Page 46 - Low Temperature Energy Systems with Applications of Renewable Energy
P. 46

34                  Low-Temperature Energy Systems with Applications of Renewable Energy





























         Fig. 1.18 Trends in working fluids for refrigeration units: a closed cycle.
         Redrawn from [28].


         1.6.3  Summary: Basic requirements for working fluids
         •  Thermodynamic
            • Large heat of vaporization and the largest values of the Clausius number Cl which rep-
              resents the ratio of energy transport associated with the fluid momentum to energy trans-
              fer by thermal conduction:

                  3
                         2
                 V Lr  rV   V
             Cl ¼    ¼
                 l DT  l DT=T

















         Fig. 1.19 Triune concept of sustained development [30].
   41   42   43   44   45   46   47   48   49   50   51