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Exergy Analysis of Several Heating and Air Conditioning Ways

Author: LiangMingShan
Tutor: FuYongZheng
School: Wuhan University of Science and Technology
Course: Environmental Engineering
Keywords: Heating and Air conditioning large temperature difference energy-efficiency analysis PER exergy-efficiency exergy consumption
CLC: TU831
Type: Master's thesis
Year: 2011
Downloads: 241
Quote: 1
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Abstract

Energy analysis methods on the heating and cooling systems commonly there are two ways: energy analysis and exergy analysis. The characteristics of the energy analysis is the balance of different qualitative energy in the amount,it only considers the utilization degree of energy“amount”,reflects the external loss of“amount”.But the characteristics of the exergy analysis is the balance of same qualitative energy in the amount,it considers both the energy“quality”devaluation and the energy“amount”losses,reflects the exergy consumption of the system inside and outside.The traditional energy analysis specify a direction on energy saving, such as through recycling waste heat, reduce leak, strengthen preservation etc. measures to reduce the energy external losses. But the energy analysis can’t reveal energy“quality”devaluation and losses,it can’t reveal the nature of energy consumption.So it’s necessary for a certain energy analysis,but as the developing of energy conservation in depth,in order to indicate the accurate direction and way on energy saving,we need for the exergy analysis based on the energy analysis.This paper reveals reasons on the exergy analysis is scientific than the energy analysis through the comparison between them.And the paper shows the huge energy-saving benefits by using the low-exergy energy in the heating and cooling systems.And for several common low-exergy technology,puts forward the respective superiority and constraints.For the electrical energy heating forms in Wuhan,the energy-efficiency was calculated and analyzed in this paper.The results show that, both the PER and the exergy-efficiency of the electric heater and the electrode boiler are just 1/3 by the heat pump unit ,although the PER of the heat pump unit is higher,and the exergy-efficiency is 3 times than the electric heater and the electrode boiler,but its exergy-efficiency is still very low,almost at 20%.This is due to consuming the high quality electrical energy,but obtain the low quality thermal energy ,there is huge energy qualitative gap between them.Taking an air conditioning project as an example, this paper analyzes the influence on energy consumption of each part of the system by increasing the temperature difference.And puts forward the method of exergy balance,calculates the exergy efficiency and exergy consumption of the standard temperature difference (outlet and inlet chilled water temperature are 7/12℃,outlet and inlet cooling water temperature are 37/32℃) and the large temperature difference (①outlet and inlet chilled water temperature are 5/13℃,outlet and inlet cooling water temperature are 37/32℃;②outlet and inlet chilled water temperature are 7/15℃,outlet and inlet cooling water temperature are 37/32℃;③outlet and inlet chilled water temperature are 5/13℃,outlet and inlet cooling water temperature are 40/32℃), The results show that,compared with the standard temperature difference,the large temperature difference program①:the exergy consumption increased by 5%,the exergy efficiency reduced by 4.2%; the large temperature difference program②:the exergy consumption reduced by 7.4%,the exergy efficiency increased by 7.0%; the large temperature difference program③:the exergy consumption reduced by 3.5%,the exergy efficiency increased by 3.2%;

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