Patents
Literature
Patsnap Copilot is an intelligent assistant for R&D personnel, combined with Patent DNA, to facilitate innovative research.
Patsnap Copilot

2749results about How to "Improve heating effect" patented technology

Air-conditioner internal and external unit cleaning method

The invention discloses an air-conditioner internal and external unit cleaning method. The method comprises the steps that an indoor heat exchanger is controlled to enter a frosting mode; operation frequency of an air-conditioner, the opening degree of a throttling device and the rotating speed of an indoor fan are adjusted to enable evaporating temperature of the indoor heat exchanger to be kept within the preset range and the surface of the indoor heat exchanger to be frosted; frosting of the indoor heat exchanger lasts for time t1, later, frequency of a compressor is reduced, a four-way valve is controlled to be reversed, an outdoor heat exchanger enters a frosting mode, and meanwhile, the indoor heat exchanger is defrosted; the operation frequency of the air-conditioner, the opening degree of the throttling device and the rotating speed of an outdoor fan are adjusted, the evaporation temperature of the outdoor heat exchanger is kept within the preset range, and the surface of the outdoor heat exchanger is frosted; frosting of the outdoor heat exchanger lasts for time t2, the compressor is controlled to be shut down, and the indoor fan and the outdoor fan are kept starting until cleaning is completed. According to the air-conditioner internal and external unit cleaning method, the problem that in the prior art, the surface of the heat exchanger is cleaned through condensate water, and the effect is poor can be solved.
Owner:QINGDAO HAIER AIR CONDITIONER GENERAL CORP LTD

Enhanced vapor injection air-conditioning circulating system and control method thereof

The invention relates to a central air-conditioning system, in particular to a duct air conditioner, namely an enhanced vapor injection air-conditioning circulating system. A vapor injection side electronic expansion valve of the system is subject to discharge superheat control instead of vapor injection superheat control; high discharge superheat is guaranteed, and heating capacity of the system can be further improved by vapor injection; the system is especially applicable to variable frequency compressors; high heating capacity is kept even under different operating frequencies; the system operates stably and fluctuates little. The enhanced vapor injection air-conditioning circulating system comprises a controller, a compressor, a four-way valve, a vapor-liquid separator, an economizer, a solenoid valve and a coolant pipe. The compressor is a variable frequency compressor. The economizer is a plate economizer. The electronic expansion valve controls vapor injection. The vapor injection electronic expansion valve is subject to discharge superheat control instead of vapor injection superheat control; accordingly, high discharge superheat is guaranteed, and heating capacity of the system is further improved by vapor injection. The system is especially applicable to variable frequency compressors; the heating capacity is kept even under different operating frequencies; the system operates stably and fluctuates little.
Owner:QINGDAO HISENSE HITACHI AIR CONDITIONING SYST

Method for controlling opening of electronic expansion valve in heat pump water heater system

The invention discloses a method for controlling the opening of an electronic expansion valve in a heat pump water heater system, and aims to provide a control method for allowing a system to avoid an area in which the air suction degree of superheat drops suddenly in the running process and allowing the coefficient of performance (COP) of the system to keep a high level. The method comprises thefollowing steps of: setting the optimum value of the change rate delta T/delta t of the air suction degree of superheat, and setting the initial opening of the expansion valve as 80 percent of total opening; taking a temperature difference between an average temperature value at an air suction port of a compressor and the saturated evaporating temperature as the air suction degree of superheat when the compressor runs to the state of the stable running of the system; measuring and calculating the air suction degree of superheat at the interval time delta t; calculating the change rate of the actual air suction degree of superheat according to the adjacent two-time air suction degree of superheat, comparing with the set optimum value of the change rate of the air suction degree of superheat, and when the change rate of the actual air suction degree of superheat is less than or equal to A, reducing the opening of the expansion valve; when the change rate of the actual air suction degreeof superheat is more than 0, increasing the opening of the expansion valve; and when the change rate of the actual air suction degree of superheat is more than A and is less than or equal to 0, maintaining the current running state.
Owner:TIANJIN UNIV OF COMMERCE

Image recognition technology-based air source heat pump defrosting system and control method thereof

