价值方程推导及其在节能评价中的应用

Derivation of Exergy Value Equations and Its Application in Energy Conservation Evaluation

热价值理论主要用于评价能量的有效利用程度.在该理论的基础上,结合热力学第二定律,推导出了依附于冷体、热体的价值方程.以加热炉钢坯热装和空(煤)气预热的算例为例,计算了两种情况下依附于钢坯和炉气的热价值和价值.结果表明,价值和热价值均随钢坯热装温度、空(煤)气预热温度的提高而提高;依附于炉气的价值在炉内传热良好且烟气入炉温度达到1 700 K甚至更高时高于其热价值,说明此条件下量得到了比热量更好的利用程度.

Thermal value theory is mainly used to evaluate the effective utilization aegree oi energy, based on which the exergy value equations depending on the cold and the hot objects were derived by combining second law of thermodynamics. Taking the charging of hot steel blank and the preheating of air （coal gas） in heating furnace as examples, the thermal values and exergy values depending on temperatures of steel blank and furnace gas were calculated. The results showed that the thermal values and exergy values both increase with the hot charging temperature of steel blank and the preheating temperature of air （coal gas）, and the exergy values depending on gas temperature even exceed its thermal values when heat transfer process is going on well and gas inlet temperature reaches or exceeds 1 700 K, this means exergy gets better utilization than heat.