The straight pipe evaporator is used for ammonia refrigeration device, its structure is shown in the figure below, the straight pipe evaporator is all welded by seamless steel pipes, the evaporator pipes are in groups, and the evaporators can be combined by several pipe groups according to different capacity requirements. The evaporation tube set is installed in a rectangular metal tank. Each group of evaporation pipes consists of two horizontal pipes and risers welded to them with slightly bent ends. At one end of the pipe group, the upper header is connected to the gas-liquid separator, and the lower header is connected to the oil collector. Ammonia enters through the middle supply pipe. The liquid supply pipe extends from the top all the way to the lower header, so that the liquid enters the lower header from the bottom and enters the riser evenly. The refrigerant liquid absorbs the heat of the refrigerant in the tube and continuously evaporates. After the vaporized refrigerant passes through the upper header and is separated by the gas-liquid separator, the steam is drawn out from the top and sucked in by the compressor, and the liquid returns to the lower header. There is a tube at the upper end of the oil collector that is connected to the suction pipe in order to remove the refrigerant from the refrigeration oil, and the accumulated lubricating oil is released from the drain pipe at regular intervals.
In order to improve the heat transfer effect of the straight tube evaporator, a mixer is installed in the water tank. There are two types of mixers: horizontal and vertical. Because horizontal mixers need sealing measures when they are installed and are difficult to maintain, there are many vertical mixers at present. The water flow rate is generally maintained at 03~0.7m/s。The upper part of the tank is provided with an overflow pipe, and the bottom is provided with a drain.
In order to control the ammonia level in the evaporator manifold, a float valve or an electronic level control device is installed on the tank.
The riser evaporator is easy for the operator to observe and maintain due to the opening of the upper part. The refrigerant capacity is large, so when using fresh water as the refrigerant, there is no risk of freezing and damaging the equipment. When using brine as a refrigerant, due to the contact between brine and air, the corrosion of the water tank is more serious, it is necessary to add corrosion inhibitor to the brine, and the brine is easy to absorb water in the air and reduce the concentration, so it is necessary to check the relative density of the brine frequently, and add solid salt to the brine.