TABLE OF CONTENTS Coolers in which the refrigerant is not depleted are generally denoted as refrigerators. This naming convention sets them apart from liquefiers, coolers that require a constant refrigerant supply. Refrigerators for cryogenic temperatures are denoted as cryocoolers.
Cryocoolers divide broadly into two categories, based on the gas heat exchanger type and the nature of fluid flow. [8.1]
In a recuperative cooler, two steady fluid streams exchange heat across a mutual boundary.
In a regenerative cooler, one fluid stream moves back and forth within the same porous heat exchanger, alternately losing and absorbing heat.
In a regenerative-cycle machine, the working fluid does not circulate in a steady loop with steady-state temperatures nor exhaust to the environment. Rather, each element of the gas oscillates in its own local temperature and pressure neighborhood as it oscillates locally within the machine. This chapter examines two types of regenerative coolers used in space applications, Stirling and pulse tube cryocoolers.
Three functional requirements differentiate space coolers from those used in all other applications:
no change in performance for lifetimes up to 10 years
negligible vibration
autonomous, reliable remote control
The first requirement derives from the cooler's use in high-cost, nonmaintainable operations in space. The second derives from the cooler's primary use in cooling electro-optical sensors that are subject to blurring under vibration. Considerable extra hardware and electronics costs go into the latter requirement, and some applications not requiring complete vibration suppression might be able...