InactiveCN101929755AReduce false defrost actionReduce defrost lossCorrosion preventionCompression machines with reversible cycleFrostSystem structure
The invention discloses an image recognition technology-based air source heat pump defrosting control method and a system, which belongs to the application field of an air conditioner heat pump technology. Based on the original system structure of the air source heat pump, a camera [7] is arranged in the middle of the outer part of an outdoor heat exchanger [3] so as to shoot the frost distribution on the surface of the outdoor heat exchanger [3]; the frosting condition on the surface of the outdoor heat exchanger is shot in real time during the heating operation of the heat pump unit, the frosting area of the surface of the outdoor heat exchanger is acquired by using the image recognition technology and the frosting operation of the heat pump unit is controlled accordingly. Compared with the traditional air source heat pump defrosting control technology, the invention effectively overcomes the defects that the frost of the outdoor heat exchanger of the heat pump unit is not removed thoroughly, the defrosting is performed when no frost exists and defrosting is mistakenly performed due to dust accumulating on the surface of the heat exchanger, reduces the defrosting loss of the heat pump unit, improves the heat performance of the unit and is particularly effective in the areas where the outdoor heat exchanger of the air source heat pump unit suffers from severe frosting.
Owner:NANJING UNIV OF SCI & TECH

Air conditioner and defrosting control method thereof

The invention relates to an air conditioner and a defrosting control method thereof. According to the defrosting control method, whether defrosting control needs to be conducted or not is judged by the way of judging the relation between outdoor environment temperature and outdoor coiled tube temperature, and the optimization time point for entering in the defrosting control can be accurately judged. After the defrosting control is conducted, the frequency of a compressor is changed, and after switching frequency is reached, a four-way valve is directly switched to conduct defrosting control. After defrosting is completed, the frequency of the compressor is changed, and after the switching frequency is reached, the four-way valve is directly switched so that defrosting operation can be achieved. By means of the air conditioner and the defrosting control method thereof, the precision for entering in and exiting out of defrosting can be guaranteed, meanwhile, due to the fact that halting can not occur to the compressor in the defrosting process, heating capacity attenuation caused by halting of the compressor is reduced, the defrosting cycle is shortened, and the heating comfort and the heating performance of the air conditioner are improved.
Owner:广东科龙嘉科电子有限公司

Solar phase change heat storage wall and ventilation system provided with same

The invention provides a solar phase change heat storage wall and a ventilation system provided with the same. The solar phase change heat storage wall is formed by connecting a high-temperature phase change layer, a medium-temperature phase change layer and a low-temperature phase change layer sequentially, wherein the phase change temperatures of the high-temperature phase change layer, the medium-temperature phase change layer and the low-temperature phase change layer are set from high to low. A glass cover plate is arranged on the south side of the outer wall of the ventilation system; the rest part of the ventilation system is composed of an enclosure structure; an outdoor air inlet is formed in the upper part of the north side of the outer wall; and an outdoor air outlet is formed in the upper part of the south side. The solar phase change heat storage wall is positioned in the outer wall and close to the glass cover plate; the high-temperature phase change layer faces south; and an upper vent hole and a lower vent hole are formed in the upper part and lower part of the solar phase change heat storage wall respectively. A hot water system penetrates through the solar phase change heat storage wall to perform heat exchange. The solar phase change heat storage wall can overcome shortcomings of a conventional heat collection wall, has the advantages of good heat storage capability, diversified functions, simplicity for operation and no energy consumption, can achieve the effects of cooling by ventilation and domestic water heating in summer, and can be used for providing heat in winter, thereby having good application prospects.
Owner:陕西中为能源技术有限公司

Air conditioner and defrosting control method thereof

The invention belongs to the technical field of air conditioners, and aims at solving the problems that when an existing air conditioner conducts defrosting, the optimal defrosting mode cannot be selected according to the outside temperature condition and the thickness of a frost layer on an air conditioner outdoor unit. Accordingly, the invention provides an air conditioner and a defrosting control method thereof. The method comprises the following steps that the outdoor environment temperature and the first preset temperature are compared; if the outdoor environment temperature is larger than or equal to the first preset temperature, the air conditioner is controlled for bypass defrosting; if the outdoor environment temperature is smaller than the first preset temperature, whether the thickness of the frost layer on the air conditioner outdoor unit meets the preset condition or not is judged; if the thickness of the frost layer meets the preset condition, the air conditioner is controlled for bypass defrosting; and if the thickness of the frost layer does not meet the preset condition, the air conditioner is controlled for refrigerating defrosting. By means of the air conditioner and the defrosting control method thereof, the optimal defrosting mode can be adopted under the situation that the outdoor environment temperature is high or low or the frost layer on the air conditioner outdoor unit is relatively thick or thin, the comfort of the indoor environment is guaranteed, and the air conditioner heating effect is improved.
Owner:QINGDAO HAIER AIR CONDITIONER GENERAL CORP LTD +2

