refrigeration

refrigeration - Refrigeration Cycles A Carnot cycle in...

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Refrigeration Cycles • A Carnot cycle in reverse evaporator compressor condenser turbine 4 1 2 3 41 2 3 Q L Q H T s Evaporates liquid into 100% vapor 1 • Compress vapor instead of two phase mixture 2 • Replace turbine by an expansion valve (not an isentropic process) 4
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Throttling Process • A significant reduction in pressure can be achieved by introducing a restriction into the flow line. The restriction can be a partially-opened valve, or a porous plug, or a capillary tube. • Enthalpy (internal energy + flow work) is a constant going through a throttling process: h 1 =h 2 . Example: Saturated liquid refrigerant-134a enters the throttling device at 1 MPa and is exiting at a lower pressure of 0.1 MPa. Determine the temperature drop during this process. At inlet: from table A-9, T 1 =T [email protected] =39.39°C, h 1 =h [email protected] =105.29 kJ/kg At outlet: h 1 =h 2 , P 2 =0.1 MPa, T 2 =-26.43°C h f =16.29, h fg =215.06, x=(h 2 -h f )/h fg =0.414 (41.4% of the refrigerant-134a vaporizes during the throttling process). Question: where does the energy come from to vaporize the refrigerant?
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This note was uploaded on 11/27/2011 for the course EML 3002c taught by Professor Staff during the Fall '08 term at FSU.

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refrigeration - Refrigeration Cycles A Carnot cycle in...

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