Stirling Cycle Refrigerator

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1.1 Background

Thermodynamic cycle can be divided into two that are power cycle and refrigeration cycle. The cycle that produce net amount of works is called power cycle. The power cycle that can remain it working fluid in gaseous phase is called gas power cycle. There are many types of cycle in gas power cycle such as Otto cycle, Diesel cycle, Bryton cycle, Stirling cycle and Ericson cycle. The Otto cycle is known as ideal cycle for spark-ignition cycle while the Diesel cycle is known as compression-ignition internal combustion engine. The Bryton cycle is known as ideal cycle for the modern-gas turbine engineand can be categorize as one of the gas power cycle. The Bryton cycle itself has four internal reversible processes. The next cycle is Stirling cycle. This Stirling cycle involves an isothermal heat-addition process and isothermal heat-rejection process. .

In reversed of heat engine, it has refrigeration system. Refrigeration system is the transfer system for heat from low temperature region to higher temperature region. The device that produces refrigeration is called refrigerator, heat pump and air-conditioning. The cycle they operate is called refrigeration cycle. The refrigerator and heat pump operate on the same cycle but different with their objective. The objective of refrigerator is to maintain the refrigerated space at low temperature. Discharging this heat to a higher-temperature medium is merely a necessary part of the operation. But the objective of heat pump is to maintain heated space at high temperature by absorbing the heat from a low temperature source and then supplying that heat to high temperature medium such as house. The refrigeration cycle can be divided into two that is vapor compression refrigeration cycle and gas refrigeration cycle. In vapor compression refrigeration cycle, the refrigerant is vaporized and condensed alternately. This cycle is the modified of the Rankine cycle operating in reverse. It also can be the Reversed Carnot Cycle operates on the reversed direction. For the gas refrigeration cycle, the refrigerants remain in the gaseous phase throughout the entire cycle. The Reversed Stirling Cycle and the Reversed Bryton Cycle can be categorized in this gas refrigeration system. The Reversed Stirling Cycle is the cycle of Stirling refrigerator operated.

1.2Stirling Cycle Refrigerator

Stirling Cycle Refrigerator is one of the machine that operating on the Stirling cycle machine. In Stirling cycle, it has two popular cycles that are Stirling cycle engine and Stirling cycle refrigerator. The operation of the Stirling cycle involves an isothermal heat-addition process and isothermal heat -rejection process. It different from the carnot process. The two isentropic processes are replaced by two constant -volume regeneration process. In the Stirling cycle machine, it has five components that are working gas, heat-exchangers, displacer mechanism, regenerator, and expansion/compression mechanism. The working gas is trapped within the system. Stirling cycle has heat-exchangers that are heat absorbing heat-exchanger and heat rejecting heat-exchanger. Heat absorbing heat-exchange is used to transfer heat from outside system to the working gas, while heat rejecting heat-exchanger is used to transfer the heat from the working gas to the outside system. Displacer mechanism is used to move the working gas between the hot and cold end of the machine. The function of regenerator is as a thermal barrier between the hot and cold ends of the machine. Regenerator also can be a ‘thermal store’ for the cycle. The function of expansion/compression mechanism is to expands or/and compress the working fluid and it also can produce net work output that is used to move the heat from low to high temperature region.

Many advantages of Stirling cycle engine and Stirling cycle refrigerator. Stirling cycle engine has a constant high efficiency, low noise compare with other...
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