Frequency increasing method and system for variable frequency air conditioner

The invention discloses a frequency increasing method and system for a variable frequency air conditioner. The frequency increasing method comprises the steps that the environment temperature of the environment where the variable frequency air conditioner is located and the set temperature set by a user are acquired; whether an absolute value of a difference value between the environment temperature and the set temperature is larger than a temperature threshold value is judged; if yes, the first frequency increasing speed of a compressor is calculated through a fuzzy control algorithm according to the environment temperature and the compressor current, and the operation frequency of the compressor is increased according to the first frequency increasing speed; if not, the operation frequency of the compressor is increased according to the preset second frequency increasing speed; the first frequency increasing speed is higher than or equal to the second frequency increasing speed. According to the frequency increasing method and system, the frequency increasing speed of the compressor can be quickly increased to achieve the purpose of quick refrigerating or heating, and therefore great convenience is brought to a user.
Owner:SHENZHEN SKYWORTH AIR CONDITIONING TECH CO LTD

Upward-downward air supply double cross-flow air conditioner indoor unit

The invention discloses an air conditioner indoor unit. The air conditioner indoor unit comprises a base, a mounting shell, a back plate, a front panel, a lower volute fan assembly, an upper volute fan assembly and an evaporator assembly, wherein the base, the mounting shell, the back plate and the front panel define an accommodating space; the lower volute fan assembly is arranged inside the accommodating space and comprises a lower fan, a first volute and a second volute, and a lower air duct is defined between the first volute and the second volute; the upper volute fan assembly is arranged above the lower volute fan assembly and comprises an upper fan, a first upper volute and a second upper volute, and an upper air duct is defined between the first upper volute and the second upper volute; the evaporator assembly is arranged inside the accommodating space and is constructed in a mode that after the evaporator assembly exchanges heat with air entering the accommodating space from a return air inlet of the back plate, the air is guided respectively by the upper fan and the lower fan to enter the lower air duct and the upper air duct. The upward-downward air supply double cross-flow air conditioner indoor unit is high in heating efficiency and low in energy consumption and use costs.
Owner:GD MIDEA AIR-CONDITIONING EQUIP CO LTD

Defrosting control method for air-conditioning system

The invention discloses a defrosting control method for an air-conditioning system, which comprises the following steps of: defining three defrosting running modes, namely a drying mode, a general mode and a high-humidity mode; formulating different defrosting entry conditions on the three modes sequentially according to the complexity of frosting; and when the air-conditioning system is energized and operates, executing the following defrosting control processes: a, when an air-conditioning outdoor unit electrifies and enters a heating running mode for the first time, setting the high-humidity mode as the defrosting running mode; b judging whether the air-conditioning system meets the defrosting entry conditions or not, if so, executing the subsequent process, and otherwise, repeating the current judging process; c, executing the defrosting operation; and d, after the defrosting is finished, determining what kind of the defrosting running mode to be executed next time according to the current defrosting time, and returning the process b. By the defrosting control strategy, the problems of defrosting error and incomplete defrosting in high-humidity areas can be saved, the energy is saved, and the heating effect is improved.
Owner:HISENSE (SHANDONG) AIR CONDITIONING CO LTD

Frequency conversion control method for heat pump water heater

The invention relates to a frequency conversion control method for a heat pump water heater. The frequency conversion control method for the heat pump water heater is characterized by comprising the following steps of: performing frequency conversion control on a compressor of the heat pump water heater; performing frequency conversion control on a throttle mechanism of the heat pump water heater; performing frequency conversion control on a defrosting mechanism of the heat pump water heater; and performing frequency conversion control on an exhaust temperature of the heat pump water heater. The frequency conversion control method for the heat pump water heater has the advantages of high heating speed, few start-stop times, small temperature fluctuation of a water tank and energy conservation. At a high ambient temperature, the frequency of the compressor can be reduced and the circulating flow quantity of a system can be reduced, so that the suction pressure is reduced and the stable operation of the compressor is guaranteed. At a low ambient temperature, the circulating flow quantity of the system is increased by increasing the frequency of the compressor and the opening degree of an electronic expansion valve, the exhaust temperature is reduced and the compression ratio is reduced, so that the compressor can operate stably. In the defrosting process, the defrosting time is greatly shortened by increasing the circulating flow quantity of the system; and the frost can be removed completely, without the problem that the frost is accumulated into ice.
Owner:JIANGSU TENESUN ELECTRICAL APPLIANCE

