Exergy analysis of vapour compression refrigeration cycles for assessing thermal energy storage
Storage of thermal energy is very important in many engineering applications.For example,in wind energy storage systems,there is the need for an effective means by which the excess energy collected during the periods of high electricity production,can be stored for utilization during the period of low energy production.Aqueous salt solutions offer a simple and economical method for storing the excess thermal energy during economically most favourable supply of energy.This type viz.,solid-liquid phase change materials are useful because they store relatively large quantity of energy over a narrow temperature range.This work reports a thermodynamic study of exergy storage using aqueous sodium chloride solutions.The exergetic efficiency of the process was studied.Vapour compression refrigeration cycles are investigated as model processes.A number of refrigerants were investigated to test their suitability for the process.Besides the efficiency other parameters important from the economical point of view such as the storage volumes were also studied.In the model process a definite amount of exergy in the form of the compressor power will be supplied to the system comprising of vapour compression refrigerator to store possibly a large part of this exergy by freezing an aqueous salt solution.This power may be,for example the surplus power from a wind mill.For this purpose a number of refrigerants viz.,R1234yf,R134a,R152a,R236ea,R236fa,R245ca,R245fa,butane,isobutane,isobutene,propane,propene,dimethyl ether and ammonia were tested under different working conditions.It was found that at a condenser pressure of 1.8 MPa the working medium ammonia provides the most efficient process.The other interesting fluids are propene and propane.The common point among these fluids is the similarity of the boiling point and the dew point curves.Both belong to the category of wet fluids.
Exergy storage Vapour compression refrigeration cycle Cold latent heat Thermodynamic efficiency
M.Aslam Siddiqi Chris Tokple Roland Vilsmeier Burak Atakan
Thermodynamics,IVG,Faculty of Engineering,University of Duisburg Essen,Lotharstr.1,47048 Duisburg,Ge numrax GmbH,Schemkesweg 16,47057 Duisburg,Germany
国际会议
桂林
英文
1-14
2013-07-16（万方平台首次上网日期，不代表论文的发表时间）