Refrigeration# Refrigerators and heat pumps, and their Carnot limits. Perkins’s vapour-compression refrigerator (1834) Perkins's vapour-compression refrigerator (1834) Kelvin’s heat pump (1852) Kelvin's heat pump (1852) Perkins’s cycle on a modern refrigerant (1834) Perkins's cycle on a modern refrigerant (1834)