57 results about "Coefficient of performance" patented technology

The invention relates to the technical field of heat exchangers, in particular to a collaborative design and control method, device and equipment for a heat exchanger and a storage medium, and the method comprises the steps that operation data of a target heat exchanger under at least one working condition are collected, and performance coefficient data meeting preset performance conditions are output through a multi-target collaborative optimization model; after operation is conducted according to the performance coefficient data, the flow value, the pressure value and the temperature value of the target heat exchanger are collected, and a corresponding adjusting instruction is determined; and based on the digital twin body, determining performance attenuation data and / or a fault diagnosis result, further generating an optimization instruction, and controlling the target heat exchanger. Therefore, the problems that in the related technology, under the variable load working condition, when the load deviates from a design point, the heat transfer and efficiency become poor due to fluid flow and flow velocity changes, vibration is caused by uneven flow, the temperature control precision is poor, and physical property changes and temperature pinch points are prone to occurring in a supercritical working medium are solved; the post-adjustment adaptability is poor, the performance is difficult to optimize, the response is slow, and potential safety hazards exist.

According to the variable-component high-temperature super heat pump device and the operation method, a non-azeotropic mixed working medium serves as a technical core of a unit, two sub-compression-type cycles are arranged, an intermediate storage tank is arranged between the two sub-cycles, and the working medium is stored in the intermediate storage tank or extracted into a heat pump cycle on the basis of the heating temperature; and equivalently, the charge quantity of each heat pump is controlled, so that'on-line mobile charge quantity 'is realized, shutdown for working medium recovery is avoided, and high COP (coefficient of performance), low compression ratio and reliable operation are kept in a full-temperature area. Due to the adoption of the variable-component device, compared with the prior art, the heat pump has the advantages of higher heating efficiency and energy conservation.

The present disclosure relates to improving the energy performance of CO2 capture. [Solution] A system for capturing carbon dioxide (CO2) from a CO2-containing gas stream, comprising an absorber for contacting the CO2-containing gas stream with an adsorbent, the adsorbent operable to capture CO2 from the CO2-containing gas stream in a first temperature range and release the CO2 in a second temperature range, a desorber for releasing the CO2 from the adsorbent, first and second heat pumps configured to recover heat for the desorber from both a condenser and at least one other point in the system, and the condenser temperature selected to maximize both the heat content of the condensate and the combined coefficient of performance of the first and second heat pumps to minimize the input energy requirements of the heat pump system.

The invention relates to a heat source determination method and system. The method comprises the steps that under the condition that a vehicle heat pump of a target vehicle absorbs heat from air to supply heat to a vehicle cabin, current heat supply parameters of the air are determined; wherein the heat supply parameters comprise the heat supply amount and the heat supply performance coefficient; reference heat supply parameters corresponding to the current environment temperature, the current air conditioner gear of the target vehicle and the current electric drive torque are inquired from the heat supply relation; wherein the heat supply relation comprises heat supply performance coefficients under different environment temperatures, air conditioner gears and electric drive torque combinations and heat supply quantities under different environment temperature and electric drive torque combinations; and according to the current heat supply parameters and the reference heat supply parameters, the future heat source of the vehicle heat pump of the target vehicle is determined. By adopting the method, the reliability and accuracy of heat source determination can be improved, and the heating efficiency of the vehicle heat pump is further improved.

The invention provides a solar energy and geothermal energy coupled heat supply control method and system and electronic equipment, and relates to the technical field of heat supply control, and the method comprises the steps that a first environment parameter representing the solar energy input intensity and a second environment parameter representing the underground heat source state are obtained; the solar heat supply heat is calculated according to the first environment parameter, and a geothermal heat exchange path is determined according to the second environment parameter; the performance coefficient of the ground source heat pump is calculated according to the soil average temperature corresponding to the geothermal heat exchange path, and the geothermal energy heat supply heat is calculated according to the performance coefficient and the heat pump input power; according to the matching degree between the heat supply demand and the solar heat supply heat, the target heat supply proportion between the solar heat supply heat and the geothermal heat supply heat is determined; and determining a target heat supply device based on the target heat supply proportion so as to carry out coupling heat supply control of solar energy and geothermal energy. According to the invention, cooperative coupling control of multiple energy sources is realized, and the overall energy efficiency and operation stability of the system are improved.

