As the first artificial refrigeration method developed

absorption refrigeration has been around for more than 200 years. In truth

it has been used in civil and industrial applications for more than 60 years. Absorption refrigeration has developed rapidly in terms of theory and application over the past 20 years

and in the refrigerator market occupies a considerable share

has drawn significant attention from both domestic and foreign manufacturers. With an increase in human energy consumption

in-depth research on new and distributed energy sources and their efficient utilization needs to be carried out. The use of waste heat

renewable solar energy

and geothermal energy make heat-driven refrigeration (heat pumps) an increasingly attractive option.Unlike electric-driven vapor compression refrigeration (heat pump) systems

absorption refrigeration (heat pump) technology can be driven directly using thermal energy from low-grade heat sources

operating at a much lower cost than the electric-driven system. Owing to their environmentally friendly features

including safety

noise-free operation

high reliability

and other significant advantages

absorption systems have adopted a water-lithium bromide solution

an ammonia-ammonia solution

or other natural refrigerant as the working fluid. However

absorption systems have a large footprint

a large initial investment

high cooling load

low energy efficiency (direct combustion form)

and other deficiencies. In view of these characteristics

the main research directions at this stage include an optimization of the cycle design

the selection of a working fluid

enhancement of the heat and mass transfer of the system components

and optimization of the system control strategy.The absorption cycle

in a narrow sense

refers to a closed

vapor refrigerant absorbed by the solution refrigeration (heat pumps) cycle. This family of cycle

in accordance with its classification of cycle configuration

includes single absorption cycles

multi-absorption cycles

and combined cycles. Single absorption cycles consist of a basic single-effect absorption cycle

diffusion absorption cycles

membrane absorption cycles

heat booster cycles

gravity-driven valve-operation cycles

and self-cascade cycles. A multiple absorption cycle mainly includes a reabsorption cycle

multi-effect cycles

intermediate-effect cycles

multi-stage cycles

intermediate-stage cycles

and GAX cycles. Combined cycles mainly consist of ejection-absorption cycles

compression-absorption cycles

and expansion-absorption cycles.Existing research into absorption refrigeration technologies includes

but is not limited to

solar energy

medium and low temperature level waste heat utilization

combined heat and power

energy storage (cooling and heat storage)

membrane exchange materials

high-temperature corrosion-resistant materials

plastic heat exchangers and so on. The existing absorption cycle was designed to satisfy a certain temperature and concentration range. In the face of new applications

new materials and a new absorption of working fluids

novel absorption cycles can be proposed with greater efficiency

wider ranges of heat-source driven temperature and solution concentration.