Fig. 2: Refrigerant flash intercooling only slightly increases the coefficient of performance (COP) for ammonia.
From: A unified approach for the thermodynamic comparison of heat pump cycles

a The calculated COP improvement \(\alpha\) varies when the intermediate temperature \({T}_{i}\) in the flash tank increases for different condensing temperatures. b The maximum COP improvement (Max α). c The corresponding optimal flash tank temperature (optimal \({T}_{i}\)).