The application provides a control method and device of a multi-split air conditioner, the multi-split air conditioner, a storage medium and an electronic device, and the method comprises the following steps: detecting a temperature control instruction of a target room node of the multi-split air conditioner, wherein the multi-split air conditioner comprises a central control node and a plurality of room nodes; acquiring a current coefficient of performance (COP) of the target room node and predicting a future COP of the target room node after the target room node executes the temperature control instruction; and intervening in the execution of the temperature control instruction by an indoor unit of the target room node according to the current COP and the future COP. By adopting the scheme of the embodiment, the technical problem of low energy efficiency of the multi-split air conditioner in the related art is solved, and the energy efficiency optimization of the multi-split air conditioner is achieved.

This invention discloses an air-source-water source composite heat pump system and its operating method, solving the problems of low coefficient of performance and reliance on high-energy-consuming reverse-cycle defrosting methods in existing coupled systems, which are mostly simply set up in series or parallel. It has the beneficial effects of improving the coefficient of performance and ensuring the continuity and stability of industrial heating. The specific solution is as follows: An air-source-water source composite heat pump system includes a photovoltaic waste heat utilization unit: including a duct, the duct being placed on the back side of the photovoltaic module; a municipal greywater waste heat utilization unit: including a municipal greywater waste heat exchanger, the municipal greywater waste heat exchanger being connected to a municipal greywater pipeline; a low-temperature air-source-water source composite heat pump unit: including a photovoltaic-side evaporator, a first greywater-side evaporator, and a first-stage heating condenser located at the end of the duct, the municipal greywater waste heat exchanger being connected to the first greywater-side evaporator; and a high-temperature air-source-water source composite heat pump unit.

The invention discloses an automatic cascade absorption type refrigeration cycle system capable of recycling rectification heat and condensation heat in a cascade mode. Aiming at the core bottleneck of low thermodynamic efficiency of an automatic cascade absorption refrigeration cycle system, the invention innovatively aims at the characteristics that the adopted multi-element mixed working medium has a remarkable temperature slippage effect in a condensation process and a rectification process, and a heat dissipation temperature area in the rectification process is higher than that in the condensation process. By constructing a cascade recovery strategy of condensation heat and rectification heat, the thermal load of the circulating system is remarkably reduced, and then the performance coefficient is effectively improved. According to the system, rectification heat and condensation heat of the high-temperature and high-pressure side are recycled in a stepped mode through a solution of the circulating low-temperature and low-pressure side, and negative effects on other links of circulation are basically avoided under the condition that sufficient heat recycling is achieved. The thermodynamic efficiency of the self-cascade absorption type refrigeration cycle system can be remarkably improved, and the device has outstanding practical value in the field of deep low-temperature absorption type refrigeration driven by low-grade waste heat.

The invention relates to the technical field of heat exchanger data monitoring, in particular to a heat transfer monitoring and adjusting system and method for monitoring the state of a double-pipe heat exchanger. Comprising a sensing detection module, a data acquisition and preprocessing module, a performance calculation and feature extraction module, an intelligent decision and state evaluation module, a flow control and execution module, a man-machine interaction and alarm management module and a system integration and data bus module. According to the method, the flow redistribution strategy based on the performance coefficient is constructed, the flow is automatically cut off and the alarm is triggered when the performance degradation unit is detected, and meanwhile, the total flow is redistributed according to the performance coefficient proportion of the remaining online units, so that the high-performance heat exchanger obtains more flow resources; therefore, the overall heat transfer efficiency of the system can still be maintained under the condition of local faults, and intelligent optimization of flow and self-recovery of the system under the faults are achieved.

The invention discloses a dehumidification heat exchanger control method and system based on a mathematical model, and relates to the technical field of refrigeration air conditioners. A dehumidification heat exchanger control system based on a mathematical model comprises a data acquisition module, a data processing module, a curve drawing module, a model building module and a control reversing module. According to the method, the mathematical model is constructed according to the performance coefficient of the air conditioning system where the dehumidification heat exchanger is located in the reversing period, and the control system can comprehensively consider the actual working condition and the working state of the dehumidification heat exchanger through the maximum value obtained through calculation and the optimal reversing time corresponding to the maximum value; and the dehumidification heat exchanger is controlled to reverse under the condition that the performance coefficient of the system is kept in the optimal state, so that the requirement for adjusting the temperature and humidity of the space can be met, meanwhile, the high energy efficiency ratio of the air conditioning system is ensured, energy conservation and environmental protection are facilitated, and the control reasonability and practicability of the dehumidification heat exchanger control method and system are improved.

