Liquid cooling evaporators
Liquid cooling evaporators can be direct expansion or flooded type. Flooded evaporators (Fig. 7.2) solid, liquid, boiling at random, steam, leaving at the top. In the case of ammonia, any oil falls to the bottom and will be deducted from the drain tank or oil drain connection.
In shell-and-tube type of fluid, as a rule, in tubes and the shell is about three-quarters full of liquid, boiling refrigerant. Number of pipes, drop into the upper part of the body to provide space for suction of the gas to escape clean surfaces without the involvement of the liquid. Additional features such as multiple points headers, suction traps dome and the walls will help to avoid drops of the liquid inside the main suction pipe. Speed of gas shall not exceed 3 m/s and lower figures are used by some designers.
Location-cross a flooded shell and tube type shown in Fig. 7.3. The speed of the fluid in the tubes should be about 1 m/s or more, to foster inner turbulence for good heat transfer.
End cover section will restrain the flow of number of passes, as with shell-and-tube condenser.
Liquid cooling evaporators may consist of a coil in the open vessel, and can be overloaded or direct expansion scheme. Flooded coils are connected to a combined battery fluid and suction separator (typically referred to as separators), as a horizontal or vertical drum (see Fig. 7.2(c) and 7.4). Expansion valve supports the fluid level in the drum and natural circulation configure bubbles to escape from the liquid refrigerant to heat transfer surface.
Shell-and-tube evaporators with direct extension of the refrigerant circuits inside the pipe for maintenance of necessary speed for continuous transport of oil, and fluid in the sink. They can be made as shell and tube, refrigerant limited number of passes (Fig. 7.5), or may be shell-and-coil (see Fig. 7.6). In both of these configurations sections are on the water side to improve turbulence, and finned tubes can be on the street. The internal torsion of the wires or maintain liquid refrigerant into contact with the tube wall.
Spray a chiller works with far fewer refrigerant than usually flooded evaporator does. On Fig. 7.7 the liquid refrigerant level in alignment shell holds below pipes and pumped liquid spray nozzles, to make sure that the surface of the pipe is covered with boiling liquid film. Water or in brine passes through the tubes. The release of gas at the compressor suction is located in the upper part of the body and the linear arrangement prevent drops of liquid. Due to the distribution of refrigerant very close control of evaporation can be obtained. Evaporation stops immediately when a liquid spray stopped. For these reasons, the coolant can be cooled down to a temperature close to its freezing. Water can be cooled up to the temperature of less than 1C boiling point close to 2C.
Direct expansion coil dive in the open vessel will be in a continuous chain, or the number of parallel chains (see Fig. 7.8). The speed of the liquid at such coils can be increased by the vents and there may be special purpose agitators, as in ice making tank. Coil in the open vessel may be permitted to collect a layer of ice during off-load, providing heat accumulation and supply of spare cooling capacity during peak periods.