A vapor compression cycle is used in most household refrigerators, refrigerator–freezers and freezers. In this cycle, a circulating refrigerant such as R134a enters a compressor as low-pressure vapor at or slightly below the temperature of the refrigerator interior. The vapor is compressed and exits the compressor as high-pressure superheated vapor. The superheated vapor travels under pressure through coils or tubes that make up the condenser; the coils or tubes are passively cooled by exposure to air in the room. The condenser cools the vapor, which liquefies. As the refrigerant leaves the condenser, it is still under pressure but is now only slightly above room temperature. This liquid refrigerant is forced through a metering or throttling device, also known as an expansion valve (essentially a pin-hole sized constriction in the tubing) to an area of much lower pressure. The sudden decrease in pressure results in explosive-like flash evaporation of a portion (typically about half) of the liquid. The latent heat absorbed by this flash evaporation is drawn mostly from adjacent still-liquid refrigerant, a phenomenon known as auto-refrigeration. This cold and partially vaporized refrigerant continues through the coils or tubes of the evaporator unit. A fan blows air from the refrigerator or freezer compartment ("box air") across these coils or tubes and the refrigerant completely vaporizes, drawing further latent heat from the box air. This cooled air is returned to the refrigerator or freezer compartment, and so keeps the box air cold. Note that the cool air in the refrigerator or freezer is still warmer than the refrigerant in the evaporator. Refrigerant leaves the evaporator, now fully vaporized and slightly heated, and returns to the compressor inlet to continue the cycle. Domestic refrigerators are extremely reliable because the moving parts and fluids are sealed from the atmosphere for life, with no possibility of leakage or contamination. In comparison, mechanically-driven refrigeration compressors, such as those in automobile air conditioning, inevitably leak fluid and lubricant past the shaft seals. This leads to a requirement for periodic recharging and, if ignored, possible compressor failure.
An absorption refrigerator works differently from a compressor refrigerator, using a source of heat, such as combustion of liquefied petroleum gas, solar thermal energy or an electric heating element. These heat sources are much quieter than the compressor motor in a typical refrigerator. A fan or pump might be the only mechanical moving parts; reliance on convection is considered impractical.
The Peltier effect uses electricity to pump heat directly; refrigerators employing this system are sometimes used for camping, or in situations where noise is not acceptable. They can be totally silent (if a fan for air circulation is not fitted) but are less energy-efficient than other methods.
Other uses of an absorption refrigerator (or "chiller") include large systems used in office buildings or complexes such as hospitals and universities. These large systems are used to chill a brine solution that is circulated through the building.
Many modern refrigerator/freezers have the freezer on top and the refrigerator on the bottom. Most refrigerator-freezers—except for manual defrost models or cheaper units—use what appears to be two thermostats. Only the refrigerator compartment is properly temperature controlled. When the refrigerator gets too warm, the thermostat starts the cooling process and a fan circulates the air around the freezer. During this time, the refrigerator also gets colder. The freezer control knob only controls the amount of air that flows into the refrigerator via a damper system.[11] Changing the refrigerator temperature will inadvertently change the freezer temperature in the opposite direction. Changing the freezer temperature will have no effect on the refrigerator temperature. The freezer control may also be adjusted to compensate for any refrigerator adjustment.
This means the refrigerator may become too warm. However, because only enough air is diverted to the refrigerator compartment, the freezer usually re-acquires the set temperature quickly, unless the door is opened. When a door is opened, either in the refrigerator or the freezer, the fan in some units stops immediately to prevent excessive frost build up on the freezer's evaporator coil, because this coil is cooling two areas. When the freezer reaches temperature, the unit cycles off, no matter what the refrigerator temperature is. Modern computerized refrigerators do not use the damper system. The computer manages fan speed for both compartments, although air is still blown from the freezer.
A few manufacturers, such as Sub Zero,[12] Sun Frost,[13] and Miele[14] offer dual compressor models. These models have separate freezer and refrigerator compartments that operate independently of each other, sometimes mounted within a single cabinet. Each has its own separate compressor, condenser and evaporator coils, insulation, thermostat, and door. Typically, the compressors and condenser coils are mounted at the top of the cabinet, with a single fan to cool them both.
This design, where no air passes between the two compartments, provides for more appropriate humidity levels and much tighter temperature control in each compartment. It also requires much less energy to operate, since each compressor & coolant system can be optimized for a specific temperature range. Further, opening the door of one compartment does not affect the temperature of the air or humidity level in the other compartment. Thus, it avoids many of the disadvantages of the much more common single compressor designs described above, although at a higher initial cost and increased system noise.[citation needed] Manufacturers of such designs argue that the increased cost is compensated over time due to reduced energy use and less food waste due to reduced spoilage.
