Performance improvement of ammonia/absorbent air source absorption heat pump in cold regions

Abstract

Air source absorption heat pump is promising in energy saving and emission reduction of heating and domestic hot water, but performs badly or even cannot work in cold climate. The ammonia/absorbent air source absorption heat pump with low-pressure boosting is proposed to solve the problem. The hybrid air source absorption heat pump + compressor system is modeled and the compression ratio is optimized to obtain maximum primary energy efficiency. The integrated system is simulated with air temperature ranging from −30℃ to 10℃ and hot water temperature from 30℃ to 60℃. Comparative simulations on three working fluids reveal that NH3–LiNO3 system has the lowest compression ratio and the highest primary energy efficiency value. By pressure boosting, the air source absorption heat pump can operate under air temperatures as low as −30℃. Primary energy efficiency of the hybrid system is about 15–50% higher than that of coal boiler, showing great potential for heat supply in cold regions. Practical application: Heating and domestic hot water consumes a large amount of energy every year. Air source absorption heat pump can be a potential alternative to the traditional boiler systems in the point view of primary energy efficiency. However, air source absorption heat pump performs badly or cannot work when the air temperature is low. This paper presents a hybrid air source absorption heat pump with pressure boosting to improve the performance of the air source absorption heat pump heating system, making it operate under lower outdoor air temperatures with higher primary energy efficiency. The novel heat supply system is expected to make contributions to building energy saving as well as pollution reduction.

Thermodynamic Investigation and Comparison of Absorption Cycles Using Hydrofluoroolefins and Ionic Liquid

“…Too small a concentration difference will worsen the performance or even make it unable to operate. To solve this problem, the compression-assisted absorption cycle 25 can be used, as demonstrated in Figure 2. A compressor is configurated between the evaporator and absorber to boost the absorption pressure from p e (10) to p a (11).…”

Numerical study of a hybrid absorption-compression high temperature heat pump for industrial waste heat recovery

“…where h2s is the enthalpy of ammonia-water liquid at the outlet of pump if the process is isentropic. The pump1 has been pre-defined at 0.85 according to the literature [18]. h2s can be calculated by considering the ammonia-water liquid at pressure PH with an entropy value of s1, then the value of h2 can be calculated by Eq.…”

“…where com has been pre-defined at 0.75 [18], the mass flow rate of ammonia-water vapor entering the compressor can be calculated based on the value of splitting ratio, ref =̇8…”

Efficiency of use of waste heat energy on the example of Chelyabinsk

“…Then, the assumption was made according to which the average monthly values of heat capacity necessary for meeting production needs and supplying hot water are constant over the year, whereas the average monthly values of heating needs vary according to the 150/70 regulation schedule [12], i.e. dependent on outdoor temperature.…”