Compressor and air conditioner

The invention provides a compressor. According to the compressor, a low-pressure cylinder, a first high-pressure cylinder and a second high-pressure cylinder are arranged in an overlapped way, and separation plates are arranged between two adjacent cylinders; the first high-pressure cylinder and the second high-pressure cylinder are both arranged at a same side of the low-pressure cylinder or respectively arranged at two sides of the low-pressure cylinder; a lower flange is disposed at the downside of the low-pressure cylinder, the first high-pressure cylinder and the second high-pressure cylinder; the first high-pressure cylinder is inside provided with a first slip sheet, the second high-pressure cylinder is inside provided with a second slip sheet, and the low-pressure cylinder is inside provided with a third slip sheet; the first high-pressure cylinder and the second high-pressure cylinder are arranged in a parallel way and then are connected with the low-pressure cylinder in a serial way; the first high-pressure cylinder or/and the second high-pressure cylinder is/are a capacity-variable cylinder; and the low-pressure cylinder is taken as a first-stage compression cylinder. The invention also relates to an air conditioner. By employing the compressor and the air conditioner disclosed by the invention, the quantity of working cylinders of a multi-cylinder compressor is convenient to adjust.
Owner:GREE ELECTRIC APPLIANCES INC +2

Frost-less air-source heat pump hot water unit and proportional-integral-differential control method for same

The invention discloses a frost-less air-source heat pump hot water unit and a proportional-integral-differential control method for the same. The proportional-integral-differential control method includes performing computation according to received air temperature and humidity parameters, received air pressure parameters and received surface temperature parameters of an evaporator when outdoor temperature parameters which are transmitted by a temperature and humidity sensor and are received by a computation controller are lower than 0 DEG C, controlling the opening of an electronic expansion valve according to a computation result and regulating the surface temperature of the evaporator by means of increasing or reducing the opening of the electronic expansion valve so that the surface temperature of the evaporator is constantly higher than a frost formation point; and enabling a silicon-controlled power regulator to judge a suction superheat degree of a compressor according to received suction temperature and suction pressure of the compressor, increasing or reducing the power of an electric heater and maintaining that the suction superheat degree of the compressor only varies within a set value range. The frost-less air-source heat pump hot water unit and the proportional-integral-differential control method have the advantage that adjustment for the opening of the electronic expansion valve is matched with adjustment for the power of the electronic heater, so that the purpose of maintaining safe and efficient running of a system is achieved.
Owner:NANJING NORMAL UNIVERSITY +1

Defrosting method and system for air conditioner

The invention discloses a defrosting method and a defrosting system for an air conditioner. The defrosting method comprises the following steps of: 10, electrifying the air conditioner for running and heating; 20, judging, namely (A) judging whether the outdoor environmental temperature is smaller than and equal to first preset temperature, (B) judging whether continuous running time of a heating compressor reaches first preset time, and judging whether accumulative running time reaches second preset time, (C) judging whether the continuous running time of the heating compressor reaches third preset time, and making accumulative running time reach fourth preset time, (D) judging whether the temperature of a defrosting sensor Te or Tc is smaller tan and equal to second preset temperature, keeping the temperature for fifth preset time, and making the accumulative running time reach fifth preset time, and (E) judging whether to defrost manually; and 30, determine to perform timing defrost, automatically defrost, manually defrost or not defrost according to a judging result obtained in the step 20. By the scheme, the problems that when the air conditioner is used for heating, a heating effect is influenced due to a relatively long defrosting period, and the air conditioner cannot defrost, or defrosts after a long time because the environmental temperature is relatively low can be solved.
Owner:QINGDAO HAIER AIR CONDITIONING ELECTRONICS CO LTD +1

