Philips refrigerator

The Philips refrigerator is based on the Stirling cycle. The basic components of the refrigerator are a displacer, a regenerator, and a piston all enclosed in a cylinder. The refrigeration cycle involves four process steps (see Fig. 4.25) ... 

Fig. 4.25. Process steps associated with the Philips refrigerator.

A Philips refrigerator is used to maintain a temperature of 77.8 K while rejecting heat to an ambient sink of 300 K. The working fluid used in the system is helium gas. The pressure limits for the system are 0.101 MPa minimum and 1.01 MPa maximum. Determine the refrigeration effect, the coefficient of performance, and the figure of merit for the system, assuming that all processes in the system are ideal and the helium may be considered to behave as an ideal gas. 

We will then describe the Collins helium liquefier and coolers which use turboexpanders (Linde He liquefier). At the end of the chapter, we will describe cooling cycles which use regenerators and other cycles used in cryocoolers (Philips-Stirling, Gifford-McMahon (GM), Klimenko cycles and pulse tube refrigerators (PTRs)). 

Photochemical reactors are commercially available or can be custom-built. They consist of an oval mirror-type wall of ca. 30 cm maximum radius equipped with two Hanovia 450-W or Philips HPT 400-W high-pressure mercury lamps inserted into a water refrigerated Pyrex flask, or equipped with a 300-W Osram sunlamp vessel (Pyrex flask). 

In synthetic laboratories, the most common method to obtain crystals is crystallization from solution. In a way this is also the most difficult process to control. The solvent evaporation rate can be affected by several factors such as ambient humidity, temperature and ventilation, thermal excursion during the 24 h in the case of open air room temperature crystallizations, and vibrations of the building (footsteps, traffic, lifts, etc.) and of the refrigerators. There is no unique and transferable recipe for the crystallization of a substance Philip Ball concluded his Nature Editorial in 1996 by saying, the precipitation of good single crystals remains a black magic [68]. 

Question by J. Meisler, North American Philips Company What is the source of refrigeration Is the compressed gas ever contaminated What is the minimum continuous time of operation ... 

In the past, temperatures below -100 C have been produced primarily via the liquefaction of gases with a low boiling point. Recently the available arsenal of liquefaction apparatus has been augmented by the introduction by the Philips Company of the gas refrigerating machine employing the Stirling cycle, in its first version of an air liquefier [1]. 

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