Study of Performance Improvement on Solar-Assisted Ejector Cooling/Heating System
Date Issued
2010
Date
2010
Author(s)
Yen, Chao-Wen
Abstract
The conventional heat power cooling systems like ejector system, adsorption system and absorption system use auxiliary heater to provide steady cooling effect, while the thermal energy is unstable. It is very unsuitable to consume a lot of cost; therefore, solar-assisted ejector cooling/heating system (SACH) was developed in this study for improving the defects of conventional heat power cooling system.
SACH combines solar heating system, ejector cooling system and inverter-type air conditioner. SACH-2 connects ejector cooling system and inverter-type air conditioner in parallel, which saves electricity by assist of solar ejector cooling system. SACH-1 connects pump-less ejector cooling system and inverter-type air conditioner in series, which uses pump-less ejector cooling system to lower condensing temperature of inverter-type air conditioner and improve inverter-type air conditioner operating performance.
On SACH-2, expansion valve feedback system in ejector cooling system is developed. Electronic expansion valve which adjusts opening of expansion valve to control evaporating temperature by feedback control is set up in suction side of ejector (evaporator inlet). Even with unstable heat, ejector can operate in double-chocking critical mode and none double-chocking critical mode to have an optimum performance. When a backflow is about to happen in the ejector, the feedback control system will turn off the expansion valve, avoiding transforming evaporator from cooling to heating, which increasing cooling load. Performance result shows that the ejector cooling system driving by solar energy works normally even with a variation on irradiation, while the maximum power saving is 63%. On long-term performance, SACH-2 has operated continuously over 8 months and has 30%-80% at power saving and also 51% at total power saving, compared with operating inverter-type air conditioner alone.
On SACH-1, new type of mixing refrigerant is built in pump-less ejector cooling system. The mixing refrigerant has a latent heat at 410.69kJ/kg twice as much as R365mfc while the temperature is at 10 degree Celsius; therefore, the mixing refrigerant has a double cooling capacity with the same suction flow. The mixing refrigerant has a lower density means reducing 25% filling capacity and 47% cost. The constant cross-section diffusion part is designed in double-conical, and the ratio of area is 8.45. SACH-1 has a power saving at 41.8% operated by electric heating and a power saving at 57.8% operated by solar energy.
In conclusion, solar-assisted ejector cooling/heating system improves the disadvantage of conventional thermal-energy assisted cooling system, solves the problem of automatic control with a solar-energy variation, and for the first time mixing refrigerant is successful connected with solar energy to save power. It makes a eminent contribution in commerce and on application.
Subjects
solar energy
ejector system
ejector cooling
solar cooling
Type
thesis
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