The application discloses an air conditioning system and a control method. The air conditioning system comprises a compressor and a control device. The compressor comprises a sliding valve, and one sliding position of the sliding valve corresponds to one content volume ratio of the compressor. The control device is configured to obtain a system volume ratio under a current working condition and a volume ratio correction value; obtain an optimal content volume ratio of the compressor; adjust the sliding position of the sliding valve; and obtain the volume ratio correction value through the following steps: setting a temporary volume ratio correction value and obtaining a performance coefficient of the air conditioning system corresponding to the temporary volume ratio correction value; gradually reducing the temporary volume ratio correction value by turns and obtaining the performance coefficient corresponding to the temporary volume ratio correction value until the performance coefficient obtained at the last time is less than the performance coefficient obtained at the previous time, and assigning the volume ratio correction value to the temporary volume ratio correction value obtained at the previous time. The application considers that the compressor is provided with an additional air inlet, the optimal content volume ratio is obtained by obtaining an optimized content volume ratio correction value, the sliding valve position is adjusted, and the compressor is operated at the best efficiency.

This invention discloses a refrigeration cycle method with liquid refrigerant compression, relating to the fields of refrigeration and gas liquefaction. The method includes a liquid tank, a liquid compression pump fixedly connected to one side of the liquid tank, and a main heat exchanger fixedly connected to the side of the liquid compression pump away from the liquid tank. The main heat exchanger is connected to an expander unit, a circulating gas compressor unit, and the liquid tank. The circulating gas compressor unit includes a circulating compressor and a circulating compression cooler. A cold box is provided outside the liquid tank, the liquid compression pump, the main heat exchanger, and the first and second expansion ends of the expander unit. This invention adds a liquid compression process to the refrigeration cycle, increasing the refrigerant pressure in both the liquid and gaseous states. Based on thermodynamics, a new refrigeration cycle method is created, reducing energy consumption during circulating compressed gaseous refrigerant, while simultaneously increasing energy recovery and utilization in multiple ways, improving the coefficient of performance (COP), and thus achieving the goal of reducing the total energy consumption of the refrigeration cycle.

The utility model relates to the technical field of air conditioners, in particular to an air conditioning system and a carrier. The air conditioning system comprises a refrigerant loop, a first heat exchange loop, a second heat exchange loop and a heat exchange device. The refrigerant loop comprises a compressor, a condenser, a throttling device and an evaporator which are connected in sequence, and the first heat exchange loop is in heat exchange connection with the refrigerant loop through the condenser; the second heat exchange loop is in heat exchange connection with the refrigerant loop through an evaporator, and the first heat exchange loop is in heat exchange connection with the second heat exchange loop through a heat exchange device. According to the air conditioning system, secondary heat exchange between the refrigerant loop and the first heat exchange loop and the second heat exchange loop is achieved through the condenser and the evaporator, heat exchange connection between the first heat exchange loop and the second heat exchange loop is achieved through the heat exchange device, heat loss is compensated, and the heat transfer efficiency is optimized; therefore, the performance coefficient of the whole system is improved, and the energy consumption is reduced.

This invention relates to a refrigeration system designed as Rotary Supercharger Ejector Refrigeration System to improve the coefficient of performance and to reduce mechanical complexity. The design ensures that the working fluid performs expansion work as it passes through the generator. On the other hand, it eliminates the need for subcooling the liquid entering the pump. The design allows conversion of the high-speed kinetic energy from the ejector's outlet stream into recoverable potential energy. Consequently, the cycle closely approaches the ideal cycle. The rotation of coils increases convective heat transfer between coils and the atmosphere and eliminates the need for a blower as well as a complex mechanical pump. In addition to coil-air heat exchange, the system can be thermally coupled with hot rotating bodies to absorb waste heat and generate effective cooling.