Control method for complete machine capability of variable-capacity multi-connected unit and control system therefor

The invention discloses a control method for complete machine capability of a variable-capacity multi-connected unit, comprising the followings: according to the working mode, indoor unit load and environmental temperature of the variable-capacity multi-connected machine, determining the number of compressors to be started and whether to start relief valves; monitoring whether exhaust pressure is larger than a set value, if so, according to the number of the started the compressors, the situation whether to start the relief valves and the failure frequency of the variable-capacity multi-connected unit, redetermining the number of the variable-capacity multi-connected unit and whether to start the relief valves and/or diluent cooling valves. The invention also discloses a control system for complete machine capability of the variable-capacity multi-connected unit, comprising an outdoor unit, the indoor unit, compressors, relief valves and diluent cooling valves, further comprising a control module, a monitoring module and a correcting module. In the invention, by monitoring exhaust pressure to automatically alter complete machine capability output, phenomena of overhigh exhaust pressure and system alarm halt caused by environment temperature variation do not occur, thus achieving good cooling and heating effects.
Owner:HAIER GRP CORP +1

Self-compensation control method and system for air volume of air conditioner, and air conditioner

The invention relates to the field of household appliance control, in particular to a self-compensation control method and system for the air volume of an air conditioner, and the air conditioner. The method comprises the following steps: acquiring the current filth blockage degree of a dust filtering screen of the air conditioner; acquiring the corresponding compensation for the rotating speed of a draught fan according to the current filth blockage degree; acquiring the target rotating speed of the draught fan according to the compensation for the rotating speed of the draught fan; and controlling the running of the draught fan according to the target rotating speed of the draught fan. According to the method provided by the invention, the filth blockage degree of the dust filtering screen of the air conditioner is detected, and the corresponding compensation is made for the rotating speed of the draught fan, so that the air volume of the air conditioner can be prevented from being lower than that outputted before filth blockage, and the air volume required by the system can still be outputted by the air conditioner in a dust-cumulated manner. Accordingly, not only are the refrigerating and heating effects of the air conditioner as well as the use comfort of a user improved, but also the energy-saving and environment-friendly properties are further achieved.
Owner:GD MIDEA AIR-CONDITIONING EQUIP CO LTD +1

Defrosting method of air conditioner

The invention discloses a defrosting method of an air conditioner. The method comprises the steps that S1. a heating mode of a compressor is carried out; S2. the fact that an outdoor fan is shut down at intervals is detected, and whether compressor accumulative operation time t reaches first preset time t1 is detected; S3. when t is larger than or equal to t1, a defrosting stage is carried out; S4. outdoor fan operation is detected, whether t is larger than second preset time t2 is detected, and the difference value delta T (delta T = T2 - T1) of the temperature T2 of an indoor heat exchanger and indoor environment temperature T1 is compared with a preset threshold value new delta T; S5. when t is larger than t2 and is smaller than third preset time t3, whether delta T is smaller than new delta T is judged; S6. when delta T is smaller than new delta T, the defrosting stage is carried out; S7. when t is larger than t3, whether delta T is smaller than new delta T + 2 DET C is judged; S8. if delta T is smaller than new delta T + 2 DET C, the defrosting stage is carried out; and S9. defrosting is over. According to the defrosting method, the operation that existing frost is removed, and when no frost exists, no processes are carried out can be achieved.
Owner:GD MIDEA AIR-CONDITIONING EQUIP CO LTD +1

Frequency control method, frequency control device, multi-split air conditioner and storage medium

The invention discloses a frequency control method, a frequency control device, a multi-split air conditioner and a storage medium. The frequency control method comprises the following steps that whenthe multi-split air conditioner is in the heating operation, a capability requirement identification value corresponding to each indoor unit in all indoor units in the running state, set temperatureand indoor environment temperature are acquired at interval preset time so as to determine the initial operating frequency of a compressor in each preset time; in each preset time, outdoor environmenttemperature is acquired; a target frequency correction coefficient within each preset time is determined according to the outdoor environment temperature; and the initial operation frequency within each preset time is corrected according to the target frequency correction coefficient so as to determine the target operating frequency of the compressor. According to the frequency control method, the frequency control device, the multi-split air conditioner and the storage medium, the problems that the accuracy of the tube temperature correction frequency of the middle of the indoor unit is lowand the needed time is too long are solved, and the effect of improving the heating capacity of the multi-split air conditioner is achieved.
Owner:GD MIDEA AIR-CONDITIONING EQUIP CO LTD +1

