The chiller shell-and-tube evaporator is made of two-layer metal plates by high-pressure gas expansion molding or mechanical pressing, and can also be made of aluminum alloy die-casting. This kind of swallow hair device is widely used in small refrigeration equipment such as refrigerators, commodity display cabinets, and popsicle storage boxes. Flat-shell and tube-type swift-freezers made of aluminum alloy die-casting are widely used for contact freezing, and are generally called flat-shell and tube-type quick-freezers.
The heat transfer coefficient of the chiller shell and tube evaporator is larger in liquid than in gas, and larger in flowing state than in static state.
Because of its good heat transfer effect, compact structure, small footprint and easy installation, the chiller shell and tube evaporator is widely used. The structure of the shell and tube evaporator of the chiller is the same as that of the horizontal shell and tube condenser. In order to control the appropriate flow rate, the refrigerant enters from the lower part of the end cover, flows out from the upper part, and flows back and forth in the Yanfa tube and the end cover to become Multi-program flow. The refrigerant flows outside the tube, the throttling refrigerant liquid enters from the bottom or side of the evaporator, and the gas after swallowing is discharged from the upper part.
The upper part of the evaporator is generally equipped with a few rows of cooling pipes or a gas bag is welded on the shell, so that the gas can separate the droplets before leaving the evaporator. A special separation device is generally made for a large swallow hair device.
When the shell-and-tube type swallow-generator is working, a certain amount of liquid refrigerant should be kept in the shell, and the liquid level should be controlled by a floating ball valve. The height of the hydrostatic surface should be about the diameter of the cylinder. Heat exchange is performed on a liquid-to-liquid basis. Therefore, the heat transfer effect is better and the heat transfer coefficient is larger. But the liquid level should not be too high, otherwise there will be liquid backflow of the refrigerator.
Although nitrogen and slave are common to this type of evaporator, the materials of the tubes used are different. Generally, the ammonia vaporizer is made of 4025x2.5-438x3 steel pipe, and the air conditioner is made of copper pipe or brass pipe. When the coolant is corrosive, the tube sheet generally uses a corrosion-resistant composite metal plate, and the cooling pipe uses a high-strength aluminum-arsenic-brass tube. In order to enhance the heat transfer effect, finned tubes are often used in Nourion evaporators.
In general, the heat transfer coefficient of the evaporator is smaller than that of the condenser, which is mainly due to the small heat transfer temperature difference.