The application is suitable for the technical field of thermal management, and provides a control method and device of a heat pump system, a computer program product and a vehicle. The heat pump system is connected between a regenerator and an evaporator for controlling the temperature of a passenger cabin and / or a battery thermal management assembly through a first throttling valve. The regenerator is connected to an outdoor heat exchanger through a second throttling valve. The control method of the heat pump system comprises: determining a current operation mode of the heat pump system; and performing opening degree control on the first throttling valve and the second throttling valve respectively according to the current operation mode. The embodiments of the application can improve the performance coefficient of the heat pump system.

The utility model provides an active enhanced vapor injection heat pump based on photovoltaic and photo-thermal, which comprises a heat pump host module, a solar module and a hydraulic module, and photovoltaic power generation drives the heat pump to do work and generate heat which is used as domestic hot water or heating, so that power is saved to the maximum extent. A flow channel is designed on the back face of the photovoltaic panel, heat is absorbed through circulating water, heat generated by the photovoltaic panel is recycled, the temperature of the photovoltaic panel is reduced, the photovoltaic power generation efficiency is improved, and hot water absorbing the heat is accumulated in the energy storage water tank and serves as an external heat source for active enhanced vapor injection to improve the performance of the heat pump. An active enhanced vapor injection device is designed for a heat pump host module, and a refrigerant in an economizer absorbs heat of heat storage hot water and converts the heat into heating capacity, so that the heating capacity and the performance coefficient of the heat pump are greatly improved, and the technical bottleneck that the heat pump cannot be applied in an extremely low-temperature environment is solved.

According to the photovoltaic panel heat dissipation system and method coupled with the supercritical carbon dioxide heat pump, efficient thermal coupling is carried out on the photovoltaic module back plate and the micro-channel integrated heat exchanger at the evaporation end of the supercritical carbon dioxide heat pump, and a transcritical cycle working medium is utilized; a large amount of waste heat generated during operation of a photovoltaic panel is actively absorbed and transferred, so that the working temperature of the photovoltaic panel is remarkably reduced to 45-55 DEG C so as to improve the power generation efficiency by 10%-15%, meanwhile, the captured low-grade waste heat is upgraded into medium-high-grade heat energy at the temperature of 60-90 DEG C through heat pump circulation to be output and utilized, cooperative operation of photovoltaic power generation and waste heat recovery and quality improvement is achieved, and the power generation efficiency is improved. The comprehensive energy efficiency of the system exceeds 70%, the heating performance coefficient of the heat pump reaches 3.2-3.8, photovoltaic self-power-generation driving is mainly used, and the system has multiple benefits of reducing carbon emission, prolonging the service life of components and adapting to various heat using scenes.

The utility model relates to a coal-fired cogeneration system integrating double-circulation heat pump heat storage. The coal-fired cogeneration system comprises a steam turbine system, a heat supply network water heating system, a heat pump system and a storage tank heat storage and release system. The steam turbine system comprises a boiler (23), a superheater outlet of the boiler (23) is connected with an inlet of a third mixing valve (22), another inlet of the third mixing valve (22) is connected with a cold source outlet of an auxiliary superheater (17), and an outlet of the third mixing valve (22) is connected with an inlet of a high-pressure cylinder (28). On the basis of a traditional combined heat and power generation system, excessive electric energy is converted into heat energy to be stored and utilized by integrating a heat pump and a heat storage system. According to the system, the overall heating performance coefficient is improved through low-temperature heat pump circulation, the heat supply capacity is enhanced, and thermoelectricity decoupling and low-carbon flexible operation of a coal-fired cogeneration unit can be achieved.

The invention discloses an air-supplementing enthalpy-increasing heat pump system, and relates to the technical field of heat pump systems. An outlet of a compressor is sequentially connected with a condenser, a first expansion valve and an evaporator. The system is further provided with an air supply branch, the inlet end of the air supply branch is connected with a pipeline between the condenser and the first expansion valve, the outlet end of the air supply branch is connected with a middle air supply port of the compressor, and the second expansion valve is arranged at the inlet end of the air supply branch. The entropy production multi-objective optimization method comprises the following steps: 1, building a test bed, and collecting thermodynamic parameters; 2, establishing and correcting a system entropy production and performance coefficient calculation model; 3, determining a control variable and a security constraint; 4, carrying out data normalization processing, and constructing a comprehensive evaluation function; 5, performing iterative optimization, and outputting a Pareto optimal leading edge; and 6, screening control parameters, and verifying adaptability. According to the method, a comprehensive optimization index combining multi-process entropy production and COP is constructed, so that the system runs in an area with the highest performance coefficient and the lowest total entropy production in the compression process while avoiding liquid impact and overheating risks.

