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Emerson
 
The concept of Vapor Injection Technology can be explained with the aid of the chart #1.
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 The basic components of the a/c system are shown in this chart – compressor, condenser, expansion valve and evaporator. The vapor injection circuit is shown through the red line. A part of the warm liquid coming out of the condenser is diverted to another heat exchange circuit. When the solenoid valve (as shown in Chart #1) is opened, a part of the liquid is extracted and it passes through an expansion device. This throttling process reduces the pressure and temperature of the refrigerant. This cold liquid is then passed through a heat exchanger – either a plate heat exchanger or a flash tank – and it exchanges heat with the main warm refrigerant flow that is going to the evaporator from the condenser. This exchange of heat cools the main liquid refrigerant and consequently increases the liquid sub cooling significantly. During this heat exchange process, the scavenged cold liquid turns into vapor. This vapor is injected in the scroll set to cool the scrolls. The main liquid refrigerant (now significantly sub cooled) then passes through the second throttling process and enter the evaporator as the chilled liquid refrigerant.
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As can be understood, 2 major benefits are obtained with the above cycle. First, the cold vapor injected in the scroll sets allows the scroll sets to get cooled down and enhances the reliability of the compression mechanism. During low ambient operation, the pressure ratios are quite high and discharge line temperature is a challenge. Cooling the scroll sets through this vapor injection allows for extended ambient operation. Secondly, the significant sub cooling gain helps to increase the cooling/heating capacity significantly. As can be seen from the cycle diagram, the mass flow through the evaporator is M while the mass flow through this condenser is M + I. The added mass flow through the condenser contributes to the heat capacity gain. |
Digital Scroll with vapor injection technology
The Digital Scroll technology has already been explained elsewhere, but the top portion of the compressor is shown in Chart #2 to explain the vapor injection path. As can be seen in the chart, the vapor is injected in the intermediate cavity of the scrolls. Since the intermediate cavity is at a higher pressure, the injection pressure has to be higher – the optimization of the injection pressure is important to ensure adequate heating capacity gain.
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The physical hardware that is used inside the compressor to inject the vapor is shown in Chart #3. A flexible pipe is connected from the compressor shell to the fixed top scroll. There is a fitting on the compressor shell and another fitting on the fixed scroll. The flexible pipe is looped inside the compressor so that there is enough flexibility in the tube to accommodate the 1.0mm vertical movement of the scroll sets during loading and unloading.
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