วงจรอัดไอน้ำใช้ในตู้เย็นในครัวเรือน ตู้เย็นตู้แช่แข็ง และตู้แช่แข็งมากที่สุด ในรอบนี้ แบบหมุนเวียนเช่น R134a ป้อนอัดที่เป็นไอ low-pressure ที่ หรือต่ำ กว่าอุณหภูมิภายในตู้เย็นเล็กน้อย ไอน้ำจะถูกบีบอัด และออกจากคอมเพรสเซอร์เป็นไอน้ำ superheated ปั้ม ไอน้ำ superheated เดินทางภายใต้ความดันผ่านขดลวดหรือท่อที่ประกอบเครื่องควบแน่น passively ความร้อนด้วยขดลวดหรือท่อ โดยสัมผัสกับอากาศในห้อง เครื่องควบแน่นที่น่าไอ ที่ liquefies ขณะที่ระบบทำการออกจากเครื่องควบแน่นที่ มันยังอยู่ภายใต้ความกดดัน แต่เป็นเพียงเล็กน้อยเหนืออุณหภูมิห้อง แบบนี้ของเหลวถูกบังคับเป็นการวัดแสงหรือการควบคุมปริมาณอุปกรณ์ หรือที่เรียกว่าการขยายวาล์ว (หลักการรู pin ขนาดเชื่อมในที่ท่อ) ไปยังพื้นที่ของความดันต่ำมาก ลดความดันลงฉับพลันที่เกิดการระเบิดเหมือนแฟลชระเหยของบางส่วน (โดยปกติประมาณครึ่งหนึ่ง) ของของเหลว ดูดซึม โดยระเหยนี้แฟลช latent ความร้อนออกจากแบบของเหลวยังคงติด ปรากฏการณ์ที่เรียกว่าเครื่องทำความเย็นอัตโนมัติส่วนใหญ่ แบบนี้เย็น และแก้ไขบางส่วนยังคงผ่านขดลวดหรือหลอดของหน่วย evaporator พัดลมพัดอากาศจากตู้เย็น หรือช่องแช่แข็ง ("กล่องอากาศ") เหล่านี้ขดลวด หรือหลอด และการออกแบบทั้งหมด vaporizes วาดเพิ่มเติม latent ความร้อนจากอากาศกล่อง อากาศเย็น ๆ นี้กลับไปช่องตู้เย็นหรือตู้แช่แข็ง และเพื่อ เก็บกล่องอากาศเย็น หมายเหตุว่า อากาศเย็นในตู้เย็นหรือตู้แช่แข็งยังคงอุ่นกว่าแบบใน evaporator ที่ แบบที่ evaporator ตอนนี้ ทั้งหมดระเหย และอุ่นเล็กน้อย และกลับกับทางเข้าของปั๊มต้องการ ตู้เย็นในประเทศน่าเชื่อถือมากเนื่องจากชิ้นส่วนเคลื่อนไหวและของเหลวปิดผนึกจากบรรยากาศการใช้ชีวิต ความเป็นไปได้ไม่รั่วไหลหรือปนเปื้อน ในการเปรียบเทียบ ขับเคลื่อนกลไกการแช่แข็ง compressors เช่นเครื่องปรับอากาศรถยนต์ ย่อมรั่วไหลน้ำมันและน้ำมันหล่อลื่นผ่านสัญลักษณ์เพลา นี้นำไปสู่ความต้องการไปเป็นครั้งคราว และ ละเว้น คอมเพรสเซอร์สามารถล้มเหลวAn absorption refrigerator works differently from a compressor refrigerator, using a source of heat, such as combustion of liquefied petroleum gas, solar thermal energy or an electric heating element. These heat sources are much quieter than the compressor motor in a typical refrigerator. A fan or pump might be the only mechanical moving parts; reliance on convection is considered impractical.The Peltier effect uses electricity to pump heat directly; refrigerators employing this system are sometimes used for camping, or in situations where noise is not acceptable. They can be totally silent (if a fan for air circulation is not fitted) but are less energy-efficient than other methods.Other uses of an absorption refrigerator (or "chiller") include large systems used in office buildings or complexes such as hospitals and universities. These large systems are used to chill a brine solution that is circulated through the building.Many modern refrigerator/freezers have the freezer on top and the refrigerator on the bottom. Most refrigerator-freezers—except for manual defrost models or cheaper units—use what appears to be two thermostats. Only the refrigerator compartment is properly temperature controlled. When the refrigerator gets too warm, the thermostat starts the cooling process and a fan circulates the air around the freezer. During this time, the refrigerator also gets colder. The freezer control knob only controls the amount of air that flows into the refrigerator via a damper system.[11] Changing the refrigerator temperature will inadvertently change the freezer temperature in the opposite direction. Changing the freezer temperature will have no effect on the refrigerator temperature. The freezer control may also be adjusted to compensate for any refrigerator adjustment.
This means the refrigerator may become too warm. However, because only enough air is diverted to the refrigerator compartment, the freezer usually re-acquires the set temperature quickly, unless the door is opened. When a door is opened, either in the refrigerator or the freezer, the fan in some units stops immediately to prevent excessive frost build up on the freezer's evaporator coil, because this coil is cooling two areas. When the freezer reaches temperature, the unit cycles off, no matter what the refrigerator temperature is. Modern computerized refrigerators do not use the damper system. The computer manages fan speed for both compartments, although air is still blown from the freezer.
A few manufacturers, such as Sub Zero,[12] Sun Frost,[13] and Miele[14] offer dual compressor models. These models have separate freezer and refrigerator compartments that operate independently of each other, sometimes mounted within a single cabinet. Each has its own separate compressor, condenser and evaporator coils, insulation, thermostat, and door. Typically, the compressors and condenser coils are mounted at the top of the cabinet, with a single fan to cool them both.
This design, where no air passes between the two compartments, provides for more appropriate humidity levels and much tighter temperature control in each compartment. It also requires much less energy to operate, since each compressor & coolant system can be optimized for a specific temperature range. Further, opening the door of one compartment does not affect the temperature of the air or humidity level in the other compartment. Thus, it avoids many of the disadvantages of the much more common single compressor designs described above, although at a higher initial cost and increased system noise.[citation needed] Manufacturers of such designs argue that the increased cost is compensated over time due to reduced energy use and less food waste due to reduced spoilage.
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