Backheating method and backheating structure for heat pump air conditioner

The invention discloses a backheating method and a backheating structure for a heat pump air conditioner, which can improve the performance of the air conditioner. The backheating structure comprises heat exchangers A and B, a compressor, and a throttling element connected between the heat exchangers A and B, wherein the heat exchanger B is connected with the compressor by an air suction pipe of the compressor; and a higher-temperature coolant in the throttling element performs heat exchange with a lower-temperature coolant in the air suction pipe of the compressor. In the backheating method and the backheating structure, the temperature of the coolant in the throttling element can be reduced by performing backheating in a throttling process, thereby retarding the evaporation of the coolant and the change of the dryness of the coolant, making more stable the flow regime of the coolant and reducing inevitable loss; and the dryness of the coolant at an outlet of the throttling element is reduced, namely, the degree of subcooling of the air conditioner is increased, so the cooling capacity of the air conditioner can be improved. The backheating method and the backheating structure for the heat pump air conditioner can improve the cooling or heating performance of the heat pump air conditioner; and the backheating structure is simplified to a certain extent so as to be convenient to manufacture and save the cost.
Owner:四川长虹空调有限公司

Control method of electronic expansion valve of indoor machine during refrigerating of convertible frequency air conditioner

ActiveCN102368009AEvaporating temperature fluctuations are reducedPrevent the opening from being too smallRefrigeration safety arrangementEngineeringElectronic expansion valve
The invention discloses a control method of an electronic expansion valve of an indoor machine during refrigerating of a convertible frequency air conditioner. The control method comprises the following steps of: 1, judging whether a microprocessor of the indoor machine (8) is in a heating standby state; 2, regulating the openness of the corresponding indoor electronic expansion valve (7) to reach 30-50 paces by the microprocessor; and 3, keeping the openness of the indoor electronic expansion valve (7) in the step 2 for 2-6min, regulating the openness of the corresponding indoor electronic expansion valve (7) by the microprocessor according to temperatures transmitted by a liquid pipe temperature sensor (9) and an indoor heat exchanger coil temperature sensor (11) every 15-35S in accordance with the following rules: the openness of the regulated indoor electronic expansion valve (7) is equal to the sum of the openness of the indoor electronic expansion valve (7) before the regulation and the openness of the regulation of the indoor electronic expansion valve (7), and the openness of the regulation of the indoor electronic expansion valve (7) is equal to (T3-Tmin-A)*E+delta(T3-Tmin)*F. Compared with the prior art, the control method disclosed by the invention has the characteristics of being suitable for a one-more air conditioner, being capable of effectively ensuring stable operation of the system and improving heating efficiency of the system, being low in energy consumption, and ensuring that the temperature change range of an indoor environment is smaller and the comfort degree of the indoor environment is higher.
Owner:NINGBO AUX ELECTRIC

Low-temperature heating method and low-temperature heating system for air conditioner

The invention provides a low-temperature heating method and a low-temperature heating system for an air conditioner. The air conditioner at least comprises an indoor unit, an outdoor unit, an indoor unit fan and a refrigerating system, wherein the refrigerating system comprises a compressor, a four-way valve, an indoor heat exchanger and an outdoor heat exchanger; a plurality of electric heaters which are connected in parallel are arranged in the indoor unit. The low-temperature heating method comprises the following steps: receiving a heating operation instruction and target regulation temperature set by a user; detecting the environment temperature of the indoor unit and the temperature of the indoor heat exchanger; controlling the quantity of electric heaters working among the plurality of electric heaters according to the difference between the target regulation temperature and the environment temperature, and the temperature of the indoor heat exchanger. According to the technical scheme, the heating effect of the air conditioner in the initial period of low-temperature heating operation can be improved, and the use experience of the user is improved.
Owner:GD MIDEA HEATING & VENTILATING EQUIP CO LTD +1
Who we serve
  • R&D Engineer
  • R&D Manager
  • IP Professional
Why Eureka
  • Industry Leading Data Capabilities
  • Powerful AI technology
  • Patent DNA Extraction
Social media
Try Eureka
PatSnap group products