Patent GB-872874-A (GB)
Title: Improvements in or relating to heat pumps
IPC: F25B30/04
Filed: 1957-10-29
Abstract: 872,874. Heat pumps. JOHANSSON, H. J. E., and NORBACK, P. J. G: Oct. 29, 1957, No. 33696/57. Class 29 [Also in Group XXVI] The invention relates to a heat pump based on a continuous cycle absorption refrigeration circuit in which useful heat is abstracted from the absorber and use is made of heat absorbing and heat delivering sources. means being provided to maintain the efficiency of the heat pump regardless of variations in temperature 'of the sources. A mixture of refrigerant (ammonia) and pressure reducing agent (water) is heated, by a heat delivery source, in a first evaporator 10, the refrigerant vapour being led through line 12 containing an analyser to a condenser 14 where it is condensed at the pressure prevailing in evaporator 10 by the heat absorbing source. Liquid refrigerant is then pumped to a second evaporator 16 where it is again heated by the heat delivery sources. Since the pressure reducing agent is not present in the second evaporator 16 the pressure of the refrigerant vapour at the same temperature as in the first evaporator is higher. The evaporated refrigerant at the higher pressure is then led to the absorber 32 to which weak liquor from the first evaporator is pumped, and the reassociation of the refrigerant and pressure reducing agent causes temperature higher than that of the heat delivery sources to be reached in the absorber. A liquid refrigerant receiver 56 is located between the condenser 14 and--evaporator 16 so that a constant amount of refrigerant is supplied to the second evaporator regardless of conditions prevailing at the condenser and first evaporator. By this means the strength of the mixture of refrigerant and pressure reducing agent is maintained constant at the absorber and heat output is steady. Instead of using a pump 20, the liquid refrigerant may be circulated from the condenser to the evaporator 16 by heating a container placed in the line 18, one-way valves causing the resulting vapour and entrained liquid to flow to the evaporator. An inert gas e.g. nitrogen may be utilized in the arrangement shown in Fig. 3. The nitrogen occupies the space above the liquid in the condenser 14 and first evaporator 10 and is displaced from the condenser by refrigerant vapour flowing through line 58 and gas heat exchanger 62. Vessels 72, 74 communicate with the gas spaces of the condenser and evaporator 16 and contain oil or other liquid immiscible with refrigerant. The height H 3  of oil varies to equalize pressures in the condenser 14 and evaporator 16. Vapour from evaporator 16 flows to absorber 32 through line 31 against the pressure of liquid column H 1 . When the system is fully operating the line 85 operates as a syphon or bubble pump carrying rioh liquor back to the evaporator 10. To assist this action the roof of absorber 32 slopes towards pipe 85. Two heat pumps may be used in cascade, the heat generated at the absorber of the first being applied to the evaporators of the second. Alternatively liquid refrigerant may be pumped from the condenser to a chamber in the absorber where it is heated and then passed to a second absorber where it is reassociated with liquid already partially enriched by passage through the first absorber. Since the reassociation takes place at the pressure of the liquid vaporized in the first absorber the temperature of the second absorber is correspondingly higher. The heat of the absorber may also be used to generate power (see Group XXVI).