Study of Solar-Assisted Ejector Cooling/Heating System
Date Issued
2010
Date
2010
Author(s)
Wu, Jia-Hong
Abstract
The conventional heat power cooling system uses auxiliary heater to provide steady cooling effect, while thermal energy is unstable. It is very unsuitable to consume a lot of energy; therefore, solar-assisted ejector cooling/heating system (SACH-1) was developed in this study for improving the defects of conventional heat power cooling system.
SACH combines solar heating system and ejector cooling system with thermal pumping together which provides steady cooling energy with the heat pump system. While using solar energy, the ejector cooling system can reduce the condensing temperature of heat pump and also increase its COP for decreasing the compressor power input.
This study first performs design of the system and analysis of economical benefit and takes an office with an overall size, 4 m × 4 m for a project research. Its cooling load is 3.5kW (1 RT) with a cooling period, 10 hours (8 o’clock am. to 6 o’clock pm.), so an overall cooling load in a day is 35kW (10 RT). First, in SACH-1, if COP of ejector cooling system can increase from 0.4 to 0.6, for reducing 50% power consumption of heat pump system, the required area of solar heating system can reduce from 58 m2 to 40 m2 (reducing 31%) in Taipei region and the required area of solar heating system can reduce from 46 m2 to 31 m2 (reducing 33%) in Tainan region. That is to say, increasing of COP in ejector cooling system can reduce the cost of solar heating system. In SACH-2 with COP=0.2 of ejector cooling system, to reduce 50% power consumption of heat pump system, the required area of solar heating system is 40 m2 in Taipei region and the required area of solar heating system is 31 m2 in Tainan region. Secondly, to generate hot water with a difference temperature, 40oC on SACH system in winter days, the required area of solar heating system is 36 m2 in Taipei region and the required area of solar heating system is 30 m2 in Tainan region. The amount of hot water supply in April is 1000 liter and in January is 500 liter which enough provides the usage of 20 to 40 people. Finally, in SACH-1 and SACH-2, if cooling capacities of ejector cooling system are more than 4RT and 3RT respectively, the period of cost recovery is less than 3 years. This conclusion is a very important reference for commercial products in future development.
This study improves Wang’s [55] system, redesigns ejector cooling system with thermal pumping, and tests the performance with thermal energy assisted using automatic control. The ejector cooling has an optimum filling capacity of refrigeration is 21.24 kg. With the following operating conditions, out-door temperature at 35oC, in-door temperature at 25oC, and heat loading at 3.52kW, the power consumption reduces to 45%. Compared with Wang’s [55] TACH, replacing an intercooler with a bigger heat-exchange area promotes energy-saving to 1.57%. Combining with solar heating system and designing a central control system for continuous operation, the result shows that by driving from solar energy, the condensing temperature of heat pump system can reduce, which saves power consumption to 56%.
Utilizing SACH-1 (series configuration), even if environment with high temperature causes condensing temperature rising, evaporating temperature of ejector cooling system can increase at the same time, which maintains the performance of ejector. When using different types to cool down condenser in ejector cooling system, the limit of increasing evaporating temperatures in ejector cooling system are inferred by experimental data in a simulation of high-temperature environment. According to reversed Rankine cycle, supposed COP of ejector cooling system at 0.4 and high-temperature environment at 45oC to 50oC, SACH can save energy more than 15% whether using water-cooling or air-cooling.
The summary of this study is the SACH improving the defects of conventional heat power cooling system, solving the problem of automatic-operating via weather variations, successfully combining with solar energy. It produces a marked effect on commerce and application.
Subjects
Solar energy
Solar cooling
Ejector cooling system
Ejector
Solar ejector cooling
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-99-D93522031-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):9d93b113400044fc6cfa019c32cc6d40