container, a single expansion pipe and an auxiliary exhaust pipe. The oil supply pipeline and the oil return pipeline are respectively connected with the expansion tank, the oil supply pipeline is provided with an oil supply valve, and the oil return pipeline is provided with an oil return valve; the heat-conducting oil can enter the expansion tank through the oil supply pipeline and circulate in the expansion tank, so that the temperature of the heat-conducting oil in the expansion tank is increased, low-boiling-point substances in the heat-conducting oil are gasified, and the pressure of the expansion tank is increased; the cooler is connected with a gas outlet of the expansion tank through a first pipeline, and the cooler is connected with the collecting container through a second pipeline; and gasified low-boiling-point substances are conveyed to a cooler for cooling through a gas outlet of the expansion tank, and then are conveyed to the collecting container. According to the conduction oil system provided by the utility model, the content of low-boiling-point substances in the conduction oil can be obviously reduced, and the normal work of the system is ensured.

The invention relates to the technical field of unmanned aerial vehicles, in particular to an eVTOL motor arm combined cooling system structure which is arranged in a motor arm, lifting force systems are installed at the two ends of the motor arm correspondingly, and each lifting force system comprises a motor installed on the motor arm and a propeller fixedly installed at the output end of the motor. Motor controllers are mounted at the two ends of the motor arm; the cooling system structure comprises a water pump, an expansion water tank, a radiator and a cooling water pipe which are arranged in the motor arm, the water pump, the expansion water tank, the radiator, the motor controller and the motor are communicated through the cooling water pipe to achieve cooling of the motor controller and the motor. An air channel is formed in the motor arm, downward airflow formed when the propeller rotates enters the motor arm from the air channel and then is blown to the radiator, the air velocity on the surfaces of fins of the radiator is increased, and the radiating efficiency of the radiator is improved. The cooling device has the advantages of light weight, low cost and good cooling effect.

The present application belongs to the technical field of industrial circulating water, and relates to a method for reducing the operation pressure of a closed circulating water system, which comprises a circulating water pump and a heat exchange device connected through a circulating water pipeline to form a closed loop, and is connected to an expansion tank through a connecting pipeline and a connecting valve in a breakable manner; the method comprises the following steps: a system starting step: starting the circulating water pump to form a stable flow of circulating water in the closed loop; a connecting opening step: after the flow of circulating water is stabilized, the connecting valve is opened to form a pressure connection loop between the expansion tank and the closed circulating water system; a pressure regulating step: the operation pressure of the closed circulating water system is controlled within a safe pressure range by regulating the gas pressure in the expansion tank; a shutdown isolation step: when the closed circulating water system needs to be shut down, the connecting valve is closed to cut off the pressure connection between the expansion tank and the closed circulating water system, and then the circulating water pump is closed.

The utility model discloses a hydraulic module and a heat pump system, and relates to the technical field of cold and hot water supply equipment.The hydraulic module comprises a box body and an expansion tank, the box body is provided with a mounting cavity, the outer side face of the box body is provided with an access hole communicating with the mounting cavity, the expansion tank is arranged in the mounting cavity, and an inflation inlet of the expansion tank corresponds to the access hole; the access hole is formed in the outer side face of the box body, the expansion tank is arranged in the mounting cavity, and the inflation inlet in the expansion tank can correspond to the access hole, so that when the pressure of the expansion tank needs to be detected or the expansion tank needs to be inflated, detection equipment can be directly in butt joint with the inflation inlet in the expansion tank through the access hole; according to the hydraulic module, the pressure of the expansion tank can be detected through the hydraulic module, and an external air source can be in butt joint with the inflation inlet in the expansion tank through the access hole to restore the pressure of the expansion tank to a default value set when the expansion tank leaves a factory, so that the pressure of the expansion tank can be conveniently detected or adjusted without disassembling a panel on the hydraulic module.

The utility model discloses a low-boiling-point substance collecting device of a heat conduction oil heating furnace. The low-boiling-point substance collecting device comprises an expansion tank and an oil-gas separator, the oil-gas separator is in fluid communication with an inner cavity of the expansion tank through an expansion pipeline, an exhaust port is formed in the top of the expansion tank, the low-boiling-point substance ascending pipe is in fluid communication with the inner cavity of the expansion tank through the exhaust port, and the condensate descending pipe and the low-boiling-point substance ascending pipe are arranged at intervals; the condensing pipes are arranged between the low-boiling-point substance ascending pipe and the condensate descending pipe, each condensing pipe is obliquely arranged from the low-boiling-point substance ascending pipe to the condensate descending pipe from high to low, and the low-boiling-point substance ascending pipe, the condensing pipes and the condensate descending pipe are in fluid communication. The device further comprises a low-boiling-point substance condensate recovery tank, and the condensate descending pipe is communicated with the low-boiling-point substance condensate recovery tank through a condensate recovery pipeline. Low-boiling-point substances are continuously and rapidly collected on line, the heat transfer performance of heat conduction oil is improved, the heating furnace operates stably, and the heat efficiency is high.

The utility model discloses an integrated battery pack and electric engineering machinery, the integrated battery pack includes: battery pack body, cooling circulation waterway and expansion water tank, wherein expansion water tank sets up at the horizontal highest end of battery pack body, and expansion water tank has the gas outlet, and the gas outlet is connected with the water outlet main pipe waterway of cooling circulation waterway, and expansion water tank is used for carrying out the degassing of cooling circulation waterway through the gas outlet. The integrated battery pack and electric engineering machinery can carry out the degassing of cooling circulation waterway through the expansion water tank set up at the horizontal highest end of battery pack body, and the air in cooling circulation waterway is discharged outside the system, so that in the case that the water cooling unit is arranged at the low vehicle end or the charging seat end, the degassing function of cooling circulation waterway in the battery pack for battery replacement can be realized, thereby the heat exchange capacity of the battery pack is improved.