A refrigerator provides a diffusion-absorption refrigeration assembly that uses helium as a diffusion gas. The refrigeration assembly includes a condenser, an evaporator, a liquid ammonia tube, and a gas heat exchanger. The liquid ammonia tube includes a first vertical section with an inlet and a second vertical section downstream of the first. The second vertical section of the liquid ammonia tube being noncontiguous with said heat exchanger, wherein no heat is exchanged between flowable fluids flowing in said second vertical section and in said heat exchanger. The heat exchanger includes inner and outer tubes. The inner tube has an outer surface, and the outer tube has an inner surface. The outer and inner surfaces each has serrations to produce an increase in surface area of the corresponding surface. The refrigerator has a freezer box defining a first cubic area and a refrigerator box defining a second cubic area. The sum of the first and second cubic areas is equal to or greater than six cubic feet. The assembly is capable of cooling the refrigerator box to a temperature of 6°C (43 °F) and the freezer compartment to a temperature of -9°C (15°F) when the ambient is at a temperature of 43 °C ( 1 10°F).