The utility model discloses a phase-change mixed heat-carrying direct-drive heat pump, which belongs to the technical field of energy conservation and environmental protection, and comprises a first flash evaporation unit, a second flash evaporation unit, a first condensation heat exchange unit, a second condensation heat exchange unit, a third flash evaporation unit and a fourth condensation heat exchange unit, an ejector is arranged between the second flash evaporation unit and the second condensation heat exchange unit, and a medium to be heated sequentially passes through the first condensation heat exchange unit and the second condensation heat exchange unit. The ejector is arranged between the second flash evaporation unit and the second condensation heat exchange unit and is coupled with a traditional direct heating machine, namely a flash evaporation and condensation combination, so that the temperature of water or a medium to be heated can be stably increased, the temperature of the water or the medium to be heated can be 15-30 DEG C higher than that of a flash evaporation medium, and the coefficient of performance (COP) can reach at least 2.0.

The utility model belongs to refrigeration and air conditioning technical field discloses a supercooling device, air conditioning system and car, supercooling device includes condenser structure and cooling medium flow structure, refrigerant can flow in condenser structure, and condenser structure includes condenser and first supercooler, and the export of condenser communicates with the entrance of first supercooler;Cooling medium can circulate and flow in cooling medium flow structure, and cooling medium is divided into two parts at the export of first cooling medium pipeline, and one part enters condenser and absorbs the heat of refrigerant through second cooling medium pipeline, and the other part passes through first supercooler through third cooling medium pipeline, and the temperature of refrigerant at condenser export is further reduced, and refrigerant is in lower enthalpy state before throttling, to realize higher unit mass refrigerating capacity of refrigerant, thereby improve the performance coefficient (COP) of refrigeration system, reach the effect that reduces energy consumption.

The application belongs to the technical field of double-source heat pump, and provides a control method of a double-source heat pump system. Various sensors are arranged on field equipment, collected data is transmitted to an edge gateway for classification and mapping, preprocessing is performed by aligning time stamps, filling in missing items and smoothing high-frequency fluctuations; the collected data is spliced into a feature vector, the error of linear regression is calculated, the candidate values of hyperparameters are selected, a loss function is defined in combination with the error, the corresponding performance coefficients of different heat sources are obtained, the consumption cost, the temperature difference of the heat source and the performance coefficient are taken as score calculation items, and a decision of switching the heat source is generated according to the score; the decision is sent to a field execution unit, smooth switching is performed through dynamic load compensation and preheating preparation, the previous heat source is closed after the switching is completed, a decision log is exported at a fixed time to calculate the performance coefficient error, the error conditions of different heat sources are analyzed, a warning threshold is set, and the weight of the score calculation item is adjusted according to the warning information.

A vehicle thermal management system includes a HVAC subsystem; a power electronics cooling subsystem; a plurality of heat recovery drive components; and a controller. The controller includes a required heat calculation module to calculate a required heat quantity for a heating operation of the HVAC subsystem. The controller includes a coefficient of performance (COP) calculation module to calculate a maximum COP of the HVAC subsystem in the heating mode and a heat recovery calculation module to calculate a maximum heat recovery quantity of the HVAC subsystem and a total sum of estimated heat recovery quantities recoverable from the plurality of heat sources. The controller also includes a power determination module to determine respective amounts of power input to the plurality of heat recovery drive components based on the total sum of estimated heat recovery quantities and the maximum heat recovery quantity.

The invention provides an absorption refrigeration system which comprises an evaporator, an absorber, a generator and a condenser, and the evaporator comprises an evaporator liquid storage tank; the absorber comprises an absorber liquid storage tank; wherein a separation chamber is arranged between the evaporator liquid storage tank and the absorber liquid storage tank, and the separation chamber is configured to receive the liquid refrigerant overflowing from the evaporator liquid storage tank and the diluted absorbent solution overflowing from the absorber liquid storage tank; wherein the absorption refrigeration system further comprises an overflow circulation loop, and the overflow circulation loop is configured to enable fluid overflowing into the separation chamber to be controllably recirculated to the generator. The absorption refrigeration system has a high coefficient of performance (COP).

