Chiller and its oil return control method

Abstract

The invention discloses a water chilling unit and an oil return control method thereof. The water chilling unit comprises a compressor, a condenser, an evaporator, an oil pump, an oil tank and an ejection device. A first refrigerant inlet of the ejection device is connected with a second refrigerant outlet of the condenser through a first throttling element. A second refrigerant inlet of the ejection device is connected with an outlet of the oil pump through a second throttling element. An oil inlet of the ejection device is connected with a second refrigerant outlet of the evaporator. An outlet of the ejection device is connected with an inlet of the oil tank or a gas return port / oil inlet of the compressor. The method includes the steps that the high pressure of the water chilling unit and the pressure at the position of the outlet of the oil pump are obtained; and the first throttling element and the second throttling element are controlled according to the high pressure and the pressure at the outlet position of the oil pump. By means of the method, it can be ensured that lubrication oil depositing at the bottom of the evaporator is ejected through high-pressure gas, and therefore reliability and high efficiency of oil return are effectively improved, the compressor is prevented from damage, and reliability of the water chilling unit is improved.

Description

technical field [0001] The invention relates to the technical field of oil return control, in particular to an oil return control method of a chiller and a chiller. Background technique [0002] For screw and centrifugal compressor units, due to the high speed and large displacement of the compressor, the resulting oil discharge is also large, so it is generally necessary to set up a special oil return circuit. [0003] In the related art, in addition to using an oil separator, an ejector is also used to eject the lubricating oil deposited at the bottom of the evaporator by using the high-pressure gas at the top of the condenser, and return it to the oil pool of the compressor. However, since the working conditions of the system change with the seasons, in transitional seasons, it is easy to have a small pressure difference operation with a small high and low pressure difference. In the small pressure difference operation condition, the high-pressure gas at the top of the co...

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Problems solved by technology

However, since the working conditions of the system change with the seasons, in the transitional season, it is easy to have a small pressure difference operation with a small high and low pressure difference. Under the small pressure difference operation condition, the high-pressure gas at the top of the condenser is used as the ejection source The ejection effect will be greatly reduced. In severe cases, it may cause the compressor to run out of oil and damage the compressor.

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