Patent GB-822056-A (GB)
Title: Improvements in or relating to absorption refrigerating apparatus
IPC: F25B47/02
Filed: 1956-10-25
Abstract: 822,056. Refrigerating. ELECTROLUX Ltd. Oct. 25, 1956 [Oct. 26, 1955], No. 32558/56. Class 29 In a continuous cycle inert gas absorption refrigerating apparatus, defrosting of the evaporator is effected by by-passing the condenser of the apparatus with a conduit adapted to convey hot vapour from the gas expeller to the evaporator and formed with a liquid trap, arranging the conduit so that vapour from the expeller condenses in the conduit and after a predetermined rise in level above the base of the trap the condensate forms a liquid seal preventing vapour flow to the evaporator and automatically removing the liquid from the conduit when the liquid in the trap has reached a predetermined level, the liquid being removed from the trap to a level below the liquid seal. Apparatus (Fig. 1) including a gas expeller 24, coondenser 30, evaporator 10 and absorber 18 has a liquid trap 44 formed by the pipe 41 communicating with vapour pipe 27 and one arm 46 of an inverted U-tube 48 the other arm 47 of which is connected to the vapour pipe 27 below the pipe 41. A vapour bypass tube 42 is connected between the evaporator 10 and the pipe 41 which it enters at a point higher than the end of arm 46. The C-shaped evaporator 10 has the upper limb 10a situated in a freezer compartment, while the lower limb 10b is in the food storage compartment, separate access being had to each compartment. The by-pass tube 42 is connected to the lower limb 10b of the evaporator. In operation hot gas vapour flows from the vapour pipe 27 directly to the evaporator defrosting. the lower limb 10b while allowing the upper limb to continue functioning. The wall temperature of the pipe 41 is lower than that of the vapour pipe 27 and condensate thus forms in pipe 41 and accumulates in the liquid trap eventually sealing the mouth of tube 42 and preventing further vapour passing to the evaporator. On the accumulation of condensate reaching the bend in the U-tube 48 it is removed by sphonic action through the arm 47 and is returned to the gas expeller 24. The end of the pipe 42 is then unsealed and defrosting can again take place. The pipe 41 can be formed so as to be in close heat exchange with the vapour pipe 27 or as a jacket about the pipe. The lower part is, however, kept clear of the vapour pipe to prevent boiling and the formation of vapour bubbles in the condensate. The condensate, on removal from the liquid trap may be led to the absorber. In an embodiment (Fig. 4) vapour leaving the gas expeller 24c is led through a pipe 53 to a stand pipe 52 acting as an analyzer and fed from the liquid heat exchanger through pipe 51. ' The liquid trap is connected to the expeller vessel and is formed by the tube 41c and the arm 46c of the inverted U-tube 48c, the other arm being connected to the pipe 53. Tube 42c carries hot vapour to the evaporator during defrosting periods. In this embodiment the evaporator part 10a does not function during . defrosting since all the hot vapour passes through the open connections and tube 42c to part 10b, the liquid in stand pipe 52 offering resistance to flow to the condenser. In a further embodiment (Fig. 6) the liquid trap is formed by the arms 46e, 41g of inverted U-tubes of which the other arms 47e and 41f are connected to the absorber and the vapour tube 27 respectively. On shut down of the refrigerating system inert gas is trapped in the tube 41f by condensate in the liquid trap. On restarting the system vapour must diffuse through the inert gas before reaching the liquid trap and while this is happening the tube 41g in close heat exchange with vapour pipe 27 is being heated by the hot vapour passing through the vapour pipe. This arrangement reduces condensation in the liquid trap due to the slow warming-up of the walls of the trap after a shut down.