The application discloses a kind of graphite heater heating performance fault detection method and system, it is related to heating system performance safety detection related field, this method includes: in graphite heater middle deployment detection array, trigger based on first-order sensing acquisition obtains first detection signal group, graphite heating geometric structure is coaxially arranged spiral channel, using modular heating unit;Determine first heating test period, execute periodic physical end test and based on analog detector heating simulation test, mutual test determines first performance coefficient;Determine second pulse test condition, execute power pulsation sequence test based on non-stable direct current output and analog test based on analog detector in physical end, mutual test determines second performance coefficient;Determine comprehensive performance coefficient and carry out test platform visualization.The technical problem that the precision of existing graphite resistance type heating process performance safety detection is limited is solved, and the technical effect of improving the accuracy of heater performance safety evaluation is achieved.

The invention discloses a hydrogen energy and natural energy heat pump heat supply and refrigeration integrated system and method, and relates to the technical field of hydrogen energy and natural energy heat pump heat supply and refrigeration integration. The heat pump heating module comprises the following steps that S1, carbon dioxide in air is absorbed through a refrigerant or the refrigerant and released into water; the carbon dioxide heat pump is used, and carbon dioxide is a clean refrigerant, has no destructive influence on the environment, is stable in chemical property, non-combustible, not easy to decompose at high temperature, does not generate harmful gas, is non-toxic, reduces threats to people due to leakage, is good in fluidity and has a relatively high evaporation latent heat value; compared with conventional refrigerants, the compression ratio of carbon dioxide is much smaller than that of common refrigerants, high performance coefficient and mechanical efficiency can be achieved, the high condensing temperature enables the exhaust temperature of a compressor to be high, and water at the high temperature can be obtained.

Systems and methods for monitoring an HVAC&R system employ a monitoring agent that uses observations of evaporator and condenser intake temperatures, evaporator discharge temperature, and a compressor input power parameter to learn operating characteristics of the HVAC&R system in newly maintained condition. Thereafter, the agent continuously or regularly computes a relative coefficient of performance (COP) for the system under subsequent observed ambient conditions, and relates the present instantaneous efficiency of the HVAC&R system under the observed ambient conditions to the instantaneous efficiency when the system was in newly maintained condition. The relative COP can be used to detect system degradation and quantify the energy usage and cost attributable to the degradation. The agent can take appropriate actions to prevent / minimize damage based on the degree of degradation detected, including shutting off power to the HVAC&R system. The monitoring agent can also be extended to other types of systems besides HVAC&R system.

The invention provides a self-adaptive control method of a vehicle air conditioning system, a heat management system and a vehicle, and the method comprises the following steps: collecting system operation parameters in real time, the parameters comprising an evaporator outlet refrigerant dryness value; whether the dryness value of the refrigerant is larger than a preset safety threshold value or not is judged; if the dryness value of the refrigerant is smaller than or equal to the safety threshold value, a safety control mode is started, and the opening degree of the electronic expansion valve is increased; if the dryness value of the refrigerant is greater than the safety threshold value, calculating a coefficient of performance (COP) value of the system in real time based on the collected system operation parameters; taking a coefficient of performance (COP) value of the system as an optimization target, and generating a control signal by adopting an extremum search control algorithm; and the opening degree of the electronic expansion valve is dynamically adjusted according to the control signal, so that the system automatically tracks and maintains the optimal energy efficiency point. According to the method, the system can adaptively search and operate at the energy efficiency highest point under the current condition under the changing working condition, so that the energy consumption minimization in the whole working condition range is realized.

This invention provides a performance testing method for a non-azeotropic refrigerant compressor, relating to the field of compressor testing technology. The method accurately verifies the cooling capacity and coefficient of performance (COP) of a non-azeotropic refrigerant compressor at a specific operating point. When the verification is accurate, the cooling capacity and COP at that operating point are used as the standard cooling capacity and standard COP for the compressor at that point. This allows for testing of non-azeotropic refrigerant compressors with different refrigerant types and component ratios to obtain standard cooling capacity and standard COP. Subsequent mass production of the compressor uses these standard cooling capacity and standard COP as the benchmark for performance quality inspection, standardizing the performance inspection process and ensuring the stability of the non-azeotropic refrigerant compressor product performance. It also facilitates accurate selection of non-azeotropic refrigerant compressors by manufacturers of refrigeration equipment such as refrigerators.