6.I4 object or volume to be cooled. This absorption takes place by vaporization of the liquid-vapor mixture into the saturated vapor state, without any change in pressure or temperature. The volume occupied by the refrigerant therefore expands. This leads back to state 1: saturated vapor at p 1 and T 1 _ Figure 6.I2 is a schematic of the actual Rankine heat pump system proposed for the colony. The refrigerant in state 1 (saturated vapor at pevap and T 1 ) is compressed to superheated vapor at prad and T 2 (state 2). It then cools and condenses in the external radiator to state 3: saturated liquid at prad and T 3 . It further cools by isenthalpic expansion in the throttling valve, lowering its pressure to pevap and its temperature to T 4 = T 1 . This is state 4, a liquid-vapor mixture. The refrigerant then absorbs heat from the hull in the evaporator, returning to state 1, a saturated vapor at pevap and T 1 . The compressor cannot convert all of its power input from Pthermal into compressive work on the refrigerant. The difference between Pthermal and the rate of work done on the refrigerant is called Pcomploss' and adds to the heat released into the hull. The other processes in the Rankine heat pump are considered ideal. In particular, prad is assumed constant throughout the external radiator. VI.I.3: ANALYSIS The relations governing the processes in the Rankine heat pump system are (6.Il): Pthermal Poutputrad m (h2-h3) h3 h4 0 Pheat into pump m (hl-h4) (The first equation includes the compressor inefficiency.)
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