Two types of heat exchangers used in mechanical refrigeration systems fluid supply of heat interchanger and refrigerant-water heater. Each is discussed here. Fluid intake for the heat interchanger is a heat exchanger that transfers a part of the heat from the liquid coolant leaving the condenser to the suction gas from the evaporator. There are three reasons for this.
The first reason is to increase the efficiency of the refrigeration cycle, particularly at low temperatures. The second reason is subcool liquid refrigerant coming from the condenser in order to prevent the outbreak of gas at the inlet of the TXV or other dispenser. "Reprogramming" of the liquid leaving the condenser is a problem for systems with small capacitor hypothermia. This is also a problem for the systems of high-liquid-line pressure differences caused by long pipelines is done or long liquid risers.
The third reason to evaporate the small volumes of the liquid refrigerant is expected to return from the evaporator in certain applications.
This ensures that the suction inlet gas dry. Thus, it prevents damage, noise, and inefficiency caused by the ingress of liquid refrigerant. System with high load fluctuations sometimes there is a need, because fluid, periodically "slops over" into the suction line. This occurs when the load drops faster than the system can respond. In addition, heat pumps that use the reversal of the cooling process, it may include both suction line accumulator and liquid suction interchanger. They keep the liquid floodbacks and evaporate slowly between them cycle turns.
In the liquid suction interchanger, cool suction steam is passed through a heat exchanger in counterflow on the hot fluid condenser. That is, two liquid flows in opposite directions, as shown. In the heat exchanger, the heat produced by suction gas as much that has lost liquid refrigerant. However, temperature changes are not equal. Specific heat capacity (Btu/lb for the degrees F) of the refrigerant vapor less than the liquid. Thus, the increase in the temperature of the steam is always greater than the drop in the temperature of the liquid. Consider, for example, reach-in refrigerated display cases that uses R-502 and maintained at the level of 28F. 24F increase suction temperature of the steam will correspond to reduce the temperature of the liquid around 12F.
The maximum amount of heat that can be transferred in a manner defined by the difference in temperature between the gas and liquid entering the interchanger; the relative size of the surface exposure of two liquids have to each other; and how much time the two liquids should exchange of heat. Zoom in on any of these three factors, increases teplootdachu.
The location of the heat exchanger depends on the intended use and allocation of equipment. If its purpose is to provide liquid subcooling, it is installed as close to the condenser as permissible practice. If it is used for cleaning the surplus of the liquid in the suction line close to the evaporator. So both liquid and suction lines must be run in the heat exchanger, equipment layout has a greater effect on its place, than any other factor.
Types of liquids and suction interchangers used to affect the two liquids should exchange of heat. This also affects the surface of the exposition of two liquids have for each other is the unit of length. This is the simplest form interchanger. Clean, straight length of the suction and liquid line attached or soldered together so that a counter-flow is maintained. Then two lines with isolation as a unit. The longer the run, the more heat exchange. Fluid is always runs along the bottom of the suction line. So when the heat exchanger is designed to remove excess liquid in the suction line liquid line should always be at the bottom of a horizontal section of the suction line.
Tube-in-tube heat exchanger has more surface impact per unit length than two lines soldered. Again, a counter is saved. Liquid runs in the space outside the suction line. The length of the junction determines the contact time for the two liquids. These heat exchangers can be easily field-built by purchasing interchanger tees for each end and tees, connecting with standard refrigerant one size larger than the suction line.
The Shell-and-finned coil heat pipe heat exchanger provides maximum surface exposition of two liquid per unit length. Countercurrent is again observed.
In summary, on the liquid line interchangers: When used for air-conditioning, are useful in providing hypothermia and remove any excess liquid refrigerant in the suction line. When using for refrigeration applications are useful for hypothermia and purification of liquid refrigerant in the suction line. They also improve the refrigerant cycle efficiency. Specifically, where R-22 is used pipe-in-pipe " diversity is used, and then only for cleaning up excess liquid. R-502 systems, on the other hand, usually use interchangers to improve efficiency, as well as for the other two goals. The disadvantage interchangers is that they tend to increase the suction temperature, which increases power consumption of the compressor.
Another disadvantage is that the upper suction temperature limits for safe operation of the compressor should be met, or a compressor may damage them. Liquid-intake interchanger pipelines increases the complexity which adds designing, mounting and material costs on the field-grey jobs. Finally, because the shell-and-finned coil interchanger is a natural oil trap, it should be properly drained to avoid problems with the return of oil...