The calcium bromide solution absorption refrigeration system is a refrigeration technology driven by thermal energy. Its core lies in completing the heat absorption and heat release cycle through the “working pair” composed of calcium bromide solution (absorbent) and water (refrigerant). The detailed working principle is as follows:
Core Components
The system mainly consists of 5 key components, and each part collaborates to complete the refrigeration cycle:
- Generator: Heats the calcium bromide solution to evaporate and separate the water from it.
- Condenser: Condenses the separated water vapor into liquid water.
- Throttle valve (expansion valve): Reduces the pressure and temperature of liquid water, preparing it for evaporation.
- Evaporator: Liquid water evaporates and absorbs heat, generating a refrigeration effect.
- Absorber: The calcium bromide solution reabsorbs the water vapor generated in the evaporator to complete the cycle.
Workflow (Cyclic Process)
The entire system operates cyclically through four stages: “absorption – generation – condensation – evaporation”. The details are as follows:
- Generator: Heating to separate the refrigerant
A calcium bromide solution with a relatively high concentration (called a “strong solution” due to its strong water absorption capacity) is introduced into the generator and heated by an external heat source (such as industrial waste heat, solar energy, or heat from gas combustion).- When the calcium bromide solution is heated, the water dissolved in it evaporates into water vapor and separates from the solution.
- The remaining solution, with reduced moisture content, has a further increased concentration (called a “weak solution”; here, “weak” is relative to the strong solution before heating, and the actual concentration is still high) and then flows back to the absorber.
- Condenser: Condensing water vapor into liquid
The water vapor separated in the generator enters the condenser and is cooled by a cooling medium (such as cooling water) to condense into high-pressure liquid water (refrigerant).- During this process, latent heat of condensation is released and carried away by the cooling medium.
- Throttle valve: Reducing pressure and temperature
After passing through the throttle valve (expansion valve), the high-pressure liquid water experiences a sudden drop in pressure and a significant decrease in temperature, forming low-pressure, low-temperature liquid water or a gas-liquid mixture, which then enters the evaporator. - Evaporator: Evaporation absorbs heat to produce refrigeration
The low-pressure, low-temperature liquid water in the evaporator exchanges heat with the object to be cooled (such as air in an air conditioning system or industrial process fluids).- Water evaporates rapidly in a low-pressure environment, absorbing a large amount of heat (latent heat of evaporation), which lowers the temperature of the object to be cooled, achieving the refrigeration effect.
- The water vapor (low-pressure) generated after evaporation enters the absorber.
- Absorber: Calcium bromide solution reabsorbs water
The strong calcium bromide solution (with high concentration due to the loss of some moisture) flowing back from the generator enters the absorber and comes into contact with the water vapor generated in the evaporator.- Calcium bromide has strong hygroscopicity and will quickly absorb the water vapor, making the water vapor redissolve into the solution to form a calcium bromide solution with a relatively low concentration (called a “weak solution”).
- The absorption process releases heat (absorption heat), which needs to be carried away by a cooling medium (such as cooling water) to maintain absorption efficiency.
- The weak solution is then pumped back to the generator to be heated again for water separation, completing the entire cycle.
Summary of Key Principles
The core role of the calcium bromide solution is to “absorb and release” the refrigerant (water):
- In the absorber, the high-concentration calcium bromide solution absorbs water vapor, maintaining a low-pressure environment in the evaporator to ensure that water can continuously evaporate and absorb heat.
- In the generator, heating causes the solution to release water vapor, restoring its high concentration for recycling.
The entire system does not require a mechanical compressor (unlike traditional compression refrigeration) and is driven by thermal energy. It is particularly suitable for scenarios with low-grade waste heat or renewable energy (such as solar energy), enabling efficient cascaded utilization of energy.
