Expansion Types of Refrigerators

Deuterium, The test results using liquid deuterium as the track medium are of particular interest from two standpoints. The first point of interest is that these are the first operational data obtained at these temperatures. The second point is that using liquid expansion, with this type of refrigeration system, permits operation of existing chambers over a wider range of temperatures than has been possible using vapor expansion. 

The dry expansion circuit does not have a liquid level which can be detected, and another type of signal must be used to control the valve. Dryexpansion circuits must be designed and installed so that there is no risk of liquid refrigerant returning to the compressor. To ensure this state, extra heat exchange surface is added to that needed, in order to heat the dry saturated gas into the superheat region. The amount of superheat is usually of the order of 5 K. 

Several types of mechanical refrigerators have been used in the last decades. Most of them use gas compression-expansion cycle to produce refrigeration work done on the fluid by compression is rejected to the surrounding, then the expansion of fluid to a lower pressure in a separate chamber achieves cooling. 

The optimized parameters are pressures of the working agent before and after the expansion valve. The absorber refrigeration machine achieves a COP of 1.41. Optimization should be carried out separately for each type of heat source (e.g. fuel cell type) connected to the chiller, due to the different composition and temperature of the flue gas delivering the heat to the chiller in each case. 

Evaporators of this general type with dry expansion circuits will have the refrigerant within the tubes, in order to maintain a suitable continuous velocity for oil transport, and the liquid in the shell. These can be made as shell-and-tube, with the refrigerant constrained to a number of passes, or maybe shell-and-coil (see Figure 7.4). In both these configurations, baffles are needed on the water side to improve the turbulence, and the tubes maybe finned on the outside. Internal swirl strips or wires will help to keep liquid refrigerant in contact with the tube wall. 

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